Spiking voltage control circuit and synchronous rectification switching power supply

Abstract

The application provides a spike voltage control circuit and a synchronous rectification switching power supply. The spike voltage control circuit is used for controlling a spike voltage on a first switch tube in the synchronous rectification switching power supply. The spike voltage control circuit comprises a charge-discharge capacitor, a first on-off control unit, a second on-off control unit and an energy consumption unit. The charge-discharge capacitor is used for absorbing and storing the spike voltage generated when the first switch tube is turned off. The first on-off control unit is used for realizing one-way conduction from the first end to the second end of the first on-off control unit when the first switch tube is turned off. The second on-off control unit is used for realizing one-way conduction from the first end to the second end of the second on-off control unit when the first switch tube is turned off, so as to transmit the energy stored in the charge-discharge capacitor to an energy storage electrolytic capacitor for storage when the first switch tube is turned off. The energy is transmitted to the energy storage electrolytic capacitor for storage, the loss is reduced, and the conversion efficiency of the power supply is improved.

Description

Technical Field

[0001] This application relates to the field of power supply technology, specifically to a peak voltage control circuit and a synchronous rectification switching power supply. Background Technology

[0002] A switch-mode power supply (SMPS), also known as a switching converter or switching power supply, is a high-frequency power conversion device and a type of power supply. Its function is to convert a voltage at a certain level into the voltage or current required by the user through different architectural structures. In synchronous rectified switching power supplies, a combination of a first switching transistor and a second switching transistor is typically used on the output side. However, due to parasitic inductance and capacitance in the PCB circuitry, the first switching transistor may experience voltage spikes when turned off. If not controlled, these spikes can easily damage the first switching transistor, causing irreversible failure of the entire synchronous rectified switching power supply.

[0003] In traditional solutions, to control the voltage spike, an RC snubber circuit is typically connected in parallel across the first and second terminals of the first switching transistor. When the first switching transistor is turned off and a voltage spike occurs, the energy corresponding to the voltage spike flows through the capacitor and resistor in the RC snubber circuit. Part of the energy is stored in the capacitor, and part of the energy is consumed in the resistor. At the start of the next cycle (i.e., when the first switching transistor is turned on), the energy stored in the capacitor flows sequentially through the capacitor, the first switching transistor, the resistor, and the capacitor, thus consuming the stored energy in the first switching transistor and the resistor. This entire process addresses the issue of significant energy loss caused by the voltage spike of the first switching transistor, which reduces the conversion efficiency of the synchronous rectified switching power supply. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this application provides a peak voltage control circuit and a synchronous rectification switching power supply.

[0005] In one embodiment, this application provides a spike voltage control circuit for controlling a spike voltage appearing on a first switching transistor in a synchronous rectified switching power supply; the spike voltage control circuit includes:

[0006] The system includes a charging / discharging capacitor, a first on / off control unit, a second on / off control unit, and an energy-consuming unit.

[0007] The first end of the charging and discharging capacitor is electrically connected to the first input terminal of the first switching transistor. The second end of the charging and discharging capacitor is electrically connected to the first end of the first on / off control unit and the second end of the second on / off control unit. The second end of the first on / off control unit is electrically connected to the positive terminal of the energy storage electrolytic capacitor of the synchronous rectifier switching power supply. The first end of the second on / off control unit is electrically connected to the second input terminal of the first switching transistor and the negative terminal of the energy storage electrolytic capacitor. The energy dissipation unit is connected in series between the second end of the charging and discharging capacitor and the positive terminal of the energy storage electrolytic capacitor.

[0008] The charge-discharge capacitor is used to absorb and store the energy of the spike voltage generated when the first switching transistor is turned off.

[0009] The first on / off control unit is used to achieve unidirectional conduction from the first terminal to the second terminal of the first on / off control unit when the first switch is off, and the second on / off control unit is used to achieve unidirectional conduction from the first terminal to the second terminal of the second on / off control unit when the first switch is off, so as to transfer the energy stored in the charging / discharging capacitor to the energy storage electrolytic capacitor for storage when the first switch is off.

[0010] The energy-consuming unit is used to consume a portion of the energy transferred from the charging and discharging capacitors to the energy storage electrolytic capacitors.

[0011] In one embodiment, the energy-consuming unit includes a bleed resistor;

[0012] The bleed resistor is connected in series between the second terminal of the charging / discharging capacitor and the positive terminal of the energy storage electrolytic capacitor.

[0013] In one embodiment, the first end of the energy-consuming unit is electrically connected to the second end of the first on / off control unit, and the second end of the energy-consuming unit is electrically connected to the positive terminal of the energy storage electrolytic capacitor.

[0014] In one embodiment, the first on / off control unit includes a first diode;

[0015] The anode of the first diode is electrically connected to the second terminal of the charging / discharging capacitor and the second terminal of the second on / off control unit, and the cathode of the first diode is electrically connected to the positive terminal of the energy storage electrolytic capacitor.

[0016] In one embodiment, the second on / off control unit includes a second diode;

[0017] The cathode of the second diode is electrically connected to the second terminal of the charging / discharging capacitor and the first terminal of the first on / off control unit, respectively. The anode of the second diode is electrically connected to the second access terminal of the first switching transistor and the negative terminal of the energy storage electrolytic capacitor, respectively.

[0018] In one embodiment, the spike voltage control circuit further includes:

[0019] Clamping unit;

[0020] The first end of the clamping unit is electrically connected to the first end of the charging and discharging capacitor and the first input terminal of the first switching transistor, respectively. The second end of the clamping unit is electrically connected to the positive terminal of the energy storage electrolytic capacitor and the second end of the first on / off control unit, respectively.

[0021] The clamping unit is used to transfer the energy corresponding to the peak voltage generated by the first switching transistor to the energy storage electrolytic capacitor for storage when the peak voltage generated by the first switching transistor exceeds the preset voltage.

[0022] In one embodiment, the clamping unit includes a bidirectional TVS tube;

[0023] The first anode of the bidirectional TVS diode is electrically connected to the first input terminal of the first switching transistor and the first terminal of the charging / discharging capacitor, respectively. The second anode of the bidirectional TVS diode is electrically connected to the second terminal of the first on / off control unit and the positive terminal of the energy storage electrolytic capacitor, respectively.

[0024] Secondly, in one embodiment, this application provides a synchronous rectifier switching power supply, including a transformer, a second switching transistor, a first switching transistor, an energy storage electrolytic capacitor, and an inductor. The first input terminal of the second switching transistor is electrically connected to the first terminal of the secondary winding of the transformer. The second input terminal of the second switching transistor is electrically connected to both the first terminal of the inductor and the first input terminal of the first switching transistor. The second terminal of the inductor is electrically connected to the positive terminal of the energy storage electrolytic capacitor. The second terminal of the secondary winding of the transformer, the second input terminal of the first switching transistor, and the negative terminal of the energy storage electrolytic capacitor are grounded. The synchronous rectifier switching power supply further includes:

[0025] The spike voltage control circuit in any of the above embodiments.

[0026] In one embodiment, the synchronous rectifier switching power supply further includes a first switching transistor driving circuit; the first switching transistor driving circuit includes:

[0027] NPN transistors and PNP transistors;

[0028] The bases of the NPN transistor and the PNP transistor are connected to control signals, respectively. The collector of the NPN transistor is connected to the operating power supply signal. The emitter of the NPN transistor is electrically connected to the control terminal of the first switching transistor and the collector of the PNP transistor, respectively. The emitter of the PNP transistor is grounded.

[0029] In one embodiment, the first switch driver circuit further includes:

[0030] Filter capacitor;

[0031] The first terminal of the filter capacitor is electrically connected to the collector of the NPN transistor, and the second terminal of the filter capacitor is grounded.

[0032] Through the aforementioned peak voltage control circuit and synchronous rectifier switching power supply, a first on / off control unit and a second on / off control unit are set up. The second terminal of the charging / discharging capacitor is electrically connected to the first terminal of the first on / off control unit and the second terminal of the second on / off control unit, respectively. The second terminal of the first on / off control unit is electrically connected to the positive terminal of the energy storage electrolytic capacitor of the synchronous rectifier switching power supply. The first terminal of the second on / off control unit is electrically connected to the second input terminal of the first switching transistor and the negative terminal of the energy storage electrolytic capacitor, respectively. By utilizing the on / off control capabilities of the first and second on / off control units for the corresponding lines, the energy stored in the charging / discharging capacitor can be reliably transferred to the energy storage electrolytic capacitor for storage. The energy stored in the energy storage electrolytic capacitor can be used to supply the output terminal of the synchronous rectifier switching power supply, thereby reducing energy loss and improving the conversion efficiency of the synchronous rectifier switching power supply. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of a spike voltage control circuit provided in one embodiment of this application;

[0035] Figure 2 This is a schematic diagram of the specific structure of a spike voltage control circuit provided in one embodiment of this application;

[0036] Figure 3 A schematic diagram of a synchronous rectifier switching power supply provided in one embodiment of this application;

[0037] Figure 4 This is a schematic diagram of the specific structure of a synchronous rectifier switching power supply provided in one embodiment of this application. Detailed Implementation

[0038] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0039] In the description of this application, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly specified. In this application, the term "exemplary" is used to mean "used as an example, illustration, or description." Any embodiment described as "exemplary" in this application is not necessarily to be construed as being more preferred or advantageous than other embodiments. To enable any person skilled in the art to implement and use this application, the following description is provided. In this description, details are set forth for purposes of explanation. It should be understood that those skilled in the art will recognize that this application can be implemented without using these specific details. In other instances, well-known structures and processes will not be described in detail to avoid obscuring the description of this application with unnecessary detail. Therefore, this application is not intended to be limited to the embodiments shown, but is consistent with the broadest scope of the principles and features disclosed in this application.

[0040] Firstly, such as Figure 1 As shown, in one embodiment, this application provides a spike voltage control circuit for controlling the spike voltage on the first switching transistor (in this embodiment, the first switching transistor is a first MOS transistor) that appears in the synchronous rectified switching power supply.

[0041] The spike voltage control circuit includes:

[0042] The system includes a charging / discharging capacitor, a first on / off control unit, a second on / off control unit, and an energy-consuming unit.

[0043] The first terminal of the charging and discharging capacitor is electrically connected to the drain of the first MOSFET. The second terminal of the charging and discharging capacitor is electrically connected to the first terminal of the first on / off control unit and the second terminal of the second on / off control unit. The second terminal of the first on / off control unit is electrically connected to the positive terminal of the energy storage electrolytic capacitor of the synchronous rectifier switching power supply. The first terminal of the second on / off control unit is electrically connected to the source of the first MOSFET and the negative terminal of the energy storage electrolytic capacitor. The energy dissipation unit is connected in series between the second terminal of the charging and discharging capacitor and the positive terminal of the energy storage electrolytic capacitor.

[0044] The first on / off control unit is mainly used to control the on / off of the line between the charging / discharging capacitor and the energy storage electrolytic capacitor.

[0045] In the synchronous rectifier switching power supply, the source of the first MOSFET and the negative terminal of the energy storage electrolytic capacitor are grounded, that is, the second on / off control unit is mainly used to control the connection and disconnection of the line between the charging and discharging capacitor and ground.

[0046] The charge-discharge capacitor is used to absorb and store the energy of the spike voltage generated when the first MOSFET is turned off.

[0047] The first on / off control unit is used to achieve unidirectional conduction from the first terminal to the second terminal of the first on / off control unit when the first MOSFET is turned off, and the second on / off control unit is used to achieve unidirectional conduction from the first terminal to the second terminal of the second on / off control unit when the first MOSFET is turned off, so as to transfer the energy stored in the charging / discharging capacitor to the energy storage electrolytic capacitor for storage when the first MOSFET is turned off.

[0048] In the prior art, the second terminal of the charging / discharging capacitor is grounded through a resistor, thus forming an RC absorption clamping circuit. This RC absorption clamping circuit is connected in parallel with the first MOSFET to form a loop, enabling the charging / discharging capacitor to charge and store energy based on the voltage spikes appearing across the first MOSFET. Utilizing the characteristic that the voltage across the capacitor cannot change abruptly, the voltage at the end of the charging / discharging capacitor closest to the resistor is pulled up, thereby dissipating most of the energy on the resistor. In this embodiment, when the first MOSFET is off, the second on / off control unit achieves unidirectional conduction from the first terminal to the second terminal of the second on / off control, meaning that a path from the charging / discharging capacitor to ground cannot be formed as in the prior art, and the energy stored in the charging / discharging capacitor cannot be dissipated on the resistor. At the same time, the first on / off control unit achieves unidirectional conduction from the first terminal to the second terminal of the first on / off control unit, thus forming a path from the charging / discharging capacitor to the energy storage electrolytic capacitor, meaning that the energy stored in the charging / discharging capacitor can be transferred to the energy storage electrolytic capacitor for storage through the first on / off control unit.

[0049] Both the first on / off control unit and the second on / off control unit can be transistors, such as NPN transistors. The collector of the transistor corresponding to the first on / off control unit is electrically connected to the second terminal of the charging / discharging capacitor and the emitter of the transistor corresponding to the second on / off control unit. The emitter of the transistor corresponding to the first on / off control unit is electrically connected to the positive terminal of the energy storage electrolytic capacitor. The collector of the transistor corresponding to the second on / off control unit is electrically connected to the source of the first MOSFET and the negative terminal of the energy storage electrolytic capacitor. When the first MOSFET is off, the transistor corresponding to the first on / off control unit is turned on. When the first MOSFET is on, the transistor corresponding to the second on / off control unit is turned on.

[0050] The energy-consuming unit is used to consume a portion of the energy transferred from the charging and discharging capacitors to the energy storage electrolytic capacitors;

[0051] Although the charging and discharging capacitor transfers the stored energy to the energy storage electrolytic capacitor for storage, this process does not involve energy consumption. However, both the charging and discharging capacitor and the energy storage electrolytic capacitor are connected in parallel across the first MOSFET, resulting in a still high voltage across the first MOSFET, which poses a risk of damage. Therefore, in this embodiment, an energy-consuming unit is also provided to consume a portion of the energy transferred from the charging and discharging capacitor to the energy storage electrolytic capacitor, thereby reducing the voltage across the first MOSFET.

[0052] The energy-consuming unit can be any device or apparatus that consumes energy in any way. For example, it can be a motor in a power system connected to a synchronous rectifier switching power supply, thereby driving the corresponding motor to rotate and converting energy into kinetic energy to achieve consumption.

[0053] Through the aforementioned peak voltage control circuit, a first on / off control unit and a second on / off control unit are set up. By utilizing the on / off control capabilities of the first on / off control unit and the second on / off control unit for the corresponding lines, the energy stored in the charging and discharging capacitor can be reliably transferred to the energy storage electrolytic capacitor for storage. The energy stored in the energy storage electrolytic capacitor can be used to supply the output terminal of the synchronous rectifier switching power supply, thereby reducing energy loss and improving the conversion efficiency of the synchronous rectifier switching power supply.

[0054] like Figure 2 As shown, in one embodiment, the power dissipation unit includes a discharge resistor R6;

[0055] The discharge resistor R6 is connected in series between the second terminal of the charging / discharging capacitor C5 and the positive terminal of the energy storage electrolytic capacitor C7;

[0056] When energy flows through the bleed resistor R6, the bleed resistor R6 will generate heat, which will then be consumed as thermal energy.

[0057] Energy is dissipated through resistance, resulting in a simple structure.

[0058] like Figure 2 As shown, in one embodiment, the first on / off control unit includes a first diode D3, and the second on / off control unit includes a second diode D5;

[0059] The anode of the first diode is electrically connected to the second terminal of the charging and discharging capacitor and the cathode of the second diode D5, respectively. The cathode of the first diode is electrically connected to the positive terminal of the energy storage electrolytic capacitor C7, and the anode of the second diode D5 is electrically connected to the source of the first MOS transistor Q3 and the negative terminal of the energy storage electrolytic capacitor C7, respectively.

[0060] Diodes have unidirectional conduction characteristics, so using them as on / off control units results in a simple structure and simplifies the circuit.

[0061] like Figure 2 As shown, in one embodiment, the first end of the energy-consuming unit (i.e., the first end of the discharge resistor R6) is electrically connected to the second end of the first on / off control unit (i.e., the cathode of the first diode D3), and the second end of the energy-consuming unit (i.e., the second end of the discharge resistor R6) is electrically connected to the positive terminal of the energy storage electrolytic capacitor C7.

[0062] In other embodiments, the energy-consuming unit may also be located in other locations, such as... Figure 1 As shown, the first end of the energy-consuming unit is electrically connected to the second end of the charging / discharging capacitor, and the second end of the energy-consuming unit is electrically connected to the first end of the first on / off control unit and the second end of the second on / off control unit, respectively.

[0063] like Figure 1 As shown, in one embodiment, the spike voltage control circuit further includes:

[0064] Clamping unit;

[0065] The first end of the clamping unit is electrically connected to the first end of the charging and discharging capacitor and the drain of the first MOS transistor, respectively. The second end of the clamping unit is electrically connected to the positive terminal of the energy storage electrolytic capacitor and the second end of the first on / off control unit, respectively.

[0066] The clamping unit is used to transfer the energy corresponding to the spike voltage generated by the first MOSFET to the energy storage electrolytic capacitor for storage when the spike voltage generated by the first MOSFET exceeds the preset voltage.

[0067] The clamping unit is mainly used to control the voltage spike when it is too high under certain abnormal conditions, so as to prevent the excessively high voltage spike from damaging the relevant devices.

[0068] like Figure 2 As shown, in one embodiment, the clamping unit includes a bidirectional TVS tube, TVS1;

[0069] The first anode of the bidirectional TVS transistor TVS1 is electrically connected to the drain of the first MOS transistor Q3 and the first terminal of the charge / discharge capacitor C5, respectively. The second anode of the bidirectional TVS transistor TVS1 is electrically connected to the second terminal of the first on / off control unit (i.e., the cathode of the first diode D3; specifically, the second anode of the bidirectional TVS transistor TVS1 is electrically connected to the cathode of the first diode D3 through the discharge resistor R6) and the positive terminal of the energy storage electrolytic capacitor C7, respectively.

[0070] In this embodiment, the bidirectional TVS tube TVS1 can clamp the peak voltage to a safe range and prevent damage to related devices. In other embodiments, a unidirectional TVS tube can also be used.

[0071] by Figure 2 Taking the voltage control circuit shown as an example, the charging / discharging capacitor C5, the first diode D3, the bleeder resistor R6, and the energy storage electrolytic capacitor C7 constitute an RCD absorption module; the bidirectional TVS transistor TVS1 and the energy storage electrolytic capacitor C7 constitute a spike clamping module; and the charging / discharging capacitor C5, the first MOSFET Q3, and the second diode D5 constitute a discharge module. The specific circuit functions are as follows:

[0072] 1. When the first MOSFET Q3 is turned off, the parasitic inductance energy in the power circuit will generate a spike voltage Vds between the drain and source of the first MOSFET Q3. The energy current flows through the charging and discharging capacitor C5, the first diode D3, the bleeder resistor R6 to the energy storage electrolytic capacitor C7. Part of this energy is stored in the charging and discharging capacitor C5 and the energy storage electrolytic capacitor C7, and part of it is consumed in the bleeder resistor R6. The part of this energy transferred to the energy storage electrolytic capacitor C7 can be saved and sent to the output terminal.

[0073] 2. At the same time, when the peak voltage Vds of the first MOSFET Q3 is too high under certain abnormal conditions, it triggers the response of the bidirectional TVS transistor TVS1. Similarly, the energy flows through the bidirectional TVS transistor TVS1 to the energy storage electrolytic capacitor C7. Part of this energy is consumed in the bidirectional TVS transistor TVS1 and part is stored in the energy storage electrolytic capacitor C7. The part of the energy transferred to the energy storage electrolytic capacitor C7 can be saved and sent to the output terminal.

[0074] 3. When the next cycle begins (i.e. when the first MOSFET Q3 is turned on), the energy stored in the charging and discharging capacitor C5 will flow through the charging and discharging capacitor C5, the first MOSFET Q3, the second diode D5, and the charging and discharging capacitor C5. The energy stored in the charging and discharging capacitor C5 is consumed by the first MOSFET Q3.

[0075] Throughout the entire process, all the energy flowing through the energy storage electrolytic capacitor C7 can be stored and used at the output end, saving some of the energy lost due to the voltage clamping of the first MOSFET Q3 and improving the conversion efficiency of the synchronous rectifier switching power supply.

[0076] like Figure 3 As shown, in a second aspect, in one embodiment, this application provides a synchronous rectifier switching power supply, including a transformer, a second switching transistor (in this embodiment, the second switching transistor is a second MOSFET), a first switching transistor (in this embodiment, the first switching transistor is a first MOSFET), an energy storage electrolytic capacitor, and an inductor. The drain of the second MOSFET is electrically connected to the first terminal of the secondary winding of the transformer, the source of the second MOSFET is electrically connected to the first terminal of the inductor and the drain of the first MOSFET, the second terminal of the inductor is electrically connected to the positive terminal of the energy storage electrolytic capacitor, and the second terminal of the secondary winding of the transformer, the source of the first MOSFET, and the negative terminal of the energy storage electrolytic capacitor are grounded. The synchronous rectifier switching power supply further includes:

[0077] The spike voltage control circuit in any of the above embodiments;

[0078] The description of the peak voltage control circuit and its connection with the synchronous rectifier switching power supply can be found in the above embodiments, and will not be repeated here.

[0079] The aforementioned synchronous rectifier switching power supply includes a first on / off control unit and a second on / off control unit. The second terminal of the charging / discharging capacitor is electrically connected to the first terminal of the first on / off control unit and the second terminal of the second on / off control unit, respectively. The second terminal of the first on / off control unit is electrically connected to the positive terminal of the energy storage electrolytic capacitor of the synchronous rectifier switching power supply. The first terminal of the second on / off control unit is electrically connected to the source of the first MOSFET and the negative terminal of the energy storage electrolytic capacitor, respectively. By utilizing the on / off control capabilities of the first and second on / off control units for corresponding lines, the energy stored in the charging / discharging capacitor can be reliably transferred to the energy storage electrolytic capacitor for storage. The energy stored in the energy storage electrolytic capacitor can then be used to supply the output terminal of the synchronous rectifier switching power supply, thereby reducing energy loss and improving the conversion efficiency of the synchronous rectifier switching power supply.

[0080] like Figure 4 As shown, in one embodiment, the synchronous rectifier switching power supply further includes a first MOSFET driving circuit; the first MOSFET driving circuit includes:

[0081] NPN transistor Q4 and PNP transistor Q6;

[0082] The base of NPN transistor Q4 and the base of PNP transistor Q6 are connected to the control signal (i.e., SR_PWM), the collector of NPN transistor Q4 is connected to the working power supply signal (i.e. +12V), the emitter of NPN transistor Q4 is electrically connected to the gate of the first MOSFET Q3 and the collector of PNP transistor Q6, and the emitter of PNP transistor Q6 is grounded.

[0083] When the input SR_PWM is high, NPN transistor Q4 is turned on and PNP transistor Q6 is turned off. +12V passes through NPN transistor Q4 and resistor R9 to the gate of the first MOSFET Q3, thus driving Q3 to turn on. When the input SR_PWM is low, NPN transistor Q4 is turned off and PNP transistor Q6 is turned on. +12V cannot reach the gate of the first MOSFET Q3, so Q3 is turned off. When there is crosstalk signal in the circuit, it can also reach ground through resistor R12, diode D4, and PNP transistor Q6, thus preventing the first MOSFET Q3 from being falsely triggered. The resistance of resistor R16 is very large, for example, 20KΩ, to reduce the input impedance.

[0084] like Figure 4 As shown, in one embodiment, the first MOS transistor drive circuit further includes:

[0085] Filter capacitor C4;

[0086] The first terminal of the filter capacitor C4 is electrically connected to the collector of the NPN transistor Q4, and the second terminal of the filter capacitor C4 is grounded.

[0087] The +12V power supply signal may have AC crosstalk. When AC crosstalk occurs, it can be connected to ground through capacitor C4 to avoid false triggering of the first MOSFET Q3.

[0088] like Figure 4 As shown, the synchronous rectifier switching power supply also includes a second MOSFET driving circuit. The second MOSFET driving circuit includes a resistor R4. The first end of the resistor R4 is electrically connected to the third end (i.e., pin 5) of the secondary winding of the transformer T1. The second end of the resistor R4 is electrically connected to the gate of the second MOSFET Q1. The first end (i.e., pin 4) of the secondary winding of the transformer T1 is electrically connected to the drain of the second MOSFET Q1. The current induced in the portion of the secondary winding of the transformer T1 corresponding to the first end (i.e., pin 4) to the second end (i.e., pin 3) is output to the drain of the second MOSFET Q1. When the second MOSFET is turned on, it is output to the output terminal of the synchronous rectifier switching power supply. The current induced in the portion of the secondary winding of the transformer T1 corresponding to the third end (i.e., pin 5) to the second end (i.e., pin 3) is output to the gate of the second MOSFET Q1 through the resistor R4, so that the second MOSFET Q1 is turned on.

[0089] The synchronous rectified switching power supply also includes an absorption circuit, which consists of a diode D1, a capacitor C2, and a resistor R3. The first end of the resistor R3 is electrically connected to the third end (pin 5) of the secondary winding of the transformer T1 and the first end of the resistor R4. The second end of the resistor R3 is electrically connected to the cathode of the diode D1 and the first end of the capacitor C2. The anode of the diode D1 and the second end of the capacitor C2 are electrically connected to the second end of the resistor R4. This absorption circuit is used to absorb the leakage inductance spike voltage of the second MOSFET Q1.

[0090] The synchronous rectifier switching power supply also includes a bidirectional TVS transistor TVS2. The first anode of the bidirectional TVS transistor TVS2 is electrically connected to the drain of the second MOSFET Q1, and the second anode of the bidirectional TVS transistor TVS2 is electrically connected to the source of the second MOSFET Q1. The bidirectional TVS transistor TVS2 is used to clamp the voltage across the second MOSFET Q1 to prevent damage to the second MOSFET Q1.

[0091] The synchronous rectifier switching power supply also includes a capacitor C6 and a resistor R13. The first end of the capacitor C6 is electrically connected to the drain of the second MOSFET Q1, the second end of the capacitor C6 is electrically connected to the first end of the resistor R13, and the second end of the resistor R13 is electrically connected to the source of the second MOSFET Q1. The capacitor C6 and the resistor R13 are used to absorb the common-mode noise generated when the second MOSFET Q1 is turned off.

[0092] like Figure 4 As shown, the first end (pin 1) of the primary winding of transformer T1 is connected to the input power signal (V_Bulk), the second end (pin 2) of the primary winding of transformer T1 is electrically connected to the drain of MOSFET Q5, the source of MOSFET Q5 is grounded, and the gate of MOSFET Q5 is connected to the control signal (PWM2) through resistor R11. When the control signal PWM2 is high, MOSFET Q5 is turned on, and the power signal V_Bulk flows through the primary winding of transformer T1, MOSFET Q5 and then to ground.

[0093] The synchronous rectifier switching power supply also includes a diode D6 and a resistor R14. The cathode of the diode D6 is electrically connected to the first end of the resistor R11, and the anode of the diode D6 is electrically connected to the first end of the resistor R14. The second end of the resistor R14 is electrically connected to the second end of the resistor R11 and the gate of the MOSFET Q5. The diode D6 and the resistor R14 are connected in anti-parallel to suppress the parasitic conduction of the MOSFET Q5.

[0094] The synchronous rectifier switching power supply also includes a resistor R15. The first end of the resistor R15 is electrically connected to the gate of the MOSFET Q5, and the second end of the resistor R15 is grounded. The resistance value of the resistor R15 is relatively large, such as 20KΩ, in order to reduce the input impedance.

[0095] like Figure 4 As shown, the synchronous rectifier switching power supply also includes capacitor C1, Zener diode ZD1, resistor R1, resistor R2, resistor R7, diode D2, MOSFET Q2, and capacitor C3.

[0096] In this configuration, the cathode of Zener diode ZD1 and the first terminal of capacitor C1 are connected to the control signal (i.e., PWM1). The anode of Zener diode ZD1 and the second terminal of capacitor C1 are electrically connected to the first terminal of resistor R1. The second terminal of resistor R1 is electrically connected to the first terminal of resistor R2, the first terminal of resistor R7, and the gate of MOSFET Q2. The second terminal of resistor R2 is electrically connected to the anode of diode D2. The cathode of diode D2, the second terminal of resistor R7, and the source of MOSFET Q2 are grounded. The drain of MOSFET Q2 is electrically connected to the first terminal of capacitor C3. The second terminal of capacitor C3 is electrically connected to the drain of MOSFET Q5 and the second terminal (i.e., pin 2) of the primary winding of transformer T1.

[0097] The functions of capacitor C1, Zener diode ZD1, resistor R1, resistor R2, resistor R7, diode D2, MOSFET Q2, and capacitor C3 can be described in the above embodiment, and will not be repeated here.

[0098] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the detailed descriptions of other embodiments above, which will not be repeated here.

[0099] The above provides a detailed description of a peak voltage control circuit and a synchronous rectifier switching power supply provided in this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

[0100] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

Claims

1. A peak voltage control circuit, characterized in that, The spike voltage control circuit is used to control the spike voltage appearing on the first switching transistor in the synchronous rectified switching power supply; the spike voltage control circuit includes: The system includes a charging / discharging capacitor, a first on / off control unit, a second on / off control unit, and an energy-consuming unit. The first end of the charging and discharging capacitor is electrically connected to the first input terminal of the first switching transistor. The second end of the charging and discharging capacitor is electrically connected to the first end of the first on / off control unit and the second end of the second on / off control unit. The second end of the first on / off control unit is electrically connected to the positive terminal of the energy storage electrolytic capacitor of the synchronous rectifier switching power supply. The first end of the second on / off control unit is electrically connected to the second input terminal of the first switching transistor and the negative terminal of the energy storage electrolytic capacitor. The energy dissipation unit is connected in series between the second end of the charging and discharging capacitor and the positive terminal of the energy storage electrolytic capacitor. The charge-discharge capacitor is used to absorb and store the energy of the spike voltage generated when the first switch is turned off. The first on / off control unit is used to achieve unidirectional conduction from the first terminal to the second terminal of the first on / off control unit when the first switch is off, and the second on / off control unit is used to achieve unidirectional conduction from the first terminal to the second terminal of the second on / off control unit when the first switch is off, so as to transfer the energy stored in the charging / discharging capacitor to the energy storage electrolytic capacitor for storage when the first switch is off. The energy-consuming unit is used to consume a portion of the energy transferred from the charging and discharging capacitor to the energy storage electrolytic capacitor. The first on / off control unit includes a first diode, and the second on / off control unit includes a second diode; The anode of the first diode is electrically connected to the second terminal of the charging / discharging capacitor and the cathode of the second diode, respectively. The cathode of the first diode is electrically connected to the positive terminal of the energy storage electrolytic capacitor, and the anode of the second diode is electrically connected to the second terminal of the first switching transistor and the negative terminal of the energy storage electrolytic capacitor, respectively.

2. The spike voltage control circuit according to claim 1, characterized in that, The energy-consuming unit includes a discharge resistor; The discharge resistor is connected in series between the second terminal of the charge / discharge capacitor and the positive terminal of the energy storage electrolytic capacitor.

3. The spike voltage control circuit according to claim 1 or 2, characterized in that, The first end of the energy-consuming unit is electrically connected to the cathode of the first diode, and the second end of the energy-consuming unit is electrically connected to the positive electrode of the energy storage electrolytic capacitor.

4. The spike voltage control circuit according to claim 1, characterized in that, The peak voltage control circuit also includes: Clamping unit; The first end of the clamping unit is electrically connected to the first end of the charging and discharging capacitor and the first input terminal of the first switching transistor, respectively; the second end of the clamping unit is electrically connected to the positive terminal of the energy storage electrolytic capacitor and the cathode of the first diode, respectively. The clamping unit is used to transfer the energy corresponding to the peak voltage generated by the first switching transistor to the energy storage electrolytic capacitor for storage when the peak voltage generated by the first switching transistor exceeds a preset voltage.

5. The spike voltage control circuit according to claim 4, characterized in that, The clamping unit includes a bidirectional TVS tube; The first anode of the bidirectional TVS diode is electrically connected to the first input terminal of the first switching transistor and the first terminal of the charging / discharging capacitor, respectively. The second anode of the bidirectional TVS diode is electrically connected to the cathode of the first diode and the positive terminal of the energy storage electrolytic capacitor, respectively.

6. A synchronous rectified switching power supply, comprising a transformer, a second switching transistor, a first switching transistor, an energy storage electrolytic capacitor, and an inductor, wherein a first input terminal of the second switching transistor is electrically connected to a first terminal of the secondary winding of the transformer, a second input terminal of the second switching transistor is electrically connected to a first terminal of the inductor and a first input terminal of the first switching transistor, a second terminal of the inductor is electrically connected to the positive terminal of the energy storage electrolytic capacitor, and a second terminal of the secondary winding of the transformer, a first input terminal of the first switching transistor, and a negative terminal of the energy storage electrolytic capacitor are respectively grounded; characterized in that, The synchronous rectifier switching power supply also includes: The spike voltage control circuit according to any one of claims 1 to 5.

7. The synchronous rectifier switching power supply according to claim 6, characterized in that, The synchronous rectifier switching power supply also includes a first switching transistor driving circuit; The first switching transistor driving circuit includes: NPN transistors and PNP transistors; The base of the NPN transistor and the base of the PNP transistor are respectively connected to control signals, the collector of the NPN transistor is connected to the working power supply signal, the emitter of the NPN transistor is electrically connected to the control terminal of the first switch and the collector of the PNP transistor, and the emitter of the PNP transistor is grounded.

8. The synchronous rectifier switching power supply according to claim 7, characterized in that, The first switch driver circuit also includes: Filter capacitor; The first terminal of the filter capacitor is electrically connected to the collector of the NPN transistor, and the second terminal of the filter capacitor is grounded.

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