Parallel-tuned electronic ballast with special output voltage waveform

  • US 5,736,819 A
  • Filed: 03/14/1995
  • Issued: 04/07/1998
  • Est. Priority Date: 03/20/1978
  • Status: Expired due to Term
First Claim
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1. An arrangement comprising:

  • a DC source functional to provide a DC supply voltage between a first and a second DC supply terminal;

    an inverter connected between the first and second DC supply terminals;

    the inverter being functional to cause a high-frequency AC inverter voltage to exist between a first and a second AC terminal;

    the high-frequency AC inverter voltage being of frequency several times higher than 60 Hz;

    any high-frequency AC voltage that might exist between the second AC terminal and one of the DC supply terminals being of very small magnitude compared with the magnitude of the high-frequency AC inverter voltage;

    the inverter being further characterized by including;

    (i) a first transistor having a first control input terminal, a first output terminal, and a first common terminal; and

    (ii) a second transistor having a second control input terminal, a second output terminal, and a second common terminal;

    the second output terminal being connected with the first common terminal, thereby to form a junction terminal;

    the junction terminal being connected with the first AC terminal in such manner that;

    (i) substantially no unidirectional voltage drop can exist between the junction terminal and the first AC terminal, and (ii) any alternating voltage existing between the junction terminal and the first AC terminal is of very small magnitude compared with the magnitude of the high-frequency AC inverter voltage;

    a unidirectional voltage existing between the second common terminal and the first output terminal;

    the average magnitude of the unidirectional voltage being substantially equal to that of the DC supply voltage;

    the inverter being additionally characterized by including a control circuit functional to cause the AC inverter voltage to consist of a continuous sequence of sinusoidally-shaped voltage pulses of alternating polarity;

    each such voltage pulse being separated from the next-following voltage pulse by a brief period during which the intantaneous magnitude of the AC inverter voltage undergoes a discontinuous change; and

    a gas discharge lamp connected in circuit with the AC output terminals.

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