LED LIGHT SOURCE WITH IMPROVED GLOW REDUCTION

• US 20160360588A1
• Filed: 05/23/2016
• Published: 12/08/2016
• 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
• Granted Patent: US 9,967,935 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• 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 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 (B),

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, 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 to the cathode of LED load.

2. A LED light source as claimed in claim 1, wherein the second current control element comprises a diode.

3. A LED light source as claimed in claim 1, wherein the first current control element comprises a diode.

4. A LED light source as claimed in claim 1, wherein the LED light source is provided with a protective earth terminal, and a predominantly capacitive element is coupled between the protective earth terminal and a node coupling the first controllable switch and the second current control element.

5. A LED light source as claimed in claim 1, wherein at least the DC-DC converter is located on a first PCB, the first current control element and/or the second current control element being located on said first PCB.

6. A LED light source as claimed in claim 3, 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 LED light source as claimed in 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.