Counting type over-current protection circuit and method for alternating current over-current detection
By using a counting-type overcurrent protection circuit to perform time statistics and energy accumulation judgment on AC transient overcurrent, the problem of the inability to respond to AC peak overcurrent in a timely manner in the existing technology is solved, thus achieving effective protection of devices, extending service life and improving system reliability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHAANXI REACTOR MICROELECTRONICS
- Filing Date
- 2025-12-30
- Publication Date
- 2026-05-08
AI Technical Summary
Existing OCP circuits cannot respond to peak overcurrent in AC loads in a timely manner, leading to stress accumulation inside the device, which can damage or shorten its service life.
A counting-type overcurrent protection circuit is adopted, which uses a current detection module, a high-speed comparator, a reset module, a counter module, and an overcurrent protection logic module to perform time statistics and energy accumulation judgment, so as to achieve timely response to AC transient overcurrent.
Significantly improves system reliability, extends device lifespan, is compatible with DC OCP protection, enhances the cumulative detection capability of AC peak overcurrent, and reduces the impact of noise interference.
Smart Images
Figure CN122000828A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of overcurrent protection technology, and more specifically to a counting-type overcurrent protection circuit and protection method for AC overcurrent detection. Background Technology
[0002] Most existing overcurrent protection (OCP) circuits rely on the duration of DC overcurrents for detection; for example, they only trigger the protection mechanism when the overcurrent lasts for more than 1–4 microseconds (μs). However, in AC loads or high-speed switching applications, spurious spike currents often occur, lasting only 1 to 100 nanoseconds (ns) but with frequencies reaching tens of megahertz (MHz). Existing OCP circuits cannot respond promptly to these rapid transient overcurrents, leading to repeated spike currents that may accumulate stress within the device, potentially damaging the MOSFET or shortening its lifespan. Therefore, a novel OCP architecture capable of performing time statistics and energy accumulation assessment for AC transient overcurrents is urgently needed. Summary of the Invention
[0003] To address the problems in the prior art, this invention provides a counting-type overcurrent protection circuit and method for AC overcurrent detection, which can perform time statistics and energy accumulation judgment for AC transient overcurrent, significantly improving system reliability, better protecting devices, and extending device lifespan.
[0004] To achieve the above objectives, this invention provides a counting-type overcurrent protection circuit for AC overcurrent detection, including a current detection module. The current detection module outputs a detected current and generates a corresponding voltage signal. The output terminal of the current detection module is connected to the positive input terminal of a high-speed comparator. The voltage signal is connected to the positive input terminal of the high-speed comparator, and a reference voltage is connected to the negative input terminal of the high-speed comparator. The high-speed comparator compares the voltage signal generated by the current detection module with the reference voltage. If the duration of the voltage signal exceeding the reference voltage is greater than a first threshold, the high-speed comparator outputs a high level. The output terminal of the current detection module is also connected to a reset module. The reset module outputs... The input terminal is connected to the output terminal of the high-speed comparator. The reset module is used to detect the overcurrent duration. If the detected overcurrent duration exceeds the second threshold, a high level is output to reset the current detection module. The output terminal of the high-speed comparator is also connected to the counter module. The input terminal of the counter module is connected to the period control module, and the output terminal of the counter module is connected to the overcurrent protection logic module. The period control module is used to reset the counter module at the end of the period. If the output of the high-speed comparator jumps high once, the counter module count value is incremented by 1. When the count reaches the set count threshold number of times, the OCP signal is triggered to enter the overcurrent protection logic module, and the overcurrent protection logic module performs the overcurrent protection action.
[0005] Furthermore, the current detection module includes a current detection circuit and a resistor RS. The first output terminal of the current detection circuit is connected to one end of the resistor RS, and the other end of the resistor RS is connected to GND. The second output terminal of the current detection circuit is connected to the positive input terminal of the high-speed comparator and the reset module, respectively.
[0006] Furthermore, the reset module includes a duration determination circuit and an NMOS reset transistor. The drain of the NMOS reset transistor is connected to the second output terminal of the current detection circuit, the source of the NMOS reset transistor is connected to GND, the gate of the NMOS reset transistor is connected to the output terminal of the duration determination circuit, and the input terminal of the duration determination circuit is connected to the output terminal of the high-speed comparator.
[0007] Furthermore, the duration determination circuit includes a rising edge delay module and a logic AND gate. The first path of the output signal of the high-speed comparator enters the rising edge delay module, and after delay, it is input to the first input terminal of the logic AND gate. The second path of the output signal of the high-speed comparator enters the second input terminal of the logic AND gate. The output of the logic AND gate is connected to the gate of the NMOS reset transistor to control the NMOS reset transistor to be turned on or off.
[0008] Furthermore, if the duration judgment circuit detects that the overcurrent time lasts for more than 1µs, the duration judgment circuit outputs a high level and resets the voltage signal output by the current detection module through the NMOS reset transistor.
[0009] Furthermore, the counter module includes four D flip-flops. The R terminals of all four D flip-flops are connected to the output terminal of the period control module, and the D terminals of all four D flip-flops are connected to their respective QN terminals. The CLK terminal of D flip-flop D1 is connected to the output terminal of the high-speed comparator, and the Q terminal of D flip-flop D1 is a 1-count output. The CLK terminal of D flip-flop D1 is connected to the QN output terminal of D flip-flop D3, the CLK terminal of D flip-flop D2 is connected to the QN output terminal of D flip-flop D4, the Q terminal of D flip-flop D2 is a 2-count output, the Q terminal of D flip-flop D3 is a 4-count output, and the Q terminal of D flip-flop D4 is an 8-count output.
[0010] This invention also provides a counting-type overcurrent protection method for AC overcurrent detection, employing the above-described counting-type overcurrent protection circuit for AC overcurrent detection, and comprising the following steps:
[0011] 1) The periodic control module sets the OCP observation period, and at the end of each observation period, the count value of the counter module is cleared to zero;
[0012] 2) The current detection module continuously detects the system current and inputs the voltage signal to the positive input terminal of the high-speed comparator;
[0013] 3) If the voltage signal exceeds the reference voltage for a duration greater than the first threshold, the high-speed comparator outputs a high level, the high-speed comparator output jumps high once, and the counter module count value increases by 1;
[0014] 4) If the high-level output of the high-speed comparator lasts for a longer period than the second threshold, the reset module resets the current signal, and the output of the high-speed comparator is pulled low.
[0015] 5) If the counter module counts more than the counting threshold, the counter module outputs an OCP signal to the overcurrent protection logic module, and the overcurrent protection logic module performs overcurrent protection.
[0016] Furthermore, the first threshold is 1 ns to 100 ns, and the second threshold is 1 μs.
[0017] Furthermore, the OCP observation period is 4μs to 10μs.
[0018] Furthermore, the counting threshold is 2 to 8 times.
[0019] Compared with the prior art, the circuit of this invention uses a current detection module to output a detected current and generate a corresponding voltage signal. A high-speed comparator compares the voltage signal generated by the current detection module with a reference voltage. If the voltage signal exceeds the reference voltage for a duration greater than a first threshold, the high-speed comparator outputs a high level. The reset module detects the overcurrent time; if the detected overcurrent duration exceeds a second threshold, it outputs a high level to reset the current detection module. The period control module resets the counter module at the end of the period. If the high-speed comparator output jumps high once, the counter module's count value is incremented by 1. When the count reaches a set count threshold number, a trigger is activated. An OCP signal is sent to the overcurrent protection logic module, which then executes the overcurrent protection action. This enables time statistics and energy accumulation judgment of AC transient overcurrent, allowing for timely response to rapid transient overcurrents. The circuit effectively improves the cumulative detection capability of AC peak overcurrents without increasing power consumption, significantly enhancing system reliability. Furthermore, the circuit is compatible with the original DC OCP protection function, providing OCP protection for continuous DC overcurrents as well, better protecting devices and extending their lifespan. EMI and other noise interference can be filtered out by reasonably setting the counting period and count value, improving the robustness of OCP. Attached Figure Description
[0020] Figure 1 This is a schematic diagram of the circuit structure of the present invention;
[0021] Figure 2 This is a schematic diagram of the duration determination circuit structure of the present invention;
[0022] Figure 3 This is a schematic diagram of the circuit structure of the counter module of the present invention;
[0023] Figure 4 This is the timing diagram for DC OCP protection;
[0024] Figure 5 This is a timing diagram for AC OCP protection. Detailed Implementation
[0025] The present invention will be further explained and described below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0026] This invention provides a counting-type overcurrent protection circuit for AC overcurrent detection, see details below. Figure 1 It includes a current detection module, a high-speed comparator, a reset module, a cycle control module, a counter module, and an overcurrent protection logic module. Within a fixed OCP observation period, if multiple instantaneous overcurrents are detected, the count is accumulated. When the count value reaches a preset threshold, it is determined to be a potential abnormal overcurrent and the protection is triggered.
[0027] Specifically, the current detection module outputs the detected current and generates a corresponding voltage signal. The output of the current detection module is connected to the positive input of a high-speed comparator, and the voltage signal is connected to the positive input of the high-speed comparator. The negative input of the high-speed comparator is connected to a reference voltage. The high-speed comparator compares the voltage signal generated by the current detection module with the reference voltage. If the voltage signal exceeds the reference voltage for a duration greater than a first threshold, the high-speed comparator outputs a high level. The output of the current detection module is also connected to a reset module, whose input is connected to the output of the high-speed comparator. The reset module detects the overcurrent duration. If the detected overcurrent duration exceeds a second threshold, it outputs a high level to reset the current detection module. The output of the high-speed comparator is also connected to a counter module, whose input is connected to a period control module, and whose output is connected to an overcurrent protection logic module. The period control module resets the counter module at the end of the period. If the high-speed comparator output jumps high once, the counter module's count value increments by 1. When the count reaches the set count threshold number, the OCP signal is triggered to enter the overcurrent protection logic module, which then performs overcurrent protection.
[0028] The current detection module includes a current detection circuit and a resistor RS. The current detection circuit outputs a detected current, which flows through the resistor RS to generate a corresponding voltage signal. This voltage signal is connected to the positive input terminal of the high-speed comparator.
[0029] The high-speed comparator module is used to compare the voltage signal generated by the current sensing module with the reference voltage (overcurrent threshold). Its positive input terminal is connected to the corresponding voltage signal, and its negative input terminal is connected to the reference voltage (overcurrent threshold). If the voltage signal exceeds the reference voltage, the output is high.
[0030] The reset module includes a 1µs duration judgment circuit and an NMOS reset transistor. If the overcurrent duration exceeds 1µs, the 1µs duration judgment circuit outputs a high level, resetting the voltage signal output by the current detection module through the NMOS reset transistor. Therefore, for a continuous DC overcurrent signal, the reset module converts it into an AC overcurrent signal with a period of 1µs. When the counter reaches the counting threshold, OCP is triggered.
[0031] Periodic control module: used to reset the counter at the end of the period, set the counting period (e.g., 8μs), and automatically reset to zero when the period expires.
[0032] Counter module: Each time the high-speed comparator output jumps, the count value increases by 1; when the counter reaches the set threshold number of times (e.g., 4 times), the OCP signal is triggered, and the overcurrent protection logic module is entered.
[0033] Overcurrent protection logic module: Performs overcurrent protection actions, such as powering off, shutting down the power transistor, or entering retry mode.
[0034] The first output of the current detection circuit is connected to one end of resistor RS, and the other end of resistor RS is connected to GND. The second output of the current detection circuit is connected to the positive input of the high-speed comparator and the drain of the NMOS reset transistor in the reset module. The source of the NMOS reset transistor is connected to GND, and its gate is connected to the output of the duration judgment circuit. The input of the duration judgment circuit is connected to the output of the high-speed comparator module. The negative input of the high-speed comparator module is connected to the overcurrent threshold. The input of the counter module is connected to the output of the period control module and the high-speed comparator module, respectively. The output of the counter module is connected to the overcurrent protection logic module.
[0035] More specifically, see Figure 2 The duration determination circuit includes a rising edge delay module and a logic AND gate. The first path of the output signal of the high-speed comparator enters the rising edge delay module, and after delay, it is input to the first input terminal of the logic AND gate. The second path of the output signal of the high-speed comparator enters the second input terminal of the logic AND gate. The output of the logic AND gate is connected to the gate of the NMOS reset transistor to control the NMOS reset transistor to be turned on or off.
[0036] Preferably, the rising edge delay module has a 1µs delay, that is, if the duration judgment circuit detects that the overcurrent time lasts for more than 1µs, the duration judgment circuit outputs a high level and resets the current signal through the NMOS reset transistor.
[0037] More specifically, see Figure 3 The counter module implements counting and reset functions through a series of D flip-flops with reset capabilities. Specifically, it includes four D flip-flops. The R terminals of all four D flip-flops are connected to the output of the period control module, and the D terminals of all four D flip-flops are connected to their respective QN terminals. The CLK terminal of D flip-flop D1 is connected to the output of the high-speed comparator, and the Q terminal of D flip-flop D1 is a 1-count output. The CLK terminal of D flip-flop D3 is connected to the QN output of D flip-flop D2, and the CLK terminal of D flip-flop D4 is connected to the QN output of D flip-flop D3. The Q terminal of D flip-flop D2 is a 2-count output, the Q terminal of D flip-flop D3 is a 4-count output, and the Q terminal of D flip-flop D4 is an 8-count output.
[0038] This invention also provides a counting-type overcurrent protection method for AC overcurrent detection, employing the above-described counting-type overcurrent protection circuit for AC overcurrent detection, and comprising the following steps:
[0039] (a) The period control module sets the OCP observation period. At the end of each observation period, the count value of the counter module will be cleared to zero.
[0040] (b) The current detection module continuously detects the system current and inputs the voltage signal to the positive input terminal of the high-speed comparator.
[0041] (c) If the duration of the voltage signal being greater than the reference voltage is greater than the first threshold, the high-speed comparator outputs a high level.
[0042] (d) When the high-speed comparator output jumps up once, the counter module's count increments by 1.
[0043] (e) If the high-level output of the high-speed comparator lasts for a duration greater than the second threshold, the reset module resets the voltage signal output by the current detection module, that is, the high-level output resets the output voltage signal of the current detection module, and the high-speed comparator output is pulled low.
[0044] (f) When the counter module counts more than the counting threshold number of times, it outputs an OCP signal to the overcurrent protection logic module to perform overcurrent protection actions, such as powering off, turning off the power transistor, or entering retry mode.
[0045] In the control method of the present invention, the first threshold is 1 ns to 100 ns, preferably 10 ns; the second threshold is 1 μs. The observation period is 4 μs to 10 μs, preferably 8 μs; the counting threshold can be set to 2 to 8 times, preferably 4 times.
[0046] The DC OCP protection timing using the circuit and control method of this invention is as follows: Figure 4As shown, the waveforms from top to bottom represent the comparator output signal, reset signal, period clearing signal, and OCP signal. Taking the counter threshold of 4 times as an example, once a DC overcurrent occurs, the comparator output will go high for 1μs. After that, the reset circuit will pull down the voltage signal output by the current detection module, thus pulling the comparator output low. After the reset signal ends, the comparator output signal will go high again. When the comparator output signal goes high for the fourth time, the counter will output a high-level OCP signal. The circuit will then eliminate the overcurrent through the protection logic circuit, and the comparator output will go low.
[0047] The AC OCP protection timing using the circuit and control method of this invention is as follows: Figure 5 As shown, the waveforms from top to bottom represent the high-speed comparator output signal, reset signal, period clearing signal, and OCP signal. If the AC signal is greater than the reference voltage for less than 1μs, the reset signal will not trigger. The counter will output a high-level OCP signal when the comparator output jumps high for the fourth time. The circuit will eliminate overcurrent through the protection logic circuit, and the comparator output will be pulled low. If the number of AC OCP triggers is less than 4 within a period (e.g., 8μs), the counter will not output a high-level OCP signal. Instead, it will start counting again after the clearing signal, and trigger OCP when it has counted four times.
[0048] The overcurrent protection circuit proposed in this invention can effectively improve the cumulative detection capability of AC peak overcurrent without increasing power consumption, thus significantly improving system reliability. The circuit of this invention is compatible with the original DC OCP protection function and also provides OCP protection for continuous AC overcurrent, better protecting devices, extending device lifespan, and improving the robustness of OCP by reasonably setting the counting period and count value to filter out noise interference such as EMI.
[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A counting-type overcurrent protection circuit for AC overcurrent detection, characterized in that, The system includes a current detection module, which outputs a detected current and generates a corresponding voltage signal. The output of the current detection module is connected to the positive input of a high-speed comparator, and the voltage signal is also connected to the positive input of the high-speed comparator. The negative input of the high-speed comparator is connected to a reference voltage. The high-speed comparator compares the voltage signal generated by the current detection module with the reference voltage. If the voltage signal exceeds the reference voltage for a duration greater than a first threshold, the high-speed comparator outputs a high level. The output of the current detection module is also connected to a reset module, whose input is connected to the output of the high-speed comparator. The reset module detects overcurrent duration. If the detected overcurrent duration exceeds a second threshold, it outputs a high level to reset the current detection module. The output of the high-speed comparator is also connected to a counter module, whose input is connected to a period control module, and whose output is connected to an overcurrent protection logic module. The period control module resets the counter module at the end of the period. If the high-speed comparator output jumps high once, the counter module's count value is incremented by 1. When the count reaches a set count threshold, an OCP signal is triggered, which enters the overcurrent protection logic module, which then performs overcurrent protection.
2. The counting-type overcurrent protection circuit for AC overcurrent detection according to claim 1, characterized in that, The current detection module includes a current detection circuit and a resistor RS. The first output terminal of the current detection circuit is connected to one end of the resistor RS, and the other end of the resistor RS is connected to GND. The second output terminal of the current detection circuit is connected to the positive input terminal of the high-speed comparator and the reset module, respectively.
3. The counting-type overcurrent protection circuit for AC overcurrent detection according to claim 2, characterized in that, The reset module includes a duration determination circuit and an NMOS reset transistor. The drain of the NMOS reset transistor is connected to the second output terminal of the current detection circuit, the source of the NMOS reset transistor is connected to GND, the gate of the NMOS reset transistor is connected to the output terminal of the duration determination circuit, and the input terminal of the duration determination circuit is connected to the output terminal of the high-speed comparator.
4. The counting-type overcurrent protection circuit for AC overcurrent detection according to claim 3, characterized in that, The duration determination circuit includes a rising edge delay module and a logic AND gate. The first path of the output signal of the high-speed comparator enters the rising edge delay module, and after delay, it is input to the first input terminal of the logic AND gate. The second path of the output signal of the high-speed comparator enters the second input terminal of the logic AND gate. The output of the logic AND gate is connected to the gate of the NMOS reset transistor to control the NMOS reset transistor to be turned on or off.
5. The counting-type overcurrent protection circuit for AC overcurrent detection according to claim 4, characterized in that, If the duration judgment circuit detects that the overcurrent time lasts for more than 1µs, the duration judgment circuit outputs a high level and resets the voltage signal output by the current detection module through the NMOS reset transistor.
6. The counting-type overcurrent protection circuit for AC overcurrent detection according to claim 1, characterized in that, The counter module includes four D flip-flops. The R terminals of the four D flip-flops are all connected to the output terminal of the period control module. The D terminals of the four D flip-flops are all connected to their respective QN terminals. The CLK terminal of D flip-flop D1 is connected to the output terminal of the high-speed comparator. The Q terminal of D flip-flop D1 is a count output for 1 time. The CLK terminal of the D flip-flop is connected to the QN output terminal of the D flip-flop D1, the CLK terminal of the D flip-flop D3 is connected to the QN output terminal of the D flip-flop D2, and the CLK terminal of the D flip-flop D4 is connected to the QN output terminal of the D flip-flop D3. The Q terminal of the D flip-flop D2 is a count output of 2, the Q terminal of the D flip-flop D3 is a count output of 4, and the Q terminal of the D flip-flop D4 is a count output of 8.
7. A counting-type overcurrent protection method for AC overcurrent detection, characterized in that, The counting-type overcurrent protection circuit for AC overcurrent detection according to any one of claims 1 to 6 includes the following steps: 1) The periodic control module sets the OCP observation period, and at the end of each observation period, the count value of the counter module is cleared to zero; 2) The current detection module continuously detects the system current and inputs the voltage signal to the positive input terminal of the high-speed comparator; 3) If the voltage signal exceeds the reference voltage for a duration greater than the first threshold, the high-speed comparator outputs a high level, the high-speed comparator output jumps high once, and the counter module count value increases by 1; 4) If the high-level output of the high-speed comparator lasts for a longer period than the second threshold, the reset module resets the current signal, and the output of the high-speed comparator is pulled low. 5) If the counter module counts more than the counting threshold, the counter module outputs an OCP signal to the overcurrent protection logic module, and the overcurrent protection logic module performs overcurrent protection.
8. The counting-type overcurrent protection method for AC overcurrent detection according to claim 9, characterized in that, The first threshold is 1 ns to 100 ns, and the second threshold is 1 μs.
9. The counting-type overcurrent protection method for AC overcurrent detection according to claim 9, characterized in that, The OCP observation period is 4μs to 10μs.
10. The counting-type overcurrent protection method for AC overcurrent detection according to claim 9, characterized in that, The counting threshold is 2 to 8 times.