Bi-directional AC-AC CUK converter

Discussion in 'The Projects Forum' started by Johnjacob1992, Feb 27, 2015.

  1. Johnjacob1992

    Thread Starter New Member

    Feb 27, 2015
    7
    0
    I am trying to build a specific AC-AC cuk converter for a project of mine. It involves the use of 4 MOSFETs configured in bi-directional switching states. I've included a picture of the schematic.[​IMG]

    I am essentially building a solid state 'electronic' variac(variable autotransformer). I input 80v AC 50Hz and I'd like to obtain AC voltages ranging from 0v to 80v at 50Hz, feeding and restrictive inductive load whilst being able to obtain an output current of up to 1A RMS.

    I found a solution for driving the MOSFETS in a patient by Simon Greenwood, and it had described a sequence as follows:

    "For a period during which input AC is positive and load current is in phase with load voltage. Transistor Q2 and transistor Q3 are held on and therefore, in conjunction with diode D2 and diode D3, provide bi-directional current paths. During this period transistors Q1 and Q4 switch alternately at high frequency in response to a high frequency control signal from the controller. For a 1st time interval of this high frequency alternation, transistor Q1 is off and transistor Q4 is on. During this interval diode D4 is forward biased and the energy transfer capacitors C1a and C1b charge through the choke inductor L1. During a second time interval of the high frequency alternation, the switching states of transistors Q1 and Q4 are reversed. Once this occurs, the energy transfer capacitors C1a and C1b discharge, driving current through the output load via inductance L2, and charging the output capacitor C2b. Circuit operation is repeated When transistor O1 is turned off and transistor O4 is turned on again. For a period during which input AC is positive and load current is in OUT of phase with load voltage, Transistor Q2 and transistor Q3 are held on. During this period transistors Q1 and Q4 switch alternately at high frequency, for a 1st time interval of this high frequency alternation, transistor Q4 is off and transistor Q1 is on. During this interval diode D1 is forward biased and the energy transfer capacitors C1a and C1b charge through the choke inductor L2. During a second time interval of the high frequency alternation, the switching states of transistors Q1 and Q4 are reversed. Once this occurs, the energy transfer capacitors discharge, driving current out through the input terminals.

    At negative AC and when load current is in phase With load voltage. Transistor Q1 and transistor Q4 are held on. During this period transistors Q2 and Q3 switch alternately at high frequency. For the 1st time interval of this high frequency alternation, transistor Q2 is off and transistor Q3 is on. During a second time interval, the switching states of transistors Q2 and Q3 are reversed. Charging the output capacitor C2b. Circuit operation is repeated when transistor Q2 is turned off and Q3 is turned on again. Finally, when AC is negative and load current is out of phase with load voltage. Transistor Q1 and transistor Q4 are held on this period transistors Q2 and Q3 switch alternately at high frequency. At the 1st interval, transistor Q3 is off and transistor Q2 is on. During a second time interval, the switching states of transistors Q2 and Q3 are reversed, driving current out through the input terminals via inductance L1, and charging the input capacitor C2a. Circuit operation is repeated When transistor Q3 is turned off and transistor Q2 is turned on again."

    My question is, how can I implement a simple way to drive the 4 MOSFETs in the bidirectional sequence described above?
     
Loading...