Boost and linear LED control

• US 9,119,262 B2
• Filed: 01/28/2015
• Issued: 08/25/2015
• Est. Priority Date: 08/24/2010
• Status: Active Grant

• Current Assignee: Signify Holding B.V. (Signify N.V.)
• Original Assignee: Koninklijke Philips N.V.
• Inventors: Melanson, John L., Draper, William
• Primary Examiner(s): VO, TUYET THI
• Application Number:
  US14/607,412
• Publication Number:
  US 20150145427A1
• Time in Patent Office: 209 Days
• Field of Search: 315/247, 315/291, 315307-326, 315/185.S, 315/224
• US Class Current: 1/1
• CPC Class Codes: H05B 41/28 using static converters
• CPC Class Codes: H05B 45/10 Controlling the intensity of the light
• CPC Class Codes: H05B 45/31 Phase-control circuits
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: H05B 45/38 using boost topology
• CPC Class Codes: H05B 45/397 Current mirror circuits
• CPC Class Codes: H05B 45/40 Details of LED load circuits
• CPC Class Codes: H05B 45/44 with an active control inside an LED matrix
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

A light emitting diode (LED) lighting system includes a switching power converter having an input for coupling to an alternating current (AC) power source, an output, and a switch. The LED lighting system also includes an LED lighting subsystem coupled to receive power from the output of the switching power converter. The LED lighting subsystem includes a current source for one or more LEDs, and the current source has a control node and a sense node. The LED lighting system additionally includes a switch state controller coupled to the switching power converter and coupled to the LED lighting subsystem. The switch state controller controls switching of the switch and varies a control current provided to the control node of the current source based on at least a parameter sensed from the sense node.

Claims

1. A light emitting diode (LED) lighting subsystem, comprising:

one or more LEDs;

a current source for the one or more LEDs, the current source including;

a transistor having a control input coupled to a constant voltage source, a first leg coupled to the one or more LEDs and a second leg; and

a current mirror coupled to the second leg of the transistor, the current mirror having a control node, a sense node indicative of an operating point of the LED lighting subsystem, and a transistor size ratio that determines an LED current provided to the one or more LEDs based on a control current received at the control node.

2. The LED lighting subsystem of claim 1, wherein the one or more LEDs include multiple parallel coupled strings of LEDs.

3. The LED lighting subsystem of claim 1, wherein the transistor is a NPN transistor.

4. An apparatus comprising:

lighting subsystem of claim 1;

a feedback circuit coupled to the sense node; and

a lighting system controller that supplies the control current to the control node of the current mirror.

5. The apparatus of claim 4, wherein the lighting system controller varies the control current provided to the control node based on an amount of dimming applied to the one or more LEDs by a phase-cut dimmer.

6. The apparatus of claim 4, wherein the switch state controller varies the control current provided to the control node to constrain current ripple in the one or more LEDs to no more than a predetermined amount.

7. A lighting system controller for a light emitting diode (LED) lighting system illuminating one or more LEDs from AC line voltage, wherein the lighting system controller receives a link voltage and a feedback signal indicative of an operating point of the LED lighting system, and responsive thereto, varies a control current provided to a current source that governs current through the one or more LEDs such that ripple in the one or more LEDs is no more than a predetermined amount.

8. The lighting system controller of claim 7, wherein the lighting system controller comprises an integrated circuit.

9. The lighting system controller of claim 7, wherein the lighting system controller further receives as an input a signal indicative of phase-cut dimming applied to the LED lighting system, and responsive thereto, varies the control current based on the signal indicative of phase-cut dimming.

10. The lighting system controller of claim 9, wherein the signal indicative of phase-cut dimming is a rectified input voltage of the LED lighting system.