Overcurrent protection circuit, circuit board and electronic device

Abstract

The application relates to the technical field of circuit protection, in particular to an overcurrent protection circuit, a circuit board and an electronic device. The circuit comprises a signal sampling end, a first operational amplifier module and a first comparison module. The first operational amplifier module is designed to realize different signal amplification multiples corresponding to sampling signals of different frequencies. In the absence of current surge, the sampling signal maintains a low frequency, the first operational amplifier module amplifies the sampling signal at a relatively small first amplification multiple, and after the first comparison module, if the reference signal is not exceeded, the overcurrent protection of the processor will not be triggered. If the current surge occurs, the current rises at a very fast speed, which will cause the frequency of the sampling signal to exceed the preset frequency, the first operational amplifier module will amplify the sampling signal at a relatively larger second amplification multiple, so that the amplified sampling signal exceeds the reference signal faster, and then a protection signal is output to the processor to trigger the overcurrent protection faster.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of circuit protection, in particular to an overcurrent protection circuit, a circuit board and an electronic device. BACKGROUND

[0002] In the power electronics industry, the design of various switching circuits often cannot do without the use of switching devices, such as triodes, MOSFETs or IGBTs, to facilitate the control of circuit conduction and shutdown. Taking IGBT as an example, in general, when it is in a high-voltage and high-current environment, it is subjected to high electrical stress, and overcurrent and short circuit occur from time to time, resulting in damage to circuit components. Therefore, an overcurrent protection circuit is usually provided to control the shutdown of the switching device when the instantaneous large current exceeds the protection value. However, in the overcurrent protection scheme provided by the related art, due to the response time of the controller and the levels of the operational amplifier unit or the comparison unit in the hardware circuit, the current at the sampling point may have risen far above the protection value within the time from detecting that the large current exceeds the protection point to controlling the switching device to shut down, which may cause the IGBT to be subjected to overcurrent stress, and even cause the IGBT to explode. To address this issue, the related art uses high-speed operational amplifiers and high-speed comparators to reduce the system processing delay, or replaces the IGBT with a larger one to increase the maximum current limit of the system, but this will sacrifice the cost advantage. SUMMARY

[0003] The embodiments of the present application mainly solve the technical problem of slow response speed of the overcurrent protection method in the prior art.

[0004] To solve the above technical problems, one technical solution adopted by the embodiments of the present application is to provide an overcurrent protection circuit, comprising: a signal sampling end, a first operational amplifier module and a first comparison module, a first end of the first operational amplifier module being connected to the signal sampling end, a second end of the first operational amplifier module being connected to a first input end of the first comparison module, a second input end of the first comparison module being configured to receive a reference signal, a third end of the first comparison module being configured to be connected to a processor, and a ground end of the first comparison module being grounded; the signal sampling end is configured to obtain a sampling signal; the first operational amplifier module is configured to amplify the sampling signal by a first amplification multiple when the frequency of the sampling signal is lower than a preset frequency, and amplify the sampling signal by a second amplification multiple when the frequency of the sampling signal is higher than the preset frequency, wherein the second amplification multiple is greater than the first amplification multiple; and the first comparison module is configured to output a protection signal to the processor when the amplified sampling signal is greater than the reference signal, so as to trigger the overcurrent protection by the processor.

[0005] The first operational amplification module is configured to realize different signal amplification multiples corresponding to different frequencies of the sampling signal. Specifically, the first operational amplification module is configured to realize a first amplification multiple for signal amplification of the sampling signal below a preset frequency, and realize a second amplification multiple for signal amplification of the sampling signal above the preset frequency. The first comparison module is configured to trigger the overcurrent protection when the amplified sampling signal exceeds the reference signal. Based on this, the current at the switching device is stable, and the sampling signal maintains a low frequency without a sudden increase in current. The first operational amplification module amplifies the sampling signal with a relatively small first amplification multiple. If the amplified sampling signal does not exceed the reference signal, the overcurrent protection of the processor (e.g., a single-chip microcomputer) is not triggered. If a sudden increase in current occurs, for example, a transient large current, the current rises very quickly, which causes the frequency of the sampling signal to suddenly increase and exceed the preset frequency. At this time, the first operational amplification module amplifies the sampling signal with a relatively large second amplification multiple, so that the amplified sampling signal exceeds the reference signal more quickly, and the first comparison module outputs a protection signal to the processor (e.g., a single-chip microcomputer) more quickly to trigger the overcurrent protection. That is, compared with the conventional overcurrent protection scheme, the present scheme additionally increases the transmission speed of the high-frequency sampling signal, reduces the response time from detection of the transient large current to triggering of the overcurrent protection, improves the response speed of the overcurrent protection, and accordingly, the current at the switching device increases less within the response time, thereby reducing the risk of damage to the switching device caused by overcurrent protection delay.

[0006] To solve the above technical problems, another technical scheme adopted by the embodiments of the present application is to provide an overcurrent protection circuit, comprising: a signal sampling end, a second operational amplification module, and a second comparison module. The first end of the second operational amplification module is connected to the signal sampling end. The second end of the second operational amplification module is connected to the first input end of the second comparison module. The second input end of the second comparison module is used to receive a reference signal. The third end of the second comparison module is used to connect to a processor. The ground end of the second comparison module is grounded. The signal sampling end is used to obtain a sampling signal. The second operational amplification module is used to amplify the sampling signal by a first amplification multiple. When the frequency of the once-amplified sampling signal is lower than a preset frequency, the second comparison module is used to output a protection signal to the processor to trigger the overcurrent protection of the processor when the once-amplified sampling signal is greater than the reference signal. When the frequency of the once-amplified sampling signal is higher than the preset frequency, the second comparison module is further used to amplify the once-amplified sampling signal by a third amplification multiple, and output a protection signal to the processor to trigger the overcurrent protection of the processor when the twice-amplified sampling signal is greater than the reference signal.

[0007] The second operational amplification module is arranged to realize the amplification function of the sampling signal. On the basis of the first signal amplification of the sampling signal by the second operational amplification module, the second comparison module is designed to realize the second amplification effect of the sampling signal with a frequency higher than the preset frequency. Based on this, the current at the switching device is stable, and there is no current surge. The sampling signal maintains a low frequency, and the second operational amplification module performs first signal amplification on the sampling signal. At this time, the amplified sampling signal does not trigger the overcurrent protection of the processor because the frequency is low and does not exceed the reference signal through the working of the second comparison module. If a current surge occurs, for example, a transient large current occurs, the current rises very fast, which can cause the frequency of the sampling signal to surge and exceed the preset frequency. After the signal amplification of the sampling signal by the second operational amplification module, the second comparison module performs signal amplification (second amplification third amplification multiple) on the first amplified sampling signal again, so that the second amplified sampling signal exceeds the reference signal faster, so that the second comparison module outputs the protection signal to the processor to trigger the overcurrent protection faster. That is, compared with the traditional overcurrent protection scheme, the present scheme reduces the response time from detecting the transient large current to triggering the overcurrent protection, improves the response speed of the overcurrent protection, and the current at the switching device increases less in the response time, thereby reducing the risk of damage to the switching device caused by overcurrent protection delay.

[0008] To solve the above technical problems, another technical scheme adopted by the embodiments of the present application is to provide a circuit board comprising the overcurrent protection circuit as described above.

[0009] To solve the above technical problems, another technical scheme adopted by the embodiments of the present application is to provide an electronic device comprising: a circuit board as described above, and a processor electrically connected to the overcurrent protection circuit in the circuit board.

[0010] Different from the related art, the overcurrent protection circuit, the circuit board and the electronic device are provided. The overcurrent protection circuit comprises a signal sampling end, a first operational amplifier module and a first comparison module. The circuit realizes different signal amplification multiples corresponding to different frequencies of the sampling signal by designing the first operational amplifier module, specifically, realizing a first amplification multiple signal amplification effect on the sampling signal lower than a preset frequency, realizing a second amplification multiple amplification effect on the sampling signal higher than the preset frequency, and setting the first comparison module to trigger the overcurrent protection effect when the amplified sampling signal exceeds the reference signal. Based on this, the current at the switching device is stable, and there is no current surge. The sampling signal maintains a low frequency, the first operational amplifier module amplifies the sampling signal with a relatively small first amplification multiple, and the first comparison module does not exceed the reference signal, so the overcurrent protection of the processor (such as a single-chip microcomputer) is not triggered. If a current surge occurs, for example, a transient large current occurs, the current rises very fast, which will cause the frequency of the sampling signal to surge and exceed the preset frequency. At this time, the first operational amplifier module amplifies the sampling signal with a relatively larger second amplification multiple, so that the amplified sampling signal exceeds the reference signal faster, so that the first comparison module outputs a protection signal to the processor (such as a single-chip microcomputer) faster to trigger the overcurrent protection. That is, compared with the traditional overcurrent protection scheme, the transmission speed of the high-frequency sampling signal is additionally increased, the response time from detecting the transient large current to triggering the overcurrent protection is reduced, the response speed of the overcurrent protection is improved, and based on this, the increase amplitude of the current at the switching device within the response time is smaller, and the risk of damage of the switching device caused by overcurrent protection delay is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 is a current situation diagram of a transient large current passing through a switching device provided by an embodiment of the present application;

[0012] Figure 2 is a structure diagram of an overcurrent protection circuit provided by an embodiment of the present application;

[0013] Figure 3 is a structure block diagram of an overcurrent protection circuit provided by an embodiment of the present application;

[0014] Figure 4a is a circuit diagram of an overcurrent protection circuit provided by an embodiment of the present application;

[0015] Figure 4b is Figure 4a unit division diagram of the circuit in the middle;

[0016] Figure 5 is a Bode diagram example corresponding to the overcurrent protection circuit in a certain scene provided by an embodiment of the present application;

[0017] Figure 6 is a comparison diagram of the protection point current when triggering overcurrent protection provided by an embodiment of the present application and prior art;

[0018] Figure 7 is a circuit schematic diagram of another overcurrent protection circuit provided by an embodiment of the present application;

[0019] Figure 8 is a structural schematic diagram of another overcurrent protection circuit provided by an embodiment of the present application;

[0020] Figure 9 is a circuit schematic diagram of another overcurrent protection circuit provided by an embodiment of the present application;

[0021] Figure 10 is a circuit schematic diagram of another overcurrent protection circuit provided by an embodiment of the present application. DETAILED DESCRIPTION

[0022] For the purpose of facilitating understanding of the present application, the present application is described in more detail below in combination with the drawings and specific embodiments. It should be noted that when one element is described as being “connected” to another element, it can be directly connected to the other element or one or more intermediate elements can be present therebetween. The terms “first”, “second”, and the like used in the present specification are only for the purpose of description and should not be understood as indicating or implying relative importance. Unless otherwise defined, all technical and scientific terms used in the present specification have the same meaning as understood by those skilled in the art to which the present application belongs. The terms used in the present specification are only for the purpose of describing specific embodiments of the present application and are not intended to limit the present application. The term “and / or” used in the present specification includes any and all combinations of one or more related listed items.

[0023] In the power technology industry, in order to ensure the normal work of switching devices in the use environment, an overcurrent protection circuit is usually designed to control the switching off of the switching device when the instantaneous large current exceeds the protection value, so as to prevent the switching device from being burned out due to the instantaneous large current. In the related art, due to the response time of each stage of operational amplifier unit or comparison unit in the hardware circuit and the controller itself, there is a large deviation between the current value when the switching device is controlled to be turned off and the set large current detection value. Please refer to Figure 1 , Figure 1 is a current condition diagram of an instantaneous large current passing through a switching device provided by an embodiment of the present application. As shown in Figure 1As shown, assuming that the set current protection value is A, which is about 97.8A in some scenarios, due to the delay in the sampling, comparison, MCU processing, driving and other stages in the overcurrent protection process, the overcurrent protection operation is actually triggered after the delay of (t2-t1), such as triggering IGBT clamping, or controlling the triode to be turned off, and the like. As shown in Figure 1 In this scenario, the delay time of (t2-t1) is about 5us, that is, the protection operation on the switching device is triggered 5 microseconds after the overcurrent condition (97.8A) is detected. In this case, the current value B corresponding to t2 is about 292.6A, which is about three times different from the set protection value A, that is, for every 1us of delay, the current at the switching device increases by about 40A. For this, there are ways to reduce system processing delay by using high-speed operational amplifiers and high-speed comparators in the related art, and there are ways to replace larger specification IGBT tubes to improve the maximum current upper limit of the system, but both will sacrifice cost advantage.

[0024] To solve the above problems, the embodiments of the present application creatively propose a solution concept, which utilizes the characteristic that the rapid increase of current causes the rapid increase of the frequency of the sampling signal, changes the amplification multiple of the high-frequency signal on the basis of not affecting the amplification multiple of the low-frequency signal, so that the high-frequency signal triggers the protection overcurrent protection faster, and reduces the delay time. That is, by shortening the delay time to limit the increase amplitude of the sampling point current within the delay time, the switching device is protected.

[0025] Please refer to Figure 2 The embodiments of the present application provide an overcurrent protection circuit. As shown, the overcurrent protection circuit 100 includes a signal sampling end (indicated by a circle in the figure), a first operational amplification module 11 and a first comparison module 12. The first end of the first operational amplification module 11 is connected to the signal sampling end, the second end of the first operational amplification module 11 is connected to the first input end of the first comparison module 12, the second input end of the first comparison module 12 is used to receive a reference signal, the third end of the comparison module 12 is connected to a processor, and a single-chip microcomputer is taken as an example in the figure, and the ground end of the first comparison module 12 is grounded.

[0026] Specifically, the signal sampling end is used to obtain the current signal at the switching device as a sampling signal, and IGBT is taken as an example of the switching device in the embodiments of the present application. The first operational amplification module 11 amplifies the sampling signal by a first amplification multiple when the frequency of the sampling signal is lower than a preset frequency, or amplifies the sampling signal by a second amplification multiple when the frequency of the sampling signal is higher than the preset frequency, and the second amplification multiple is greater than the first amplification multiple. The first comparison module 12 is used to compare the amplified sampling signal with the reference signal, and outputs a protection signal to the single-chip microcomputer when the amplified sampling signal is greater than the reference signal, so that the single-chip microcomputer triggers the overcurrent protection.

[0027] The first operational amplification module is configured to realize different signal amplification multiples corresponding to different frequencies of the sampling signal, specifically, realizing a first amplification multiple for signal amplification of the sampling signal below the preset frequency, and realizing a second amplification multiple for signal amplification of the sampling signal above the preset frequency, and the first comparison module is configured to realize the effect of triggering the overcurrent protection when the amplified sampling signal exceeds the reference signal. Based on this, the current at the switching device is stable, and there is no current surge. The sampling signal maintains a low frequency, the first operational amplification module amplifies the sampling signal with a relatively small first amplification multiple, and the first comparison module does not exceed the reference signal, so the overcurrent protection of the processor is not triggered. If a current surge occurs, for example, a transient large current occurs, the current rises very quickly, which will cause the frequency of the sampling signal to surge and exceed the preset frequency. At this time, the first operational amplification module amplifies the sampling signal with a relatively large second amplification multiple, so that the amplified sampling signal exceeds the reference signal more quickly, so that the first comparison module outputs a protection signal to the processor (such as a single-chip microcomputer) more quickly to trigger the overcurrent protection. That is, compared with the traditional overcurrent protection scheme, the transmission speed of the high-frequency sampling signal is additionally increased, the response time from detecting the transient large current to triggering the overcurrent protection is reduced, the response speed of the overcurrent protection is improved, and based on this, the increase amplitude of the current at the switching device within the response time is smaller, and the risk of damage to the switching device caused by overcurrent protection delay is reduced.

[0028] In some embodiments, please refer to Figure 3 The first operational amplification module 11 includes a first primary amplification unit 111 and a second absolute value unit 112. The first end of the first primary amplification unit 111 is connected to the signal sampling end, the second end of the first primary amplification unit 111 is connected to the first end of the second absolute value unit 112, and the second end of the second absolute value unit 112 is connected to the first input end of the first comparison module 12. The first primary amplification unit 111 can amplify the sampling signal by a first multiple when the frequency of the sampling signal is lower than the preset frequency, or can amplify the sampling signal by a second multiple when the frequency of the sampling signal is higher than the preset frequency. The second absolute value unit 112 can take the absolute value of the amplified sampling signal, so that the negative half cycle of the sampling signal is converted into a positive voltage with equal amplitude, so that the transmission of the converted sampling signal is adapted to the comparison process of the first comparison module 12.

[0029] Please refer to Figure 4a and Figure 4bThe first stage amplification unit 111 includes capacitors CA1 and CA2, a first amplifier U1A, capacitor C1, resistors R5, R1, R3, C2, R6, R2, and R4. The second stage absolute value unit 112 includes a second amplifier U1B, resistors R7, R8, and R9, and diode D1.

[0030] Specifically, such as Figure 4a and Figure 4b As shown, resistors R1 and R3 are connected in series, resistors R2 and R4 are connected in series, capacitor CA1 is connected in parallel across resistor R1, and capacitor CA2 is connected in parallel across resistor R2. The first input terminal U1A_2 of the first amplifier U1A is connected to the negative signal sampling terminal (shown as the sampling signal - in the diagram) through the series-connected resistors R1 and R3. The second input terminal U1A_3 of the first amplifier U1A is connected to the positive signal sampling terminal (shown as the sampling signal + in the diagram) through the series-connected resistors R2 and R4. The output terminal U1A_1 of the first amplifier U1A is connected to the first input terminal U1B_6 of the second amplifier U1B through resistor R7. The output terminal U1B_7 of the second amplifier U1B is connected to the anode of diode D1, and the cathode of diode D1 is connected to the first input terminal of the first comparator module 12. The first terminal of capacitor C2 is connected to the first input terminal of the first amplifier U1A, the second terminal of capacitor C2 is connected to the output terminal of the first amplifier U1A, and resistor R6 is connected in parallel across capacitor C2. The first end of capacitor C1 is connected to the second input terminal U1A_3 of the first amplifier U1A. The second end of capacitor C1 is connected to the second input terminal U1B_5 of the second amplifier U1B through resistor R8. Resistor R5 is connected in parallel across the two ends of capacitor C1. The two ends of resistor R9 are connected to the first input terminal of the second amplifier U1B and the cathode of diode D1, respectively.

[0031] Specifically, the first-stage amplification unit 111, through the configuration of the first amplifier U1A and peripheral circuitry, combined with capacitors CA1 and CA2, can amplify the sampled signal, providing two different amplification factors for sampled signals of different frequencies. Specifically, when the frequency of the sampled signal is less than a preset frequency, capacitors CA1 and CA2 are essentially open-circuited, with a first amplification factor of approximately R6 / (R1+R3); when the frequency of the sampled signal is greater than the preset frequency, capacitors CA1 and CA2 are essentially short-circuited, with a second amplification factor of approximately R6 / R3. That is, the first amplification factor R6 / (R1+R3) < the second amplification factor R6 / R3. Simultaneously, capacitors C1 and C2 also enable low-pass filtering, increasing the driving capability of the sampled signal while reducing noise interference.

[0032] In addition, in some application embodiments, the second end of the capacitor C1 is also connected with a bias voltage source of the comparator U1A, which is schematically shown as +1.625V, and can provide a bias voltage for the sampling signal, and cooperate with the second amplifier U1B to realize the effect of taking absolute value of the negative half cycle of the sampling signal, so that the negative half cycle of the alternating sampling signal becomes a positive voltage with equal amplitude, and the voltage value of the positive half cycle remains unchanged, thereby converting the whole sampling signal into a positive voltage, which is convenient for subsequent processing of the single-chip microcomputer.

[0033] The first comparison module 12 includes resistors R10, R11, R12, R13, R14, capacitors C3, C4, C5, and a comparator U2A.

[0034] As shown in Figure 4a and Figure 4b , the first input end U2A_2 of the comparator U2A is connected to the second end of the first operational amplifier module 11, i.e. the cathode of the diode D1, through the resistor R10. The second input end U2A_3 of the comparator U2A is connected to the resistor R11 and receives the reference signal through the resistor R11. The first end of the capacitor C3 is connected to the first input end of the comparator U2A, the second end of the capacitor C3 is connected to the ground end U2A_4 of the comparator U2A, which is schematically shown as GND, and the second input end U2A_3 of the comparator U2A is also grounded through the resistor R12, which is schematically shown as GND. The first end of the capacitor C4 is connected to the power supply end U2A_8 of the comparator U2A, and the second end of the capacitor C4 is grounded. The first end of the resistor R13 is connected to the output end U2A_1 of the comparator U2A, and the second end of the resistor R13 is connected to a single-chip microcomputer (not shown in the figure). The first end of the capacitor C5 is connected to the second end of the resistor R13, and the second end of the capacitor C5 is grounded. The second end of the resistor R13 is connected to an upper pull power supply, which is schematically shown as 3.3V, through the resistor R14.

[0035] In combination with the first comparison module 12, the resistors R11 and R12 divide the reference signal as a protection value for triggering the overcurrent protection, and the first comparison module 12 compares the sampling signal processed by the first operational amplifier module with the protection value. If the sampling signal is lower than the protection value, the comparator U2A outputs a high level, at this time, the resistor R14 as a pull-up resistor provides a high level to the single-chip microcomputer in combination with the power supply of the upper pull power supply; if the sampling signal exceeds the protection value, the comparator U2A outputs a low level as a protection signal to the single-chip microcomputer, and the single-chip microcomputer triggers the overcurrent protection operation based on the low level protection signal to close the IGBT drive and prevent the IGBT from being burned out by a large current.

[0036] In combination with Figure 5 , Figure 5is an example of the Bode diagram of the overcurrent protection circuit corresponding to a certain scene. It can be seen from the Bode diagram that the circuit basically has no gain increase below 1 kHz, can be effectively amplified by about 1.89 times at 7.87 kHz-93.6 kHz, and starts to attenuate and present low-pass characteristics after 261 kHz. That is, in combination with the high-frequency short-circuit characteristics of the capacitors CA1 and CA2, the overcurrent protection circuit can additionally amplify the sampling signal of high frequency, that is, the sampling signal of low frequency corresponds to a first amplification multiple, and the sampling signal of high frequency corresponds to a second amplification multiple larger than the first amplification multiple. Thus, in the case that the current at the switching device is stable and there is no sudden current surge, the sampling signal maintains a low frequency, and the first operational amplifier module amplifies the sampling signal with a relatively small first amplification multiple; if a current surge occurs, for example, a transient large current occurs, the current rises extremely fast, which causes the frequency of the sampling signal to surge and exceed the preset frequency. At this time, the first operational amplifier module amplifies the sampling signal with a relatively large second amplification multiple, so that the amplified sampling signal exceeds the reference signal faster, so that the first comparison module outputs a protection signal to the single-chip microcomputer to trigger overcurrent protection, thereby improving the response speed of overcurrent protection.

[0037] Based on this, please combine Figure 6 , Figure 6 is a comparison diagram of the protection point current when the present scheme and the prior art trigger overcurrent protection. Among them, curve a is a schematic diagram of the protection point current of the circuit provided by the present scheme when triggering overcurrent protection, which sets a larger second amplification multiple (compared with the first amplification multiple of normal low-frequency signal) for high-frequency signal; curve b is a schematic diagram of the protection point current of the circuit of the prior art when triggering overcurrent protection, which sets only one amplification multiple, i.e., the first amplification multiple, for sampling signals of any frequency. As shown in the figure, if the current protection value is 100 A, when a high-frequency sampling signal exceeding the preset frequency is detected, compared with the overcurrent protection circuit setting only a single amplification multiple, the present scheme sets a first high-frequency amplification module, which can amplify the sampling signal faster, so that the first comparison module in the circuit can control the single-chip microcomputer to trigger overcurrent protection faster. Taking the scenario in Figure 1 as an example, that is, the current at the switching device increases by about 40 A for every 1 us delay. In the scenario shown in the figure, the triggering speed corresponding to curve b is increased by about 3.2 us, that is, curve b can trigger overcurrent protection 3.2 us before curve a triggers overcurrent protection. Therefore, compared with the overcurrent protection circuit of the prior art setting only a single amplification multiple, the overcurrent protection circuit provided by the present scheme reduces the current value by 128 A when triggering overcurrent protection, and greatly reduces the risk of damage caused by IGBT overcurrent stress when triggering overcurrent protection.

[0038] In some embodiments, please combine Figure 7The first-stage amplification unit 111 in the circuit further includes a resistor RA1 and a resistor RA2. The resistor RA1 is connected in series with the capacitor CA1 to form a parallel branch of the resistor R1. The resistor RA2 is connected in series with the capacitor CA2 to form a parallel branch of the resistor R2. On this basis, the resistor RA1 and the resistor RA2 can assist in adjusting the first amplification multiple and the second amplification multiple in cooperation with the capacitor CA1 and the capacitor CA2, so that the second amplification multiple of the circuit for the high-frequency sampling signal is more suitable for actual use scenarios.

[0039] The embodiment of the present application provides a kind of overcurrent protection circuit, please combine Figure 8 The overcurrent protection circuit 1000 includes signal sampling end (in the figure, it is indicated with circle), second operational amplifier module 13 and second comparison module 14.The first end of second operational amplifier module 13 is connected signal sampling end, the second end of second operational amplifier module 13 is connected the first input end of second comparison module 14, the second input end of second comparison module 14 is used to receive reference signal, the third end of second comparison module 14 is used to connect processor, in the figure, with single-chip microcontroller as the example of processor, the ground terminal of second comparison module 14 is grounded.

[0040] Specifically, signal sampling end is used to obtain the current signal at switch device as sampling signal, in the embodiment of the present application, with IGBT as the example of switch device.Second operational amplifier module 13 will be amplified first amplification multiple after sampling signal, is transmitted to second comparison module 14.When the frequency of once amplified sampling signal is lower than preset frequency, second comparison module 14 is used to output protection signal to processor when once amplified sampling signal is greater than reference signal, in the embodiment of the present application, with single-chip microcontroller as the example of processor, to make processor trigger overcurrent protection;When the frequency of once amplified sampling signal is higher than preset frequency, second comparison module 14 is also used to amplify third amplification multiple after twice, and output protection signal to processor when twice amplified sampling signal is greater than reference signal, to make processor trigger overcurrent protection.

[0041] The second operational amplification module is arranged to realize the amplification function of the sampling signal. On the basis of the first signal amplification of the sampling signal by the second operational amplification module, the second comparison module is designed to realize the second amplification effect of the sampling signal with a frequency higher than the preset frequency. Based on this, the current at the switching device is stable, and there is no current surge. The sampling signal maintains a low frequency, and the second operational amplification module performs first signal amplification on the sampling signal. At this time, the amplified sampling signal does not trigger the overcurrent protection of the processor because the frequency is low and does not exceed the reference signal through the working of the second comparison module. If a current surge occurs, for example, a transient large current occurs, the current rises very fast, which will cause the frequency of the sampling signal to surge and exceed the preset frequency. After the signal amplification of the sampling signal by the second operational amplification module, the second comparison module performs signal amplification (second amplification third amplification multiple) on the first amplified sampling signal again, so that the second amplified sampling signal exceeds the reference signal faster, so that the second comparison module outputs the protection signal to the processor to trigger the overcurrent protection faster. That is, compared with the traditional overcurrent protection scheme, the response time from detecting the transient large current to triggering the overcurrent protection is reduced, the response speed of the overcurrent protection is improved, the increase amplitude of the current at the switching device within the response time is smaller, and the risk of damage of the switching device caused by the overcurrent protection delay is reduced.

[0042] Among them, please combine Figure 9 The second operational amplification module 13 includes a second first amplification unit 131 composed of a first amplifier U1A, a capacitor C1, a resistor R5, a resistor R3, a capacitor C2, a resistor R6 and a resistor R4, and a second absolute value unit 132 composed of a second amplifier U1B, a resistor R7, a resistor R8, a resistor R9 and a diode D1.

[0043] Specifically, the first input end of the first amplifier U1A is connected to the negative signal sampling end (indicated as sampling signal - in the figure) through the resistor R3, the second input end of the first amplifier U1A is connected to the positive signal sampling end (indicated as sampling signal + in the figure) through the resistor R4, the first end of the capacitor C2 is connected to the first input end of the first amplifier U1A, the second end of the capacitor C2 is connected to the output end of the first amplifier U1A, and the resistor R6 is connected in parallel to the two ends of the capacitor C2. The output end of the first amplifier U1A is connected to the first input end of the second amplifier U1B through the resistor R7, the first end of the capacitor C1 is connected to the second input end of the first amplifier U1A, the second end of the capacitor C1 is connected to the second input end of the second amplifier U1B through the resistor R8, the resistor R5 is connected in parallel to the two ends of the capacitor C1, the output end of the second amplifier U1B is connected to the anode of the diode D1, the cathode of the diode D1 is connected to the first input end of the second comparison module 14, and the two ends of the resistor R9 are respectively connected to the first input end of the second amplifier U1B and the cathode of the diode D1. The second operational amplifier module 13 can realize the signal amplification function of the sampling signal, which is a signal amplification process of the sampling signal once. The structure and function of the second-level absolute value unit 132 are the same as those of the second-level absolute value unit 112 in the overcurrent protection circuit 100 embodiment, and will not be described here.

[0044] The second comparison module 14 includes resistors R10, R11, R12, R13, R14, capacitors C3, C4, C5, CB1, RB1 and a comparator U2A.

[0045] Specifically, the first input end of the comparator U2A is connected to the second end of the second operational amplifier module 13, i.e. the cathode of the diode D1, through the resistor R10, the capacitor CB1 is connected in parallel to the two ends of the resistor R10, the second input end of the comparator U2A is connected to the resistor R11 and receives the reference signal through the resistor R11. The first end of the capacitor C3 is connected to the first input end of the comparator U2A, the second end of the capacitor C3 is connected to the ground end of the comparator U2A, and the resistor RB1 is connected in parallel to the two ends of the capacitor C3. The second input end of the comparator U2A is grounded through the resistor R12, which is indicated as GND in the figure. The first end of the capacitor C4 is connected to the power supply end of the comparator U2A, the second end of the capacitor C4 is grounded, the first end of the resistor R13 is connected to the output end of the comparator U2A, the second end of the resistor R13 is connected to the processor, and the second end of the resistor R13 is connected to the pull-up power supply through the resistor R14, which is indicated as 3.3V in the figure. The first end of the capacitor C5 is connected to the second end of the resistor R13, and the second end of the capacitor C5 is grounded.

[0046] Based on this, in the second comparison module 14, the capacitor CB1 cooperates with the comparator U2A and the peripheral circuit to further provide a signal amplification effect with a third amplification multiple for the high-frequency sampling signal with a frequency exceeding the preset frequency. Specifically, when the frequency of the sampling signal after the first amplification (by the second operational amplification module 13) is less than the preset frequency, the capacitor CB1 is equivalent to an open circuit and does not provide a signal amplification effect; when the frequency of the sampling signal after the first amplification (by the second operational amplification module 13) is greater than the preset frequency, the capacitor CB1 is equivalent to a short circuit, and the resistor RB1 and the comparator U2A and the peripheral circuit provide a signal amplification effect with a third amplification multiple for it, so that the amplified sampling signal exceeds the reference signal faster, so that the second comparison module 14 outputs the protection signal to the single-chip microcomputer to trigger the overcurrent protection faster, thereby improving the response speed of the overcurrent protection. Based on this, compared with the prior art overcurrent protection circuit that only provides a single amplification multiple, the overcurrent protection circuit provided in the present scheme can greatly reduce the risk of damage caused by the overcurrent stress of the IGBT when triggering the overcurrent protection.

[0047] In some embodiments, please refer to Figure 10 The second comparison module 14 in the overcurrent protection circuit 1000 further includes a resistor RB2, which is connected in series with the capacitor CB1 to form a parallel branch of the resistor R10. On this basis, the resistor RB2 can assist in adjusting the third amplification multiple together with the capacitor CB1, so that the third amplification multiple of the circuit for high-frequency signals is more suitable for actual use scenarios, thereby improving the application range of the circuit.

[0048] The present application embodiment provides a circuit board, which is provided with the above-mentioned overcurrent protection circuit. The circuit board can be a whole board or can be spliced from multiple boards. The circuit board has the corresponding functions and beneficial effects of the above-mentioned overcurrent protection circuit. Technical details not described in detail in the circuit board embodiment can be referred to the overcurrent protection circuit provided in the present application embodiment.

[0049] The present application embodiment provides an electronic device, which includes the above-mentioned circuit board and a processor electrically connected to the overcurrent protection circuit in the circuit board. For example, the processor can be a single-chip microcomputer. The electronic device has the corresponding functions and beneficial effects of the above-mentioned overcurrent protection circuit. Technical details not described in detail in the electronic device embodiment can be referred to the overcurrent protection circuit provided in the present application embodiment.

[0050] It should be noted that the preferred embodiments of the present application are described in the specification and its attached drawings, but the present application can be implemented in many different forms and is not limited to the embodiments described in the specification, and these embodiments are not intended to be additional limitations on the content of the present application, and the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive. Furthermore, each of the above technical features continues to combine to form various embodiments not listed above, which are considered to be within the scope of the present application specification; further, for those skilled in the art, the above description can be improved or changed, and all these improvements and changes shall fall within the scope of protection of the claims of the present application.

Claims

1. An overcurrent protection circuit, characterized by, The application relates to a signal sampling end, a first operational amplification module and a first comparison module, wherein the first end of the first operational amplification module is connected with the signal sampling end, the second end of the first operational amplification module is connected with the first input end of the first comparison module, the second input end of the first comparison module is used for receiving a reference signal, the third end of the first comparison module is used for connecting with a processor, and the ground end of the first comparison module is grounded. The signal sampling end is used for acquiring a sampling signal. The first operational amplification module is used for amplifying the sampling signal by a first amplification multiple when the frequency of the sampling signal is lower than a preset frequency, and is used for amplifying the sampling signal by a second amplification multiple when the frequency of the sampling signal is higher than the preset frequency, wherein the second amplification multiple is greater than the first amplification multiple. The first comparison module is used for outputting a protection signal to the processor to make the processor trigger an overcurrent protection when the amplified sampling signal is greater than the reference signal. The first operational amplification module comprises a first primary amplification unit and a secondary absolute value unit. The resistor R1 and the resistor R3 are connected in series, the resistor R2 and the resistor R4 are connected in series, the capacitor CA1 is connected in parallel to the two ends of the resistor R1, and the capacitor CA2 is connected in parallel to the two ends of the resistor R2. The first input end of the first amplifier U1A is connected to the signal sampling end of the negative pole through the series connection of the resistor R1 and the resistor R3, the second input end of the first amplifier U1A is connected to the signal sampling end of the positive pole through the series connection of the resistor R2 and the resistor R4, the first end of the capacitor C2 is connected to the first input end of the first amplifier U1A, the second end of the capacitor C2 is connected to the output end of the first amplifier U1A, and the resistor R6 is connected in parallel to the two ends of the capacitor C2. The output end of the first amplifier U1A is connected to the first input end of the secondary absolute value unit, the first end of the capacitor C1 is connected to the second input end of the first amplifier U1A, the second end of the capacitor C1 is connected to the second input end of the secondary absolute value unit, and the resistor R5 is connected in parallel to the two ends of the capacitor C1. The first primary amplification unit is used for amplifying the sampling signal by a first multiple when the frequency of the sampling signal is lower than a preset frequency, and is used for amplifying the sampling signal by a second multiple when the frequency of the sampling signal is higher than the preset frequency. The secondary absolute value unit is used for taking an absolute value of the amplified sampling signal, so that the negative half cycle of the sampling signal is converted into an equal-amplitude positive voltage, and the converted sampling signal is transmitted to the first comparison module. The secondary absolute value unit comprises a second amplifier U1B, a resistor R7, a resistor R8, a resistor R9 and a diode D1.

2. The overcurrent protection circuit of claim 1, wherein ​ The first input end of the second amplifier U1B is connected to the output end of the first amplifier U1A through the resistance R7, the second input end of the second amplifier U1B is connected to the second end of the capacitor C1 through the resistance R8, the output end of the second amplifier U1B is connected to the anode of the diode D1, the cathode of the diode D1 is connected to the first input end of the first comparison module, and the two ends of the resistance R9 are respectively connected to the first input end of the second amplifier U1B and the cathode of the diode D1.

3. The overcurrent protection circuit of claim 1, wherein, The first primary amplification unit further comprises a resistance RA1 and a resistance RA2, the resistance RA1 is connected in series with the capacitor CA1 to form a parallel branch of the resistance R1, and the resistance RA2 is connected in series with the capacitor CA2 to form a parallel branch of the resistance R2.

4. The overcurrent protection circuit of claim 1, wherein, The processor is a single-chip microcomputer.

5. The overcurrent protection circuit of claim 1, wherein, The first comparison module comprises a resistance R10, a resistance R11, a resistance R12, a resistance R13, a resistance R14, a capacitor C3, a capacitor C4, a capacitor C5 and a comparator U2A. The first input end of the comparator U2A is connected to the second end of the first operational amplification module through the resistance R10, the second input end of the comparator U2A is connected to the resistance R11 and receives a reference signal through the resistance R11, the first end of the capacitor C3 is connected to the first input end of the comparator U2A, and the second end of the capacitor C3 is connected to the ground end of the comparator U2A. The second input end of the comparator U2A is grounded through the resistance R12, the first end of the capacitor C4 is connected to the power supply end of the comparator U2A, the second end of the capacitor C4 is grounded, the first end of the resistance R13 is connected to the output end of the comparator U2A, the second end of the resistance R13 is connected to the processor, the second end of the resistance R13 is connected to the pull-up power supply through the resistance R14, the first end of the capacitor C5 is connected to the second end of the resistance R13, and the second end of the capacitor C5 is grounded.

6. An overcurrent protection circuit, characterized by It comprises: a signal sampling end, a second operational amplification module and a second comparison module, the first end of the second operational amplification module is connected to the signal sampling end, the second end of the second operational amplification module is connected to the first input end of the second comparison module, the second input end of the second comparison module is used for receiving a reference signal, the third end of the second comparison module is used for connecting a processor, and the ground end of the second comparison module is grounded; the signal sampling end is used for acquiring a sampling signal; the second operational amplification module is used for amplifying the sampling signal by a first amplification multiple; when the frequency of the sampling signal after one-time amplification is lower than a preset frequency, the second comparison module is used for outputting a protection signal to the processor when the sampling signal after one-time amplification is greater than the reference signal, so as to make the processor trigger an overcurrent protection. When the frequency of the once-amplified sampling signal is higher than a preset frequency, the second comparison module is further configured to amplify the once-amplified sampling signal for a second time by a third amplification multiple, and output a protection signal to the processor when the sampling signal amplified for the second time is greater than the reference signal, so as to make the processor trigger an overcurrent protection; The second operation amplification module comprises a second first-stage amplification unit composed of a first amplifier U1A, a capacitor C1, a resistor R5, a resistor R3, a capacitor C2, a resistor R6 and a resistor R4, and a second absolute value unit composed of a second amplifier U1B, a resistor R7, a resistor R8, a resistor R9 and a diode D1; A first input end of the first amplifier U1A is connected to a negative signal sampling end through the resistor R3, a second input end of the first amplifier U1A is connected to a positive signal sampling end through the resistor R4, a first end of the capacitor C2 is connected to the first input end of the first amplifier U1A, a second end of the capacitor C2 is connected to an output end of the first amplifier U1A, and the resistor R6 is connected in parallel to both ends of the capacitor C2; An output end of the first amplifier U1A is connected to a first input end of the second amplifier U1B through the resistor R7, a first end of the capacitor C1 is connected to a second input end of the first amplifier U1A, a second end of the capacitor C1 is connected to a second input end of the second amplifier U1B through the resistor R8, the resistor R5 is connected in parallel to both ends of the capacitor C1, an output end of the second amplifier U1B is connected to an anode of the diode D1, a cathode of the diode D1 is connected to a first input end of the second comparison module, and both ends of the resistor R9 are connected to the first input end of the second amplifier U1B and the cathode of the diode D1 respectively.

7. The overcurrent protection circuit of claim 6, wherein, The second comparison module comprises a resistor R10, a resistor R11, a resistor R12, a resistor R13, a resistor R14, a capacitor C3, a capacitor C4, a capacitor C5, a capacitor CB1, a resistor RB1 and a comparator U2A; A first input end of the comparator U2A is connected to a second end of the second operation amplification module through the resistor R10, the capacitor CB1 is connected in parallel to both ends of the resistor R10, a second input end of the comparator U2A is connected to the resistor R11 and receives a reference signal through the resistor R11, a first end of the capacitor C3 is connected to the first input end of the comparator U2A, a second end of the capacitor C3 is connected to a ground end of the comparator U2A, and the resistor RB1 is connected in parallel to both ends of the capacitor C3; The second input end of the comparator U2A is grounded through the resistor R12, the first end of the capacitor C4 is connected to the power supply end of the comparator U2A, the second end of the capacitor C4 is grounded, the first end of the resistor R13 is connected to the output end of the comparator U2A, the second end of the resistor R13 is connected to a processor, the second end of the resistor R13 is connected to a pull-up power supply through the resistor R14, the first end of the capacitor C5 is connected to the second end of the resistor R13, and the second end of the capacitor C5 is grounded.

8. The overcurrent protection circuit of claim 7, wherein, The second comparison module further comprises a resistor RB2 connected in series with the capacitor CB1 to form a parallel branch of the resistor R10.

9. A circuit board, characterized by The overcurrent protection circuit comprises the overcurrent protection circuit according to any one of claims 1-5; or the overcurrent protection circuit comprises the overcurrent protection circuit according to any one of claims 6-8.

10. An electronic device, comprising: The overcurrent protection circuit comprises: The circuit board according to claim 9, and a processor electrically connected to the overcurrent protection circuit in the circuit board.

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