Rapid overcurrent protection method

Abstract

The invention relates to a rapid overcurrent protection method, which is characterized in that a pulse width modulation signal (PWM signal) is processed and output by an MCU (Microprogrammed Control Unit) to a filtering unit, the pulse width modulation signal is converted into a reference voltage signal by the filtering unit, and an adjusting resistor and a divider resistor can be connected in series or in parallel by a switch unit through switch devices such as an MOS (Metal Oxide Semiconductor) tube and a triode; therefore, the resistance value of the divider resistor is changed, the rapid change of the finally output target voltage signal is realized, the rapid requirement of the current protection circuit is met, the over-current protection of electrical equipment under different working conditions or environments can be adapted, and the working reliability and stability of the equipment are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of safety circuits, and in particular to a fast overcurrent protection method. Background Art

[0002] When electrical equipment is running, short circuits and other faults may occur, generating large currents, which may damage the device at the least, or even cause safety hazards such as fires at the worst. Therefore, overcurrent protection measures need to be added to most electrical equipment. When the current on the key link is detected to be greater than a certain value, the current loop is automatically disconnected to protect the device. However, under different working conditions or environments, the current size that the electrical equipment needs to protect will also change, so the protection threshold of the overcurrent protection circuit needs to be adjusted to meet different needs.

[0003] In existing overcurrent protection circuits, the protection threshold is mostly adjusted by changing the duty cycle of the reference PWM signal. This solution can achieve online adjustment of the threshold, which can be achieved by simply changing the duty cycle of the reference PWM signal driven by the MCU processor. However, the problem with this solution is that the threshold adjustment speed is slow and cannot meet the needs of fast protection. Summary of the invention

[0004] A main purpose of the present invention is to overcome at least one of the above-mentioned defects and to provide a fast overcurrent protection method, which can increase the advance switching speed of the overcurrent protection circuit and improve the safety and reliability of the operation of electrical equipment.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is: The present invention provides a fast overcurrent protection method, which converts a pulse width modulation signal emitted by an MCU processor into a DC reference voltage signal through a filtering unit, and the reference voltage signal outputs a target voltage signal through the switch unit, and the target voltage signal output is used as a threshold voltage signal of an overcurrent protection circuit, wherein the switch unit includes a voltage divider circuit, at least one adjustment resistor and at least one switch element, the MCU processor is connected to each switch element and is used to control the on and off of each switch element, and each adjustment resistor is controllably connected to the voltage divider circuit through the switch element, and is used to adjust the output voltage signal of the voltage divider circuit, and the output voltage signal of the voltage divider circuit is the target voltage signal.

[0006] According to one embodiment of the present invention, the target voltage signal is divided into two paths, one path is input into the MCU processor as feedback, and the other path is connected to the overcurrent protection circuit.

[0007] According to one embodiment of the present invention, the filtering unit includes at least one RC filter, and the RC filter converts the pulse width modulation signal into the reference voltage signal.

[0008] According to one embodiment of the present invention, the filtering unit includes a Butterworth filter, and the pulse width modulation signal is filtered by the RC filter and the Butterworth filter to form the reference voltage signal.

[0009] According to one embodiment of the present invention, the voltage divider circuit includes an operational amplifier, a first voltage divider resistor and a second voltage divider resistor, one end of the first voltage divider resistor is connected to the reference voltage signal, the other end of the first voltage divider resistor and one end of the second voltage divider resistor are connected in series, the other end of the second voltage divider resistor is connected to the ground terminal, the connection midpoint of the first voltage divider resistor and the second voltage divider resistor is connected to the operational amplifier, the operational amplifier constructs a voltage follower circuit, the output voltage of the operational amplifier is the target voltage signal, the second voltage divider resistor is connected in series or in parallel with each adjustment resistor, and the connection between each adjustment resistor and the second voltage divider resistor is controlled by turning on and off the switch.

[0010] According to one embodiment of the present invention, the adjusting resistor is connected in parallel with the second voltage-dividing resistor, the signal electrode of the switch element is connected in series with the adjusting resistor, the control electrode is connected to the output control terminal of the MCU processor, and the adjusting resistor can be controllably connected according to the IO control signal output by the MCU processor to adjust the output voltage of the voltage-dividing circuit.

[0011] According to one embodiment of the present invention, the adjusting resistor is connected in series between the second voltage-dividing resistor and the ground terminal, the signal electrode of the switch element is connected in parallel with the adjusting resistor, the control electrode is connected to the output control terminal of the MCU processor, and the adjusting resistor can be controllably connected according to the IO control signal output by the MCU processor to adjust the output voltage of the voltage-dividing circuit.

[0012] According to one embodiment of the present invention, the switch element is a MOS tube or a triode. Compared with the prior art, the advantages and beneficial effects of the fast overcurrent protection method of the patent application of the present invention are: In the fast overcurrent protection method of the present application, the MCU processes and outputs a pulse width modulation signal (PWM signal) to a filtering unit, which converts the pulse width modulation signal into a reference voltage signal. The switching unit can use switching devices such as MOS tubes and triodes to connect the adjustment resistor in series or in parallel with the voltage dividing resistor, thereby changing the resistance value of the voltage dividing resistor, thereby achieving a rapid change in the target voltage signal finally output to meet the rapidity requirements of the current protection circuit, and can adapt to the overcurrent protection of electrical equipment under different working conditions or environments, thereby improving the working reliability and stability of the equipment.

[0013] Furthermore, the MCU processor can still adjust the size of the reference voltage signal by changing the duty cycle of the pulse width modulation signal, and can also adjust the accuracy of the reference voltage signal by changing the frequency of the pulse width modulation signal. This adjustment can be performed during the debugging stage, and the method of switching control through the switching circuit in this application can be used to quickly adjust the overcurrent protection threshold when necessary. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Hereinafter, some specific embodiments of the present invention will be described in detail in an exemplary and non-limiting manner with reference to the accompanying drawings. The same reference numerals in the accompanying drawings indicate the same or similar components or parts. It should be understood by those skilled in the art that these drawings are not necessarily drawn to scale. In the accompanying drawings: Figure 1 is a principle block diagram of a fast overcurrent protection method according to an embodiment of the present invention; Figure 2 is a principle block diagram of a fast overcurrent protection method according to another embodiment of the present invention; Figure 3 is a principle block diagram of a fast overcurrent protection method according to another embodiment of the present invention; Figure 4 is a schematic diagram of the circuit structure of a filter unit in a fast overcurrent protection method according to an embodiment of the present invention; Figure 5 is a schematic diagram of the circuit structure of a switch unit in a fast overcurrent protection method according to an embodiment of the present invention; Figure 6 is a schematic diagram of the circuit structure of a switch unit in a fast overcurrent protection method according to another embodiment of the present invention; Figure 7 It is a schematic diagram of the circuit structure of a switch unit in a fast overcurrent protection method according to another embodiment of the present invention. DETAILED DESCRIPTION

[0015] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0016] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0017] This embodiment describes a fast overcurrent protection method. Figure 1 As shown, the system framework on which it is based can generally include an MCU processor, a filtering unit, and a switching unit. The pulse width modulation signal emitted by the MCU processor is converted into a DC reference voltage signal through the filtering unit. The reference voltage signal outputs a target voltage signal through the switching unit. The target voltage signal is output as a threshold voltage signal of the overcurrent protection circuit. The switching unit includes a voltage divider circuit, at least one adjustment resistor and at least one switch element. The MCU processor is connected to each switch element for controlling the on and off of each switch element. Each adjustment resistor is controllably connected to the voltage divider circuit through the switch element for adjusting the output voltage signal of the voltage divider circuit. The output voltage signal of the voltage divider circuit is the target voltage signal.

[0018] The MCU processes and outputs a pulse width modulation signal (PWM signal) to the filtering unit, which converts the pulse width modulation signal into a reference voltage signal. The switching unit can use switching devices such as MOS tubes and triodes to connect the adjustment resistor in series or in parallel with the voltage dividing resistor, thereby changing the resistance value of the voltage dividing resistor, thereby achieving rapid changes in the final output target voltage signal to meet the rapidity requirements of the current protection circuit, and can adapt to overcurrent protection of electrical equipment under different working conditions or environments, thereby improving the working reliability and stability of the equipment.

[0019] In one embodiment, Figure 2 As shown, the target voltage signal is divided into two paths, one path is input into the MCU processor as feedback, which can facilitate the MCU processor to monitor the target voltage signal output by the switch unit, and the other path is connected to the overcurrent protection circuit as the threshold voltage of the overcurrent protection circuit. The real-time current of the electrical equipment is collected and converted into voltage and then compared with the target voltage signal. If it is greater than the threshold voltage (target voltage signal), the overcurrent protection circuit is started and the electrical equipment is disconnected and stopped.

[0020] In addition, if Figure 3As shown, a circuit for protecting the output voltage stability may also be provided at the rear end of the switch unit, such as a voltage output protection circuit such as a follower or a voltage stabilizer, which can prevent the target voltage signal from being affected by the subsequent load and change, thereby ensuring the stability of the output target voltage signal.

[0021] like Figure 4 As shown, the filtering unit includes an RC filter, which is composed of a resistor R1 and a capacitor C1. The RC filter converts the pulse width modulation signal into the reference voltage signal. The reference voltage signal is a DC signal, and the voltage value of the DC reference signal is V=D*(VOH-VOL), where D is the duty cycle of the pulse width modulation signal, VOH is the low level voltage value of the pulse width modulation signal, and VOL is the low level voltage value of the pulse width modulation signal. The number of RC filters in the filtering unit can be increased according to demand, and the increase of RC filters can improve the accuracy of the reference voltage signal.

[0022] In addition, the filtering unit includes a Butterworth filter, which is composed of a resistor R2, a resistor R3, a resistor R4, a capacitor C2, a capacitor C3 and an operational amplifier U1, and the pulse width modulated signal is filtered by the RC filter and the Butterworth filter to form the reference voltage signal. The pulse width modulated signal generated by the MCU is filtered by combining the RC filter and the Butterworth filter, and the pulse width modulated signal after two filterings can be converted into a high-precision DC reference voltage.

[0023] like Figures 5 to 7 As shown, the voltage-dividing circuit includes an operational amplifier U2, a first voltage-dividing resistor R5 and a second voltage-dividing resistor R6, one end of the first voltage-dividing resistor R5 is connected to the reference voltage signal, the other end of the first voltage-dividing resistor R5 and one end of the second voltage-dividing resistor R6 are connected in series, the other end of the second voltage-dividing resistor R6 is connected to the ground, the connection midpoint of the first voltage-dividing resistor R5 and the second voltage-dividing resistor R6 is connected to the operational amplifier U2, the operational amplifier U2 constructs a voltage follower circuit and acts as a follower, the output voltage of the operational amplifier U2 is the target voltage signal, the second voltage-dividing resistor R6 is connected in series or in parallel with each adjusting resistor, and the connection between each adjusting resistor and the second voltage-dividing resistor R6 is controlled by turning on and off the switch.

[0024] Figure 5Take the parallel connection of the regulating resistor and the second voltage-dividing resistor R6 as an example. The first regulating resistor R10 is connected in series with the signal pole of the first switch Q1 and then connected in parallel with the second voltage-dividing resistor R6. The second regulating resistor R11 and the third regulating resistor R12 are connected in series with the signal pole of the second switch Q2 and then connected in parallel with the second voltage-dividing resistor R6. The MCU processor has two IO control signals, which respectively control the on and off of the first switch Q1 and the second switch Q2. In this way, each regulating resistor can be controlled to be connected according to the IO control signal output by the MCU processor. After the connection, the resistance value of the lower voltage-dividing resistor of the voltage-dividing circuit changes from the second voltage-dividing resistor R6 to the resistance after the second voltage-dividing resistor R6 is connected in parallel with the regulating resistor, so that the resistance value of the lower voltage-dividing resistor in the voltage-dividing circuit can be changed, which is used to adjust the output voltage of the voltage-dividing circuit.

[0025] Figure 6 Take the adjustment resistor and the second voltage-dividing resistor R6 in series as an example. The fourth adjustment resistor R13 and the fifth adjustment resistor R14 are connected in series between the second voltage-dividing resistor R6 and the ground terminal, the two signal poles of the third switch Q3 are connected in parallel to the two ends of the series link formed by the fourth adjustment resistor R13 and the fifth adjustment resistor R14, and the two signal poles of the fourth switch Q4 are connected in parallel to the two ends of the fourth adjustment resistor. The MCU processor has two IO control signals, which respectively control the on and off of the third switch Q3 and the second switch Q2. In this way, the adjustment resistors can be controlled to be connected according to the IO control signal output by the MCU processor. After the connection, the resistance value of the lower voltage-dividing resistor of the voltage-dividing circuit changes from the second voltage-dividing resistor R6 to the resistance after the second voltage-dividing resistor R6 and the adjustment resistor are connected in series, which can also realize the change of the resistance value of the lower voltage-dividing resistor in the voltage-dividing circuit, which is used to adjust the output voltage of the voltage-dividing circuit.

[0026] Figure 7 Take the example of some regulating resistors connected in series with the second voltage-dividing resistor R6 and some regulating resistors connected in parallel with the second voltage-dividing resistor R6. It is not difficult to understand that the MCU processor has four IO control signals, which respectively control the on and off of the first switch Q1, the second switch Q2, the third switch Q3, and the second switch Q2. In this way, the regulating resistors can be controlled to be connected according to the IO control signals output by the MCU processor. After the connection, the resistance value of the lower-level voltage-dividing resistor of the voltage-dividing circuit changes from the second voltage-dividing resistor R6 to the resistance after the second voltage-dividing resistor R6 is connected in series and / or in parallel with the regulating resistor, which can also realize the change of the resistance value of the lower-level voltage-dividing resistor in the voltage-dividing circuit, which is used to adjust the output voltage of the voltage-dividing circuit.

[0027] It is understandable that by adjusting the different structures and different numbers of resistors, the target voltage can have different numbers of adjustment gears, which can be set according to user needs and will not be described in detail here.

[0028] In each of the above embodiments, the switch element may be a MOS tube or a triode, or may be other electronic devices that perform fast on-off control.

[0029] In addition, the MCU processor can still adjust the size of the reference voltage signal by changing the duty cycle of the pulse width modulation signal, and can also adjust the accuracy of the reference voltage signal by changing the frequency of the pulse width modulation signal. This adjustment can be performed during the debugging stage, and the method of switching control through the switching circuit in this application can be used to quickly adjust the overcurrent protection threshold when necessary.

[0030] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the contents of the present invention and implement them accordingly. They cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A fast overcurrent protection method, characterized in that: The pulse width modulation signal sent by the MCU processor is converted into a DC reference voltage signal through the filtering unit, and the reference voltage signal outputs a target voltage signal through the switching unit, and the target voltage signal output is used as a threshold voltage signal of the overcurrent protection circuit, wherein: The switch unit includes a voltage divider circuit, at least one adjustment resistor and at least one switch element. The MCU processor is connected to each switch element and is used to control the on and off of each switch element. Each adjustment resistor is controllably connected to the voltage divider circuit through the switch element and is used to adjust the output voltage signal of the voltage divider circuit. The output voltage signal of the voltage divider circuit is the target voltage signal.

2. The overcurrent protection method according to claim 1, characterized in that: The target voltage signal is divided into two paths, one path is input into the MCU processor as feedback, and the other path is connected to the overcurrent protection circuit.

3. The overcurrent protection method according to claim 1, characterized in that: The filtering unit includes at least one RC filter, and the RC filter converts the pulse width modulation signal into the reference voltage signal.

4. The overcurrent protection method according to claim 2, characterized in that: The filtering unit includes a Butterworth filter, and the pulse width modulation signal is filtered by the RC filter and the Butterworth filter to form the reference voltage signal.

5. The overcurrent protection method according to claim 1, characterized in that: The voltage-dividing circuit includes an operational amplifier, a first voltage-dividing resistor and a second voltage-dividing resistor, one end of the first voltage-dividing resistor is connected to the reference voltage signal, the other end of the first voltage-dividing resistor and one end of the second voltage-dividing resistor are connected in series, the other end of the second voltage-dividing resistor is connected to the ground, the connection midpoint of the first voltage-dividing resistor and the second voltage-dividing resistor is connected to the operational amplifier, the operational amplifier constructs a voltage follower circuit, the output voltage of the operational amplifier is the target voltage signal, the second voltage-dividing resistor is connected in series or in parallel with each adjustment resistor, and the connection between each adjustment resistor and the second voltage-dividing resistor is controlled by turning on and off the switch.

6. The overcurrent protection method according to claim 5, characterized in that: The regulating resistor is connected in parallel with the second voltage-dividing resistor, the signal electrode of the switch element is connected in series with the regulating resistor, the control electrode is connected to the output control end of the MCU processor, and the regulating resistor can be controllably connected according to the IO control signal output by the MCU processor to adjust the output voltage of the voltage-dividing circuit.

7. The overcurrent protection method according to claim 5 or 6, characterized in that: The regulating resistor is connected in series between the second voltage-dividing resistor and the ground terminal, the signal electrode of the switch element is connected in parallel with the regulating resistor, and the control electrode is connected to the output control terminal of the MCU processor. The regulating resistor can be controllably connected according to the IO control signal output by the MCU processor to adjust the output voltage of the voltage-dividing circuit.

8. The overcurrent protection method according to claim 1, characterized in that: The switch element is a MOS tube or a triode.

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