LIGHT-DIMMING DEVICE

• US 20170150568A1
• 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 Corporation of America (Panasonic Holdings Corporation)
• Inventors: HAYASHI, Masanori, SUEHIRO, Yoshifumi, GOTO, Kiyoshi
• Granted Patent: US 9,974,134 B2
• Time in Patent Office: Days
• CPC Class Codes: H02M 1/08 Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
• CPC Class Codes: H02M 1/36 Means for starting or stopping converters
• CPC Class Codes: H03K 17/725 for ac voltages or currents H03K17/722, H03K17/735 take precedence
• 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 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps

Abstract

Light-dimming device includes: first and second terminals; switch including switching device connected between terminals; adjuster for varying conduction angle of switch; controller for controlling switch and power supply module for supplying power to controller. Controller includes zero-cross detection circuit for detecting zero-cross of AC voltage, control circuit for generating PWM signal of on-duty ratio corresponding to conduction angle from adjuster, and driver circuit for turning device on and off by PWM signal. Controller allows device to conduct and then turn off within variable period of time, from start of half cycle of AC voltage, shorter than half cycle. Circuit starts generation of pulse in PWM signal when prescribed period of time, shorter than variable period of time, from zero-cross of voltage elapses.

Claims

1. A light-dimming device, comprising:

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

a switch that comprises a normally open switching device connected between the first and second terminals;

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

a controller that is configured to control the switch and that comprises

a zero-cross detection circuit that is configured to detect zero-cross of an AC voltage from the AC power supply with the series circuit connected between the first and second terminals,

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

a driver circuit that is configured to turn the switching device on and off in accordance with the PWM signal; and

a power supply module that is connected between first and second terminals and configured to supply power to the controller, wherein

the controller is configured to control the switch by allowing the switching device to conduct and then turn off within a variable period of time, from a start of each half cycle of the AC voltage from the AC power supply, which is shorter than a corresponding half cycle, and

the control circuit is configured to start generation of a pulse, to be contained in the PWM signal, for turning the switching device on when a prescribed period of time elapses, and to stop the generation of the pulse at an end of the variable period of time, the prescribed period of time being a period of time, shorter than the variable period of time, from detection of the zero-cross of the AC voltage by the zero-cross detection circuit.

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

the control circuit comprises a first detection circuit that is configured to detect a voltage from the power supply module;

the prescribed period of time is one of a first period of time and a second period of time, and the first period of time is longer than the second period of time; and

the control circuit is configured

to start the generation of the pulse to be contained in the PWM signal when the first period of time as the prescribed period of time elapses, in case a value of the voltage detected with the first detection circuit is less than or equal to a preset first threshold, and

to stop the generation of the pulse to be contained in the PWM signal when the second period of time as the prescribed period of time elapses, in case the value of the voltage is greater than the first threshold.

3. The light-dimming device of claim 2, wherein the power supply module comprises:

a rectifier circuit that is configured to convert the AC voltage into a full-wave rectified voltage;

a capacitor; and

a constant voltage circuit that is configured to generate a first DC voltage from the full-wave rectified voltage by the rectifier circuit to apply the first DC voltage across the capacitor, wherein

the first detection circuit is configured to detect a voltage across the capacitor.

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

the adjuster comprises a variable resistor that is configured to vary a resistance value thereof for generating a second DC voltage corresponding to the conduction angle of the switch;

the prescribed period of time is one of a first period of time and a second period of time, and the first period of time is shorter than the second period of time; and

the control circuit comprises a second detection circuit that is configured to detect the second DC voltage generated through the variable resistor,

the control circuit being configured

to start the generation of the pulse to be contained in the PWM signal when the first period of time as the prescribed period of time elapses, in case a value of the second DC voltage detected with the second detection circuit is less than or equal to a preset second threshold, and

to stop the generation of the pulse to be contained in the PWM signal when the second period of time as the prescribed period of time elapses, in case the value of the second DC voltage is greater than the second threshold.