In circuits for driving gas discharge lamp loads, such as fluorescent lamps, it is known to reduce the power from which the lamps are driven (so as to produce dimming of the lamps) by using a resonant inductor and capacitor in series with the lamps and by varying the circuit's operating frequency. In such a known circuit, when the operating frequency of the circuit is changed, current through the lamps is reduced and the lamps are correspondingly dimmed.
However, employing variation of the circuit's operating frequency in order to produce dimming renders the actual dimming level of the circuit susceptible to changes in the circuit's temperature which cause the circuit's operating frequency to change.