Patent ID: 9596729
Date: 2017-03-14
CPC Classifications: H02M,H05B,Y02B

Claim:
1. A dimmable switching mode LED driving circuit without phase angle measurement, including: a dimmer circuit for performing a phase-cutting operation on an AC voltage to provide a phase-cut AC voltage in response to a dimming input; a bridge rectifier for providing an input voltage by performing a rectifying operation on the phase-cut AC voltage; an electromagnetic interference filtering and energy storing circuit, for providing a line voltage by performing a filtering and energy storing operation on the input voltage; a switching power converter for converting the line voltage to an output current for an LED load under a control of a driving voltage; and a control unit for receiving and processing at least one feedback signal from the switching power converter to determine an on time per switching cycle and generating the driving voltage; wherein the control unit includes an on-time controller for operating in a constant on-time mode to determine the on time according to the at least one feedback signal, the on-time controller including a voltage limiting circuit, a saw-tooth signal generator, and a comparison circuit, the voltage limiting circuit being used to set a limit on an on-time control voltage generated according to the at least one feedback signal and output a resultant on-time control voltage accordingly, the saw-tooth signal generator being used for generating a saw-tooth signal, and the comparison circuit being used for comparing the saw-tooth signal with the resultant on-time control voltage to determine the on time, and the on time having a maximum period when the resultant on-time control voltage is equal to the limit.