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Control of power converters having a parallel resonant commutation circuit

  • US 3,882,370 A
  • Filed: 11/15/1973
  • Issued: 05/06/1975
  • Est. Priority Date: 11/15/1973
  • Status: Expired due to Term
First Claim
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1. An efficient power converter for converting an input voltage to a different frequency output voltage comprising a power converter circuit having a plurality of controlled power devices that are sequentially rendered conductive at a variable frequency, a parallel resonant commutation circuit including commutating inductance means and parallel commutating capacitor means for supplying a variable amount of reactive power to render said controlled power devices nonconductive, and constant turn-off time control means for computing the timing of firing signals to provide an approximately constant turn-off time for said controlled power devices, to thereby adjust the operating frequency, wherein said constant turn-off time control means comprises sensing means for sensing selected instantaneous power circuit parameters and analog computation circuit means for cyclically and instantaneously deriving an output signal for timing said firing signals, said sensing means and computation circuit means being operative to produce said output signal when the predicted time to passage through zero of the voltage of said commutating capacitor means after the firing of each incoming controlled power device is approximately equal to a predetermined constant turn-off time for a corresponding outgoing controlled power device, and said sensing means and computation circuit means comprises at least one potential sensing device for sensing the instantaneous voltage of said commutating capacitor means and at least one current sensing device for sensing a plurality of instantaneous power circuit currents indicative of the commutating capacitor means current after the firing of each incoming controlled power device, a burden resistor coupled to the outputs of said current and potential sensing devices and forming an analog circuit which generates a control signal, and means for comparing said control signal with a reference voltage and producing said output signal.

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