Multichannel constant current LED driving circuit, driving method and LED driving power

Patent metadata

Field	Value
Publication number	US-9699844-B2
Application number	US-201615176337-A
Country	US
Kind code	B2
Filing date	Jun 8, 2016
Priority date	Aug 7, 2014
Publication date	Jul 4, 2017
Grant date	Jul 4, 2017

Abstract

A multichannel constant current LED driving circuit can include: (i) a power stage circuit having a power switching transistor, an inductor, and a rectifier circuit, where the power stage circuit is configured to receive a DC bus voltage, and to generate a pseudo-constant output signal to drive a plurality of LED strings; (ii) a current control unit configured to control an average current of each of the plurality of LED strings in accordance with a corresponding one of a plurality of dimming signals; and (iii) the current control unit being configured to control the power switching transistor in accordance with a current feedback signal that represents a current flowing through the LED strings, where the plurality of LED strings are coupled in series to receive the pseudo-constant output signal.

First claim

What is claimed is:

1. A light-emitting diode (LED) driving circuit configured to drive an LED load having a plurality of LED strings coupled in series, the LED driving circuit comprising:
a) a power stage circuit configured to receive a DC bus voltage, and to generate an output signal to drive said plurality of LED strings;
b) a current control unit configured to control an average current of each of said plurality of LED strings in accordance with a corresponding one of a plurality of dimming signals; and
c) said current control unit being configured to control operation of said power stage circuit to control said output signal in accordance with a current feedback signal that represents a current flowing through said plurality of LED strings.

2. The LED driving circuit of claim 1 , wherein each of said plurality of dimming signals comprises a pulse-width modulation (PWM) control signal.

3. The LED driving circuit of claim 1 , further comprising a plurality of switching circuits, wherein each of said plurality of switching circuits is coupled in parallel to a corresponding one of said plurality of LED strings, and wherein each of said plurality of switching circuits is controlled to be on or off by said current control unit in accordance with a corresponding one of said plurality of dimming signals.

4. The LED driving circuit of claim 3 , wherein each of said plurality of switching circuits is controlled to be on in a transistor saturation region.

5. The LED driving circuit of claim 3 , wherein each of said plurality of LED strings has a same number of LEDs.

6. The LED driving circuit of claim 3 , wherein:
a) said switching circuit comprises a switching transistor having a first power terminal coupled to one terminal of said LED string, a second power terminal coupled to the other terminal of said LED string, and a control terminal coupled to said current control unit; and
b) on and off operation of said switching transistor is controlled by a corresponding one of said plurality of dimming signals.

7. The LED driving circuit of claim 1 , wherein said plurality of LED strings are coupled in series between outputs of said power stage circuit.

8. The LED driving circuit of claim 1 , wherein said current control unit is configured to control said power switching transistor in accordance with an error between said current feedback signal and a reference current signal.

9. The LED driving circuit of claim 3 , wherein each of said plurality of switching circuits comprises a controllable switch configured to be operated in a switching mode.

10. The LED driving circuit of claim 1 , further comprising a current sensing circuit coupled in series with said plurality of LED strings, and being configured to generate said current feedback signal.

11. The LED driving circuit of claim 1 , wherein said DC bus voltage is configured as a supply voltage of said current control unit.

12. The LED driving circuit of claim 8 , wherein said reference current signal is regulated in accordance with a pulse-width modulation (PWM) control signal that represents a luminance requirement of said LED load.

13. The LED driving circuit of claim 10 , wherein:
a) said power stage circuit comprises a power switching transistor, an inductor, and a rectifier circuit; and
b) said current sensing circuit, said plurality of LED strings, said inductor, and said power switching transistor are coupled in series between said DC bus voltage and ground.

14. The LED driving circuit of claim 13 , wherein said inductor operates in a continuous current mode.

15. A method of driving a plurality of light-emitting diode (LED) strings, the method comprising:
a) receiving a plurality of dimming signals that each corresponding to one of said plurality of LED strings;
b) controlling, by a current control unit, an average current flowing through each of said plurality of LED strings in accordance with a corresponding one of said plurality of dimming signals;
c) receiving a current feedback signal that represents an output current flowing through said plurality of LED strings; and
d) controlling, by a power stage circuit configured to receive a DC bus voltage, said output current to be pseudo-constant in accordance with said current feedback signal.

16. The method of claim 15 , further comprising determining said current feedback signal, by a current sensing circuit coupled in series with said plurality of LED strings, wherein a voltage signal across said current sensing circuit is configured as said current feedback signal.

17. The method of claim 15 , further comprising controlling said plurality of LED strings by a plurality of switching circuits that are controlled to be on or off by a corresponding one of said plurality of dimming signals.

18. The method of claim 15 , wherein each of said plurality dimming signals comprises a pulse-width modulation (PWM) control signal.

19. The method of claim 15 , further comprising:
a) determining a value of a reference current signal in accordance with a PWM control signal; and
b) controlling said power stage circuit in accordance with an error between said reference current signal and said current feedback signal.

20. An apparatus, comprising:
a) means for receiving a plurality of dimming signals that each corresponding to one of a plurality of light-emitting diode (LED) strings;
b) means for controlling, by a current control unit, an average current flowing through each of said plurality of LED strings in accordance with a corresponding of said plurality of dimming signals;
c) means for receiving a current feedback signal that represents an output current flowing through said plurality of LED strings; and
d) means for controlling, by a power stage circuit configured to receive a DC bus voltage, said output current to be pseudo-constant in accordance with said current feedback signal.

Assignees

• Silergy Semiconductor Technology Hangzhou Ltd

Inventors

• Xu Ligang
• Wang Jianxin
• Lai Hongbin

Classifications

• H05B45/48 Primary

  having LEDs organised in strings and incorporating parallel shunting devices · CPC title

• H05B45/10

  Controlling the intensity of the light · CPC title

• H05B45/00 Primary

  Circuit arrangements for operating light-emitting diodes [LED] · CPC title

• H05B33/0845

  Electricity · mapped topic

• H05B33/0851

  Electricity · mapped topic