Wuhan UHV specializes in producing series resonant (also known as AC withstand voltage test device), and now we will share with you the current development of series resonant power supply.
Development of series resonantספק כוח
Early charging power sources used constant voltage DC charging, but their efficiency could not keep up with the design requirements. In order to achieve fast charging, power frequency resonance was developed, which linearly increased the voltage of the capacitor. However, the self-regulation ability of the current was too poor. With the change of load, the inductance and transformer volume under power frequency were large, and common mode interference was also serious, which could not achieve the required voltage accuracy and was inconvenient to carry. Therefore, inverter based circuits appeared. Although the weight and volume were reduced, the switching frequency of the thyristor was close to 10 Khz, and the triggering circuit of the thyristor was also very complex. With the development of electronic switching devices, semiconductors with high switching frequency and low conduction voltage drop have been widely used in charging power supplies. It can be seen that the power supply is developing towards high frequency direction.
Currently, many experts and manufacturers at home and abroad have conducted continuous research on series resonant chargers, and the research results mainly focus on the following aspects:
(1) Research on the Equivalent Circuit of Series Resonance
For series resonance with different resonance periods and equivalent circuits, one switching period is divided into six modes, and the resonance parameter values are obtained based on the calculation formulas of voltage and current. However, this is an ideal calculation formula, which only reduces the impact of transformer leakage inductance on the circuit. Due to the intervention of high-frequency transformers and rectifier silicon stacks, the influence of distributed capacitance must be considered. In fact, it has become a series parallel resonance circuit. Therefore, when designing high-frequency transformers, the distributed capacitance should be minimized as much as possible.
(2) Design of inductors in series resonant converters
The inductor in a series resonant converter is a high-frequency component, and ferrite cores are mostly used in design. The most commonly used is the EE type core. Although this method can also meet the requirements of the power supply, the magnetic flux density continues to increase during resonance, which can easily cause saturation of the core. From the perspective of reducing weight, it is not conducive to the lightweighting of the power supply.
