Composite synchronous rectification driving circuit and switching power supply

Abstract

The invention discloses a composite synchronous rectification driving circuit and a switching power supply, which are applied to the field of rectification driving circuits, and comprise a transformer, a first switching tube, a first capacitor, a first resistor, a second resistor, a second switching tube and a control circuit, compared with a traditional PWM synchronous rectification driving circuit, the PWM synchronous rectification driving circuit has the advantages that a layer of conduction conditions is added for the first switch tube serving as a rectification device by utilizing devices such as the switch tube, the diode and the resistor, and only when a transformer signal and a PWM wave are unified and matched, the first switch tube can be conducted. Abnormal conduction of the first switching tube when the driving pulse provided by the pulse width generator has an error is avoided, and the problem of circuit potential safety hazards caused by accidental conduction of a rectification device in the rectification driving circuit is solved.

Description

Technical Field

[0001] The invention relates to the field of rectification drive circuits, and in particular to a composite synchronous rectification drive circuit and a switching power supply. Background Art

[0002] The rectifier drive circuit is an important component in the power electronic circuit. Its main function is to provide appropriate trigger signals for rectifier devices such as thyristors and field effect transistors to control the rectification process.

[0003] The rectifier drive circuit is responsible for providing trigger signals to the rectifier devices, which control the on and off timing of the rectifier devices. In modern power electronic converters, the rectifier drive circuit usually requires precise timing control to ensure that the rectifier devices can be turned on and off at the right time, thereby achieving efficient power conversion.

[0004] In the traditional pulse width modulation (PWM) synchronous rectification drive circuit, such as Figure 1 As shown in the figure, the input end of the PWM wave is directly connected to the switch tube as a rectifier through a resistor. When the transformer stops working, but the pulse width generator is still providing pulses to the rectifier due to a fault, the rectifier will be directly turned on, causing a short circuit in the rectifier drive circuit. Usually, the circuit also has multiple parallel power supplies or battery packs, which has a greater destructive ability and will cause great safety hazards.

[0005] Therefore, a reliable rectifier drive solution is urgently needed to solve the circuit safety hazard problem caused by accidental conduction of the rectifier device in the rectifier drive circuit. Summary of the invention

[0006] In view of this, the purpose of the present invention is to provide a composite synchronous rectification drive circuit and a switching power supply, which can effectively solve the circuit safety hazard problem caused by the accidental conduction of the rectifier device in the rectification drive circuit. The specific scheme is as follows:

[0007] In a first aspect, the present application provides a composite synchronous rectification drive circuit, comprising: a transformer, a first switch tube and a first capacitor, a first resistor, a second resistor, a second switch tube and a control circuit arranged on an output loop of the transformer;

[0008] The control end of the first switch tube, the second end of the first resistor and the first end of the second resistor are connected;

[0009] The second end of the second resistor is connected to the first end of the second switch tube, and the second end of the second switch tube is connected to the output end of the PWM wave;

[0010] The input end of the control circuit is connected to the output end of the transformer and the output end of the PWM wave, and is used to detect the working state of the transformer and the output state of the PWM wave;

[0011] The output end of the control circuit is connected to the control end of the second switch tube, and is used to control the on and off of the second switch tube according to the working state of the transformer and the output state of the PWM wave.

[0012] Optionally, the control circuit includes: a first diode, a third resistor and a fourth resistor;

[0013] The anode of the first diode is connected to the first end of the third resistor, and the cathode of the first diode is connected to the output end of the transformer and the first end of the first switch tube;

[0014] The second end of the third resistor is connected to the first end of the fourth resistor, and a common end of the third resistor and the first end of the fourth resistor is connected to the control end of the second switch tube as the output end of the control circuit.

[0015] Optionally, the control circuit further includes: a second capacitor;

[0016] A first end of the second capacitor is connected to an anode of the first diode;

[0017] The second end of the second capacitor is connected to the control end of the second switch tube.

[0018] Optionally, the control circuit further includes: a second diode;

[0019] The anode of the second diode is connected to the control end of the first switch tube through a resistor;

[0020] A cathode of the second diode is connected to an output end of the PWM wave.

[0021] Optionally, the first capacitor is an electrolytic capacitor;

[0022] The anode of the electrolytic capacitor is the first end of the first capacitor, and the cathode of the electrolytic capacitor is the second end of the first capacitor.

[0023] Optionally, the PWM wave is synchronized with the phase of the electrical signal output by the transformer.

[0024] Optionally, the second switching tube is a PNP type transistor, the base is connected to the output end of the control circuit as a control end, the emitter is connected to the control end of the first switching tube through a resistor as a first end, and the collector is connected to the output end of the PWM wave as a first end.

[0025] Optionally, a short-circuit protection circuit is also provided on the output circuit of the transformer.

[0026] Optionally, the short-circuit protection circuit is a fuse.

[0027] In a second aspect, the present application provides a switching power supply, including the composite synchronous rectification drive circuit.

[0028] It can be seen that the present application discloses a composite synchronous rectification drive circuit. Compared with the traditional PWM synchronous rectification drive circuit, the present application uses devices such as switch tubes, diodes and resistors to add a layer of conduction conditions for the first switch tube as a rectifier device: the first switch tube can only be turned on when the transformer signal and the PWM wave are unified and matched. This avoids the abnormal conduction of the rectifier device when an error occurs in the driving pulse provided by the pulse width generator, and solves the circuit safety hazard problem caused by the accidental conduction of the rectifier device in the rectifier drive circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0030] Figure 1 A PWM synchronous rectification driving circuit diagram provided in an embodiment of the present application;

[0031] Figure 2 A composite synchronous rectification driving circuit diagram provided in an embodiment of the present application;

[0032] Figure 3 A composite synchronous rectification driving circuit diagram provided in an embodiment of the present application. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] The core of this application is to provide a composite synchronous rectification drive circuit.

[0035] In order to enable those skilled in the art to better understand the present application, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0036] In the power supply circuit, the rectifier drive circuit is an indispensable part. Its main function is to provide appropriate trigger signals for rectifier devices such as thyristors and field effect transistors to control the rectification process.

[0037] The rectifier drive circuit is responsible for providing trigger signals to the rectifier devices, which control the on and off timing of the rectifier devices. In modern power electronic converters, the rectifier drive circuit usually requires precise timing control to ensure that the rectifier devices can be turned on and off at the right time, thereby achieving efficient power conversion.

[0038] In the traditional PWM synchronous rectification drive circuit, such as Figure 1 As shown in the figure, the input end of the PWM wave is directly connected to the switch tube as a rectifier through a resistor. When the transformer T1 stops working, but the pulse width generator is still providing pulses to the rectifier due to a fault, the rectifier will be directly turned on, causing a short circuit in the rectifier drive circuit. If the circuit is still connected to multiple power supplies or battery packs in parallel at this time, the circuit will have a greater destructive ability, which will lead to great safety hazards.

[0039] Therefore, a reliable rectifier drive solution is urgently needed to solve the circuit safety hazard problem caused by accidental conduction of the rectifier device in the rectifier drive circuit.

[0040] Figure 2 A composite synchronous rectification driving circuit is provided in an embodiment of the present application. Figure 2 As shown, in order to solve the above problems, this embodiment provides a composite synchronous rectification driving circuit including: a transformer T1, a first switch tube Q1 and a first capacitor C1 arranged on the output loop of the transformer T1, a first resistor R1, a second resistor R2, a second switch tube Q2 and a control circuit;

[0041] The control end of the first switch tube Q1, the second end of the first resistor R1 and the first end of the second resistor R2 are connected;

[0042] The second end of the second resistor R2 is connected to the first end of the second switch tube Q2, and the second end of the second switch tube Q2 is connected to the output end of the PWM wave;

[0043] The input end of the control circuit is connected to the output end of the transformer T1 and the output end of the PWM wave, and is used to detect the working state of the transformer T1 and the output state of the PWM wave;

[0044] The output end of the control circuit is connected to the control end of the second switch tube Q2, and is used to control the on and off of the second switch tube Q2 according to the working state of the transformer T1 and the output state of the PWM wave.

[0045] like Figure 2As shown, the first output end of the transformer T1 is connected to the first end of the first capacitor C1 and the voltage output end. When the transformer inputs an electrical signal with positive top and negative bottom, it conforms to the circuit rectification direction and is output from the voltage output end. The second output end of the transformer T1 is connected to the first end of the first switch tube Q1 and one of the input ends of the control circuit. The second end of the first switch tube Q1 is connected to the second end of the first capacitor C1 and the first end of the first resistor R1, and the common end of the three is grounded. The control end of the first switch tube Q1 is connected to the second end of the first resistor R1 and the first end of the second resistor R2. The first resistor R1 and the second resistor R2 are used as voltage-dividing resistors to reasonably configure the conduction condition of the first switch tube Q1.

[0046] Figure 2 The right side of the improved circuit is the output end of the PWM wave, which is used to input the driving pulse signal for controlling the opening and closing of the first switch tube Q1. The output end of the PWM wave is connected to the pulse width generator. The PWM wave provided by the pulse width generator is a pulse synchronized with the electrical signal output by the transformer T1. The pulse width generator here can be a single-chip microcomputer: the single-chip microcomputer collects the electrical signal output by the transformer T1, and connects the synchronized pulse to the control circuit through the output end of the PWM wave. The control circuit controls the conduction and shutdown of the second switch tube Q2 according to the working state of the transformer T1 and the output state of the PWM wave. Under normal working conditions, the electrical signal output by the transformer T1 should reach the control circuit at the same time as the PWM wave, and the second switch tube Q2 is turned on. When the pulse width generator is abnormal, once the electrical signal output by the transformer T1 does not reach the control circuit at the same time as the PWM wave, the control circuit will not control the second switch tube Q2 to be turned on. In this way, when the transformer T1 stops, the pulse width generator outputs a pulse at the same time as the fault, and the drive circuit is accidentally turned on, causing the circuit to short-circuit. Since most driving circuits are connected in parallel to a battery pack or power source, once a short circuit occurs in the driving circuit, the circuit will generate a huge current for a while, thereby causing a fire or explosion. Therefore, the present invention constructs a control circuit and determines the conduction of the second switch tube Q2 through the control circuit by the PWM wave signal and the T1 input signal, thereby determining the conduction of the first switch tube Q1.

[0047] It can be seen that the embodiment of the present application discloses a composite synchronous rectification drive circuit. Compared with the traditional PWM synchronous rectification drive circuit, the present application uses devices such as switch tubes, diodes and resistors to add a layer of conduction conditions for the rectifier device: the rectifier device can only be turned on when the input signal of the transformer T1 and the PWM wave are unified and matched. This avoids the abnormal conduction of the rectifier device when an error occurs in the drive pulse provided by the pulse width generator, and solves the circuit safety hazard problem caused by the accidental conduction of the rectifier device in the rectifier drive circuit.

[0048] Figure 3 A composite synchronous rectification driving circuit diagram provided in an embodiment of the present application is as follows: Figure 3 As shown, according to the above embodiment, this embodiment provides a specific solution, the control circuit includes: a first diode D1, a third resistor R3 and a fourth resistor R4;

[0049] The anode of the first diode D1 is connected to the first end of the third resistor R3, and the cathode of the first diode D1 is connected to the output end of the transformer T1 and the first end of the first switch tube Q1;

[0050] The second end of the third resistor R3 is connected to the first end of the fourth resistor R4, and a common end of the two is connected to the control end of the second switch tube Q2 as the output end of the control circuit.

[0051] As shown in the figure, the third resistor R3 and the fourth resistor R4 are bias resistors of the second switch tube Q2, and the first diode D1 has unidirectional conductivity, and together constitute a control circuit of the second diode D2.

[0052] In a specific embodiment, taking the output end of the transformer T1 as an example with the upper positive and the lower negative, at this time, the control end of the second switch tube Q2 is pulled down by the first diode D1 and the third resistor R3, and at this time, the second switch tube Q2 is turned on, and the synchronous rectification drive signal PWM wave is completely sent to the control end of the first switch tube Q1 through the second switch tube Q2 and the second resistor R2, so that the first end and the second end of the first switch tube Q1 are turned on.

[0053] It can be seen that only when the PWM wave and the transformer T1 signal are transmitted synchronously, the second switch tube Q2 is turned on, and the PWM wave signal is transmitted to the control end of the first switch tube Q1 through the second switch tube Q2 and the resistor, thereby turning on the first switch tube Q1. The control circuit effectively improves the reliability of the drive circuit and avoids the accidental turn-on of the rectifier device when the pulse width generator fails and is not synchronized with the transformer T1 to provide pulses for the rectifier device.

[0054] According to the above embodiment, this embodiment provides a specific solution, wherein the control circuit further includes: a second capacitor C2;

[0055] A first end of the second capacitor C2 is connected to the anode of the first diode D1;

[0056] The second end of the second capacitor C2 is connected to the control end of the second switch tube Q2.

[0057] like Figure 3 As shown, the second capacitor C2 is connected in parallel with both sides of the third resistor R3. Taking the output end of the transformer T1 as positive at the top and negative at the bottom as an example, when the PWM wave is input, the first and second diodes are turned on only when the cathode of the first diode D1 is negative. At this time, the second capacitor C2 is charged. The charging moment is equivalent to a wire, which quickly lowers the voltage of the second switch tube Q2, accelerates the conduction speed of the second switch tube Q2, and makes the first switch tube Q1 turn on instantly.

[0058] It can be seen that the second capacitor C2 speeds up the conduction speed of the second switch tube Q2. Since the electrical signal in the circuit is a periodic signal, the instant conduction characteristic helps to effectively transmit the signal and prevent the delay of the signal in one cycle from affecting the next cycle.

[0059] According to the above embodiment, this embodiment provides a specific solution, the control circuit further includes: a second diode D2;

[0060] The anode of the second diode D2 is connected to the control end of the first switch tube Q1 through a resistor;

[0061] The cathode of the second diode D2 is connected to the output end of the PWM wave.

[0062] like Figure 3 As shown, the second diode D2 is connected in parallel with the second switch tube Q2. When the synchronous rectification drive signal PWM wave is turned off, the PWM wave signal is in a low level state. Due to the existence of the second diode D2, the control end of the first switch tube Q1 is instantly pulled down, and the first switch tube Q1 quickly enters the off state.

[0063] It can be seen that the second diode D2 can pull down the control terminal of the first switch tube Q1 to a low potential at the moment when the PWM wave is turned off, thereby turning off the first switch tube Q1, thereby ensuring the timeliness of the electrical signal in the circuit.

[0064] According to the above embodiment, this embodiment provides a specific solution, the first capacitor C1 is an electrolytic capacitor;

[0065] The anode of the electrolytic capacitor is the first end of the first capacitor C1 , and the cathode of the electrolytic capacitor is the second end of the first capacitor C1 .

[0066] Polar capacitors have larger capacitance values ​​than ordinary capacitors. In this embodiment, the circuit can be connected to electric vehicles and other electrical equipment. The high-capacity characteristics of polar capacitors can reduce the number and volume of capacitors in the circuit, making the circuit design more concise and efficient. At the same time, when the circuit in this embodiment is connected to both ends of a battery pack such as an electric vehicle, the polar capacitor generally has a relatively stable capacitance value and voltage characteristic within its operating voltage range relative to ordinary capacitors. That is, under different working conditions, polar capacitors can provide relatively consistent filtering and energy storage effects, reducing the impact of voltage changes on circuit performance.

[0067] In this embodiment, when the phase of the PWM wave is synchronized with the electrical signal output by the transformer T1, it can be ensured that the first switch tube Q1 is turned on when the pulse width generator of the PWM wave is working normally. If the phase of the PWM wave is not synchronized with the electrical signal output by the transformer T1, the circuit for controlling the conduction of the same switch tube by using two signals with delayed timing will be very complicated. In order to ensure the feasibility of operation, a single-chip microcomputer chip needs to be added to strictly control the timing, which does not meet the principle of simple and reliable circuit design.

[0068] According to the above embodiment, this embodiment provides a specific solution, the second switch tube Q2 is a PNP type transistor, the base is connected to the output end of the control circuit as the control end, the emitter is connected to the control end of the first switch tube Q1 through a resistor as the first end, and the collector is connected to the output end of the PWM wave as the first end.

[0069] In a specific embodiment, taking the output end of transformer T1 as positive at the top and negative at the bottom as an example, when a PWM wave is input, it is easier to build a circuit environment that meets the PNP conduction conditions through a resistor based on the potential input of transformer T1. Therefore, a PNP transistor is selected as one of the key components for controlling the conduction of the first switch tube Q1.

[0070] According to this embodiment, a specific solution is provided, which also includes a short-circuit protection circuit arranged on the output loop of the transformer T1.

[0071] Depend on Figure 3 It can be seen that when the voltage output end of the circuit is connected to a load or a power supply, a short circuit in the circuit will cause a great safety hazard. Therefore, a short-circuit protection circuit is provided on the output loop of the transformer T1 to further improve the safety of the circuit during operation.

[0072] According to the above embodiments, this embodiment provides a specific solution, in which the short-circuit protection circuit is a fuse.

[0073] When normal current flows through the circuit, the fuse in the fuse will generate a certain amount of heat due to its own resistance. However, under normal working conditions, this heat is relatively small and will not melt the fuse. When an overcurrent occurs in the circuit due to a short circuit, the current will increase sharply. According to Joule's law, a large increase in current will cause the fuse to heat up rapidly, and the heat generated will far exceed the heat during normal working. As the heat continues to accumulate, the temperature of the fuse rises rapidly. When the temperature reaches the melting point of the fuse, the fuse begins to melt. After the melt melts, it will disconnect the circuit, thereby protecting other devices and components in the circuit.

[0074] In order to make it clearer to those skilled in the art Figure 3 The circuit structure and working principle shown will be described in detail below. Figure 3 A specific implementation method of this application is as follows: Figure 3 As shown, the first switch tube Q1 is an NMOS tube, and the direction of the rectified electrical signal output by this embodiment is positive at the top and negative at the bottom of the transformer. In the initial state, the circuit has no input, which means that the transformer has no input, and the input end of the PWM wave has no input. At this time, the first switch tube Q1 and the second switch tube Q2 are closed. When the input of the transformer T1 is negative at the top and positive at the bottom, it does not conform to the rectification direction of the composite synchronous rectification drive circuit of this embodiment. The resistance values ​​and ratios of the third resistor R3 and the fourth resistor R4 are set. At this time, the voltage difference between the emitter and the base of the second switch tube Q2 cannot make the third switch tube conduct. At this time, the first switch tube Q1 remains in the off state. When the input of the transformer is positive at the top and negative at the bottom, it conforms to the rectification direction of the composite synchronous rectification drive circuit of this embodiment. At this time, the cathode of the first diode D1 is a negative voltage. At this time, a positive voltage signal is input to the PWM wave input end, and the second switch tube Q2 meets the conduction condition. The second switch tube is turned on and transmits the PWM wave to the control end of the first switch tube Q1. The first switch tube Q1 is turned on, and the voltage output end outputs the voltage signal of the transformer with positive at the top and negative at the bottom.

[0075] When the driving pulse signal timing and pulse width generator fail to synchronize with the phase of the output terminal of the transformer T1, since the transformer T1 is not positive at the top and negative at the bottom, the second switch tube Q2 will not be turned on, and the first switch tube Q1 is in the off state;

[0076] When the transformer T1 stops working for any reason, the upper and lower ends of the output are at 0 level; or when multiple machines or parallel battery packs appear at the output end, the upper and lower ends of the transformer are at high level. At this time, when the synchronous rectification drive signal PWM wave arrives, the second switch tube Q2 still cannot be turned on, so the first switch tube Q1 is always in the off state.

[0077] To sum up, the first switch tube Q1 will be turned on normally only when the transformer T1 works normally and the synchronous rectification drive signal PWM wave is complete and correct. If any correct state is missing, the composite synchronous rectification drive circuit of this embodiment will be in a closed state, ensuring the reliability of the composite synchronous rectification drive circuit of this embodiment.

[0078] Finally, this embodiment provides a switching power supply, including the composite synchronous rectification driving circuit.

[0079] The above is a detailed introduction to the composite synchronous rectification drive circuit and switching power supply provided by the present application. The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same and similar parts between the embodiments can refer to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can refer to the method part description. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the scope of protection of the claims of the present application.

[0080] It should also be noted that, in this specification, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

Claims

1. A composite synchronous rectification driving circuit, characterized in that: It includes: a transformer, a first switch tube and a first capacitor arranged on an output loop of the transformer, a first resistor, a second resistor, a second switch tube and a control circuit; The control end of the first switch tube, the second end of the first resistor and the first end of the second resistor are connected; The second end of the second resistor is connected to the first end of the second switch tube, and the second end of the second switch tube is connected to the output end of the PWM wave; The input end of the control circuit is connected to the output end of the transformer and the output end of the PWM wave, and is used to detect the working state of the transformer and the output state of the PWM wave; The output end of the control circuit is connected to the control end of the second switch tube, and is used to control the on and off of the second switch tube according to the working state of the transformer and the output state of the PWM wave.

2. The composite synchronous rectification driving circuit according to claim 1, characterized in that: The control circuit comprises: a first diode, a third resistor and a fourth resistor; The anode of the first diode is connected to the first end of the third resistor, and the cathode of the first diode is connected to the output end of the transformer and the first end of the first switch tube; The second end of the third resistor is connected to the first end of the fourth resistor, and a common end of the third resistor and the first end of the fourth resistor is connected to the control end of the second switch tube as the output end of the control circuit.

3. The composite synchronous rectification driving circuit according to claim 2, characterized in that: The control circuit also includes: a second capacitor; A first end of the second capacitor is connected to an anode of the first diode; The second end of the second capacitor is connected to the control end of the second switch tube.

4. The composite synchronous rectification driving circuit according to claim 2 or 3, characterized in that: The control circuit further includes: a second diode; The anode of the second diode is connected to the control end of the first switch tube through a resistor; A cathode of the second diode is connected to an output end of the PWM wave.

5. The composite synchronous rectification driving circuit according to claim 1, characterized in that: The first capacitor is an electrolytic capacitor; The anode of the electrolytic capacitor is the first end of the first capacitor, and the cathode of the electrolytic capacitor is the second end of the first capacitor.

6. The composite synchronous rectification driving circuit according to claim 1, characterized in that: The PWM wave is synchronized with the phase of the electrical signal output by the transformer.

7. The composite synchronous rectification driving circuit according to claim 1, characterized in that: The second switch tube is a PNP type transistor, the base is connected to the output end of the control circuit as a control end, the emitter is connected to the control end of the first switch tube through a resistor as a first end, and the collector is connected to the output end of the PWM wave as a first end.

8. The composite synchronous rectification driving circuit according to claim 1, characterized in that: It also includes a short-circuit protection circuit arranged on the output loop of the transformer.

9. The composite synchronous rectification driving circuit according to claim 8, characterized in that: The short circuit protection circuit is a fuse.

10. A switching power supply, characterized in that: A composite synchronous rectification drive circuit comprising any one of claims 1 to 9.

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