Design Of Source Driving Control Circuit Applied To LED Driver Switching Power Supply

With the development of LED driver, low cost and low power consumption of the driving circuit becomes one of the major trends. An auxiliary winding has been eliminated in the source driving control and the structure is simple, it has advantages of low power on chips, low cost and low power consumption. However, due to some shortcomings of the conventional source driving control applied to LED driver such as low voltage power supply problems, excessive power loss of the main power MOS and general output current precision. A source driving control circuits applied to LED driver to solve problems mentioned before will be presented in this thesis.First, the principle of source driving control technology has been analyzed in this thesis. Secondly, the voltage on supply capacitor has not reached the required value after the control circuit begins to work at low input voltage. And the issues with the delay time control circuit of capacitor charging has been raised in this thesis. And a sampling circuit to directly detect the gate-source voltage of the main power MOS has been presented in this thesis to reduce the power loss of the main power MOS. In terms of constant output current, a constant output current control circuit which has input line voltage compensation to improve output current precision has been presented in this thesis. Finally, the test environment of driving circuit to verify the validity of proposed circuit based on the saber simulation software platform is set up in this thesis.Through the simulation and validation, a source driving control circuit used in LED driving has been designed in this thesis and it achieved charging delay control of supply capacitor at low input voltage. The whole input voltage range of 85V-265V, supply current of input line voltage<200uA, output constant current precision<±5%, the circuit meets the design requirements and is simple to implement, strong practicability.