How to keep the system from losing power by switching between two switches

stm32f103vct6

How to keep the system from losing power by switching between two switches [Copy link]

The system does not add large capacitors, and has two switching power supplies, one main and one backup. When one fails, it must immediately switch to the other and ensure that the system does not lose power. How to achieve it better? The diode method does not work, and requires both switching power supplies to work at the same time. Only one switching power supply can work at any time.

chunyang

The idea of the original poster is unrealistic. If you want a seamless connection, you must have hot backup or a sufficiently large short-term energy reserve (capacitor storage). Any switching power supply takes time from power-on to output stability.

maychang

The diode method does not work because it requires two switching power supplies to work at the same time. Only one switching power supply can work at any time. It takes a certain amount of time for any switching power supply to power up and output steadily. Therefore, "only one switching power supply can work at any time" is impossible.

stm32f103vct6

Is there no other way?

qwqwqw2088

How to explain the phrase "switching immediately"? Simple zero switching is not realistic. The power-off retention time of the power supply needs to be controlled. If the power switching power supply is large, you can consider using relays and contactors. The original poster can check a relay and two contactors, similar to the forward and reverse connection method of controlling the motor, one connected to the normally open contact and the other connected to the normally closed contact.

stm32f103vct6

qwqwqw2088 posted on 2018-5-10 15:04 What does it mean to switch immediately?,,, Pure zero switching is not realistic. The power-off retention time of the power supply needs to be controlled. If the power is large...

Moderator, do you mean to control the input or output of the switching power supply? Cold start or hot start? In the experiment, the input end of the switching power supply was controlled (the switching power supply outputs 30V, DC-DC to 12V). A 4700UF capacitor was used at 12V (the switching relay controlled by the MCU is 12V). The power stored in this capacitor is estimated to be enough to wait for the backup power supply to be seamlessly connected. However, the system also has to carry a load of nearly 10A, so it is impossible to increase the capacitance. Then the main switching power supply will lose power quickly, and if the cold start backup switching power supply is not powered on fast enough, the system will hiccup briefly.

qwqwqw2088

stm32f103vct6 posted on 2018-5-10 15:20 Moderator, do you mean to control the input or output of the switching power supply? Cold start or hot start? The experiment was done to control the input end of the switching power supply (switch power...

Suitable for switching AC control, the input end switches the DC output end and needs to design a control circuit. It is best to use MCU to judge the disconnection state

stm32f103vct6

qwqwqw2088 posted on 2018-5-10 15:28 Suitable for switching AC control, the input end switches the DC output end and needs to design a control circuit. It is best to use MCU to judge the disconnection state

Control the AC input end, the switching power supply startup time is too long. Time cannot guarantee the normal power supply of the system.

stm32f103vct6

stm32f103vct6 posted on 2018-5-10 16:19 Control the AC input end, the switching power supply startup time is too long. The time cannot guarantee the normal power supply of the system.

Oh, thank you