Short circuit fault rapid detection circuit
By combining input voltage and load current detection into a fast short-circuit fault detection circuit, the problems of inaccurate short-circuit fault identification and delayed protection in existing technologies are solved, achieving fast and reliable short-circuit fault detection and protection.
Patent Information
- Application Number
- CN202422860378.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-22
- Publication Date
- 2025-10-31
- Estimated Expiration
- 2034-11-22
AI Technical Summary
Existing technologies have difficulty quickly and accurately identifying short circuit faults when detecting short circuits in load lines. They are particularly prone to falsely triggering protection under capacitive loads, and the delayed detection at startup leads to untimely protection, posing a safety hazard.
A fast short-circuit fault detection circuit was designed. By combining the detection of input voltage and load current, and utilizing an input voltage detection circuit, a load current detection circuit, and a shutdown execution circuit composed of discrete components, the short-circuit characteristics can be quickly identified, avoiding reliance on integrated circuits and microprocessor power supply delays, and achieving rapid protection.
It enables rapid and accurate identification and disconnection of the load line in the event of a short circuit, avoiding the problems of false triggering of protection by capacitive load and power-on delay, thus ensuring safety and reliability.
Smart Images
Figure CN223501145U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of circuit testing technology, and in particular to a fast short-circuit fault detection circuit. Background Technology
[0002] In applications such as electronic switches and power controllers, since the power supply may be provided by high-power sources such as batteries, a short circuit in the load line often generates a very large short-circuit current very quickly, causing serious damage, and in severe cases, even a fire.
[0003] Therefore, a key safety indicator in the design of such products is the ability to quickly disconnect the load line and isolate the power supply from the short circuit point when a short circuit occurs. Existing protection methods often employ current detection technology. When the current in the load line exceeds a set value, the protection circuit is triggered, disconnecting the load line. Current current detection technologies mainly fall into two categories: one uses Hall effect sensors to detect line current, with the Hall sensor providing an overcurrent signal; the other uses a low-resistance current-sensing resistor, amplifying the signal and transmitting it to the protection circuit before disconnecting the load line. Additionally, our company uses a combination of current transformers and DC resistors for detection, achieving a faster response speed. However, simply using the above methods has the following problems:
[0004] (1) Since only the load current is detected in the circuit, the protection circuit cannot easily distinguish whether an overcurrent or short circuit has actually occurred or the capacitive load is simply large when the capacitive load is large. As a result, the protection point is set too low, and the protection may be falsely triggered when the capacitive load starts; if the protection point is set too high, the protection will not be timely.
[0005] (2) For normally closed electronic switches or power controllers, if the short circuit occurs before the circuit is connected, the various detection circuits and microprocessor self-tests during the power supply power-on process may delay the detection current and the triggering of protection actions, resulting in a protection time interval that is too long and an irreparable fault may occur.
[0006] Therefore, we propose a fast short-circuit fault detection circuit to solve the above problems. Utility Model Content
[0007] To address the shortcomings of existing technologies, this invention provides a rapid short-circuit fault detection circuit to solve the technical problems in the prior art.
[0008] To achieve the above objectives, this utility model provides the following technical solution:
[0009] A fast short-circuit fault detection circuit includes an input voltage detection circuit, a load current detection circuit, and a shutdown execution circuit.
[0010] The input voltage detection circuit includes capacitor C4, resistors R3, R4, R5, R6, R7, R8, and R9, diode N2, and transistor VT1. Resistors R3 and R4 are connected in series and coupled to the two ends of the power supply. Resistor R3 is connected in parallel with capacitor C4. Resistors R6, R5, and N2 are connected in series and then in parallel across resistor R3.
[0011] The load current detection circuit includes a resistor RS1, an amplifier N3, and a capacitor C5. The positive and negative terminals of the resistor RS1 are coupled to pins 4 and 5 of the amplifier N3, respectively. Pins 1 and 3 of the amplifier are coupled to the positive and negative terminals of the capacitor C5, respectively. The capacitor is connected to an external power supply voltage VCC1.
[0012] The shutdown execution circuit includes a microcontroller N1, capacitors C2, C1, and C3, and resistors R1 and R2. Pin 1 of the microcontroller N1 is coupled to capacitor C2 and then grounded. Pin 2 of the microcontroller N1 is coupled to the collector of transistor VT2. Pin 3 of the microcontroller N1 is coupled to resistor R2, which is connected in parallel with capacitor C1.
[0013] As a preferred embodiment of this utility model, transistors VT3 and VT2 and resistor R9 are provided between the input voltage detection circuit and the shutdown execution circuit. The base of transistor VT3 is coupled between resistors R8 and R7, and the emitter of transistor VT3 is coupled to pin 2 of amplifier N3.
[0014] As a preferred embodiment of this utility model, the collector of transistor VT3 is coupled to the base of transistor VT2 via resistor R9, the collector of transistor VT2 is coupled to pin 2 of microcontroller N1, and the emitter of transistor VT2 is coupled to field-effect transistor VM1 via a load.
[0015] As a preferred embodiment of this invention, the gate of the field-effect transistor VM1 is coupled to pin 7 of the monolithic N1, and the drain of the field-effect transistor VM1 is coupled to pin 4 of the amplifier N3.
[0016] As a preferred embodiment of this utility model, the resistor R1 and resistor R2 are connected in series and then connected in parallel with capacitor C2, and capacitor C3 is connected between pin 6 and pin 8 of the microcontroller N1.
[0017] As a preferred embodiment of this utility model, the resistor R6 is coupled to the base of the transistor VT1, and the collector of the transistor VT1 is coupled to the resistor R7 via the resistor R8.
[0018] This utility model provides a fast short-circuit fault detection circuit, which has the following beneficial effects:
[0019] 1. Based on the mechanism of short circuit occurrence and common phenomena in the circuit, this utility model extracts the key characteristics of the circuit during a short circuit, designs a control circuit, accurately identifies short circuit protection, and provides rapid protection.
[0020] 2. The entire circuit can be completed with discrete components, without relying on the input power supply to establish and convert it into auxiliary power supply for the chip, processor self-test, etc., completely avoiding the delay caused by the above-mentioned work.
[0021] 3. By extracting key characteristics of the line during a short circuit, this invention avoids false triggering of short circuit protection caused by capacitive load during startup by combining undervoltage or input voltage rapid reduction signals with overcurrent signals.
[0022] 4. The detection and protection mechanism of this utility model does not rely on integrated circuits, microprocessors or other devices that require external power to operate. Therefore, it can react quickly in the case of short circuit before startup or startup before short circuit. Even if the input voltage is close to 0V after short circuit, it can prevent the shutdown of the actuator from starting. Attached Figure Description
[0023] Figure 1 This is a schematic diagram of the present invention;
[0024] Figure 2 This is the circuit diagram of this utility model. Detailed Implementation
[0025] To make the technical problems, technical solutions, and beneficial effects of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present utility model and are not intended to limit the present utility model.
[0026] Therefore, a feature pointed out in this specification is used to describe one feature of one embodiment of the present invention, and does not imply that every embodiment of the present invention must have the described feature. Furthermore, it should be noted that this specification describes many features. Although certain features may be combined to illustrate possible system designs, these features may also be used in other combinations not explicitly stated. Therefore, unless otherwise stated, the described combinations are not intended to be limiting.
[0027] The principle and structure of this utility model will be described in detail below with reference to the accompanying drawings and embodiments:
[0028] refer to Figure 1-2 A short-circuit fault fast detection circuit includes an input voltage detection circuit, a load current detection circuit, and a shutdown execution circuit.
[0029] The input voltage detection circuit includes capacitor C4, resistors R3, R4, R5, R6, R7, R8, and R9, diode N2, and transistor VT1. Resistors R3 and R4 are connected in series and coupled to the two ends of the power supply. Resistor R3 is connected in parallel with capacitor C4. Resistors R6, R5, and N2 are connected in series and then in parallel across resistor R3.
[0030] The load current detection circuit includes a resistor RS1, an amplifier N3, and a capacitor C5. The positive and negative terminals of the resistor RS1 are coupled to pins 4 and 5 of the amplifier N3, respectively. Pins 1 and 3 of the amplifier are coupled to the positive and negative terminals of the capacitor C5, respectively. The capacitor is connected to an external power supply voltage VCC1.
[0031] The shutdown execution circuit includes a microcontroller N1, capacitors C2, C1, and C3, and resistors R1 and R2. Pin 1 of the microcontroller N1 is grounded after being coupled to capacitor C2. Pin 2 of the microcontroller N1 is coupled to the collector of transistor VT2. Pin 3 of the microcontroller N1 is coupled to resistor R2. Resistor R2 is connected in parallel with capacitor C1. Resistor R1 and resistor R2 are connected in series and then in parallel with capacitor C2. Capacitor C3 is connected across pins 6 and 8 of the microcontroller N1. Resistor R6 is coupled to the base of transistor VT1. The collector of transistor VT1 is coupled to resistors R8 and R7.
[0032] The input voltage detection circuit and the shutdown execution circuit are provided with transistors VT3 and VT2 and resistor R9. The base of transistor VT3 is coupled between resistors R8 and R7, and the emitter of transistor VT3 is coupled to pin 2 of amplifier N3.
[0033] In this configuration, the collector of transistor VT3 is coupled to the base of transistor VT2 via resistor R9. The collector of transistor VT2 is coupled to pin 2 of microcontroller N1. The emitter of transistor VT2 is coupled to field-effect transistor VM1 via a load. The gate of field-effect transistor VM1 is coupled to pin 7 of microcontroller N1, and the drain of field-effect transistor VM1 is coupled to pin 4 of amplifier N3.
[0034] refer to Figure 1 Based on the mechanism of short circuit occurrence and common phenomena in circuits, this utility model extracts the key characteristics of the circuit when an electronic switch or power controller is short-circuited: after the load is short-circuited, before the circuit is disconnected, the input and output are directly connected, and the input voltage will drop significantly due to the output short circuit; the current in the circuit will increase rapidly. The circuit principle designed in this utility model synchronously detects the above two signals. When both signals are present at the same time, it immediately acts on the protection circuit. Discrete components are used in the circuit principle to avoid the use of active integrated circuits to prevent delays.
[0035] Specifically, in the diagram, C4, R3-R9, N2, and VT1 constitute the input voltage detection circuit, determining whether the input voltage is abnormally low or rapidly decreasing; RS1, N3, and C5 constitute the load current detection circuit, detecting changes in the current signal in the line; the signal received at the base of VT3 is the input undervoltage / rapid input voltage drop confirmation signal, and the signal received at the emitter of VT3 is the load current overload signal; VT2 executes the system shutdown signal, canceling the input signal of N1. The core circuit of N1 is the device shutdown actuator. This circuit provides the signal for VM1 to open the connection. When VT2 pulls down the input signal of N1, VM1 loses the drive signal of N1 and disconnects the line.
[0036] refer to Figure 2 The voltage divider signal from resistors R3 and R4 reflects the magnitude of the input voltage. This signal serves as the reference for N2. N2 conducting indicates a normal input voltage, while N2 being cut off indicates an excessively low input voltage or a rapid decrease in input voltage. When the input voltage decreases, the reference for N2 fails to reach the required threshold and stops conducting, causing VT1 to de-conduct. The function of capacitor C4 in the circuit is to accelerate the cutoff of N2 when the input voltage decreases rapidly, thereby speeding up the protection process.
[0037] Furthermore, the input undervoltage / rapid input voltage drop confirmation signal is that VT1 is not conducting.
[0038] Figure 2 In this circuit, the voltage signal of RS1 is obtained by multiplying the current flowing through RS1 by the resistance of RS1. This signal is appropriately amplified by N3 and connected to the emitter stage of VT3, where VT3 controls whether it is transmitted as a short-circuit signal. In this circuit, N3 and RS1 are replaced by a new circuit combining our company's current transformer and sensing resistor, which realizes the function of directly outputting overcurrent signal without chip power supply.
[0039] There is no cutoff voltage signal at the base of VT3, so VT3 can conduct current signals. The conducting current signals trigger VT2 to conduct, and VT2 pulls down the input signal of N1, eventually turning off VM1.
[0040] In applications, a signal latch-up circuit can be added to this part of the circuit to ensure reliable circuit disconnection after a short circuit.
[0041] The load current is too high signal when the signal output by N3 is greater than the set value. It needs to pass through VT3 and R9 to trigger VT2 to conduct fully.
[0042] The signal circuit for shutting down the system includes VT2, VT3, and R9. VT3 implements an AND relationship between the undervoltage signal and the short-circuit current signal, meaning that a short circuit is considered to have occurred only when both are present. VT2 is the actuator for this signal, removing the input signal from N1 to reliably disconnect VM1.
[0043] VM1 has its drain connected to the input and its source connected to the output. When VM1 is on, the entire line power supply provides power to the load. When VM1 is off, the electrical connection between the line power supply and the load is severed.
[0044] The undervoltage detection and control logic, overcurrent detection method, and shutdown mechanism used in the above circuit are merely an introduction to the principle of this utility model, and should not affect the claims of this utility model due to changes in local circuits.
[0045] The above description is merely a specific embodiment of this utility model, but the protection scope of this utility model is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this utility model, and these modifications or substitutions should all be covered within the protection scope of this utility model. Therefore, the protection scope of this utility model should be determined by the scope of the claims.
Claims
1. A fast short-circuit fault detection circuit, comprising an input voltage detection circuit, a load current detection circuit, and a shutdown execution circuit, characterized in that, The input voltage detection circuit includes capacitor C4, resistors R3, R4, R5, R6, R7, R8, R9, diode N2, and transistor VT1. Resistors R3 and R4 are connected in series and coupled to the two ends of the power supply. Resistor R3 is connected in parallel with capacitor C4. Resistors R6, R5, and N2 are connected in series and then in parallel across resistor R3. The load current detection circuit includes a resistor RS1, an amplifier N3, and a capacitor C5. The positive and negative terminals of the resistor RS1 are coupled to pins 4 and 5 of the amplifier N3, respectively. Pins 1 and 3 of the amplifier are coupled to the positive and negative terminals of the capacitor C5, respectively. The capacitor is connected to an external power supply voltage VCC1. The shutdown execution circuit includes a microcontroller N1, capacitors C2, C1, and C3, and resistors R1 and R2. Pin 1 of the microcontroller N1 is coupled to capacitor C2 and then grounded. Pin 2 of the microcontroller N1 is coupled to the collector of transistor VT2. Pin 3 of the microcontroller N1 is coupled to resistor R2, which is connected in parallel with capacitor C1.
2. The short-circuit fault fast detection circuit according to claim 1, characterized in that, Transistors VT3 and VT2 and resistor R9 are provided between the input voltage detection circuit and the shutdown execution circuit. The base of transistor VT3 is coupled between resistors R8 and R7, and the emitter of transistor VT3 is coupled to pin 2 of amplifier N3.
3. The short-circuit fault fast detection circuit according to claim 2, characterized in that, The collector of transistor VT3 is coupled to the base of transistor VT2 via resistor R9. The collector of transistor VT2 is coupled to pin 2 of microcontroller N1. The emitter of transistor VT2 is coupled to field-effect transistor VM1 via a load.
4. The short-circuit fault fast detection circuit according to claim 3, characterized in that, The gate of the field-effect transistor VM1 is coupled to pin 7 of the monolithic N1, and the drain of the field-effect transistor VM1 is coupled to pin 4 of the amplifier N3.
5. A fast short-circuit fault detection circuit according to claim 1, characterized in that, The resistors R1 and R2 are connected in series and then connected in parallel with the capacitor C2. A capacitor C3 is connected between pin 6 and pin 8 of the microcontroller N1.
6. The short-circuit fault fast detection circuit according to claim 1, characterized in that, The resistor R6 is coupled to the base of the transistor VT1, and the collector of the transistor VT1 is coupled to the resistor R7 via the resistor R8.