| 摘要 |
A light-emitting-diode-driving device includes a control circuit that is configured to perform constant current control with a DC-DC converter so that a value of a current detected by a current detection unit agrees with a prescribed reference current value to be supplied to a light source. The control circuit includes a reference-current-instruction unit, a threshold-voltage-setting unit, and a comparator circuit. The reference-current-instruction unit is configured to set the prescribed reference current value. The threshold-voltage-setting unit is configured to set a threshold voltage for determining a short circuit failure in the light source. The comparator circuit is configured to compare, with the threshold voltage, a value of a voltage that is detected by a voltage detection unit. The control circuit is configured to make the threshold-voltage-setting unit reduce the threshold voltage, when the reference-current-instruction unit reduces the prescribed reference current value. |
| 主权项 |
1. A light-emitting-diode-driving device, comprising:
a DC-DC converter configured to convert, into a prescribed DC voltage, a DC voltage that is supplied from a DC power supply, and apply the prescribed DC voltage to a light source including a light emitting diode; a current detection unit configured to detect a current that flows through the light source; and a control circuit configured to perform constant current control with the DC-DC converter so that a value of the current detected by the current detection unit agrees with a prescribed reference current value to be supplied to the light source, the control circuit comprising: a reference-current-instruction unit configured to set the prescribed reference current value to be supplied to the light source; a threshold-voltage-setting unit configured to set a threshold voltage for determining a short circuit failure in the light source; and a comparator circuit configured to compare, with the threshold voltage, a value of a voltage across the light source that is detected by a voltage detection unit, the control circuit being configured to make the threshold-voltage-setting unit reduce the threshold voltage, when the reference-current-instruction unit reduces the prescribed reference current value. |
