LED light source with improved glow reduction

• US 9,967,935 B2
• Filed: 05/23/2016
• Issued: 05/08/2018
• Est. Priority Date: 06/04/2015
• Status: Active Grant

• Current Assignee: Signify Holding B.V. (Signify N.V.)
• Original Assignee: Philips Lighting Holding BV (Signify N.V.)
• Inventors: Hulshof, Fokko Jan Willem, Cornelissen, Wilhelmus Josephus
• Primary Examiner(s): Owens, Douglas W
• Assistant Examiner(s): Kaiser, Syed M
• Application Number:
  US15/161,370
• Publication Number:
  US 20160360588A1
• Time in Patent Office: 715 Days
• Field of Search: 315291, 315294, 315201, 315224, 315226, 315307
• CPC Class Codes: H05B 45/10 Controlling the intensity of the light
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: H05B 45/40 Details of LED load circuits
• CPC Class Codes: H05B 45/46 having LEDs disposed in parallel lines
• CPC Class Codes: H05B 45/48 having LEDs organised in strings and incorporating parallel shunting devices
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

The invention relates to a LED light source comprising:

• • input terminals for connection to a mains voltage supply source,
  • a rectifier coupled to the input terminals for rectifying the mains supply voltage supplied by the mains supply voltage source and comprising rectifier output terminals,
  • a DC-DC converter for generating a DC current out of the rectified mains supply voltage, comprising converter input terminals connected to the rectifier output terminals and comprising a first converter output terminal and a second converter output terminal,
  • a LED load with an anode coupled to the first converter output terminal via a first current control element for blocking a current flowing from the anode of the LED load to the first converter output terminal, and with a cathode coupled to the second converter output terminal via a first controllable switch having a control electrode coupled to first control circuitry for rendering the controllable switch non-conductive in case the LED light source is in standby mode, whereby the cathode of the LED load is coupled to the first controllable switch via a second current control element for blocking a current flowing from the first controllable switch.

Claims

1. A light emitting diode (LED) light source comprising:

input terminals for connection to a mains voltage supply source;

a rectifier coupled to the input terminals for rectifying the mains supply voltage supplied by the mains supply voltage source and comprising rectifier output terminals, a DC-DC converter for generating a DC current out of the rectified mains supply voltage, comprising converter input terminals connected to the rectifier output terminals and comprising a first converter output terminal and a second converter output terminal, a LED load comprising one or more LEDs and having an anode as its most positive node and a cathode as its most negative node;

a protective earth terminal;

the anode being coupled to the first converter output terminal via a first current control element for blocking a current flowing from the anode of the LED load to the first converter output terminal, and the cathode being coupled to the second converter output terminal via a first controllable switch having a control electrode coupled to first control circuitry for rendering the controllable switch non-conductive in case the LED light source is in standby mode, wherein the first controllable switch stores a charge, whereby the cathode of the LED load is coupled to the first controllable switch via a second current control element which blocks a current flowing from the stored charge of the first controllable switch from flowing to the cathode of the LED load, and

a capacitive element coupled between the protective earth terminal and a node coupling the first controllable switch and the second current control element.

2. The LED light source of claim 1, wherein the second current control element comprises a diode.

3. The LED light source of claim 1, wherein the first current control element comprises a diode.

4. The LED light source of claim 1, wherein at least the DC-DC converter is located on a first printed circuit board (PCB), the first current control element and/or the second current control element being located on said first PCB.

5. The LED light source of claim 1, wherein at least the LED load is located on a second PCB, the first control element and/or the second current control element being located on said second PCB.

6. The LED light source of claim 1, wherein the first and second current control elements are each selected to have a parasitic capacitance that is smaller than the parasitic capacitance across the first controllable switch.

11. The LED light source of claim 1, wherein at least the DC-DC converter is located on a first printed circuit board (PCB), the first current control element and/or the second current control element being located on said first PCB.

12. The LED light source of claim 1, wherein at least the LED load is located on a second PCB, the first control element and/or the second current control element being located on said second PCB.

7. A light emitting diode (LED) light source comprising:

input terminals for connection to a mains voltage supply source;

a rectifier coupled to the input terminals for rectifying the mains supply voltage supplied by the mains supply voltage source and comprising rectifier output terminals, a DC-DC converter for generating a DC current out of the rectified mains supply voltage, comprising converter input terminals connected to the rectifier output terminals and comprising a first converter output terminal and a second converter output terminal, a LED load comprising one or more LEDs and having an anode as its most positive node and a cathode as its most negative node;

the anode being coupled to the first converter output terminal via a first current control element for blocking a current flowing from the anode of the LED load to the first converter output terminal, and the cathode being coupled to the second converter output terminal via a first controllable switch having a control electrode coupled to first control circuitry for rendering the controllable switch non-conductive in case the LED light source is in standby mode, wherein the first controllable switch stores a charge, whereby the cathode of the LED load is coupled to the first controllable switch via a second current control element which blocks a current flowing from the stored charge of the first controllable switch from flowing to the cathode of the LED load;

wherein the first and second current control elements are each selected to have a parasitic capacitance that is smaller than the parasitic capacitance across the first controllable switch.

8. The LED light source of claim 7, wherein the second current control element comprises a diode.

9. The LED light source of claim 7, wherein the first current control element comprises a diode.

10. The LED light source of claim 7, wherein the LED light source is provided with a protective earth terminal, and a capacitive element is coupled between the protective earth terminal and a node coupling the first controllable switch and the second current control element.