Patent ID: 7436378
Filing Date: 2008-10-14
Classification: H05B,Y02B

Abstract:
1. An LED-switching controller for applying a voltage necessary for driving a plurality of parallel-connected LEDs in a current control mode, said LED-switching controller comprising: a boosting circuit having an output voltage control function, capable of performing a controlled boosting operation for boosting a predetermined dc voltage to apply a voltage necessary for driving the plurality of LEDs in current control mode; an LED circuit with a plurality of parallel connected LEDs is coupled with an output terminal of the boosting circuit; an output voltage monitoring circuit for monitoring an output voltage of the boosting circuit, providing an output monitoring signal when the output voltage of the boosting circuit is increased to a predetermined maximum voltage; an LED terminal monitoring circuit that performs current control operation for controlling a current regulated by a constant-current, that confirms an LED connection operation for confirming the connection of the plurality of parallel connected LEDs; and that performs an LED specifying operation for specifying the LED to which a minimum voltage is applied; the LED terminal monitoring circuit confirms connection operation by determining a connection state of the LED of the plurality of parallel connected LEDs; the LED terminal monitoring circuit determines the connection state of the LED by determining if the output voltage of the boosting circuit is at the predetermined maximum voltage based on a receipt of the output monitoring signal and if the signal line voltage of the signal line to which the LED is coupled is higher than a reference voltage; if it is determined that any one of the output voltage of the boosting circuit is at the predetermined maximum and the signal line voltage of the signal line to which the LED is coupled is higher than the reference voltage, the LED is determined as connected by the LED terminal monitoring circuit; the LED terminal monitoring circuit further specifies the signal line that is connected to the LED that has the lowest signal line voltage among signal line voltages that are connected to the LEDs, excluding LEDs determined as not connected; an analog signal selecting circuit for providing a signal indicating the specified signal line with the lowest signal line voltage to the boosting circuit; and the constant-current circuit for driving the plurality of LEDs in the current control mode based on the boosting operations.