CN104053288A - Adaptive power supply non-isolated step-down LED drive circuit and working method - Google Patents

Abstract

The invention relates to a non-isolation step-down LED drive circuit capable of adaptive power supply and a working method. The non-isolation step-down LED drive circuit comprises a rectification filter circuit and a control module, wherein the power supply end of the control module is connected with the output end of the rectification circuit through a resistor. An adaptive power supply circuit is arranged in the control module. The adaptive power supply circuit comprises a microprocessor unit, a step-down unit, a plurality of Pn junctions connected in series and an analog switch unit. The output end of the step-down unit is connected with the input ends of the Pn junctions in series, and the output end of the step-down unit serves as the voltage output end of the adaptive power supply circuit. Nodes are arranged among the Pn junctions, the nodes are connected with the switch input ends of the analog switch unit respectively, and the switch output ends of the analog switch unit are connected with one another and connected to the ground through a resistor. The power supply end of the processor unit obtains sampling voltage, and the control output ends of the processor unit are respectively connected with the control end of the analog switch unit.

Description

Adaptive power supply non-isolated step-down LED drive circuit and working method

technical field

The invention relates to an LED drive circuit, in particular to a self-adaptive power supply non-isolated step-down LED drive circuit and a working method.

Background technique

With the continuous improvement of LED (Light-Emitting Diode) technology, LED as a lighting source has shown the characteristics of high light efficiency, long life, fast response and environmental protection, and has begun to replace traditional light sources in many lighting fields. Although the power capacity of a single LED has reached 10W, the lighting scheme using a single LED still cannot meet the requirements for lighting occasions that require large areas and high illuminance. In order to solve this problem, the LEDs are often connected in parallel, series and mixed, and the LEDs are driven by a non-isolated step-down LED drive circuit. The power supply end of the traditional non-isolated step-down LED drive circuit is generally connected to the The energy storage unit is connected to collect the output voltage of the energy storage unit.

Contents of the invention

The purpose of the present invention is to provide a self-adaptive power supply non-isolated step-down LED drive circuit, the power supply part of the LED drive circuit is more optimized to adapt to peripheral voltage fluctuations and protect components.

In order to solve the above technical problems, the present invention provides a self-adaptive power supply non-isolated step-down LED drive circuit, including: a rectifier filter circuit, a control module with a switch tube, the power supply terminal of the control module is connected to the rectifier through a resistor The output terminals of the circuit are connected; the control module is provided with an adaptive power supply circuit, the adaptive power supply circuit includes a microprocessor unit, and the first and second resistors are connected in series to form a step-down unit, which is composed of several series-connected PN junctions A PN junction unit, an analog switch unit; the output end of the step-down unit is connected to the input end of the PN junction unit, and the output end is used as the voltage output end of the adaptive power supply circuit; There are nodes, each node is respectively connected to each switch input end of the analog switch unit, each switch output end of the analog switch unit is connected, and grounded through a resistor; the processor unit obtains a sampling voltage from the power supply end, The control output terminals of the processor unit are respectively connected to the control terminals of the analog switch unit, that is, the analog switch unit is controlled to open or close the corresponding switch according to the sampled voltage value, so as to increase or decrease the PN junction in series and stabilize The output voltage of the adaptive power supply circuit.

In order to better optimize the circuit and simplify the components and parts, one end of the switching tube in the control module is connected to the input end of the energy storage unit as a voltage output end, and the current sampling end of the control module is obtained from the freewheeling tube in the energy storage unit The cathode of the cathode obtains a current sampling signal, and controls the disconnection, conduction or maintenance of the switching tube by judging the magnitude of the current sampling signal.

Further, the control module further includes: a comparison unit, which includes: a sampling resistor suitable for converting the current sampling signal into a voltage sampling signal, one end of the sampling resistor is connected to the current sampling end, and the other end is grounded, One end of the sampling resistor is also connected to the hysteresis voltage comparison subunit, which is suitable for inputting the voltage sampling signal through its non-inverting terminal, and the output terminal of the hysteresis voltage comparison subunit is passed through an inverter The phaser is connected to the control terminal of the switch tube, and the hysteresis voltage comparison subunit is adapted to control the switching off, on or holding of the switch tube according to the change of the sampling voltage.

Further, the hysteresis voltage comparison subunit includes: a comparator, the inverting terminal of the comparator inputs a reference voltage, the voltage sampling signal is connected to the non-inverting terminal of the comparator through an input resistance, and the non-inverting terminal is also connected to a feedback One end of the resistor is connected, the output end of the comparator is connected with one end of an output resistor, the output end of the comparator is also connected with the other end of the feedback resistor, and the other end of the output resistor is used as the hysteresis The output terminal of the voltage comparison subunit.

In order to solve the above technical problems, on the basis of the above technical solutions, the present invention also provides a working method of a self-adaptive power supply non-isolated step-down LED drive circuit, including: the processor unit is adapted to The voltage value controls the analog switch unit to open or close the corresponding switch to increase or decrease the PN junction in series and stabilize the output voltage of the adaptive power supply circuit; that is, when the sampling voltage value increases, the PN junction in series is reduced. PN junction; if the sampling voltage value drops, then add a PN junction in series.

Further, the current sampling terminal of the control module obtains a current sampling signal from the cathode of the freewheeling tube in the energy storage unit, and controls the disconnection, conduction or maintenance of the switching tube by judging the magnitude of the current sampling signal.

Further, the control module further includes: a comparison unit, the comparison unit includes: a sampling resistor adapted to convert the current sampling signal into a voltage sampling signal, and suitable for controlling the disconnection of the switch tube according to the change of the voltage sampling signal, The hysteresis voltage comparison subunit that is turned on or maintained; the hysteresis voltage comparison subunit inputs the voltage sampling signal through its non-inverting terminal, and the output terminal of the hysteresis voltage comparison subunit is connected to the said hysteresis voltage comparison subunit through an inverter. The control terminals of the switch tubes are connected.

Further, the hysteresis voltage comparison subunit includes: a comparator, the inverting terminal of the comparator inputs a reference voltage, the voltage sampling signal is connected to the non-inverting terminal of the comparator through an input resistance, and the non-inverting terminal is also connected to a feedback One end of the resistor is connected, the output end of the comparator is connected with one end of an output resistor, the output end of the comparator is also connected with the other end of the feedback resistor, and the other end of the output resistor is used as the hysteresis The output terminal of the voltage comparison subunit; set the positive threshold voltage and the negative threshold voltage of the hysteresis voltage comparison subunit; that is, when the voltage sampling signal starts to rise from the negative threshold voltage, the hysteresis The voltage comparison subunit outputs a low level to control the switch to turn on, and when the voltage sampling signal exceeds the forward threshold voltage value, the hysteresis voltage comparison subunit outputs a high level to control the switch to turn off; or, the When the voltage sampling signal starts to drop from the positive threshold voltage, the hysteresis voltage comparison subunit outputs a high level to control the switching tube to turn off. When the voltage sampling signal is equal to the negative threshold voltage value, the hysteresis voltage comparison subunit The subunit outputs a low level to control the switching tube to conduct.

The technical scheme of the present invention has the following advantages compared with the prior art: (1) the present invention cooperates to form an adaptive power supply circuit by a microprocessor unit, some PN junctions connected in series, and an analog switch unit, and this power supply circuit makes the control module acceptable The power supply voltage range is larger, and when the control module forms a non-isolated step-down LED drive circuit, there is no need to consider the input power supply voltage too much, and the circuit is greatly optimized, saving components; (2 ) through the hysteresis voltage comparison subunit to realize the control of the switching tube through the positive threshold voltage and the negative threshold voltage, and realize the charging and discharging of the subsequent energy storage unit; (3) through the hysteresis voltage comparison subunit to make the control module The structure is simplified, and the on-off control of the switch tube can also be realized without the internal pulse control unit.

Description of drawings

In order to make the content of the present invention more easily understood, the present invention will be described in further detail below in conjunction with the specific embodiments according to the accompanying drawings, wherein

Figure 1 is a schematic block diagram 1 of a non-isolated step-down LED drive circuit;

Fig. 2 is a circuit schematic diagram of an adaptive power supply circuit;

Fig. 3 is the circuit schematic diagram 2 of the non-isolated step-down LED driving circuit;

Fig. 4 is the circuit schematic diagram of comparison unit;

FIG. 5 is a waveform diagram of a hysteresis voltage comparison subunit.

Among them, the first resistor R1, the second resistor R2, the third resistor R3, the fourth resistor R4, the current sampling signal I _CS , the voltage sampling signal U _CS , the sampling resistor R11, the comparator A1, the reference voltage U _R , the input resistor R8 , feedback resistor R9, output resistor R10, sampling resistor R11, bidirectional regulator Z, positive threshold voltage U _TH1 , negative threshold voltage U _TH2 , freewheeling tube VD.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in combination with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are exemplary only, and are not intended to limit the scope of the present invention. Also, in the following description, descriptions of well-known structures and techniques are omitted to avoid unnecessarily obscuring the concept of the present invention.

Example 1

As shown in Figure 1 and Figure 2, a non-isolated step-down LED drive circuit for self-adaptive power supply, including: a rectifier filter circuit, a control module with a switch tube, the power supply terminal of the control module is connected to the rectifier through a resistor R The output terminals of the circuit are connected; the control module is provided with an adaptive power supply circuit, the adaptive power supply circuit includes a microprocessor unit, and the first and second resistors are connected in series to form a step-down unit, which is composed of several series-connected PN junctions A PN junction unit, an analog switch unit; the output end of the step-down unit is connected to the input end of the PN junction unit, and the output end is used as the voltage output end of the adaptive power supply circuit; between the PN junctions Nodes are provided, each node is connected to each switch input terminal of the analog switch unit, each switch output terminal of the analog switch unit is connected, and grounded through a resistor R6; the power supply terminal of the processor unit obtains a sampling voltage , the control output terminals of the processor unit are respectively connected to the control terminals of the analog switch unit, that is, the analog switch unit is controlled to open or close corresponding switches according to the sampled voltage value, so as to increase or decrease the PN junction in series, and stabilizing the output voltage of the adaptive power supply circuit.

The microprocessor unit obtains the sampling voltage through a voltage divider circuit formed by the third resistor R3 and the fourth resistor R4.

Wherein, the PN junction can be realized by using a diode, such as a silicon tube or a germanium tube.

The function of the self-adaptive power supply circuit is to provide the power supply voltage for the remaining circuits in the control module, and for the self-adaptive power supply circuit to adopt another independent power supply circuit, it can be realized by a voltage stabilizing circuit; by adopting the self-adaptive power supply Two sets of power supply circuits, the self-adaptive power supply circuit and the independent power supply circuit, can effectively reduce the failure rate of the control module, and the adjustment range of the voltage of the self-adaptive power supply circuit is larger than that of the independent power supply circuit, which is more conducive to the control of the rest of the module. Stable power supply of the circuit.

The switch in the analog switch unit is realized through the internal mos tube.

As shown in Figure 3, one end of the switching tube of the control module is connected to the input end of the energy storage unit as a voltage output end, and the current sampling end of the control module obtains current sampling from the cathode of the freewheeling tube VD in the energy storage unit The signal I _CS controls the disconnection, conduction or maintenance of the switching tube by judging the magnitude of the current sampling signal I _CS .

The shown control module also includes: a comparison unit, which includes: a sampling resistor R11 suitable for converting the current sampling signal I _CS into a voltage sampling signal U _CS , one end of the sampling resistor R11 is connected to the current sampling end, and The other end is grounded; one end of the sampling resistor R11 is also connected to the hysteresis voltage comparison subunit, which is suitable for inputting the voltage sampling signal U _CS through its non-inverting terminal, and the hysteresis voltage comparison subunit The output terminal of the unit is connected with the control terminal of the switching tube through an inverter, and the hysteresis voltage comparison subunit is suitable for controlling the switching off, conducting or holding of the switching tube according to the variation of the sampling voltage.

The hysteresis voltage comparison subunit includes: a comparator A1, the inverting terminal of the comparator A1 inputs a reference voltage _UR , the voltage sampling signal U _CS is connected to the non-inverting terminal of the comparator A1 through an input resistance, the non-inverting terminal end is also connected with one end of a feedback resistor R9, the output end of the comparator A1 is connected with one end of an output resistor R10, the output end of the comparator A1 is also connected with the other end of the feedback resistor R9, the The other end of the output resistor R10 is used as the output end of the hysteresis voltage comparison subunit.

Example 2

On the basis of Embodiment 1, the present invention also provides a working method of a self-adaptive power supply non-isolated step-down LED drive circuit, including: the processor unit is adapted to control the analog switch unit according to the sampled voltage value Open or close the corresponding switch to increase or decrease the PN junction in series to stabilize the output voltage of the adaptive power supply circuit; that is, when the sampling voltage value increases, reduce the PN junction in series; if the sampling When the voltage value drops, the PN junction in series is added.

The current sampling terminal of the control module obtains the current sampling signal I _CS from the cathode of the freewheeling tube VD in the energy storage unit, and controls the disconnection, conduction or maintenance of the switching tube by judging the magnitude of the current sampling signal I _CS .

The control module includes: a sampling resistor suitable for converting the current sampling signal I _CS into a voltage sampling signal U, and a hysteresis suitable for controlling the disconnection, conduction or maintenance of the switch tube according to the change of the voltage sampling signal U _CS A return voltage comparison subunit; the hysteresis voltage comparison subunit inputs the voltage sampling signal through its non-inverting terminal, and the output terminal of the hysteresis voltage comparison subunit is connected to the control terminal of the switch tube through an inverter .

As shown in Figure 4, the hysteresis voltage comparison subunit includes: a comparator A1, the inverting terminal of the comparator A1 inputs a reference voltage _UR , and the voltage sampling signal U _CS is connected to the comparator through an input resistor R8 The non-inverting terminal of A1, the non-inverting terminal is also connected to one end of a feedback resistor R9, the output terminal of the comparator A1 is connected to one end of an output resistor R10, and the output terminal of the comparator A1 is also connected to the feedback resistor R9 The other end of the output resistor R10 is used as the output end of the hysteresis voltage comparison subunit; the negative threshold voltage U _TH2 and the positive threshold voltage U _TH1 of the hysteresis voltage comparison subunit are set .

That is, when the voltage sampling signal U _CS rises from the negative threshold voltage U _TH2 , the hysteresis voltage comparison subunit outputs a low level to control the switching tube to be turned on. When the voltage sampling signal U _CS exceeds the positive When reaching the threshold voltage value, the hysteresis voltage comparison subunit outputs a high level, and the control switch tube is turned off;

Or, when the voltage sampling signal U _CS starts to drop from the positive threshold voltage U _TH1 , the hysteresis voltage comparison subunit outputs a high level to control the switch to turn off. When the voltage sampling signal U CS is equal to the negative threshold voltage value, the hysteresis voltage comparison subunit outputs a low level to control the switch tube to be turned on.

Forward Threshold Voltage $u_{\mathrm{TH}1}=(1+\frac{R8}{R9})u_R+\frac{R8}{R9}{u}_{\mathrm{OL}}$

Negative Going Threshold Voltage $u_{\mathrm{TH}2}=(1+\frac{R8}{R9})u_R-\frac{R8}{R9}{u}_{\mathrm{Oh}}$

Set U _OL to 0, and set an appropriate reference voltage _UR to obtain positive threshold voltage U _TH1 and negative threshold voltage U _TH2 , as shown in Figure 5.

Wherein, if the switch tube is a triode, the control terminal is a base, and if the switch tube is a MOS tube, the control terminal is a G pole.

It should be understood that the above specific embodiments of the present invention are only used to illustrate or explain the principle of the present invention, and not to limit the present invention. Therefore, any modification, equivalent replacement, improvement, etc. made without departing from the spirit and scope of the present invention shall fall within the protection scope of the present invention. Furthermore, it is intended that the appended claims of the present invention embrace all changes and modifications that come within the scope and metesques of the appended claims, or equivalents of such scope and metes and bounds.

Claims (8)

1. A non-isolated step-down LED drive circuit for adaptive power supply, characterized in that it comprises: a rectification filter circuit, a control module provided with a switching tube, the power supply terminal of the control module is connected to the output terminal of the rectification circuit through a resistor ; An adaptive power supply circuit is provided in the control module, the adaptive power supply circuit includes a microprocessor unit, a step-down unit is composed of first and second resistors connected in series, and a PN junction unit composed of several series connected PN junctions simulates A switch unit; the output terminal of the step-down unit is connected to the input terminal of the PN junction unit, and the output terminal is used as the voltage output terminal of the adaptive power supply circuit; Nodes are provided between the PN junctions, each node is connected to each switch input end of the analog switch unit, each switch output end of the analog switch unit is connected, and grounded through a resistor; The processor unit obtains a sampling voltage from the power supply terminal, and the control output terminals of the processor unit are respectively connected to the control terminals of the analog switch unit, that is, control the analog switch unit to open or close according to the sampling voltage value. Closing the corresponding switch to increase or decrease the number of PN junctions connected in series to stabilize the output voltage of the self-adaptive power supply circuit. 2. The non-isolated step-down LED drive circuit according to claim 1, wherein one end of the switch tube in the control module is connected to the input end of the energy storage unit as a voltage output end, and the output end of the control module is The current sampling terminal obtains a current sampling signal from the cathode of the freewheeling tube in the energy storage unit, and controls the disconnection, conduction or maintenance of the switching tube by judging the magnitude of the current sampling signal. 3. The non-isolated step-down LED drive circuit according to claim 2, wherein the control module further comprises: a comparison unit, which comprises: a sampling unit suitable for converting the current sampling signal into a voltage sampling signal A resistor, one end of the sampling resistor is connected to the current sampling terminal, the other end is grounded, and one end of the sampling resistor is also connected to the hysteresis voltage comparison subunit; The hysteresis voltage comparison subunit is suitable for inputting the voltage sampling signal through its non-inverting terminal, the output terminal of the hysteresis voltage comparison subunit is connected to the control terminal of the switching tube through an inverter, and the hysteresis voltage The comparison subunit is adapted to control the switching off, on or holding of the switching tube according to the sampling voltage. 4. The non-isolated step-down LED drive circuit according to claim 3, wherein the hysteresis voltage comparison subunit comprises: a comparator, an inverting terminal of the comparator inputs a reference voltage, and the voltage The sampling signal is connected to the non-inverting terminal of the comparator through the input resistor, and the non-inverting terminal is also connected to one end of a feedback resistor, and the output terminal of the comparator is connected to one end of an output resistor, and the output terminal of the comparator is also connected to the The other end of the feedback resistor is connected, and the other end of the output resistor is used as the output end of the hysteresis voltage comparison subunit. 5. A working method of the self-adaptive power supply non-isolated step-down LED driver circuit according to claim 1, characterized in that it comprises: the processor unit is adapted to control the analog switch according to the sampled voltage value The unit opens or closes the corresponding switch to increase or decrease the PN junction in series to stabilize the output voltage of the adaptive power supply circuit; That is, when the sampling voltage value increases, the PN junctions connected in series are reduced; when the sampling voltage value decreases, the PN junctions connected in series are increased. 6. A working method of the non-isolated step-down LED drive circuit according to claim 5, wherein one end of the switching tube in the control module is connected to the input end of the energy storage unit as a voltage output end, The current sampling terminal of the control module obtains a current sampling signal from the cathode of the freewheeling tube in the energy storage unit, and controls the disconnection, conduction or maintenance of the switching tube by judging the magnitude of the current sampling signal. 7. The working method of the non-isolated step-down LED drive circuit according to claim 6, wherein the control module further comprises: a comparison unit, the comparison unit includes: A sampling resistor for the signal, and a hysteresis voltage comparison subunit suitable for controlling the disconnection, conduction or maintenance of the switch tube according to the change of the voltage sampling signal; The hysteresis voltage comparison subunit inputs the voltage sampling signal through its non-inverting terminal, and the output terminal of the hysteresis voltage comparison subunit is connected to the control terminal of the switch tube through an inverter. 8. The working method of the non-isolated step-down LED drive circuit according to claim 7, wherein the hysteresis voltage comparison subunit comprises: a comparator, the inverting terminal of the comparator inputs a reference voltage, The voltage sampling signal is connected to the non-inverting terminal of the comparator through the input resistor, the non-inverting terminal is also connected to one end of a feedback resistor, the output terminal of the comparator is connected to one end of an output resistor, and the output terminal of the comparator Also connected to the other end of the feedback resistor, the other end of the output resistor is used as the output end of the hysteresis voltage comparison subunit; Setting the positive threshold voltage and negative threshold voltage of the hysteresis voltage comparison subunit; That is, when the voltage sampling signal starts to rise from the negative threshold voltage, the hysteresis voltage comparison subunit outputs a low level to control the switch to conduct, and when the voltage sampling signal exceeds the positive threshold voltage value, The hysteresis voltage comparison subunit outputs a high level to control the switching tube to be turned off; Or, when the voltage sampling signal starts to drop from the positive threshold voltage, the hysteresis voltage comparison subunit outputs a high level to control the switching tube to turn off, and when the voltage sampling signal is equal to the negative threshold voltage value, the The hysteresis voltage comparison subunit outputs a low level to control the switching tube to be turned on.