Tapped single-stage buck converter LED driver

Patent metadata

Field	Value
Publication number	US-11233449-B2
Application number	US-201815906797-A
Country	US
Kind code	B2
Filing date	Feb 27, 2018
Priority date	Feb 27, 2018
Publication date	Jan 25, 2022
Grant date	Jan 25, 2022

Abstract

An apparatus is disclosed, comprising: a first light source having a first threshold voltage; a second light source having a second threshold voltage; a rectifier configured to receive an AC voltage as input and generate a DC voltage based on the AC voltage; a single-stage Buck converter section coupled to the rectifier, the first light source, and the second light source, the Buck converter section being configured to output a current generated based on the DC voltage towards the first light source and the second light source; and a switching circuit configured to reduce a load on the Buck converter section by periodically diverting the current away from the second light source when a magnitude of the AC voltage is less than or equal to a sum of the first threshold voltage and the second threshold voltage.

First claim

What is claimed is:

1. An integrated light emitting diode (LED) lighting system comprising:
an alternating current (AC) input;
a load circuit comprising:
at least a first plurality of LED devices coupled in parallel with a first capacitor and a second plurality of LED devices coupled in parallel with a second capacitor, the at least the first plurality of LED devices and the second plurality of LED devices being coupled together at a tap point, and
a diode coupled in series with at least the first and second capacitors on a first electrical path between the tap point and a first node;

a single stage buck converter circuit, electrically coupled between the AC input and the first plurality of LED devices, configured to provide a drive current to the load circuit; and
a switching circuit on a second electrical path between the tap point and a second node, the switching circuit comprising an input electrically coupled to a second location between the AC input and the single stage buck converter circuit to sense an instantaneous voltage of the sinusoidal input voltage and configured to close the second electrical path to divert the drive current away from the second plurality of LED devices along the second electrical path when the instantaneous voltage is less than a threshold voltage of the load circuit and to open the second electrical path when the instantaneous voltage is greater than the threshold voltage of the load circuit.

2. The system of claim 1 , wherein the switching circuit comprises a switch coupled to the tap point and a comparator coupled to the switch, and the comparator is configured to switch the switch to an on state to disconnect the second plurality of LED devices from the drive current in response to the instantaneous voltage dropping below the threshold voltage of the load circuit.

3. The system of claim 1 , further comprising a rectifier element coupled to the single stage buck converter circuit.

4. The system of claim 1 , wherein the threshold voltage of the load circuit equals a total threshold voltage of the first and second plurality of LED devices.

5. The system of claim 1 , wherein each of the first plurality of LED devices and the second plurality of LED devices comprises a plurality of LED devices electrically coupled together in at least one of in series and in parallel.

6. The system of claim 1 , wherein the switching circuit comprises a plurality of switching circuits, and the load circuit comprises a plurality of tap points and more than two pluralities of LED devices.

7. A method comprising:
receiving an alternating current (AC);
converting the AC to a direct current (DC) using a single stage buck converter circuit;
supplying the DC from the single stage buck converter circuit to a series string of a first plurality of LED devices and a second plurality of LED devices, the first plurality of LED devices and the second plurality of LED devices being coupled together at a tap point on a first electrical path; and
maintaining a switch, on a second electrical path between a tap point between the first plurality of LED devices and the second plurality of LED devices and a node, in an ON state to close the second electrical path and divert the DC current along the second electrical path to by-pass the second plurality of LED devices when a voltage level of the AC is below a threshold voltage of the first and second plurality of LED devices;
sensing an instantaneous voltage of the sinusoidal input voltage at a location between the AC input and the single stage buck converter circuit;
maintaining a switch in an OFF state to open the second electrical path when the instantaneous voltage is greater than the threshold voltage of the load circuit; and
supplying the second plurality of LEDs with a current from an alternate source when the DC current is diverted.

8. The method of claim 7 , wherein the diverting the DC current further comprises diverting the DC current on a condition that the instantaneous voltage is between a threshold voltage of the first plurality of LED devices and the threshold voltage of the series string of the first plurality of LED devices and the second plurality of LED devices.

9. The method of claim 7 , wherein the current from the alternate source is supplied by a capacitor.

10. The method of claim 7 , wherein the diverting the DC current does not short the first and second plurality of LED devices.

11. The system of claim 1 , wherein the threshold voltage of the load circuit is constant.

12. The method of claim 7 , wherein the threshold voltage is constant.

Assignees

• Lumileds Llc

Inventors

• Song Zhi Hua
• Soer Wouter

Classifications

• Y02B70/10

  Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes · CPC title

• H05B45/36

  Circuits for reducing or suppressing harmonics, ripples or electromagnetic interferences [EMI] · CPC title

• H05B45/355

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

• H02M1/44

  Circuits or arrangements for compensating for electromagnetic interference in converters or inverters · CPC title

• H02M1/0048

  Circuits or arrangements for reducing losses (using snubbers H02M1/34) · CPC title