Slow start switch filter circuit and circuit board

Abstract

The utility model relates to a slow start switch filter circuit and a circuit board, and belongs to the technical field of switch circuits. The circuit comprises a slow start switch circuit, a differential mode filter circuit and a common mode filter circuit which are sequentially connected with an input power supply, the slow start switch circuit comprises an MOS tube U1; the first resistor R1 is connected in parallel between the input end and the control end of the MOS tube U1; the first capacitor C1 is connected in parallel between the input end and the control end of the MOS tube U1; one end of the second resistor R2 is connected with the control end of the MOS tube U1, and the second capacitor C2 is connected between the first output end and the second output end of the slow start switch circuit in parallel. According to the utility model, the power-on speed and the power-off speed of the power supply are slowed down through the slow start switch circuit, the current impact at the starting moment is reduced, and after power-on, the differential mode filter circuit and the common mode filter circuit are used for filtering differential mode interference and common mode interference entering the load from external power supply equipment, so that the operation stability of the load is improved.

Description

Technical Field

[0001] This utility model belongs to the field of switching circuit technology, and relates to a soft-start switch filter circuit and circuit board. Background Technology

[0002] With the increasing popularity and development of electronic products, the power-on and power-off processes have gradually attracted attention. During power-on and power-off, spike signals can easily be generated on the power lines, potentially affecting the product itself and the power supply equipment. Unpredictable spike signals can damage the product's lifespan and system stability.

[0003] Patent CN221448381U discloses a DC power supply soft-start switching circuit. It controls the switching of another MOSFET by receiving a switching control signal at the gate of the MOSFET to turn it on or off. Because it requires generating a switching signal, this invention is suitable for use in circuits that can generate switching control signals. Patent CN219802155U discloses a high-current soft-start switching circuit for lasers. It uses a transistor to control another MOSFET to slowly start the switching circuit, gradually increasing the output voltage until it matches the input voltage, avoiding the instantaneous jump to the highest voltage that occurs when the switching circuit of a traditional laser closes. This invention also requires an additional control signal to drive a transistor to control the MOSFET's switching. Since the transistor is a current-controlled device, it generates additional power consumption. Furthermore, this invention does not include a protection design for the MOSFET; voltage spikes exceeding the gate-gate withstand voltage during switching may damage the MOSFET, leading to power supply failure in subsequent circuits. Utility Model Content

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a soft-start switch filter circuit and circuit board, which can slow down the power-on and power-off speed of the power supply, reduce the current surge at the moment of startup, and filter out power supply noise.

[0005] To achieve the above objectives, this utility model employs the following technical solution:

[0006] In a first aspect, this utility model provides a soft-start filter switching circuit, comprising:

[0007] A soft-start switch circuit connected to the input power supply;

[0008] A differential-mode filter circuit is connected to the output terminal of the soft-start switch circuit to filter out differential-mode interference from the input power supply entering the load.

[0009] A common-mode filter circuit is connected between the output of the differential-mode filter circuit and the load to filter out common-mode interference from the input power supply entering the load.

[0010] The slow start switch circuit comprises:

[0011] a MOS tube U1, an output end of which is a first output end of the slow start switch circuit;

[0012] a first resistor R1 connected in parallel between an input end and a control end of the MOS tube U1;

[0013] a first capacitor C1 connected in parallel between the input end and the control end of the MOS tube U1;

[0014] a second resistor R2, one end of which is connected to the control end of the MOS tube U1, and the other end of which is a second output end of the slow start switch circuit;

[0015] a second capacitor C2 connected in parallel between the first output end and the second output end of the slow start switch circuit.

[0016] Further, the slow start switch circuit further comprises a voltage stabilizing diode D1 connected in parallel between the input end and the control end of the MOS tube U1.

[0017] Further, the MOS tube U1 is a P-channel MOS tube, a source of the P-channel MOS tube is the input end, a drain of the P-channel MOS tube is the output end, and a gate of the P-channel MOS tube is the control end.

[0018] Further, the differential mode filter circuit comprises a first inductor L1, a second inductor L2 and a fourth capacitor C4;

[0019] The first inductor L1 and the second inductor L2 are respectively connected to two ends of the fourth capacitor C4;

[0020] The other end of the first inductor L1 is connected to the first output end of the slow start switch circuit, and the other end of the second inductor L2 is connected to the second output end of the slow start switch circuit.

[0021] Further, a first output end of the differential mode filter circuit is connected between the first inductor L1 and the fourth capacitor C4, and a second output end of the differential mode filter circuit is connected between the second inductor L2 and the fourth capacitor C4.

[0022] Further, the common mode filter circuit comprises a common mode inductor L3, a fifth capacitor C5 and a sixth capacitor C6;

[0023] Two input ends of the common mode inductor L3 are respectively connected to the first output end and the second output end of the differential mode filter circuit;

[0024] Two output ends of the common mode inductor L3 are respectively connected to the fifth capacitor C5 and the sixth capacitor C6;

[0025] The other end of the fifth capacitor C5 and the other end of the sixth capacitor C6 are grounded.

[0026] Further, the first output end of the common mode filter circuit is connected between the common mode inductor L3 and the fifth capacitor C5, and the second output end of the common mode filter circuit is connected between the common mode inductor L3 and the sixth capacitor C6.

[0027] The power input end of the load is connected with the first output end and the second output end of the common mode filter circuit.

[0028] Further, the switch device SW1 in series between the input power supply and the soft start switch circuit is further included.

[0029] Further, the third resistor R3 and the third capacitor C3 are further included.

[0030] The third resistor R3 and the third capacitor C3 are connected in series and then connected in parallel across the switch device SW1.

[0031] In a second aspect, the utility model also provides a circuit board, the circuit board includes the soft start switch filter circuit.

[0032] Compared with the prior art, the utility model has the beneficial effects that:

[0033] The soft start switch filter circuit provided by the utility model forms a voltage division type RC time constant through the first resistor, the second resistor and the first capacitor in the soft start switch circuit, changes the power-on speed of the slow power supply, forms an RC discharge circuit between the second capacitor in the soft start switch circuit and the load, realizes slow closing of power-off, reduces the current impact in the power-on moment of the power supply, and after formal power-on, forms a differential mode filter circuit through the first inductor, the second inductor and the fourth capacitor to filter out the differential mode interference of the external power supply device into the load, forms a common mode filter circuit through the common mode inductor, the fifth capacitor and the sixth capacitor to filter out the common mode interference of the external power supply device into the load, thereby improving the operation stability of the load. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 The structure schematic view of the soft start switch filter circuit provided by the utility model embodiment is shown in the figure.

[0035] Figure 2 The connection structure schematic view of the soft start switch filter circuit and the load in the utility model embodiment is shown in the figure. DETAILED DESCRIPTION

[0036] The technical solution of this utility model will be described in detail below with reference to the accompanying drawings and specific embodiments. The same reference numerals in the drawings indicate the same or similar components or parts. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. The embodiments and specific features within the embodiments of this application are detailed descriptions of the technical solution of this application, and not limitations thereof. Where there is no conflict, the embodiments and technical features within the embodiments of this application can be combined with each other.

[0037] In the description of this utility model, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating the orientation or positional relationship, are 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. Furthermore, the term "and / or" in this document is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0038] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0039] Example 1:

[0040] like Figure 1 As shown, this utility model embodiment provides a soft-start switching filter circuit, including:

[0041] A soft-start switch circuit connected to the input power supply;

[0042] A differential-mode filter circuit is connected to the output terminal of the soft-start switch circuit to filter out differential-mode interference from the input power supply entering the load.

[0043] A common-mode filter circuit is connected between the output of the differential-mode filter circuit and the load to filter out common-mode interference from the input power supply entering the load.

[0044] A switching device SW1 is connected in series between the input power supply and the soft-start switch circuit.

[0045] The soft-start switch circuit includes: a MOSFET U1, whose output terminal is the first output terminal of the soft-start switch circuit; a first resistor R1, connected in parallel between the input terminal and the control terminal of the MOSFET U1; a first capacitor C1, connected in parallel between the input terminal and the control terminal of the MOSFET U1; a second resistor R2, one end of which is connected to the control terminal of the MOSFET U1, and the other end of which is the second output terminal of the soft-start switch circuit; and a second capacitor C2, connected in parallel between the first output terminal and the second output terminal of the soft-start switch circuit.

[0046] In this embodiment of the invention, MOS transistor U1 is a P-channel MOS transistor (PMOS transistor). The source of the PMOS transistor is the input terminal, the drain is the output terminal, and the gate is the control terminal. Its turn-on voltage is... -3V -60V ±20V The voltage rating is -12A; the first capacitor C1 and the second capacitor C2 are tantalum capacitors, and the third capacitor C3, the fourth capacitor C4, the fifth capacitor C5, and the sixth capacitor C6 are ceramic capacitors. Specifically, the capacitance of the first capacitor C1 is 22uF, the capacitance of the second capacitor C2 is 100nF, the capacitance of the third capacitor C3 is 100nF, the capacitance of the fourth capacitor C4 is 100nF, the capacitance of the fifth capacitor C5 is 470nF, and the capacitance of the sixth capacitor C6 is 470nF; the voltage rating of the Zener diode D1 is 12V; the resistance of the first resistor R1 is 15kΩ, the resistance of the second resistor R2 is 30kΩ, and the resistance of the third resistor R3 is 10kΩ; the first inductor L1 and the second inductor L2 are surface mount inductors, both with an inductance of 4.7mH; the common mode inductor L3 has an impedance of 350Ω at 100MHz.

[0047] When switching device SW1 is open, the circuit is not conducting. When switching device SW1 is closed, the first resistor R1, the second resistor R2, and the first capacitor C1 in the soft-start switching circuit form a voltage divider RC time constant. The first capacitor C1 is connected in parallel across the gate and source of MOSFET U1. When the power is first turned on, the first capacitor C1 is not charged. When MOSFET U1 is not turned on, the power supply cannot pass through the soft-start switch filter circuit disclosed herein, and therefore cannot supply power to the load; the power supply slowly charges the first capacitor C1 through the first resistor R1 and the second resistor R2. When the voltage of the first capacitor C1 reaches the turn-on voltage of MOSFET U1... At this time, the source and drain of MOSFET U1 are turned on.

[0048] The process of the power supply charging the first capacitor C1 serves to delay the power-on process, with a delay time of:

[0049] ,

[0050] in, Let R1 be the resistance value of the first resistor. Let R2 be the resistance value of the second resistor. To delay time, This is the power supply input voltage. , The time constant of the voltage divider RC circuit is calculated using the following formula:

[0051] ,

[0052] Substituting the above values ​​into the calculation yields the delay time. It takes approximately 85.31 ms.

[0053] After MOSFET U1 is turned on, Continue increasing (until it reaches around 10V), As the voltage decreases rapidly, the second capacitor C2 is slowly charged, and the output voltage of the soft-start switching circuit gradually increases until it is basically consistent with the input voltage, at which point the load is powered on. Throughout the process, the output voltage does not jump to its highest point instantaneously, but rises slowly, thus greatly reducing the interference of inrush current.

[0054] When the switching device SW1 changes from closed to open, the second capacitor C2 discharges to the outside, and an RC discharge circuit is formed between the second capacitor C2 and the load. Therefore, the voltage slowly drops to 0V, completing the slow shutdown.

[0055] In addition, the soft-start switch circuit also includes a Zener diode D1 connected in parallel between the gate and source of the MOSFET U1. The Zener diode D1 is used to protect the MOSFET U1. When the voltage difference between the gate and source of the MOSFET U1 is greater than 12V, the Zener diode D1 conducts, clamping the voltage between the gate and source of the MOSFET U1 at 12V, preventing the MOSFET U1 from being damaged due to excessive voltage difference between its gate and source.

[0056] A third resistor R3 and a third capacitor C3 are connected in parallel across the two ends of the switching device SW1, and the third resistor R3 and the third capacitor C3 are connected in series. When the switch changes from closed to open, the third capacitor C3 is charged. When the switch changes from open to closed, the third capacitor C3 discharges through the switch to form a circuit. This process can reduce voltage fluctuations and current spikes caused by the switching device SW1 when switching between open and closed states.

[0057] The differential mode filter circuit includes a first inductor L1, a second inductor L2, and a fourth capacitor C4; the first inductor L1 and the second inductor L2 are respectively connected to the two ends of the fourth capacitor C4; the other end of the first inductor L1 is connected to the first output terminal of the soft start switch circuit, and the other end of the second inductor L2 is connected to the second output terminal of the soft start switch circuit.

[0058] The first output terminal of the differential mode filter circuit is connected between the first inductor L1 and the fourth capacitor C4, and the second output terminal of the differential mode filter circuit is connected between the second inductor L2 and the fourth capacitor C4.

[0059] The common-mode filter circuit includes a common-mode inductor L3, a fifth capacitor C5, and a sixth capacitor C6. The two input terminals of the common-mode inductor L3 are connected to the first and second output terminals of the differential-mode filter circuit, respectively. The two output terminals of the common-mode inductor L3 are connected to the fifth capacitor C5 and the sixth capacitor C6, respectively. The other ends of the fifth capacitor C5 and the sixth capacitor C6 are grounded.

[0060] The first output terminal of the common-mode filter circuit is connected between the common-mode inductor L3 and the fifth capacitor C5, and the second output terminal of the common-mode filter circuit is connected between the common-mode inductor L3 and the sixth capacitor C6.

[0061] The first and second output terminals of the common-mode filter circuit are also the output terminals of the soft-start switch filter circuit of this utility model. For example... Figure 2 As shown, the power input terminal of the load is connected to the first and second output terminals of the common-mode filter circuit.

[0062] After power-on, the first inductor L1, the second inductor L2, and the fourth capacitor C4 form a differential-mode filter circuit to filter out differential-mode interference from external power supply equipment entering the load. The common-mode inductor L3, the fifth capacitor C5, and the sixth capacitor C6 form a common-mode filter circuit to filter out common-mode interference from external power supply equipment entering the load, thereby improving the operating stability of the load.

[0063] Secondly, this utility model embodiment also provides a circuit board, including the soft-start switch filter circuit of the above embodiment.

[0064] The above description is only a preferred embodiment of the present utility model. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present utility model, and these improvements and modifications should also be considered within the scope of protection of this disclosure / application.

Claims

1. A soft-start switching filter circuit, characterized in that, include: A soft-start switch circuit connected to the input power supply; A differential-mode filter circuit is connected to the output terminal of the soft-start switch circuit to filter out differential-mode interference from the input power supply entering the load. A common-mode filter circuit is connected between the output of the differential-mode filter circuit and the load to filter out common-mode interference from the input power supply entering the load. The soft-start switch circuit includes: MOSFET U1, whose output terminal is the first output terminal of the soft-start switch circuit; The first resistor R1 is connected in parallel between the input terminal and the control terminal of the MOS transistor U1; The first capacitor C1 is connected in parallel between the input terminal and the control terminal of the MOS transistor U1; The second resistor R2 has one end connected to the control terminal of the MOS transistor U1, and the other end is the second output terminal of the soft-start switch circuit. The second capacitor C2 is connected in parallel between the first and second output terminals of the soft-start switch circuit.

2. The soft-start switch filter circuit according to claim 1, characterized in that, The soft-start switch circuit also includes a Zener diode D1 connected in parallel between the input terminal and the control terminal of the MOS transistor U1.

3. The soft-start switch filter circuit according to claim 2, characterized in that, The MOS transistor U1 is a P-channel MOS transistor, with the source being the input terminal, the drain being the output terminal, and the gate being the control terminal.

4. The soft-start switch filter circuit according to claim 1, characterized in that, The differential mode filter circuit includes a first inductor L1, a second inductor L2, and a fourth capacitor C4; The first inductor L1 and the second inductor L2 are respectively connected to the two ends of the fourth capacitor C4; The other end of the first inductor L1 is connected to the first output terminal of the soft-start switch circuit, and the other end of the second inductor L2 is connected to the second output terminal of the soft-start switch circuit.

5. The soft-start switch filter circuit according to claim 4, characterized in that, The first output terminal of the differential mode filter circuit is connected between the first inductor L1 and the fourth capacitor C4, and the second output terminal of the differential mode filter circuit is connected between the second inductor L2 and the fourth capacitor C4.

6. The soft-start switch filter circuit according to claim 5, characterized in that, The common-mode filter circuit includes a common-mode inductor L3, a fifth capacitor C5, and a sixth capacitor C6. The two input terminals of the common-mode inductor L3 are respectively connected to the first output terminal and the second output terminal of the differential-mode filter circuit; The two output terminals of the common-mode inductor L3 are respectively connected to the fifth capacitor C5 and the sixth capacitor C6; The other end of the fifth capacitor C5 and the other end of the sixth capacitor C6 are grounded.

7. The soft-start switch filter circuit according to claim 6, characterized in that, The common-mode inductor L3 and the fifth capacitor C5 are connected to the first output terminal of the common-mode filter circuit, and the common-mode inductor L3 and the sixth capacitor C6 are connected to the second output terminal of the common-mode filter circuit. The power input terminal of the load is connected to the first and second output terminals of the common-mode filter circuit.

8. The soft-start switch filter circuit according to claim 1, characterized in that, It also includes a switching device SW1 connected in series between the input power supply and the soft-start switch circuit.

9. The soft-start switching filter circuit according to claim 8, characterized in that, It also includes the third resistor R3 and the third capacitor C3; The third resistor R3 and the third capacitor C3 are connected in series and then in parallel across the two ends of the switching device SW1.

10. A circuit board, characterized in that, Includes the soft-start switch filter circuit as described in any one of claims 1 to 9.

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