Overvoltage protection circuit and overvoltage protection method

Abstract

Provided are an overvoltage protection circuit and an overvoltage protection method. The overvoltage protection circuit comprises: a pi filter circuit composed of an inductor and a capacitor, configured to filter an input voltage signal to obtain a filtered voltage signal; and an overvoltage protection unit, configured to generate an output voltage signal of the overvoltage protection circuit based on the filtered voltage signal, and output an adjusted voltage signal different from the filtered voltage signal as the output voltage signal of the overvoltage protection circuit in a case where a voltage value of the output voltage signal is greater than or equal to a first threshold value, the voltage value of the adjusted voltage signal being less than the first threshold value, wherein the adjusted voltage signal is in a sawtooth waveform.

Description

Technical Field

[0001] This disclosure relates to the field of circuits, and more specifically, to overvoltage protection circuits and overvoltage protection methods. Background Technology

[0002] Electrical equipment has strict safe operating voltage ranges. When the voltage in a circuit, such as the input voltage, exceeds these ranges, it can damage or burn out components, affecting the normal operation of the equipment and, in severe cases, even causing accidents. Therefore, overvoltage protection circuits are generally provided to protect the circuit and ensure electrical safety.

[0003] Meanwhile, with the rapid development of automotive electronic control, the Transmission Control Unit (TCU) has become one of the core control systems for vehicles with automatic transmissions. During vehicle operation, the TCU processes various sensor signals describing the current vehicle's driving state, determines the driver's intention to control the current gear, and controls the transmission to shift gears between different gears.

[0004] A typical TCU (Transmission Control Unit) includes control circuits, detection circuits, and drive circuits. Each circuit requires a power supply to function properly. Passenger cars typically use a 12V power supply system, while trucks and buses use a 24V system. Therefore, the TCU generally uses either 12V or 24V to power its internal circuits, or its internal power module performs DC-DC conversion to obtain the required voltages (e.g., 3.3V, 5V, etc.) for each circuit. However, during a vehicle load dump, large speed changes in the motor and braking can cause peak voltages of up to approximately 50V at the TCU's power input. This peak voltage can damage the TCU's internal circuits and power module, thus affecting its performance. Summary of the Invention

[0005] An embodiment of this disclosure provides an overvoltage protection circuit, comprising: a π-filter circuit composed of an inductor and a capacitor, used to filter an input voltage signal to obtain a filtered voltage signal; and an overvoltage protection unit, used to generate an output voltage signal of the overvoltage protection circuit based on the filtered voltage signal, and, when the voltage value of the output voltage signal is greater than or equal to a first threshold, output an adjustment voltage signal different from the filtered voltage signal as the output voltage signal of the overvoltage protection circuit, wherein the voltage value of the adjustment voltage signal is less than the first threshold, and wherein the adjustment voltage signal has a sawtooth waveform.

[0006] Embodiments of this disclosure also provide an overvoltage protection method for the overvoltage protection circuit described above, comprising: a π-filter circuit composed of an inductor and a capacitor filtering an input voltage signal to obtain a filtered voltage signal; an overvoltage protection unit generating an output voltage signal of the overvoltage protection circuit based on the filtered voltage signal, and, when the voltage value of the output voltage signal is greater than or equal to a first threshold, outputting an adjustment voltage signal different from the filtered voltage signal as the output voltage signal of the overvoltage protection circuit, wherein the voltage value of the adjustment voltage signal is less than the first threshold, and wherein the adjustment voltage signal exhibits a sawtooth waveform.

[0007] It should be understood that both the foregoing general description and the following detailed description are exemplary and intended to provide further illustration of the claimed technology. Attached Figure Description

[0008] The above and other objects, features, and advantages of this disclosure will become more apparent from the more detailed description of the embodiments thereof in conjunction with the accompanying drawings. The drawings are provided to further illustrate the embodiments of this disclosure and form part of the specification. They are used together with the embodiments of this disclosure to explain the disclosure and do not constitute a limitation thereof. In the drawings, the same reference numerals generally represent the same components or steps.

[0009] Figure 1A A circuit diagram of a TCU including an overvoltage protection circuit is shown.

[0010] Figure 1B-1C Two example circuit diagrams of overvoltage protection circuits are shown.

[0011] Figure 2A A circuit diagram of a TCU including an overvoltage protection circuit according to an embodiment of the present disclosure is shown.

[0012] Figure 2B An example circuit diagram of an overvoltage protection circuit according to an embodiment of the present disclosure is shown.

[0013] Figure 3 A waveform diagram of each voltage signal is shown when the overvoltage protection circuit according to an embodiment of the present disclosure is in operation.

[0014] Figure 4 A flowchart of an overvoltage protection method according to an embodiment of the present disclosure is shown. Detailed Implementation

[0015] The technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0016] For the high peak voltage at the power input terminal of the TCU mentioned above, a common solution is to add an overvoltage protection unit before the power input terminal of each internal circuit (when the TCU does not have an internal power module) or before the input terminal of the internal power module (when the TCU has an internal power module) to keep the corresponding input voltage within a safe range.

[0017] In addition, in order for the TCU (especially the TCU including the internal power module) to pass the electromagnetic compatibility test, it is usually necessary to set up a π-type filter circuit composed of inductors and capacitors in each part of the internal circuit or the internal power module.

[0018] For ease of description and better understanding of this disclosure, this document describes in detail an overvoltage protection circuit within a TCU. However, those skilled in the art will understand that the application of the overvoltage protection circuit should not be limited to the TCU, and other applications are also possible, such as for general electrical equipment.

[0019] Furthermore, this article uses the case where the TCU includes an internal power supply module as an example for illustration. However, those skilled in the art will understand that the case where the TCU does not have an internal power supply module (i.e., the voltage at the power input terminal of the TCU directly supplies power to the control circuit, detection circuit, etc. inside the TCU) is similar, except that the internal voltage conversion step is missing. This disclosure does not impose any limitations on this.

[0020] Figure 1A A circuit diagram of a TCU including an overvoltage protection circuit is shown. Figure 1B-1C It shows Figure 1A The diagram shows two example circuit diagrams of the overvoltage protection circuit in the TCU.

[0021] like Figure 1AAs shown above, in order to ensure that the input voltage of each circuit in the TCU (e.g., control circuit, detection circuit, and drive circuit) or the input voltage of the internal power supply module of the TCU is kept within a safe range and meets the requirements of electromagnetic compatibility, an overvoltage protection circuit 100 is provided in front of each circuit in the TCU or the internal power supply module of the TCU. The overvoltage protection circuit 100 includes an overvoltage protection unit 101 and a π filter circuit 102 composed of an inductor and a capacitor (hereinafter referred to as the LC-π filter circuit).

[0022] It is worth noting that, although Figure 1A The diagram shows that the overvoltage protection circuit 100 is located inside the TCU, but depending on the specific circumstances, the overvoltage protection circuit 100 may also be located outside the TCU.

[0023] Generally, the overvoltage protection unit 101 can use a Zener diode for overvoltage protection, such as... Figure 1B As shown, by selecting a Zener diode of appropriate specifications, the high voltage appearing at the power input terminal of the TCU can be stabilized to its regulated value and supplied to the input terminal of the TCU's internal power module. However, Zener diodes have low efficiency and generate a lot of heat.

[0024] Therefore, an overvoltage protection unit 101 based on an overvoltage protection control integrated circuit (IC) is also proposed. For example... Figure 1C As shown, the overvoltage protection unit 101 includes a switching transistor Q and an overvoltage protection control module 1011 (the control module includes a control integrated circuit IC). When the voltage value of the input voltage signal at the power input terminal of the TCU is within the normal range, the overvoltage protection control integrated circuit IC controls the switching transistor Q to remain on. The overvoltage protection circuit directly outputs the input voltage signal at the power input terminal to the LC-π filter circuit, and then provides it to the internal power module of the TCU. When an overvoltage is detected at the power input terminal of the TCU, the overvoltage protection control integrated circuit IC controls the switching transistor Q to be intermittently turned on and off, similar to a voltage regulator, so that the voltage value of the voltage signal provided to the internal power module of the TCU by the LC-π filter circuit is within the normal range.

[0025] However, when the overvoltage protection control integrated circuit IC controls the switching transistor Q to switch between on and off states, i.e., when the switching transistor Q is intermittently turned on and off, since the first terminal of the switching transistor Q is connected to the input terminal of the overvoltage protection unit and the second terminal is connected to the output terminal of the overvoltage protection unit, i.e., the input terminal of the LC-π filter circuit, when the switching transistor Q is off, the value of the input current signal of the LC-π filter circuit will be zero until the switch is turned on again. That is, the input current signal of the LC-π filter circuit will be discontinuous. This will cause the inductor and capacitor in the LC-π filter circuit 102, as shown in the figure, to form an LC oscillation loop, thereby generating an oscillating voltage signal at the output terminal of the overvoltage protection circuit 100. If the peak value of the oscillation voltage signal is higher than the maximum input voltage allowed by the internal power module of the TCU, the internal power module connected to the output terminal may be damaged, and the TCU will not work properly. Therefore, as Figure 1C The use of overvoltage protection units with the circuit structure shown is limited.

[0026] Therefore, this disclosure proposes an improved overvoltage protection circuit that ensures that the electrical equipment (e.g., the internal power module of the TCU) can still operate normally even if the voltage value of the input voltage signal from the power supply (e.g., battery) to the power input terminal of the electrical device (e.g., TCU) is abnormally high (e.g., overvoltage at the power input terminal of the TCU during load dumping).

[0027] Figure 2A A circuit diagram of a TCU including an overvoltage protection circuit according to an embodiment of the present disclosure is shown. Figure 2B An example circuit diagram of an overvoltage protection circuit according to an embodiment of the present disclosure is shown.

[0028] like Figure 2A As shown, the LC-π filter circuit 202 is positioned before the overvoltage protection unit 201. The LC-π filter circuit 202 is used to filter the input voltage signal to obtain a filtered voltage signal. The input terminal of the overvoltage protection unit 201 is connected to the output terminal of the LC-π filter circuit 201, and is used to output the filtered voltage signal as the output voltage signal of the overvoltage protection circuit, or to adjust the filtered voltage signal to obtain an adjusted voltage signal as the output voltage signal of the overvoltage protection circuit, and then provide the output voltage signal to the internal power module of the TCU.

[0029] Furthermore, when the overvoltage protection unit 201 adjusts the filtered voltage signal, the current flowing into the overvoltage protection unit 201 from the LC-π filter circuit 202 is discontinuous, which causes the adjusted voltage signal to have a sawtooth waveform. The specific process will be described in detail later.

[0030] More specifically, Figure 2BA further circuit diagram of an overvoltage protection circuit 200 according to an embodiment of the present disclosure is shown.

[0031] like Figure 2B As shown, the LC-π filter circuit 202 includes an inductor and two capacitors connected in a π-type configuration. The LC-π filter circuit 202 receives the input voltage signal Vin from the power supply and can filter the input voltage signal Vin to obtain the filtered voltage signal Vin_filtered.

[0032] The input terminal of the overvoltage protection unit 201 receives the filtered voltage signal Vin_filtered and generates the output voltage signal Vout of the overvoltage protection circuit based on the filtered voltage signal Vin_filtered.

[0033] Furthermore, when the voltage value of the output voltage signal Vout is detected to remain below the first threshold, the overvoltage protection unit 201 directly uses the filtered voltage signal Vin_filtered as the output voltage signal Vout of the overvoltage protection circuit 300. And when the voltage value of the output voltage signal Vout is detected to be greater than or equal to the first threshold, the overvoltage protection unit 201 outputs an adjustment voltage signal Vp_out, which is different from the filtered voltage signal, as the output voltage signal Vout of the overvoltage protection circuit. The voltage value of the adjustment voltage signal Vp_out is less than the first threshold and has a sawtooth waveform.

[0034] Optionally, keeping the voltage value of the output voltage signal Vout below the first threshold can mean that the voltage value of the output voltage signal Vout is below the first threshold for a preset time period.

[0035] Optionally, the first threshold can be set according to the maximum input voltage allowed by the internal power module in the TCU unit.

[0036] The structure of the overvoltage protection unit 201 is described in detail below.

[0037] The overvoltage protection unit includes a switching transistor Q and an output capacitor Cout. The first terminal of the switching transistor Q is connected to the input terminal of the overvoltage protection unit 201 to receive the filtered voltage signal Vin_filtered. The second terminal of the switching transistor Q is connected to the output terminal of the overvoltage protection unit 201 to output the filtered voltage signal Vin_filtered when the voltage value of the output voltage signal Vout is kept below a first threshold, or to output the adjustment voltage signal Vp_out when the voltage value of the output voltage signal Vout is greater than or equal to the first threshold. One terminal of the output capacitor Cout is connected to the second terminal of the switching transistor Q, and the other terminal of the output capacitor Cout is grounded.

[0038] The switching transistor remains on while the output voltage signal Vout is below a first threshold, and intermittently turns on and off when the output voltage signal Vout is greater than or equal to the first threshold. Furthermore, since the first terminal of the switching transistor Q is connected to the input terminal of the overvoltage protection unit (i.e., the output terminal of the LC-π filter circuit), and the second terminal is connected to the output terminal of the overvoltage protection unit, when the switching transistor Q is off, the output current signal from the LC-π filter circuit to the overvoltage protection unit will be zero until the switching transistor turns on again. This means the output current signal from the LC-π filter circuit to the overvoltage protection unit will be discontinuous, causing the output capacitor Cout to repeatedly charge and discharge as the switching transistor Q intermittently turns on and off, resulting in a sawtooth waveform for the adjustment voltage signal Vp_out.

[0039] Optionally, the overvoltage protection unit 201 further includes an overvoltage protection control module 2011, which may be an overvoltage protection control integrated circuit (IC). The control terminal of the switching transistor Q is connected to the overvoltage protection control module 2011, and the overvoltage protection control module 2011 is configured to: operate in normal mode when the voltage value of the output voltage signal Vout remains below a first threshold, outputting a valid level control signal to the control terminal of the switching transistor Q to keep the switching transistor on; and operate in overvoltage protection mode when the voltage value of the output voltage signal Vout is greater than or equal to the first threshold, outputting an intermittent valid level control signal to the control terminal of the switching transistor Q to intermittently turn the switching transistor Q on and off.

[0040] Optionally, the overvoltage protection unit 201 further includes a voltage detection circuit 2012. One end of the voltage detection circuit 2012 is connected to the output terminal of the overvoltage protection unit 201, and the other end of the voltage detection circuit 2012 is grounded. It is used to detect the voltage value of the output voltage signal Vout. The voltage detection circuit 2012 provides a voltage detection signal to the overvoltage protection control module 2011. When the value of the voltage detection signal is greater than or equal to a first voltage detection threshold corresponding to a first threshold, the overvoltage protection control module enters an overvoltage protection mode and controls the switching transistor Q to turn off until the value of the voltage detection signal drops to a predetermined proportion of the first voltage detection threshold. Then, it controls the switching transistor Q to turn on again until the value of the voltage detection signal is again greater than or equal to the first voltage detection threshold corresponding to the first threshold.

[0041] Optionally, an example of the voltage detection circuit 2012 includes a resistor divider circuit consisting of resistors RF1 and RF2 connected in series, wherein the ratio of a first voltage detection threshold to a first threshold is determined by the resistance values ​​of RF1 and RF2.

[0042] Furthermore, when the overvoltage protection control module 2011 operates in normal mode, as an example and not a limitation, the effective level control signal output by the overvoltage protection control module 2011 to the control terminal of the switching transistor Q can enable the switching transistor Q to be fully turned on. When the overvoltage protection control module 2011 operates in overvoltage protection mode, when it is necessary to switch the switching transistor Q from off to on, to prevent the output capacitor Cout from being rapidly charged and reaching the first threshold again, one option is for the overvoltage protection control module 2011 to control the switching transistor Q to be in a partially on state. For example, in the overvoltage protection control mode, the level of each effective level control signal in the intermittent effective level control signal output by the overvoltage protection control module 2011 to the control terminal of the switching transistor Q gradually increases, causing the voltage at the control terminal of the switching transistor Q to gradually increase from a voltage value that causes the switching transistor to operate in a partially on state, thereby keeping the switching transistor Q partially on for a period of time, thus ensuring safe overvoltage protection. As the voltage level at the control terminal of the switching transistor gradually increases, when the voltage value of the output voltage signal is detected to reach the first threshold again, the overvoltage protection control module 2011 turns off the switching transistor by outputting an invalid level control signal. Then, when the voltage value of the output voltage signal Vout is detected to drop to a predetermined proportion of the first threshold, the overvoltage protection control module 2011 turns on the switching transistor Q again by applying an effective level control signal to the control terminal of the switching transistor. That is, at this time, the switching transistor Q is controlled to turn on according to the gradually increasing voltage at the control terminal of the switching transistor.

[0043] Meanwhile, when the level of a certain effective control signal applied to the control terminal of the switching transistor gradually increases to the point that the switching transistor is fully turned on and the voltage value of the output voltage signal is kept below the first threshold, it indicates that the filtered voltage signal Vin_filtered is used as the output voltage signal Vout, and the voltage value of the filtered voltage signal Vin_filtered has been kept below the first threshold. In this case, the overvoltage protection control module 2011 has switched back to normal mode.

[0044] In addition, by adopting such Figure 2BAs analyzed earlier, in the overvoltage protection circuit shown, when the overvoltage protection control module 2011 operates in overvoltage protection mode, the switching transistor intermittently turns on and off. When the switching transistor Q is off, no current flows into the LC-π filter circuit, and the inductor and capacitor inside the LC-π filter circuit form an oscillating loop. At this time, the voltage value of the filtered voltage signal Vin_filtered will also show a voltage spike due to the LC oscillation. However, the filtered voltage signal Vin_filtered with voltage spikes is only applied to the first terminal of the switching transistor Q. Therefore, it is only necessary to select a switching transistor of appropriate specifications. (For example, a metal-oxide-semiconductor field-effect transistor is selected that can withstand a maximum voltage value between its drain and source that is greater than or equal to the voltage value of the voltage spike.) This ensures that the internal circuitry of the overvoltage protection circuit (e.g., switching transistor, overvoltage protection control module, voltage detection circuit) and the subsequent circuitry of the overvoltage protection circuit (e.g., the internal power supply module of the TCU or directly connected control circuitry, detection circuitry, etc.) will not experience overvoltage. This provides the subsequent circuitry with a voltage within the normal range that ensures its normal operation, and allows the selection of subsequent circuitry with lower input voltages even under high input voltage conditions, thereby increasing the safety, adaptability, and reliability of the overvoltage protection circuitry.

[0045] The following is for reference. Figure 3 The waveform diagram of the voltage signal is used to further describe the working principle of the overvoltage protection circuit shown in Figure 2.

[0046] As shown in Figure 2 and Figure 3 As shown, when the input voltage signal Vin is within the normal range, where the highest value of this normal range is generally equal to the first threshold, the voltage detected by the voltage detection circuit located at the output of the overvoltage protection circuit is also less than the first voltage detection threshold corresponding to the first threshold. It can be determined that the voltage value of the filtered voltage signal Vin_filtered is also within the normal range (remaining less than the first threshold Vth). The overvoltage protection control module in the overvoltage protection unit 201 operates in normal mode, outputting a control signal with an effective level to the switching transistor Q to keep the switching transistor Q conducting, thereby continuing to directly output the filtered voltage signal Vin_filtered as the output voltage signal of the overvoltage protection circuit. Furthermore, this circuit has good electromagnetic compatibility performance.

[0047] When the input voltage signal Vin is greater than or equal to the highest value of the normal range, the voltage detected by the voltage detection circuit at the output of the overvoltage protection circuit is also greater than or equal to the first voltage detection threshold corresponding to the first threshold. It can be determined that the voltage value of the filtered voltage signal Vin_filtered also exceeds the normal range (greater than or equal to the first threshold Vth). At this time, the overvoltage protection control module in the overvoltage protection unit 201 outputs an invalid level control signal to control the switching transistor Q to turn off. After the switching transistor turns off, the output capacitor Cout begins to discharge, causing the voltage value on the output capacitor (i.e., the voltage value of the output voltage signal Vout) to begin to decrease.

[0048] When the voltage across the output capacitor Cout drops to a certain level (e.g., 90% Vth), the overvoltage protection control module in the overvoltage protection unit 201 re-outputs a valid control signal to drive the switching transistor to turn on. This allows the output capacitor Cout to be recharged using the filtered voltage signal Vin_filtered, causing the voltage across the output capacitor (i.e., the voltage of the output voltage signal Vout) to gradually increase. As analyzed earlier, in overvoltage protection mode, the level of the valid control signal output by the overvoltage protection control module at the control terminal of the switching transistor gradually increases, and the switching transistor is not directly and fully turned on at this time.

[0049] When the voltage on the output capacitor Cout rises to the first threshold again, the overvoltage protection control module in the overvoltage protection unit 201 outputs an invalid level control signal to turn off the switching transistor Q again to stop charging the output capacitor Cout, causing the voltage on the output capacitor Cout to gradually decrease again.

[0050] When the voltage across the output capacitor Cout drops again to a predetermined percentage (e.g., 90%) of the first threshold, the overvoltage protection control module in the overvoltage protection unit 201 activates the switching transistor again by outputting a control signal with an effective level. The switching transistor is not fully activated at this point, and it restarts charging the output capacitor, causing the voltage across the output capacitor to gradually increase. This process is repeated until the gradually increasing level at the control terminal of the switching transistor has caused it to fully activate, and the voltage across the output capacitor is detected to remain below the first threshold. Then, the switching transistor remains fully activated, and the filtered voltage signal Vin_filtered is directly output again as the output voltage signal of the overvoltage protection circuit.

[0051] It should be understood that, although Figure 3The waveform diagram shows that the effective level of the control signal applied to the control terminal of the switching transistor increases linearly. However, other implementation methods are also feasible, as long as the control signal can gradually change the switching transistor from a partially on state to a fully on state.

[0052] When the overvoltage protection control module of the overvoltage protection unit operates in overvoltage protection mode, with the switching transistor intermittently turning on and off, when the switching transistor is off, the LC-π filter circuit (LC) forms an oscillating loop. At this time, the voltage value of the filtered voltage signal Vin_filtered will exhibit a voltage spike due to the LC oscillation. However, this voltage spike is blocked by a switching transistor with appropriate specifications (e.g., a suitable metal-oxide-semiconductor field-effect transistor that can withstand the maximum voltage between its drain and source) and will not be transmitted to the output voltage signal Vout. Figure 3 As shown in the image.

[0053] According to another aspect of this disclosure, an overvoltage protection method based on the above-described overvoltage protection circuit is also proposed. Figure 4 An overvoltage protection method according to an embodiment of the present disclosure is shown.

[0054] In step 410, the input voltage signal is filtered by the LC-π filter circuit to obtain the filtered voltage signal.

[0055] In step 420, the overvoltage protection unit generates an output voltage signal for the overvoltage protection circuit based on the filtered voltage signal. When the voltage value of the output voltage signal is greater than or equal to the first threshold, an adjustment voltage signal different from the filtered voltage signal is output as the output voltage signal of the overvoltage protection circuit. The voltage value of the adjustment voltage signal is less than the first threshold. The adjustment voltage signal has a sawtooth waveform.

[0056] Optionally, step 420 includes: controlling the switching transistor to remain on when the voltage value of the output voltage signal is less than a first threshold; and intermittently turning on and off when the voltage value of the output voltage signal is greater than or equal to the first threshold, wherein the output capacitor repeatedly charges and discharges while the switching transistor is intermittently turned on and off, so that the adjustment voltage signal has a sawtooth waveform.

[0057] Optionally, step 420 includes: when the output voltage signal value remains below a first threshold, operating the overvoltage protection control module in normal mode to output an effective level control signal to the control terminal of the switching transistor, keeping the switching transistor on; and when the output voltage signal value is greater than or equal to the first threshold, operating the overvoltage protection control module in overvoltage protection mode to output intermittent effective level control signals to the control terminal of the switching transistor, causing the switching transistor to intermittently turn on and off. The level of each effective level control signal acting on the control terminal of the switching transistor gradually increases.

[0058] Optionally, step 420 includes: providing a voltage detection signal to the overvoltage protection control module via the voltage detection circuit; and, if the value of the voltage detection signal is greater than or equal to a first voltage detection threshold corresponding to a first threshold, controlling the overvoltage protection control module, which has already entered the overvoltage protection mode, to turn off the switching transistor until the value of the voltage detection signal drops to a predetermined proportion of the first voltage detection threshold; and then controlling the switching transistor to turn on again until the value of the voltage detection signal is again greater than or equal to the first voltage detection threshold corresponding to the first threshold, wherein the switching transistor is controlled to turn on based on the gradually increasing level at the control terminal of the switching transistor.

[0059] Optionally, step 420 above includes: when the overvoltage protection control module is operating in overvoltage protection mode, switching the overvoltage protection control module to normal mode when the switching transistor is fully turned on and the voltage value of the output voltage signal remains less than the first threshold.

[0060] Based on this overvoltage protection method, by placing the LC-π filter circuit in front of the overvoltage protection unit, even when the overvoltage protection control module in the overvoltage protection unit is working in overvoltage protection mode and the switching transistor is intermittently turned on and off, causing the LC-π filter circuit to generate voltage spikes due to LC oscillation, the voltage spikes can be isolated at the first terminal (input terminal) of the switching transistor. This ensures that neither the internal circuit of the overvoltage protection circuit nor the subsequent circuits of the overvoltage protection circuit will experience overvoltage, thus providing the subsequent circuits with a voltage within the normal range that can guarantee their normal operation. Furthermore, even with a high input voltage, a subsequent circuit with a lower input voltage can still be selected, increasing the safety, adaptability, and reliability of the overvoltage protection circuit.

[0061] While the subject matter has been described in detail with respect to various specific exemplary embodiments, each example is provided by way of explanation rather than limitation. Those skilled in the art, upon receiving the foregoing understanding, will readily make changes, variations, and equivalents to such embodiments. Therefore, the invention does not exclude the inclusion of such modifications, variations, and / or additions to the subject matter that will be obvious to those skilled in the art. For example, features illustrated or described as part of one embodiment may be used with another embodiment to produce yet another embodiment. Therefore, it is intended that this disclosure cover such changes, variations, and equivalents.

[0062] Specifically, although the accompanying drawings of this disclosure depict steps performed in a specific order for illustrative and discussion purposes, the methods of this disclosure are not limited to the specific illustrated order or arrangement. Without departing from the scope of this disclosure, the various steps of the described methods may be omitted, rearranged, combined, and / or adjusted in various ways.

[0063] Unless otherwise defined, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. It should also be understood that terms such as those defined in a common dictionary shall be interpreted as having a meaning consistent with their meaning in the context of the relevant art, and not as having an idealized or highly formalized meaning, unless expressly defined herein.

[0064] The foregoing description is intended to illustrate the present disclosure and should not be construed as limiting it. While several exemplary embodiments of the present disclosure have been described, those skilled in the art will readily understand that many modifications may be made to the exemplary embodiments without departing from the novel teachings and advantages of the present disclosure. Therefore, all such modifications are intended to be included within the scope of the present disclosure as defined by the claims. It should be understood that the foregoing description is intended to illustrate the present disclosure and should not be construed as limiting it to the specific embodiments disclosed, and modifications to the disclosed embodiments and other embodiments are intended to be included within the scope of the appended claims. The present disclosure is defined by the claims and their equivalents.

Claims

1. An overvoltage protection circuit, comprising: A π-filter circuit, consisting of an inductor and a capacitor, is used to filter the input voltage signal to obtain a filtered voltage signal. An overvoltage protection unit is configured to generate an output voltage signal for the overvoltage protection circuit based on the filtered voltage signal, and, when the voltage value of the output voltage signal is greater than or equal to a first threshold, output an adjustment voltage signal different from the filtered voltage signal as the output voltage signal of the overvoltage protection circuit, wherein the voltage value of the adjustment voltage signal is less than the first threshold. The overvoltage protection unit includes a switching transistor and an output capacitor. The first terminal of the switching transistor is connected to the input terminal of the overvoltage protection unit to receive the filtered voltage signal. The second terminal of the switching transistor is connected to the output terminal of the overvoltage protection unit to output a filtered voltage signal or an adjusted voltage signal. One end of the output capacitor is connected to the second terminal of the switching transistor, and the other end of the output capacitor is grounded. The switching transistor remains on when the output voltage signal value is below a first threshold; and intermittently turns on and off when the output voltage signal value is greater than or equal to the first threshold. The output capacitor repeatedly charges and discharges as the switching transistor is intermittently turned on and off, causing the adjustment voltage signal to exhibit a sawtooth waveform.

2. The overvoltage protection circuit according to claim 1, wherein, The overvoltage protection unit further includes an overvoltage protection control module, the control terminal of the switching transistor is connected to the overvoltage protection control module, and the overvoltage protection control module is configured to: When the output voltage signal remains below the first threshold, in normal mode, a valid control signal is output to the control terminal of the switching transistor to keep the switching transistor on. When the voltage value of the output voltage signal is greater than or equal to the first threshold, the system operates in overvoltage protection mode, outputting an intermittent effective level control signal to the control terminal of the switching transistor to cause the switching transistor to intermittently turn on and off.

3. The overvoltage protection circuit according to claim 2, wherein, The level of each effective level control signal in the intermittent effective level control signal applied to the control terminal of the switching transistor gradually increases.

4. The overvoltage protection circuit according to claim 3, wherein, The overvoltage protection unit further includes a voltage detection circuit, one end of which is connected to the output terminal of the overvoltage protection unit, and the other end of which is grounded. The voltage detection circuit provides a voltage detection signal to the overvoltage protection control module. When the value of the voltage detection signal is greater than or equal to a first voltage detection threshold corresponding to the first threshold, the overvoltage protection control module enters an overvoltage protection mode and controls the switching transistor to turn off until the value of the voltage detection signal drops to a predetermined proportion of the first voltage detection threshold. Then, it controls the switching transistor to turn on again until the value of the voltage detection signal is again greater than or equal to the first voltage detection threshold corresponding to the first threshold. The switching transistor is controlled to turn on based on the gradually increasing voltage at the control terminal of the switching transistor.

5. The overvoltage protection circuit according to claim 4, wherein, The overvoltage protection control module is also configured to: When operating in overvoltage protection mode, the system switches to normal mode when the switching transistor is fully turned on and the voltage value of the output voltage signal remains below the first threshold.

6. An overvoltage protection method, applied to the overvoltage protection circuit according to any one of claims 1-5, comprising: A π-filter circuit, consisting of an inductor and a capacitor, filters the input voltage signal to obtain a filtered voltage signal. The overvoltage protection unit generates an output voltage signal for the overvoltage protection circuit based on the filtered voltage signal. If the voltage value of the output voltage signal is greater than or equal to a first threshold, an adjustment voltage signal, different from the filtered voltage signal, is output as the output voltage signal of the overvoltage protection circuit. The voltage value of the adjustment voltage signal is less than the first threshold. The adjusted voltage signal has a sawtooth waveform.

7. The method according to claim 6, wherein, The overvoltage protection unit includes a switching transistor and an output capacitor. A first terminal of the switching transistor is connected to the input terminal of the overvoltage protection unit to receive the filtered voltage signal. A second terminal of the switching transistor is connected to the output terminal of the overvoltage protection unit to output a filtered voltage signal or an adjusted voltage signal. One end of the output capacitor is connected to the second terminal of the switching transistor, and the other end of the output capacitor is grounded. The overvoltage protection unit generates an output voltage signal for the overvoltage protection circuit based on the filtered voltage signal, and when the voltage value of the output voltage signal is greater than or equal to a first threshold, it outputs an adjustment voltage signal different from the filtered voltage signal as the output voltage signal of the overvoltage protection circuit, including: The switching transistor is controlled to remain on when the voltage value of the output voltage signal is less than a first threshold; and to be intermittently turned on and off when the voltage value of the output voltage signal is greater than or equal to the first threshold, wherein the output capacitor repeatedly charges and discharges when the switching transistor is intermittently turned on and off, so that the adjustment voltage signal has a sawtooth waveform.

8. The method according to claim 7, wherein, The overvoltage protection unit further includes an overvoltage protection control module, and the control terminal of the switching transistor is connected to the overvoltage protection control module. The overvoltage protection unit generates an output voltage signal for the overvoltage protection circuit based on the filtered voltage signal, and when the voltage value of the output voltage signal is greater than or equal to a first threshold, outputs an adjustment voltage signal different from the filtered voltage signal as the output voltage signal of the overvoltage protection circuit, further comprising: When the output voltage signal remains below a first threshold, the overvoltage protection control module operates in normal mode, outputting a valid control signal to the control terminal of the switching transistor to keep the switching transistor on. When the voltage value of the output voltage signal is greater than or equal to the first threshold, the overvoltage protection control module is operated in overvoltage protection mode to output an intermittent effective level control signal to the control terminal of the switching transistor, so that the switching transistor is intermittently turned on and off.

9. The method according to claim 8, wherein, The level of each effective level control signal in the intermittent effective level control signal applied to the control terminal of the switching transistor gradually increases.

10. The method according to claim 9, wherein, The overvoltage protection unit includes a voltage detection circuit, one end of which is connected to the output terminal of the overvoltage protection unit, and the other end of which is grounded. The overvoltage protection unit generates an output voltage signal for the overvoltage protection circuit based on the filtered voltage signal, and when the voltage value of the output voltage signal is greater than or equal to a first threshold, outputs an adjustment voltage signal different from the filtered voltage signal as the output voltage signal of the overvoltage protection circuit, further comprising: The voltage detection circuit provides a voltage detection signal to the overvoltage protection control module. If the value of the voltage detection signal is greater than or equal to a first voltage detection threshold corresponding to the first threshold, the overvoltage protection control module, which has already entered the overvoltage protection mode, controls the switching transistor to turn off until the value of the voltage detection signal drops to a predetermined proportion of the first voltage detection threshold. Then, the switching transistor is controlled to turn on again until the value of the voltage detection signal is again greater than or equal to the first voltage detection threshold corresponding to the first threshold. The switching transistor is controlled to turn on based on the gradually increasing voltage at the control terminal of the switching transistor.

11. The method according to claim 9, wherein, The overvoltage protection unit generates an output voltage signal for the overvoltage protection circuit based on the filtered voltage signal, and when the voltage value of the output voltage signal is greater than or equal to a first threshold, outputs an adjustment voltage signal different from the filtered voltage signal as the output voltage signal of the overvoltage protection circuit, further comprising: When the overvoltage protection control module operates in overvoltage protection mode, it switches to normal mode when the switching transistor is fully turned on and the voltage value of the output voltage signal remains below the first threshold.

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