低频正弦电流源广泛应用于接地网故障诊断、通信、雷达等领域。测试用激励源具有精度高、频率稳定、失真度小的特点。本文以接地网故障诊断用低频正弦电流源为应用背景，对线性电流源和开关电流源的基本原理、结构、特点进行了深入的研究，对各种正弦电流源的实现方案进行了比较。根据接地网故障诊断用低频正弦电流源具有频率低、频率稳定度高、输出电流大的特点，提出了由预调节开关电压源、开关直流电压源、线性直流正弦电流源、H电桥以及智能控制器组成的电路设计方案。H电桥起极性转换的作用；线性直流正弦电流源是系统的输出级，利用其输出纹波小、反应速度快的特点，提高正弦波输出精度；开关直流电压源是系统的中间级，作用是提供一个正弦全波整流波形式的电压，减小输出级调整管两端的电压差，提高整个系统的效率；预调节开关电压源是系统的输入级，它的作用是对输入电压进行预处理，保证中间级电源输出波形的调节灵敏度。LPC2138作为整个电源的智能控制器，主要完成负载电阻两端的电压测量、参考信号及PWM互补脉冲的生成，为预调节开关电压源、开关直流电压源、线性直流正弦电流源提供参考信号以及控制H电桥的工作状态。 根据设计方案完成了软件编程和电路硬件制作，并对整个系统进行了测试和分析。测试结果表明，电流源的技术参数完全满足接地网故障诊断用电流源的要求，验证了设计方案的可行性。

A low-frequency sine wave current source is widely used in fields of grounding grid fault diagnosis, communication, radar, etc. The source has many characteristics of higher output precision, stable frequency and low total harmonic distortion (THD). In this paper a low-frequency sine wave current source is designed for grounding grid fault diagnosis. The basic principles, structures and characteristics of linear current source and switching current source have been studied deeply; meanwhile, the implementation scheme of all kinds of sine wave current source has been compared as well. According to the low-frequency sine wave current source’s characteristics of low frequency, high frequency stability, and large output current in grounding grid fault diagnosis, the circuit design which consists of a pre-regulation switching voltage source, switching DC voltage source, linear DC sine wave current source, H-bridge and the intelligent controller is proposed. H-bridge can convert polarity. Linear DC sine wave current source is the output stage. By its small output ripple and fast response, the output accuracy of sine wave can be improved. The switching DC voltage source is the middle stage, which can provide the full-wave rectified sine wave voltage for output circuit to reduce the voltage difference of the output stage regulator transistor and improve the efficiency of the whole system. The pre-regulation switching voltage source is the input stage, which can pre-regulation input voltage to ensure adjustment sensitivity of the middle stage output waveform. LPC2138 is used as the intelligent controller of the power supply, which mainly completes voltage measurement of load resistance, generates low-frequency sine wave reference signals and PWM complementary pulses, provides reference signals for the pre-regulation switching voltage source, switching DC voltage source, linear DC sine wave current source, and controls the work stage of H bridge. According to the design scheme, the software programme and the hardware circuit are completed, and the entire system has been tested and analyzed. The test results show that the technical parameters of current source satisfy the requirements for grounding grid fault diagnosis completely, and verify the scheme’s feasibility.