Patent ID: 7541749

Claim:
A current-mode resonant inverter circuit for a discharge lamp comprising: a step-up transformer including a primary winding and secondary winding, the secondary winding exhibiting a leakage inductance; a secondary side circuit connected to the secondary winding of the step-up transformer, the secondary side circuit including a capacitive component, which is connected in series between the secondary winding and an element connected to ground, the capacitive component exhibiting an auxiliary capacitance, the secondary side circuit being operably connected to the discharge lamp; current detecting means for detecting a phase of current flowing through the capacitive component in the secondary side circuit, the current detecting means comprising the element, which is connected in series between the capacitive component and ground; and switching means for determining a switching timing in response to an output from the current detecting means, the switching means driving the primary winding of the step-up transformer during operation of the current-mode resonant inverter circuit in causing a continuous discharge of the discharge lamp, wherein the capacitive component and the step-up transformer secondary winding are connected such that in combination the auxiliary resonance capacitance exhibit characteristics of a series resonant circuit, and the switching means drives the primary winding according to the switching timing so that an effective voltage applied to the primary winding coincides substantially in phase with the detected current and oscillates self-excitedly substantially at a resonance frequency of the series resonant circuit during the operation of the current-mode resonant inverter circuit.