一种低纹波高精度数控直流电流源的研制

Research of a Digitally Controlled DC Current Source with Low Ripple and High Precision

针对以往直流电流源普遍存在的精度低、调节范围窄和纹波电流较大等缺点,研制了一种基于ATmega64单片机的低纹波高精度数控直流电流源。该电流源通过设置使单片机产生两路大小相等、相位相差180°和分辨率为16位的PWM波,分别通过两路斩波与滤波稳流电路来减少纹波电流和增宽电流调节范围;采用16位A/D转换器来实现高精度的模数转换,并与单片机组成闭环反馈控制模式来进行稳流。测试结果表明,该电流源的输出电流调节范围为10～3 000 mA,步进电流为0.5 mA,纹波电流低于0.07 mA,具有矩阵按键设置预置电流、液晶显示电流和过流报警等功能。

A digitally controlled DC current source with low ripple and high precision based on ATmega64 is developed to overcome the drawbacks of the low-precision, small adjusting range and large ripple cur- rent commonly existed in the traditional DC current source. The Current source makes the microcontroller generate two PWM waves with the equal size, the phase difference 180° and 16-bit resolution. Then, the tipple current is reduced and the current adjustment range is widened by two choppers and the filter steady flow circuit respectively. The 16 -bit A/D converter is used to achieve the high-precision analog/digital conversion, which combines with a microcontroller to form the closed-loop feedback control mode for the stable current. The test results show that the output voltage range of the current source with the function of the matrix button to set the preset current, the LCD current and over-current alarm is 10 -3 000 mA, the step current is 0.5 mA, the ripple current is less than 0.07 mA.