PWM controllers designed to eliminate no-load losses

The devices’ three operating modes enable the performance improvement. In normal mode, switching frequency is 65 or 100kHz; the controllers enter green mode, where frequency fold-back is used to back-off the frequency and raise average efficiency, for a mid-range load; and in conditions of no-load or a very light load, the devices enter a burst mode to minimise standby power.

A minimum switching frequency setting of 20kHz helps to minimise audible noise, while built-in frequency dithering (normal and green modes) reduces EMI emissions. The AP3125’s internal line compensation ensures output power limit is constant over the entire line voltage range.

The controllers’ improved internal slope compensation helps to simplify feedback loop design and enables more stable peak current control over a wide range of input voltage and load conditions. According to Diodes Incorporated, the controllers integrate a more complete range of protection functions than competing devices, including internal over-temperature, fast over-current, over-voltage and overload protection.

The AP3125B and AP3125HB variants also integrate brownout and line over-voltage protection, easily configured using a few divider resistors.

The AP3125 PWM controllers are available in an SOT26 package, priced from $0.20 each in 1,000 unit quantities.