To reduce power loss in a power supply when a supply voltage is generated for driving a backlight, for example in a liquid crystal display.
A main power-supply circuit and an inverter circuit (or DC-DC converter) are connected in parallel to an input-voltage generating means for rectifying and smoothing a commercial AC power supply. Then, the inverter circuit (or the DC-DC converter) includes an insulating transformer comprising a primary winding at a primary side not insulated to the commercial AC power supply and a secondary winding at a secondary side to input the DC input voltage at the primary side for power conversion and to attain the output voltage at the secondary side of the transformer. Accordingly, the total number of steps for power conversion is eliminated by one step as compared with conventional one to supply the power to the backlight connected to the inverter circuit (or the DC-DC converter), so that the power loss is reduced much more than the conventional one.
OYAMA YOSHIKI
SHIKAI NOBUHIKO
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Nobuo Suzuki
Hiroto Nakagawa