Abstract: An electronic circuit for providing a high voltage alternating current supply from a DC supply to an electroluminescent lamp. The circuit includes an inductive element and an output switching element arranged in series. The output switching element is operable to alternate, in use, between a first state and a second state, whereby in the first state a current path is provided through the inductive element and the output switching element, which current path is interrupted in the second state, such that when the output switching element changes from the first state to the second state, the inductive element generates a voltage at an output of the circuit for charging the electroluminescent lamp. The circuit includes an output diode arranged to prevent current flowing back from the output while the output switching element is in the first state.

Abstract: A high voltage AC power supply circuit for a capacitive load CL, such as an electroluminescent lamp, includes a low voltage DC supply, an inductor L and a FET S in series. The FET S can be pulsed so that the inductor L generates a voltage to charge the capacitive load CL via an H-bridge H, which is in parallel with the FET S. A diode D prevents current discharging from the capacitive load CL while the FET S is closed. The total capacitance downstream of the diode D and in parallel with the capacitive load CL is less than the capacitive load CL, so that when the polarity of the H-bridge is reversed, the voltage across the H-bridge collapses to earth and the capacitive load CL is discharged via the low voltage DC supply. The circuits which a employ a large smoothing capacitor in parallel with the H-bridge.

Abstract: A high voltage AC power supply circuit for a capacitive load CL, such as an electroluminescent lamp, includes an inductive component T and an output FET S1 in series. The output FET S1 can be pulsed so that the inductive component T generates a voltage to charge the capacitive load CL via an H-bridge H. A diode D1 prevents current discharging from the capacitive load CL while the output FET S1 Is closed. The circuit also includes a reservoir capacitor CR and a reservoir FET S3 in series with the inductive component T. The reservoir FET S3 can be pulsed so that the inductive component T generates a voltage to charge the reservoir capacitor CR by transferring energy from the capacitive load CL. A diode D2 Prevents current discharging from the reservoir capacitor CR while the reservoir FET S3 is closed. Energy can be transferred from the capacitive load CL to the reservoir capacitor CR and back again to reduce the amount of energy that must be discarded during operation of the circuit.