Apparatus and methods of operation of passive LED lighting equipment

Patent metadata

Field	Value
Publication number	US-9717120-B2
Application number	US-58262009-A
Country	US
Kind code	B2
Filing date	Oct 20, 2009
Priority date	Apr 24, 2009
Publication date	Jul 25, 2017
Grant date	Jul 25, 2017

Abstract

This invention is concerned with the control and design of a LED lighting system that does not need electrolytic capacitors in the entire system and can generate light output with reduced luminous flux fluctuation. The proposal is particularly suitable, but not restricted to, off-line applications in which the lighting system is powered by the ac mains. By eliminating electrolytic capacitors which have a limited lifetime of typically 15000 hours, the proposed system can be developed with passive and robust electrical components such as inductor and diode circuits, and it features long lifetime, low maintenance cost, robustness against extreme temperature variations and good power factor. No extra electronic control board is needed for the proposed passive circuits, which can become dimmable systems if the ac input voltage can be adjusted by external means.

First claim

The invention claimed is:

1. A passive lighting circuit comprising
a variable input inductor for receiving an AC input power, the variable input inductor being arranged to filter the AC input power, limit a power flow into an LED load having at least one LED, reduce the sensitivity of LED power to fluctuations in the AC input power, and be selectively controlled for dimming the at least one LED;
a rectification circuit connected directly with an output of the variable input inductor, the rectification circuit being arranged to receive the filtered AC input power from the input inductor, rectify the AC input power, and generate a rectified DC power;
a non-electrolytic capacitor connected across an output of the rectification circuit for reducing a voltage ripple of said rectified DC power;
a current ripple reduction circuit formed by an inductor connected directly between the non-electrolytic capacitor and the LED load, the current ripple reduction circuit being arranged to generate a current to be provided to the LED load;
the LED load with at least one LED for receiving said current as an input;
wherein the current supplied to said at least one LED is a continuous direct current that is permitted to vary periodically between a non-zero maximum value and a non-zero minimum value, and wherein the operating and/or design parameters of said at least one LED are chosen such that the variation in luminous flux resulting from the variation in the continuous direct current is not observable to the human eye; and
wherein the passive LED lighting circuit that is free of active electronic switches, electronic control circuits for the switches, power supplies for the electronic control circuits, and electrolytic capacitors.

2. The passive LED lighting circuit of claim 1 , further comprises a valley-fill circuit located between said rectification circuit and said non-electrolytic capacitor, wherein the non-electrolytic capacitor is connected across an output of the valley-fill circuit.

3. The passive LED lighting circuit of claim 2 , wherein said valley-fill circuit comprises a first capacitor and a second capacitor.

4. The passive LED lighting circuit of claim 3 , wherein the first and second capacitors have the same capacitance.

5. The passive LED lighting circuit of claim 3 , wherein the first and second capacitors have different capacitances.

6. The passive LED lighting circuit of claim 2 , wherein said valley-fill circuit includes a voltage-doubler.

7. The passive LED lighting circuit of claim 2 , wherein said valley-fill circuit comprises more than two capacitors.

8. A passive LED driver circuit comprising:
a variable input inductor for receiving an AC input power, the variable input inductor being arranged to:
filter the AC input power;
limit a power flow into an LED load having at least one LED;
reduce the sensitivity of LED power to fluctuations in the AC input power; and
be selectively controlled for dimming the at least one LED;

a rectification circuit connected directly with an output of the variable input inductor, the rectification circuit being arranged to receive the filtered AC input power from the input inductor, rectify the AC input power, and generate a rectified DC power;
a non-electrolytic capacitor connected across an output of the rectification circuit for reducing a voltage ripple of said rectified DC power;
a current ripple reduction circuit formed by an inductor connected directly between the non-electrolytic capacitor and the LED load, the current ripple reduction circuit being arranged to generate a current to be provided to the LED load;
wherein the current supplied to said at least one LED is a continuous direct current that is permitted to vary periodically between a non-zero maximum value and a non-zero minimum value, and wherein the operating and/or design parameters of said at least one LED are chosen such that the variation in luminous flux resulting from the variation in the continuous direct current is not observable to the human eye; and
wherein the passive LED driver circuit that is free of active electronic switches, electronic control circuits for the switches, power supplies for the electronic control circuits, and electrolytic capacitors.

Assignees

• Hui Ron Shu Yuen
• Chen Wu
• Univ City Hong Kong

Inventors

• Hui Ron Shu Yuen
• Chen Wu

Classifications

• H05B33/0809 Primary

  Electricity · mapped topic

• Y02B20/342

  Cross-Sectional Technologies · mapped topic

• H05B45/355 Primary

  Power factor correction [PFC]; Reactive power compensation · CPC title

• H05B45/375

  using buck topology · CPC title

• Y02B20/30

  Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED] · CPC title