Circuit for soft startup and soft shutdown

Abstract

The invention discloses a circuit for soft startup and soft shutdown. The circuit comprises a positive (P)-channel metallic oxide semiconductor field effect transistor (MOSFET), a negative (N)-channel metallic oxide semiconductor field effect transistor (MOSFET), an isolating component, an input input/output (I/O) port and an output I/O port, wherein the source of the P-channel MOSFET is connected with an external power supply; the grid of the P-channel MOSFET is connected with the external power supply through a first resistor; the drain of the P-channel MOSFET is connected with a system power supply; the source of the N-channel MOSFET is grounded; the grid of the N-channel MOSFET is grounded through a second resistor; the drain of the N-channel MOSFET is connected with the grid of the P-channel MOSFET; the first electrode of the isolating component is connected with the grid of the P-channel MOSFET; the second electrode of the isolating component is connected with the system power supply through a fourth resistor; the third electrode of the isolating component is grounded through a power button; the input I/O port is connected with the second electrode of the isolating component; and the output I/O port is connected with the grid of the N-channel MOSFET through a third resistor. The startup/shutdown control process of the circuit comprise the following steps of: detecting whether the input I/O port is in a low-level state or not; if the input I/O port is in a high-level state, finishing the process; and if the input I/O port is in the low-level state, setting the output I/O port in the high-level state or in the low-level state. Thereby, the circuit can ensure that power is cut off completely when a system is shut down and no standby current exists.

Description

technical field [0001] The invention relates to switch control of embedded system power supply, in particular to a soft switch circuit. Background technique [0002] In the prior art, there are two ways to realize system on / off: hard on / off and soft on / off. [0003] The system power is turned on or off by means of a hard switch. The advantage is that it is simple to implement and there is no standby current after shutdown; the disadvantage is that even when the microprocessor is processing key programs or key data, if the key is pressed, the system power It will also be shut down, which may easily cause loss of important data or damage to the system. [0004] In order to avoid the loss of important data or the damage of the system, the prior art usually adopts the mode of soft switch to control the power of the system to turn on or off. The advantage is that even after the shutdown, some circuits are powered on, and the standby operation is used to detect the power-on butto...

AI Technical Summary

Problems solved by technology

[0003] The system power is turned on or off by means of a hard switch. The advantage is that it is simple to implement and there is no standby current after shutdown; the disadvantage is that even when the microprocessor is processing key programs or key data, if the key is pressed, the system power It will also be shut down, which will easily cause loss of important data or damage to the system

[0004] In order to avoid the loss of important data or the damage of the system

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