LED DRIVER CIRCUIT

摘要

An LED driver circuit capable of overcoming the issues in that a brightness change is perceived as a stepped change in a very low light amount region or light abruptly goes out by using PWM control and of realizing smooth dimming even at a very low amount of light is provided. In the LED driver circuit, a first circuit including a first resistor and a first power transistor connected in series and a second circuit including a second resistor and a second power transistor connected in series are connected in parallel with each other and are connected to an LED. First and second PWM signal generator circuits drive the first and second power transistors, respectively. When the first and second power transistors are in an on-state, currents flow through the LED via the first and second resistors, respectively, which enable a smooth brightness change even in a low illuminance region.

主权项

1. An LED driver circuit comprising:
at least one driver circuit connected to an LED, the at least one driver circuit including:
a plurality of current-limiting circuits for which currents that flow therethrough are certain current set values that are different from one another; anda plurality of pulse width modulation circuits, wherein the LED driver circuit is configured to mainly control a pulse width for a current-limiting circuit having a small current set value, among the plurality of current-limiting circuits, in a low light amount region and mainly control a pulse width for a current-limiting circuit having a large current set value, among the plurality of current-limiting circuits, in a high light amount region, whereby an amount of light of the LED is smoothly changed in a wider dynamic range than in a case of using a single driver circuit.