Project Description

The DC to DC Resonant Converter has many useful applications in practice with the most common one being the second stage in an uninterruptible power supply system or UPS. The goal of the design is to produce an extremely efficient, small, light weight, and cost effective DC to DC converter. These are some of the properties that are made possible by using a ZVT(Zero Voltage Transition) resonant type converter. The converter built in this project has 4 main stages.

The first is quite simply the AC to DC conversion to supply the input DC voltage to the unit itself. This was accomplished by using a 3-phase 208V input with variable control connected to a bridge rectifier and large filter capacitor giving a 0-150 VDC inout range.

The second is the control circuit which will supply the gate signals to the mosfets in the power circuit. The control circuit is responsible for supplying the gate signals at a certain frequency with correct phase shift and delay between all the signals. Proper operation of the control circuit is critical to prevent short circuiting of the input DC voltage. The third stage is the driver circuit. The gate to drain and gate to source junctions on the mosfets have relatively large capacitances that load down the gate signals from the control circuit instantaneously when switched very quickly. For that reason it is required that a current amplifier board be connected to the control circuit board to be able to supply the required current to the mosfet gates on the power board. The fourth and final stage of the project is the power board. The power board contains the four mosfets that are being turned on and off in a specific sequence by the control board. It also contains the series-parallel LCC type resonant converter. There is also an isolation transformer, bridge rectifier and output filter capacitor included on the power board.

This design was based around the following specifications:

V in 110Vdc to 130Vdc
V out 120Vdc
Power 500 Watts
Frequency 100 KHz