DIMMER COMPATIBLE LED DRIVING APPARATUS WITH ADJUSTABLE BLEEDING CURRENT

摘要

An LED driving apparatus includes a rectifier bridge generating a DC bus voltage, a bus capacitor coupled between the output terminal of the rectifier bridge and a reference ground, a voltage sensing circuit generating a voltage sensing signal indicative of the DC bus voltage, a bleeding circuit providing a bleeding current for the bus capacitor, a switching converter configured to convert the DC bus voltage into a driving signal to drive an LED, a dimming mode detector detecting whether the LED driving apparatus is coupled to a leading edge dimmer or a trailing edge dimmer based on the voltage sensing signal, and a bleeding control circuit generating a control signal to control the bleeding circuit based on the voltage sensing signal, the leading edge dimming mode signal and the trailing edge dimming mode signal.

主权项

1. A controller used in an LED driving apparatus, wherein the LED driving apparatus includes a rectifier bridge providing a DC bus voltage at an output terminal, a bus capacitor coupled between the output terminal of the rectifier bridge and a reference ground, a bleeding circuit configured to provide a bleeding current for the bus capacitor and a switching converter configured to convert the DC bus voltage into a driving signal to drive an LED, and wherein the controller comprises:
a dimming mode detector configured to receive a voltage sensing signal indicative of the DC bus voltage, wherein based on the voltage sensing signal, the dimming mode detector detects whether the LED driving apparatus is coupled to a leading edge dimmer or a trailing edge dimmer, and generates a leading edge dimming mode signal and a trailing edge dimming mode signal; and a bleeding control circuit coupled to the dimming mode detector, wherein based on the voltage sensing signal, the leading edge dimming mode signal and the trailing edge dimming mode signal, the bleeding control circuit generates a control signal to control the bleeding circuit; wherein if the LED driving apparatus is coupled to a leading edge dimmer, the bleeding circuit will provide a first bleeding current when the voltage sensing signal becomes smaller than a first threshold voltage; if the LED driving apparatus is coupled to a trailing edge dimmer, the bleeding circuit will provide a second bleeding current when the voltage sensing signal becomes smaller than a second threshold voltage.