Balancing transformers for ring balancer

• US 20050093472A1
• Filed: 10/05/2004
• Published: 05/05/2005
• Est. Priority Date: 10/06/2003
• Status: Active Grant

• Current Assignee: Polaris PowerLED Technologies, LLC (Microchip Technology Incorporated)
• Original Assignee: Microsemi Corporation (Microchip Technology Incorporated)
• Inventors: Jin, Xiaoping
• Granted Patent: US 7,294,971 B2
• Time in Patent Office: Days
• US Class Current: 315/177
• CPC Class Codes: H01F 30/12 Two-phase, three-phase or polyphase transformers
• CPC Class Codes: H01F 38/00 Adaptations of transformers or inductances for specific applications or functions
• CPC Class Codes: H05B 41/245 for a plurality of lamps
• CPC Class Codes: H05B 41/2822 using specially adapted components in the load circuit, e.g. feed-back transformers, piezoelectric transformers; using specially adapted load circuit configurations

Abstract

A ring balancer comprising a plurality of balancing transformers facilitates current sharing in a multi-lamp backlight system. The balancing transformers have respective primary windings separately coupled in series with designated lamps and have respective secondary windings coupled together in a closed loop. The secondary windings conduct a common current and the respective primary windings conduct proportional currents to balance currents among the lamps. The ring balancer facilitates automatic lamp striking and the lamps can be advantageously driven by a common voltage source.

Claims

1. A balancer for current sharing among multiple loads in a parallel configuration, the balancer comprising a plurality of balancing transformers, each of the balancing transformers designated for a particular load, and each of the balancing transformers comprising a magnetic core, a primary winding to be inserted in series with its designated load, and a secondary winding, wherein the secondary windings of the balancer are serially coupled in a closed loop to conduct a common current.

2. The balancer of claim 1, wherein the magnetic core has a toroidal shape, and the primary winding and the secondary winding are wound progressively on separate sections of the magnetic core.

3. The balancer of claim 1, wherein the magnetic core has a toroidal shape, and a single insulated wire goes through inner holes of the magnetic cores in the balancer to form the closed loop secondary windings.

4. The balancer of claim 1, wherein the magnetic core is based on an E structure, and the primary winding and the secondary winding are wound on separate sections of a bobbin.

5. The balancer of claim 1, wherein the magnetic core has high relative permeability with an initial relative permeability greater than 5,000.

6. The balancer of claim 1, wherein the plurality of balancing transformers has substantially identical turns ratios.

7. The balancer of claim 1, wherein the plurality of balancing transformers has different turns ratios.

8. The balancer of claim 1, wherein polarity of the secondary windings is aligned so that voltages induced in the secondary windings are in phase and add up together in the closed loop.

9. A method to control current ratios among multiple parallel loads, the method comprising the steps of:

providing a balancing transformer for each load;

coupling each load in series with a primary winding of the corresponding balancing transformer; and

coupling secondary windings of the balancing transformers in a serial loop to conduct a common current.

10. The method of claim 9, wherein the balancing transformers have substantially identical turns ratios to force the multiple loads to conduct substantially equal currents.

11. The method of claim 9, wherein the balancing transformers have different turns ratios to allow the multiple loads to conduct currents with predetermined ratios.

12. The method of claim 9, wherein polarity of the secondary windings is aligned so that voltages induced in the secondary windings are in phase when alternating current voltages applied to the corresponding primary windings are in the same phase.

13. A method to produce a ring balancer, the method comprising the acts of:

providing a plurality of toroidal magnetic cores to correspond to a plurality of balancing transformers;

winding an insulated wire progressively on a section of each toroidal magnetic core to correspond to primary windings for the respective balancing transformers, wherein each of the primary windings is coupled to a separate load for current balancing; and

looping an insulated wire through the plurality of toroidal magnetic cores to correspond to secondary windings connected in a closed loop.

14. The method of claim 13, wherein the secondary windings comprise a single turn of the insulated wire.

15. A ring balancer comprising means for passively controlling current ratios of multiple parallel loads using a plurality of transformers with respective secondary windings connected in a short circuit loop and respective primary windings individually coupled to different loads.

16. The ring balancer of claim 15, wherein each of the secondary windings has ten or less turns.