A Simplified Output Voltage Ripple Calculation Method of Intrinsically Safe Buck Converter with LC Low Pass Filter

Intrinsically safe Buck converter is an efficient DC-DC step-down switching circuit applied in flammable and explosive environment. The output voltage ripple (OVR) is an important electrical performance of the converter. It affected by switching frequency, filter inductance, capacitance, duty cycle, load resistance and other parameters. It is not easy to accurately calculate. The OVR calculation of the intrinsically safe Buck converter with LC low pass filter is more complicated compared with that of the traditional Buck converter. In this paper, an ideal circuit topology which is completely equivalent to the intrinsically safe Buck converter with LC low pass filter in continuous conduction mode (CCM) is constructed. By analyzing the frequency response of the equivalent circuit, the steady-state output characteristics of the circuit is obtained. Based on the voltage harmonic analysis, the OVR calculation method of the converter is obtained. Further ripple theoretical calculation and simulation analysis show that the fundamental ripple ratio can be equivalent to the total ripple ratio of the circuit completely and accurately in numerical computation. The final simulation results show that this method can effectively calculate the OVR of the intrinsically safe Buck converter with LC low pass filter.