Overview: Customer Specific Device from ON Semiconductor DAP006 PWM Current−Mode Controller for Free Running Quasi−Resonant Operation The DAP006 bines a true current mode modulator and a demagnetization detector to ensure full borderline/ critical Conduction Mode in any load/line conditions and minimum drain voltage switching (Quasi−Resonant operation). Due to its inherent skip cycle capability, the controller enters burst mode as soon as the power demand falls below a predetermined level. As this happens at low peak current, no audible noise can be heard. An internal 5.0 ms timer prevents the free−run frequency to exceed the 150 kHz CISPR−22 EMI starting limit while the skip adjustment capability lets the user select the frequency at which the burst foldback takes place.
The Dynamic Self−Supply (DSS) drastically simplifies the transformer design in avoiding the use of an auxiliary winding. This feature is particularly useful in applications where the output voltage varies during operation (e.g. battery chargers). Due to its high−voltage technology, the IC is directly connected to the high−voltage DC rail. The DSS also offers a better overload trip point.
The transformer core reset detection is done through an auxiliary winding which, brought via a dedicated pin, also enables fast Over−Voltage Protection (OVP). Once an OVP has been detected, the IC permanently latches−off.
Finally, the continuous feedback signal monitoring implemented with an over−current fault protection circuitry (OCP) makes the final design rugged and reliable.
