Voltage fed inverter for fluorescent lamps

A ballast for operating capacitively coupled parallel lamps each including a pair of electrodes, the ballast comprising:

• a high frequency resonant circuit, which generates a high frequency bus configured for operational coupling to the electrodes of each lamp;
• an inverter operationally coupled to the resonant circuit for inducing an AC current in the resonant circuit, the inverter circuit including:
• analogous first and second switches connected together at a common node to receive the oscillation signal generated by the resonant circuit, which oscillation signal determines a switching rate of the pair of switches,
• first and second driving inductors, each operationally connected between the common node and a control mode and being mutually coupled to the resonant circuit, and
• first and second secondary inductors, operationally connected serially to the control node and a corresponding first or second driving inductor, wherein each pair of first and second driving and secondary inductors cooperate to drive the analogous switches so that a square wave is generated at the common node;
• and
• a resistor starting network connected to receive an input from an input voltage source, which resistor starting network charges the inverter using the input voltage during an inverter start up.

A ballast for operating capacitively coupled parallel lamps, comprising:

• a resonant load circuit which generates a high frequency bus into which each lamp is operatively coupled through an associated ballasting capacitor and which includes a resonant inductance and a resonant capacitance which includes at least the ballasting capacitors;
• and
• an inverter circuit operationally coupled to the resonant load circuit for inducing an AC current in the resonant load circuit, the inverter circuit including:
• first and second switches serially connected between a positive and ground conductors, and being connected together at a common node through which the AC load current flows, the first and second switches each includes a control node and a common node, and
• gate drive circuitry which regeneratively controls the first and second switches, the circuitry including:
• first and second driving inductors mutually coupled to the resonant inductor to induce a voltage therein which is proportional to the instantaneous rate of change of the AC load current in the resonant load circuit, the driving inductors being connected between the common and control nodes,
• first and second secondary inductors, each serially connected to a respective first or second driving inductor and the control node,
• a tertiary inductor mutually coupled to the first and second secondary inductors, and
• a voltage clamp, connected in parallel to the tertiary inductor and secondary inductors, which voltage clamp clamps the voltage of the tertiary inductor and secondary inductors so that a preselected amount of current is supplied to the lamps.