TWI770696B - Switching conversion circuit controlled by the secondary side - Google Patents

Abstract

The invention is a switching conversion circuit controlled by the secondary side, mainly composed of a transformer mode. A switch module, a digital isolation coupling module and a control module are combined, the switch module is electrically connected with the transformer module, the control module is electrically connected with the transformer module and receives the The output voltage of the transformer module, and the digital isolation coupling module is electrically connected between the switch module and the control module, wherein the control module directly passes the digital isolation according to the change of the output voltage and voltage The coupling module sends a control signal to the switch module to regulate the output voltage of the switch conversion circuit, thereby achieving the purpose of improving control accuracy.

Description

Switching conversion circuit controlled by the secondary side

The present invention relates to a switching conversion circuit, especially a switching conversion circuit that can be mastered by the secondary side.

Generally speaking, since electronic devices (smartphones, notebook computers, etc.) cannot directly use terminal power (such as commercial power, the terminal of the power distribution system, etc.) to be charged, it is necessary to convert the terminal power into the electronic device through a power converter. The required power, for example, to convert 110V AC to 5V DC.

In order to effectively control the operation state of the power converter, a signal corresponding to the output voltage is usually required as the feedback signal. In the prior art, the sampling signal of the primary side or the signal generated by the isolation coupling element is often used as the feedback signal.

However, it is impossible to accurately reflect the output voltage state of the secondary side by using the sampling signal of the primary side to simulate the output voltage state of the secondary side. In addition, the isolation coupling element is usually an analog signal (such as an analog voltage signal or a current signal) To drive to generate the aforementioned feedback signal, but the analog signal cannot achieve precise synchronization control.

To sum up, in the prior art, the sampling signal on the primary side or the signal generated by the isolated coupling element driven by the analog signal as the feedback signal cannot achieve precise synchronous control. Therefore, it is indeed necessary to propose a better solution. necessity.

In view of the above-mentioned deficiencies of the prior art, the main purpose of the present invention is to provide a switching conversion circuit controlled by the secondary side, which utilizes digital signals to regulate the output voltage of the switching conversion circuit, thereby improving the control accuracy the goal of.

The main technical means adopted to achieve the above-mentioned purpose is to make the aforementioned switching conversion circuit controlled by the secondary side to include: a transformer module, outputting an output voltage; a switch module, electrically connected with the transformer module; a digital isolation coupling module electrically connected to the switch module; and a control module electrically connected to the transformer module and the digital isolation coupling module for receiving the output voltage, wherein the According to the change of the output voltage, the control module directly sends a control signal to the switch module through the digital isolation coupling module to regulate the output voltage.

With the above structure, the control module can send a control signal to the switch module with a digital signal through the digital isolation coupling module according to the change of the output voltage, so as to regulate the switching conversion circuit according to a load. Output voltage, thereby achieving the purpose of improving control accuracy.

10: Transformer module

11: Transformer

12: Peripheral circuit

13: Output rectifier module

20: Switch module

30: Digital isolation coupling module

40: Control Module

100: Switching conversion circuit

Vi: input voltage

Vcc: power supply voltage

Vo: output voltage

Vsen: sense voltage

T1, T2, Q1, Q2: Transistor

Ta, Tb, Tc: time point

C1: load capacitance

D1: Light Emitting Diode

L1: Primary side winding

L2: Auxiliary winding

LC: logic circuit

Ls: Secondary winding

Cs: digital control signal

G1, G2, PGate, SGate: control signal

PD: Photodiode Module

PGND: Primary side ground terminal

SGND: Secondary side ground terminal

Ss: light sensing signal

Ip: primary side current

Is: Secondary side current

FIG. 1 is a block diagram of a system architecture of an embodiment of the present invention; FIG. 2 is a block diagram of another system architecture of an embodiment of the present invention; and FIG. 3 is a schematic timing diagram of an embodiment of the present invention.

For an embodiment of the switching conversion circuit 100 controlled by the secondary side of the present invention, please refer to FIG. 1 , which includes a transformer module 10 , a switch module 20 , a digital isolation coupling module 30 and A control module 40 .

The switch module 20 is electrically connected to the transformer module 10 , the digital isolation coupling module 30 is electrically connected to the switch module 20 , and the control module 40 is electrically connected to the digital isolation coupling module 30 and is used for receiving the output voltage Vo of the transformer module 10, wherein the control module 40 generates a corresponding digital control signal Cs to the digital isolation coupling module 30 according to the change of the output voltage Vo, so that the digital The isolation coupling module 30 sends a control signal PGate to the switch module 20 according to the received digital control signal Cs, and uses the control signal PGate to regulate the on and off time of the switch module 20, thereby adjusting the output voltage Vo. Thereby, the digital isolation coupling module 30 can instantly send the control signal PGate to the switch module 20 according to the digital control signal Cs, so that the transformer module 10 can be precisely adjusted according to the control of the switch module 20 The output voltage Vo is adjusted according to a load to achieve the purpose of improving the control accuracy.

In one embodiment, the digital control signal Cs may be a PWM (Pulse Width Modulation) control signal, a PDM (Pulse Density Modulation) control signal, or a mixed control signal formed by mixing the PWM control signal and the PDM control signal, Or, for example, in the resonant driving mode, the control signal sometimes controls the output power by modulating the frequency, and the present invention is not limited thereto.

In one embodiment, the switching converter circuit 100 is, for example, a flyback converter, a forward converter or a resonance converter, and this is not the case in the present invention. limit.

In order to further illustrate the switching conversion circuit 100 controlled by the secondary side of the present invention, please refer to FIG. 2 , the transformer module 10 at least includes a transformer 11 , a peripheral circuit 12 and an output rectifier module 13 , and The peripheral circuit 12 is electrically connected to the primary side of the transformer 11 , and the output rectifier module 13 is electrically connected to the secondary side of the transformer 11 .

Further, as shown in FIG. 2 , the transformer 11 includes a primary winding L1 on the primary side, an auxiliary winding L2 , and a secondary winding Ls on the secondary side, wherein the primary winding L1 , the auxiliary winding L2 and the secondary winding Ls are magnetically coupled to each other, and the secondary winding Ls is used to generate a sensing voltage Vsen corresponding to the primary winding L1 and the auxiliary winding L2.

The peripheral circuit 12 is electrically connected to the primary side winding L1 and the auxiliary winding L2. The peripheral circuit 12 may include at least a start up circuit and is used to generate a power supply voltage Vcc, and this is not the case in the present invention limit.

Further, please refer to FIG. 2 , the output rectifier module 13 includes a transistor Q2 and a load capacitor C1 . One end of the transistor Q2 is electrically connected to the other end of the secondary side winding Ls, the other end of the transistor Q2 is electrically connected to a secondary side ground terminal SGND, and the gate terminal of the transistor Q2 is used for receiving A control signal SGate, wherein the transistor Q2 determines whether to make one end and the other end of the transistor to conduct with each other according to the control signal SGate. In this embodiment, the transistor Q2 is used as a synchronous rectifier switch to replace a rectifier diode, such as a Schottky diode with low forward voltage and fast recovery characteristics. The invention is not limited by this. Two ends of the load capacitor C1 are individually electrically connected to one end of the secondary side winding Ls and the secondary side ground terminal SGND, thereby providing the output voltage Vo to a load and reducing the ripple of the output voltage Vo Wave.

Further, please refer to FIG. 2, the switch module 20 includes a transistor Q1, one end of the transistor Q1 is electrically connected to the other end of the primary side winding L1, and the other end of the transistor Q1 is electrically connected It is electrically connected to the primary side ground terminal PGND, and the gate terminal of the transistor Q1 is used to receive the control signal PGate, wherein the transistor Q1 determines whether one end and the other end of the transistor Q1 are connected to each other according to the control signal PGate. Thereby, the switch module 20 can control the time and frequency of the output power of the transformer 11 , thereby controlling and adjusting the output voltage Vo.

In one embodiment, the transistor Q1 and the transistor Q2 can be implemented by a bipolar transistor, a field effect transistor, an insulated gate bipolar transistor (IGBT), etc., and the present The invention is not limited by this.

Further, please refer to FIG. 2, in this embodiment, the digital isolation coupling module 30 is realized by a digital optical coupling module, which includes a light emitting diode D1, a photodiode module PD, A logic circuit LC, a transistor T1 and a transistor T2.

One end of the light-emitting diode D1 is connected to a power source on the secondary side (such as the secondary side ground terminal SGND), and the other end of the light-emitting diode D1 is used to receive the digital control signal Cs output by the control module 40 Therefore, the light-emitting diode D1 can emit light (ie, the light signal corresponding to the binary signal) according to the voltage difference between a power supply on the secondary side and the digital control signal Cs (ie, the binary signal).

The photodiode module PD is electrically connected to the logic circuit LC, which is used to sense the light of the light emitting diode D1 and generate a corresponding light sensing signal Ss, and transmit the light sensing signal Ss to the Logic circuit LC, thereby achieving isolation between the photodiode module PD and the light emitting diode D1 (ie, no conductor (resistivity <0.01ohm-m) connection, insulated from each other (leakage current <10mA) ), the effect of high voltage resistance (collapse voltage>40V)) coupling (signal transmission).

The logic circuit LC is electrically connected with the photodiode module PD, the transistor T1 and the transistor T2, and the logic circuit LC is used for receiving the light sensing signal Ss, and according to the light sensing signal Ss A first control signal G1 and a second control signal G2 for controlling the transistor T1 and the transistor T2 are generated.

In one embodiment, when the switching conversion circuit 100 is just powered on, the logic circuit LC has not yet received the light sensing signal Ss, and the logic circuit LC is used to automatically generate the first control signal G1 and the second control signal G1. Control signal G2.

In one embodiment, when the switching conversion circuit 100 is just powered on, the logic circuit LC has not yet received the light sensing signal Ss, and the logic circuit LC can generate the first signal according to an external signal (not shown). The control signal G1 and the second control signal G2.

In one embodiment, the logic circuit LC determines whether to restart according to the light sensing signal Ss. Further, the logic circuit LC judges whether the light sensing signal Ss is interrupted (for example, when the switching conversion circuit 100 has been powered on for a period of time, the logic circuit LC judges that the light sensing signal is not received) When the time of Ss exceeds 0.1 second, the logic circuit LC judges that the light sensing signal Ss has been interrupted). When the logic circuit LC judges that the light sensing signal Ss has been interrupted, it restarts the machine.

One end of the transistor T1 receives a power supply voltage Vcc, the other end of the transistor T1 is used to output the control signal PGate, and the gate terminal of the transistor T1 is used to receive the first control signal G1, wherein the transistor T1 According to the first control signal G1, it is determined whether to make one end and the other end conduct with each other.

One end of the transistor T2 is electrically connected to the other end of the transistor T1, the other end of the transistor T2 is electrically connected to the primary side ground terminal PGND, and the gate terminal of the transistor T2 is used to receive the second control The signal G2, wherein the transistor T2 determines whether to make one end and the other end of the transistor to conduct with each other according to the first control signal G1.

In this embodiment, the transistor T1 and the transistor T2 can be implemented by one of an N-type transistor and a P-type transistor. For example, the transistor T1 can be a P-type transistor, and the transistor T2 can be an N-type transistor, and the present invention is not limited thereto.

In one embodiment, the transistor T1 is implemented by one of an N-type transistor and a P-type transistor, and when the transistor T2 is implemented by the other of an N-type transistor and a P-type transistor, The first control signal G1 and the second control signal G2 may be substantially the same.

Thereby, the logic circuit LC can control the on or off of the transistor T1 and the transistor T2 by the first control signal G1 and the second control signal G2 to generate the control signal PGate.

Further, please refer to FIG. 2 , the control module 40 is used for receiving the output voltage Vo and the sensing voltage Vsen, and generating the control signal SGate for controlling the transistor Q2 and controlling the light-emitting diode accordingly The digital control signal Cs of D1.

In one embodiment, the control module 40 can be a PWM control module, and the present invention is not limited thereto.

Further, the operation of the power conversion circuit 100 controlled by the secondary side will be described below with reference to the schematic diagram of the timing sequence in FIG. 3 .

Please refer to FIG. 2 and FIG. 3 at the same time. First, taking the flyback type as an example, at the time point Ta, on the primary side of the transformer 11 , the digital control signal Cs changes from the enable voltage level to the disable voltage level (high voltage level). The voltage level is changed to a low voltage level), and at the same time, the control signal PGate that controls the transistor Q1 is changed from an enable voltage level to a disable voltage level (the high voltage level is changed to a low voltage level). When the transistor Q1 is turned off, on the secondary side of the transformer 11, the sensing voltage Vsen is lower than a reference voltage, so the control signal SGate of the transistor Q2 changes from the disable voltage level to the enable voltage level (low voltage level to high voltage level bit), turn on the transistor Q2, form a loop between the two ends of the secondary side winding Ls, generate a secondary side current Is, and start charging the load capacitor C1.

From the time point Ta to the time point Tb, the secondary side current Is decreases with time in a substantially linear manner, and the sensing voltage Vsen increases with the decrease of the secondary side current Is. At time point Tb, the secondary side current Is stops.

At the time point Tc, the sensing voltage Vsen reaches the peak (high voltage level), and the control module 40 detects the time point (the instant point Tc) of the returning point of the sensing voltage Vsen, and at this point makes the digital The control signal Cs changes from the disable voltage level to the enable voltage level (low voltage level to high voltage level), and controls the control signal PGate from the disable voltage level to the enable voltage level (low voltage level to high voltage level). The voltage level is changed to high voltage level), the transistor Q1 is turned on, and a primary side current Ip is generated. On the secondary side of the transformer 11, the control signal SGate is kept at the disable voltage level (low voltage level) ), the transistor Q2 is turned off, and the misoperation of the transistor Q2 is avoided by the control signal SGate of the disable voltage level, wherein, in this embodiment, the semi-resonant mode (QR mode) It operates in the manner of , and basically turns on the transistor Q1 by detecting the time point of the turning-back point of the coil voltage on the transformer 11 (ie, the sensing voltage Vsen). Here, a voltage conversion process is completed.

In one embodiment, the reference voltage is, for example, -50 mV, and the present invention is not limited thereto.

To sum up, in the present invention, the digital control signal Cs generated by the control module 40 is matched with the digital isolation coupling module 30 driven by the digital signal, so that the control signal PGate can be based on the digital control signal Cs The synchronous conversion of voltage levels is used to control the transistor Q1, so that the transformer module 10 can accurately adjust the output voltage Vo, so as to improve the control accuracy.

10: Transformer module

20: Switch module

30: Digital isolation coupling module

40: Control Module

100: Switching conversion circuit

Vo: output voltage

Cs: digital control signal

PGate: control signal

Claims (12)

A switching conversion circuit controlled by a secondary side, comprising: a transformer module for outputting an output voltage; a switch module electrically connected with the transformer module; a digital isolation coupling module, Electrically connected with the switch module, the digital isolation coupling module includes: a logic circuit for automatically generating a first control signal and a second control signal; and a control module, connected to the transformer module and the digital isolation coupling module is electrically connected to receive the output voltage, wherein the control module directly sends a control signal to the switch module through the digital isolation coupling module according to the change of the output voltage , to regulate the output voltage. The switching conversion circuit of claim 1, wherein the control module receives the output voltage and the sensed voltage of the secondary side of the transformer module, and generates a digital control signal accordingly. The switching conversion circuit of claim 2, wherein the digital control signal includes a PWM control signal and a PDM control signal. The switching conversion circuit of claim 2, wherein the control signal is synchronized with the digital control signal. The switching conversion circuit of claim 2, wherein the control signal is synchronized with the sensing voltage. The switching conversion circuit according to claim 2, wherein the digital isolation coupling module is a digital optical coupling module. The switching conversion circuit of claim 6, wherein the digital isolation coupling module comprises: a light emitting diode electrically connected to the control module for receiving the digital control signal; a photodiode a module, which is optically coupled with the light-emitting diode, and generates a photo-sensing signal; wherein the logic circuit is electrically connected to the photo-diode module, receives the photo-sensing signal, and generates the first control signal and the second control signal; a first transistor, one end of which is used to receive a power supply voltage, and its gate terminal is electrically connected to the logic circuit to receive the first control signal, the first transistor according to the first The control signal determines whether to turn on or off; and a second transistor, one end of which is electrically connected to the other end of the first transistor and used to output the control signal, and the gate terminal of the second transistor is electrically connected to the logic circuit , for receiving the second control signal, and the second transistor is turned on or off according to the second control signal. The switching conversion circuit of claim 7, wherein the logic circuit further generates the first control signal and the second control signal according to an external signal. The switching conversion circuit as claimed in claim 7, wherein the logic circuit is used for determining whether to restart according to the state of the light sensing signal. The switching conversion circuit as claimed in claim 1, wherein the switch module comprises a transistor, one end of the transistor is electrically connected to the primary side of the transformer module, and the gate terminal of the transistor is connected to the digital type The isolation coupling module is electrically connected to receive the control signal, and the other end of the transistor is electrically connected to the ground terminal of the primary side of the transformer module. The switching conversion circuit of claim 10, wherein the transistor is a bipolar transistor, a field effect transistor or an insulated gate bipolar transistor. The switching conversion circuit of claim 1, wherein the switching conversion circuit comprises a load capacitor electrically connected to the transformer module.

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