A new TRIAC dimmable LED driver control method achieves high-PF and quality-of-light

TRIAC dimmable LED driver senses the input phase or RMS voltage to determine the dimming current level. Most TRIAC dimmable LED drivers use bleeding circuits to help supply enough holding current in order to keep the TRIAC on. This usually adds extra power devices and control circuits to the bleeding circuit. This paper proposes a new dimming approach that allows the dimmer to turn off if the dimmer current drops below the holding threshold. The input capacitance is actively discharged by the boost circuit. The boost operation restores the input phase without keeping the TRIAC conduction. Therefore it avoids the multi-firing and dimmer turn-off inconsistency. Both the bleeding and holding functions are integrated into the boost circuit.