Lnk306 constant current
AN37 shows a Lnk306 buck boost circuit with constant current but I want to add cc to a Lnk306 cv buck circuit to provide current limit during startup of a fan motor. Any info would be appreciated.
Comments
Hi, thanks for the reply which I understand, but I need to stop the LNK306 going into auto restart due to the fan motor inrush current. I assume that I can only do that if I can keep the start up current below the 306's inherent maximum by employing a current limit external to the chip.
Hello MobyUK,
You're right, if you want to avoid auto restart, using an external current limit circuit will do it. Also, if the extra power you need in order to go trough this start-up sequence is just a little bit higher tan your design, you can try to increase your output voltage and power your fan trough a small resistor.
Cheers,
PI_Crusher
Hello MobyUK,
Both versions you see on AN-37 (buck and buck-boost) are by default CV and CC. As long as the output current stays under the maximum output current (design choice) you have the circuit in CV mode (buck or buck-boost). Output power capability depends on respective output voltage and maximum current. If your output current goes to maximum, the circuit will not provide more power. Instead the voltage goes down because the chip will be in CC mode; any decrease of the output load Rout multiplied with Imax will force the output voltage to go down. The circuit offers over-heating and output short circuit protection.
Cheers,
PI_Crusher