Slow start circuit

Abstract

The utility model relates to a slow start circuit, comprising an input voltage which is respectively connected with a first capacitor, a first electrolytic capacitor and a load working circuit; the other end of the first capacitor is connected with the first resistor; the other end of the first resistor is connected with the second resistor and the base electrode of the triode. The other end of the first electrolytic capacitor, the other end of the second resistor and the collector electrode of the triode are grounded. The emitter of the triode is respectively connected with the third resistor and the EN pin of the circuit control unit; a VCC pin, an SW pin, an ISEN pin and the other end of the third resistor of the circuit control unit are connected with the load working circuit; and a GND pin of the circuit control unit is grounded. According to the utility model, abnormal phenomena of overload, overcurrent and the like of a power supply system are effectively prevented.

Description

Technical Field

[0001] This utility model relates to a soft-start circuit. Background Technology

[0002] When a circuit is powered on, the power supply voltage is instantaneously applied to the load. For some capacitive loads (such as large-capacity electrolytic capacitors) or inductive loads (such as motors and transformers), a large inrush current will be generated. For example, in a power supply circuit containing a large-capacity filter capacitor, when the power is first turned on, the capacitor is equivalent to a short circuit, and the instantaneous current will be very large. This may cause fuses in the circuit to blow, electronic components to be damaged, such as rectifier diodes burning out due to overcurrent, or cause a large drop in the output voltage of the power supply, affecting the normal operation of other equipment.

[0003] Therefore, a soft-start circuit is provided. Utility Model Content

[0004] The purpose of this invention is to overcome the existing defects and provide a soft-start circuit that effectively prevents abnormal phenomena such as overload and overcurrent in the power supply system.

[0005] The technical solution to achieve the above objectives is:

[0006] A soft-start circuit includes: an input voltage,

[0007] The input voltage is connected to the first capacitor, the first electrolytic capacitor, and the load working circuit, respectively.

[0008] The other end of the first capacitor is connected to the first resistor;

[0009] The other end of the first resistor is connected to the second resistor and the base of the transistor, respectively;

[0010] The other ends of the first electrolytic capacitor, the second resistor, and the collector of the transistor are all grounded;

[0011] The emitter of the transistor is connected to the third resistor and the EN pin of the circuit control unit, respectively.

[0012] The VCC pin, SW pin, ISEN pin, and the other end of the third resistor of the circuit control unit are all connected to the load operating circuit.

[0013] The GND pin of the circuit control unit is grounded.

[0014] Preferably, the load operating circuit includes: a second capacitor, a fourth resistor, a diode, an inductor, and a fifth resistor.

[0015] The VCC pin of the circuit control unit is connected to the second capacitor and the fourth resistor respectively, the SW pin is connected to the anode of the diode and the inductor respectively, and the ISEN pin is connected to the fifth resistor.

[0016] The other ends of the second capacitor and the fifth resistor are both grounded;

[0017] The input voltage, the other end of the third resistor, the fourth resistor, and the cathode of the diode are connected to the positive terminal of the light-emitting diode;

[0018] The other end of the inductor is connected to the negative terminal of the light-emitting diode;

[0019] A second electrolytic capacitor is connected in parallel across the positive and negative terminals of the light-emitting diode.

[0020] The beneficial effects of this utility model are as follows: During the input voltage change from 0 to Vin, the first capacitor is charged. The current then flows through the first resistor to the transistor, causing current to flow through the transistor's base, thus connecting the emitter and collector. This conduction is achieved through the EN pin of the circuit control unit, pulling the transistor's potential down to ground, putting the load control circuit in standby mode with no load operation. When the voltage reaches a stable value Vin, the charging process of the first capacitor ends, the potentials at both ends are balanced, and no more current flows. The transistor then turns off, and the voltage at the EN pin of the circuit control unit decreases. A third resistor pulls the EN pin up to Vin, putting it at a high potential. At this time, the circuit control unit switches the load operating circuit from standby to load operating state. This process effectively disconnects the load before the input power supply voltage stabilizes by changing the input potential during startup, effectively avoiding abnormal problems such as overload and overcurrent at the moment of power-on, and providing product stability. At the same time, the soft-start time can be appropriately adjusted according to the capacitance value of the first capacitor to suit different product circuits. This circuit is simple, low-cost, and widely applicable, and can be used in most soft-start circuits. Attached Figure Description

[0021] Figure 1 This is a circuit diagram of a soft-start circuit according to this utility model. Detailed Implementation

[0022] The technical solution of this utility model will now be clearly and completely described in conjunction with the accompanying drawings. In the description of this utility model, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing this utility model and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0023] The present invention will be further described below with reference to the accompanying drawings.

[0024] like Figure 1 As shown, a soft-start circuit includes: an input voltage Vin, which is connected to a first capacitor C1, a first electrolytic capacitor EC1, and a load operating circuit; the other end of the first capacitor C1 is connected to a first resistor R1; the other end of the first resistor R1 is connected to a second resistor R2 and the base of a transistor Q1; the other ends of the first electrolytic capacitor EC1, the second resistor R2, and the collector of the transistor Q1 are all grounded; the emitter of the transistor Q1 is connected to a third resistor R3 and the EN pin of a circuit control unit U1; the VCC pin, SW pin, ISEN pin of the circuit control unit U1, and the other end of the third resistor R3 are all connected to the load operating circuit; the GND pin of the circuit control unit U1 is grounded.

[0025] In this embodiment, the load operating circuit includes: a second capacitor C2, a fourth resistor R4, a diode D1, an inductor L1, and a fifth resistor R5. The VCC pin of the circuit control unit U1 is connected to the second capacitor C2 and the fourth resistor R4, the SW pin is connected to the anode of the diode D1 and the inductor L1, and the ISEN pin is connected to the fifth resistor R5. The other ends of the second capacitor C2 and the fifth resistor R5 are grounded. The input voltage Vin, the other ends of the third resistor R3 and the fourth resistor R4, and the cathode of the diode D1 are connected to the positive terminal of the light-emitting diode LED. The other end of the inductor L1 is connected to the negative terminal of the light-emitting diode LED. The positive and negative terminals of the light-emitting diode LED are connected in parallel with the second electrolytic capacitor EC2.

[0026] Working principle:

[0027] As the input voltage changes from 0 to Vin, the first capacitor C1 is charged. The current then flows through the first resistor R1 to the transistor Q1, causing current to flow through the base of transistor Q1. This conducts between the emitter and collector of transistor Q1. Through the EN pin of the circuit control unit U1, the potential of the capacitor C1 is pulled low to ground by transistor Q1, putting the control load circuit in standby mode with no load operation. When the voltage reaches the stable value Vin, the charging process of the first capacitor C1 ends, the potentials at both ends are balanced, and no current is formed. Transistor Q1 is also turned off. The potential of the EN pin of the circuit control unit U1 is then pulled up to Vin by the third resistor R3, putting the EN pin at a high potential. At this time, the circuit control unit U1 controls the load circuit to switch from standby mode to load operation mode, thus completing the circuit's soft start process.

[0028] The above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although the utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this utility model.

Claims

1. A soft start circuit, characterized by It includes: Input voltage (Vin), The input voltage (Vin) is connected to the first capacitor (C1), the first electrolytic capacitor (EC1) and the load working circuit respectively; The other end of the first capacitor (C1) is connected to the first resistor (R1); The other end of the first resistor (R1) is connected to the base of the second resistor (R2) and the transistor (Q1) respectively; The other end of the first electrolytic capacitor (EC1), the second resistor (R2) and the collector of the transistor (Q1) are grounded; The emitter of the transistor (Q1) is connected to the third resistor (R3) and the EN pin of the circuit control unit (U1) respectively; The VCC pin, SW pin, ISEN pin of the circuit control unit (U1) and the other end of the third resistor (R3) are connected to the load working circuit; The GND pin of the circuit control unit (U1) is grounded.

2. A soft start circuit according to claim 1, wherein The load working circuit includes: second capacitor (C2), fourth resistor (R4), diode (D1), inductor (L1) and fifth resistor (R5), The VCC pin of the circuit control unit (U1) is connected to the second capacitor (C2) and the fourth resistor (R4) respectively, the SW pin is connected to the anode of the diode (D1) and the inductor (L1) respectively, and the ISEN pin is connected to the fifth resistor (R5); The other end of the second capacitor (C2) and the fifth resistor (R5) is grounded; The input voltage (Vin), the other end of the third resistor (R3), the fourth resistor (R4) and the cathode of the diode (D1) are connected to the positive electrode of the light emitting diode (LED); The other end of the inductor (L1) is connected to the negative electrode of the light emitting diode (LED); The positive and negative electrodes of the light emitting diode (LED) are connected in parallel with the second electrolytic capacitor (EC2).

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