The AP4341S from Diodes is an output voltage detector for primary side control systems. It is a low power loss solution. It detects the output voltage and provides a periodic signal when the output voltage is lower than a certain threshold.

The periodical signal can be coupled by the transformer to the primary side and provided as an awakening signal for the main primary side controller. By fast response to secondary side voltage, the AP4341S can effectively improve the transient performance of the primary side control system.

The AP4341S will enable a discharge circuit when it detects the output voltage is higher than a certain threshold. It is designed to operate with Diodes’ PSR ICs, such as AP3776 and AP3785, and is available in SOT23 package.