Circuit arrangement for equalizing waveforms of push-pull power supply

Claim 1

A circuit arrangement for generating two alternating sets of load-energizing pulses of equal power, comprising: two substantially identical transistors each having two main electrodes and a control electrode, one main electrode of each transistor being connected to a first terminal of a source of direct current having a second terminal connected by way of respective circuit branches to the other main electrode of each transistor, each of said circuit branches including a primary winding forming part of transformer means provided with at least one secondary winding for energizing a load; pulse-generating circuitry with a pair of output leads connected to the control electrodes of said transistors for respectively delivering thereto two interleaved trains of first and second driving pulses of substantially constant recurrence frequency and of a width less than a half-cycle of said recurrence frequency whereby said transistors alternately conduct and energize said primary windings fractions of respective half-cycles; sensing means for producing a pair of measuring variables respectively proportional to the mean current flow through said primary windings, said sensing means including two capacitors each connected in series with a respective resistor across at least part of one of said circuit branches; and comparison means with inputs connected to said capacitors for emitting on error signal representative in sign and magnitude to any difference between said measuring variables, said pulse-generating circuitry having a control input connected to said comparison means for varying the relative width of said first and second driving pulses in a sense tending to reduce said error signal to substantially zero, said pulse-generating circuitry including a square-wave oscillator having a control input connected to said comparison means for producing an unsymmetrical waveform in response to said error signal.