Two-stage multichannel LED driver with CLL resonant circuit

Patent metadata

Field	Value
Publication number	US-9544956-B2
Application number	US-201514628372-A
Country	US
Kind code	B2
Filing date	Feb 23, 2015
Priority date	Apr 4, 2014
Publication date	Jan 10, 2017
Grant date	Jan 10, 2017

Abstract

In a two-stage power converter providing voltage regulation in a first stage, zero voltage switching (ZVS) is provided in switches in an unregulated, constant frequency second stage of a two-stage power converter by an inductor of a CLL resonant circuit connected in parallel with both a series connection of an external inductor and a primary winding of one or more transformers connected in series and an output of the switching circuit so that the output capacitances of the switches can be charged and discharged, respectively, by current in the parallel-connected inductor and independently of current in the magnetizing inductance of the transformer. Therefore, the magnetizing inductance of the transformer can be made sufficiently large to balance currents delivered to respective loads as is particularly desirable for driving a plurality of unbalanced LED strings independently of the value of the parallel-connected inductor which is desirably small.

First claim

We claim:

1. A power converter including
a first stage for regulating output voltage of said power converter from an input voltage in accordance with a sensed current, and
an unregulated second stage having
a switching circuit operating at a constant frequency for providing and interrupting said output voltage of said first stage to a primary winding of one or more transformers connected in series,
one or more rectifier circuits to provide an output from a secondary winding of each of said one or more transformers to at least two loads, and
a single resonant circuit including said one or more transformers, an external inductor connected in series with a primary winding of said one or more transformers connected in series and a capacitor, said transformer having a magnetizing inductance sufficient to substantially balance currents to said at least two loads
wherein said resonant circuit further includes a further inductor having terminals connected in parallel with said external inductor and said primary winding of said transformer wherein said resonant circuit is connected in parallel with said switching circuit, said further inductor having a value that is lower than a value of said magnetizing inductance of said transformer and provides zero voltage switching in said switching circuit such that the inductance value to provide zero voltage switching is decoupled from the magnetizing inductance value that provides substantial balancing of currents to said at least two loads.

2. The power converter as recited in claim 1 , wherein said rectifier circuit functions as a voltage doubler circuit to supply power to at least two loads.

3. The power converter as recited in claim 2 , further including a circuit to balance currents from said transformer secondary winding to said at least two loads.

4. The power converter as recited in claim 3 , wherein said circuit to balance currents comprises a connection of said secondary winding of said transformer to a reference voltage through a series-connected capacitor.

5. The power converter as recited in claim 1 , wherein said rectifier circuit includes a filter capacitor.

6. The power converter as recited in claim 1 , wherein said resonant circuit is a CLL circuit.

7. The power converter as recited in claim 1 , wherein said transformer and said rectifier circuit comprise a transformer module.

8. The power converter as recited in claim 7 , wherein said power converter includes more than one said transformer module, and wherein
primary windings of transformers of said more than one transformer modules are connected in series to an output of said resonant circuit.

9. The power converter as recited in claim 7 , wherein said transformer module further includes a load including a plurality of series-connected light emitting diodes.

10. The power converter as recited in claim 1 , wherein said second stage includes a current sensor for controlling an output voltage of said first stage.

Assignees

• Virginia Tech Intellectual Properties Inc

Inventors

• Chen Xuebing
• Huang Daocheng
• Li Qiang
• Lee Fred C

Classifications

• H05B33/0851

  Electricity · mapped topic

• H05B33/0815 Primary

  Electricity · mapped topic

• H05B45/10 Primary

  Controlling the intensity of the light · CPC title

• H05B45/375

  using buck topology · CPC title

• H05B45/39

  Circuits containing inverter bridges · CPC title