Patent ID: 7102299

Claim:
An electronic circuit for providing a high voltage alternating current supply from a DC supply to an electroluminescent lamp, wherein: the circuit comprises 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 comprises an output diode arranged to prevent current flowing back from the output while the output switching element is in the first state; the circuit further comprises a reservoir capacitor, a reservoir switching element in series with the inductive element, and a reservoir diode; the reservoir switching element is operable to alternate between a first state and a second state, whereby in the first state a current path is provided from the electroluminescent lamp through the inductive element and the reservoir switching element, which current path is interrupted in the second state, such that when the reservoir switching element changes from the first state to the second state the inductive element generates a voltage to charge the reservoir capacitor; and the reservoir diode is arranged to prevent current flowing back from the reservoir capacitor while the reservoir switching element is in the first state, whereby energy can be transferred from the electroluminescent lamp to the reservoir capacitor by means of the inductive element and the reservoir switching element, and energy can be transferred from the reservoir capacitor to the electroluminescent lamp by means of the inductive element and the output switching element; the circuit further comprising a supply selector arranged to selectively enable or disable supply of current from the DC supply, and which is arranged to disable supply of current in use when energy is being transferred from the electroluminescent lamp to the reservoir capacitor.