用于原边反馈反激变换器的电压采样电路设计

Design of a voltage-sampling circuit used in PSR converter

设计了一种用于原边反馈反激变换器的电压采样电路,该电路利用一个具有正温度系数的电流去补偿输出整流二极管正向压降的负温度系数,以消除由二极管正向压降的温度系数导致的误差和系统的误操作,电路具有过零检测功能,能够检测次边二极管电流的过零位置,减小由二极管正向压降引起的误差。本电路采用0.5μm BiCMOS工艺,利用Hspice对电路进行仿真。结果表明,本电路能够有效抵消整流二极管80%的温度系数值并准确检测次边电流零点,提高采样精度。

A voltage sampling circuit used in primary side regulated （PSR） flyback converters was presented. A positive temperature coefficient （PTC） current was used to compensate the temperature coefficient of the output rectifier diode, which could eliminate the error and misoperation caused by the temperature coefficient of the diode. The circuit has zero cross detection（ZCD） function, which is used to detect the point when diode current reaches zero, so that the error caused by forward voltage drop of rectifier diode can be eliminated. This circuit was based on 0.5 ~tm BiCMOS process, circuit was simulated with Hspice. Simulation results show that the temperature coefficient is well counterbalanced by 80% and the cross zero point of the secondary side current is precisely detected, which can increase the sampling precision.