The paper presents a step-up controller that is used in WLED driver system and has two dimming modes:PWM dimming mode and Analog dimming mode.In the circuit

the introduction of large capacitor compensating network and the design of low voltage choose circuit effectively improve the circuit dimming performance.System simulation of the step-up controller is simulated in 0.5m-BCD process.The simulation results show that:The step-up controller can switch between zero load and rated load in PWM dimming mode

the switching time is less than 12s;Output voltage is adaptive to the dimming voltages in analog dimming mode

when the load is 6×6

6×8

6×10WLED array

the output stabilizes at 20.4V

27Vand 33.3V

and the LED current is set to 20mA.This design improves the WLED driver dimming performance

and thus enhances the quality of the LCD display.