Mature and easy to use battery-powered switching circuit diagram

One-piece inductor

Features:
1, support tact switch, self-locking switch
2, support external power supply automatically power on ( soldering on D17 can be achieved)
3, support standby constant current output
4. The external power supply and the lithium battery power supply are automatically switched. Due to the existence of the freewheeling diode in the PMOS, the voltage drop does not occur during the switching process.
5, through the double PMOS back to back connection, to prevent external power supply from pouring into the lithium battery

The schematic diagram is as follows, the power supply label description:
1, VCC_5V0 external power input
2, LI_BAT lithium battery
3, VCC_SYS main power output
4, VCC_SB standby power output

Control interface description:
1. EX_PWR_KEY switch button input, external tact switch or self-locking switch, active low.
2, PWR_KEY_DET switch button detection, for the microcontroller to detect the switch state, mainly suitable for the use of tact switches.
3, SYS_PWR_HOLD power supply, active high, useful when using a tact switch, or the system wants to control the shutdown itself

typical application:
1. The power switch uses the tact switch to control the SYS_PWR_HOLD by detecting the PWR_KEY_DET state, enabling a long press of xx seconds, the system is powered on, and the long press is xx seconds, and the system is shut down.
2, the vehicle equipment, D17 external ACC signal, to achieve car ignition, the device automatically starts, the car is turned off, after the delay xx time, automatically shut down.
3. Use the self-locking switch to disconnect D17. It does not need PWR_KEY_DET and SYS_PWR_HOLD to realize automatic switching between external power supply and built-in power supply, and small self-locking switch to control large current on and off.