Sansha Electric Manufacturing Company, Limited

Masataka Nishimura

Kenzo Danjo

Takashi Tsujii

Haruo Moriguchi

A power supply apparatus for a light source includes an input-side rectifier ( ) which converts an input AC signal to a DC signal, and a high-frequency inverter ( ) which converts the DC signal to a high-frequency signal. An output-side rectifier ( ) converts the high-frequency signal to a DC output signal for application to the light source. Power detecting means ( ) detects the power supplied to the light source through the application of the DC output signal thereto, and develops a power representative signal. A control circuit ( ), a summer ( ) and an error amplifier ( ) cooperate to control the high-frequency inverter ( ) in accordance with the power representative signal in such a manner that power of a predetermined value can be supplied to the light source. An input current detector ( ) detects the input AC signal current value and develops an input current representative signal. When the input current representative signal is smaller than a predetermined input current reference value, a summer ( ) and an error amplifier ( ) cooperate to provide the summer ( ) with such a control signal as to maintain the input AC signal current value at a predetermined value.

Power supply apparatus for light source

A power supply apparatus useful for starting and driving a discharge lamp includes a DC-to-DC converter for converting a DC signal from a DC power supply to a second DC signal having a predetermined magnitude which is supplied to the lamp. A current detector develops a DC current representative signal representing DC current supplied to the lamp from the DC-to-DC converter. A combination of the current detector a DC voltage detector and a multiplier develops a DC power representative signal representing DC power supplied from the DC-to-DC converter to the lamp. An error amplifier develops a DC current error signal representing the difference between the DC current representative signal and a predetermined DC current reference signal. An error amplifier develops a DC power error signal representing the difference between the DC power representative signal and a predetermined power reference signal. For a predetermined time period following the start of operation of the power supply apparatus, a combination of a delay circuit a comparator and a clamping diode clamps the DC power error signal so that only the DC current error signal can be outputted. A driver unit controls the DC-to-DC converter in such a manner as to make the DC current error signal zero.

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Osaka, Japan

Masataka Nishimura