A protection device, method and electric vehicle for a flyback switching power supply

Abstract

The application discloses a protection device of a flyback switching power supply, an electric automobile and a protection method of the flyback switching power supply of the electric automobile. The device comprises a control module. In the case that the voltage of the output side of the secondary winding of a transformer module is received, if it is determined that the voltage of the output side of the secondary winding of the transformer module is not within a set voltage range, it is considered that the bus DC voltage of the flyback switching power supply appears fluctuation voltage or surge voltage, a control signal is sent to control the closing of a switching module; in the case that the control signal is received, the switching module is closed to connect an absorption branch, the fluctuation voltage or the surge voltage is absorbed by an absorption module, and the protection of an output rectifier diode module is realized. According to the scheme, when the fluctuation voltage or the surge voltage is detected at the output side of the secondary winding of the high-frequency transformer in the flyback switching power supply, the absorption branch is used for absorption, so that the output rectifier diode is protected in advance to avoid breakdown.

Description

Technical Field

[0001] This invention belongs to the field of switching power supply technology, specifically relating to a protection device and method for a flyback switching power supply, and an electric vehicle having the protection device for the flyback switching power supply. In particular, it relates to a breakdown protection circuit and control method for the output rectifier diode of a flyback switching power supply in an electric vehicle, and an electric vehicle having the breakdown protection circuit. Background Technology

[0002] The input voltage of the flyback switching power supply of the internal controller of household appliances is generally in the range of AC 85V-AC265V. When supplying power, it usually needs to be filtered and then rectified into 310V DC. Then, after passing through a high-frequency transformer and an output rectifier diode, the voltage is converted to obtain one or more low-voltage DC power supplies to the required low-voltage DC load.

[0003] When the input voltage is low, the output voltage of the rectifier diode is also at a low level, and there will be no damage to the output rectifier diode. However, when the input voltage is a DC voltage of several hundred volts (i.e., high voltage DC voltage), the controller may be damaged. For example, the high voltage DC voltage in electric vehicles may experience instantaneous fluctuations or high surge voltage impacts during driving in harsh environments or at the moment of power-on. This often leads to the breakdown and short circuit of the output rectifier diode, resulting in damage and failure of the controller board.

[0004] The above content is only used to help understand the technical solution of the present invention and does not represent an admission that the above content is prior art. Summary of the Invention

[0005] The purpose of this invention is to provide a protection device for a flyback switching power supply, and a protection method for an electric vehicle and its flyback switching power supply. This addresses the problem that when the input voltage of the flyback switching power supply in the internal controller of a household appliance is high-voltage DC, instantaneous fluctuations or high surge voltage impacts on the bus DC voltage may occur under harsh operating conditions or at the moment of power-on. This can lead to short circuits and damage to the rectifier diodes on the output side of the flyback switching power supply, resulting in controller board failure. The invention achieves this by setting an absorption branch and a voltage detection module on the output side of the secondary winding of the high-frequency transformer in the flyback switching power supply. When fluctuations or surge voltages are detected on the output side of the secondary winding of the high-frequency transformer in the flyback switching power supply, the absorption branch absorbs the fluctuations or surge voltages, thus protecting the output rectifier diodes from breakdown in advance. This improves the timeliness and reliability of the protection for the flyback switching power supply.

[0006] This invention provides a protection device for a flyback switching power supply. The flyback switching power supply includes a transformer module and an output rectifier diode module. The protection device for the flyback switching power supply includes an absorption branch, a voltage detection module, and a control module. The absorption branch includes an absorption module and a switching module. A DC input voltage is input to the primary winding of the transformer module. The output side of the secondary winding of the transformer module outputs a DC voltage after passing through the output rectifier diode module. The absorption branch is located on the output side of the secondary winding of the transformer module, connected in parallel with the output rectifier diode module, and located at the front end of the output rectifier diode module. The switching module is in a default off state. The voltage detection module is located on the transformer... The output side of the secondary winding of the transformer module, located at the front end of the output rectifier diode module, is used to detect the voltage on the output side of the secondary winding of the transformer module. The control module, upon receiving the voltage on the output side of the secondary winding of the transformer module, if it determines that the voltage on the output side of the secondary winding of the transformer module is outside a set voltage range, considers that the DC bus voltage of the flyback switching power supply has fluctuated or surged, and issues a control signal to control the closing of the switching module. The switching module, upon receiving the control signal, closes itself to connect the absorption branch, allowing the absorption module to absorb the fluctuating or surged voltage, thereby protecting the output rectifier diode module.

[0007] In some embodiments, the absorption module includes a varistor module; the switching module includes a relay module; wherein, on the output side of the secondary winding of the transformer module, the same-name terminal of the secondary winding of the transformer module is connected to the opposite-name terminal of the secondary winding of the transformer module via the varistor and the normally open contact of the relay module; the same-name terminal of the secondary winding of the transformer module is also connected to the anode of the output rectifier diode module; the cathode of the output rectifier diode module is connected to the first connection terminal of the DC voltage output terminal of the flyback switching power supply; the opposite-name terminal of the secondary winding of the transformer module is also connected to the second connection terminal of the DC voltage output terminal of the flyback switching power supply; the second connection terminal of the DC voltage output terminal of the flyback switching power supply is grounded.

[0008] In some embodiments, the system further includes an output filtering module; wherein the output filtering module is disposed between the cathode of the output rectifier diode module and the second connection terminal of the DC voltage output terminal of the flyback switching power supply, and is used to rectify and filter the voltage on the output side of the secondary winding of the transformer module before outputting it.

[0009] In some embodiments, the system further includes an input filtering module; wherein the input filtering module is located between the input terminal of the DC input voltage and the input side of the primary winding of the transformer module, and is disposed between the input terminal of the DC input voltage and ground, for filtering the DC input voltage before inputting it to the input side of the primary winding of the transformer module.

[0010] In some embodiments, the system further includes: a sampling module, a voltage regulator module, an optocoupler module, a switching power supply chip, and a clamping protection module; wherein, the sampling module is disposed at the output terminal of the flyback switching power supply and is used to sample the output DC voltage of the flyback switching power supply; the voltage regulator module is disposed between the sampling module and the optocoupler module and is used to perform voltage division based on the sampled output DC voltage of the flyback switching power supply to extract the divided voltage; and to set the reference voltage of the optocoupler module based on the extracted divided voltage to determine the forward voltage drop of the diode in the optocoupler module; the optocoupler module is disposed on the output side of the voltage regulator module and is respectively connected to the switching power supply chip and the transformer. The input side of the primary winding of the power supply module is used to provide control current to the control terminal of the MOSFET in the power supply chip. The power supply chip is located between the optocoupler module and the clamping protection module. When the sampled output DC voltage of the flyback power supply is greater than the sum of the forward voltage drop of the diode in the optocoupler module and the voltage drop across the sampling module, the control terminal of the MOSFET in the power supply chip provides control current. As the emitter current of the transistor in the optocoupler module increases, the duty cycle of the MOSFET in the power supply chip decreases, thereby reducing the output DC voltage of the flyback power supply and achieving clamping protection for the output DC voltage of the flyback power supply.

[0011] In some embodiments, the system further includes: a sampling module, a voltage regulator module, an optocoupler module, a switching power supply chip, and a clamping protection module; wherein, the sampling module is disposed at the output terminal of the flyback switching power supply and is used to sample the output DC voltage of the flyback switching power supply; the voltage regulator module is disposed between the sampling module and the optocoupler module and is used to perform voltage division based on the sampled output DC voltage of the flyback switching power supply to extract the divided voltage; and to set the reference voltage of the optocoupler module based on the extracted divided voltage to determine the forward voltage drop of the diode in the optocoupler module; the optocoupler module is disposed on the output side of the voltage regulator module and is respectively connected to the switching power supply chip and the transformer. The input side of the primary winding of the power supply module is used to provide control current to the control terminal of the MOSFET in the power supply chip. The power supply chip is located between the optocoupler module and the clamping protection module. When the sampled output DC voltage of the flyback power supply is greater than the sum of the forward voltage drop of the diode in the optocoupler module and the voltage drop across the sampling module, the control terminal of the MOSFET in the power supply chip provides control current. As the emitter current of the transistor in the optocoupler module increases, the duty cycle of the MOSFET in the power supply chip decreases, thereby reducing the output DC voltage of the flyback power supply and achieving clamping protection for the output DC voltage of the flyback power supply.

[0012] In conjunction with the above-described device, the present invention further provides an electric vehicle, including: the protection device for the flyback switching power supply described above.

[0013] In conjunction with the aforementioned electric vehicle, this invention further provides a protection method for a flyback switching power supply in an electric vehicle, comprising: detecting the voltage on the output side of the secondary winding of the transformer module; upon receiving the voltage on the output side of the secondary winding of the transformer module, if it is determined that the voltage on the output side of the secondary winding of the transformer module is not within a set voltage range, then it is considered that the DC bus voltage of the flyback switching power supply has fluctuated voltage or surge voltage, and a control signal is issued to control the switching module to close; upon receiving the control signal, the switching module itself closes to connect the absorption branch, so that the absorption module absorbs the fluctuating voltage or surge voltage, thereby protecting the output rectifier diode module.

[0014] In some embodiments, the method further includes: sampling the output DC voltage of the flyback switching power supply; performing voltage division based on the sampled output DC voltage of the flyback switching power supply to extract the divided voltage; setting a reference voltage for the optocoupler module based on the extracted divided voltage to determine the forward voltage drop of the diode in the optocoupler module; providing control current to the control terminal of the MOSFET in the switching power supply chip through the optocoupler module; when the sampled output DC voltage of the flyback switching power supply is greater than the sum of the forward voltage drop of the diode in the optocoupler module and the voltage drop across the sampling module, the control current provided by the control terminal of the MOSFET in the switching power supply chip increases with the current at the emitter of the transistor in the optocoupler module, thereby reducing the duty cycle of the MOSFET in the switching power supply chip, so as to reduce the output DC voltage of the flyback switching power supply, thereby achieving clamping protection of the output DC voltage of the flyback switching power supply.

[0015] Therefore, the solution of this invention involves setting an absorption branch and a voltage detection module on the output side of the secondary winding of the high-frequency transformer in the flyback switching power supply, and at the front end of the output rectifier diode. This absorption branch is connected in parallel with the output rectifier diode. The absorption branch includes an absorption module (such as a varistor RV) and a switching module (such as a relay K1), with the switching module defaulting to an open state. When the flyback switching power supply is operating, the voltage on the output side of the secondary winding of the high-frequency transformer is detected by the voltage detection module, and the main chip MCU determines whether the voltage is within a set voltage range. If not, the voltage is considered to be within the set range. The voltage detected by the detection module is a surge voltage. The main chip MCU controls the closing of the switch module so that the absorption module can absorb the fluctuating voltage or surge voltage, thereby protecting the output rectifier diode. Thus, by setting an absorption branch and a voltage detection module on the output side of the secondary winding of the high-frequency transformer in the flyback switching power supply, when a fluctuating voltage or surge voltage is detected on the output side of the secondary winding of the high-frequency transformer in the flyback switching power supply, the absorption branch is used to absorb the fluctuating voltage or surge voltage, thereby protecting the output rectifier diode from breakdown in advance and improving the timeliness and reliability of the protection for the flyback switching power supply.

[0016] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention.

[0017] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a structure of an embodiment of the protection device for the flyback switching power supply of the present invention;

[0019] Figure 2 A schematic diagram of an embodiment of a flyback switching power supply output rectifier diode breakdown protection circuit;

[0020] Figure 3 A schematic diagram of another embodiment of the anti-breakdown circuit for the output rectifier diode of a flyback switching power supply;

[0021] Figure 4 This is a schematic flowchart of an embodiment of the protection method for a flyback switching power supply of the present invention;

[0022] Figure 5 This is a flowchart illustrating an embodiment of the method of the present invention for clamping and protecting the output DC voltage of the flyback switching power supply.

[0023] Figure 6 This is a schematic diagram of the experimental data table;

[0024] Figure 7 This is a schematic diagram of a defective diode wafer.

[0025] Figure 8 This is a schematic diagram of a transistor-controlled relay circuit. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0027] Considering that the input voltage of the flyback switching power supply in the internal controller of household appliances is high-voltage DC, under harsh operating conditions or at the moment of power-on, the DC bus voltage may experience momentary fluctuations or high surge voltage impacts, which can cause the rectifier diodes on the output side of the flyback switching power supply to break down and short-circuit, leading to damage and failure of the controller board. Related solutions involve adding protective devices at the power input front end of the flyback switching power supply for protection. However, this protection often only provides a certain level of protection at the very beginning of the power supply and cannot protect the output rectifier diodes at the high-frequency transformer end of the flyback switching power supply under high surge conditions.

[0028] Therefore, the present invention proposes a protection device for a flyback switching power supply, specifically a breakdown protection circuit for the output rectifier diode of an electric vehicle flyback switching power supply. By adjusting the circuit structure of the flyback switching power supply, an absorption branch is connected in parallel to the front end of the output rectifier diode after the high-frequency transformer in the flyback switching power supply. A varistor RV and a relay K1 are installed on this absorption branch. A voltage detection module (such as a surge detection module or surge detection circuit module) is connected to the front end of the output rectifier diode after the high-frequency transformer in the flyback switching power supply. After the main chip MCU detects that the voltage converted by the voltage detection module is an abnormal surge voltage, it issues a command to drive the relay K1 to engage, connecting the varistor RV, which is normally disconnected, in parallel in the circuit. That is, the varistor RV is connected in parallel to the front end of the output rectifier diode, so as to relieve the abnormal surge voltage through the varistor RV. This enables early protection against breakdown of the output rectifier diode when a high DC surge voltage impacts, preventing the flyback switching power supply from failing and improving the reliability of the flyback switching power supply while reducing circuit power consumption.

[0029] According to an embodiment of the present invention, a protection device for a flyback switching power supply is provided. See also... Figure 1 The diagram shows a structural schematic of an embodiment of the device of the present invention. The flyback switching power supply includes: a transformer module and an output rectifier diode module, the transformer module being, for example, a high-frequency transformer T1, and the output rectifier diode module being, for example, an output rectifier diode D2; the protection device of the flyback switching power supply includes: an absorption branch, a voltage detection module, and a control module, the control module being, for example, a main chip MCU; the absorption branch includes: an absorption module and a switching module, the absorption module being, for example, a varistor RV, and the switching module being, for example, a relay K1.

[0030] The DC input voltage is input to the primary winding of the transformer module; the output side of the secondary winding of the transformer module outputs a DC voltage after passing through the output rectifier diode module; the absorption branch is located on the output side of the secondary winding of the transformer module, connected in parallel with the output rectifier diode module, and located in front of the output rectifier diode module; the switch module is in the off state by default.

[0031] The voltage detection module is located on the output side of the secondary winding of the transformer module and at the front end of the output rectifier diode module, and is used to detect the voltage on the output side of the secondary winding of the transformer module.

[0032] The control module is configured to, upon receiving the voltage at the output side of the secondary winding of the transformer module, determine that the voltage at the output side of the secondary winding of the transformer module is not within the set voltage range, and therefore consider that the DC bus voltage of the flyback switching power supply has fluctuated or surged, and issue a control signal to control the switching module to close.

[0033] The switching module is used to close itself upon receiving the control signal, thereby connecting the absorption branch and allowing the absorption module to absorb the fluctuating voltage or the surge voltage, thus protecting the output rectifier diode module.

[0034] This invention addresses the problem of breakdown of the output rectifier diodes on the high-frequency transformer side of a flyback switching power supply used in high-voltage DC applications for electric vehicles. The solution provides a breakdown protection circuit for the flyback switching power supply's output rectifier diodes. This is achieved by adjusting the circuit structure of the flyback switching power supply by connecting a parallel absorption branch to the front end of the output rectifier diodes on the high-frequency transformer side. This absorption branch includes a varistor RV and a relay K1. A voltage detection module (such as a surge detection module or surge detection circuit module) is connected to the front end of the output rectifier diodes on the high-frequency transformer side of the flyback switching power supply. The main chip MCU detects an abnormal surge voltage from the voltage detected by the voltage detection module and then triggers a drive to activate the relay K1. The following design allows for the following: When an abnormal surge voltage is detected, the normally disconnected varistor RV is connected in parallel to the circuit. Specifically, the varistor RV is connected in parallel to the front end of the output rectifier diode. This allows the varistor RV to release the abnormal surge voltage, preventing abnormally high surge voltage from causing the output rectifier diode behind the high-frequency transformer in the flyback switching power supply to break down. This provides early protection against high DC surge voltage, preventing the output rectifier diode from breaking down and avoiding flyback power supply failure. This improves the reliability of the flyback switching power supply, reduces circuit power consumption, and enhances the reliability and stability of the flyback switching power supply during operation. It also solves the problem of flyback switching power supply failure and controller damage caused by output rectifier diode breakdown, fundamentally reducing after-sales safety hazards and product quality issues.

[0035] In some embodiments, the absorption module includes: a varistor module, such as a varistor RV; the switching module includes: a relay module, such as a relay K1.

[0036] Specifically, on the output side of the secondary winding of the transformer module, the same-name terminal of the secondary winding of the transformer module is connected to the opposite-name terminal of the secondary winding of the transformer module via the varistor and the normally open contact of the relay module.

[0037] The same-name terminal of the secondary winding of the transformer module is also connected to the anode of the output rectifier diode module; the cathode of the output rectifier diode module is connected to the first connection terminal of the DC voltage output terminal of the flyback switching power supply; the opposite-name terminal of the secondary winding of the transformer module is also connected to the second connection terminal of the DC voltage output terminal of the flyback switching power supply; the second connection terminal of the DC voltage output terminal of the flyback switching power supply is grounded.

[0038] Figure 2 This is a schematic diagram of one embodiment of a flyback switching power supply output rectifier diode breakdown protection circuit. See also... Figure 2 In the example shown, the voltage detection module (such as a surge detection module, surge detection circuit module, etc.) is used to detect abnormal surge voltages; after the relay circuit detects the signal from the voltage detection module through the main chip MCU, it controls whether the varistor RV is connected to the circuit, thereby realizing the protection of the output rectifier diode by the varistor RV.

[0039] The solution of this invention is to adjust the circuit structure of the flyback switching power supply by connecting a voltage detection module (such as a surge detection module or surge detection circuit module) to the output rectifier diode. The main chip sends a drive relay energizing command after detecting the voltage converted by the voltage detection module. When an abnormal surge voltage is detected, the varistor, which is normally disconnected, is connected in parallel to the circuit. This achieves early protection against high DC surge voltage impacts, preventing the output rectifier diode from breaking down. This protection is mainly concentrated on the secondary side of the high-frequency transformer, i.e., protecting the output rectifier diode. Without early protection, different surge voltage inputs would occur, causing the rectifier diode voltage to rise rapidly. If the reverse voltage on the diode exceeds the rated voltage, the diode will overvoltage and short-circuit, resulting in failure. The early protection provides the following benefits: it can detect and absorb potential surge voltages that could damage the diode, protecting it from overvoltage breakdown if it is operating normally, thus ensuring the normal operation of the switching power supply, the main board, and the unit.

[0040] Figure 6 This is a schematic diagram of the experimental data table. Figure 7 The experimental data for the defective diode wafer is shown in the screenshot below; for the experimental data of the present invention, please refer to... Figure 6 and Figure 7 The example shown. See also Figure 6The datasheet shows that under a surge voltage input of 4kV and 1.5 / 50μs, the reverse voltage of the rectifier diode exceeded its rated voltage of 200V, indicating a potential for breakdown and short circuit. When the test voltage was increased to over 5kV during the experiment, the rectifier diode broke down and short-circuited. Upon re-examination of the defective products, a breakdown point was found on the edge of the rectifier diode wafer. For details, please refer to [link to relevant documentation]. Figure 7 The example shown. See also Figure 7 As shown in the example, the location of the internal wafer damage in the defective rectifier diode reproduced by the surge test is completely consistent with that of the defective product after the sale, confirming that the rectifier diode was indeed damaged due to excessive input voltage.

[0041] In some embodiments, the protection device for the flyback switching power supply described in the present invention further includes an output filtering module, such as capacitor C6. The output filtering module is disposed between the cathode of the output rectifier diode module and the second connection terminal of the DC voltage output terminal of the flyback switching power supply, and is used to rectify and filter the voltage on the output side of the secondary winding of the transformer module before outputting it.

[0042] In some embodiments, the protection device for the flyback switching power supply described in the present invention further includes: an input filtering module, such as an input filtering capacitor bank composed of capacitors C1, C2, C3, and C4. The input filtering module is located between the input terminal of the DC input voltage and the input side of the primary winding of the transformer module, and is disposed between the input terminal of the DC input voltage and ground, for filtering the DC input voltage before inputting it to the input side of the primary winding of the transformer module.

[0043] In some embodiments, where the protection device of the flyback switching power supply further includes an input filtering module, the protection device of the flyback switching power supply further includes: a sampling module, a voltage regulator module, an optocoupler module, a switching power supply chip, and a clamping protection module. The sampling module is such as a resistor R2, the voltage regulator module is such as a precision voltage regulator U3, the optocoupler module is such as an optocoupler chip U2 and a resistor R2, the switching power supply chip is such as a switching power supply chip U1 with an internally integrated high-voltage MOSFET, and the clamping protection module is such as a drain clamping protection circuit composed of a resistor R1, a capacitor C5, and a diode D1.

[0044] The sampling module is located at the output terminal of the flyback switching power supply and is used to sample the output DC voltage of the flyback switching power supply.

[0045] The voltage regulator module is disposed between the sampling module and the optocoupler module. It is used to divide the DC output voltage of the sampled flyback switching power supply and extract the divided voltage. It also sets the reference voltage of the optocoupler module based on the extracted divided voltage to determine the forward voltage drop of the diode in the optocoupler module.

[0046] The optocoupler module is located on the output side of the voltage regulator module and is connected to the switching power supply chip and the input side of the primary winding of the transformer module (specifically, it is connected to the same-name terminal of the primary winding of the transformer module), and is used to provide control current to the control terminal of the MOS transistor in the switching power supply chip.

[0047] The switching power supply chip, disposed between the optocoupler module and the clamping protection module, is used to reduce the duty cycle of the MOS transistor in the switching power supply chip when the sampled output DC voltage of the flyback switching power supply is greater than the sum of the forward voltage drop of the diode in the optocoupler module and the voltage drop across the sampling module. This is achieved by providing a control current at the control terminal of the MOS transistor in the switching power supply chip as the emitter current of the transistor in the optocoupler module increases, thereby reducing the output DC voltage of the flyback switching power supply and clamping protection for the output DC voltage of the flyback switching power supply.

[0048] In some embodiments, where the protection device of the flyback switching power supply further includes an output filtering module but not an input filtering module, the protection device of the flyback switching power supply further includes: a sampling module, a voltage regulator module, an optocoupler module, a switching power supply chip, and a clamping protection module. The sampling module is such as a resistor R2, the voltage regulator module is such as a precision voltage regulator U3, the optocoupler module is such as an optocoupler chip U2 and a resistor R2, the switching power supply chip is such as a switching power supply chip U1 with an internally integrated high-voltage MOSFET, and the clamping protection module is such as a drain clamping protection circuit composed of a resistor R1, a capacitor C5, and a diode D1.

[0049] The sampling module is located at the output terminal of the flyback switching power supply and is used to sample the output DC voltage of the flyback switching power supply.

[0050] The voltage regulator module is disposed between the sampling module and the optocoupler module. It is used to divide the DC output voltage of the sampled flyback switching power supply and extract the divided voltage. It also sets the reference voltage of the optocoupler module based on the extracted divided voltage to determine the forward voltage drop of the diode in the optocoupler module.

[0051] The optocoupler module is located on the output side of the voltage regulator module and is connected to the switching power supply chip and the input side of the primary winding of the transformer module (specifically, it is connected to the same-name terminal of the primary winding of the transformer module), and is used to provide control current to the control terminal of the MOS transistor in the switching power supply chip.

[0052] The switching power supply chip, disposed between the optocoupler module and the clamping protection module, is used to reduce the duty cycle of the MOS transistor in the switching power supply chip when the sampled output DC voltage of the flyback switching power supply is greater than the sum of the forward voltage drop of the diode in the optocoupler module and the voltage drop across the sampling module. This is achieved by providing a control current at the control terminal of the MOS transistor in the switching power supply chip as the emitter current of the transistor in the optocoupler module increases, thereby reducing the output DC voltage of the flyback switching power supply and clamping protection for the output DC voltage of the flyback switching power supply.

[0053] Specifically, such as Figure 2 The flyback switching power supply output rectifier diode breakdown protection circuit shown includes: a DC filter circuit, a drain clamping protection circuit, a high-frequency transformer, a bias circuit, an optocoupler feedback circuit, a built-in MOS switching power supply chip, a main chip MCU, a voltage detection module, an output rectifier filter circuit, an output sampling circuit, a transistor-controlled relay circuit, and a varistor RV. For details on the transistor-controlled relay circuit, please refer to [link to relevant documentation]. Figure 8 The example shown, Figure 8 The transistor-controlled relay circuit shown has one end connected to the front end of rectifier diode D2 and the other end grounded; Figure 8 In the example shown, transistor Q1 controls relay K1 under the control of the MCU.

[0054] The high-voltage DC input voltage Ui passes through a DC filter circuit, a drain clamping protection circuit, a high-frequency transformer, and an output rectifier and filter circuit to output a DC output voltage U0. The output sampling circuit samples the output voltage from the output rectifier and filter circuit, and then, after passing through an optocoupler feedback circuit and a built-in MOS switching power supply chip, outputs a control signal to the drain clamping protection circuit. A bias circuit is located between the high-frequency transformer and the optocoupler feedback circuit. The voltage detection module samples the secondary voltage of the high-frequency transformer from its output side, and then, after passing through the voltage detection module, the main chip MCU, a transistor-controlled relay circuit, and a varistor RV, feeds the signal back to the output rectifier and filter circuit.

[0055] Figure 3 This is a schematic diagram of another embodiment of a flyback switching power supply output rectifier diode breakdown protection circuit, specifically a schematic diagram of an embodiment of a flyback switching power supply output rectifier diode breakdown protection circuit for electric vehicles. Figure 3The flyback switching power supply output rectifier diode anti-breakdown circuit shown includes: capacitors C1, C2, C3, C4, C5, C6, C7, and C8; resistors R1, R2, R3, R4, and R5; a high-frequency transformer T1; diodes D1 and D2; a varistor RV; a relay K1; a switching power supply chip with an integrated high-voltage MOSFET; an optocoupler chip U2; and a precision voltage regulator U3.

[0056] The high-voltage DC input voltage Ui is 576V DC. Ui is grounded after passing through parallel capacitors C1, C2, C3, and C4. Ui is also connected to the cathode of diode D1 via resistor R1; the anode of diode D1 is connected to the output terminal of the switching power supply chip with an integrated high-voltage MOSFET. Ui is further connected to the anode of diode D1 via capacitor C5. Ui is also connected to the opposite-named terminal of the primary winding of high-frequency transformer T1. The same-named terminal of the primary winding of high-frequency transformer T1 is connected to the collector of the transistor side in optocoupler chip U2. The emitter of the transistor side in optocoupler chip U2 is connected to the input terminal of the switching power supply chip with an integrated high-voltage MOSFET. The switching power supply chip with an integrated high-voltage MOSFET includes both a MOSFET and a power supply IC.

[0057] The corresponding terminal of the secondary winding of high-frequency transformer T1 is grounded via varistor RV and the normally open contact of relay K1. The corresponding terminal of the secondary winding of high-frequency transformer T1 is also connected to the input terminal of the voltage detection module. The corresponding terminal of the secondary winding of high-frequency transformer T1 is also connected to the anode of diode D2; the cathode of diode D2 is grounded via capacitor C6; the cathode of diode D2 is also connected to the connection terminal of output voltage U0. The connection terminal of output voltage U0 can output a +24V DC voltage.

[0058] The output voltage U0 is connected to the anode of the diode in the optocoupler chip U2 via resistor R2. The output voltage U0 is also connected to ground via resistors R5 and R3. The common terminal of resistors R5 and R3 is connected to the first terminal of the precision voltage regulator U3. This common terminal is further connected to the second terminal of the precision voltage regulator U3 via capacitor C8 and resistor R4. The second terminal of the precision voltage regulator U3 is connected to the cathode of the diode in the optocoupler chip U2; it is also grounded via capacitor C7.

[0059] See Figure 2 and Figure 3The example shown includes a DC filter circuit for the high-voltage DC input voltage Ui, comprising an input filter capacitor bank consisting of capacitors C1, C2, C3, and C4. An integrated high-voltage MOSFET switching power supply chip U1 is included, which contains an oscillator, a reference voltage source, an error amplifier, and a PWM comparator. The drain clamping protection circuit consists of resistor R1, capacitor C5, and diode D1. The output rectifier filter circuit consists of diode D2 and capacitor C6; diode D2 is the output rectifier diode. The surge protection varistor RV is part of the surge protection module.

[0060] The optocoupler circuit includes an optocoupler chip U2 and a resistor R2, where resistor R2 is used to set the gain of the control loop. The bias circuit, also known as the bias regulator circuit, consists of a precision voltage regulator U3, capacitors C7 and C8, and resistor R4, providing bias voltage to the phototransistor in the optocoupler chip U2. The output voltage of the precision voltage regulator U3 is obtained by voltage division via resistors R3 and R5. The precision voltage regulator U3 can be a controllable precision voltage divider TL431. The single-channel output voltage U0 is DC +24V.

[0061] See Figure 2 and Figure 3 In the example shown, when the high-voltage DC voltage of 450V to 750V is filtered by the input filter capacitor, it is connected to one end of the primary winding of the high-frequency transformer T1 (i.e., the primary winding of the high-frequency transformer T1). The other end of the primary winding of the high-frequency transformer T1 (i.e., the primary winding of the high-frequency transformer T1) is connected to the drain D of the MOSFET in the switching power supply chip U1, which integrates a high-voltage MOSFET. The drain clamping protection circuit consists of a transient voltage suppression circuit, namely resistor R1, capacitor C5, and diode D1. It is used to absorb the voltage spike generated by the leakage inductance of the high-frequency transformer T1 when the MOSFET in the switching power supply chip U1 with integrated high-voltage MOSFET is turned off and limit it to a safe range. It protects the drain of the MOSFET in the switching power supply chip U1 with integrated high-voltage MOSFET. The output voltage of the secondary winding of the high-frequency transformer T1 is rectified by diode D2 (specifically, it can be a Schottky diode). After rectification, it is filtered by the filter capacitor C6, and the output DC voltage U0 is a +24V DC voltage.

[0062] When the output voltage U0 fluctuates, a voltage of +2.5V is divided by the voltage divider resistors R3 and R5. This voltage is compared with the +2.499V reference voltage inside the optocoupler chip U2. The duty cycle of the MOSFET in the switching power supply chip U1, which integrates a high-voltage MOSFET, is adjusted accordingly. Let the forward voltage drop of the diode (such as an LED) in the optocoupler chip U2 be Uf, and the voltage drop across resistor R2 be Ur2. Then, the output voltage U0 of the electric vehicle flyback switching power supply = the forward voltage drop of the LED Uf + the voltage drop across resistor R2 Ur2. When the output voltage U0 increases for some reason, i.e., when the output voltage U0 > the forward voltage drop Uf of the LED + the voltage drop Ur2 across the resistor R2, the resulting error voltage Urr = output voltage U0 - (the forward voltage drop Uf of the LED + the voltage drop Ur2 across the resistor R2). This causes the current on the LED in the optocoupler chip U2 to increase, and the current through the emitter of the transistor in the optocoupler chip U2, such as the phototransistor, to increase. This, in turn, increases the current at the control terminal of the switching power supply chip U1, which integrates a high-voltage MOSFET. The duty cycle of the MOSFET in the switching power supply chip U1 decreases, resulting in a decrease in the output voltage U0, thus achieving fine adjustment of the output voltage U0. The reverse is also true.

[0063] However, due to the harsh external operating environment of electric buses, when the high-voltage DC power input to the bus experiences voltage fluctuations or abnormal surge voltage impacts, the output U0 will be very large. Since there is generally no protection in front of the output rectifier diode in the circuit, the output voltage U0 exceeds the effective voltage withstand value of the output rectifier diode, causing the output rectifier diode, such as diode D2, to break down due to overvoltage. If the power supply is not cut off in time, the output rectifier diode, such as diode D2, will explode, resulting in the destruction of the flyback switching power supply. In addition, from the perspective of actual breakdown, it is an overvoltage breakdown. Therefore, by adjusting the circuit structure of the switching power supply, a voltage detection module (such as a surge detection module or surge detection circuit module) is connected to the front end of the output rectifier diode, such as diode D2. Under normal circumstances, the main chip MCU detects the low voltage Ua converted by the voltage detection module. When the main chip MCU recognizes that the voltage value (i.e., the low voltage Ua) is within the normal setting range, it does not issue a command to drive the relay K1. The relay K1 does not work and is disconnected. The varistor RV connected in parallel to the front end of the diode is not connected to the circuit, and the flyback switching power supply works normally with low power consumption. When the main chip MCU detects a high surge voltage through the voltage detection module, it detects the low voltage Ub converted by the voltage detection module. When it recognizes that the value of the low voltage Ub is not within the normal setting range, the main chip MCU issues a command to drive the relay K1 to engage. This connects the varistor RV, which is normally disconnected, in parallel to the circuit of the flyback switching power supply. This enables early protection against high DC surge voltage impacts, preventing the output rectifier diode, such as diode D2, from breaking down. This avoids the problem of flyback switching power supply failure and improves the reliability of the flyback switching power supply.

[0064] A high-surge-resistance varistor RV is connected in parallel with the output rectifier diode, such as diode D2. When an abnormal surge voltage is coupled to the secondary winding of the high-frequency transformer T1, the varistor RV absorbs it in time. When the flyback switching power supply circuit is in normal use, the impedance of the varistor RV is very high and the leakage current is very small, so it can be regarded as an open circuit and has almost no impact on the flyback switching power supply circuit. However, when a very high surge voltage arrives, the resistance value of the varistor RV drops instantaneously, such as from the MΩ (megaohm) level to the mΩ (milliohm) level, allowing a large current to flow through the varistor RV and clamping the overvoltage to a certain value, thereby protecting the output rectifier diode, such as diode D2, and enabling the flyback switching power supply to operate normally.

[0065] As can be seen, by adjusting the switching power supply circuit structure and connecting a voltage detection module (such as a surge detection module or surge detection circuit module) to the front end of the output rectifier diode, under normal circumstances, the main chip detects the low voltage Ua converted by the voltage detection module. When the main chip MCU recognizes that the voltage value (i.e., the low voltage Ua) is within the normal setting range, it does not issue a command to drive the relay K1. The relay K1 does not work and is disconnected. The varistor RV connected in parallel to the front end of the diode is not connected to the circuit of the flyback switching power supply, and the flyback switching power supply works normally with low power consumption. When the main chip MCU detects a high surge voltage through the voltage detection module, the main chip MCU detects the low voltage Ub converted by the voltage detection module. When it recognizes that the value of the low voltage Ub is not within the normal setting range, the main chip MCU issues a command to drive the relay K1 to engage. This connects the varistor RV, which is normally disconnected, in parallel to the circuit of the flyback switching power supply, thus enabling early protection against high DC surge voltage impacts and preventing the output rectifier diode, such as diode D2, from breaking down.

[0066] The solution of this invention, by adjusting the circuit structure of the flyback switching power supply and connecting a varistor in parallel with the output rectifier diode, allows for the discharge of high DC surge voltages through this varistor. This proactively protects the output rectifier diode from breakdown, preventing flyback switching power supply failure and improving its reliability. This fundamentally reduces after-sales safety hazards and product quality issues. Furthermore, in actual testing of a flyback switching power supply, an output rectifier diode breakdown was observed. By adjusting the electronic components to avoid safety hazards and power supply failure, this invention provides a new approach for controller product development and design, compensating for the deficiencies and defects of flyback switching power supply protection circuits.

[0067] The technical solution of this invention involves setting an absorption branch and a voltage detection module on the output side of the secondary winding of the high-frequency transformer in a flyback switching power supply, at the front end of the output rectifier diode. This absorption branch is connected in parallel with the output rectifier diode. The absorption branch includes an absorption module (such as a varistor RV) and a switching module (such as a relay K1), with the switching module defaulting to an open state. When the flyback switching power supply is operating, the voltage detection module detects the voltage on the output side of the secondary winding of the high-frequency transformer, and the main chip MCU determines whether the voltage is within a set voltage range. If not, the voltage is considered to be within the set range. The voltage detected by the detection module is a surge voltage. The main chip MCU controls the closing of the switch module so that the absorption module can absorb the fluctuating voltage or surge voltage, thereby protecting the output rectifier diode. Thus, by setting an absorption branch and a voltage detection module on the output side of the secondary winding of the high-frequency transformer in the flyback switching power supply, when a fluctuating voltage or surge voltage is detected on the output side of the secondary winding of the high-frequency transformer in the flyback switching power supply, the absorption branch is used to absorb the fluctuating voltage or surge voltage, thereby protecting the output rectifier diode from breakdown in advance and improving the timeliness and reliability of the protection for the flyback switching power supply.

[0068] According to an embodiment of the present invention, an electric vehicle corresponding to a protection device for a flyback switching power supply is also provided. The electric vehicle may include the protection device for the flyback switching power supply described above.

[0069] Since the processing and functions implemented by the electric vehicle in this embodiment are basically corresponding to the embodiments, principles and examples of the device, any details not covered in the description of this embodiment can be found in the relevant descriptions in the foregoing embodiments, and will not be repeated here.

[0070] The technical solution of this invention involves setting an absorption branch and a voltage detection module on the output side of the secondary winding of the high-frequency transformer in a flyback switching power supply, at the front end of the output rectifier diode. This absorption branch is connected in parallel with the output rectifier diode. The absorption branch includes an absorption module (such as a varistor RV) and a switching module (such as a relay K1), with the switching module defaulting to an open state. When the flyback switching power supply is operating, the voltage detection module detects the voltage on the output side of the secondary winding of the high-frequency transformer. The main chip MCU determines whether this voltage is within a set voltage range. If not, the voltage detected by the voltage detection module is considered a surge voltage, and the main chip MCU controls the switching module to close, allowing the absorption module to absorb the fluctuating or surge voltage, thus protecting the output rectifier diode. This proactive protection prevents the output rectifier diode from breaking down, avoiding flyback switching power supply failure and improving the reliability of the flyback switching power supply.

[0071] According to embodiments of the present invention, a protection method for a flyback switching power supply for an electric vehicle, corresponding to an electric vehicle, is also provided, such as... Figure 4 The diagram shows a flowchart of an embodiment of the method of the present invention. The protection method for the flyback switching power supply of this electric vehicle may include steps S110 to S130.

[0072] Step S110: Detect the voltage on the output side of the secondary winding of the transformer module.

[0073] Step S120: Upon receiving the voltage at the output side of the secondary winding of the transformer module, if it is determined that the voltage at the output side of the secondary winding of the transformer module is not within the set voltage range, it is considered that the DC bus voltage of the flyback switching power supply has fluctuated or surged, and a control signal is issued to control the switching module to close.

[0074] In step S130, upon receiving the control signal, the switch module closes itself to connect the absorption branch, allowing the absorption module to absorb the fluctuating voltage or the surge voltage, thereby protecting the output rectifier diode module.

[0075] This invention addresses the problem of breakdown of the output rectifier diodes on the high-frequency transformer side of a flyback switching power supply used in high-voltage DC applications for electric vehicles. The solution provides a breakdown protection circuit for the flyback switching power supply's output rectifier diodes. This is achieved by adjusting the circuit structure of the flyback switching power supply by connecting a parallel absorption branch to the front end of the output rectifier diodes on the high-frequency transformer side. This absorption branch includes a varistor RV and a relay K1. A voltage detection module (such as a surge detection module or surge detection circuit module) is connected to the front end of the output rectifier diodes on the high-frequency transformer side of the flyback switching power supply. The main chip MCU detects an abnormal surge voltage from the voltage detected by the voltage detection module and then triggers a drive to activate the relay K1. The following design allows for the following: When an abnormal surge voltage is detected, the normally disconnected varistor RV is connected in parallel to the circuit. Specifically, the varistor RV is connected in parallel to the front end of the output rectifier diode. This allows the varistor RV to release the abnormal surge voltage, preventing abnormally high surge voltage from causing the output rectifier diode behind the high-frequency transformer in the flyback switching power supply to break down. This provides early protection against high DC surge voltage, preventing the output rectifier diode from breaking down and avoiding flyback power supply failure. This improves the reliability of the flyback switching power supply, reduces circuit power consumption, and enhances the reliability and stability of the flyback switching power supply during operation. It also solves the problem of flyback switching power supply failure and controller damage caused by output rectifier diode breakdown, fundamentally reducing after-sales safety hazards and product quality issues.

[0076] In some embodiments, the protection method for the flyback switching power supply of an electric vehicle according to the present invention further includes: a process of clamping the output DC voltage of the flyback switching power supply.

[0077] The following is combined Figure 5 The diagram shows a flowchart of an embodiment of the method of the present invention for clamping protection of the output DC voltage of the flyback switching power supply. The specific process of clamping protection of the output DC voltage of the flyback switching power supply is further explained, including steps S210 to S240.

[0078] Step S210: Sample the output DC voltage of the flyback switching power supply.

[0079] Step S210: Divide the DC output voltage of the sampled flyback switching power supply and extract the divided voltage; and set the reference voltage of the optocoupler module based on the extracted divided voltage to determine the forward voltage drop of the diode in the optocoupler module.

[0080] Step S230: Through the optocoupler module, control current is provided to the control terminal of the MOS transistor in the switching power supply chip.

[0081] Step S240: When the sampled output DC voltage of the flyback switching power supply is greater than the sum of the forward voltage drop of the diode in the optocoupler module and the voltage drop across the sampling module, the control terminal of the MOS transistor in the switching power supply chip provides a control current that increases with the current at the emitter of the transistor in the optocoupler module. This causes the duty cycle of the MOS transistor in the switching power supply chip to decrease, thereby reducing the output DC voltage of the flyback switching power supply and achieving clamping protection for the output DC voltage of the flyback switching power supply.

[0082] Specifically, see Figure 2 and Figure 3 In the example shown, when the high-voltage DC voltage of 450V to 750V is filtered by the input filter capacitor, it is connected to one end of the primary winding of the high-frequency transformer T1 (i.e., the primary winding of the high-frequency transformer T1). The other end of the primary winding of the high-frequency transformer T1 (i.e., the primary winding of the high-frequency transformer T1) is connected to the drain D of the MOSFET in the switching power supply chip U1, which integrates a high-voltage MOSFET. The drain clamping protection circuit consists of a transient voltage suppression circuit, namely resistor R1, capacitor C5, and diode D1. It is used to absorb the voltage spike generated by the leakage inductance of the high-frequency transformer T1 when the MOSFET in the switching power supply chip U1 with integrated high-voltage MOSFET is turned off and limit it to a safe range. It protects the drain of the MOSFET in the switching power supply chip U1 with integrated high-voltage MOSFET. The output voltage of the secondary winding of the high-frequency transformer T1 is rectified by diode D2 (specifically, it can be a Schottky diode). After rectification, it is filtered by the filter capacitor C6, and the output DC voltage U0 is a +24V DC voltage.

[0083] When the output voltage U0 fluctuates, a voltage of +2.5V is divided by the voltage divider resistors R3 and R5. This voltage is compared with the +2.499V reference voltage inside the optocoupler chip U2. The duty cycle of the MOSFET in the switching power supply chip U1, which integrates a high-voltage MOSFET, is adjusted accordingly. Let the forward voltage drop of the diode (such as an LED) in the optocoupler chip U2 be Uf, and the voltage drop across resistor R2 be Ur2. Then, the output voltage U0 of the electric vehicle flyback switching power supply = the forward voltage drop of the LED Uf + the voltage drop across resistor R2 Ur2. When the output voltage U0 increases for some reason, i.e., when the output voltage U0 > the forward voltage drop Uf of the LED + the voltage drop Ur2 across the resistor R2, the resulting error voltage Urr = output voltage U0 - (the forward voltage drop Uf of the LED + the voltage drop Ur2 across the resistor R2). This causes the current on the LED in the optocoupler chip U2 to increase, and the current through the emitter of the transistor in the optocoupler chip U2, such as the phototransistor, to increase. This, in turn, increases the current at the control terminal of the switching power supply chip U1, which integrates a high-voltage MOSFET. The duty cycle of the MOSFET in the switching power supply chip U1 decreases, resulting in a decrease in the output voltage U0, thus achieving fine adjustment of the output voltage U0. The reverse is also true.

[0084] However, due to the harsh external operating environment of electric buses, when the high-voltage DC power input to the bus experiences voltage fluctuations or abnormal surge voltage impacts, the output U0 will be very large. Since there is generally no protection in front of the output rectifier diode in the circuit, the output voltage U0 exceeds the effective voltage withstand value of the output rectifier diode, causing the output rectifier diode, such as diode D2, to break down due to overvoltage. If the power supply is not cut off in time, the output rectifier diode, such as diode D2, will explode, resulting in the destruction of the flyback switching power supply. In addition, from the perspective of actual breakdown, it is an overvoltage breakdown. Therefore, by adjusting the circuit structure of the switching power supply, a voltage detection module (such as a surge detection module or surge detection circuit module) is connected to the front end of the output rectifier diode, such as diode D2. Under normal circumstances, the main chip MCU detects the low voltage Ua converted by the voltage detection module. When the main chip MCU recognizes that the voltage value (i.e., the low voltage Ua) is within the normal setting range, it does not issue a command to drive the relay K1. The relay K1 does not work and is disconnected. The varistor RV connected in parallel to the front end of the diode is not connected to the circuit, and the flyback switching power supply works normally with low power consumption. When the main chip MCU detects a high surge voltage through the voltage detection module, it detects the low voltage Ub converted by the voltage detection module. When it recognizes that the value of the low voltage Ub is not within the normal setting range, the main chip MCU issues a command to drive the relay K1 to engage. This connects the varistor RV, which is normally disconnected, in parallel to the circuit of the flyback switching power supply. This enables early protection against high DC surge voltage impacts, preventing the output rectifier diode, such as diode D2, from breaking down. This avoids the problem of flyback switching power supply failure and improves the reliability of the flyback switching power supply.

[0085] A high-surge-resistance varistor RV is connected in parallel with the output rectifier diode, such as diode D2. When an abnormal surge voltage is coupled to the secondary winding of the high-frequency transformer T1, the varistor RV absorbs it in time. When the flyback switching power supply circuit is in normal use, the impedance of the varistor RV is very high and the leakage current is very small, so it can be regarded as an open circuit and has almost no impact on the flyback switching power supply circuit. However, when a very high surge voltage arrives, the resistance value of the varistor RV drops instantaneously, such as from the MΩ (megaohm) level to the mΩ (milliohm) level, allowing a large current to flow through the varistor RV and clamping the overvoltage to a certain value, thereby protecting the output rectifier diode, such as diode D2, and enabling the flyback switching power supply to operate normally.

[0086] As can be seen, by adjusting the switching power supply circuit structure and connecting a voltage detection module (such as a surge detection module or surge detection circuit module) to the front end of the output rectifier diode, under normal circumstances, the main chip detects the low voltage Ua converted by the voltage detection module. When the main chip MCU recognizes that the voltage value (i.e., the low voltage Ua) is within the normal setting range, it does not issue a command to drive the relay K1. The relay K1 does not work and is disconnected. The varistor RV connected in parallel to the front end of the diode is not connected to the circuit of the flyback switching power supply, and the flyback switching power supply works normally with low power consumption. When the main chip MCU detects a high surge voltage through the voltage detection module, the main chip MCU detects the low voltage Ub converted by the voltage detection module. When it recognizes that the value of the low voltage Ub is not within the normal setting range, the main chip MCU issues a command to drive the relay K1 to engage. This connects the varistor RV, which is normally disconnected, in parallel to the circuit of the flyback switching power supply, thus enabling early protection against high DC surge voltage impacts and preventing the output rectifier diode, such as diode D2, from breaking down.

[0087] The solution of this invention, by adjusting the circuit structure of the flyback switching power supply and connecting a varistor in parallel with the output rectifier diode, allows for the discharge of high DC surge voltages through this varistor. This proactively protects the output rectifier diode from breakdown, preventing flyback switching power supply failure and improving its reliability. This fundamentally reduces after-sales safety hazards and product quality issues. Furthermore, in actual testing of a flyback switching power supply, an output rectifier diode breakdown was observed. By adjusting the electronic components to avoid safety hazards and power supply failure, this invention provides a new approach for controller product development and design, compensating for the deficiencies and defects of flyback switching power supply protection circuits.

[0088] Since the processing and functions implemented by the method in this embodiment are basically the same as those of the aforementioned electric vehicle embodiments, principles and examples, any details not covered in this embodiment can be found in the relevant descriptions in the aforementioned embodiments, and will not be repeated here.

[0089] In this embodiment, an absorption branch and a voltage detection module are set on the output side of the secondary winding of the high-frequency transformer in the flyback switching power supply, at the front end of the output rectifier diode. This absorption branch is connected in parallel with the output rectifier diode. The absorption branch includes an absorption module (such as a varistor RV) and a switching module (such as a relay K1), with the switching module in the off state by default. When the flyback switching power supply is operating, the voltage detection module detects the voltage on the output side of the secondary winding of the high-frequency transformer. The main chip MCU determines whether this voltage is within a set voltage range. If not, the voltage detected by the voltage detection module is considered a surge voltage, and the main chip MCU controls... The switch module is closed to allow the absorption module to absorb fluctuating or surge voltages, thus protecting the output rectifier diodes. By connecting a varistor RV in parallel with the output rectifier diodes, abnormal surge voltages are discharged through the varistor RV, preventing abnormally high surge voltages from causing the output rectifier diodes behind the high-frequency transformer in the flyback switching power supply to break down. This provides early protection against high DC surge voltages, preventing the output rectifier diodes from breaking down and avoiding flyback power supply failure. This improves the reliability of the flyback switching power supply, reduces circuit power consumption, and enhances the reliability and stability of the flyback switching power supply during operation.

[0090] In summary, it is readily understood by those skilled in the art that, without conflict, the aforementioned advantageous methods can be freely combined and superimposed.

[0091] The above description is merely an embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A protection device for a flyback switching power supply, characterized in that, The flyback switching power supply includes: a transformer module and an output rectifier diode module; the protection device of the flyback switching power supply includes: an absorption branch, a voltage detection module, and a control module; the absorption branch includes: an absorption module and a switching module; the absorption module includes: a varistor module; the switching module includes: a relay module; on the output side of the secondary winding of the transformer module, the same-name terminal of the secondary winding of the transformer module is connected to the opposite-name terminal of the secondary winding of the transformer module via the normally open contact of the varistor and the relay module; The same-name terminal of the secondary winding of the transformer module is also connected to the anode of the output rectifier diode module; the cathode of the output rectifier diode module is connected to the first connection terminal of the DC voltage output terminal of the flyback switching power supply; the opposite-name terminal of the secondary winding of the transformer module is also connected to the second connection terminal of the DC voltage output terminal of the flyback switching power supply; the second connection terminal of the DC voltage output terminal of the flyback switching power supply is grounded; wherein, A DC input voltage is input to the primary winding of the transformer module; the output side of the secondary winding of the transformer module outputs a DC voltage after passing through the output rectifier diode module; the absorption branch is located on the output side of the secondary winding of the transformer module, connected in parallel with the output rectifier diode module, and located in front of the output rectifier diode module; the switch module is in the off state by default. The voltage detection module is disposed on the output side of the secondary winding of the transformer module and located at the front end of the output rectifier diode module, and is used to detect the voltage on the output side of the secondary winding of the transformer module. The control module is configured to, upon receiving the voltage at the output side of the secondary winding of the transformer module, determine that the voltage at the output side of the secondary winding of the transformer module is not within the set voltage range, and then consider that the DC bus voltage of the flyback switching power supply has fluctuated or surged, and issue a control signal to control the switching module to close. The switching module is used to close itself upon receiving the control signal, thereby connecting the absorption branch and allowing the absorption module to absorb the fluctuating voltage or the surge voltage, thus protecting the output rectifier diode module.

2. The protection device for the flyback switching power supply according to claim 1, characterized in that, Also includes: Output filtering module; where, The output filtering module is located between the cathode of the output rectifier diode module and the second connection terminal of the DC voltage output terminal of the flyback switching power supply. It is used to rectify and filter the voltage on the output side of the secondary winding of the transformer module before outputting it.

3. The protection device for the flyback switching power supply according to claim 1 or 2, characterized in that, Also includes: Input filtering module; where, The input filtering module is located between the input terminal of the DC input voltage and the input side of the primary winding of the transformer module, and is disposed between the input terminal of the DC input voltage and ground. It is used to filter the DC input voltage before inputting it to the input side of the primary winding of the transformer module.

4. The protection device for the flyback switching power supply according to claim 3, characterized in that, Also includes: The system includes a sampling module, a voltage regulator module, an optocoupler module, a switching power supply chip, and a clamping protection module; among which, The sampling module is located at the output terminal of the flyback switching power supply and is used to sample the output DC voltage of the flyback switching power supply. The voltage regulator module is disposed between the sampling module and the optocoupler module. It is used to divide the DC output voltage of the sampled flyback switching power supply and extract the divided voltage. It also sets the reference voltage of the optocoupler module based on the extracted divided voltage to determine the forward voltage drop of the diode in the optocoupler module. The optocoupler module is located on the output side of the voltage regulator module and is connected to the input side of the primary winding of the switching power supply chip and the transformer module, respectively, and is used to provide control current to the control terminal of the MOS transistor in the switching power supply chip. The switching power supply chip, disposed between the optocoupler module and the clamping protection module, is used to reduce the duty cycle of the MOS transistor in the switching power supply chip when the sampled output DC voltage of the flyback switching power supply is greater than the sum of the forward voltage drop of the diode in the optocoupler module and the voltage drop across the sampling module. This is achieved by providing a control current at the control terminal of the MOS transistor in the switching power supply chip as the emitter current of the transistor in the optocoupler module increases, thereby reducing the output DC voltage of the flyback switching power supply and clamping protection for the output DC voltage of the flyback switching power supply.

5. The protection device for the flyback switching power supply according to claim 1 or 2, characterized in that, Also includes: The system includes a sampling module, a voltage regulator module, an optocoupler module, a switching power supply chip, and a clamping protection module; among which, The sampling module is located at the output terminal of the flyback switching power supply and is used to sample the output DC voltage of the flyback switching power supply. The voltage regulator module is disposed between the sampling module and the optocoupler module. It is used to divide the DC output voltage of the sampled flyback switching power supply and extract the divided voltage. It also sets the reference voltage of the optocoupler module based on the extracted divided voltage to determine the forward voltage drop of the diode in the optocoupler module. The optocoupler module is located on the output side of the voltage regulator module and is connected to the input side of the primary winding of the switching power supply chip and the transformer module, respectively, and is used to provide control current to the control terminal of the MOS transistor in the switching power supply chip. The switching power supply chip, disposed between the optocoupler module and the clamping protection module, is used to reduce the duty cycle of the MOS transistor in the switching power supply chip when the sampled output DC voltage of the flyback switching power supply is greater than the sum of the forward voltage drop of the diode in the optocoupler module and the voltage drop across the sampling module. This is achieved by providing a control current at the control terminal of the MOS transistor in the switching power supply chip as the emitter current of the transistor in the optocoupler module increases, thereby reducing the output DC voltage of the flyback switching power supply and clamping protection for the output DC voltage of the flyback switching power supply.

6. An electric vehicle, characterized in that, include: The protection device for the flyback switching power supply as described in any one of claims 1 to 5.

7. A protection method for a flyback switching power supply of an electric vehicle as described in claim 6, characterized in that, include: Detect the voltage on the output side of the secondary winding of the transformer module; If the voltage at the output side of the secondary winding of the transformer module is received, and it is determined that the voltage at the output side of the secondary winding of the transformer module is not within the set voltage range, then it is considered that the DC bus voltage of the flyback switching power supply has fluctuated or surged, and a control signal is issued to control the closing of the switching module. Upon receiving the control signal, the switch module closes itself to connect the absorption branch, allowing the absorption module to absorb the fluctuating voltage or surge voltage, thereby protecting the output rectifier diode module.

8. The protection method for the flyback switching power supply of an electric vehicle according to claim 7, characterized in that, Also includes: Sample the output DC voltage of the flyback switching power supply; The sampled output DC voltage of the flyback switching power supply is divided to extract the divided voltage; and the reference voltage of the optocoupler module is set based on the extracted divided voltage to determine the forward voltage drop of the diode in the optocoupler module. The optocoupler module provides control current to the control terminal of the MOSFET in the switching power supply chip. When the output DC voltage of the flyback switching power supply is greater than the sum of the forward voltage drop of the diode in the optocoupler module and the voltage drop across the sampling module, the control terminal of the MOSFET in the switching power supply chip provides a control current. As the current at the emitter of the transistor in the optocoupler module increases, the duty cycle of the MOSFET in the switching power supply chip decreases, thereby reducing the output DC voltage of the flyback switching power supply and achieving clamping protection for the output DC voltage of the flyback switching power supply.

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