Please help me to divide this power supply and charging circuit

stm32f103vct6

Please help me to divide this power supply and charging circuit [Copy link]

Working Principle The input end of the D1 diode is a DC27V voltage, which is used to power a 24V 26AH battery through a BUCK circuit. The network label BAT is connected to the battery. At the same time, network number FG1 is also connected to the DC-DC which is stepped down to 12V and then to 5V to power the microcontroller. The conduction of Q1 in the BUCK circuit is controlled by the microcontroller (I have a question here. Since this circuit not only powers the battery but also steps down the voltage to power the microcontroller, and Q1 is controlled by the microcontroller, then when the power is just turned on, Q1 needs to be controlled by the microcontroller to turn on, and the microcontroller needs Q1 to turn on so that the microcontroller can work. Isn't this equivalent to a deadlock and no one can work? Supplement: The MCU must also be able to work when the battery is not connected.) Question 2: When the battery is reversely discharged, although the reverse of D9 will not affect the output of the switching power supply, because L2 D9 C27 exists, it is equivalent to this part of the circuit also having current. Does this matter? The U2 mos tube here works in a bidirectional conduction state.

maychang

"I have a question here. Since this circuit not only supplies power to the battery but also steps down the voltage to supply power to the microcontroller..." There is no power at the diode D1, but there is power at the battery BAT, so the microcontroller can work.

maychang

"When the battery is reversely discharged, although D9 is reversed, it will not affect the output of the switching power supply..." When the battery is discharged and the switching power supply is not working, there is no current in L2 and C27.

stm32f103vct6

maychang posted on 2018-1-19 16:27 "I have a question here. Since this road not only supplies power to the battery but also steps down the voltage to supply power to the microcontroller..." There is no power at the diode D1, but there is power at the battery BAT...

The problem is that it must be able to work even when the battery is not connected.

chunyang

This circuit must be connected to a battery.

chunyang

If you want to make it work properly without connecting the battery or power on first and then connect the battery, you can connect a capacitor between the gate of Q1 and the ground, and use a diode to connect a discharge circuit. In this way, after powering on, the gate of Q1 will not be pulled up immediately, and there will be a short conduction time. As long as the capacitor capacity is reasonably selected, the transient conduction can provide enough energy to start the MCU.

maychang

stm32f103vct6 posted on 2018-1-19 16:53 The problem is that it needs to work even when the battery is not connected.

"The problem is that it needs to work even when the battery is not connected." As far as your first post circuit is concerned, it is impossible.

wsdymg

If we only analyze the circuit posted by the OP, it will not work without a battery, unless your system has other backup power sources.

stm32f103vct6

chunyang posted on 2018-1-19 17:59 If you want to make it work normally without connecting the battery or power on first and then connect the battery, you can connect a capacitor between the gate and ground of Q1, and use a diode to bleed the discharge...

If this is done, it will affect the PWM modulation of the BUCK circuit.

chunyang

stm32f103vct6 posted on 2018-1-20 20:36 If this will affect the PWM modulation of the BUCK circuit.

There is nothing you can do about it, unless you don't use such a cheap circuit.

chunyang

Alternatively, adding another backup power system to the MCU system will also increase the cost.