Power Electronics

IC Pair Exhibits Less Than 10 mW No-Load Input Power Consumption

ON Semiconductor's NCP1246 is a fixed-frequency current-mode controller featuring Dynamic Self-Supply. This function greatly simplifies the design of the auxiliary supply and the Vcc capacitor by activating the internal startup current source to supply the controller during start-up, transients, latch, stand-by etc. This device contains a special HV detector which detects the application unplug from the AC input line and triggers the X2 discharge current. The HV structure also includes brown-out detection circuitry.

The NCP1246 features a timer-based fault detection that ensures the detection of overload and an adjustable power compensation to help keep the maximum power independent of the input voltage. Due to frequency foldback, the controller exhibits excellent efficiency in light load condition while still achieving very low standby power consumption. Internal frequency jittering, ramp compensation, and a versatile latch input make this controller an excellent candidate for robust power supply designs.

A dedicated off mode allows the SMPS to reach extremely low no load input power consumption when combined with secondary side controller NCP4353 or NCP4354. When used together, the SMPS is capable of achieving <10 mW no load input power consumption. The secondary side controller signals the NCP1246 to enter a sleep mode, minimizing the power consumption of the control circuitry.

The NCP4353 and NCP4354 are secondary side SMPS controllers designed for use in applications which 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 is allowed to decrease to an adjustable level. Once more energy is required, the NCP4353 or 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 ONOFF 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 and the NCP4353 is available in TSOP-6.

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