LED drive circuit
AssigneeLite-On Technology Corporation
InventorsKenji Yamamoto, Akihiko Satokata
Life of this patent
Estimating the term…
Abstract
An LED drive circuit, wherein a circuit that drives light-emitting diode with a common connected cathode has a resistor connected to the anode of the light-emitting diode, an NPN-type transistor connected to the second terminal of the resistor that approximately determines the control current for the emission of light in cooperation with the resistor, an NPN-type transistor positioned in parallel with the resistor and connected to the anode of the light-emitting diode, and a current supply, a level shifter, and a switch for selectively changing the voltage between the base-emitter of the second transistor, which are placed between the base of transistor and resistor.
Claims8
A light-emitting diode (LED) drive circuit including a circuit that drives a light-emitting diode with a common connected cathode, said drive circuit comprising:
- a first resistor having a first terminal connected to an anode of said light-emitting diode;
- a first NPN-type transistor that has an emitter connected to a second terminal of said first resistor and that approximately determines a control current for emission of light in cooperation with said first resistor;
- a second NPN-type transistor positioned parallel with said first resistor element that has an emitter connected to said anode of said light-emitting diode;
- and
- a current supply, a level shifter, and a switch for selectively changing a voltage between a base-emitter of said second NPN-type transistor, that are positioned between a base of said second NPN-type transistor and said second terminal of said first resistor.
Dependencies are inferred from the claim text.