The ON Semiconductor NCP4354 is a secondary side SMPS controller designed for use in applications that require extremely low no-load power consumption. The device is capable of detecting 'no-load' conditions and entering the power supply into a low-consumption OFF mode. During OFF mode, the primary side controller is turned off and energy is provided by the output capacitors, thus eliminating the power consumption required to maintain regulation. During OFF mode, the output voltage relaxes and decreases to an adjustable level. Once more energy is required, the NCP4354 automatically restarts the primary side controller.
During normal power supply operation, the devices provide integrated voltage feedback regulation, replacing the need for a shunt regulator. The A versions include a current regulation loop in addition to voltage regulation. Feedback control as well as ON/OFF signal can be provided with only one optocoupler.
The NCP4354 includes a LED driver pin implemented with an open-drain MOSFET, driven by a 1 kHz square wave with a 12.5% duty cycle for indication purpose. The NCP4354 is available in SOIC-8 package.