Step-down isolation protection circuit

Abstract

The utility model relates to the technical field of power supplies, in particular to a step-down isolation protection circuit, which comprises an input protection circuit, a primary step-down circuit, an isolation circuit and a secondary step-down circuit which are electrically connected in sequence, the input end of the input protection circuit is used for being connected with an input voltage module, the output end of the secondary step-down circuit is used for being connected with a load power supply end, and the input protection circuit comprises an overcurrent and overvoltage protection circuit, an anti-backflow circuit and a slow start circuit which are electrically connected in sequence. And the output end of the slow start circuit is connected with the input end of the primary step-down circuit. According to the utility model, step-down isolation and multiple protection can be realized.

Description

TECHNICAL FIELD

[0001] The utility model relates to power supply technical field, concretely relates to a step-down isolation protection circuit. BACKGROUND

[0002] With the rapid popularization of new energy vehicles, the safety and reliability of charging piles as core energy supply equipment are concerned. In the charging pile system, the MCU (micro control unit) circuit board as the control core needs a continuous and stable low-voltage power supply to ensure the normal operation of charging control, communication, state monitoring and other functions. At present, some charging piles use external batteries to supply power to the MCU, and convert the high-voltage battery output into a low-voltage level suitable for the operation of the MCU through a DCDC step-down circuit. However, the following defects still exist in the prior art:

[0003] Insufficient isolation leads to interference and safety hazards: the traditional non-isolated DCDC circuit is easily affected by external battery terminal voltage fluctuation or surge impact, and high-frequency noise may be coupled to the MCU side through the common ground path, resulting in signal distortion, program runaway or even hardware damage. In addition, the design lacking electrical isolation may threaten the safety of the MCU and the operator when a short circuit or leakage occurs on the battery side.

[0004] Weak dynamic response and protection mechanism: when the battery input voltage suddenly changes, such as a high-voltage spike or under-voltage, the conventional step-down circuit lacks a fast-response protection module, making it difficult to cut off or adjust the output in time, which may cause the MCU power supply to be interrupted or damaged by overvoltage. Although some solutions add overvoltage protection devices such as TVS tubes, the single protection component has the problems of long action delay and limited tolerance.

[0005] Therefore, there is an urgent need for a step-down protection circuit scheme with high-efficiency isolation, wide voltage adaptation and high reliability to improve the safety and environmental adaptability of the new energy charging pile MCU power supply system. UTILITY MODEL CONTENTS

[0006] The utility model aims to provide a step-down isolation protection circuit, which realizes step-down isolation and multiple protection.

[0007] To achieve the above-mentioned purpose, the utility model provides the following technical scheme:

[0008] The utility model provides a step-down isolation protection circuit, which comprises input protection circuit, primary step-down circuit, isolation circuit and secondary step-down circuit connected in sequence, the input end of input protection circuit is used for accessing input voltage module, the output end of secondary step-down circuit is used for connecting load power supply end, input protection circuit includes overcurrent overvoltage protection circuit, anti-backflow circuit and slow start circuit connected in sequence, the output end of slow start circuit is connected with the input end of primary step-down circuit.

[0009] In combination with the first aspect, optionally, the overcurrent and overvoltage protection circuit comprises a fuse F1 and a TVS diode array, an input end of the fuse F1 is connected with a positive pole end of the input voltage module, an output end of the fuse F1 is connected with an input / output pin end of the TVS diode array, and a ground pin end of the TVS diode array is connected with a negative pole end of the input voltage module.

[0010] In combination with the first aspect, optionally, the anti-backflow circuit comprises a MOS tube Q1, a drain of the MOS tube Q1 is connected with the output end of the fuse F1, a resistor R1 is connected in series between a gate and a source of the MOS tube Q1, and the gate of the MOS tube Q1 is connected with the negative pole end of the input voltage module in sequence through a resistor R3 and a resistor R5.

[0011] In combination with the first aspect, optionally, the slow start circuit comprises a MOS tube Q2, a resistor R2 is connected in series between a source and a gate of the MOS tube Q2, and a capacitor C1 is connected in parallel across the resistor R2, the source of the MOS tube Q2 is connected with the source of the MOS tube Q1, and the gate of the MOS tube Q2 is connected with the negative pole end of the input voltage module in sequence through a resistor R4 and a resistor R6; a drain of the MOS tube Q2 is a positive pole input end of the input protection circuit, and a connection end of the resistor R6 and the input voltage module is a negative pole input end of the input protection circuit.

[0012] In combination with the first aspect, optionally, the primary voltage reduction circuit is a DCDC voltage reduction circuit.

[0013] In combination with the first aspect, optionally, the isolation circuit is an isolation power module.

[0014] In combination with the first aspect, optionally, the secondary voltage reduction circuit is an LDO voltage reduction circuit.

[0015] The utility model discloses the beneficial effect is:

[0016] 1) adopt hierarchical voltage reduction, increase the isolation circuit between the primary voltage reduction circuit and the secondary voltage reduction circuit, build the perfect electrical isolation barrier, effectively block the high-frequency noise, surge interference of input side through the common ground path coupling to MCU power supply end, this design not only avoids signal distortion and program exception, also significantly improves the safety of system under the battery short circuit or leakage working condition, ensures the safety of operating personnel and equipment, designs the input protection circuit before the primary voltage reduction circuit, and the input protection circuit comprises the overcurrent and overvoltage protection circuit, the anti-backflow circuit and the slow start circuit that are electrically connected in sequence, provides multiple protection.

[0017] 2) The input protection circuit adopts a three-stage series architecture of "overcurrent and overvoltage - anti-backflow - slow start"; a TVS diode array and a fuse F1 constitute a fast response unit, which can clamp high voltage peaks and trigger the fuse protection within microseconds; the anti-backflow circuit built by the MOS tube Q1 accurately controls the conduction threshold through a gate resistor network, completely blocking the impact of reverse current on the front-end battery; the slow start circuit realizes the progressive charging of the input capacitor through the RC delay network and the synergistic effect of the MOS tube Q2, eliminating the stress damage of inrush current on power devices. BRIEF DESCRIPTION OF DRAWINGS

[0018] The accompanying drawings are included to provide a further understanding of the present application, and constitute a part of the specification, illustrate the present application and explain the technical scheme of the present application, and do not constitute a limitation on the present application. In the drawings:

[0019] Figure 1 is a module schematic diagram of the present application;

[0020] Figure 2 is an input protection circuit diagram of the present application;

[0021] Figure 3 is a first-stage voltage reduction circuit diagram of the present application;

[0022] Figure 4 is an isolation circuit diagram of the present application;

[0023] Figure 5 is a second-stage voltage reduction circuit diagram of the present application. DETAILED DESCRIPTION

[0024] The technical scheme of the present application will be described in detail below by means of the drawings and specific embodiments, and it should be understood that the specific features in the embodiments and the specific embodiments are detailed descriptions of the technical scheme of the present application, and not a limitation on the technical scheme of the present application.

[0025] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "illustrative embodiment", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics can be combined in any one or more embodiments or examples in a suitable manner.

[0026] As Figure 1The utility model provides a kind of step-down isolation protection circuit, including input protection circuit, primary step-down circuit, isolation circuit, secondary step-down circuit connected in turn electrically;The input end of input protection circuit is used to access input voltage module, the output end of secondary step-down circuit is used to connect load power supply end, input protection circuit includes overcurrent overvoltage protection circuit, anti-backflow circuit and slow start circuit connected in turn electrically, the output end of slow start circuit is connected with the input end of primary step-down circuit.

[0027] In some embodiments, as Figure 2 Shown, overcurrent overvoltage protection circuit includes fuse F1 and TVS diode array, the input end of fuse F1 is connected with the anode end of input voltage module, the output end of fuse F1 is connected with the input / output pin end of TVS diode array, the ground pin end of TVS diode array is connected with the cathode end of input voltage module;In an embodiment, the model of TVS diode array is NUP1301,215.

[0028] In some embodiments, as Figure 2 Shown, anti-backflow circuit includes MOS tube Q1, the drain of MOS tube Q1 is connected with the output end of fuse F1, resistance R1 is connected between the gate and source of MOS tube Q1, the gate of MOS tube Q1 is connected with the cathode end of input voltage module after resistance R3 and resistance R5 are connected in series in turn.

[0029] In some embodiments, as Figure 2 Shown, slow start circuit includes MOS tube Q2, resistance R2 is connected between the source and gate of MOS tube Q2, capacitor C1 is connected in parallel at the two ends of resistance R2, the source of MOS tube Q2 is connected with the source of MOS tube Q1, the gate of MOS tube Q2 is connected with the cathode end of input voltage module after resistance R4 and resistance R6 are connected in series in turn;The drain of MOS tube Q2 is the anode input end of input protection circuit, and the connection end of resistance R6 and input voltage module is the cathode input end of input protection circuit.

[0030] In some embodiments, as Figure 3 Shown, primary step-down circuit is DCDC step-down circuit, can adopt known DCDC step-down circuit, the utility model does not make too much limit here;In a specific example, the model of selected DCDC power chip is SCT2A10STER.

[0031] In some embodiments, as Figure 4 Shown, isolation circuit is isolation power module, and isolation power module can be selected according to actual needs, and does not make too much limit here;In a specific example, the model of isolation power module is B0505LS-1WR3L.

[0032] In some embodiments, asFigure 5 As shown, the secondary voltage reduction circuit is an LDO voltage reduction circuit, wherein the LDO voltage reduction circuit can adopt a known LDO voltage reduction circuit, and the utility model does not limit too much herein; in one specific example, the linear voltage regulator model is ME6211C33M5G-N.

[0033] The above only describes the preferred embodiments of the utility model and is not used to limit the utility model, although the utility model is described in detail with reference to the foregoing embodiments, for the person skilled in the art, still can modify the technical scheme recorded in the foregoing each embodiment, or equivalent replacement is carried out to part technical features. Any modification, equivalent replacement, improvement etc. that is made within the spirit and principle of the utility model should be included in the protection scope of the utility model.

Claims

1. A step-down isolation protection circuit, characterized in that, It includes an input protection circuit, a first-stage step-down circuit, an isolation circuit, and a second-stage step-down circuit, which are connected in sequence. The input terminal of the input protection circuit is used to connect to the input voltage module, and the output terminal of the second-stage step-down circuit is used to connect to the load power supply terminal. The input protection circuit includes an overcurrent and overvoltage protection circuit, an anti-backflow circuit, and a soft-start circuit, which are connected in sequence. The output terminal of the soft-start circuit is connected to the input terminal of the first-stage step-down circuit.

2. The step-down isolation protection circuit according to claim 1, characterized in that: The overcurrent and overvoltage protection circuit includes a fuse F1 and a TVS diode array. The input terminal of the fuse F1 is connected to the positive terminal of the input voltage module, the output terminal of the fuse F1 is connected to the input / output pin of the TVS diode array, and the ground pin of the TVS diode array is connected to the negative terminal of the input voltage module.

3. The step-down isolation protection circuit according to claim 2, characterized in that: The backflow prevention circuit includes a MOSFET Q1, the drain of which is connected to the output terminal of the fuse F1, a resistor R1 connected in series between the gate and source of the MOSFET Q1, and the gate of the MOSFET Q1 connected in series with resistors R3 and R5 and then connected to the negative terminal of the input voltage module.

4. The step-down isolation protection circuit according to claim 3, characterized in that: The soft-start circuit includes a MOSFET Q2, with a resistor R2 connected in series between the source and gate of the MOSFET Q2. A capacitor C1 is connected in parallel across the resistor R2. The source of the MOSFET Q2 is connected to the source of the MOSFET Q1. The gate of the MOSFET Q2 is connected in series with resistors R4 and R6 and then connected to the negative terminal of the input voltage module. The drain of the MOSFET Q2 is the positive input terminal of the input protection circuit, and the connection point of the resistor R6 with the input voltage module is the negative input terminal of the input protection circuit.

5. The step-down isolation protection circuit according to claim 1, characterized in that: The first-stage step-down circuit is a DC-DC step-down circuit.

6. The step-down isolation protection circuit according to claim 1, characterized in that: The isolation circuit is an isolated power supply module.

7. The step-down isolation protection circuit according to claim 1, characterized in that: The secondary step-down circuit is an LDO step-down circuit.

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