Pre-charging control circuit for switching power supply

Abstract

The utility model discloses a pre-charging control circuit for a switching power supply, which comprises a power supply module (15), a relay (16), a pre-charging module (11), a voltage dividing module (12), an energy storage module (13) and a switching module (14), external input is connected with the input end of the pre-charging module (11) and one end of the relay (16), the output end of the pre-charging module (11) is connected with the input end of the energy storage module (13) and the input end of the voltage dividing module (12), and the output end of the energy storage module (13) and the output end of the voltage dividing module (12) are connected in parallel and then connected with the first input end of the switch module (14). The second input end of the switch module (14) is connected with the output end of the power supply module (15), the output end of the switch module (14) is connected with the other end of the relay (16), and the output end of the relay (16) is connected with the output interface.

Description

Technical Field

[0001] This utility model relates to the field of circuit control technology, and in particular to a pre-charge control circuit for a switching power supply. Background Technology

[0002] In high-power switching power supplies, there are large-capacity filter capacitors after the mains rectifier circuit. Due to the characteristic that the voltage across the capacitor cannot change abruptly, a very large current will charge the filter capacitor when the power is turned on. If this current is not controlled, it will damage the power grid and the filter capacitor.

[0003] Existing technology uses a pre-charge control circuit to pre-charge the filter capacitor. The pre-charge circuit basically uses a resistor for pre-charging, with a relay connected in parallel across the resistor. After the pre-charge is complete, the relay closes, directly short-circuiting the resistor to reduce circuit power consumption.

[0004] Currently, conventional pre-charge control circuits either directly activate the relay via auxiliary power or activate the relay by a separate microcontroller based on estimated time. Due to varying residual voltages in the capacitors, if the relay closes too early, the pre-charge function is not achieved. If the relay closes too late, the subsequent stage has already started operating, and the operating current of the subsequent stage flows through the pre-charge resistor, posing a risk of burnout or damage to the pre-charge resistor. Utility Model Content

[0005] To address the problem of burnout and damage to pre-charging resistors caused by unstable relay closing time in existing technologies, this invention proposes a pre-charging control circuit for switching power supplies. This circuit uses a control method that directly detects the voltage across a large-capacity capacitor to close the relay, thus overcoming the shortcomings of existing control methods and making the pre-charging circuit more reliable.

[0006] To achieve the above objectives, this utility model provides the following technical solution:

[0007] A pre-charge control circuit for a switching power supply includes a power module 15 and a relay 16, and also includes a pre-charge module 11 for pre-charging, a voltage divider module 12 for dividing the electrical energy on the energy storage module 13, an energy storage module 13 for storing electrical energy, and a switch module 14 for switching the circuit on and off according to the control voltage output by the voltage divider module 12.

[0008] The external input is connected to the input terminal of the pre-charge module 11 and one end of the relay 16, respectively. The output terminal of the pre-charge module 11 is connected to the input terminal of the energy storage module 13 and the input terminal of the voltage divider module 12, respectively. The output terminals of the energy storage module 13 and the voltage divider module 12 are connected in parallel and then connected to the first input terminal of the switch module 14. The second input terminal of the switch module 14 is connected to the output terminal of the power module 15. The output terminal of the switch module 14 is connected to the other end of the relay 16. The output terminal of the relay 16 is connected to the output interface.

[0009] Preferably, when the external input is AC power, the pre-charge module 11 includes a first resistor and a first diode D1, wherein the first diode is an AC rectifier silicon bridge.

[0010] Preferably, the positive terminal of the external input is connected to one end of the first resistor and the third contact of the relay, and the other end of the first resistor is connected to the third port of the first diode and the fourth contact of the relay; the negative terminal of the external input is connected to the second port of the first diode, and the first port of the first diode is grounded.

[0011] The fourth port of the first diode is connected to one end of the first capacitor and one end of the fifth resistor. The other end of the first capacitor, one end of the sixth resistor, and the input terminal of the first voltage regulator are connected in parallel and then grounded. The other end of the fifth resistor and the other end of the sixth resistor are connected in parallel and then connected to the detection terminal of the first voltage regulator. The output terminal of the first voltage regulator is connected to one end of the fourth resistor. The other end of the fourth resistor and one end of the third resistor are connected in parallel and then connected to the base of the first transistor. The other end of the third resistor and the emitter of the first transistor are connected in parallel and then connected to the power module.

[0012] The collector of the first transistor is connected to the first contact of the relay, and the second contact of the relay is grounded.

[0013] Preferably, when the output control voltage of the voltage divider of the fifth and sixth resistors is higher than the reference voltage of the first voltage regulator, the first voltage regulator provides bias current to the first transistor, the first transistor turns on, the power supply voltage is applied to the control coil of the relay, the control coil is energized, and the relay turns on.

[0014] Preferably, it also includes a hysteresis circuit:

[0015] The first contact of the relay is connected to the positive terminal of the third diode, the negative terminal of the third diode is connected to one end of the second resistor, and the other end of the second resistor is connected to the detection terminal of the first voltage regulator.

[0016] Preferably, it further includes a second diode:

[0017] The second contact of the relay is connected to the positive terminal of the second diode, and the negative terminal of the second diode is connected to the first contact of the relay.

[0018] Preferably, the first transistor is a PNP type.

[0019] Preferably, the first voltage regulator is a TL431.

[0020] Preferably, when the external input is DC power, the pre-charge module 11 only includes the first resistor.

[0021] Preferably, the positive terminal of the external input is connected to one end of the first resistor and the third contact of the relay, and the other end of the first resistor is connected to the fourth contact of the relay, the first end of the first capacitor, and one end of the fifth resistor; the negative terminal of the external input is grounded.

[0022] In summary, by adopting the above technical solution, compared with the prior art, this utility model has at least the following beneficial effects:

[0023] This application addresses the shortcomings of existing control methods, such as large differences in charging voltage, poor pre-charging performance, complex circuitry, and numerous components, by directly detecting the voltage across a large-capacity capacitor to close the relay. This avoids burning out the pre-charging resistor and makes the pre-charging circuit more reliable. Attached image description:

[0024] Figure 1 This is a schematic diagram of a pre-charge control circuit for a switching power supply according to an exemplary embodiment 1 of the present invention.

[0025] Figure 2 This is a schematic diagram of a pre-charge control circuit for a switching power supply according to an exemplary embodiment 2 of the present invention.

[0026] Figure 3 This is a schematic diagram of a pre-charge control circuit for a switching power supply according to Exemplary Embodiment 3 of the present invention. Detailed Implementation

[0027] The present invention will be further described in detail below with reference to embodiments and specific implementation methods. However, it should not be construed as limiting the scope of the above-mentioned subject matter of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0028] In the description of this utility model, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and 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. Therefore, they should not be construed as limitations on this utility model.

[0029] In the description of this utility model, unless otherwise specified and limited, it should be noted that the terms "installation", "connection" and "linking" should be interpreted broadly. For example, they can refer to mechanical or electrical connections, or internal connections between two components. They can be direct connections or indirect connections through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0030] Example 1

[0031] like Figure 1 As shown, this application provides a pre-charge control circuit for a switching power supply, including a pre-charge module 11, an energy storage module 13, a voltage divider module 12, a switching module 14, a power supply module 15, and a relay 16.

[0032] External inputs (external power supply, including AC input and DC input) are connected to the input terminal of the pre-charge module 11 and one end of the relay 16, respectively. The output terminal of the pre-charge module 11 is connected to the input terminal of the energy storage module 13 and the input terminal of the voltage divider module 12, respectively. The output terminals of the energy storage module 13 and the voltage divider module 12 are connected in parallel and then connected to the first input terminal of the switch module 14. The second input terminal of the switch module 14 is connected to the output terminal of the power module 15. The output terminal of the switch module 14 is connected to the other end of the relay 16. The output terminal of the relay 16 is connected to the output interface.

[0033] The working principle of this utility model is as follows:

[0034] Upon power-on, the external input voltage charges the energy storage module 13 via the pre-charge module 11, causing the voltage across the energy storage module 13 to gradually increase. The voltage divider module 12 divides the voltage across the energy storage module 13 and outputs a control voltage to the switch module 14. When the control voltage exceeds the reference voltage of the switch module 14, the switch module 14 is turned on, thereby applying the power supply voltage of the power module 15 to the relay 16. The relay 16 closes, and the external input load outputs electrical energy through the relay 16 and the output port.

[0035] Example 2

[0036] like Figure 2 As shown, when the external input is AC (alternating current) input, the pre-charge module 11 includes a first resistor R1 (pre-charge resistor) and a first diode D1 (AC rectifier silicon bridge, used to convert the input AC to DC), the energy storage module 13 includes a first capacitor C1 (pre-charge capacitor), the voltage divider module 12 includes a fifth resistor R5 and a sixth resistor R6, the switch module 14 includes a first controllable precision voltage regulator U1 (TL431), a fourth resistor R4 and a first transistor Q1, the power supply module 15 includes a power supply VCC, and the relay 16 includes a first contact 1, a second contact 2, a third contact 3 and a fourth contact 4.

[0037] Therefore, in this embodiment, the specific circuit structure of a pre-charge control circuit for a switching power supply is as follows:

[0038] The positive terminal of the external input is connected to one end of the first resistor R1 and the third contact 3 of the relay, respectively. The other end of the first resistor R1 is connected to the third port of the first diode D1 and the fourth contact 4 of the relay, respectively. The negative terminal of the external input is connected to the second port of the first diode D1. The first port of the first diode D1 is grounded. The first port of the first diode D1 is also connected to the negative terminal of the DC output.

[0039] The fourth port of the first diode D1 is connected to one end of the first capacitor C1, one end of the fifth resistor R5, and the positive terminal of the DC output terminal. The other end of the first capacitor C1, one end of the sixth resistor R6, and the input terminal of the first voltage regulator U1 are connected in parallel and then grounded. The other end of the fifth resistor R5 and the other end of the sixth resistor R6 are connected in parallel and then connected to the detection terminal of the first voltage regulator U1. The output terminal of the first voltage regulator U1 is connected to one end of the fourth resistor R4. The other end of the fourth resistor R4 and one end of the third resistor R3 are connected in parallel and then connected to the base of the first transistor Q1 (PNP type). The other end of the third resistor R3 and the emitter of the first transistor Q1 are connected in parallel and then connected to the power module (VCC).

[0040] The collector of the first transistor Q1 is connected to the first contact 1 of the relay RLY1, and the second contact 2 of the relay RLY1 is grounded.

[0041] In this embodiment, the working principle of a pre-charge control circuit for a switching power supply is as follows:

[0042] Upon power-on, an external AC input voltage charges the energy storage capacitor C1 through the pre-charging resistor R1, causing the voltage across C1 to gradually increase. Simultaneously, resistors R5 and R6 divide the voltage across C1. When the output control voltage from the R5 and R6 voltage divider exceeds the internal reference voltage of U1, U1 outputs a voltage that provides bias current to Q1 via resistor R4, causing Q1 to conduct. The VCC power supply voltage is then applied to the relay's control coil, energizing it. This energizes the relay's third contact 3 and fourth contact 4, closing the relay and enabling it to conduct. The external input then outputs electrical energy to the load through relay 16 and the output port.

[0043] The output voltage is controlled by resistors R5 and R6, ensuring that the voltage across the pre-charge capacitor C1 reaches the designed value, turning on transistor Q1 and energizing the relay's control coil. Upon power-on, capacitor C1 begins charging through pre-charge resistor R1, gradually increasing the voltage across it. When the voltage division value of resistors R5 and R6 exceeds the internal reference voltage of U1, U1 outputs a low voltage, providing bias current to Q1 through R4. Q1 then conducts, applying the VCC power supply voltage to the relay coil, closing the relay.

[0044] In this embodiment, a hysteresis circuit is also included to prevent the relay from frequently tripping during charging; the hysteresis circuit includes a second resistor R2 and a third diode D3.

[0045] The first contact 1 of the relay is connected to the positive terminal of the third diode D3, the negative terminal of the third diode D3 is connected to one end of the second resistor R2, and the other end of the second resistor R2 is connected to the detection terminal of the first voltage regulator U1.

[0046] In this embodiment, a second diode D2 is also included to absorb the peak voltage generated when the relay is turned off.

[0047] The second contact 2 of the relay is connected to the positive terminal of the second diode D2, and the negative terminal of the second diode D2 is connected to the first contact 1 of the relay.

[0048] Example 3

[0049] like Figure 3 As shown, when the external input is DC (direct current) input, the pre-charge module 11 includes a first resistor R1 (pre-charge resistor), the energy storage module 13 includes a first capacitor C1, the voltage divider module 12 includes a fifth resistor R5 and a sixth resistor R6, the switch module 14 includes a first voltage regulator U1, a fourth resistor R4 and a first transistor Q1, the power supply module 15 includes a power supply VCC, and the relay 16 includes a first contact 1, a second contact 2, a third contact 3 and a fourth contact 4.

[0050] Therefore, in this embodiment, the specific circuit structure of a pre-charge control circuit for a switching power supply is as follows:

[0051] The positive terminal of the external input is connected to one end of the first resistor R1 and the third contact 3 of the relay. The other end of the first resistor R1 is connected to the fourth contact 4 of the relay, the first end of the first capacitor C1, one end of the fifth resistor R5, and the positive terminal of the DC output. The negative terminal of the external input is grounded. The negative terminal of the DC output is grounded.

[0052] The other structures and working principles of the circuit are the same as in Embodiment 2, so they will not be described in detail here.

[0053] Those skilled in the art will understand that the above embodiments are specific examples of implementing the present invention, and in practical applications, various changes can be made to them in form and detail without departing from the spirit and scope of the present invention.

Claims

1. A pre-charge control circuit for a switching power supply comprising a power module (15) and a relay (16) characterized in that, The pre-charging module (11) is used for pre-charging, the voltage dividing module (12) is used for voltage dividing the electric energy on the energy storage module (13), the energy storage module (13) is used for storing the electric energy, and the switch module (14) is used for realizing circuit breaking according to the control voltage output by the voltage dividing module (12). The external input is connected with the input end of the pre-charging module (11) and one end of the relay (16) respectively, the output end of the pre-charging module (11) is connected with the input end of the energy storage module (13) and the input end of the voltage dividing module (12) respectively, the output end of the energy storage module (13) and the output end of the voltage dividing module (12) are connected with the first input end of the switch module (14) in parallel, the second input end of the switch module (14) is connected with the output end of the power module (15), the output end of the switch module (14) is connected with the other end of the relay (16), and the output end of the relay (16) is connected with the output interface.

2. A precharge control circuit for a switching power supply as recited in claim 1, wherein, When the external input is an alternating current, the pre-charging module (11) comprises a first resistor and a first diode D1, and the first diode is an alternating current rectification silicon bridge.

3. A precharge control circuit for a switching power supply as recited in claim 2, wherein, The positive electrode of the external input is connected with one end of the first resistor and the third contact of the relay respectively, the other end of the first resistor is connected with the third port of the first diode and the fourth contact of the relay respectively, and the negative electrode of the external input is connected with the second port of the first diode. The fourth port of the first diode is connected with one end of the first capacitor and one end of the fifth resistor respectively, the other end of the first capacitor, one end of the sixth resistor and the input end of the first voltage stabilizer are connected with the ground in parallel, the other end of the fifth resistor and the other end of the sixth resistor are connected with the detection end of the first voltage stabilizer in parallel, the output end of the first voltage stabilizer is connected with one end of the fourth resistor, the other end of the fourth resistor and one end of the third resistor are connected with the base of the first triode in parallel, and the other end of the third resistor and the emitter of the first triode are connected with the power module in parallel. The collector of the first triode is connected with the first contact of the relay, and the second contact of the relay is grounded.

4. A precharge control circuit for a switching power supply as recited in claim 3, wherein, When the output control voltage of the fifth resistor and the sixth resistor is higher than the reference voltage of the first voltage stabilizer, the first voltage stabilizer provides a bias current for the first triode, the first triode is turned on, the power supply voltage is added to the control coil of the relay, the control coil is electrified, and the relay is turned on.

5. A precharge control circuit for a switching power supply as recited in claim 3, wherein, The hysteresis circuit further comprises a third diode: The first contact of the relay is connected with the positive electrode of the third diode, the negative electrode of the third diode is connected with one end of the second resistor, and the other end of the second resistor is connected with the detection end of the first voltage stabilizer.

6. A precharge control circuit for a switching power supply as recited in claim 3, wherein, The relay further comprises a second diode: The second contact of the relay is connected with the positive electrode of the second diode, and the negative electrode of the second diode is connected with the first contact of the relay.

7. A precharge control circuit for a switching power supply as recited in claim 3, wherein, The first triode is a PNP type.

8. A precharge control circuit for a switching power supply as recited in claim 3, wherein, The model of the first voltage stabilizer is TL431.

9. A precharge control circuit for a switching power supply as recited in claim 1, wherein, When the external input is a direct current, the pre-charging module (11) only comprises the first resistor.

10. A precharge control circuit for a switching power supply as recited in claim 9, wherein, The positive electrode of the external input is connected with one end of the first resistor and the third contact of the relay respectively, the other end of the first resistor is connected with the fourth contact of the relay, the first end of the first capacitor and one end of the fifth resistor respectively, and the negative electrode of the external input is grounded.

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