Voltage Boosting using Modified Dickson Charge Pump VM Circuit

Abstract

I. INTRODUCTIONWith the increase in energy demand, the renewable energy systems have gained popularity in both residential and commercial areas. Thus dc-dc converters have attracted the attention of many due to its capability of enhancing the voltage level and its tendency to act as an interface between low input source and distribution DC bus systems[1]- [4]. Currently, telecom centers, data centers and micro grids are among the emerging examples of dc distribution system[5]- [7].It also finds its application in the HID lamps in automobiles, X-Ray power generators, Gas Discharge Tubes(GDT), UPS, etc., For achieving high voltage gains, conventional boost and buck-boost converters requires high duty ratios which results in high current stress in the switch thereby efficiency also reduces[8]- [11]. Due to the effect of power switches, rectifier diodes, and the equivalent series resistance of inductors and capacitors the step-up voltage gain is limited. Moreover, the extremely high duty-ratio operation will result in a serious reverse-recovery problem. Typically high-frequency transformers or coupled inductors are used to achieve high-voltage conversion ratios[12]- [18].But the transformer design is complicated and the leakage inductances increase for achieving larger gains, as it requires higher number of winding turns. This leads to voltage spikes across the switches and voltage clamping techniques are required to limit voltage stresses on the switches. Consequently, it makes the design more complicated. Villard voltage-doubler used to achieve high gain is a combination of the clamper and peak holder circuit [19]. It converts an input AC voltage to a doubled DC voltage across its output. Hence it requires an additional inverter to convert DC to AC which increases the complexity. One other method introduced by Cockcraft and Walton is a complex cascade voltage-doubler circuit which could produce a steady potential of about 700 kV which is about 3 times greater than the applied input voltage [20]. But it results in high coupling voltage drop due to the presence of series connected coupling capacitances which causes a small voltage gain for the circuit. To attain high-voltage conversion ratios, a new family of high-voltage-gain dc-dc power electronic converters that makes use of VM cells derived from Dickson charge pump circuit has been proposed [21]. The voltage rating of each VM cell capacitor is twice as that of its previous VM cell. Whenever even number of VM cells are used, the inductors (L , L ) and switches (S , S ) experience different current stresses whenever even number of VM cells are used.