Zero-current switching with LC resonant tank circuit and capacitor isolation DC-DC converter

Insulated DC-DC switching power supplies have been using a magnetic coupling method using a transformer for several decades. Transformers have excellent properties as a material that can change the voltage while insulating. On the other hand, it can be considered that there is a limit to the reduction in size and weight with increasing switching frequency. Therefore, we are interested in the insulation type converter by the capacitor coupling. The principle of the capacitor insulation method was introduced in 1994, but it was pointed out that the problem of noise that occurs when the power device is turned on and off. After that, a case where noise was suppressed by using a series resonant circuit of a capacitor and an inductor was reported. However, it had no means to control the output voltage, and had the problem that fluctuations in the input voltage would directly cause fluctuations in the output. Therefore, we maintain “resonance state” by providing “two sets of LC resonance tank circuits corresponding to the resonance frequency” and changing the operating frequency for ON width pulse of fixed width (pulse frequency modulation or pulse density modulation). We propose that the output voltage can be controlled while. The voltage control characteristics are analyzed using Spice Simulation, and the Co-relation with the experimental value is confirmed. By using frequency/density modulation, the inverter is always switched at the current zero crossing point, enabling Noiseless switching. Regarding the possibility, we will analyze the switching characteristics due to the deviation from the resonance point by using ADS; Electronic Design Automation tool, for the noise that may occur in the actual PCB (circuit pattern), and show the results.