As in the question, there is a small system powered by a dc12v adapter. There are three strings of lithium batteries inside. The working current may reach 3~5A. The boost charging circuit is completed, but I want the system to be able to automatically switch to the external power supply when the 12V external power supply is connected. , I don’t know what circuit structure you all use? The more the better~~ I drew a circuit with IRF power MOSFET, and found that because there is a reverse diode in the MOSFET, it will cause a lot of problems. Unless you add a diode to prevent current backflow, the power consumption of the diode is too wasteful for the 3A current. , Consider whether the reverse withstand voltage of the MOSFET is replaced by a triode. There is no ideal plan yet, please feel free to enlighten me...
In addition, I don’t know if you have used JK flip-flops as a key switch circuit.
Alina ポストする August 4, 2020
Two MOS placed back to back
Kira ポストする August 4, 2020
Alison ポストする August 4, 2020
Controlled by a relay, very good.
Kira ポストする August 4, 2020
First of all, thank you, the single-pole double-throw relay can be switched. If the relay is used in a household ordinary circuit, it should be possible, with a simple structure and low cost. But the relay contact time is about milliseconds. During this period, the system is actually without power. If a capacitor is used, a large current system may also require a large volume. Furthermore, if the charging interface is plugged in and unplugged, it will cause frequent contact. Mechanical movements of the head are also inappropriate. Maybe I didn't make it clear that there are modules in this system that are sensitive to power failure protection.
