Semiconductor light emitting element drive device and lighting fixture with the same

• US 8,729,827 B2
• Filed: 12/31/2012
• Issued: 05/20/2014
• Est. Priority Date: 02/13/2012
• Status: Expired due to Fees

• Current Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Esaki, Sana, Hiramatu, Akinori
• Primary Examiner(s): TRAN, ANH Q
• Application Number:
  US13/731,246
• Publication Number:
  US 20130207571A1
• Time in Patent Office: 505 Days
• Field of Search: None
• US Class Current: 315/297
• CPC Class Codes: H05B 45/10 Controlling the intensity of the light
• CPC Class Codes: H05B 45/327 Burst dimming
• CPC Class Codes: H05B 45/38 using boost topology
• CPC Class Codes: H05B 45/385 using flyback topology
• CPC Class Codes: H05B 47/10 Controlling the light source
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

A semiconductor light emitting element drive device includes: a converter circuit configured to supply a light source unit with a load current from a first-primary winding; and a current regulation circuit. The converter circuit further includes a second-secondary winding. The current regulation circuit includes a switching device (second switching device) connected in series with the second-secondary winding. In a dimming ratio of the light source unit is lower than a first ratio, the second switching device is controlled to ON and OFF so as to decrease the load current through the light source unit by a shunt of a part of the energy stored in the primary winding.

Claims

1. A semiconductor light emitting element drive device, comprising:

a direct-current power supply circuit configured to output direct-current power;

a converter circuit which has a transformer and a first switching device, said transformer having a primary winding and first- and second-secondary windings, said first- and second-secondary windings being same polarity with each other, and said first switching device being connected to said primary winding, wherein said converter circuit being configured to be input the power outputted from said direct-current power supply circuit and to supply a load current to a light source unit comprising light emitting elements from said first-secondary winding, said converter circuit being configured to control the load current by variably controlling an ON width of said first switching device;

a current regulation circuit which has a second switching device connected in series with said second-secondary winding, said current regulation circuit being configured to decrease an energy supplied to said first-secondary winding from said primary winding so as to decrease the load current supplied to said light source unit as the increase of an ON width of said second switching device; and

a control unit configured to control ON and OFF of said first and second switching devices,

wherein said control unit is configured,

(a-1) if increasing a dimming ratio of said light source unit in a range where the dimming ratio of said light source unit is higher than a first ratio, to increase the ON width of said first switching device with said second switching device kept off,

(a-2) if decreasing the dimming ratio of said light source unit in a range where the dimming ratio of said light source unit is higher than the first ratio, to decrease the ON width of said first switching device with said second switching device kept off, and

(b) in a range where the dimming ratio of said light source unit is lower than the first ratio, to regulate the ON width of said second switching device with the ON width of said first switching device held at a lower limit,

thereby controlling the dimming ratio of said light source unit.

2. The semiconductor light emitting element drive device as set forth in claim 1,

wherein said current regulation circuit comprises:

a series circuit, of an impedance component and a capacitor, connected in parallel with said light source unit;

a third switching device adapted to discharge said capacitor when said third switching device is turned on; and

an inductor placed along a discharge path of said capacitor,

wherein, in a range where the dimming ratio of said light source unit is lower than a second ratio, a pulse voltage, derived from an induced power of said inductor generated when said third switching device discharges said capacitor, is superposed on an output of said converter circuit.

3. The semiconductor light emitting element drive device as set forth in claim 1, wherein an ON and OFF frequency of said second switching device is set to a higher frequency than that corresponding to a video equipment'"'"'s shutter speed.

4. The semiconductor light emitting element drive device as set forth in claim 2, wherein an ON and OFF frequency of said third switching device is set to 120 Hz or more.

5. The semiconductor light emitting element drive device as set forth in claim 2,

wherein the second ratio is set to be smaller than the first ratio, and

said control unit is configured:

to keep said third switching device turned off in a range where the dimming ratio of said light source unit is higher than the second ratio; and

to control ON and OFF of said third switching device in a range where the dimming ratio of said light source unit is lower than the second ratio.

6. The semiconductor light emitting element drive device as set forth in claim 2,

wherein the second ratio is set to equal to the first ratio, and

said control unit is configured:

to keep said third switching device turned off in a range where the dimming ratio of said light source unit is higher than the second ratio; and

to control ON and OFF of said third switching device in a range where the dimming ratio of said light source unit is lower than the second ratio.

7. The semiconductor light emitting element drive device as set forth in claim 2, wherein said control unit comprises a microcomputer configured to control ON and OFF of at least one of said first to third switching devices based on a dimming signal from outside.

8. The semiconductor light emitting element drive device as set forth in claim 1,

wherein said transformer further has a third-secondary winding of a reversed polarity to said first-secondary winding, and

said semiconductor light emitting element drive device generates a drive power of said current regulation circuit by commutating and smoothing a voltage generated across said third-secondary winding.

9. A lighting fixture, comprising the semiconductor light emitting element drive device as set forth in claim 1,

wherein said lighting fixture comprises:

said light source unit which comprises light emitting elements and is adapted to be driven with said semiconductor light emitting element drive device; and

a fixture body in which said semiconductor light emitting element drive device and said light source unit are placed.