Based On Multiphase Boost Structure Of High-power Led Driver Chip Design

LED lighting as green lighting because of its high efficiency, high life expectancy, low pollution,etc, are being widely used in the display, backlight, lighting and other fields. In order to ensure the LED can work reliably and meet differenrt application requirements, you need to use the driver whose heart is the LED driver chip. So designing a high efficiency, low cost, compact LED driver chip is the basis of the wide range of LED applications.In high power white LED driver applications, high efficiency switching regulator and PWM dimming mode are currently used. However, this also introduces some issues, such as large output current ripple, high requirement for the transient response of converters, etc.In order to solve these problem, this paper designed a white LED driver chip used in multi-phase boost converter, this structure can effectively reduce the output current ripple and has faster transient response. This chip provides drive signal for three phase boost converter, where the drive signal is phase-shifted by120degree each other, which can reduce the output current ripple. In addition, The chip includes a dimming signal feedforward control, which can improve the transient response of the system when system works in the PWM dimming. Besides, the chip drives up to6LED strings and supports the PWM dimming function. the chip is targeted for large size monitor or car lighting application.The chip mainly includes three parts:the boost control loop, the current balance circuit and dimming circuit. The chip includes a high frequency oscillator which provides operating frequency for the boost control loop and current balance circuit. This chip includes the minimum turn-on time constraints, which can avoid the system mistakenly flipping result from the diode reverse current spikes, also includes a series of protective measures, such as soft-start protection, over-current protection, over-voltage protection, etc.The paper firstly introduces the basic idea of the multi-phase converters, and analyzes the design of the multi-phase boost converter from various angles, such as the stability, the transient response, protection measures and the selection of the capacitance and the inductor in multi-phase boost converter. Then it focuses on the principle of several modules of the chip, makes detailed theoretical analysis to all the analog parts and verifies the result through simulation. The modules which have been designed include voltage and current reference, voltage regulator, OSC and three-phase clock control circuit. Finally, the whole circuit is simulated in Hspice and the simulation results are analyzed. Through the whole simulation, we finds that the current ripple size dcreases while the current ripple frequency in the three-phase boost converter is increased to three times that of the single-phase converter. Besides, the transient response of the system has been improved significantly in the feedforward control.