LED DRIVE METHOD AND LED DRIVE DEVICE

摘要

An LED drive method drives an LED by a drive current. The LED drive method uses a voltage conversion unit, which includes a coil and a first switch, and converts an external voltage into a first voltage, which is a DC voltage, by controlling the first switch to be on in an on-pulse period of a first drive signal. A constant current drive unit is provided with the first voltage and generates a drive current based on a second drive signal.

主权项

1. An LED drive method that drives an LED by a drive current, the LED drive method using:
a voltage conversion unit which includes a coil and a first switch, and converts an external voltage into a first voltage which is a DC voltage by controlling the first switch to be on in an on-pulse period of a first drive signal; a constant current drive unit which is provided with the first voltage and which generates a drive current based on a second drive signal; and a control unit which includes a target voltage setting unit, and generates the first drive signal and the second drive signal, and the target voltage setting unit sets a target voltage representing a target of the drive current according to the light control information, wherein the control unit performs:
a first step of comparing a brightness based on the light control information and a predetermined reference brightness;a second step of generating the first drive signal based on an error between the first voltage and the target voltage;a third step of generating the second drive signal based on the light control information in a first case in which the brightness based on the light control information is higher than the predetermined reference brightness; anda fourth step of generating the second drive signal having a predetermined fixed on-pulse period in a second case in which the brightness based on the light control information is lower than the predetermined reference brightness, and wherein, in the fourth step, the control unit performs a fifth step of updating the target voltage based on the light control information in the second case.