Lamp driver circuit
First Claim
1. A lamp driver circuit for driving a lamp circuit with an AC squarewave voltage at a relatively high frequency, comprising:
- a self-oscillating half-bridge circuit having a pair of input terminals for connection across a DC voltage supply and a pair of output terminals for connection across a said lamp circuit including a lamp to be energized;
said bridge circuit including a pair of capacitors connected together in series across said input terminals and having a junction therebetween connected to a first one of said output terminals; and
said bridge circuit further including first and second transistor switching means connected together in series across said input terminals, a transformer having a single saturable core having first and second windings thereon respectively connected to said first and second switching means for alternately applying forward biasing base drive current to said first and second transistor switching means, thereby producing in said transistor switching means alternate conductive intervals, and a third winding on said core connected in series with the junction of said first and second transistor switching means and a second one of said output terminals for energization by current in a circuit between said junctions for supplying a squarewave voltage across said output terminals for driving said lamp circuit, and in which;
said forward biasing base drive current in each transistor switching means during each conductive interval thereof is terminated by saturation of said core in response to passage of a predetermined pulse of current through said third winding.
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Accused Products
Abstract
A lamp driver circuit is presented herein for driving a lamp circuit with an AC squarewave voltage at a relatively high frequency. The driver circuit includes a self-oscillating half-bridge circuit having a pair of input terminals connected across a DC voltage supply, which may be obtained from rectifying an AC voltage signal, and a pair of output terminals connected across a lamp circuit including a lamp, either a resistive lamp or a gaseous discharge lamp, to be energized. The circuit also includes a pair of capacitors connected together in series across the input terminals and having a junction therebetween connected to a first one of the output terminals. The bridge circuit also includes first and second switching transistors connected together in series across the input terminals. A transformer is provided having first and second windings thereon respectively connected to the first and second switching transistors for alternately applying forward biasing base drive current to the first and second transistors. A third winding on the transformer is connected in series from the junction of the two transistors to a second one of the output terminals for purposes of supplying a squarewave voltage across the output terminals for driving the lamp circuit. A starter circuit serves to start the half-bridge circuit by initially turning on one of the switching transistors in such a manner that while one transistor is being forward biased into conduction, the other transistor is reverse biased.
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Citations
16 Claims
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1. A lamp driver circuit for driving a lamp circuit with an AC squarewave voltage at a relatively high frequency, comprising:
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a self-oscillating half-bridge circuit having a pair of input terminals for connection across a DC voltage supply and a pair of output terminals for connection across a said lamp circuit including a lamp to be energized; said bridge circuit including a pair of capacitors connected together in series across said input terminals and having a junction therebetween connected to a first one of said output terminals; and said bridge circuit further including first and second transistor switching means connected together in series across said input terminals, a transformer having a single saturable core having first and second windings thereon respectively connected to said first and second switching means for alternately applying forward biasing base drive current to said first and second transistor switching means, thereby producing in said transistor switching means alternate conductive intervals, and a third winding on said core connected in series with the junction of said first and second transistor switching means and a second one of said output terminals for energization by current in a circuit between said junctions for supplying a squarewave voltage across said output terminals for driving said lamp circuit, and in which;
said forward biasing base drive current in each transistor switching means during each conductive interval thereof is terminated by saturation of said core in response to passage of a predetermined pulse of current through said third winding.
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2. A lamp driver circuit for driving a lamp circuit with an AC squarewave voltage at a relatively high frequency, comprising:
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a self-oscillating half-bridge circuit having a pair of input terminals for connection across a DC voltage supply and a pair of output terminals for connection across a said lamp circuit including a lamp to be energized; said bridge circuit including a pair of capacitors connected together in series across said input terminals and having a junction therebetween connected to a first one of said output terminals; and said bridge circuit further including first and second transistor switching means connected together in series across said input terminals, a transformer having a single saturable core having first and second windings thereon respectively connected to said first and second switching means for alternately applying forward biasing base drive current to said first and second transistor switching means, and a third winding on said core connected in series with the junction of said first and second transistor means and a second one of said output terminals for energization by current in a circuit between said junctions for supplying a squarewave voltage across said output terminals for driving said lamp circuit, said lamp driver circuit further including starter means for initially turning on one of said transistor switching means, including; (a) a third capacitor connected in a series charging circuit with said first winding across said input terminals so as to receive a charging current from said voltage supply; and (b) voltage breakdown trigger means connected across said series charging circuit and responsive to the charge voltage developed across said third capacitor attaining a given level causing said trigger means to breakdown from presenting a normal high impedance to presenting a low impedance to said third capacitor whereby said third capacitor discharges through said trigger means to cause a current pulse to flow through each of said first and second windings such that one of said transistor switching means is biased into conduction while the other is reverse biased. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A lamp driver circuit for driving a lamp circuit with an AC squarewave voltage, comprising:
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a self-oscillating half-bridge circuit having a pair of input terminals for connection across a DC voltage supply and a pair of output terminals for connection across a said lamp circuit including a lamp to be energized; said bridge circuit including a pair of capacitors connected together in series across said input terminals and having a junction therebetween connected to a first one of said output terminals; said bridge circuit further including first and second transistor switching means connected together in series across said input terminals, transformer means showing a first and second windings thereon respectively. connected to said first and second transistor switching means, for alternately applying forward biasing base drive current to said first and second transistor switching means, and a third winding connected in a series with the junctions of said first and second transistor switching means and a second one of said output terminals for energization by current in a circuit between said junctions for supplying a squarewave voltage across said output terminals for driving said lamp circuit; and starter means energized independently of said transformer means and including energy storage means and voltage breakdown trigger means effective upon breakdown to cause said energy storage means to discharge and thereby develop a starting pulse for initially turning on said bridge circuit in such a manner as to forward bias one of said transistor switching means into conduction while at the same time reverse biasing the other one of said transistor switching means.
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15. A lamp driver circuit for driving a lamp circuit with an AC squarewave voltage, comprising:
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a self-oscillating half-bridge circuit having a pair of input terminals for connection across a DC voltage supply and a pair of output terminals for connection across a said lamp circuit including a lamp to be energized; said bridge circuit including a pair of capacitors connected together in series across said input terminals and having a junction therebetween connected to a first one of said output terminals; said bridge circuit further including first and second transistor switching means connected together in series across said input terminals, transformer means having first and second windings thereon respectively connected to said first and second transistor switching means for alternately applying forward biasing drive current to said first and second transistor switching means, and a third winding connected in series with the junction of said first and second transistor switching means and a second one of said output terminals for energization by current in a circuit between said junctions for supplying a squarewave voltage across said output terminals for driving said lamp circuit; and starter means for initially turning on said bridge circuit in such a manner as to forward bias one of said transistor switching means into conduction while at the same time reserve biasing the other one of said transistor switching means, wherein said starter means includes; (a) a third capacitor connected in a series charging circuit with said first winding across said input terminals so as to receive a charging current from said voltage supply; and (b) voltage breakdown trigger means connected across said series charging circuit and responsive to the charge voltage developed across said third capacitor attaining a given level causing said trigger means to breakdown from presenting a normal high impedance to presenting a low impedance to said third capacitor whereby said third capacitor discharges through said trigger means to cause a current pulse to flow through each of said first and second windings such that one of said transistor switching means is biased into conduction while the other is reverse biased. - View Dependent Claims (16)
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Specification