LIGHTING DEVICE FOR SOLID-STATE LIGHT SOURCE AND ILLUMINATION APPARATUS USING SAME

• US 20120286686A1
• Filed: 04/26/2012
• Published: 11/15/2012
• Est. Priority Date: 05/12/2011
• Status: Active Grant

• Current Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: WATANABE, Koji, Mizukawa, Hiromitsu
• Granted Patent: US 8,716,949 B2
• Time in Patent Office: Days
• US Class Current: 315/224
• CPC Class Codes: H05B 45/14 using electrical feedback from LEDs or from LED modules
• CPC Class Codes: H05B 45/327 Burst dimming
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: H05B 45/375 using buck topology
• CPC Class Codes: H05B 45/38 using boost topology
• CPC Class Codes: H05B 45/385 using flyback topology
• CPC Class Codes: H05B 45/39 Circuits containing inverter bridges

Abstract

A lighting device for lighting a solid-state light source includes: a DC power circuit unit for converting a power of an input DC power source using a switching element and flowing a current through a solid-state light source; and a control unit for performing a first switching control in which the switching element is turned on/off at a first high frequency and a second switching control in which an ON/OFF operation of the switching element is intermittently stopped at a second frequency lower than the first frequency of the first switching control. When the current flowing through the solid-state light source is changed, the second frequency is varied.

Claims

1. A lighting device for lighting a solid-state light source, comprising:

a DC power circuit unit for converting a power of an input DC power source using a switching element and flowing a current through a solid-state light source; and

a control unit for performing a first switching control in which the switching element is turned on/off at a first high frequency, and a second switching control in which an ON/OFF operation of the switching element is intermittently stopped at a second frequency which is lower than the first frequency of the first switching control,

wherein when the current flowing through the solid-state light source is changed, the second frequency is varied.

2. The lighting device of claim 1, wherein when the first frequency becomes higher, the control unit raises the second frequency.

3. The lighting device of claim 1, wherein when the current flowing through the solid-state light source is less than a predetermined value, the control unit controls the first frequency to be almost constant.

4. The lighting device of claim 1, wherein when the current flowing through the solid-state light source is less than a predetermined value, the control unit controls an ON-time period of the switching element in the first switching control to be almost constant.

5. The lighting device of claim 1, wherein when the current flowing through the solid-state light source is less than a predetermined value, the control unit raises the second frequency as the first frequency becomes higher, whereas when the current flowing through the solid-state light source is equal to or greater than the predetermined value, the control unit controls the second frequency to be almost constant.

6. The lighting device of claim 1, wherein the DC power circuit unit is configured such that an inductor is connected in series to the switching element and the current flows through the solid-state light source by using a charging current and a discharging current of the inductor, and the switching element is controlled by the first switching control so that the current of the inductor is in a zero-crossing operation or in a discontinuous operation close to the zero-crossing operation.

7. The lighting device of claim 1, wherein the DC power circuit unit includes capacitive impedance connected in parallel to the solid-state light source and the second frequency is set such that the current flowing through the solid-state light source forms a continuous waveform.

8. The lighting device of claim 1, further comprising a capacitor for smoothing a control signal of the second frequency, wherein the first frequency is set based on a voltage of the capacitor.

9. An illumination apparatus comprising the lighting device described in claim 1.