LED light source

Patent metadata

Field	Value
Publication number	US-9357607-B2
Application number	US-201214124733-A
Country	US
Kind code	B2
Filing date	Jun 4, 2012
Priority date	Jun 10, 2011
Publication date	May 31, 2016
Grant date	May 31, 2016

Abstract

A LED light source comprises—a full bridge rectifier equipped with a first input terminal and a second input terminal for coupling to output terminals of the phase cut dimmer, —a series arrangement comprising N LED loads, a first and second end of said series arrangement being coupled to a first output terminal and a second output terminal of the full bridge rectifier respectively, —control means for during a period of the rectified AC supply voltage subsequently making the LED loads comprised in the first series arrangement carry a current, one by one and in dependency of the momentary amplitude of the rectified AC supply voltage when the momentary amplitude increases and for subsequently making the LED loads stop carrying a current, one by one, and in dependency of the momentary amplitude of the rectified AC supply voltage when the momentary amplitude decreases, said control means controlling the current through the LED loads at zero when the output voltage of the phase cut dimmer equals zero and controlling the current through the LED loads at a value that is independent from the phase angle of the phase cut dimmer when the output voltage of the phase cut dimmer differs from zero Volt. In order to make the LED light source compatible with a phase cut dimmer, the LED light source is further equipped with—a switchable bleeder current source coupled between the first and second output terminal of the full bridge rectifier, —a latch coupled between the first and second output terminals of the full rectifier bridge and comprising a series arrangement of a resistor and a capacitor to prevent the current through the dimmer from crossing zero after a leading edge generated by the phase cut dimmer, in case the phase cut dimmer is a leading edge phase cut dimmer, —a unidirectional element arranged in series with the capacitor for preventing discharging of the capacitor via the LED loads or the adjustable bleeder current source, and—a clamp circuit coupled to the capacitor and comprising a current source for discharging the capacitor and providing a low ohmic path for the dimmer current when the dimmer is off.

First claim

The invention claimed is:

1. A device, comprising:
a rectifier equipped with a first input terminal and a second input terminal for coupling to output terminals of a phase cut dimmer, supplying an AC supply voltage,
a series arrangement comprising N LED loads, a first and second end of said series arrangement being coupled to a first output terminal and a second output terminal of the rectifier respectively,
control means, comprising N current sources, each current source coupled between the cathode of a respective LED load and the second output terminal of the rectifier for during a period of the rectified AC supply voltage subsequently and sequentially making the LED loads comprised in the series arrangement carry a current, one by one and in dependency of the momentary amplitude of the rectified AC supply voltage when the momentary amplitude increases and for subsequently making the LED loads stop carrying a current, one by one, and in dependency of the momentary amplitude of the rectified AC supply voltage when the momentary amplitude decreases, said control means controlling the current through the LED loads at zero when the output voltage of the phase cut dimmer equals zero and controlling the current through the LED loads at a value that is independent from the phase angle of the phase cut dimmer when the output voltage of the phase cut dimmer differs from zero Volt, and
a switchable bleeder current source coupled between the first output terminal and second output terminal of the rectifier,

wherein:
a latch is coupled between the first and second output terminals of the rectifier and comprising a series arrangement comprising a resistor and a capacitor to prevent the current through the dimmer from crossing zero after a leading edge generated by the phase cut dimmer, in case the phase cut dimmer is a leading edge phase cut dimmer,
a unidirectional element is arranged in series with the capacitor, and
a clamp circuit is coupled to the capacitor and comprises a current source for discharging the capacitor and providing a low ohmic path for the dimmer current when the phase cut dimmer is off.

2. The device of claim 1 , wherein the switchable bleeder current source comprises a first series arrangement and a second series arrangement in parallel with the first series arrangement and coupled between output terminals of the rectifier, the first series arrangement comprising a first resistor and a first transistor and the second series arrangement comprising a second transistor and a second resistor and wherein a control electrode of the first transistor is connected to a terminal between the second transistor and the second resistor and a control electrode of the second transistor is connected to a terminal between the first transistor and the first resistor.

3. The device of claim 1 , wherein the control means comprises N control strings comprising a switchable current source and connecting the cathode of a LED load to the second output terminal of the rectifier.

4. The device of claim 3 ,
wherein each of the current sources comprises a first series arrangement comprising a first resistor and a first switching element and a second series arrangement, in parallel with the first series arrangement, of a second switching element and a second resistor,
wherein a control electrode of the first transistor is connected to a terminal between the second transistor and the second resistor and a control electrode of the second transistor is connected to a terminal between the first transistor and the first resistor, and
wherein a first end of each current source is coupled to the cathode of a LED load and a second end of the nth current source is coupled to a terminal between the second transistor and the second resistor of the (n−1)th current source for 2≦n≦N, and to terminal between the second transistor and the second resistor of the bleeder current source for n=1.

5. The device of claim 1 , further comprising
at least one LED light source that is not compatible with a phase cut dimmer.

6. The device of claim 1 , further comprising:
connection terminals for connecting one or more LED light sources, that are not compatible with a phase cut dimmer, in parallel to the device.

7. The device of claim 6 , wherein the one or more LED light sources are arranged that during operation there is no phase shift between an input voltage to the one or more LED light sources and an input current to the one or more LED light sources.

8. The device of claim 6 , wherein the control means comprises N control strings comprising a switchable current source and connecting the cathode of a LED load to the second output terminal of the rectifier.

9. A method for dimmed operation of a light emitting diode (LED) light source equipped with a series arrangement of N LED loads, the method comprising:
providing an AC supply voltage with frequency (f),
interrupting the supply voltage in each half period during an adjustable time lapse,
rectifying the interrupted AC supply voltage by means of a rectifier, and supplying the rectified interrupted AC voltage to the series arrangement comprising N LED loads,
during a period of the rectified interrupted AC supply voltage,
subsequently making the LED loads carry a current, one by one, in dependency of the momentary amplitude of the rectified AC supply voltage, when the momentary amplitude increases,
subsequently making the LED loads stop carrying a current, one by one, in dependency of the momentary amplitude of the AC supply voltage, when the momentary amplitude decreases, and
maintaining the LED loads in a non-conducting state during the interruptions of the AC supply voltage, during which the momentary amplitude of the rectified interrupted supply voltage is zero,
controlling the current through the LED loads at a value that is independent from the phase angle of the phase cut dimmer when the output voltage of the phase cut dimmer differs from zero Volt,
providing a switchable bleeder current source coupled between the first and second output terminal of the rectifier and maintaining a flow of current through the dimmer using the adjustable bleeder current source, when the amplitude of the rectified interrupted supply voltage is higher than zero Volt and the LED loads are not carrying a current,
providing a latch coupled between the first and second output terminal of the rectifier and comprising a series arrangement of a resistor and a capacitor and using the latch to prevent the current through the dimmer from crossing zero after a leading edge generated by the phase cut dimmer at the end of an interruption, in case the phase cut dimmer is a leading edge phase cut dimmer,
providing a unidirectional element arranged in series with the capacitor and with the resistor preventing discharging of the capacitor via the LED loads or the adjustable bleeder current source, and
providing a clamp circuit coupled to the capacitor and comprising a current source and discharging the capacitor using the clamp circuit and providing a low ohmic path for the dimmer current using the clamp circuit when the dimmer is off.

10. A device for supplying power to a non-dimmable light emitting diode (LED) light source, the device comprising:
a first input terminal and a second input terminal for connection to output terminals of a phase cut dimmer,
a rectifier equipped with rectifier input terminals connected to the first input terminal and the second input terminal,
wherein
a latch is coupled between output terminals of the rectifier, and the latch comprising a series arrangement of a resistor and a capacitor to prevent the dimmer current from crossing zero after a leading edge, in case the phase cut dim

Assignees

• Kahlman Henricus Marius Joseph Maria
• Kurt Ralph
• Koninkl Philips Nv

Inventors

• Kahlman Henricus Marius Joseph Maria
• Kurt Ralph

Classifications

• H05B45/48

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

• H05B47/10

  Controlling the light source · CPC title

• Y02B20/347

  Cross-Sectional Technologies · mapped topic

• H05B33/0815

  Electricity · mapped topic

• H05B33/083

  Electricity · mapped topic