Direct-current soft start circuit

Abstract

The utility model discloses a DC soft start circuit, comprising a power supply input end positive electrode IN +, a power supply input end negative electrode IN-, a relay K100, a thermistor RT100, a current limiting resistor R100, a light emitting diode D100, a load power supply end positive electrode OUT + and a load power supply end negative electrode OUT-, the power supply input end positive electrode IN + is connected with a normally open contact NO of the relay K100, a common end COM and the thermistor RT100; the other end of the thermistor RT100 is connected with a coil A end of a relay and a load power supply end positive electrode OUT +, a power input end negative electrode IN-is connected with a coil B end of a relay K100 and a load power supply end negative electrode OUT-, the load power supply end negative electrode OUT-is connected with a negative electrode of a light-emitting diode D100, a positive electrode of the light-emitting diode D100 is connected with a current-limiting resistor R100, and a negative electrode of the current-limiting resistor R100 is connected with a positive electrode of the thermistor RT100. According to the utility model, when the load is heavy, power supply protection or damage caused by overlarge starting current at the power-on moment can be avoided, the requirement on the system power supply performance can be reduced, and the cost is effectively reduced.

Description

Technical Field

[0001] This utility model relates to the field of electronic circuit technology, and in particular to a DC soft-start circuit. Background Technology

[0002] In existing technologies, excessive starting current under heavy loads can lead to power supply protection failure or damage. For example, when a motor starts, the starting current can be twice or more than the normal rated current, resulting in excessive starting current at power-on. Currently, when driving inductive loads, the common practice is to select a power supply with sufficient redundancy, choosing one with a power rating far exceeding the load's rated power. However, this approach typically increases design costs. Therefore, there is an urgent need to develop a DC soft-start circuit to solve the aforementioned technical problems.

[0003] In view of the above, this utility model is hereby proposed. Utility Model Content

[0004] The purpose of this invention is to provide a DC soft-start circuit that can prevent excessive starting current at the moment of power-on when the load is heavy, thus avoiding power supply protection or damage. It can reduce the requirements for system power supply performance, effectively reduce costs, has broad application prospects, and is conducive to promotion and application.

[0005] To achieve the above objectives, this utility model provides a DC soft-start circuit, including a positive power input terminal IN+, a negative power input terminal IN-, a relay K100, a thermistor RT100, a positive load power supply terminal OUT+, and a negative load power supply terminal OUT-. The positive power input terminal IN+ is connected to the normally open contact NO and the common terminal COM of the relay K100 and the thermistor RT100. The other end of the thermistor RT100 is connected to the coil A terminal of the relay and the positive load power supply terminal OUT+. The negative power input terminal IN- is connected to the coil B terminal of the relay K100 and the negative load power supply terminal OUT-.

[0006] Preferably, the circuit also includes a current-limiting resistor R100 and a light-emitting diode D100. The negative terminal OUT- of the load power supply is connected to the negative terminal of the light-emitting diode D100, the positive terminal of the light-emitting diode D100 is connected to the current-limiting resistor R100, and the other end of the current-limiting resistor R100 is connected to the normally closed contact NC of the relay K100. The current-limiting resistor R100 and the light-emitting diode D100 are circuit operating status indicators and are not functionally necessary.

[0007] Preferably, the thermistor RT100 is a negative temperature coefficient thermistor.

[0008] Preferably, the relay K100 is a relay that has both normally open and normally closed contacts.

[0009] The DC soft-start circuit provided by this utility model has the following beneficial effects.

[0010] When the load is heavy, this invention can avoid excessive starting current at the moment of power-on, which may cause power supply protection or damage. It can reduce the requirements for system power supply performance and effectively reduce costs. Attached Figure Description

[0011] Figure 1 A circuit diagram of a DC soft-start circuit provided by this utility model. Detailed Implementation

[0012] The present invention will be further described below with reference to specific embodiments and accompanying drawings to help understand the content of the present invention.

[0013] like Figure 1 The diagram shown is a circuit diagram of a DC soft-start circuit provided by this utility model. This DC soft-start circuit includes a positive power input terminal IN+, a negative power input terminal IN-, a relay K100, a thermistor RT100, a positive load power supply terminal OUT+, and a negative load power supply terminal OUT-. The positive power input terminal IN+ is connected to the normally open contact NO of the relay K100, the common terminal COM, and the thermistor RT100. The other end of the thermistor RT100 is connected to the coil A terminal of the relay and the positive load power supply terminal OUT+. The negative power input terminal IN- is connected to the coil B terminal of the relay K100 and the negative load power supply terminal OUT-.

[0014] The DC soft-start circuit also includes a current-limiting resistor R100 and a light-emitting diode (LED) D100. The negative terminal OUT- of the load power supply is connected to the negative terminal of the LED D100, and the positive terminal of the LED D100 is connected to the current-limiting resistor R100. The other end of the current-limiting resistor R100 is connected to the normally closed contact NC of the relay K100. The current-limiting resistor R100 and the LED D100 are circuit operating status indicators and are not functionally necessary. The thermistor RT100 is a negative temperature coefficient thermistor. The relay K100 is a relay with both normally open and normally closed contacts.

[0015] The working principle of this utility model is as follows:

[0016] After the system is initially powered on, the thermistor limits the current to the load. Because the initial resistance of the thermistor RT100 is relatively large, the voltage drop across it is large, while the voltage drop across the relay coil is small. The relay is in the open state, and the relay common terminal COM and normally closed contact NC are short-circuited. Current flows through the power input terminal IN+ into the common terminal COM, normally closed contact NC, current-limiting resistor R100, and LED D100, returning to the power input terminal IN-. LED D100 lights up, indicating that the circuit is in the process of soft-starting. As the circuit operates, the temperature of the thermistor RT100 increases, its resistance decreases, the voltage drop across the relay coil and load increases, the relay activates, the LED turns off, the circuit completes the soft-start, and the load operates normally.

[0017] When the load is heavy, this invention can avoid excessive starting current at the moment of power-on, which may cause power supply protection or damage. It can reduce the requirements for system power supply performance and effectively reduce costs.

[0018] This article uses specific examples to illustrate the inventive concept in detail. The description of the above embodiments is only for the purpose of helping to understand the core idea of ​​this utility model. It should be noted that any obvious modifications, equivalent substitutions or other improvements made by those skilled in the art without departing from the inventive concept should be included within the protection scope of this utility model.

Claims

1. A DC soft-start circuit, characterized in that, It includes a power input terminal positive IN+, a power input terminal negative IN-, a relay K100, a thermistor RT100, a load power supply terminal positive OUT+, and a load power supply terminal negative OUT-. The power input terminal positive IN+ is connected to the normally open contact NO of the relay K100, the common terminal COM, and the thermistor RT100. The other end of the thermistor RT100 is connected to the coil A terminal of the relay and the load power supply terminal positive OUT+. The power input terminal negative IN- is connected to the coil B terminal of the relay K100 and the load power supply terminal negative OUT-.

2. The DC soft-start circuit according to claim 1, characterized in that, It also includes a current-limiting resistor R100 and a light-emitting diode D100. The negative terminal OUT- of the load power supply is connected to the negative terminal of the light-emitting diode D100, the positive terminal of the light-emitting diode D100 is connected to the current-limiting resistor R100, and the other end of the current-limiting resistor R100 is connected to the normally closed contact NC of the relay K100. The current-limiting resistor R100 and the light-emitting diode D100 are circuit operating status indication circuits.

3. The DC soft-start circuit according to claim 2, characterized in that, The thermistor RT100 is a negative temperature coefficient thermistor.

4. The DC soft-start circuit according to claim 3, characterized in that, The relay K100 is a relay that has both normally open and normally closed contacts.

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