CN113113840B

CN113113840B - Control method of double-feedback PWM constant-current drive circuit

Info

Publication number: CN113113840B
Application number: CN202110416292.7A
Authority: CN
Inventors: 胡肖松; 骈冰; 戢冰; 张武杰
Original assignee: Casi Vision Technology Luoyang Co Ltd; Casi Vision Technology Beijing Co Ltd
Current assignee: Casi Vision Technology Luoyang Co Ltd; Casi Vision Technology Beijing Co Ltd
Priority date: 2021-01-27
Filing date: 2021-01-27
Publication date: 2022-04-29
Anticipated expiration: 2041-01-27
Also published as: CN112436719A; CN113113840A; CN112436719B

Abstract

The application discloses a control method of a double-feedback PWM constant-current drive circuit, which comprises the following steps: a voltage feedback step and a current feedback step; the voltage feedback step further includes: the voltage signal VD passes through the voltage conversion circuit (6) to output a voltage signal VF, passes through the voltage feedback control circuit (5) to output a feedback voltage signal FB, and the feedback voltage signal FB controls the process that the switching power supply circuit (1) outputs the voltage signal VO; the current feedback step further includes: the sampling resistor R7 in the current feedback driving circuit (3) samples the current flowing through the sampling resistor R7, and then the process of outputting the current is controlled by the voltage signal VI through the current series negative feedback circuit or the current parallel negative feedback circuit. The invention realizes high-precision and high-stability constant current or PWM constant current output when the high-power laser is driven, can adaptively adjust the output voltage of the adjustable switching power supply according to the working voltage of the laser and the voltage drop of the power tube in the current feedback circuit, and improves the working efficiency of the system.

Description

Control method of double-feedback PWM constant-current drive circuit

Technical Field

The invention relates to the technical field of laser circuits, in particular to a constant-current laser driving circuit with voltage and current double feedback and PWM control and a control method.

Background

Semiconductor lasers, also known as Laser Diodes (LDs), are currently widely used in Laser ranging, Laser marking, Laser radar, Laser communication, Laser analog weapons, optoelectronic information processing, medical and military applications, and detection instruments.

The semiconductor laser works by means of direct injection of carriers, and the stability of injected current has direct and obvious influence on the output of the laser, so that the driving technology of the semiconductor laser usually adopts a constant current driving mode and generally requires high stability of output current, small surge impact current and small ripple.

With the development of laser technology, the output function of a laser driving circuit is required to have not only constant current but also arbitrarily adjustable Pulse width and frequency, i.e., the output current is required to have a Pulse Width Modulation (PWM) function.

For the conventional laser constant current driving circuit, a plurality of mature solutions are available on the market at present. However, these driving circuits are generally only suitable for lasers with specific PVI (power-voltage-current), and the circuit is usually changed or redesigned after the laser with different parameters is replaced, otherwise the system efficiency is low.

For a specific laser, due to the difference of VI characteristics of the laser, the efficiency of the system is often different under different operating currents, and it is not possible to ensure that the system operates at a higher efficiency under both low current and high current driving. Furthermore, in high power constant current or pulsed current applications, such as laser marking, laser ranging, laser targeting, laser etching, single pulse lasers are required to have higher pulse accuracy and energy.

Thus, high power LD lasers are required to have currents as high as 40A or more and pulse width and strobe PWM adjustments based on feedback parameters, and existing solutions have not been adequate for these system applications.

Disclosure of Invention

The invention aims to solve the technical problem of providing a voltage and current double-feedback and PWM controlled laser constant current driving circuit, which comprises a current feedback control loop and a voltage feedback control loop, realizes the high-precision and high-stability PWM constant current driving output function of the light intensity of a high-power laser, and can adaptively adjust the output voltage of an adjustable switching power supply according to different types of lasers or different working voltages of the lasers. The laser driving circuit has two modes of constant current or PWM constant current, and the output current value can be flexibly set; the output voltage of the system can be changed in a self-adaptive manner according to the working voltage of the laser, so that the system works in the highest efficiency state; the light intensity of the laser does not change with the change of the pulse width or the frequency; the output is constant or the pulse light intensity, and the device has the characteristics of high precision and good stability.

In order to solve the above technical problem, the present invention provides a PWM constant current dual feedback laser driving circuit, including: the device comprises a switching power supply circuit 1, a PWM control circuit 2, a current feedback drive circuit 3, a laser circuit 4, a voltage feedback control circuit 5 and a voltage conversion circuit 6;

the switching power supply circuit 1 is respectively connected with the voltage feedback control circuit 5, the laser circuit 4 and the voltage conversion circuit 6; the feedback circuit is used for receiving a feedback voltage signal FB output by the voltage feedback control circuit 5; and outputs a voltage signal VO to the voltage feedback control circuit 5, the laser circuit 4, and the voltage conversion circuit 6;

the PWM control circuit 2 is connected to the current feedback driving circuit 3 and the voltage converting circuit 6, respectively; the voltage signal VI is connected to the current feedback driving circuit 3, and the voltage signal PW is connected to the voltage conversion circuit 6.

Preferably, the current feedback driving circuit 3 is respectively connected to the PWM control circuit 2, the laser circuit 4, and the voltage conversion circuit 6; the sampling resistor R7 samples the current signal ID flowing through the laser circuit, and then sets the current series negative feedback circuit or the current parallel negative feedback circuit in the current feedback driving circuit 3 through the voltage signal VI, so as to control the output current signal ID.

Preferably, the laser circuit 4 is respectively connected to the switching power supply circuit 1, the voltage feedback control circuit 5, the voltage conversion circuit 6, and the current feedback driving circuit 3; and the output end of the voltage conversion circuit 6 is connected with the current feedback driving circuit 3 and the voltage conversion circuit VO, and is used for receiving a voltage signal VO output by the switching power supply circuit 1 and outputting a voltage signal VD to the current feedback driving circuit 3.

Preferably, the voltage feedback control circuit 5 is respectively connected to the switching power supply circuit 1, the laser circuit 4, and the voltage conversion circuit 6; the voltage signal VO output by the switching power supply circuit 1 and the voltage signal VF output by the voltage conversion circuit 6 output a feedback voltage signal FB through the voltage feedback control circuit 5.

Preferably, the voltage conversion circuit 6 is respectively connected to the switching power supply circuit 1, the PWM control circuit 2, the current feedback drive circuit 3, the laser circuit 4, and the voltage feedback control circuit 5; a voltage signal VO output by the switching power supply circuit 1 is used for controlling the voltage required by the circuit; a voltage signal VD output by the laser circuit 4 and a voltage signal VS output by the current feedback driving circuit output a voltage signal VF through the voltage conversion circuit 6; the voltage signal PW of the PWM control circuit 2 is connected to the voltage conversion circuit 6.

Preferably, the switching power supply circuit 1, the PWM control circuit 2, the current feedback drive circuit 3, the voltage feedback control circuit 5, and the voltage conversion circuit 6 are connected to a ground line.

Preferably, the current signal ID is a signal that needs to be converted and processed to flow through the laser circuit 4; the voltage signal VD output by the laser circuit 4 and the voltage signal VS output by the current feedback driving circuit are the voltages of the drain electrode and the source electrode of the power MOS tube in the current feedback driving circuit 3; the voltage signal PW output by the PWM control circuit 2 is a conversion control signal; the voltage signal VF output by the voltage conversion circuit 6 is provided to the voltage feedback control circuit 5; the voltage signal VO output by the switching power supply circuit 1 is an output voltage signal that is adaptively adjusted and is used for providing electric energy for the laser circuit 4.

Preferably, the voltage feedback control circuit 5 is further configured to: and after the voltage signal VO output by the switching power supply circuit 1 and the voltage signal VF output by the voltage conversion circuit 6 are redundantly connected in parallel, providing an output feedback voltage signal FB to the switching power supply circuit 1.

Preferably, in the voltage conversion circuit 6, the voltage signal VD and the voltage signal VS pass through the switch M2 and the switch M3, respectively, and then pass through a proportional operation and integration circuit formed by the operational amplifier U3, and then output the voltage signal VF to the voltage feedback control circuit 5.

Preferably, the PWM control circuit 2 controls the DA conversion circuit 1 to output the voltage signal VI1 through the MCU processor, and controls the DA conversion circuit 2 to output the voltage signal VI2 through the MCU processor; and respectively providing the voltage signal VI1 and the voltage signal VI2 to the input terminal of an analog switch U1; the MCU processor outputs a voltage signal PWM1 and a voltage signal PWM 2; the voltage signal PWM1 provides a voltage signal PW to the voltage converting circuit 6 through a current limiting resistor R2; the voltage signal PWM2 controls the analog switch U1 through the current limiting resistor R1, and selects the voltage signal VI1 or the voltage signal VI2 to output the voltage signal VI.

In order to solve the above technical problem, the present invention further provides a dual-feedback PWM constant current driving circuit, including: the device comprises a switching power supply circuit 1, a PWM control circuit 2, a current feedback drive circuit 3, a light source circuit 7, a voltage feedback control circuit 5 and a voltage conversion circuit 6;

the switching power supply circuit 1 is respectively connected with the voltage feedback control circuit 5, the light source circuit 7 and the voltage conversion circuit 6; the feedback circuit is used for receiving a feedback voltage signal FB output by the voltage feedback control circuit 5; and outputs a voltage signal VO to the voltage feedback control circuit 5, the light source circuit 7, and the voltage conversion circuit 6;

Preferably, the current feedback driving circuit 3 is respectively connected to the PWM control circuit 2, the light source circuit 7, and the voltage conversion circuit 6; the sampling resistor R7 samples the current flowing through the resistor, and then the output current control is realized by the voltage signal VI through the current series negative feedback circuit or the current parallel negative feedback circuit provided in the current feedback driving circuit 3.

Preferably, the light source circuit 7 is respectively connected to the switching power supply circuit 1, the voltage feedback control circuit 5, the voltage conversion circuit 6, and the current feedback driving circuit 3; and is configured to receive the voltage signal VO input by the voltage conversion circuit 6, and output a voltage signal VD to the current feedback driving circuit 3 and the voltage conversion circuit 6.

Preferably, the voltage feedback control circuit 5 is respectively connected to the switching power supply circuit 1, the light source circuit 7, and the voltage conversion circuit 6; the voltage signal VD passes through the voltage conversion circuit 6 to output a voltage signal VF, and then passes through the voltage feedback control circuit 5 to output a feedback voltage signal FB.

Preferably, the voltage conversion circuit 6 is respectively connected to the switching power supply circuit 1, the PWM control circuit 2, the current feedback drive circuit 3, the light source circuit 7, and the voltage feedback control circuit 5; the voltage signal VD passes through the voltage conversion circuit 6 to output a voltage signal VF; the voltage signal VI of the PWM control circuit 2 is connected with the input of the current feedback drive circuit 3; the voltage signal PW is connected to an input of the voltage conversion circuit 6.

Preferably, one and/or more of the switching power supply circuit 1, the PWM control circuit 2, the current feedback drive circuit 3, the voltage feedback control circuit 5, and the voltage conversion circuit 6 are connected to ground.

Preferably, the voltage signal VD at the input end is a signal that needs to be converted and processed by the voltage conversion circuit 6; the input voltage signal VO provides electric energy for the voltage conversion circuit 6; an input voltage signal PW of the voltage conversion circuit 6 is a conversion control signal; the voltage conversion circuit 6 outputs a voltage signal VF to the voltage feedback control circuit 5.

Preferably, the voltage feedback control circuit 5 redundantly connects the voltage signal VO output by the switching power supply circuit 1 and the output voltage signal VF of the voltage conversion circuit 6 in parallel, and then outputs a feedback voltage signal FB to the switching power supply circuit 1, so as to adjust the output voltage range of the switching power supply circuit 1.

In order to solve the above technical problems, the present invention also provides a control method for a driving circuit of a PWM constant current dual feedback laser,

the PWM constant-current double-feedback laser driving circuit comprises: the device comprises a switching power supply circuit 1, a PWM control circuit 2, a current feedback drive circuit 3, a laser circuit 4, a voltage feedback control circuit 5 and a voltage conversion circuit 6;

the PWM control circuit 2 is connected to the current feedback driving circuit 3 and the voltage converting circuit 6, respectively; a voltage signal VI is connected with the current feedback driving circuit 3, and a voltage signal PW is connected with the voltage conversion circuit 6;

the current feedback driving circuit 3 is respectively connected with the PWM control circuit 2, the laser circuit 4, and the voltage conversion circuit 6;

the laser circuit 4 is respectively connected with the switching power supply circuit 1, the voltage feedback control circuit 5, the voltage conversion circuit 6 and the current feedback drive circuit 3; the voltage conversion circuit is used for receiving a voltage signal VO output by the switching power supply circuit 1 and outputting a voltage signal VD to the current feedback driving circuit 3 and the voltage conversion circuit 6;

the voltage feedback control circuit 5 is respectively connected with the switching power supply circuit 1, the laser circuit 4 and the voltage conversion circuit 6;

the voltage conversion circuit 6 is respectively connected with the switching power supply circuit 1, the PWM control circuit 2, the current feedback drive circuit 3, the laser circuit 4, and the voltage feedback control circuit 5;

the method comprises the following steps: a voltage feedback step and a current feedback step;

the voltage feedback step further includes: a voltage signal VO output by the switching power supply circuit (1) and a voltage signal VF output by the voltage conversion circuit 6 pass through the voltage feedback control circuit 5 to output a feedback voltage signal FB, and the feedback voltage signal FB controls the process of outputting the voltage signal VO by the switching power supply circuit 1;

the current feedback step further includes: the sampling resistor R7 in the current feedback driving circuit 3 samples the current signal ID flowing through the laser circuit 4, and then controls the process of outputting the current ID through the voltage signal VI via the current series negative feedback circuit or the current parallel negative feedback circuit in the current feedback driving circuit 3.

Preferably, the voltage signal VI of the PWM control circuit 2 is connected to the input of the current feedback driving circuit 3, and the voltage signal PW is connected to the input of the voltage converting circuit 6.

Preferably, the PWM control circuit 2 controls the DA conversion circuit 1 to output the voltage signal VI1 through the MCU processor, controls the DA conversion circuit 2 to output the voltage signal VI2 to be respectively provided to the input terminals of the analog switch U1, and the MCU processor outputs the voltage signal PWM1 and the voltage signal PWM2, the voltage signal PWM1 provides the voltage signal PW to the voltage conversion circuit 6 through the current limiting resistor R2, the voltage signal PWM2 controls the analog switch U1 through the current limiting resistor R1 to select the voltage signal VI1 and the voltage signal VI2 to output the voltage signal VI, and provides the voltage signal VI to the current feedback driving circuit 3.

Preferably, the DA converter circuit 2 of the PWM control circuit 2 is formed by serially dividing a voltage by a plurality of resistors, one end of the resistor R26 is connected to the reference voltage VCC, one end of the resistor R27 is connected to the signal ground, and the intermediate terminals of the plurality of resistors are connected to the voltage signal VI 2.

Preferably, the DA conversion circuit 2 of the PWM control circuit 2 is formed by serially dividing a voltage by a resistor R26 and a resistor R27.

Preferably, the current feedback driving circuit 3 adopts a circuit structure of a current series negative feedback topology as follows: the voltage signal VI is connected with a terminal 1 of a resistor R3, and a terminal 2 of a resistor R3 is connected with a non-inverting input end of the operational amplifier U2; the reverse input end of the operational amplifier U2 is connected with the anode of the diode D1, the terminal 1 of the capacitor C1 and the terminal 1 of the resistor R6; the diode D1 and the resistor R4 are connected in series to improve the dynamic characteristic of the operational amplifier U2, the cathode of the diode D1 is connected with the terminal 1 of the resistor R4, and the terminal 2 of the resistor R4 is connected with the output end of the operational amplifier U2.

Preferably, the current feedback driving circuit 3 adopts a circuit structure of a current parallel negative feedback topology: the voltage signal VI is connected with a terminal 1 of a resistor R3, and a terminal 2 of a resistor R3 is connected with an inverted input end of an operational amplifier U2, an anode of a diode D1, a terminal 1 of a capacitor C1 and a terminal 1 of a resistor R6; the resistors R22 and R23 divide the voltage to provide a reference voltage Vref for the non-inverting input end of the operational amplifier U2, the non-inverting input end of the operational amplifier U2 is connected with the terminal 1 of the resistor R22 and the terminal 1 of the resistor R23, the terminal 2 of the resistor R22 is connected with the reference voltage VCC1, and the resistor R23 is connected with the signal ground.

Preferably, the voltage feedback control circuit 5 inputs the voltage signal VO and the voltage signal VF, and outputs a feedback voltage signal FB; the voltage feedback control circuit 5 redundantly connects in parallel the voltage signal VO output by the switching power supply circuit 1 and the voltage signal VF output by the voltage conversion circuit 6, and outputs the feedback voltage signal FB to the switching power supply circuit 1, so as to adjust the output voltage of the switching power supply circuit.

Preferably, in the voltage feedback control circuit 5, the voltage signal VO is connected to the terminal 1 of the resistor R9, the terminal 2 of the resistor R9 is connected to the terminal 1 of the resistor R10 and the anode of the diode D3, the terminal 2 of the resistor R10 is connected to the signal ground, and the cathode of the diode D3 is connected to the feedback voltage signal FB; the voltage signal VF is connected with a terminal 1 of the resistor R11, a terminal 2 of the resistor R11 is connected with a terminal 1 of the resistor R12 and an anode of the diode D4, a terminal 2 of the resistor R12 is connected with the signal ground, and a cathode of the diode D4 is connected with the feedback voltage signal FB.

Preferably, the current ID flowing through the laser circuit is a signal that the current feedback driving circuit 6 needs to convert and process; a voltage signal VD at an input end and a voltage signal VS output by the current feedback driving circuit (3) are signals which need to be converted and processed by the voltage conversion circuit 6, the voltage signal VO provides electric energy for the voltage conversion circuit 6, and a voltage signal PW input by the voltage conversion circuit 6 is a conversion control signal; the voltage signal VF output by the voltage conversion circuit 6 is provided to the voltage feedback control circuit 5.

Preferably, after the output voltage VO of the switching power supply circuit 1 and the output voltage VF of the voltage conversion circuit 6 are redundantly connected in parallel, an output signal FB is provided to the switching power supply circuit 1 for adjusting the output voltage range of the switching power supply circuit 1.

Preferably, in the voltage conversion circuit 6, the voltage signal VD and the voltage signal VS are respectively switched by MOS transistors M2 and M3, and then output a voltage signal VF to the voltage feedback control circuit 5 after passing through a proportional operation and integration circuit formed by an operational amplifier U3; the MOS is used for controlling the turning-on and turning-off of M2 and M3; and is realized by signal adjustment for the PW signal passing through the PWM control circuit 2.

Preferably, the PWM control circuit 2 controls the DA circuit 1 to output the signal VI1 through the MCU processor, and controls the DA circuit 2 to output the signal VI2 through the MCU processor; and the two signals are respectively provided to the input terminals of the analog switch U1; the MCU processor outputs a PWM1 signal and a PWM2 signal; the PWM1 signal provides a signal PW to the voltage conversion circuit 6 through a current limiting resistor R2; the PWM2 signal controls the analog switch U1 through the current limiting resistor R1 and selects VI1 and/or VI2 to output to VI, providing a voltage signal to the current feedback driving circuit 3.

In order to solve the above technical problem, the present invention further provides a control method of a dual feedback PWM constant current driving circuit,

the double-feedback PWM constant-current driving circuit comprises: the device comprises a switching power supply circuit 1, a PWM control circuit 2, a current feedback drive circuit 3, a light source circuit 7, a voltage feedback control circuit 5 and a voltage conversion circuit 6;

the current feedback driving circuit 3 is respectively connected with the PWM control circuit 2, the light source circuit 7 and the voltage conversion circuit 6;

the light source circuit 7 is respectively connected with the switching power supply circuit 1, the voltage feedback control circuit 5, the voltage conversion circuit 6 and the current feedback drive circuit 3; the voltage conversion circuit is used for receiving a voltage signal VO input by the switching power supply circuit 1 and outputting a voltage signal VD to the current feedback driving circuit 3 and the voltage conversion circuit 6;

the voltage feedback control circuit 5 is respectively connected with the switching power supply circuit 1, the light source circuit 7 and the voltage conversion circuit 6;

the voltage conversion circuit 6 is respectively connected with the switching power supply circuit 1, the PWM control circuit 2, the current feedback drive circuit 3, the light source circuit 7 and the voltage feedback control circuit 5;

the current feedback step further includes: the sampling resistor R7 in the current feedback driving circuit 3 samples the current flowing through the sampling resistor R7, and then the process of outputting the current is controlled by the voltage signal VI through the current series negative feedback circuit or the current parallel negative feedback circuit in the current feedback driving circuit 3.

Preferably, the PWM control circuit 2 controls the DA conversion circuit 1 and the DA conversion circuit 2 through the MCU processor, the output voltage signal VI1 and the voltage signal VI2 are respectively provided to the input terminals of the analog switch U1, the MCU processor outputs the voltage signal PWM1 and the voltage signal PWM2, the voltage signal PWM2 controls the analog switch U1 through the current limiting resistor R1, so that the output voltage signal VI is selectively controlled and output between the voltage signal VI1 and the voltage signal VI 2.

Preferably, the DA converter circuit 2 in the PWM control circuit 2 is formed by serially dividing a voltage by a plurality of resistors, one end of the resistor R26 is connected to the reference voltage VCC, one end of the resistor R27 is connected to the signal ground, and the intermediate terminals of the plurality of resistors are connected to the voltage signal VI 2.

Preferably, the DA conversion circuit 2 in the PWM control circuit 2 is formed by serially dividing a voltage by a resistor R26 and a resistor R27.

Preferably, the voltage signal VD at the input end is a signal that needs to be converted and processed by the voltage conversion circuit 6, the input voltage signal VO provides power for the voltage conversion circuit 6, and the voltage signal PW input by the voltage conversion circuit 6 is a conversion control signal; the voltage signal VF output by the voltage conversion circuit 6 is provided to the voltage feedback control circuit 5.

The beneficial technical effects of the invention comprise:

(1) the laser light intensity accurate PWM control is realized, the principle process of voltage control constant current output is definitely provided, and the problem of self-adaptive change of the working voltage of the laser is solved.

(2) The heat dissipation is small, expensive heat dissipation measures are not needed, and the stability of the system is high.

(3) The current series negative feedback or current parallel negative feedback mode of the linear constant current control circuit is adopted, so that the output current can be ensured to be consistent when the pulse widths of the constant current and the pulse current are in the microsecond level, and the characteristics of high precision, controllability and good stability of the light intensity of the laser are achieved.

(4) A voltage conversion circuit and a voltage feedback control circuit are newly designed, and output feedback signals can control the switching power supply circuit with various topological structures to realize the adjustment of output voltage so as to ensure that the laser and the power tube work in the highest efficiency state.

(5) The driving circuit adopting the current depth negative feedback mode can be a current series feedback control mode topological structure or a current parallel feedback topological structure, can realize constant current or PWM constant current two-mode output functions, and realizes the constant light intensity or PWM modulation output of the laser.

(6) The PWM control circuit is adopted and comprises an MCU microprocessor, a DA conversion circuit and an analog switch, so that the flexible setting of an output voltage signal VI can be realized, and the flexible adjusting function of the light intensity of the laser can be realized.

(7) The voltage conversion circuit is adopted to obtain effective voltage drops on the power tube and the sampling resistor in the current feedback driving circuit, and the effective voltage drops are provided for the voltage feedback control circuit after operation, so that the output voltage of the system can be changed in a self-adaptive mode according to the working voltage of the laser, and the system can work in the highest efficiency state.

(8) The voltage feedback control circuit connects the voltage signal VO output by the switch power supply circuit and the voltage signal VF of the voltage conversion circuit in parallel, so as to realize the functions of regulating the working voltage of the laser and protecting the overvoltage.

(9) The switch power supply circuit can be selected from various types, which is very beneficial to the expansion of products; various circuit topologies can be employed, such as a Buck, Boost, Buck-Boost, Fly, full-bridge phase-shift, etc.

Drawings

In order to more clearly illustrate the embodiments or technical solutions in the prior art of the present invention, the drawings used in the description of the embodiments or prior art will be briefly described below, it is obvious that the drawings in the following description are only a part of the embodiments or prior art, and other similar or related drawings can be obtained by those skilled in the art without creative efforts.

Fig. 1 is a block diagram of a circuit according to an embodiment of the present invention.

Fig. 2 is a schematic diagram illustrating details of a circuit according to an embodiment of the present invention.

Fig. 3 is a circuit diagram of a second implementation of the current feedback and driving circuit according to the embodiment of the invention.

Fig. 4 is a circuit diagram of a second embodiment of the PWM control circuit according to the present invention.

Fig. 5 is a circuit diagram of a second embodiment of the voltage converting circuit according to the embodiment of the invention.

Fig. 6 is a circuit diagram of an embodiment of the switching power supply circuit according to the invention.

Fig. 7 is a block diagram of another circuit implementation according to an embodiment of the invention.

Fig. 8 is a schematic diagram illustrating details of another circuit implementation according to an embodiment of the present invention.

Fig. 9 is a circuit diagram of a second implementation of another voltage converting circuit according to an embodiment of the invention.

Detailed Description

The present invention will be described in detail with reference to examples. The present invention will be described in further detail below to make the objects, aspects and advantages of the present invention clearer and more clear, but the present invention is not limited to these examples.

In one embodiment of the invention, the laser constant current driving circuit adopting voltage and current double feedback and PWM control comprises: the laser comprises a switching power supply circuit 1, a PWM control circuit 2, a current feedback drive circuit 3, a laser circuit 4, a voltage feedback control circuit 5 and a voltage conversion circuit 6; the switching power supply circuit 1 provides electric energy for the laser circuit 4, the voltage feedback control circuit 5 and the voltage conversion circuit 6; the laser circuit 4 is connected in series between the output VO of the switching power supply circuit 1 and the input of the current feedback driving circuit 3; the current feedback driving circuit 3 is controlled by the output voltage signal VI of the PWM control circuit 2 to realize PWM constant current output; the voltage conversion circuit 6 collects a constant voltage signal or a PWM voltage signal at the input end of the current feedback driving circuit 3, converts the constant voltage signal or the PWM voltage signal into a constant voltage signal VF and provides the constant voltage signal VF for the voltage feedback control circuit 5; the voltage feedback control circuit 5 redundantly connects in parallel the voltage signal VO output by the switching power supply circuit 1 and the voltage signal VF output by the voltage conversion circuit 6, and then outputs a feedback voltage signal FB to the switching power supply circuit 1, so as to adjust the output voltage of the switching power supply circuit within a suitable range, and enable the power device of the current feedback driving circuit 3 to operate at a high efficiency. The innovation points of the embodiment are as follows: the system has two modes of constant current or PWM constant current, and the output current value can be flexibly set, so that the function of accurately controlling the output light intensity is realized; the output voltage of the system can be changed in a self-adaptive way according to the working voltage of the laser, so that the system works in the highest efficiency state; and thirdly, the output current does not change along with the change of the pulse width or the frequency, the output is constant or the pulse current has high precision, so the output light intensity has the characteristic of good stability.

In another embodiment of the present invention, a dual feedback and PWM controlled laser constant current driving circuit includes: the laser driving circuit comprises a switching power supply circuit 1, a PWM control circuit 2, a current feedback driving circuit 3, a laser circuit 4, a voltage feedback control circuit 5 and a voltage conversion circuit 6.

Preferably, the switching power supply circuit 1 is connected to the voltage feedback control circuit 5, the laser circuit 4, and the voltage conversion circuit 6, respectively; the feedback circuit is used for receiving a feedback voltage signal FB output by the voltage feedback control circuit 5; and outputs a voltage signal VO to the voltage feedback control circuit 5, the laser circuit 4, and the voltage conversion circuit 6.

Preferably, the PWM control circuit 2 is connected to the current feedback driving circuit 3 and the voltage conversion circuit 6 respectively; the voltage signal VI is connected to the input of the current feedback driving circuit 3, and the voltage signal PW is connected to the input of the voltage converting circuit 6.

Preferably, the current feedback driving circuit 3 is respectively connected to the PWM control circuit 2, the laser circuit 4, and the voltage conversion circuit 6; the sampling resistor R7 samples the current flowing through the resistor, and then the output current control is realized by the voltage signal VI through the current series negative feedback circuit or the current parallel negative feedback circuit provided in the current feedback driving circuit 3.

Preferably, the laser circuit 4 is respectively connected to the switching power supply circuit 1, the voltage feedback control circuit 5, the voltage conversion circuit 6, and the current feedback driving circuit 3; and is configured to receive the voltage signal VO input by the voltage conversion circuit 6, and output a voltage signal VD to the current feedback driving circuit 3 and the voltage conversion circuit 6.

Preferably, the voltage feedback control circuit 5 is respectively connected to the switching power supply circuit 1, the laser circuit 4, and the voltage conversion circuit 6; the voltage signal VD passes through the voltage conversion circuit 6 to output a voltage signal VF and then passes through the voltage feedback control circuit 5 to output a feedback voltage signal FB

Preferably, the voltage conversion circuit 6 is respectively connected to the switching power supply circuit 1, the PWM control circuit 2, the current feedback drive circuit 3, the laser circuit 4, and the voltage feedback control circuit 5; the voltage signal VD and the voltage signal VS output a voltage signal VF through the voltage conversion circuit 6; the voltage signal VI of the PWM control circuit 2 is connected with the input of the current feedback drive circuit 3; the voltage signal PW is connected to an input of the voltage conversion circuit 6.

Preferably, the current signal ID flowing through the laser circuit is a signal that the voltage conversion circuit 6 needs to convert and process; the voltage signal VD and the voltage signal VS are the voltages of the drain electrode and the source electrode of the power MOS tube in the current feedback driving circuit 3; an input voltage signal PW of the voltage conversion circuit 6 is a conversion control signal; the voltage conversion circuit 6 outputs a voltage signal VF to the voltage feedback control circuit 5; the output voltage signal VO is an output voltage that is adaptively adjusted and supplies power to the voltage conversion circuit 6.

In another embodiment of the present invention, a dual feedback PWM constant current driving circuit includes: the device comprises a switching power supply circuit 1, a PWM control circuit 2, a current feedback drive circuit 3, a light source circuit 7, a voltage feedback control circuit 5 and a voltage conversion circuit 6;

the PWM control circuit 2 is connected to the current feedback driving circuit 3 and the voltage converting circuit 6, respectively; the voltage signal VI is connected to the input of the current feedback driving circuit 3, and the voltage signal PW is connected to the input of the voltage converting circuit 6.

Preferably, the voltage signal VD at the input terminal is a signal that needs to be converted and processed by the voltage conversion circuit 6; the input voltage signal VO provides electric energy for the voltage conversion circuit 6; an input voltage signal PW of the voltage conversion circuit 6 is a conversion control signal; the voltage conversion circuit 6 outputs a voltage signal VF to the voltage feedback control circuit 5.

In still another embodiment of the present invention, a dual feedback PWM constant current driving circuit control method is provided. Wherein, the circuit includes: the device comprises a switching power supply circuit 1, a PWM control circuit 2, a current feedback drive circuit 3, a laser circuit 4, a voltage feedback control circuit 5 and a voltage conversion circuit 6;

the control method of the double-feedback PWM constant-current driving circuit comprises the following steps: a voltage feedback step and a current feedback step.

Preferably, the voltage feedback step further includes: the voltage signal VD passes through the voltage conversion circuit 6 to output a voltage signal VF, and then passes through the voltage feedback control circuit 5 to output a feedback voltage signal FB, which controls the process of the switching power supply circuit 1 outputting the voltage signal VO;

preferably, the current feedback step further includes: the sampling resistor R7 in the current feedback driving circuit 3 samples the current flowing through the resistor, and then controls the process of outputting current through the voltage signal VI through the current series negative feedback circuit or the current parallel negative feedback circuit.

Preferably, the PWM control circuit 2 controls the DA conversion circuit 1 and the DA conversion circuit 2 through the MCU processor, the output voltage signal VI1 and the voltage signal VI2 are respectively provided to the input terminals of the analog switch U1, the MCU processor outputs the voltage signal PWM1 and the voltage signal PWM2, and the voltage signal PWM2 controls the analog switch U1 through the current limiting resistor R1, so that the output voltage signal VI is selectively controlled and output between the voltage signal VI1 and the voltage signal VI 2.

Preferably, the voltage feedback control circuit 5 inputs the voltage signal VO and the voltage signal VF, and outputs a feedback voltage signal FB; the voltage feedback control circuit 5 redundantly connects in parallel the voltage signal VO output by the switching power supply circuit 1 and the output voltage signal VF of the voltage conversion circuit 6, and then outputs a feedback voltage signal FB to the switching power supply circuit 1, so as to adjust the output voltage of the switching power supply circuit.

Preferably, the voltage signal VD at the input terminal is a signal that needs to be converted and processed by the voltage converting circuit 6, the input voltage signal VO provides power for the voltage converting circuit 6, and the voltage signal PW input by the voltage converting circuit 6 is a conversion control signal; the voltage conversion circuit 6 outputs a voltage signal VF to the voltage feedback control circuit 5.

Preferably, in the voltage feedback control circuit 5, the voltage signal VO is connected to the terminal 1 of the resistor R9, the terminal 2 of the resistor R9 is connected to the terminal 1 of the resistor R10 and the anode of the diode D3, the terminal 2 of the resistor R10 is connected to signal ground, and the cathode of the diode D3 is connected to the feedback voltage signal FB; the voltage signal VF is connected with a terminal 1 of the resistor R11, a terminal 2 of the resistor R11 is connected with a terminal 1 of the resistor R12 and an anode of the diode D4, a terminal 2 of the resistor R12 is connected with the signal ground, and a cathode of the diode D4 is connected with the feedback voltage signal FB.

In another embodiment of the present invention, a dual feedback PWM constant current driving circuit control method is provided, the circuit includes: the device comprises a switching power supply circuit 1, a PWM control circuit 2, a current feedback drive circuit 3, a light source circuit 7, a voltage feedback control circuit 5 and a voltage conversion circuit 6; the method comprises the following steps: a voltage feedback step and a current feedback step.

preferably, the current feedback step further includes: the sampling resistor R7 in the current feedback driving circuit 3 samples the current flowing through the sampling resistor R7, and then controls the process of outputting the current through the voltage signal VI via the current series negative feedback circuit or the current parallel negative feedback circuit.

Preferably, the voltage signal VD at the input terminal is a signal that needs to be converted and processed by the voltage converting circuit 6, the input voltage signal VO provides power for the voltage converting circuit 6, and the input voltage signal PW of the voltage converting circuit 6 is a conversion control signal; the voltage conversion circuit 6 outputs a voltage signal VF to the voltage feedback control circuit 5.

The technical route adopted by the invention comprises the following steps:

the PWM constant current driving circuit adopting voltage and current double feedback control comprises a switching power supply circuit 1, a PWM control circuit 2, a current feedback driving circuit 3, a laser circuit 4 or a light source circuit 7, a voltage feedback control circuit 5 and a voltage conversion circuit 6;

the voltage feedback in the double feedback refers to a process that a voltage signal VD passes through a voltage conversion circuit 6 and a voltage feedback control circuit 5, and a feedback voltage signal FB is output to control a switching power supply circuit to output a voltage signal VO; the current feedback in the double feedback refers to that a sampling resistor R7 in the current feedback driving circuit 3 samples the current in a loop, and then the function of controlling the output current through a voltage signal VI is realized through a current series negative feedback or a current parallel negative feedback circuit;

the switch power supply circuit 1 provides electric energy for the laser circuit 4 or the light source circuit 7, the voltage feedback control circuit 5 and the voltage conversion circuit 6; each module adopts the same grounding signal; the switching power supply circuit 1 outputs a voltage signal VO and feeds back a voltage signal FB; the switching power supply circuit can adopt a Buck topological structure circuit, a Boost topological structure circuit, a Buck-Boost structural circuit, a push-pull structural circuit, a half-bridge topological structure circuit or a full-bridge moving direction topological structure circuit;

the PWM control circuit 2 outputs a voltage signal VI and a voltage signal PW, the voltage signal VI is input to the current feedback drive circuit, and the voltage signal PW is output to the voltage conversion circuit;

preferably, one implementation scheme of the PWM control circuit is: the MCU processor controls the DA conversion circuit 1 and the DA conversion circuit 2 in the PWM control circuit, an output voltage signal VI1 and a voltage signal VI2 are respectively provided for an input terminal of the analog switch U1, the MCU processor outputs PWM1 and PWM2 signals, and the PWM1 controls the analog switch U1 after passing through the current-limiting resistor R1, so that the output voltage signal VI is selectively controlled and output between the voltage signal VI1 and the voltage signal VI 2;

the MCU processor can select one or a combination of a plurality of single chip microcomputer, ARM, CPU or FPGA unit circuits; an output voltage signal VI and a voltage PW signal of the PWM control circuit are respectively provided for the current feedback drive circuit and the voltage conversion circuit, the voltage signal VI is used for controlling the output current, and the PW is used for controlling the opening and closing of a sampling switch tube of the voltage conversion circuit;

preferably, another implementation scheme of the PWM control circuit: the DA conversion circuit 2 in the PWM control circuit can be formed by connecting two resistors in series and dividing voltage, one end of the resistor R26 is connected with a reference voltage VCC, one end of the resistor R27 is connected with a signal ground, and the middle terminals of the two resistors are connected with a voltage signal VI 2;

the current feedback driving circuit 3 receives a voltage signal VI and a voltage signal VD; the voltage signal VI corresponds to the magnitude of the output constant current or PWM pulse current; the voltage signal VD terminal flows into the output current of the LED/LD circuit and flows out through the grounding terminal of the current feedback current; the current feedback driving circuit comprises a current sampling resistor R7, wherein one end of the sampling resistor R7 is connected with current, and the other end is connected with a signal ground;

preferably, an implementation scheme of the current feedback driving circuit comprises the following steps: the current feedback driving circuit adopts a circuit structure of current series negative feedback topology; the voltage signal VI is connected with a terminal 1 of a resistor R3, and a terminal 2 of a resistor R3 is connected with a non-inverting input end of the operational amplifier U2; the reverse input end of the operational amplifier U2 is connected with the anode of the diode D1, the terminal 1 of the capacitor C1 and the terminal 1 of the resistor R6; the diode D1 and the resistor R4 are connected in series to improve the dynamic characteristic of the operational amplifier U2, the cathode of the diode D1 is connected with the terminal 1 of the resistor R4, and the terminal 2 of the resistor R4 is connected with the output end of the operational amplifier U2; the terminal 2 of the capacitor C1 is connected with the output end of the operational amplifier U2; the output end of the operational amplifier U2 is connected with the terminal 1 of the resistor R5, and the terminal 2 of R5 is connected with the grid of the MOS tube M1; a terminal 2 of the resistor R6 is connected with a terminal 1 of the sampling resistor R7 and a source electrode of the MOS transistor M1, a terminal 2 of the resistor R7 is connected with a signal ground, a drain electrode of the MOS transistor M1 is connected with an input signal VD, the drain electrode is connected with a terminal 1 of the capacitor C2, and a terminal 2 of the capacitor C2 is connected with the signal ground; the calculation formula of the output current by adopting the scheme is as follows:

equation 1

Wherein, the voltage signal VI is the voltage value of the input port VI, and the sampling resistor R7 is the resistance value of the current sampling resistor;

preferably, another implementation scheme of the current feedback driving circuit comprises the following steps: the current feedback driving circuit adopts a circuit structure of current parallel negative feedback topology; the voltage signal VI is connected with a terminal 1 of the resistor R3, and a terminal 2 of the resistor R3 is connected with an inverted input end of the operational amplifier U2, an anode of the diode D, a terminal 1 of the capacitor C1 and a terminal 1 of the resistor R6; the resistors R22 and R23 divide voltage to provide reference voltage Vref for the non-inverting input end of the operational amplifier U2, the non-inverting input end of the operational amplifier U2 is connected with the terminal 1 of the resistor R22 and the terminal 1 of the resistor R23, the terminal 2 of the resistor R22 is connected with the reference voltage VCC1, and the resistor R23 is connected with signal ground; the diode D1 and the resistor R4 are connected in series to improve the dynamic characteristic of the operational amplifier U2, the cathode of the diode D1 is connected with the terminal 1 of the resistor R4, and the terminal 2 of the resistor R4 is connected with the output end of the operational amplifier U2; the terminal 2 of the capacitor C1 is connected with the output end of the operational amplifier U2; the output end of the operational amplifier U2 is connected with the terminal 1 of the resistor R5, and the terminal 2 of the resistor R5 is connected with the grid of the MOS tube M1; a terminal 2 of the resistor R6 is connected with a terminal 1 of the sampling resistor R7 and a source electrode of the MOS transistor M1, a terminal 2 of the resistor R7 is connected with a signal ground, a drain electrode of the resistor M1 is connected with an input signal VD, a drain electrode is connected with a terminal 1 of the capacitor C2, and a terminal 2 of the capacitor C2 is connected with the signal ground; the calculation formula of the output current by adopting the scheme is as follows:

equation 2

The input signal of the laser circuit 4 or the LED/LD light source circuit 7 is a voltage signal VO, and the output signal is a voltage VD; the LED lamp group circuit 4 is connected in series between the switching power supply circuit 1 and the current feedback drive circuit 3, and a current signal flows in from a VO terminal and flows out from a VD terminal;

preferably, the laser circuit/LED/LD light source circuit has a composition: the input of the voltage signal VO is connected with the anode of the LED/LD, and is also connected with the terminal 1 of the resistor R8 and the cathode of the diode D2; the cathode of the LED/LD is connected with an output voltage VD signal, and is also connected with a terminal 1 of a capacitor C3 and the anode of a diode D2; a terminal 2 of the resistor R8 is connected with a terminal 2 of the capacitor C3; the LED/LD can be a single LED or LD device, or a module formed by connecting a plurality of LED chips in series and in parallel, or a module formed by connecting a plurality of LDs in series; the resistor R8 and the capacitor C3 form a resistance-capacitance absorption circuit; the diode D2 plays a role in reverse current drainage;

the voltage feedback control circuit 5 inputs a voltage signal VO and a voltage signal VF and outputs a feedback voltage signal FB; the voltage feedback control circuit 5 redundantly connects in parallel the voltage signal VO output by the switching power supply circuit 1 and the voltage signal VF output by the voltage conversion circuit 6, and then outputs a feedback voltage signal FB to the switching power supply circuit 1, so as to adjust the output voltage of the switching power supply circuit within a suitable range, and enable the power device of the current feedback driving circuit 3 to operate at a high efficiency.

Preferably, the voltage feedback control circuit comprises: the voltage signal VO is connected with a terminal 1 of a resistor R9, a terminal 2 of a resistor R9 is connected with a terminal 1 of a resistor R10 and an anode of a diode D3, a terminal 2 of the resistor R10 is connected with a signal ground, and a cathode of a diode D3 is connected with a feedback voltage signal FB; the voltage signal VF is connected with a terminal 1 of the resistor R11, a terminal 2 of the resistor R11 is connected with a terminal 1 of the resistor R12 and an anode of the diode D4, a terminal 2 of the resistor R12 is connected with the signal ground, and a cathode of the diode D4 is connected with the feedback voltage signal FB;

the voltage signals VD and VS at the input end of the voltage conversion circuit 6 are signals that the voltage conversion circuit 6 needs to perform conversion and processing, the input voltage signal VO provides electric energy for the voltage conversion circuit 6, and the input voltage signal PW of the voltage conversion circuit 6 is a conversion control signal; the voltage conversion circuit 6 outputs a voltage signal VF to the voltage feedback control circuit 5;

preferably, an implementation of the voltage conversion circuit 6: the drain electrode of the MOS tube M2 is a path control switch for inputting a signal VD, and the grid electrode of the M2 is provided with a control signal by a driving circuit which is composed of resistors R13, R14, R15, R16, an optocoupler U5 and a triode T1; the drain of the MOS tube M3 is a path control switch for an input signal VS, the gate of the MOS tube M3 is connected to the gate of the MOS tube M2, the source of the MOS tube M3 is connected to a resistor R22 and then connected to the negative input end of the operational amplifier U3, and the source of the MOS tube M3 is connected to a capacitor C6 to signal ground; the input voltage signal PW is connected with a terminal 1 of a resistor R13, a terminal 2 of a resistor R13 is connected with an input terminal 1 of an optocoupler U5, and an input terminal 2 of an optocoupler U5 is connected with a signal ground; a voltage signal VO is input and then connected with a terminal 1 of a resistor R14, and simultaneously connected with a terminal 1 of a resistor R15, a terminal 2 of a resistor R14 is simultaneously connected with a terminal 3 of an optocoupler U5 and a terminal 1 of a resistor R16, a terminal 2 of R16 is connected with a base electrode of a triode T1, and an emitter electrode of the triode T1 and a terminal 4 of the optocoupler U5 are connected and then connected with a signal ground; a terminal 2 of the resistor R15 is connected with a collector of the triode T1 and is simultaneously connected with a grid electrode of the MOS transistor M2 to control the work of the MOS transistor M2;

the voltage signal VD passes through a drain electrode of the MOS tube, and enters an in-phase proportional-integral circuit after coming out of a source electrode, the in-phase proportional-integral circuit consists of resistors R17, R18, R19, R20, R21 and a capacitor C5, a capacitor C4 is an input signal storage and filter capacitor, and a capacitor C6 is an output signal storage and filter capacitor; a terminal 1 of the resistor R17 and a terminal 1 of the capacitor C4 are connected and then connected to the source of the MOS transistor M2, a terminal 2 of the capacitor C4 is connected with the signal ground, a terminal 2 of the resistor R17 is simultaneously connected with a non-inverting input end of the operational amplifier U3 and a terminal 1 of the resistor R18, and a terminal 2 of the resistor R18 is connected with the signal ground; the reverse input end of the operational amplifier U2 is simultaneously connected with the terminal 1 of the resistor R19, the terminal 1 of the resistor R21 and the terminal 1 of the capacitor C5, and the terminal 2 of the resistor R19 is connected with the signal ground; the output end of the operational amplifier U3 is simultaneously connected with the terminal 2 of the resistor R21, the terminal 2 of the capacitor C5 and the terminal 1 of the resistor R20; the terminal 2 of the resistor R20 is connected to the terminal 1 of the capacitor C6 and the voltage signal VF, the terminal 2 of the capacitor C6 is connected to the signal ground, and the voltage signal VF is supplied to the voltage feedback control circuit.

Preferably, another implementation of the voltage conversion circuit 6: the optocoupler U5 in the voltage conversion circuit described above may be replaced by a transistor T2. The input voltage signal PW is connected with a terminal 1 of a resistor R13, a terminal 2 of a resistor R13 is connected with a base electrode of a triode T2, and an emitting electrode of a triode T2 is connected with the signal ground; the voltage signal VO is input and then connected with a terminal 1 of a resistor R14, a terminal 1 of a resistor R15, a terminal 2 of a resistor R14, a collector of a triode T2 and a terminal 1 of a resistor R16, a terminal 2 of a resistor R16 is connected with a base of a triode T1, and an emitter of the triode T1 is connected with a signal ground; and a terminal 2 of the resistor R15 is connected with a collector of the triode T1 and is also connected with the grid of the MOS transistor M2 to control the operation of the MOS transistor M2.

Example 1:

as shown in fig. 1 and fig. 2, a block diagram of a circuit implementation according to an embodiment of the present invention and a schematic diagram of a detailed circuit implementation according to an embodiment of the present invention are shown, respectively. In the implementation block diagram shown in fig. 1, the method includes: the laser comprises a switching power supply circuit, a PWM control circuit, a current feedback drive circuit, a laser circuit, a voltage feedback control circuit and a voltage conversion circuit.

The specific implementation details are shown in fig. 2:

the output voltage signal VO of the switching power supply circuit is supplied to the laser circuit and the voltage conversion circuit as electric energy supply, the voltage signal VO is supplied to the voltage feedback control circuit for carrying out overvoltage protection point setting, and the output feedback voltage signal FB of the voltage feedback control circuit is supplied to the switching power supply circuit for controlling the output voltage;

the PWM control circuit controls the two DA conversion circuits to be respectively provided for a signal terminal of an analog switch U1 through the MCU processor, the MCU processor outputs a voltage signal PWM1 and a voltage signal PWM2, the voltage signal PWM2 controls the analog switch U1 after passing through a current-limiting resistor R1, and the output voltage signal VI is subjected to selective PWM control output between the DA conversion circuit 1 and the DA conversion circuit 2; the PWM control circuit outputs a voltage signal VI and a voltage signal PW, the voltage signal VI is provided for the current feedback drive circuit to control the output current, the voltage signal PW is provided for the voltage conversion circuit, and the voltage signal PW is used for controlling the opening and closing of a sampling switch tube of the voltage conversion circuit;

the laser circuit is a circuit connected with a load, is connected in series between a voltage signal VO and a voltage signal VD, and flows constant current or PWM constant current; a resistor R8 and a capacitor C3 in the LED conversion circuit form a resistance-capacitance circuit which is used for absorbing high-frequency oscillation when the LED or LD module is turned on or turned off; the reverse diode D2 is used for discharging reverse surge current;

the current feedback driving circuit is a current series deep negative feedback circuit, a voltage signal VI and a voltage signal VD are input into the current series deep negative feedback circuit, the voltage signal VI and output current form a linear control relation, and the output current relation is shown as a formula 1. The resistor R4 and the diode D1 play a role in smoothing overshoot at the moment of switching on, C1 is an integrating capacitor, R5 is used for zero pole configuration of the conditional operational amplifier U2, and R6 is used for reducing noise; the device M1 is an MOS tube and is a key device of the whole system, and the M1 is in a linear constant current region when in normal operation;

a voltage signal PW of the voltage conversion circuit is generated by a PWM control circuit and is mainly used for controlling the on and off of an MOS (metal oxide semiconductor) tube M2 so as to enable a VD signal to pass through an in-phase proportional-integral circuit formed by an operational amplifier U3 and then output a voltage signal VF to a voltage feedback control circuit; r13, U5, R14, R16, T1 and R15 in the voltage conversion circuit form a level conversion circuit for driving the MOS transistor M2 to be switched on and off;

the voltage feedback control circuit respectively carries out resistance series voltage division on the voltage signal VO and the voltage signal VF, the divided signals are respectively connected in parallel through a diode D3 and a diode D4, and then a feedback voltage signal FB is output and provided for the switching power supply circuit, and the feedback voltage signal FB is used for controlling the output voltage of the switching power supply circuit and carrying out overvoltage protection limitation.

Example 2:

fig. 3 is a circuit diagram of a second implementation of the current feedback and driving circuit according to the embodiment of the present invention. The implementation block diagram of the dual feedback controlled PWM constant current driving circuit of this embodiment is shown in fig. 1, and the difference from embodiment 1 is that the current feedback circuit adopts the scheme shown in fig. 3;

the current feedback circuit of fig. 3 constitutes a current parallel deep negative feedback circuit; the voltage signal VI is connected to the PWM control circuit and is used for controlling the magnitude of the output current, and the calculation of the output current is shown as formula 2; the voltage signal VD is connected to the laser circuit, and the depth negative feedback circuit controls the MOS tube M1 to work in a linear constant current area, so that the constant current output control of the whole circuit is realized.

Example 3:

fig. 4 is a circuit diagram of a second embodiment of the PWM control circuit according to the embodiment of the present invention. A block diagram of a dual feedback controlled PWM constant current driving circuit of this embodiment is shown in fig. 1, and the difference from embodiment 1 is that the PWM control circuit adopts the scheme shown in fig. 4;

the PWM control circuit in fig. 4 is different from the PWM control circuit in fig. 2 in that the DA conversion circuit 2 in fig. 2 is replaced with the divided voltage of the resistor R26 and the resistor R27 in fig. 5, and the other parts are the same as those in embodiment 1.

The setting of resistor R26 and resistor R27 is as follows: for the case that the current feedback driving circuit in the circuit diagram of embodiment 1 adopts current series negative feedback, at this time, the resistor R26 adopts a resistance value of more than 4.7k Ω or does not need to be assembled, the resistor R27 adopts a resistance value of 0 Ω, and at this time, when the analog switch U1 is connected to this path, it is equivalent to that the output voltage signal VI is low level, and it can be seen from formula 1 that the output current is 0A; for the case that the current feedback driving circuit in the circuit diagram of embodiment 2 adopts the current parallel negative feedback, at this time, the resistor R26 adopts a resistor with a resistance of 0 Ω, and the resistor R27 adopts a resistor with a resistance of 4.7k Ω or more, and at this time, when the analog switch U1 is connected to this path, it is equivalent to that the output voltage signal VI is high level, and it can be seen from formula 2 that the output current is 0A.

Example 4:

fig. 5 is a circuit diagram of a second embodiment of the voltage converting circuit according to the embodiment of the present invention. The implementation block diagram of the dual feedback controlled PWM constant current driving circuit of this embodiment is shown in fig. 1, and the difference from embodiment 1 is that the voltage conversion circuit adopts the scheme shown in fig. 5;

the voltage conversion circuit in fig. 5 is different from the voltage conversion circuit in fig. 2 in that the optocoupler U5 of the voltage conversion circuit in fig. 2 is replaced by the transistor T2 in fig. 5, and the rest of the embodiment 1 is the same.

Example 5:

fig. 6 is a circuit diagram of an embodiment of the switching power supply circuit according to the invention. A block diagram of a dual feedback and PWM controlled laser constant current driving circuit in this embodiment is shown in fig. 1, and the difference from embodiment 1 is that a switching power supply circuit adopts a circuit scheme with a Buck structure as shown in fig. 6, and a core chip of the switching power supply circuit is LTC 3892-1.

Example 6:

fig. 7 and fig. 8 are a block diagram of another circuit implementation according to the embodiment of the present invention and a schematic diagram of details of another circuit implementation according to the embodiment of the present invention, respectively. In the implementation block diagram shown in fig. 7, the method includes: the LED driving circuit comprises a switching power supply circuit, a PWM control circuit, a current feedback driving circuit, an LED or LD circuit, a voltage feedback control circuit and a voltage conversion circuit.

The specific implementation details are shown in fig. 8:

the voltage feedback control circuit outputs a feedback voltage signal FB which is provided for the switching power supply circuit to control the magnitude of the output voltage;

the LED/LD circuit is a circuit connected with a load, is connected between a voltage signal VO and a voltage signal VD in series, and flows constant current or PWM constant current; a resistor R8 and a capacitor C3 in the LED conversion circuit form a resistance-capacitance circuit which is used for absorbing high-frequency oscillation when the LED or LD module is turned on or turned off; the reverse diode D2 is used for discharging reverse surge current;

the current feedback driving circuit is a current series deep negative feedback circuit, a voltage signal VI and a voltage signal VD are input into the current series deep negative feedback circuit, the voltage signal VI and output current form a linear control relation, and the output current relation is shown as a formula 1. The resistor R4 and the diode D1 play a role in smoothing overshoot at the moment of switching on, C1 is an integrating capacitor, R5 is used for zero pole configuration of the conditional operational amplifier U2, and R6 is used for reducing noise; m1 is an MOS tube, which is a key device of the whole system, and the MOS tube M1 is in a linear constant current region when working normally;

a voltage signal PW of the voltage conversion circuit is generated by a PWM control circuit and is mainly used for controlling the on and off of an MOS (metal oxide semiconductor) tube M2 so as to enable a voltage signal VD to output a voltage signal VF to a voltage feedback control circuit after passing through an in-phase proportional-integral circuit formed by an operational amplifier U3; r13, U5, R14, R16, T1 and R15 in the voltage conversion circuit form a level conversion circuit for driving the MOS transistor M2 to be switched on and off;

the voltage feedback control circuit respectively carries out resistance series voltage division on the voltage signal VO and the voltage signal VF, the divided signals are respectively connected in parallel through diodes D3 and D4, and then a feedback voltage signal FB is output and provided for the switching power supply circuit, and the feedback voltage signal FB is used for controlling the output voltage of the switching power supply circuit and carrying out overvoltage protection limitation.

Example 7:

the current feedback circuit of fig. 3 constitutes a current parallel deep negative feedback circuit; the voltage signal VI is connected to the PWM control circuit and is used for controlling the magnitude of the output current, and the calculation of the output current is shown as formula 2; the voltage signal VD is connected to the LED/LD circuit, and the depth negative feedback circuit controls the MOS tube M1 to work in a linear constant current area, so that the constant current output control of the whole circuit is realized.

Example 8:

fig. 4 is a circuit diagram of a second embodiment of the PWM control circuit according to the embodiment of the present invention. A block diagram of a dual feedback controlled PWM constant current driving circuit of this embodiment is shown in fig. 7, which is different from embodiment 6 in that the PWM control circuit adopts the scheme shown in fig. 4;

the PWM control circuit in fig. 4 is different from the PWM control circuit in fig. 7 in that the DA conversion circuit 2 in fig. 7 is replaced with the divided voltage of the resistor R26 and the resistor R27 in fig. 9, and the other parts are the same as in embodiment 6.

The resistors R26 and R27 are set as follows: for the case that the current feedback driving circuit in the circuit diagram of embodiment 6 adopts current series negative feedback, at this time, the resistor R26 adopts a resistance value of more than 4.7k Ω or does not need to be assembled, the resistor R27 adopts a resistance value of 0 Ω, and at this time, when the analog switch U1 is connected to this path, it is equivalent to that the output voltage signal VI is a bottom level, and it can be seen from formula 1 that the output current is 0A; for the case that the current feedback driving circuit in the circuit diagram of embodiment 7 adopts the current parallel negative feedback, at this time, the resistor R26 adopts a resistor with a resistance of 0 Ω, and the resistor R27 adopts a resistor with a resistance of 4.7k Ω or more, and at this time, when the analog switch U1 is connected to this path, it is equivalent to that the output voltage signal VI is high level, and it can be seen from formula 2 that the output current is 0A.

Example 9:

fig. 9 is a circuit diagram of a second implementation of another voltage converting circuit according to an embodiment of the invention. The implementation block diagram of the dual feedback controlled PWM constant current driving circuit of this embodiment is shown in fig. 7, and the difference from embodiment 6 is that the voltage conversion circuit adopts the scheme shown in fig. 9;

the voltage conversion circuit in fig. 9 is different from the voltage conversion circuit in fig. 8 in that the optocoupler U5 of the voltage conversion circuit in fig. 8 is replaced by the transistor T2 in fig. 9, and the rest of the embodiment 6 is the same.

Example 10:

fig. 6 is a circuit diagram of an embodiment of the switching power supply circuit according to the invention. Fig. 7 shows a block diagram of a dual feedback controlled PWM constant current driving circuit according to this embodiment, which is different from the embodiment 6 in that a switching power supply circuit adopts a circuit scheme with a Buck structure as shown in fig. 6, and a core chip of the switching power supply circuit is LTC 3892-1.

In the above embodiment examples 1 to 10, if a constant current output is required, the voltage signal PW output from the PWM control circuit should constantly output a high level.

In the above embodiments 1-10, if PWM constant current output is required, the voltage signal PWM1 and the voltage signal PWM2 of the PWM control circuit should be controlled synchronously, and when the MOS transistor M2 of the current feedback driving circuit turns on the output signal, the MOS transistor M2 of the voltage conversion circuit should be turned on, and at this time, the voltage signal VD is sampled.

Although the present invention has been described with reference to a few exemplary embodiments, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. A control method of a double-feedback PWM constant current drive circuit is characterized in that,

the double-feedback PWM constant-current driving circuit comprises: the device comprises a switching power supply circuit (1), a PWM control circuit (2), a current feedback drive circuit (3), a light source circuit (7), a voltage feedback control circuit (5) and a voltage conversion circuit (6);

the switching power supply circuit (1) is respectively connected with the voltage feedback control circuit (5), the light source circuit (7) and the voltage conversion circuit (6); the feedback voltage signal FB is used for receiving a feedback voltage signal FB output by the voltage feedback control circuit (5); and outputs a voltage signal VO to the voltage feedback control circuit (5), the light source circuit (7) and the voltage conversion circuit (6);

the PWM control circuit (2) is respectively connected with the current feedback drive circuit (3) and the voltage conversion circuit (6); a voltage signal VI is connected with the current feedback driving circuit (3), and a voltage signal PW is connected with the voltage conversion circuit (6);

the current feedback driving circuit (3) is respectively connected with the PWM control circuit (2), the light source circuit (7) and the voltage conversion circuit (6);

the light source circuit (7) is respectively connected with the switching power supply circuit (1), the voltage feedback control circuit (5), the voltage conversion circuit (6) and the current feedback drive circuit (3); the voltage conversion circuit is used for receiving a voltage signal VO input by the switching power supply circuit (1) and outputting a voltage signal VD to the current feedback driving circuit (3) and the voltage conversion circuit (6);

the voltage feedback control circuit (5) is respectively connected with the switching power supply circuit (1), the light source circuit (7) and the voltage conversion circuit (6);

the voltage conversion circuit (6) is respectively connected with the switching power supply circuit (1), the PWM control circuit (2), the current feedback drive circuit (3), the light source circuit (7) and the voltage feedback control circuit (5);

the voltage feedback step further includes: the voltage signal VD passes through the voltage conversion circuit (6) to output a voltage signal VF, the voltage signal VO and the voltage signal VF output by the switching power supply circuit (1) pass through the voltage feedback control circuit (5) to output a feedback voltage signal FB, and the feedback voltage signal FB controls the process of outputting the voltage signal VO by the switching power supply circuit (1);

the current feedback step further includes: the sampling resistor R7 in the current feedback driving circuit (3) samples the current flowing through the sampling resistor R7, and then the current passes through a current series negative feedback circuit or a current parallel negative feedback circuit in the current feedback driving circuit (3), and the process of outputting the current is controlled by the voltage signal VI.

2. The dual-feedback PWM constant current driving circuit control method according to claim 1, wherein a voltage signal VI of the PWM control circuit (2) is connected with an input of the current feedback driving circuit (3), and a voltage signal PW is connected with an input of the voltage conversion circuit (6).

3. The control method of the dual-feedback PWM constant current driving circuit as claimed in claim 1, wherein the PWM control circuit (2) controls the DA conversion circuit 1 and the DA conversion circuit 2 through the MCU processor, the output voltage signal VI1 and the voltage signal VI2 are respectively provided to the input terminal of the analog switch U1, the MCU processor outputs the voltage signal PWM1 and the voltage signal PWM2, the voltage signal PWM2 controls the analog switch U1 after passing through the current limiting resistor R1, so that the output voltage signal VI can be selectively controlled and output between the voltage signal VI1 and the voltage signal VI 2.

4. The control method of the dual-feedback PWM constant current driving circuit according to claim 3, wherein the DA conversion circuit 2 in the PWM control circuit (2) is composed of a plurality of resistors connected in series and divided, one end of the resistor R26 is connected with a reference voltage VCC, one end of the resistor R27 is connected with a signal ground, and the intermediate terminals of the plurality of resistors are connected and then connected with the voltage signal VI 2.

5. The control method of the double-feedback PWM constant-current drive circuit as claimed in claim 4, wherein the DA conversion circuit 2 in the PWM control circuit (2) is composed of a resistor R26 and a resistor R27 which are connected in series and divided in voltage.

6. The control method of the double-feedback PWM constant-current drive circuit according to claim 1, wherein the current feedback drive circuit (3) adopts a circuit structure of a current series negative feedback topology as follows: the voltage signal VI is connected with a terminal 1 of a resistor R3, and a terminal 2 of a resistor R3 is connected with a non-inverting input end of the operational amplifier U2; the reverse input end of the operational amplifier U2 is connected with the anode of the diode D1, the terminal 1 of the capacitor C1 and the terminal 1 of the resistor R6; the diode D1 and the resistor R4 are connected in series to improve the dynamic characteristic of the operational amplifier U2, the cathode of the diode D1 is connected with the terminal 1 of the resistor R4, and the terminal 2 of the resistor R4 is connected with the output end of the operational amplifier U2.

7. The control method of the double-feedback PWM constant-current drive circuit according to claim 1, wherein the current feedback drive circuit (3) adopts a circuit structure of a current parallel negative feedback topology: the voltage signal VI is connected with a terminal 1 of a resistor R3, and a terminal 2 of a resistor R3 is connected with an inverted input end of an operational amplifier U2, an anode of a diode D1, a terminal 1 of a capacitor C1 and a terminal 1 of a resistor R6; the resistors R22 and R23 divide the voltage to provide a reference voltage Vref for the non-inverting input end of the operational amplifier U2, the non-inverting input end of the operational amplifier U2 is connected with the terminal 1 of the resistor R22 and the terminal 1 of the resistor R23, the terminal 2 of the resistor R22 is connected with the reference voltage VCC1, and the resistor R23 is connected with the signal ground.

8. The control method of the double-feedback PWM constant-current drive circuit according to claim 1, wherein the voltage feedback control circuit (5) inputs a voltage signal VO and a voltage signal VF and outputs a feedback voltage signal FB; and the voltage feedback control circuit (5) redundantly connects in parallel the voltage signal VO output by the switching power supply circuit (1) and the voltage signal VF output by the voltage conversion circuit (6), and outputs the feedback voltage signal FB to the switching power supply circuit (1) for regulating the output voltage of the switching power supply circuit.

9. The control method of the double-feedback PWM constant-current driving circuit according to claim 2, wherein a voltage signal VD at an input end is a signal which needs to be converted and processed by the voltage conversion circuit (6), an input voltage signal VO supplies electric energy to the voltage conversion circuit (6), and a voltage signal PW input by the voltage conversion circuit (6) is a conversion control signal; the voltage signal VF output by the voltage conversion circuit (6) is provided for the voltage feedback control circuit (5).

10. The dual-feedback PWM constant current driving circuit control method as claimed in claim 1, wherein in the voltage feedback control circuit (5), the voltage signal VO is connected with the terminal 1 of a resistor R9, the terminal 2 of a resistor R9 is connected with the terminal 1 of a resistor R10 and the anode of a diode D3, the terminal 2 of the resistor R10 is connected with a signal ground, and the cathode of a diode D3 is connected with the feedback voltage signal FB; the voltage signal VF is connected with a terminal 1 of the resistor R11, a terminal 2 of the resistor R11 is connected with a terminal 1 of the resistor R12 and an anode of the diode D4, a terminal 2 of the resistor R12 is connected with the signal ground, and a cathode of the diode D4 is connected with the feedback voltage signal FB.

11. A control method of a PWM constant-current double-feedback laser driving circuit is characterized in that,

the PWM constant-current double-feedback laser driving circuit comprises: the device comprises a switching power supply circuit (1), a PWM control circuit (2), a current feedback drive circuit (3), a laser circuit (4), a voltage feedback control circuit (5) and a voltage conversion circuit (6);

the switching power supply circuit (1) is respectively connected with the voltage feedback control circuit (5), the laser circuit (4) and the voltage conversion circuit (6); the feedback voltage signal FB is used for receiving a feedback voltage signal FB output by the voltage feedback control circuit (5); and outputs a voltage signal VO to the voltage feedback control circuit (5), the laser circuit (4) and the voltage conversion circuit (6);

the current feedback driving circuit (3) is respectively connected with the PWM control circuit (2), the laser circuit (4) and the voltage conversion circuit (6);

the laser circuit (4) is respectively connected with the switching power supply circuit (1), the voltage feedback control circuit (5), the voltage conversion circuit (6) and the current feedback drive circuit (3); the voltage conversion circuit is used for receiving a voltage signal VO output by the switching power supply circuit (1) and outputting a voltage signal VD to the current feedback driving circuit (3) and the voltage conversion circuit (6);

the voltage feedback control circuit (5) is respectively connected with the switching power supply circuit (1), the laser circuit (4) and the voltage conversion circuit (6);

the voltage conversion circuit (6) is respectively connected with the switching power supply circuit (1), the PWM control circuit (2), the current feedback drive circuit (3), the laser circuit (4) and the voltage feedback control circuit (5);

the voltage feedback step further includes: the voltage signal VD and the voltage signal VS output by the current feedback driving circuit (3) output a voltage signal VF through the voltage conversion circuit (6), the voltage signal VO and the voltage signal VF output by the switching power supply circuit (1) output a feedback voltage signal FB through the voltage feedback control circuit (5), and the feedback voltage signal FB controls the process that the switching power supply circuit (1) outputs the voltage signal VO;

the current feedback step further includes: and a sampling resistor R7 in the current feedback driving circuit (3) samples a current signal ID flowing through the laser circuit (4), and then the process of outputting the current ID is controlled by the voltage signal VI through a current series negative feedback circuit or a current parallel negative feedback circuit in the current feedback driving circuit (3).

12. The PWM constant-current dual-feedback laser driving circuit control method according to claim 11, wherein a voltage signal VI of the PWM control circuit (2) is connected to an input of the current feedback driving circuit (3), and the voltage signal PW is connected to an input of the voltage conversion circuit (6).

13. The method for controlling the PWM constant-current dual-feedback laser driving circuit according to claim 11, wherein the PWM control circuit (2) controls the DA converter circuit 1 to output the voltage signal VI1 through the MCU processor, controls the DA converter circuit 2 to output the voltage signal VI2 to be respectively provided to the input terminals of the analog switch U1, the MCU processor outputs the voltage signal PWM1 and the voltage signal PWM2, the voltage signal PWM1 provides the voltage signal PW to the voltage converter circuit (6) through the current limiting resistor R2, the voltage signal PWM2 controls the analog switch U1 through the current limiting resistor R1 to select the voltage signal VI1 and the voltage signal VI2 to output the voltage signal VI, and provides the voltage signal VI to the current feedback driving circuit (3).

14. The method as claimed in claim 13, wherein the DA converter circuit 2 of the PWM control circuit (2) is formed by serially dividing a voltage with a plurality of resistors, one end of the resistor R26 is connected to the reference voltage VCC, one end of the resistor R27 is connected to the signal ground, and the intermediate terminals of the plurality of resistors are connected to the voltage signal VI 2.

15. The control method of the PWM constant-current dual-feedback laser driving circuit according to claim 14, wherein the DA conversion circuit 2 of the PWM control circuit (2) is formed by serially dividing a voltage by a resistor R26 and a resistor R27.

16. The control method of the PWM constant-current dual-feedback laser driving circuit according to claim 11, wherein the current feedback driving circuit (3) adopts a circuit structure of a current series negative feedback topology as follows: the voltage signal VI is connected with a terminal 1 of a resistor R3, and a terminal 2 of a resistor R3 is connected with a non-inverting input end of the operational amplifier U2; the reverse input end of the operational amplifier U2 is connected with the anode of the diode D1, the terminal 1 of the capacitor C1 and the terminal 1 of the resistor R6; the diode D1 and the resistor R4 are connected in series to improve the dynamic characteristic of the operational amplifier U2, the cathode of the diode D1 is connected with the terminal 1 of the resistor R4, and the terminal 2 of the resistor R4 is connected with the output end of the operational amplifier U2.

17. The control method of the PWM constant-current double-feedback laser driving circuit according to claim 11, wherein the current feedback driving circuit (3) adopts a circuit structure of a current parallel negative feedback topology: the voltage signal VI is connected with a terminal 1 of a resistor R3, and a terminal 2 of a resistor R3 is connected with an inverted input end of an operational amplifier U2, an anode of a diode D1, a terminal 1 of a capacitor C1 and a terminal 1 of a resistor R6; the resistors R22 and R23 divide the voltage to provide a reference voltage Vref for the non-inverting input end of the operational amplifier U2, the non-inverting input end of the operational amplifier U2 is connected with the terminal 1 of the resistor R22 and the terminal 1 of the resistor R23, the terminal 2 of the resistor R22 is connected with the reference voltage VCC1, and the resistor R23 is connected with the signal ground.

18. The PWM constant-current dual-feedback laser driving circuit control method according to claim 11, wherein the voltage feedback control circuit (5) inputs a voltage signal VO and a voltage signal VF, and outputs a feedback voltage signal FB; and the voltage feedback control circuit (5) redundantly connects the voltage signal VO output by the switching power supply circuit (1) and the voltage signal VF output by the voltage conversion circuit (6) in parallel and outputs the feedback voltage signal FB to the switching power supply circuit (1) for regulating the output voltage of the switching power supply circuit.

19. The PWM constant-current dual-feedback laser driving circuit control method according to claim 11, wherein in the voltage feedback control circuit (5), the voltage signal VO is connected to the terminal 1 of the resistor R9, the terminal 2 of the resistor R9 is connected to the terminal 1 of the resistor R10 and the anode of the diode D3, the terminal 2 of the resistor R10 is connected to signal ground, and the cathode of the diode D3 is connected to the feedback voltage signal FB; the voltage signal VF is connected with a terminal 1 of the resistor R11, a terminal 2 of the resistor R11 is connected with a terminal 1 of the resistor R12 and an anode of the diode D4, a terminal 2 of the resistor R12 is connected with the signal ground, and a cathode of the diode D4 is connected with the feedback voltage signal FB.

20. The PWM constant-current dual-feedback laser driving circuit control method according to claim 12, wherein the current ID flowing through the laser circuit is a signal that the current feedback driving circuit (3) needs to convert and process; a voltage signal VD at an input end and a voltage signal VS output by the current feedback driving circuit (3) are signals which need to be converted and processed by the voltage conversion circuit (6), the voltage signal VO provides electric energy for the voltage conversion circuit (6), and a voltage signal PW input by the voltage conversion circuit (6) is a conversion control signal; the voltage signal VF output by the voltage conversion circuit (6) is provided for the voltage feedback control circuit (5).