Soft start circuit having switching function

Abstract

A soft start circuit having a switching function. The soft start circuit comprises a switch device (U) connected in series between a power input end (VIN) and a power output end (VOUT), and further comprises a switch device control unit (200) coupled to the switch device (U). One end of the switch device control unit (200) is coupled to the power input end (VIN); the switch device control unit (200) is provided with a powerdown pin; the powerdown pin is signaled to an external controller; and the external controller controls the powerdown pin to implement the disconnection of current output, so as to control the turn-off of the switch device (U). The technical solution has the beneficial effect that: the powerdown pin is connected between the power input end (VIN) and the switch device (U), so that the external controller controls to pull up the powerdown pin, to control the disconnection of the current output, so as to implement the turn-off of the switch device (U). The present invention has the characteristics of a soft start circuit, implements a circuit switching function due to the addition of a control unit, and has the advantages of low power consumption and good control effects.

Description

A slow start circuit with switching function

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on November 24, 2023, with application number 202323182196.4 and invention name “A slow start circuit with switching function”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The utility model belongs to the technical field of power-on circuits, and in particular relates to a soft start circuit with a switch function. Background Art

[0003] The rapid development of electronic information technology has led to a wide variety of problems in electronic design and application. In particular, high voltage differentials can occur during the startup of capacitive load circuits, causing severe damage or even destruction to front-end and back-end equipment. A capacitive load generally refers to a load with capacitance parameters, i.e., a load with a current-leading-voltage characteristic. During charging and discharging, the voltage of a capacitive load cannot change suddenly, resulting in a negative power factor, while the power factor of an inductive load is positive. To address this, various devices designed to mitigate high voltage differentials have emerged. When external interference suddenly generates a spike in current or voltage in an electrical circuit or communication line, these devices can conduct and shunt the current in a very short time, thereby preventing damage to other equipment in the circuit caused by the high voltage differential.

[0004] To prevent damage to system components caused by sudden voltage surges or current spikes, commonly used technologies often employ a slow-start circuit to prevent high-voltage differentials. This circuit typically incorporates a MOS field-effect transistor (MOSFET) with an RC network consisting of a resistor and capacitor attached to the MOSFET's gate. When the system is powered on, the RC network begins charging, gradually increasing the MOSFET's gate voltage and, consequently, the MOSFET's conduction state. As the gate voltage gradually rises, the MOSFET's conduction state gradually increases, eventually reaching a fully on state. This allows for slow charging of the load capacitor and ensures stable system operation.

[0005] However, the RC network composed of MOS field-effect transistors and auxiliary components in conventional technology has the problem that the slow-start circuit only supports power-on. As shown in Figure 1, the slow-start circuit in conventional technology can achieve slow startup by combining filter capacitors with MOS transistors. However, this slow-start circuit only supports power-on. To shut down the circuit, components such as switches must be introduced, which not only increases the number of components in the circuit but also increases the power consumption. Therefore, it is necessary to design a new slow-start circuit that can achieve both power-on and shutdown functions. Utility Model Content

[0006] The utility model provides a slow-start circuit with a switching function, which can realize the slow-start function and the switching function without adding an additional switching tube.

[0007] Other purposes and advantages of the present invention can be further understood from the technical features disclosed in the present invention.

[0008] To achieve one, some, or all of the above-mentioned objectives, or other objectives, a technical solution of the present invention provides a soft-start circuit with a switching function, comprising a power input and a power output. The soft-start circuit includes: a switching device connected in series to the power input and the power output; and a switching device control unit coupled to the switching device. One end of the switching device control unit is coupled to the power input. The switching device control unit is provided with a powerdown pin, which is connected to an external controller signal. The external controller controls the powerdown pin to disconnect the current output and thereby control the switching device to turn off. The beneficial effect of the device of the present invention is that the device of the present invention connects a switching device control unit between the power input and the switching device, wherein the switching device is a MOS transistor, which is connected to the connection line between the power input and the MOS transistor gate. The switching device control unit is a powerdown pin. The powerdown pin is controlled by an external controller to pull high to disconnect the output current, thereby controlling the MOS transistor to turn off. The device has the characteristics of a soft-start circuit and realizes a circuit switching function by adding a control unit. The switching device has the advantages of small size and intelligent control.

[0009] A filter capacitor is connected in parallel between the switching device and the power input terminal; the filter capacitor controls the on and off timing of the switching device; the other end of the filter capacitor coupled to the power input terminal is coupled to the powerdown pin. The filter capacitor supplies power to the gate of the MOS transistor. When the powerdown pin is turned on, a voltage difference is generated across the filter capacitor, disconnecting the filter capacitor, causing the MOS transistor gate voltage to drop, and gradually closing the MOS transistor's current path. The powerdown pin and filter capacitor work together to achieve the circuit's switching function.

[0010] The external controller disconnects the current output by pulling up the powerdown pin, opens the powerdown pin, and then enables the discharge current of the filter capacitor to flow out from the powerdown pin, so that the switch device is disconnected.

[0011] The external signal controller is a single chip microcomputer controller.

[0012] The switching device control unit further includes a current regulating element, which is connected in series between the filter capacitor and the powerdown pin, and is used to regulate the speed at which the discharge current of the filter capacitor flows out of the powerdown pin.

[0013] The current regulating element is a resistor R1 or a diode D1 , and the conducting direction of the diode D1 is from the filter capacitor toward the powerdown pin.

[0014] The current regulating element can control the current from the filter capacitor to the powerdown pin current output end. The resistor R1 reduces the passing current by the resistance value, and the diode D1 reduces the current by the tube voltage drop. The current regulating element can control the current discharge speed of the filter capacitor.

[0015] The switch device is a P-channel MOS transistor, the gate of the P-channel MOS transistor is coupled to the filter capacitor, the source is coupled to the power input terminal and the filter capacitor, and the drain is coupled to the power output terminal.

[0016] The slow start circuit is also provided with a current discharge channel and a voltage stabilizing capacitor, one end of the voltage stabilizing capacitor is coupled to the power output terminal and the other end is grounded; the current discharge channel (100) is coupled between the filter capacitor and the voltage stabilizing capacitor, and the current discharge channel (100) is used to discharge current from the voltage stabilizing capacitor into the filter capacitor through the current discharge channel (100) after the power input terminal is powered off.

[0017] The current discharge channel includes a diode D2 coupled to the grounded end of the voltage-stabilizing capacitor. Diode D2 conducts from the voltage-stabilizing capacitor toward the filter capacitor. Diode D2 is used to allow discharge current from the voltage-stabilizing capacitor to flow to the filter capacitor after the power output is disconnected. When the power input is disconnected, the current discharge channel releases energy from the voltage-stabilizing capacitor and flows through diode D2 to the plate of the filter capacitor. This reduces the turn-on time of the switching device when the circuit is next started, speeding up power-up.

[0018] Voltage-dividing resistors R2 and R3 are further provided between the diode D2 and the voltage-stabilizing capacitor; the voltage-dividing resistor R2 is connected in parallel above the diode D2; and the voltage-dividing resistor R3 is provided below the coupling point between the voltage-stabilizing capacitor and the diode D2.

[0019] The diodes D1 and D2 are voltage stabilizing diodes.

[0020] Compared with the commonly used technologies, the beneficial effects of the present invention mainly include:

[0021] 1. Set a powerdown pin connected to an external controller. The controller can pull up the powerdown pin to open the powerdown pin for current discharge. The voltage difference across the filter capacitor will be disconnected. At this time, the current channel of the switching device is gradually closed. By setting the powerdown pin, the switching function can be realized under the premise that the circuit has a slow start function, while not increasing the circuit area or the circuit power consumption.

[0022] 2. By setting up a current discharge channel, after the circuit is temporarily shut down, the voltage-stabilizing capacitor at the power output end releases current through the voltage-stabilizing diode D2 and enters the filter capacitor for storage, thereby reducing the next power-on time.

[0023] In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below with reference to the accompanying drawings for detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the specific embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] FIG1 is a schematic diagram of a soft start circuit in a common technology.

[0026] FIG2 is a schematic diagram of a soft start circuit with a switch function of the device of the present invention.

[0027] FIG3 is a schematic diagram of another embodiment of a switch device control unit in the device of the present invention.

[0028] In the figure, 100 is a current discharge channel; 200 is a switching device control unit. DETAILED DESCRIPTION

[0029] The aforementioned and other technical aspects, features, and functions of the present invention are clearly presented in the following detailed description of a preferred embodiment with reference to the accompanying drawings. Directional terms such as up, down, left, right, front, and back, used in the following embodiments, are merely references to the directions in the accompanying drawings. Therefore, the directional terms used are for illustrative purposes only and are not intended to limit the present invention.

[0030] Figure 2 is a schematic diagram of a soft-start circuit with a switching function in a device according to the present invention. One embodiment of the present invention provides a soft-start circuit comprising a switching device U connected in series between the power input terminal Vin and the power output terminal Vout; the switching device U is a P-channel MOS transistor. The gate G of the P-channel MOS transistor is connected to a filter capacitor C1, the source is coupled to the power input terminal Vin and the filter capacitor C1, and the drain is connected to the power output terminal Vout. The filter capacitor C1 is connected in parallel between the power input terminal Vin and the MOS transistor. The soft-start circuit also includes a switching device U control unit 200 connected to the switching device U. One end of the switching device control unit 200 is connected to the filter capacitor C1. The switching device control unit 200 is provided with a powerdown pin, which is connected to an external controller signal, such as a single-chip microcomputer. The controller can pull the powerdown pin high to enable current output from the powerdown pin to ground, thereby shutting down the soft-start circuit.

[0031] The specific working principle is as follows:

[0032] When the power input terminal Vin is powered on, it provides a gradually rising voltage, typically in milliseconds. During this time, the voltage at the source S of the switching device U increases as the power input voltage rises. The configured filter capacitor C1 has a time constant of several hundred milliseconds, causing the voltage across filter capacitor C1 to rise synchronously during this phase. This keeps the voltage difference between the source S and gate G of the switching device U near zero, and the switching device U remains off.

[0033] When the voltage at the power input terminal VIN gradually stabilizes, the voltages across capacitor C1 become consistent. Capacitor C1 then conducts, energizing the gate G of switching device U. At this point, the voltage at the source S of switching device U remains consistent with the voltage at the power input terminal. The voltage difference between gate G and source S gradually exceeds the threshold voltage of switching device U, gradually increasing the degree of conduction of switching device U until it is fully turned on. The on-resistance of switching device U approaches zero. This is the entire power-up process of the soft-start circuit of the present invention.

[0034] To shut down the slow-start circuit, a switching device control unit 200 is provided. This switching device control unit 200 has a powerdown pin, which is signal-connected to the controller. Specifically, in this embodiment, this pin is signal-connected to the microcontroller. After the slow-start circuit is electrically conductive, when the circuit needs to be disconnected, the microcontroller pulls up the powerdown pin, enabling the current output on one side of the powerdown pin to be turned on. At this point, filter capacitor C1 will discharge current through the powerdown pin. A voltage difference is generated across filter capacitor C1, causing it to become non-conductive. The voltage difference between the source S and gate G of switching device U gradually increases until switching device U is turned off. At this point, the slow-start circuit is closed. To control the shutdown speed of this circuit, the switching device control unit 200 is also provided with a current regulating element. As shown in Figures 2 and 3, this current regulating element can be either a resistor R1 or a diode D1. The resistance value of resistor R1 can be selected based on the required time control. Diode D1 is a voltage-stabilizing diode. It allows current to flow toward the powerdown pin, and its resistance is determined by the voltage drop. Both resistor R1 and diode D1 control the current flowing to the powerdown pin, thereby adjusting the slow-start circuit's turn-off speed.

[0035] In addition, the slow start circuit is also provided with a current discharge channel 100 and a voltage stabilizing capacitor C2. One end of the voltage stabilizing capacitor C2 is connected to the power output terminal Vout, and the other end is grounded; the current discharge channel 100 includes a diode D2 connected to the grounded end of the voltage stabilizing capacitor C2, and the other end of the diode D2 is connected to the filter capacitor C1. The conduction direction of the diode D2 is from the voltage stabilizing capacitor to the filter capacitor C1; the diode D2 is a voltage stabilizing diode that can reduce the input voltage to a stable value output. After the power input terminal Vin is disconnected, the voltage stabilizing capacitor C2 discharges, and part of the current discharged by the voltage stabilizing capacitor C2 flows to the filter capacitor C1 through the diode D2. C1 can store some electrical energy, and the other part of the current discharged by the voltage stabilizing capacitor flows to the ground end. The filter capacitor C1 collects part of the current flowing in through the voltage stabilizing diode D2, so that when the slow start circuit is started again, the voltages at both ends of the voltage stabilizing capacitor can be quickly made consistent, which speeds up the power-on speed of the slow start circuit and saves time.

[0036] At the same time, voltage-dividing resistors R2 and R3 are also provided between the diode D2 and the voltage-stabilizing capacitor C2; the voltage-dividing resistor R2 is connected in parallel above the diode D2, and the resistance value of the voltage-dividing resistor R2 is 1m ohm, which can protect the diode D2 when the voltage-stabilizing capacitor C2 is rapidly discharged; the voltage-dividing resistor R3 is arranged below the voltage-stabilizing capacitor C2 and the diode D2. The voltage-dividing resistor R3 is arranged to prevent the current from being quickly discharged to the ground when the voltage-stabilizing capacitor C2 is discharged, and the current can flow evenly to the diode D2.

[0037] The above describes in detail the soft-start circuit with a switching function provided by the present invention. This article uses specific examples to illustrate the structure and operating principle of the present invention. The description of the above embodiments is intended only to help understand the method and core concept of the present invention. It should be noted that those skilled in the art may make various improvements and modifications to the present invention without departing from the principles of the present invention, and such improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A soft start circuit with a switch function, having a power input terminal and a power output terminal, characterized in that: The soft start circuit comprises: a switch device connected in series between the power input terminal and the power output terminal; and a switch device control unit (200) coupled to the switch device, wherein one end of the switch device control unit (200) is coupled to the power input terminal, and the other end is set as a powerdown pin, the powerdown pin is connected to an external controller, and the external controller controls the closing and opening of the switch device by controlling the powerdown pin.

2. The slow start circuit with switch function according to claim 1, characterized in that: A filter capacitor is connected in parallel between the switch device and the power input terminal; the filter capacitor controls the on and off time of the switch device; and one end of the filter capacitor is coupled to the powerdown pin.

3. The slow start circuit with switch function according to claim 2, characterized in that: The external controller opens the powerdown pin by pulling up the powerdown pin, thereby causing the discharge current of the filter capacitor to flow out of the powerdown pin, thereby disconnecting the switch device.

4. The slow start circuit with switch function according to claim 2, characterized in that: The external signal controller is a single chip microcomputer controller.

5. The slow start circuit with switch function according to claim 3, characterized in that: The switch device control unit (200) further comprises a current regulating element, the current regulating element being connected in series between the filter capacitor and the powerdown pin, and the current regulating element being used to regulate the speed at which the discharge current of the filter capacitor flows out of the powerdown pin.

6. The slow start circuit with switch function according to claim 5, characterized in that: The current regulating element is a diode D1 or a resistor R1, and the conducting direction of the diode D1 is from the filter capacitor toward the powerdown pin.

7. The slow start circuit with switch function according to claim 2, characterized in that: The switch device is a P-channel MOS tube, the gate of the P-channel MOS tube is coupled to the filter capacitor, the source is coupled to the power input terminal and the filter capacitor, and the drain is coupled to the power output terminal.

8. The slow start circuit with switch function according to claim 1, characterized in that: The slow start circuit is also provided with a current discharge channel (100) and a voltage stabilizing capacitor, one end of the voltage stabilizing capacitor is coupled to the power supply output end, and the other end of the voltage stabilizing capacitor is grounded; the current discharge channel (100) is coupled between the filter capacitor and the voltage stabilizing capacitor, and the current discharge channel (100) is used for the voltage stabilizing capacitor to discharge current into the filter capacitor through the current discharge channel (100) after the power supply input end is powered off.

9. The slow start circuit with switch function according to claim 8, characterized in that: The current discharge channel (100) comprises a diode D2 coupled to a grounded end of a voltage stabilizing capacitor, and the conducting direction of the diode D2 is from the voltage stabilizing capacitor toward the filter capacitor.

10. The slow start circuit with switch function according to claim 9, characterized in that: Voltage-dividing resistors R2 and R3 are further arranged between the diode D2 and the voltage-stabilizing capacitor; the voltage-dividing resistor R2 is connected in parallel above the diode D2; and the voltage-dividing resistor R3 is arranged below the coupling point between the voltage-stabilizing capacitor and the diode D2.

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