LIGHT-DIMMING DEVICE

• US 20170150569A1
• Filed: 03/26/2015
• Published: 05/25/2017
• Est. Priority Date: 04/03/2014
• Status: Active Grant

• Current Assignee: Panasonic Intellectual Property Management Co., Ltd. (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Intellectual Property Management Co., Ltd. (Panasonic Holdings Corporation)
• Inventors: HAYASHI, Masanori, SUEHIRO, Yoshifumi, GOTO, Kiyoshi
• Granted Patent: US 9,801,247 B2
• Time in Patent Office: Days
• CPC Class Codes: H05B 39/041 the light-intensity of the source H05B39/08 takes precedence
• CPC Class Codes: H05B 39/048 with reverse phase control
• CPC Class Codes: H05B 45/10 Controlling the intensity of the light
• CPC Class Codes: H05B 45/37 Converter circuits
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

A light-dimming device includes a switch including a switching device, a controller, and a power supply module. The power supply module includes a capacitor to be charged by a constant voltage circuit. The controller includes a driver circuit, a zero-cross detection circuit, a detecting circuit, and a control circuit, and receive electric power from the capacitor. The driver circuit drives the switching device in accordance with a PWM signal. The control circuit starts generation of a pulse, to be contained in the PWM signal, for turning on the switching device after the zero-cross detection circuit detects zero-cross and also a voltage across the capacitor is threshold or more.

Claims

1. A light-dimming device, comprising:

first and second terminals that allow a series circuit of an AC power supply and an illumination load to be connected between;

a switch including a normally off type switching device connected between the first and second terminals;

an adjuster configured to vary a conduction angle of the switch;

a power supply module connected between the first and second terminals and including

a rectifier circuit configured to convert a voltage between the first and second terminals into a full-wave rectified voltage,

a constant voltage circuit configured to generate a DC voltage from the full-wave rectified voltage by the rectifier circuit, and

a capacitor configured to be charged by the constant voltage circuit; and

a controller configured to operate with electric power supplied from the capacitor of the power supply module to control the switch, the controller including

a zero-cross detection circuit configured to detect zero-cross of the voltage between the first and second terminals with the series circuit connected between the first and second terminals,

a detecting circuit configured to detect a voltage across the capacitor,

a control circuit configured to generate a PWM signal having an on-duty ratio corresponding to the conduction angle acquired from the adjuster, and

a driver circuit configured to drive the switching device in accordance with the PWM signal, wherein

the controller is configured to control the switch to turn the switching device on and then off within a half cycle of an AC voltage of the AC power supply in accordance with the conduction angle acquired from the adjuster,

the control circuit further includes a determination circuit configured to determine whether or not the voltage across the capacitor detected by the detecting circuit is less than threshold, and

the control circuit is configured to

after the zero-cross detection circuit detects zero-cross of the voltage between the first and second terminals and also the determination circuit determines that the voltage across the capacitor is the threshold or more, start generation of a pulse, to be contained in the PWM signal, for turning on the switching device, and

terminate the generation of the pulse when a period of time corresponding to the conduction angle elapses from a start of the generation of the pulse.

2. The light-dimming device of claim 1, wherein:

the determination circuit is configured to, after the zero-cross detection circuit detects zero-cross of the voltage between the first and second terminals, determine whether or not the voltage across the capacitor is less than the threshold; and

the control circuit is configured to start the generation of the pulse to be contained in the PWM signal when the determination circuit determines that the voltage across the capacitor is the threshold or more.

3. The light-dimming device of claim 2, wherein

the determination circuit is configured to

before the zero-cross detection circuit detects zero-cross of the voltage between the first and second terminals, determine whether or not the voltage across the capacitor is less than the threshold, and

in a case of determining that the voltage across the capacitor is the threshold or more, stop determining whether or not the voltage across the capacitor is less than the threshold after the zero-cross detection circuit detects the zero-cross of the voltage between the first and second terminals, and

the control circuit is configured to, in a case of the determination circuit determining that the voltage across the capacitor is the threshold or more, start the generation of the pulse to be contained in the PWM signal when the zero-cross detection circuit detects the zero-cross of the voltage between the first and second terminals.

4. The light-dimming device of claim 1, wherein

the determination circuit is configured to determine whether or not the voltage across the capacitor is less than the threshold in a period after the zero-cross detection circuit detects zero-cross of the voltage between the first and second terminals within a half cycle of the AC voltage of the AC power supply, and

the control circuit is configured to, in a case of the determination circuit determining that the voltage across the capacitor is the threshold or more in the half cycle of the AC voltage, start the generation of the pulse to be contained in the PWM signal when the zero-cross detection circuit detects a next zero-cross, which corresponds to a start of a next half cycle of the AC voltage, of the voltage between the first and second terminals.