At present, there are many types of DC/DC converters on the market, resonant converter is a type of DC/DC converter topology, by controlling the switching frequency to achieve a constant output voltage resonance circuit. Resonant converters are commonly used in high voltage applications to smooth waveforms, improve power factor, and reduce switching losses caused by high frequency power switches such as MOSFETs and IGBTs. It is important to note that the LLC circuit is usually used in resonant converters because it enables zero voltage switching (ZVS) and zero current switching (ZCS) in the operating range, supports higher switching frequencies, reduces the footprint of components, and reduces electromagnetic interference (EMI).
Schematic diagram of the resonant converter
A resonant converter is built on a resonant inverter that uses a network of switches to convert a DC input voltage into a square wave, which is then applied to a resonant circuit. As shown in Figure 2, the resonant circuit consists of a resonant capacitor Cr, a resonant inductor Lr and a magnetizing inductor Lm of the transformer in series. The LLC circuit filters out any higher-order harmonics by selectively absorbing the maximum power at a fixed square wave resonant frequency and releasing sinusoidal voltage through magnetic resonance. This AC waveform is amplified or reduced by a transformer, rectified, and then filtered to generate the converted DC output voltage.
Simplified LLC resonant DC/DC converter
The root mean square (RMS) current of the capacitor is one of the important parameters to be considered when selecting a suitable resonant capacitor Cr for a DC/DC converter. It affects capacitor reliability, voltage ripple, and the overall performance of the converter (depending on the topology of the resonant circuit). Heat dissipation is also affected by RMS current and other internal losses.
Polypropylene film dielectric
PCB mountable
Low ESR, Low ESL
High frequency
Post time: Sep-15-2023