Design of New Over-Temperature Protection Light-Emitting Diode Driver Circuit and Improvement Method of Visual Design

Abstract

The overall design of light-emitting diode (LED) display control system was completed at first. For the problems of LED driver chip such as low accuracy of constant current output, high power consumption, poor stability, and single over-temperature protection function, the double temperature hysteresis and over-temperature buffer protection function of circuit were designed. The low-power constant-current module of LED driver module included an operational amplifier, a MOS tube with negative feedback control, and the driving current required to achieve high-precision reference current conversion. The temperature control points were set in hysteretic and overtemperature buffer modules for the working temperature, and power MOS tube was turned off in time to reduce the driving current to a constant driving current, thus reducing the power consumption of circuit. In addition, to improve the image quality of LED display, a visual refresh logic circuit was designed. The display cycle was divided into 32 segments by logic circuit, with 128 gray clock cycles in each segment, and duty ratio was controlled by 12 bits of gray data. In test, the multi-value output bandgap reference voltage was simulated at first. In range of –30 °C–130 °C, the fluctuation of voltage in this temperature range met the requirements of circuit. During simulation of buffer circuit of the LED driver module, it was found that output terminal can perform good voltage following, so as to meet the needs of circuit. The design of visual refresh logic circuit can greatly improve the refresh rate of pulse width modulation (PWM).