| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide an LED power supply circuit which allows for switching to a control method that can minimize decrease of light by preventing the circuit loss from increasing when the driving voltage of an LED rises. <P>SOLUTION: The LED power supply circuit comprises: a power supply means 8; a voltage detection means (R<SB POS="POST">1</SB>, R<SB POS="POST">2</SB>); a current detection means (R<SB POS="POST">3</SB>); and a control circuit 12. The power supply means 8 has a conversion section for converting an input power P<SB POS="POST">1</SB>into a drive power P<SB POS="POST">2</SB>. The voltage detection means detects the driving voltage V<SB POS="POST">2</SB>to the LED, and the current detection means detects a driving current I2. Furthermore, an input power acquisition means 6 for acquiring the input power P<SB POS="POST">1</SB>value is provided. The control circuit 12 has a difference operation section for calculating the difference (P<SB POS="POST">1</SB>-P<SB POS="POST">2</SB>) between the input power P<SB POS="POST">1</SB>value and the product P<SB POS="POST">2</SB>of the driving voltage value and the driving current value. A constant loss control section for controlling the conversion rate of the conversion section so that the difference becomes constant, and a constant current control section for controlling the driving current I<SB POS="POST">2</SB>value to be constant are also provided, and switching is made to constant loss control when the driving voltage V<SB POS="POST">2</SB>value exceeds a reference voltage. <P>COPYRIGHT: (C)2013,JPO&INPIT</p> |
