| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a driving device of a light emitting element which can maximally improve the consumption efficiency of a power source since margin voltage to a constant current circuit is not needed to be added to a reference voltage when a cathode terminal voltage of a light emitting element is monitored. <P>SOLUTION: The driving device has a charge pump circuit 2 boosting an input voltage VIN, a selecting circuit 3 selecting non-boosting, one-and-half-time boosting, or two-time boosting, the constant current circuit 4-1 including a field effect transistor M1, or the like, and drives a plurality of light emitting diodes LED1 to LEDn with a voltage V<SB>OUT</SB>output from the charge pump circuit 2, wherein a V<SB>GD</SB>monitoring circuit 12-1 which includes a field effect transistor M2 and a constant current source I1 and monitors a gate-drain voltage V<SB>GD1</SB>of the field effect transistor M1, or the like, are provided. The monitoring circuit 12-1, or the like, compares the V<SB>GD1</SB>of the M1 with a threshold voltage V<SB>TH2</SB>of the M2 to determine whether the selected boosting manner is changed. Consequently, the cathode terminal voltage can be monitored without being affected by manufacturing variance of a component in the constant current circuit or temperature characteristic variation. <P>COPYRIGHT: (C)2009,JPO&INPIT</p> |
