Switching power supply and power converter

Abstract

The utility model discloses a switching power supply and a power converter. The switching power supply comprises a transformer, a controller and a switching circuit, the switching circuit comprises at least two switching tubes which are connected in series; the first end of the primary winding of the transformer is connected with a direct-current source; the second end of the primary winding of the transformer is grounded through at least two switching tubes which are connected in series; a secondary winding of the transformer is used for supplying power to a load; the control end of the switching circuit is connected with the controller; the switching circuit further comprises absorption circuits corresponding to the switching tubes; the first end of the absorption circuit is connected with the drain electrode of the corresponding switch tube, and the second end of the absorption circuit is connected with the source electrode of the corresponding switch tube; the controller controls the on-off state of the at least two series-connected switch tubes. The plurality of switch tubes connected in series can divide the voltage, and the overheating and breakdown of the switch tubes caused by the reflection voltage and the peak voltage are avoided. And each switch tube adopts a switch tube with a common voltage-withstanding grade. And the absorption circuit balances the voltage of each switching tube and absorbs the voltage peak, thereby achieving a voltage-sharing effect.

Description

Technical Field

[0001] The present application relates to the field of power supply technology, and in particular to a switching power supply and a power converter. Background Art

[0002] In power converters, switching power supplies are often used as auxiliary power supplies to power the load. A switching power supply consists of a transformer and a switching transistor. Its operating principle is that the transformer stores energy when the switching transistor is on and releases the energy to the load when the switching transistor is off.

[0003] When the input voltage of the switching power supply is high, the voltage stress borne by the switching tube when it is turned off may exceed the tolerance range of the switching tube.

[0004] Therefore, it is necessary to provide a technical solution to ensure that the voltage borne by the switching tube of the switching power supply is lower than the voltage level of the switching tube. Utility Model Content

[0005] In view of this, the present application provides a switching power supply and a power converter, which can reduce the voltage borne by a single switching tube and can achieve voltage balancing of multiple switching tubes.

[0006] An embodiment of the present application provides a switching power supply, comprising: a transformer, a controller and a switching circuit; the switching circuit comprises at least two switching tubes connected in series; the first end of the primary winding of the transformer is used to connect to a DC source; the second end of the primary winding of the transformer is grounded through the at least two switching tubes connected in series; the secondary winding of the transformer is used to supply power to a load; the control end of the switching circuit is connected to the controller; the switching circuit further comprises: an absorption circuit corresponding to each of the switching tubes; the first end of the absorption circuit is connected to the drain of the corresponding switching tube, and the second end of the absorption circuit is connected to the source of the corresponding switching tube; the controller is used to control the switching state of the at least two switching tubes connected in series.

[0007] In one possible implementation, the absorption circuit includes: a first resistor and a first capacitor; the first end of the first resistor is connected to the drain of the corresponding switching tube; the second end of the first resistor is connected to the source of the corresponding switching tube; the first end of the first capacitor is connected to the drain of the corresponding switching tube; and the second end of the first capacitor is connected to the source of the corresponding switching tube.

[0008] In a possible implementation, the absorption circuit further includes: a first diode; an anode of the first diode is connected to the drain of the corresponding switching tube, and a cathode of the first diode is connected to the first end of the corresponding first capacitor.

[0009] A possible implementation, the switching circuit further includes: a delay circuit corresponding to each switching transistor; a first end of the delay circuit is connected to the gate of the corresponding switching transistor, and a second end of the delay circuit is connected to the controller.

[0010] A possible implementation, the delay circuit includes: a turn-on delay circuit and a turn-off delay circuit; the turn-on delay circuit includes: a second resistor and a second diode; a first end of the second resistor is connected to the gate of the corresponding switching transistor, and a second end of the second resistor is connected to the cathode of the second diode; the anode of the second diode is used to connect to the controller. The turn-off delay circuit includes: a third resistor and a third diode; a first end of the third resistor is connected to the gate of the corresponding switching transistor, and a second end of the third resistor is connected to the anode of the third diode; the cathode of the third diode is used to connect to the controller.

[0011] A possible implementation, the switching circuit includes three switching transistors connected in series as follows: a first switching transistor, a second switching transistor, and a third switching transistor; the drain of the first switching transistor is connected to the primary winding of the transformer; the source of the first switching transistor is connected to the drain of the second switching transistor; the source of the second switching transistor is connected to the drain of the third switching transistor; the source of the third switching transistor is grounded; the gates of the first switching transistor, the second switching transistor, and the third switching transistor are used to connect to the controller.

[0012] A possible implementation, the switching circuit includes two switching transistors connected in series as follows: a first switching transistor and a second switching transistor; the drain of the first switching transistor is connected to the primary winding of the transformer; the source of the first switching transistor is connected to the drain of the second switching transistor; the source of the second switching transistor is grounded; the gates of the first switching transistor and the second switching transistor are used to connect to the controller.

[0013] A possible implementation, the switching power supply is a flyback switching power supply.

[0014] A possible implementation, the transformer is a step-down transformer.

[0015] The embodiment of the present application further provides a power converter, including: a power conversion circuit and the switching power supply introduced above; one end of the switching power supply is connected to the power conversion circuit, and the other end of the switching power supply is used to connect to a load; the switching power supply is used to supply power to the load.

[0016] In the embodiments of the present application, a switching circuit composed of multiple switching tubes connected in series can effectively divide the voltage compared with a single switching tube used in a traditional switching power supply. Therefore, when the switching tube is turned off, overheating and breakdown of the switching tube caused by reflected voltage and spike voltage can be avoided. Such a design not only protects the safety of the switching tube, but also improves the overall safety and stability of the switching power supply. At the same time, since the switching tubes are configured in series, each switching tube does not need to select a model with a high withstand voltage rating, and only a switching tube with a common withstand voltage rating can be used. This configuration not only ensures the safety of the circuit, but also effectively reduces the cost of each switching tube. Moreover, in order to achieve voltage sharing among multiple series-connected switching tubes, an absorption circuit is configured for each switching tube to balance the voltage drop of each switching tube and absorb voltage spikes, so as to achieve voltage sharing and protect the switching tube. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic diagram of a switching power supply provided by an embodiment of the present application;

[0018] Figure 2 is a schematic diagram of a switching power supply with a rectifying circuit added provided by an embodiment of the present application;

[0019] Figure 3 is a schematic diagram of a switching circuit in a switching power supply provided by an embodiment of the present application;

[0020] Figure 4 is Figure 3 the simulation diagram of the voltage sharing waveform of each switching tube without considering the leakage inductance of the transformer shown in;

[0021] Figure 5 is Figure 3 the simulation diagram of the voltage sharing waveform of each switching tube considering the leakage inductance of the transformer shown in;

[0022] Figure 6 is a schematic diagram of another switching circuit in a switching power supply provided by an embodiment of the present application;

[0023] Figure 7 is a schematic diagram of still another switching circuit in a switching power supply provided by an embodiment of the present application;

[0024] Figure 8 is a schematic diagram of a power converter provided by an embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] In a switching power supply, the switching power supply is a common DC-DC power supply, which is widely used in low-power devices, isolated power supplies, multi-output power supplies, battery chargers and other scenarios, and has the advantages of simple structure, electrical isolation, wide input voltage range, etc. However, when the input voltage of the switching power supply is higher than a certain value, at the moment when the switching tube in the switching power supply is turned off, the reflected voltage and spike voltage generated by the secondary winding of the transformer in the switching power supply on the primary winding are superimposed on the input voltage, which will exceed the rated breakdown voltage of the switching tube and cause the switching tube to be damaged, such as breakdown.

[0026] The switching power supply provided by the embodiment of the present application includes a switching circuit, and the switching circuit includes a plurality of switching tubes connected in series. The plurality of switching tubes share the voltage jointly, preventing a single switching tube from being damaged by overvoltage, and improving the stability and safety of the switching power supply.

[0027] To make the above objects, features and advantages of the present application more obvious and understandable, the following further details the embodiments of the present application in conjunction with the drawings and specific embodiments.

[0028] See Figure 1 , which is a schematic diagram of a switching power supply provided by the embodiment of the present application.

[0029] The switching power supply provided by the embodiment of the present application includes: a transformer 100, a switching circuit 200 and a controller 300.

[0030] The transformer 100 includes: a primary winding P and a secondary winding S. It should be understood that the present application does not specifically limit the turns ratio of the primary winding P and the secondary winding S of the transformer. For example, when the switching power supply is applied to an auxiliary power supply scenario, the transformer is generally a step-down transformer, that is, the number of turns of the primary winding P is greater than the number of turns of the secondary winding S.

[0031] In order to better achieve voltage sharing for each switching tube to protect each switching tube in the switching circuit from overvoltage breakdown, the switching circuit provided by the embodiment of the present application adds an absorption circuit for each switching tube in the switching circuit. The first end of the absorption circuit is connected to the drain of the corresponding switching tube, and the second end of the absorption circuit is connected to the source of the corresponding switching tube; the present application does not specifically limit the implementation manner of the absorption circuit, which generally includes a resistor and a capacitor.

[0032] The switching circuit 200 includes N switching tubes, such as Figure 1 shown Q1, Q2, up to QN, where N is an integer greater than or equal to 2. The present application does not specifically limit the number of switching tubes in the switching circuit 200, and the specific number is determined according to the input voltage level and the breakdown voltage level of the switching tube model. For example, taking the switching circuit needing to withstand 2600V voltage as an example, 3 switching tubes with 950V can be selected for voltage sharing, or 2 switching tubes with 1500V can be selected for voltage sharing.

[0033] The embodiments of the present application do not specifically limit the type of the switching transistors in the switching circuit 200. For example, it may be a Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET), or it may be an Insulated Gate Bipolar Transistor (IGBT).

[0034] The first end A of the primary winding P of the transformer 100 is used to connect to a DC source. The second end B of the primary winding P of the transformer 100 is grounded through the switching circuit 200. The secondary winding S of the transformer 100 is used to supply power to a load. The control end of the switching circuit 200 is connected to the controller 300.

[0035] When the switching circuit 200 is turned on, it should be understood that the switching circuit 200 being turned on means that all the switching transistors in the switching circuit 200 are turned on, that is, a path is formed from the first end of the transformer to the ground. The input voltage passes through the primary winding P of the transformer 100, causing the primary winding P to generate a magnetic field and store energy. When the switching circuit 200 is turned off, the switching circuit 200 being turned off means that all the switching transistors in the switching circuit 200 are turned off. The current in the primary winding P of the transformer 100 decreases, and the energy in the primary winding P is transferred to the secondary winding S through coupling. The secondary winding S releases the energy to supply power to the load.

[0036] The controller 300 is used to control the on / off state of the switching transistors in the switching circuit 200. For example, in a possible implementation, the controller 300 outputs a driving signal to the switching circuit, and the driving signal can be a high or low level. Specifically, when the controller 300 outputs a high level to the switching circuit 200, all the switching transistors Q1 to QN in the switching circuit 200 are turned on. When the controller 300 outputs a low level to the switching circuit 200, all the switching transistors Q1 to QN in the switching circuit are turned off. It should be understood that the controller 300 generating the driving signal is a mature technology and will not be explained in detail here.

[0037] The working principle of the switching power supply provided by the embodiments of the present application will be introduced below in combination with specific values. In a possible implementation, the switching power supply is a flyback switching power supply. It should be understood that the switching power supply can also be a forward switching power supply. Only the flyback switching power supply is taken as an example for introduction below.

[0038] The turns ratio of the primary winding P and the secondary winding S of the transformer 100 is 16:1, and the drive signal generated by the controller 300 is a Pulse Width Modulation (PWM) wave. At this time, assuming the input voltage is 2000V, the output voltage is 25V. At this time, the reflected voltage generated by the secondary winding S on the primary winding P is 16 * 25V. Assuming the spike voltage at the moment when the switching circuit 200 is turned off is 200V, the voltage across the switching circuit 200 is 2600V, and the voltage divided by each switching transistor alone is 2600 / NV. Since the switching circuit 200 is used to replace a single switching transistor, the switching circuit 200 will not be broken down by the high voltage of 2600V, thereby improving the overall stability and safety of the flyback switching power supply.

[0039] The switching circuit in the switching power supply provided by the embodiment of the present application includes a plurality of switching transistors connected in series. Compared with a single switching transistor in a traditional switching power supply, the plurality of switching transistors connected in series can divide the voltage, thereby preventing the switching transistor from overheating and breakdown caused by the reflected voltage and the spike voltage at the moment of turning off, protecting the safety of the switching transistor, and improving the overall safety and stability of the switching power supply. At the same time, since a plurality of switching transistors are connected in series, each switching transistor does not need to use a switching transistor with a high withstand voltage rating, and a switching transistor with a normal withstand voltage can be selected, which can reduce the cost of a single switching transistor. Moreover, in order to achieve voltage sharing among the plurality of series-connected switching transistors, an absorption circuit is also configured for each switching transistor to balance the voltage drop of each switching transistor and absorb the voltage spike to achieve three-transistor voltage sharing and protect the switching transistor.

[0040] See Figure 2 , which is a schematic diagram of another switching power supply provided by the embodiment of the present application.

[0041] The switching power supply provided by the embodiment of the present application is equivalent to Figure 1 In terms of, it also includes a rectifier circuit. The embodiment of the present application does not specifically limit the specific form of the rectifier circuit. For example, it can be a bridge arm circuit or only include a diode. The rectifier circuit is connected to the secondary winding of the transformer, and the output of the secondary winding is rectified by the rectifier circuit into direct current to supply power to the load. [[ID=I4]]

[0042] In the embodiment of the present application, the rectifier circuit including the diode D1 is taken as an example for introduction. In the embodiment of the present application, a capacitor C1 is added after the rectifier circuit for filtering and voltage stabilization.

[0043] The first end of the diode D1 is used to connect the first end C of the secondary winding of the transformer, and the second end of the diode D1 is connected to the first end of the capacitor C1. The second end of the capacitor C1 is connected to the second end of the secondary winding of the transformer.

[0044] The embodiments of the present application do not specifically limit the conduction voltage drop of diode D1 and the capacitance value of capacitor C1. It should be understood that the conduction voltage drop of diode D1 and the capacitance value of capacitor C1 are determined according to specific load requirements. Determining the conduction voltage drop of diode D1 and the capacitance value of capacitor C1 is a mature technology, and the embodiments of the present application will not explain it in detail.

[0045] In a possible implementation, the transformer is a step-down transformer. When the switching circuit is turned on, diode D1 is turned off, and no current passes through the secondary winding of the transformer. When the switching circuit is turned off instantaneously, the voltage polarity of the secondary winding of the transformer is reversed, diode D1 is turned on, and after being filtered by capacitor C1, a smooth voltage is output to the load. At the same time, capacitor C1 stores energy at this time. When the switching circuit is turned on again, diode D1 is turned off again, and at this time, capacitor C1 supplies power to the load.

[0046] See Figure 3 , which is a schematic diagram of a switching circuit provided by the embodiments of the present application.

[0047] In order to better achieve the equal voltage sharing of each switching tube to protect each switching tube in the switching circuit from overvoltage breakdown, the switching circuit provided by the embodiments of the present application, as Figure 3 shown, relative to Figure 1 and Figure 2 , an absorption circuit and a delay circuit are added to each switching tube in the switching circuit. Figure 3 In

[0048] RS is a current detection resistor. The selection of the resistance value of RS and its working principle are mature technologies, and the embodiments of the present application will not explain it in detail.

[0048] To better enable those skilled in the art to understand Figure 3 the absorption circuit and the delay circuit in

[0049] the embodiments of the present application provide a possible implementation. According to the general usage scenario of the switching power supply, this implementation selects the following example where the switching circuit includes the following three switching tubes, namely the first switching tube Q1, the second switching tube Q2, and the third switching tube Q3 for introduction. It should be understood that the driving signal phases of the first switching tube Q1, the second switching tube Q2, and the third switching tube Q3 are the same, and the amplitudes are the same.

[0049] The purpose of the absorption circuit provided by the embodiments of the present application is to balance the voltage drops of each switching tube and absorb voltage spikes to achieve equal voltage sharing among the three tubes and protect the switching tubes.

[0050] The snubber circuit corresponding to the first switching transistor Q1 includes: a first resistor R11, a first capacitor C11, and a first diode D11. The anode of the first diode D11 is connected to the drain of the switching transistor Q1. The first end of the first resistor R11 is connected to the cathode of the first diode D11. The second end of the first resistor R11 is connected to the source of the switching transistor Q1. The first end of the first capacitor C11 is connected to the cathode of the first diode D11. The second end of the first capacitor C11 is connected to the source of the corresponding switching transistor Q1.

[0051] The snubber circuit corresponding to the second switching transistor Q2 includes: a first resistor R21, a first capacitor C21, and a first diode D21. The anode of the first diode D21 is connected to the drain of the switching transistor Q2. The first end of the first resistor R21 is connected to the cathode of the first diode D21. The second end of the first resistor R21 is connected to the source of the switching transistor Q2. The first end of the first capacitor C21 is connected to the cathode of the first diode D21. The second end of the first capacitor C21 is connected to the source of the corresponding switching transistor Q2.

[0052] The snubber circuit corresponding to the third switching transistor Q3 includes: a first resistor R31, a first capacitor C31, and a first diode D31. The anode of the first diode D31 is connected to the drain of the switching transistor Q3. The first end of the first resistor R31 is connected to the cathode of the first diode D31. The second end of the first resistor R31 is connected to the source of the switching transistor Q3. The first end of the first capacitor C31 is connected to the cathode of the first diode D31. The second end of the first capacitor C31 is connected to the source of the corresponding switching transistor Q3.

[0053] The following introduces the specific working principle of the snubber circuit.

[0054] When Q1, Q2, and Q3 are turned off, the reflected voltage and voltage spike generated by the secondary winding of the transformer forward bias and turn on D11, D21, and D31, and the current flows into the snubber circuit. R11, R21, and R31 are used to limit the current magnitude and balance the voltage drops of each switching transistor, and C11, C21, and C31 are used to absorb the voltage spike, so that the voltage fluctuations are consistent when the switching transistor is turned on or off. The diode, capacitor, and resistor work together to achieve uniform voltage division among the three switching transistors when the switching transistor is turned off, avoiding overvoltage breakdown of the switching transistor. If the voltage of a certain switching transistor is relatively high, the resistance value of the resistor corresponding to this switching transistor can be reduced to balance the voltage. If the voltage fluctuation of a certain switching transistor is relatively large, the capacitance value of the capacitor corresponding to this switching transistor can be increased to reduce the voltage fluctuation.

[0055] The purpose of the delay circuit provided in the embodiment of the present application is to control the turn-on delay and turn-off delay of the switching transistor to achieve equal voltage among the three transistors and protect the switching transistor.

[0056] The delay circuit corresponding to the first switching transistor Q1 includes: a turn-on delay circuit and a turn-off delay circuit.

[0057] The turn-on delay circuit includes: a second resistor R12 and a second diode D12. The first end of the second resistor R12 is connected to the gate of the switching transistor Q1, and the second end of the second resistor R12 is connected to the cathode of the second diode D12. The anode of the second diode D12 is used to connect to the controller.

[0058] The turn-off delay circuit includes: a third resistor R13 and a third diode D13. The first end of the third resistor R13 is connected to the gate of the switching transistor Q1, and the second end of the third resistor R13 is connected to the anode of the third diode D13. The cathode of the third diode D13 is used to connect to the controller.

[0059] The delay circuit corresponding to the second switching transistor Q2 includes: a turn-on delay circuit and a turn-off delay circuit.

[0060] The turn-on delay circuit includes: a second resistor R22 and a second diode D22. The first end of the second resistor R22 is connected to the gate of the switching transistor Q2, and the second end of the second resistor R22 is connected to the cathode of the second diode D22. The anode of the second diode D22 is used to connect to the controller.

[0061] The turn-off delay circuit includes: a third resistor R23 and a third diode D23. The first end of the third resistor R23 is connected to the gate of the switching transistor Q2, and the second end of the third resistor R23 is connected to the anode of the third diode D23. The cathode of the third diode D23 is used to connect to the controller.

[0062] The delay circuit corresponding to the third switching transistor Q3 includes: a turn-on delay circuit and a turn-off delay circuit.

[0063] The turn-on delay circuit includes: a second resistor R32 and a second diode D32. The first end of the second resistor R32 is connected to the gate of the switching transistor Q3, and the second end of the second resistor R32 is connected to the cathode of the second diode D32. The anode of the second diode D32 is used to connect to the controller.

[0064] The turn-off delay circuit includes: a third resistor R33 and a third diode D33. The first end of the third resistor R33 is connected to the gate of the switching transistor Q3, and the second end of the third resistor R33 is connected to the anode of the third diode D33. The cathode of the third diode D33 is used to connect to the controller.

[0065] The following describes the specific working principle of the delay circuit.

[0066] A possible implementation of a delay circuit. Taking R12, D12, R13, D13, and Q1 as examples, when the drive signal generated by the controller is at a high level, D12 conducts, D13 cuts off, and Q1 conducts. When the drive signal generated by the controller is at a low level, D12 cuts off, D13 conducts, and Q1 cuts off. D12 and D13 ensure the directionality of the drive signal generated by the controller. When Q1 needs to conduct, D12 is forward-biased, allowing the drive signal to pass through. When Q1 needs to turn off, D13 is forward-biased, providing a discharge path for the gate charge. When Q1 needs to conduct, R12 limits the drive current to prevent excessive gate current. When Q1 needs to turn off, the gate charge discharges through R13.

[0067] By fine-tuning the resistance value of R12, the turn-on delay of the switching transistor Q1 can be adjusted. If it is necessary to increase the turn-on delay of the switching transistor Q1, the resistance value of R12 is increased. If it is necessary to decrease the turn-on delay of the switching transistor Q1, the resistance value of R12 is decreased.

[0068] By fine-tuning the resistance value of R13, the turn-off delay of the switching transistor Q1 can be adjusted. If it is necessary to increase the turn-off delay of the switching transistor Q1, the resistance value of R13 is increased. If it is necessary to decrease the turn-off delay of the switching transistor Q1, the resistance value of R13 is decreased.

[0069] The working principle and adjustment method of the switching transistor Q2 and the delay circuit corresponding to the switching transistor Q2 are the same as those of the switching transistor Q1 and the delay circuit corresponding to the switching transistor Q1. The embodiments of the present application will not be explained in detail.

[0070] The working principle and adjustment method of the switching transistor Q3 and the delay circuit corresponding to the switching transistor Q3 are the same as those of the switching transistor Q1 and the delay circuit corresponding to the switching transistor Q1. The embodiments of the present application will not be explained in detail.

[0071] The switching circuit provided by the embodiments of the present application uses multiple switching transistors for balanced voltage division, avoiding the risk of overvoltage breakdown of a single switching transistor in a traditional switching power supply. At the same time, by adjusting the values of the resistors and capacitors in the absorption circuit, balanced voltage division of each switching transistor can be achieved, thereby improving the overall stability and safety of the switching power supply. The delay circuit provided by the embodiments of the present application can control the turn-on delay and turn-off delay of the switching transistor by adjusting the resistance value. While ensuring that the switching transistor obtains the correct drive signal, it prevents excessive current in the switching transistor, thereby improving the overall stability and safety of the switching power supply.

[0072] For the voltage equalization effect of the first switching transistor Q1, the second switching transistor Q2, and the third switching transistor Q3, please refer to Figure 4 and Figure 5 . Figure 4 is the simulation waveform of the voltage across a single switching transistor when the leakage inductance of the transformer is not considered. Figure 5The simulation waveform of the voltage across a single switch when considering the leakage inductance of the transformer Figure 4 and Figure 5 The abscissa is time and the ordinate is the voltage amplitude.

[0073] Figure 4 The simulation waveform in [reference] shows that without considering the leakage inductance of the transformer, by connecting three switches in series, the voltage is evenly distributed, and each switch only bears one-third of the total voltage, fluctuating around 800V, which greatly reduces the voltage stress on each switch. The voltage division design reduces the peak voltage and stress borne by the switch, reduces the breakdown risk, and improves the overall reliability and stability of the switching power supply.

[0074] Figure 5 The simulation waveform in [reference] shows that when considering the leakage inductance of the transformer, although a spike voltage of about 400V will be generated additionally at the moment when the switch is turned off, it still does not exceed the withstand voltage level of a single switch. After the spike voltage is absorbed, the voltage amplitude drops back to about 800V. The voltage division design reduces the peak voltage and stress borne by the switch, reduces the breakdown risk, and improves the overall reliability and stability of the switching power supply.

[0075] See Figure 6 , which is a schematic diagram of a switching circuit provided by an embodiment of the present application. Compared with Figure 3 , when a single switch is not sufficient to withstand the sum of the reflected voltage, spike voltage and input voltage when turned off, but the sum of the withstand voltage levels of the three switches exceeds the sum of the reflected voltage, spike voltage and input voltage, two switches with appropriate withstand voltage levels can be selected for voltage sharing.

[0076] The switching circuit provided by the embodiment of the present application includes, in addition to Q1 and Q2, a delay circuit and an absorption circuit corresponding to Q1, and a delay circuit and an absorption circuit corresponding to Q2. In addition, the switching circuit also includes a current detection resistor RS.

[0077] For the working principles and advantages of each delay circuit and each absorption circuit provided by the embodiment of the present application, see the description in Figure 3 , which will not be elaborated here.

[0078] See Figure 7 , which is a schematic diagram of a switching circuit provided by an embodiment of the present application. Compared with Figure 3 , when the three switches are not sufficient to withstand the sum of the reflected voltage, spike voltage and input voltage, the number of switches can be increased and multiple switches can be used for voltage sharing.

[0079] In addition to including Q1, Q2 to QN, the switching circuit provided by the embodiment of the present application further includes a delay circuit and an absorption circuit corresponding to Q1, a delay circuit and an absorption circuit corresponding to Q2, and a delay circuit and an absorption circuit corresponding to QN. In addition, the switching circuit further includes a current detection resistor RS. Wherein N is a positive integer greater than or equal to 3. For example, N can be 4 or 5.

[0080] For the working principles and advantages of each delay circuit and each absorption circuit provided by the embodiment of the present application, refer to Figure 3 the description, which will not be elaborated here.

[0081] Refer to Figure 8 , which is a schematic diagram of a power converter provided by the embodiment of the present application.

[0082] The power converter includes: a power conversion circuit 801 and the switching power supply 800 introduced in the above embodiment.

[0083] One end of the switching power supply 800 is connected to the power conversion circuit 801, and the other end of the switching power supply 800 is used to connect to a load; the switching power supply 800 is used to supply power to the load.

[0084] Among them, the load can be at least one of the control circuit of the power conversion circuit 801 and the temperature control component in the power converter. It should be understood that the switching power supply 800 can supply power only to the control circuit of the power conversion circuit 801, or only to the temperature control component in the power converter, or can supply power to the control circuit of the power conversion circuit 801 and the temperature control component in the power converter at the same time. The embodiment of the present application does not specifically limit the specific type of the temperature control component. For example, it can include at least one of the following: a fan, a heater or a water pump. The fan is used for air cooling, and the water pump is used for water cooling. The heater can be a heating resistance wire, etc., and is used to heat when the power conversion circuit starts in a low-temperature environment.

[0085] The embodiment of the present application uses the switching power supply described above, preventing the switching power supply of the power converter from being damaged due to overvoltage breakdown, and thus improving the overall stability and safety of the power converter.

[0086] It should be noted that the various embodiments in this specification are described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. The same or similar parts among the various embodiments can be referred to each other. For the system or 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 be referred to the description of the method part.

[0087] The foregoing description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A switching power supply, characterized in that, Comprising: A transformer, a controller, and a switching circuit; the switching circuit includes at least two series-connected switching tubes; The first end of the primary winding of the transformer is used to connect to a DC source; The second end of the primary winding of the transformer is grounded through the at least two series-connected switching tubes; the secondary winding of the transformer is used to supply power to a load; The control end of the switching circuit is connected to the controller; the switching circuit further includes: a snubber circuit corresponding to each switching tube; the first end of the snubber circuit is connected to the drain of the corresponding switching tube, and the second end of the snubber circuit is connected to the source of the corresponding switching tube; The controller is used to control the switching states of the at least two series-connected switching tubes.

2. The switching power supply according to claim 1, wherein The snubber circuit includes: a first resistor and a first capacitor; the first end of the first resistor is connected to the drain of the corresponding switching tube; the second end of the first resistor is connected to the source of the corresponding switching tube; the first end of the first capacitor is connected to the drain of the corresponding switching tube; the second end of the first capacitor is connected to the source of the corresponding switching tube.

3. The switching power supply according to claim 2, wherein The snubber circuit further includes: a first diode; the anode of the first diode is connected to the drain of the corresponding switching tube, and the cathode of the first diode is connected to the first end of the corresponding first capacitor.

4. The switching power supply according to any one of claims 1-3, characterized in that The switching circuit further includes: a delay circuit corresponding to each switching tube; the first end of the delay circuit is connected to the gate of the corresponding switching tube, and the second end of the delay circuit is connected to the controller.

5. The switching power supply according to claim 4, wherein The delay circuit includes: a turn-on delay circuit and a turn-off delay circuit; the turn-on delay circuit includes: a second resistor and a second diode; the first end of the second resistor is connected to the gate of the corresponding switching tube, and the second end of the second resistor is connected to the cathode of the second diode; the anode of the second diode is used to connect to the controller. The turn-off delay circuit includes: a third resistor and a third diode; the first end of the third resistor is connected to the gate of the corresponding switching tube, and the second end of the third resistor is connected to the anode of the third diode; the cathode of the third diode is used to connect to the controller.

6. The switching power supply according to claim 5, characterized in that, The switching circuit includes the following three series-connected switching tubes: a first switching tube, a second switching tube, and a third switching tube; the drain of the first switching tube is connected to the primary winding of the transformer; the source of the first switching tube is connected to the drain of the second switching tube; the source of the second switching tube is connected to the drain of the third switching tube; the source of the third switching tube is grounded; the gates of the first switching tube, the second switching tube, and the third switching tube are used to connect to the controller.

7. The switching power supply according to claim 5, characterized in that, The switching circuit includes the following two series-connected switching tubes: a first switching tube and a second switching tube; the drain of the first switching tube is connected to the primary winding of the transformer; the source of the first switching tube is connected to the drain of the second switching tube; the source of the second switching tube is grounded; the gates of the first switching tube and the second switching tube are used to connect to the controller.

8. The switching power supply according to claim 5, wherein, The switching power supply is a flyback switching power supply.

9. The switching power supply according to claim 8, wherein The transformer is a step-down transformer.

10. A power converter, characterized in that, Comprising: A power conversion circuit and the switching power supply according to any one of claims 1-9 One end of the switching power supply is connected to the power conversion circuit, and the other end of the switching power supply is used to be connected to a load; The switching power supply is used to supply power to the load.

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