Variable Off Time Controller

The NCP1215A is a controller for low power off-line flyback Switched Mode Power Supplies (SMPS) featuring low size, weight and cost constraints together with a good low standby power performance. The operating principle uses switching frequency reduction at light load by increasing the OFF Time. Also, when OFF Time expands, the peak current is gradually reduced down to approximately 1/4 of the maximum peak current to prevent from exciting the transformer mechanical resonances. The risk of acoustic noise is thus greatly diminished while keeping good standby power performance.