Power supply output short circuit and overcurrent protection circuit suitable for electric energy meter and terminal equipment

Abstract

The utility model discloses a power supply output short circuit and overcurrent protection circuit suitable for an electric energy meter and terminal equipment, which comprises a power supply input end VIN, a power supply output end VOUT, a current sampling circuit, a voltage monitoring circuit and a voltage output circuit. And the current sampling circuit and the voltage output circuit are connected in series between the power supply input end VIN and the power supply output end VOUT. The current sampling circuit is used for converting a current signal between the power input end VIN and the power output end VOUT into a voltage signal and outputting the voltage signal from the voltage signal output end. The voltage monitoring circuit is used for sending out a control signal according to the voltage signal, and the voltage output circuit controls the on-off of a circuit between the power input end VIN and the power output end VOUT according to the control signal output by the voltage monitoring circuit. According to the utility model, the sensitivity can be set in a reasonable range by adjusting the resistors and the capacitors, false triggering protection is avoided, and the circuit also has the advantages of low cost, flexible configuration, good compatibility and the like.

Description

Technical Field

[0001] The utility model relates to a power output short - circuit and over - current protection circuit. Background Art

[0002] At present, smart electricity meters generally need to be used in cooperation with external modules. For example, a single - phase electricity meter compliant with the DL / T 645 - 2007 standard needs to be externally connected with a carrier module, and in addition to the external carrier module, an Internet of Things electricity meter can also be equipped with 2 to 3 expansion modules. According to a large number of on - site operation experiences of smart electricity meters, these external modules may malfunction, which may lead to current overload or short - circuit problems in the power supply of the electricity meter, resulting in the electricity meter crashing or the power supply outputting over - power for a long time, or even burning out the power circuit.

[0003] To address the above problems, a failure protection circuit needs to be set at the power output interface of the electricity meter and the terminal device. The traditional solution is to use a customized over - current protection chip (i.e., an e - Fuse chip) to achieve the protection function, which has the following problems:

[0004] 1. The customization degree of the e - Fuse chip is relatively high. It was originally designed for the protection of USB interface power supplies, and its sensitivity requirements are extremely high (it is required to provide protection immediately after over - current is triggered, and the waiting time for over - current determination is usually 2 milliseconds). However, when the external module of the electricity meter starts up, a short - term large current may occur, which easily causes the e - Fuse chip to mis - trigger the over - current protection.

[0005] 2. The existing e - Fuse chip, as a customized integrated circuit, has a high cost and is not suitable for electricity meter and terminal device products.

[0006] 3. The existing e - Fuse chip, as a customized integrated circuit, cannot be flexibly configured according to the protection requirements of the circuit. Summary of the Utility Model

[0007] The utility model provides a power output short - circuit and over - current protection circuit applicable to electricity meters and terminal devices, aiming to solve the problems of high sensitivity of the existing protection scheme, easy mis - triggering of protection, high cost, and inability to be flexibly configured.

[0008] The technical solution of the utility model is as follows:

[0009] A power output short - circuit and over - current protection circuit applicable to electricity meters and terminal devices includes a power input terminal VIN and a power output terminal VOUT, and further includes a current sampling circuit, a voltage monitoring circuit, and a voltage output circuit;

[0010] The current sampling circuit and the voltage output circuit are serially arranged between the power input terminal VIN and the power output terminal VOUT;

[0011] The current sampling circuit is used to convert the current signal between the power input terminal VIN and the power output terminal VOUT into a voltage signal and output it from the voltage signal output terminal;

[0012] The voltage monitoring circuit includes a resistor R2, a resistor R3, a resistor R4, a capacitor C1 and a power supply monitoring chip D1; the resistor R2 and the resistor R3 are connected in series between the voltage signal output terminal of the current sampling circuit and the ground terminal to form a voltage dividing circuit, and both ends of the resistor R3 are respectively connected to the power supply terminal VCC and the ground terminal GND of the power supply monitoring chip D1, and the capacitor C1 is connected in parallel with the resistor R3; one end of the resistor R4 is connected to the power supply terminal VCC of the power supply monitoring chip D1, and the other end is connected to the reset output terminal RESET of the power supply monitoring chip D1; the reset output terminal RESET of the power supply monitoring chip D1 is the control signal output terminal of the voltage monitoring circuit;

[0013] The control signal input terminal of the voltage output circuit is connected to the control signal output terminal of the voltage monitoring circuit, and is used to control the on / off of the circuit between the power input terminal VIN and the power output terminal VOUT according to the control signal output by the voltage monitoring circuit.

[0014] As a further improvement of the power output short-circuit and over-current protection circuit applicable to the electric energy meter and the terminal device: the current sampling circuit includes a resistor R1, one end of the resistor R1 is connected to the power input terminal VIN, and the other end is connected to the power output terminal VOUT through the voltage output circuit; the other end of the R1 is the voltage signal output terminal of the current sampling circuit.

[0015] As a further improvement of the power output short-circuit and over-current protection circuit applicable to the electric energy meter and the terminal device: the voltage output circuit further includes a linear voltage regulator D2, the input terminal IN of the linear voltage regulator D2 is connected to the power input terminal VIN through the current sampling circuit, the output terminal OUT of the linear voltage regulator D2 is connected to the power output terminal VOUT, and the enable terminal EN of the linear voltage regulator D2 is connected to the control signal input terminal of the voltage output circuit.

[0016] As a further improvement of the power output short-circuit and over-current protection circuit applicable to the electric energy meter and the terminal device: the input terminal IN of the linear voltage regulator D2 is also grounded through a capacitor C2.

[0017] As a further improvement of the power output short-circuit and over-current protection circuit applicable to the electric energy meter and the terminal device: the voltage output circuit further includes a P-MOS transistor V1 and an N-MOS transistor V2;

[0018] The source electrode of the P-MOS transistor V1 is connected to the power input terminal VIN through the current sampling circuit, and the drain electrode is connected to the power output terminal VOUT;

[0019] The N-MOS transistor V2 is connected between the control signal input terminal of the voltage output circuit and the P-MOS transistor V1, and is used to realize the conversion of control logic and control the on / off of the P-MOS transistor V1.

[0020] As a further improvement of the power output short-circuit and over-current protection circuit applicable to the electric energy meter and the terminal device: the voltage output circuit further includes a resistor R5, a resistor R6, a capacitor C2 and a capacitor C3;

[0021] One end of the resistor R5 is connected to the source electrode of the P-MOS transistor V1, and the other end is connected to the drain electrode of the N-MOS transistor V2 through the resistor R6; the other end of the resistor R5 is also connected to the gate electrode of the P-MOS transistor V1; the source electrode of the N-MOS transistor V2 is grounded, and the gate electrode is connected to the control signal input terminal of the voltage output circuit; the capacitor C2 is connected in parallel with the resistor R5;

[0022] The drain electrode of the P-MOS transistor V1 is also grounded through the capacitor C3.

[0023] Compared with the prior art, the present utility model has the following positive effects:

[0024] 1. The filter capacitor C1 in the voltage monitoring circuit can filter out the pulsed voltage. By adjusting the capacitor C1 and the resistor, the waiting delay and the trigger voltage for triggering the over-current protection can be adjusted, so as to control the sensitivity of the voltage monitoring within a suitable range and avoid false triggering of the protection.

[0025] 2. This circuit is built based on common components, and has the advantages of low cost, short procurement cycle and high production efficiency.

[0026] 3. By adjusting the resistance value in the circuit and the linear voltage regulator or P-MOS in the voltage output circuit, more flexible configuration can be carried out, providing wide compatibility for different power supply voltages and output currents.

[0027] 4. Two different types of voltage output circuits are provided, and can be freely selected according to the requirements of voltage output accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is the circuit diagram of Embodiment 1;

[0029] Figure 2 is the circuit diagram of Embodiment 2. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] The technical solution of the present utility model will be described in detail below with reference to the drawings. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all of the embodiments. Embodiment 1

[0031] As Figure 1 , a power output short - circuit and over - current protection circuit applicable to an electric energy meter and a terminal device, includes a power input terminal VIN and a power output terminal VOUT, and further includes a current sampling circuit, a voltage monitoring circuit, and a voltage output circuit.

[0032] The current sampling circuit and the voltage output circuit are serially arranged between the power input terminal VIN and the power output terminal VOUT.

[0033] Specifically:

[0034] The current sampling circuit is used to convert the current signal between the power input terminal VIN and the power output terminal VOUT into a voltage signal and output it from the voltage signal output terminal.

[0035] In this embodiment, the current sampling circuit includes a resistor R1. One end of the resistor R1 is connected to the power input terminal VIN, and the other end is connected to the power output terminal VOUT through the voltage output circuit. The other end of the R1 is the voltage signal output terminal of the current sampling circuit.

[0036] The voltage monitoring circuit includes a resistor R2, a resistor R3, a resistor R4, a capacitor C1, and a power monitoring chip D1.

[0037] The model of the power monitoring chip D1 is SGM803B, and it includes a power supply terminal VCC, a grounding terminal GND, and a reset output terminal RESET.

[0038] The resistor R2 and the resistor R3 are serially connected between the voltage signal output terminal of the current sampling circuit and the grounding terminal to form a voltage - dividing circuit. Two ends of the resistor R3 are respectively connected to the power supply terminal VCC and the grounding terminal GND of the power monitoring chip D1, and the capacitor C1 is connected in parallel with the resistor R3. One end of the resistor R4 is connected to the power supply terminal VCC of the power monitoring chip D1, and the other end is connected to the reset output terminal RESET of the power monitoring chip D1. The reset output terminal RESET of the power monitoring chip D1 is the control signal output terminal of the voltage monitoring circuit.

[0039] The control signal input terminal of the voltage output circuit is connected to the control signal output terminal of the voltage monitoring circuit, and is used to control the on - off of the circuit between the power input terminal VIN and the power output terminal VOUT according to the control signal output by the voltage monitoring circuit.

[0040] In this embodiment, the voltage output circuit further includes a linear voltage regulator D2. The input terminal IN of the linear voltage regulator D2 is connected to the power input terminal VIN through a current sampling circuit. The output terminal OUT of the linear voltage regulator D2 is connected to the power output terminal VOUT. The enable terminal EN of the linear voltage regulator D2 is connected to the control signal input terminal of the voltage output circuit (connected to the reset output terminal RESET).

[0041] Further, the input terminal IN of the linear voltage regulator D2 is also grounded through a capacitor C2 for filtering.

[0042] When a load is connected to the power output V OUT the output current I OUT will flow through the resistor R1 in the current sampling circuit A, converting the current signal into a voltage signal V R1 . When the output current increases, the voltage VIN1 at the back end of R1 (VIN1 = VIN - V R1 ) will decrease. When the voltage of the power supply terminal VCC drops to a fixed voltage U REF or below, the reset output terminal RESET outputs a low level. At this time, the output of the linear voltage regulator D2 is turned off, stopping the external power supply. When the voltage of the power supply terminal VCC rises above the fixed value U REF , after a delay of about 150 - 370 mS, the reset output terminal RESET outputs a high impedance state, pulling up the voltage of the enable terminal EN of the linear voltage regulator D2 through the pull-up resistor R4, and the power supply starts to output.

[0043] The voltage drop of the resistor R1 should be between 0.3V and 2V. Too small will affect the sampling accuracy and anti-interference ability, and too large will require a very large rated power value for the resistor R1, increasing the circuit cost and occupying more printed circuit board space. Since the power supply monitoring chip D1 itself has a certain power consumption, when determining the voltage dividing resistors of the voltage monitoring circuit, the resistance values of R2 and R3 should not be too large to avoid the power consumption of D1 itself having too much influence on the voltage division ratio.

[0044] By adjusting the resistance values of the resistors R1, R2, and R3, the monitoring of different input voltages VIN and power output currents can be achieved. By adjusting the RC constant of the resistance values of the resistors R1, R2 and the capacitance value of C1, the voltage monitoring sensitivity of the voltage monitoring circuit can be adjusted.

[0045] The traditional e-Fuse chip cuts off the output after detecting an output overcurrent for about 2 ms. However, based on this circuit, by adjusting the capacitor C1, etc., it is actually measured that it will not trigger protection even after 20 ms, which can not only meet the usage requirements of the electric energy meter and terminal equipment, but also will not trigger protection by mistake. Embodiment 2

[0046] The difference between this embodiment and Embodiment 1 is that the voltage output circuit therein is replaced with the following structure:

[0047] As Figure 2 , the voltage output circuit includes a P-MOS transistor V1 and an N-MOS transistor V2.

[0048] The P-MOS transistor V1 is responsible for turning on and off the power supply. Its source is connected to the power input terminal VIN through a current sampling circuit, and its drain is connected to the power output terminal VOUT.

[0049] The N-MOS transistor V2 is connected between the control signal input terminal of the voltage output circuit and the P-MOS transistor V1, and is used to implement the conversion of control logic and control the on and off of the P-MOS transistor V1.

[0050] Specifically, the voltage output circuit further includes a resistor R5, a resistor R6, a capacitor C2, and a capacitor C3. One end of the resistor R5 is connected to the source of the P-MOS transistor V1, and the other end is connected to the drain of the N-MOS transistor V2 through the resistor R6. The other end of the resistor R5 is also connected to the gate of the P-MOS transistor V1. The source of the N-MOS transistor V2 is grounded, and its gate is connected to the control signal input terminal of the voltage output circuit. The capacitor C2 is connected in parallel with the resistor R5. The drain of the P-MOS transistor V1 is also grounded through the capacitor C3. The resistor R5, the resistor R6, and the capacitor C2 form a soft-start circuit to prevent the back-end load from having too large an instantaneous impact on the power supply.

[0051] When the reset output terminal RESET outputs a low level, the gate of the P-MOS transistor V1 is pulled high by the resistor R5, the P-MOS transistor V1 is turned off, and the power output is turned off. When the reset output terminal RESET outputs a high impedance state, the gate of the P-MOS transistor V1 is pulled low, the P-MOS transistor V1 is turned on, and the power output is turned on.

[0052] It should be noted that for those skilled in the art, it is obvious that the present utility model is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of the present utility model, the present utility model can be implemented in other specific forms. The scope of the present utility model is defined by the claims rather than the above description.

Claims

1. A power output short - circuit and over - current protection circuit applicable to an electric energy meter and a terminal device, including a power input terminal VIN and a power output terminal VOUT, characterized in that: It also includes a current sampling circuit, a voltage monitoring circuit, and a voltage output circuit; The current sampling circuit and the voltage output circuit are serially arranged between the power input terminal VIN and the power output terminal VOUT; The current sampling circuit is used to convert the current signal between the power input terminal VIN and the power output terminal VOUT into a voltage signal and output it from the voltage signal output terminal; The voltage monitoring circuit includes a resistor R2, a resistor R3, a resistor R4, a capacitor C1, and a power supply monitoring chip D1; the resistor R2 and the resistor R3 are serially connected between the voltage signal output terminal of the current sampling circuit and the ground terminal to form a voltage dividing circuit, and both ends of the resistor R3 are respectively connected to the power supply terminal VCC and the ground terminal GND of the power supply monitoring chip D1, and the capacitor C1 is connected in parallel with the resistor R3; one end of the resistor R4 is connected to the power supply terminal VCC of the power supply monitoring chip D1, and the other end is connected to the reset output terminal RESET of the power supply monitoring chip D1; the reset output terminal RESET of the power supply monitoring chip D1 is the control signal output terminal of the voltage monitoring circuit; The control signal input terminal of the voltage output circuit is connected to the control signal output terminal of the voltage monitoring circuit, and is used to control the on / off of the circuit between the power input terminal VIN and the power output terminal VOUT according to the control signal output by the voltage monitoring circuit.

2. The power output short - circuit and over - current protection circuit applicable to an electric energy meter and a terminal device according to claim 1, characterized in that: The current sampling circuit includes a resistor R1, one end of the resistor R1 is connected to the power input terminal VIN, and the other end is connected to the power output terminal VOUT through the voltage output circuit; the other end of the R1 is the voltage signal output terminal of the current sampling circuit.

3. The power output short - circuit and over - current protection circuit applicable to an electric energy meter and a terminal device according to claim 1 or 2, characterized in that: The voltage output circuit further includes a linear voltage regulator D2, the input terminal IN of the linear voltage regulator D2 is connected to the power input terminal VIN through the current sampling circuit, the output terminal OUT of the linear voltage regulator D2 is connected to the power output terminal VOUT, and the enable terminal EN of the linear voltage regulator D2 is connected to the control signal input terminal of the voltage output circuit.

4. The power output short-circuit and over-current protection circuit applicable to the electric energy meter and the terminal device according to claim 3, wherein: The input terminal IN of the linear voltage regulator D2 is also grounded through a capacitor C2.

5. The power output short-circuit and over-current protection circuit applicable to an electric energy meter and a terminal device according to claim 1 or 2, characterized in that: The voltage output circuit further includes a P-MOS transistor V1 and an N-MOS transistor V2; The source electrode of the P-MOS transistor V1 is connected to the power input terminal VIN through the current sampling circuit, and the drain electrode is connected to the power output terminal VOUT; The N-MOS transistor V2 is connected between the control signal input terminal of the voltage output circuit and the P-MOS transistor V1, and is used to realize the conversion of the control logic and control the on / off of the P-MOS transistor V1.

6. The power output short-circuit and over-current protection circuit applicable to an electricity meter and a terminal device as claimed in claim 5, characterized in that: The voltage output circuit further includes a resistor R5, a resistor R6, a capacitor C2, and a capacitor C3; One end of the resistor R5 is connected to the source electrode of the P-MOS transistor V1, and the other end is connected to the drain electrode of the N-MOS transistor V2 through the resistor R6; the other end of the resistor R5 is also connected to the gate electrode of the P-MOS transistor V1; the source electrode of the N-MOS transistor V2 is grounded, and the gate electrode is connected to the control signal input terminal of the voltage output circuit; the capacitor C2 is connected in parallel with the resistor R5; The drain electrode of the P-MOS transistor V1 is also grounded through a capacitor C3.

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