Miniature High Voltage Capacitor Charging Power Module

In pulsed power applications, high voltage (HV) capacitors are employed for energy storage. This energy is transferred to load in a very short time typically nanosecond to microsecond. HV capacitor requires a power supply which can charge to a voltage level as per energy requirements. This power supply should be compact to accommodate in a limited available space and to be fed from onboard batteries. This paper presents a power supply which operates from a 12 V battery input and generates the output voltage of 4 kV. Generally for this application, flyback topology is suitable because of lower cost and less number of components. This paper discusses the design of power supply built around a commercially available controller LT3751 for capacitor charging application. The controller LT3751 is not only a fast charge transfer device but also a higher operating potential input device which can be effectively used in a flyback module. A high value capacitor can be charged at faster rate through this control device. This controller works in boundary conduction mode (BCM), while charging it reduces turn-on losses and improves the efficiency. Another important element is flyback transformer of the power supply, which also affects operation and overall efficiency of the system. Mainly, transformer parasitics play an important role in converter operation. The parasitics of transformer are reduced through employing stringent winding technique to control the secondary winding capacitances. Software simulation results are compared with experimental results of power module of 4 kV, 2 mA (size: 100 mm × 40 mm × 45 mm) and are in good agreement.