| 摘要 |
PROBLEM TO BE SOLVED: To perform constant power control over a wide range of a voltage level when a voltage is supplied to an objective load. SOLUTION: When a voltage is supplied from an AC power supply to a lamp load 8, a first rectifying/smoothing circuit 1 creates a first DC voltage source (DC1) from the AC power supply, a switching element SW1 performs ON/OFF operation, and an inductor L1 creates a second DC voltage source (DC2) for supplying a voltage to the objective load by rectifying/smoothing the current. A voltage detecting circuit 5 and a current detecting circuit 6 detect the load voltage and the load current of the lamp load and the detection results are fed to a multiplier 4 where the product of the load voltage and the load current is produced (output from the multiplier). Output from the multiplier is controlled to have a specified constant level by performing ON/OFF control of the switching element through an amplifier 3, a photocoupler PC1 and a current mode PWM control circuit 2. COPYRIGHT: (C)2004,JPO&NCIPI
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