DC-AC converter with feedback signal control circuit utilizing power supply voltage, controller IC therefor, and electronic apparatus utilizing the DC-AC converter

摘要

An inverter controls the power supplied to a load such as a CCFL connected to a secondary winding of a transformer by means of pulse width modulation (PWM) control of the switches of a semiconductor switching circuit connected to the primary winding of the transformer. The current and voltage supplied to the load are fed back to the inverter in the form of a current error signal and a voltage error signal, respectively, from which a feedback signal is formed in accordance with the magnitudes of these signals. Thus, when the DC supply voltage of a DC power supply sharply rises, the inverter changes the feedback signal directly, that is, without waiting for the changes to occur in the load current and load voltage, so as to reduce the power supplied to the load. Thus, over-current and resultant viewer's discomfort is suppressed. Sudden shut down of the inverter are also prevented from occurring.