Patent ID: 7550933
Filing Date: 2009-06-23
Classification: H05B

Abstract:
1. An offline control circuit of LED driver to control a plurality of LEDs, comprising: a switching circuit generating a plurality of LED currents through a transformer to supply the LEDs; a voltage divider coupled to the LEDs and sensing a voltage across the LEDs for generating a voltage-feedback signal; a voltage-feedback circuit coupled to the voltage divider and sensing the voltage-feedback signal for generating a voltage loop signal; a current-feedback circuit coupled to the LEDs and sensing the LED currents for generating a current loop signal in accordance with a plurality of current-feedback signals of the LEDs, and in response to a maximum current of the LEDs, the current-feedback circuit comprises: a buffer circuit coupled to the voltage-feedback circuit and the current-feedback circuit, generating a feedback signal in accordance with the voltage loop signal and the current loop signal; wherein the feedback signal is coupled to the switching circuit to control a maximum voltage of the LEDs and the maximum current of the LEDs.