A direct current input circuit with anti-reverse connection, slow start and switch controlled functions

Abstract

The utility model provides a kind of DC input circuit with anti-reverse connection, slow start, switch controlled function, the circuit of this design uses low-power electronic device, the impact current caused by the input end parallel large capacity capacitor when power supply starts is solved, simultaneously has anti-input reverse connection function, this circuit utilizes MOS tube gate-source different ground, simplifies the gate drive mode of MOS tube, saves product space and cost, it includes two VI N+ signal interface and two VI N- signal signal interface, the VI N+ signal interface on left side is connected with first diode V1, the VI N+ signal interface on right side and VI N- signal signal interface are connected with same capacitor C1, the other end of the first diode V1 is connected with first resistance R1, the first resistance R1 is connected with photo-coupler triode O1, the photo-coupler triode O1 is connected with first voltage discharge resistance R2.

Description

Technical Field

[0001] This utility model relates to the field of DC input circuit technology, and in particular to a DC input circuit with reverse connection protection, soft start, and switch control functions. Background Technology

[0002] When designing a DC power supply input circuit, a large-capacity electrolytic capacitor needs to be connected in parallel in the input circuit to maintain the stability of the input voltage. A soft-start circuit also needs to be designed to limit the inrush current generated by the charging of the electrolytic capacitor at power-on.

[0003] Because it uses DC power input, reverse polarity can easily damage internal components. Therefore, a reverse polarity protection function is required. This protects the input electrolytic capacitors from reverse voltage breakdown and also protects downstream components from damage.

[0004] When a DC power supply is input, it needs to have a switch control function to enable the power-on or power-off function of the electrical equipment.

[0005] Typically, a relay (or contactor) and a starting resistor connected in series with the relay are used to switch the power supply and enable soft start; a diode is connected in parallel at the input to provide reverse connection protection for DC input. However, because the mechanical contacts of a relay have weak resistance to inrush current, they are prone to sticking together under certain operating conditions. If a reverse connection protection diode is connected in parallel at the input, it will suffer severe losses and be easily damaged under long-term reverse connection conditions. This design easily leads to component damage and poor circuit reliability. Utility Model Content

[0006] To address the shortcomings of existing technologies, this invention solves the following technical problem: Due to the weak resistance of relay mechanical contacts to surge current, relay contacts are prone to sticking under certain operating conditions. If a reverse connection protection diode is connected in parallel at the input terminal, the diode suffers severe losses and is easily damaged under long-term reverse connection conditions. The above design easily leads to device damage and poor circuit reliability. This invention provides a DC input circuit with reverse connection protection, soft start, and controlled switching functions.

[0007] To achieve the above objectives, this utility model provides: A DC input circuit with reverse connection protection, soft start, and switch control functions includes two VIN+ signal interfaces and two VIN- signal interfaces. A first diode V1 is connected to the VIN+ signal interface on the left. The VIN+ signal interface and the VIN- signal interface on the right are connected to the same capacitor C1. The other end of the first diode V1 is connected to a first resistor R1. An optocoupler transistor O1 is connected to the first resistor R1. A first voltage bleed resistor R2 is connected to the optocoupler transistor O1. A second diode V2 is connected to the first voltage bleed resistor R2. A soft start resistor R3 is connected to the second diode V2. A second voltage bleed resistor R4 is connected to the soft start resistor R3. A second resistor R5 is connected to the second voltage bleed resistor R4. The second resistor R5 is connected to the VIN+ signal interface on the right.

[0008] Preferably, a first NMOS switch V3 and a second NMOS switch V4 are connected in series on the two VIN- signal interfaces, and the first NMOS switch V3, the second NMOS switch V4, the second diode V2, and the soft-start resistor R3 are connected in parallel.

[0009] Preferably, the second diode V2 and the soft-start resistor R3 are connected in series between the two VIN- signal interfaces.

[0010] Preferably, one end of the first NMOS switch V3 is connected to the first voltage discharge resistor R2.

[0011] Preferably, one end of the second NMOS switch V4 is connected to the second voltage discharge resistor R4.

[0012] Preferably, the first voltage discharge resistor R2 is connected to the VIN- signal interface on the left side.

[0013] Preferably, the second voltage discharge resistor R4 is connected to the VIN- signal interface on the right side.

[0014] Preferably, the first NMOS switch V3 and the second NMOS switch V4 form a bidirectional switch.

[0015] Preferably, the capacitor C1 is a high-capacity capacitor.

[0016] Preferably, the first resistor R1 and the second resistor R5 provide the gate turn-on voltage for the bidirectional switch.

[0017] Preferably, the first diode V1 is connected in series in the gate conduction branch of the second NMOS switch V4 to provide reverse connection protection for this branch.

[0018] Preferably, the soft-start resistor R3 can limit the instantaneous short-circuit current, and the second diode V2 is connected in series in the branch of the soft-start resistor R3 to perform the reverse connection protection function of this branch.

[0019] Preferably, the optocoupler transistor O1 plays the role of controlling the turn-on and turn-off of the second NMOS switch transistor V4.

[0020] Compared with the prior art, the advantages of this utility model are: This utility model circuit uses low-power electronic devices, which solves the problem of inrush current caused by a large-capacity capacitor connected in parallel at the input terminal when the power supply is started. It also has a reverse connection protection function. This circuit uses different grounding points of the gate and source of the MOSFET to simplify the gate driving method of the MOSFET, saving product space and cost. Attached Figure Description

[0021] Figure 1 The circuit diagram for the bidirectional MOSFET soft-start reverse connection protection in this design is shown. Detailed Implementation

[0022] The embodiments of this utility model will be further described in detail below with reference to the accompanying drawings.

[0023] See Figure 1 As shown, a DC input circuit with reverse connection protection, soft start, and switch control functions includes a VIN+ input interface, a VIN- input interface, a VOUT+ output interface, and a VOUT- output interface. A first diode V1 is connected to the VIN+ input interface. A capacitor C1, which is a large-capacity capacitor, is connected between the VOUT+ and VOUT- output interfaces. A first resistor R1 is connected to the other end of the first diode V1. An optocoupler O1 is connected to the first resistor R1. A first voltage bleeder resistor R2 is connected to the optocoupler O1. A second diode V2 is connected to the first voltage bleeder resistor R2. A soft start resistor R3 is connected to the second diode V2. A second voltage bleeder resistor R4 is connected to the soft start resistor R3. A second resistor R5 is connected to the second voltage bleeder resistor R4. The second resistor R5 is connected to the VOUT+ output interface.

[0024] In this embodiment, a first NMOS switch V3 and a second NMOS switch V4 are connected in series between the VIN input interface and the VOUT output interface. The first NMOS switch V3, the second NMOS switch V4, the second diode V2, and the soft-start resistor R3 are connected in parallel.

[0025] In this embodiment, the second diode V2 and the soft-start resistor R3 are connected in series between the VIN input interface and the VOUT output interface.

[0026] In this embodiment, the gate of the first NMOS switch V3 is connected to the first voltage discharge resistor R2, and the gate of the second NMOS switch V4 is connected to the second voltage discharge resistor R4.

[0027] In this embodiment, the first voltage bleed resistor R2 is connected to the VIN input interface, and the second voltage bleed resistor R4 is connected to the VOUT output interface.

[0028] In this embodiment, the first NMOS switch V3 and the second NMOS switch V4 form a bidirectional switch.

[0029] In this embodiment, the first resistor R1 and the second resistor R5 provide the gate turn-on voltage for the bidirectional switch.

[0030] In this embodiment, the first diode V1 is connected in series in the gate conduction branch of the second NMOS switch V4, which serves as the reverse connection protection function for this branch.

[0031] In this embodiment, the soft-start resistor R3 can limit the instantaneous short-circuit current, and the second diode V2 is connected in series in the branch of the soft-start resistor R3 to provide reverse connection protection for this branch.

[0032] In this embodiment, the optocoupler transistor O1 plays the role of controlling the turn-on and turn-off of the second NMOS switch V4.

[0033] Work style: 1. When inputs VIN+ and VIN- are positively connected, capacitor C1 is slowly charged through the soft-start resistor R3 and the second diode V2 at a preset current. During this process, the optocoupler transistor O1 provides the turn-on voltage to the first NMOS switch V3. The second NMOS switch V4 is turned on by the voltage provided by the second resistor R5 during the charging of capacitor C1. When capacitor C1 is fully charged, the internal transistor of optocoupler O1 is turned on, and the gate turn-on voltage of the first NMOS switch V3 is provided through the first diode V1, the first resistor R1, and the optocoupler transistor O1, turning on the first NMOS switch V3. At this time, the first NMOS switch V3 and the second NMOS switch V4 are connected in parallel with the soft-start resistor R3 and the second diode V2 with a very small on-resistance, and the current of the soft-start resistor R3 is negligible.

[0034] 2. When the inputs VIN+ and VIN- are reversed, the following branches exist: First voltage bleeder resistor R2 → optocoupler O1 → First resistor R1 → First diode V1; Branch: First NMOS switch V3 → Second NMOS switch V4 → Capacitor C1. Because the input signal is reversed, the second NMOS switch V4 has no turn-on condition, and it also has an internal reverse diode. Each of the above current loops has a reverse diode (first diode V1, second NMOS switch V4), therefore there is no current path when the input is reversed, and it will not cause circuit damage.

[0035] This utility model is not limited to the above-described preferred embodiment. Anyone can derive other forms of products under the guidance of this utility model. However, regardless of any changes made in its shape or structure, any technical solution that is the same as or similar to this utility model is within its protection scope.

Claims

1. A DC input circuit with reverse connection protection, soft start, and switch control functions, comprising a VIN+ input interface, a VIN- input interface, a VOUT+ output interface, and a VOUT- output interface, characterized in that: A first diode V1 is connected to the VIN+ input interface. A capacitor C1 is connected between the VOUT+ output interface and the VOUT- output interface. A first resistor R1 is connected to the other end of the first diode V1. An optocoupler O1 is connected to the first resistor R1. A first voltage bleed resistor R2 is connected to the optocoupler O1. A second diode V2 is connected to the first voltage bleed resistor R2. A soft-start resistor R3 is connected to the second diode V2. A second voltage bleed resistor R4 is connected to the soft-start resistor R3. A second resistor R5 is connected to the second voltage bleed resistor R4. The second resistor R5 is connected to the VOUT+ output interface.

2. The DC input circuit with reverse connection protection, soft start, and switch control functions according to claim 1, characterized in that: A first NMOS switch V3 and a second NMOS switch V4 are connected in series between the VIN input interface and the VOUT output interface. The first NMOS switch V3, the second NMOS switch V4, the second diode V2, and the soft-start resistor R3 are connected in parallel.

3. The DC input circuit with reverse connection protection, soft start, and switch control functions according to claim 1, characterized in that: The second diode V2 and the soft-start resistor R3 are connected in series between the VIN input interface and the VOUT output interface.

4. A DC input circuit with reverse connection protection, soft start, and switch control functions according to claim 2, characterized in that: The gate of the first NMOS switch V3 is connected to the first voltage discharge resistor R2.

5. A DC input circuit with reverse connection protection, soft start, and switch control functions according to claim 2, characterized in that: The gate of the second NMOS switch V4 is connected to the second voltage discharge resistor R4.

6. A DC input circuit with reverse connection protection, soft start, and switch control functions according to claim 1, characterized in that: The first voltage discharge resistor R2 is connected to the VIN input interface.

7. A DC input circuit with reverse connection protection, soft start, and switch control functions according to claim 1, characterized in that: The second voltage discharge resistor R4 is connected to the VOUT output interface.

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