CN114726217A - MOS drive circuit of switching power supply - Google Patents

Abstract

The invention discloses a MOS drive circuit of a switching power supply. The switching power supply includes a transformer component, a first resistor, a power switch tube and a control unit for driving the power switch tube. The control unit includes a drive module for outputting corresponding One end of the drive circuit is connected to the drive module, and the other end is connected to the first resistor; the drive circuit includes a power tube temperature detection module for detecting the temperature of the power switch tube; a The voltage control module is used to provide different gate voltages according to the power tube temperature. The present invention can effectively reduce system loss and improve system efficiency by adding a temperature detection module and a voltage control module.

Description

MOS drive circuit of switching power supply

technical field

The invention relates to the design of power products, in particular to a MOS drive circuit of a switching power supply.

Background technique

Switching power supplies have the advantages of small size, high efficiency and large current, so they are widely used in mobile phone chargers and notebook computer adapters. FIG. 1 is a circuit schematic diagram of a switching power supply in the prior art. The control modulator 115 is connected to the primary coil 104 of the transformer through the power switch tube 108 . The control modulator 115 controls the power switch tube 108 to be turned on in each switching cycle, and transmits the energy of the primary coil 103 of the transformer to the output of the secondary coil 105 . The modulator 115 is controlled to obtain a stable output voltage on the secondary winding 105 through the switching period or switching frequency of the power switch tube 108 .

As shown in FIG. 1 , the operating losses of the flyback power supply mainly include: conduction loss of the MOS switch 108 , driving loss of the switch 108 , switching overlap loss of the switch 108 , output rectifier loss, clamping Protection circuit loss, feedback circuit loss, etc. The internal resistance temperature characteristic of the switch tube 108 is that the internal resistance also increases with the increase of temperature, and decreases with the increase of the gate driving voltage. In the case of a fixed gate voltage, as the temperature increases, the internal resistance will increase and the efficiency will decrease during operation. Therefore, when the output power is constant, if the internal resistance of the switch tube 108 can be optimized, the system efficiency can be improved.

In the green era where environmental awareness is increasingly valued, the effective use of limited energy has become a consensus. European and American countries have defined clear specifications for the efficiency of electrical products. Since July 2001, the United States has stipulated that government agencies shall not purchase electrical products whose efficiency does not meet the standard. It can be seen that improving the overall efficiency of switching power converters has become a basic requirement, which is also a challenge that power supply design engineers must face.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a MOS driving circuit of a switching power supply. The switching power supply of the driving circuit can reduce the loss and improve the system efficiency.

In order to solve the above problems, the MOS drive circuit of the switching power supply according to the present invention includes:

an input capacitor Cin, the input capacitor is connected across the positive and negative input terminals of the power supply;

The first resistor 201, the first end of the first resistor 201 is connected to the positive input end of the power supply, the second end is connected to one end of the first capacitor C1, and the other end of the first capacitor C1 is grounded;

The cathode of the first diode 202 is connected to the second section of the first resistor 201, the anode of the first diode 202 is connected to one end of the second primary coil 204 of the transformer, and the other end of the second primary coil 204 is grounded ;

The same name terminal of the first primary coil 203 of the transformer is connected to the positive input terminal of the power supply;

The same-named end of the secondary coil 205 of the transformer is the first output end of the switching power supply, the synonymous end of the secondary coil 205 is connected to the positive pole of the second diode 206, and the negative pole of the second diode 206 is the the second output terminal of the switching power supply;

The second capacitor C2 and the second resistor 207 are connected in parallel between the first and second output terminals of the switching power supply;

The drain of the power tube 208 is connected to the opposite end of the first primary coil 203 of the transformer, and the source of the power tube 208 is grounded through the third resistor 209;

a power tube temperature detection module 216, the power tube temperature detection module 216 is connected to the voltage control module 217, and provides the voltage control module 217 with a signal voltage Vt;

An output end of a turn-off comparator 214 is connected to the R input end of a flip-flop 213, an input end of the turn-off comparator 214 is connected to the first reference voltage Vref1, and the other input end is connected to the third resistor 209;

After the fourth resistor 210 is connected in series with the fifth resistor 211, the other end of the fifth resistor 211 is grounded, and the other end of the fourth resistor 210 is connected to the positive electrode of the first diode 202;

The S input terminal of the flip-flop 213 is connected to the series node of the fourth resistor 210 and the fifth resistor 211;

a driving module 212, the output end of the driving module 212 is connected to the gate of the power tube 208, and provides a driving voltage to control the turn-on or turn-off of the power tube 208;

The same-direction output terminal of the flip-flop 213 is connected to the driving module 212 , and the output terminal of the voltage control module 217 is connected to the driving module 212 .

A further improvement is that the power MOS transistor 208 is an NMOS.

A further improvement is that the power tube temperature detection module 216 includes: a zero temperature constant current source and a sixth resistor 219, the zero temperature constant current source outputs a constant current to the first end of the sixth resistor 219, and the sixth resistor 219 The second terminal is grounded, and the first terminal of the sixth resistor 219 outputs the signal voltage Vt.

A further improvement is that the sixth resistor 219 is a resistor with a temperature coefficient, including a positive temperature coefficient or a negative temperature coefficient; when the sixth resistor 219 is a resistor with a positive temperature coefficient, as the temperature increases, the signal voltage increases. Vt increases accordingly.

A further improvement is that the voltage control module 217 includes: a first comparator 401, a second comparator 402, an inverter 403, an AND gate 404, a NOR gate 405, a first switch 406, a second switch 407, The third switch 408; the positive input terminals of the first comparator 401 and the second comparator 402 are connected in parallel with the signal voltage Vt, the negative input terminal of the first comparator 401 is connected to the second reference voltage Vref2, and the first comparator 401 is connected to the second reference voltage Vref2. The negative input terminals of the two comparators 402 are connected to the third reference voltage Vref3;

The output terminal of the first comparator 401 is connected to the gate of the first switch 406, and the drain of the first switch 406 is connected to the power supply Vcc1.

The output terminal of the first comparator 401 is connected to the first input terminal of the AND gate 404 through an inverter 403, the output terminal of the second comparator 402 is connected to the second input terminal of the AND gate 404, and the output terminal of the AND gate is connected to the first input terminal of the AND gate 404. The gates of the second switches 407 and the drains of the second switches 407 are connected to the power supply Vcc2.

The output terminal of the first comparator 401 and the output terminal of the second comparator 402 are respectively connected to the first input terminal and the second input terminal of the NOR gate 405 , and the output terminal of the NOR gate 405 is connected to the third switch 408 . The gate and the drain of the third switch 408 are connected to the power supply Vcc3.

The source of the first switch 406 , the source of the second switch 407 , and the source of the third switch 408 are connected in parallel and then output to the driving module 212 .

A further improvement is that the first switch 406 , the second switch 407 and the third switch 408 are all NMOS transistors.

A further improvement is that the gate voltage output by the drive module 212 is adjusted in real time according to the temperature, and the gate voltage output when the temperature is high is higher than the output when the temperature is low; that is, the gate voltage output by the drive module 212 The pole voltage increases with increasing temperature.

A further improvement is that the power tube temperature detection module 216 detects the working temperature of the power tube 208 and outputs the corresponding signal voltage Vt according to the working temperature of the power tube 208 .

A further improvement is that the driving module (212) provides corresponding gate drive to the power tube (208) by adjusting according to the PWM signal provided by the trigger (213) and the voltage signal provided by the voltage control module (217). Voltage.

A further improvement is that, in the voltage control module (217), the power sources Vcc1, Vcc2, and Vcc3 are three preset switch gate driving voltages; the preset switch gate driving voltages are not limited to Three, with the corresponding number of switch tubes as required, more gate drive voltage levels of the switch tubes can be set.

The MOS drive circuit of the switching power supply of the present invention detects the real-time working temperature of the power switch tube through the power tube temperature detection module, transmits the temperature signal of the power switch tube in real time, and drives the gate drive voltage of the power switch tube with the power switch. changes in tube temperature. When the temperature is low, the drive module outputs a lower gate voltage; when the temperature is high, the drive module outputs a larger gate voltage, which can significantly reduce system losses and improve system efficiency.

Description of drawings

FIG. 1 is a circuit schematic diagram of a switching power supply in the prior art.

FIG. 2 is a circuit schematic diagram of the switching power supply of the present invention.

FIG. 3 is a schematic circuit diagram of the power tube temperature detection module 216 of the present invention.

FIG. 4 is a schematic circuit diagram of the voltage control module 217 of the present invention.

Description of reference numerals

Input capacitor Cin, first resistor 201, first capacitor C1, first diode 202, transformers 203, 204, 205, second diode 206, second capacitor C2, second resistor 207, power switch tube 208, The third resistor 209, the fourth resistor 210, the fifth resistor 211, the drive module 212, the trigger 213, the shutdown comparator 214, the power tube temperature detection module 216, the voltage control module 217, the control unit 218, the sixth resistor 219, The first comparator 401 , the second comparator 402 , the inverter 403 , the AND gate 404 , the NOR gate 405 , the first switch 406 , the second switch 407 , and the third switch 408 .

Detailed ways

For the MOS drive circuit of the switching power supply of the present invention, in order to make those skilled in the art better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clarified and explained below with reference to the accompanying drawings in the embodiments of the present invention. full description.

As shown in Figure 2, a driving circuit of a switching power supply, the circuit connection relationship is as follows:

An input capacitor Cin, the input capacitor is connected between the positive and negative input terminals of the power supply; the first resistor 201, the first end of the first resistor 201 is connected to the positive input terminal of the power supply, and the second end is connected to the first capacitor One end of C1 is connected, and the other end of the first capacitor C1 is grounded; the cathode of the first diode 202 is connected to the second section of the first resistor 201, and the anode of the first diode 202 is connected to the second primary coil 204 of the transformer One end of the second primary side coil 204 is connected to ground; the same name terminal of the first primary side coil 203 of the transformer is connected to the positive input terminal of the power supply; the same name terminal of the secondary side coil 205 of the transformer is the first output of the switching power supply terminal, the opposite terminal of the secondary coil 205 is connected to the anode of the second diode 206, and the cathode of the second diode 206 is the second output terminal of the switching power supply; the second capacitor C2 is connected in parallel with the second resistor 207 Then it is connected between the first and second output terminals of the switching power supply; the drain of the power tube 208 is connected to the opposite end of the first primary coil 203 of the transformer, and the source of the power tube 208 is grounded through the third resistor 209; A power tube temperature detection module 216, the power tube temperature detection module 216 is connected to the voltage control module 217, and provides a signal voltage Vt for the voltage control module 217; The input terminal is connected, one input terminal of the off-comparator 214 is connected to the first reference voltage Vref1, and the other input terminal is connected to the third resistor 209; after the fourth resistor 210 is connected in series with the fifth resistor 211, the other input terminal of the fifth resistor 211 One end is grounded, and the other end of the fourth resistor 210 is connected to the anode of the first diode 202; the S input end of the flip-flop 213 is connected to the series node of the fourth resistor 210 and the fifth resistor 211; the driving module 212, the driving The output end of the module 212 is connected to the gate of the power tube 208, and provides a driving voltage to control the on or off of the power tube 208; the same-direction output end of the trigger 213 is connected to the driving module 212, and the The output terminal is connected to the driving module 212 .

The switching power supply includes a transformer assembly, a first resistor 209 , a power switch tube 208 and a control unit 218 for driving the power switch tube. The control unit 218 includes a drive module 212 , and the control unit is connected to the original source of the transformer through the power switch tube 208 . side coil. The control unit controls the power switch tube 208 to be turned on in each switching cycle, and transmits the energy of the primary coil 203 of the transformer to the secondary coil 205 for output. The driving circuit includes a power tube temperature detection module 216 for detecting the temperature of the power switch tube 208; a voltage control module 217 for providing different voltages Vdd to the driving module 212 according to the temperature of the power tube, so that the output of the driving module 212 is different The gate drive voltage of the power transistor 208 is supplied.

As shown in FIG. 3 , in this embodiment, the power tube temperature detection module 216 includes a sixth resistor 219 with a certain temperature coefficient and a zero-temperature constant current source. The zero temperature constant current source outputs a constant current I1 to the first end of the sixth resistor 219 , the second end of the sixth resistor 219 is grounded, and the first end of the sixth resistor 219 outputs the signal voltage Vt.

When the system is working, if the temperature of the power tube 208 changes (for example, rises), the temperature on the sixth resistor 219 changes accordingly. Since the sixth resistor 219 has a temperature coefficient, I1 is a constant current source with zero temperature, so the voltage Vt changes accordingly (if the sixth resistor 219 is a positive temperature coefficient resistor, the Vt rises), and the change in the value of Vt reflects the power transistor. 208 temperature change.

As shown in FIG. 4 , the voltage control module 217 includes a first comparator 401, a second comparator 402, a first switch 406, a second switch 407, a third switch 408, and an inverter 403; the voltage The control module 217 includes: a first comparator 401, a second comparator 402, an inverter 403, an AND gate 404, a NOR gate 405, a first switch 406, a second switch 407, and a third switch 408; the first The positive input terminals of the comparator 401 and the second comparator 402 are connected in parallel with the signal voltage Vt, the negative input terminal of the first comparator 401 is connected to the second reference voltage Vref2, and the negative input terminal of the second comparator 402 is connected to the second reference voltage Vref2. The third reference voltage Vref3.

The output terminal of the first comparator 401 is connected to the gate of the first switch 406, and the drain of the first switch 406 is connected to the power supply Vcc1.

The output terminal of the first comparator 401 is connected to the first input terminal of the AND gate 404 through an inverter 403, the output terminal of the second comparator 402 is connected to the second input terminal of the AND gate 404, and the output terminal of the AND gate is connected to the first input terminal of the AND gate 404. The gates of the second switches 407 and the drains of the second switches 407 are connected to the power supply Vcc2.

The output terminal of the first comparator 401 and the output terminal of the second comparator 402 are respectively connected to the first input terminal and the second input terminal of the NOR gate 405 , and the output terminal of the NOR gate 405 is connected to the third switch 408 . The gate and the drain of the third switch 408 are connected to the power supply Vcc3.

The source of the first switch 406 , the source of the second switch 407 , and the source of the third switch 408 are connected in parallel and then output to the driving module 212 .

The first switch 406 , the second switch 407 and the third switch 408 are all NMOS transistors.

In FIG. 4 , Vref2 and Vref3 are two reference voltages preset by the chip according to system requirements, wherein Vref2<Vref3; Vcc1, Vcc2 and Vcc3 are the three preset gate driving voltages of the switches. When Vt is lower than Vref2 and Vref3, it is output from the NOR gate 405, and Vcc3 is output to the driving module 212 through the third switch tube 408 to drive the power switch tube 208. When Vt is higher than Vref2 and lower than Vref3, it is output through the AND gate 404, and Vcc2 is output to the driving module 212 through the second switch tube 407 to drive the power switch tube 208. When the Vt is higher than Vref2 and Vref3, Vcc1 is output to the driving module 212 through the first switch tube 406 to drive the power switch tube 208 .

In this embodiment, the gate driving voltage of the driving switch transistor 208 varies with the temperature of the power transistor. When the temperature is relatively low, the driving module 212 outputs a relatively low gate voltage; when the temperature is relatively high, the driving module 212 outputs a relatively large gate voltage. Therefore, the present invention can significantly reduce the system loss and improve the system efficiency.

The above description is only a preferred embodiment of the present invention, and does not limit the embodiment in any form. Anyone familiar with the art, without departing from the scope of the technical solutions of the present invention, can make many possible changes and modifications to the present invention by using the methods and technical contents disclosed above, or modify them into equivalent embodiments of equivalent changes, For example, the driving voltage of the current control module 217 is divided into three levels or more. Therefore, without departing from the content of the present invention, any simple modifications, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention still fall within the protection scope of the present invention.

The above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Various modifications and variations of the present invention are possible for those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. A MOS drive circuit of a switching power supply is characterized in that: the MOS drive circuit includes:

an input capacitor (Cin) connected across the positive and negative input terminals of the power supply;

the first end of the first resistor (201) is connected with the positive input end of the power supply, the second end of the first resistor (201) is connected with one end of a first capacitor (C1), and the other end of the first capacitor (C1) is grounded;

the negative electrode of the first diode (202) is connected with the second section of the first resistor (201), the positive electrode of the first diode (202) is connected with one end of a second primary coil (204) of the transformer, and the other end of the second primary coil (204) is grounded;

the dotted terminal of a first primary coil (203) of the transformer is connected with the positive input end of the power supply;

the dotted terminal of a secondary coil (205) of the transformer is a first output terminal of the switching power supply, the synonym terminal of the secondary coil (205) is connected with the anode of a second diode (206), and the cathode of the second diode (206) is a second output terminal of the switching power supply;

a second capacitor (C2) is connected in parallel with a second resistor (207) and then is connected between the first output end and the second output end of the switching power supply in a bridge connection mode;

the drain electrode of the power tube (208) is connected with the synonym terminal of the first primary coil (203) of the transformer, and the source electrode of the power tube (208) is grounded through a third resistor (209);

the power tube temperature detection module (216), the power tube temperature detection module (216) is connected with the voltage control module (217) and provides a signal voltage Vt for the voltage control module (217);

an output end of a turn-off comparator (214) is connected with an R input end of a trigger (213), an input end of the turn-off comparator (214) is connected with a first reference voltage Vref1, and the other input end of the turn-off comparator (214) is connected with a third resistor (209);

after the fourth resistor (210) is connected with the fifth resistor (211) in series, the other end of the fifth resistor (211) is grounded, and the other end of the fourth resistor (210) is connected with the anode of the first diode (202);

the S input end of the trigger (213) is connected with the series node of the fourth resistor (210) and the fifth resistor (211);

the output end of the driving module (212) is connected with the grid electrode of the power tube (208), and the driving voltage is provided to control the power tube (208) to be switched on or switched off;

the same-direction output end of the trigger (213) is connected with a driving module (212), and the output end of the voltage control module (217) is connected with the driving module (212).

2. The MOS drive circuit of the switching power supply according to claim 1, wherein: the power MOS tube (208) is an NMOS.

3. The MOS drive circuit of the switching power supply according to claim 1, wherein: the power tube temperature detection module (216) comprises: the zero-temperature constant current source outputs a constant current to a first end of the sixth resistor (219), a second end of the sixth resistor (219) is grounded, and a first end of the sixth resistor (219) outputs a signal voltage Vt.

4. A MOS drive circuit of a switching power supply according to claim 3, wherein: the sixth resistor (219) is a resistor with a temperature coefficient, and comprises a positive temperature coefficient or a negative temperature coefficient; when the sixth resistor (219) is a positive temperature coefficient resistor, the signal voltage Vt increases with an increase in temperature.

5. The MOS drive circuit of the switching power supply according to claim 1, wherein: the voltage control module (217) comprises: a first comparator (401), a second comparator (402), an inverter (403), an AND gate (404), a NOR gate (405), and a first switch (406), a second switch (407), and a third switch (408); the positive input ends of the first comparator (401) and the second comparator (402) are connected in parallel and then connected with a signal voltage Vt, the negative input end of the first comparator (401) is connected with a second reference voltage Vref2, and the negative input end of the second comparator (402) is connected with a third reference voltage Vref 3;

the output end of the first comparator (401) is connected with the grid of the first switch (406), and the drain electrode of the first switch (406) is connected with a power supply Vcc1;

the output end of the first comparator (401) is connected with the first input end of the AND gate (404) through an inverter (403), the output end of the second comparator (402) is connected with the second input end of the AND gate (404), the output end of the AND gate is connected with the grid of the second switch (407), and the drain of the second switch (407) is connected with a power supply Vcc2;

the output end of the first comparator (401) and the output end of the second comparator (402) are respectively connected to a first input end and a second input end of the NOR gate (405), the output end of the NOR gate (405) is connected with the grid of the third switch (408), and the drain electrode of the third switch (408) is connected with a power supply Vcc 3;

and the source of the first switch (406), the source of the second switch (407) and the source of the third switch (408) are connected in parallel and then output to the driving module (212).

6. The MOS drive circuit of the switching power supply according to claim 5, wherein: the first switch (406), the second switch (407) and the third switch (408) are all NMOS tubes.

7. The MOS drive circuit of the switching power supply according to claim 1, wherein: the gate voltage output by the driving module (212) is adjusted in real time according to the temperature, and the gate voltage output at higher temperature is higher than the gate voltage output at lower temperature; namely, the gate voltage output by the driving module (212) is increased along with the increase of the temperature.

8. The MOS drive circuit of the switching power supply according to claim 1, wherein: the power tube temperature detection module (216) detects the working temperature of the power tube (208), and outputs a corresponding signal voltage Vt according to the working temperature of the power tube (208).

9. The MOS drive circuit of the switching power supply according to claim 1, wherein: the driving module (212) is adjusted according to the PWM signal provided by the trigger (213) and the voltage signal provided by the voltage control module (217) to provide the corresponding gate driving voltage for the power tube (208).

10. The MOS drive circuit of the switching power supply according to claim 5, wherein: the voltage control module (217), the power supply Vcc1, Vcc2, Vcc3 are three preset switching tube gate driving voltages; the preset switching tube gate driving voltages are not limited to three, and more switching tube gate driving voltage grades can be set by matching with a corresponding number of switching tubes according to needs.

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