Patent ID: 8492982

Claim:
A current drive circuit configured to allow a maximum of eight channels of light emitting diode strings to be connected, and to drive the light emitting diode strings thus connected, the current drive circuit comprising: a control input terminal configured to receive a pulse width modulated dimming pulse signal; a standby terminal configured to receive a standby signal which is an instruction to switch the state of the current drive circuit between a standby state and an operating state; eight burst dimming terminals respectively provided to the channels, and each configured to receive a voltage that occurs at one terminal of the corresponding diode string; and a controller configured such that, when the voltage level of the standby signal is included in a first voltage range, the operating mode is set to an all channel common mode in which the light emitting diode strings of the respective channels are each driven using a corresponding driving current having the same phase, and when the voltage level of the standby signal is included in a second voltage range, the mode is set to a phase shift mode in which the light emitting diode strings of the respective channels are each driven using a corresponding driving current having a shifted phase, wherein the controller set to the phase shift mode performs a driving operation such that, when the electric potentials at the burst dimming terminals of the fifth through eighth channels are all lower than a predetermined second threshold voltage in a judgment period, the mode is set to a 90-degree phase shift mode in which the light emitting diode strings of the first through fourth channels are driven in a driving period after the judgment period using respective driving currents the phases of which are shifted from one another by ¼ the period of the dimming pulse signal, and, when the electric potentials at the burst dimming terminals of the seventh and eighth channels are all lower than the predetermined second threshold voltage in the judgment period, the mode is set to a 60-degree phase shift mode in which the light emitting diode strings of the first through sixth channels are driven in the driving period after the judgment period using respective driving currents the phases of which are shifted from one another by ⅙ the period of the dimming pulse signal, and, in cases other than the foregoing, the mode is set to a 45-degree phase shift mode in which the light emitting diode strings of the first through eighth channels are driven in the driving period after the judgment period using respective driving currents the phases of which are shifted from one another by ⅛ the period of the dimming pulse signal.