Lighting device and lighting fixture using same

Patent metadata

Field	Value
Publication number	US-2016198532-A1
Application number	US-201614986794-A
Country	US
Kind code	A1
Filing date	Jan 4, 2016
Priority date	Jan 6, 2015
Publication date	Jul 7, 2016
Grant date	—

Abstract

Provided is a lighting device including two switching elements, a control circuit, a resonance circuit, a rectification circuit, and a feedback circuit. The control circuit controls two switching elements such that the two switching elements operate separately from each other. The control circuit changes the switching frequencies of the two switching elements from high frequencies to low frequencies, relative to one another, when the operation (switching operation) of the switching elements is started. The control circuit controls the feedback circuit such that the difference output from an error amplifier approaches zero within a period of time from a point of time at which the switching operation is stopped to a point of time at which the switching operation is next started.

First claim

1 . A lighting device comprising:
a pair of input terminals; a pair of output terminals; at least two switching elements; a control circuit that controls the at least two switching elements; a resonance circuit including a coupling unit having a first inductor and a second inductor, a third inductor, and a first capacitor; a rectification circuit configured to rectify a terminal voltage of the second inductor; a second capacitor configured to smooth a voltage rectified by the rectification circuit; and a feedback circuit configured to detect an output current which is a current flowing between the pair of output terminals or an output voltage which is a voltage applied between the pair of output terminals, and to feedback a difference between a reference voltage and a detected voltage which is a voltage proportional to the output current or the output voltage to the control circuit, wherein the first inductor and the second inductor are magnetically coupled, the at least two switching elements are connected in series, the at least two switching elements connected in series are electrically connected between the pair of input terminals, the third inductor is connected to a first terminal of the first inductor, and the first capacitor is connected to a second terminal of the first inductor, a series circuit of the third inductor, the first inductor, and the first capacitor is connected in parallel to one of the at least two switching elements, the second capacitor is electrically connected between the pair of output terminals, the feedback circuit includes
a detector configured to detect the output current or the output voltage, and
an error amplifier configured to receive the detected voltage and the reference voltage and output the difference,
the control circuit is configured to control the at least two switching elements such that the at least two switching elements operate separately from each other and the difference output from the error amplifier becomes zero, the control circuit is configured to change switching frequencies of the at least two switching elements from high frequencies to low frequencies, relative to one another, when the operation of the at least two switching elements is started, and the control circuit is configured to control the feedback circuit such that the difference output from the error amplifier approaches zero within a period of time from a point of time at which the operation of the at least two switching elements is stopped to a point of time at which the operation of the at least two switching elements is next started.

2 . The lighting device according to claim 1 , wherein
the control circuit is configured to control the at least two switching elements with a same switching frequency, the control circuit is configured to control the at least two switching elements such that, when the change in the switching frequencies of the at least two switching elements from high frequencies to low frequencies, relative to one another, is started, the switching frequencies of the at least two switching elements become equal to or higher than a first resonance frequency which is a resonance frequency determined by an inductance of the first inductor and a capacitance of the first capacitor, and the control circuit is configured to control the at least two switching elements such that, when the change in the switching frequencies of the at least two switching elements from high frequencies to low frequencies, relative to one another, is ended, the switching frequencies of the at least two switching elements become lower than the first resonance frequency and also equal to or higher than a second resonance frequency which is a resonance frequency determined by the inductance of the first inductor, an inductance of the third inductor, and the capacitance of the first capacitor.

3 . The lighting device according to claim 1 , wherein
the control circuit is configured to control the feedback circuit such that, when the operation of the at least two switching elements is started, a voltage level of the reference voltage input to the error amplifier increases as an elapse of time.

4 . The lighting device according to claim 3 , wherein
the feedback circuit further includes a generator configured to generate the reference voltage, the generator includes a third capacitor, the error amplifier is configured to receive a terminal voltage of the third capacitor as the reference voltage, and the control circuit is configured to discharge electric charges, which have accumulated in the third capacitor, before the operation of the at least two switching elements is started, and charge the third capacitor when the operation of the at least two switching elements is started.

5 . The lighting device according to claim 4 , further comprising a series circuit of a resistor and a switch, the series circuit being connected between terminals of the third capacitor, wherein
the control circuit is configured to switch on the switch when the operation of the at least two switching elements is stopped and to switch off the switch before the operation of the at least two switching elements is started.

6 . The lighting device according to claim 1 , wherein
the control circuit is configured to control the feedback circuit such that, when the operation of the at least two switching elements is stopped, a voltage level of the detected voltage input to the error amplifier becomes equal to or higher than a voltage level of the reference voltage.

7 . The lighting device according to claim 6 , wherein
the error amplifier includes a first input terminal that receives the detected voltage and a second input terminal that receives the reference voltage, and the control circuit is configured to apply a voltage to the first input terminal of the error amplifier when the operation of the at least two switching elements is stopped.

8 . The lighting device according to claim 1 , wherein
the control circuit is configured to control the feedback circuit such that the difference output from the error amplifier becomes zero within a period of time from a point of time at which the operation of the at least two switching elements is stopped to a point of time at which the operation of the at least two switching elements is started.

9 . The lighting device according to claim 8 , further comprising a switch connected between an output terminal of the error amplifier and a circuit ground, wherein
the control circuit is configured to switch on the switch when the operation of the at least two switching elements is stopped and to switch off the switch when the operation of the at least two switching elements is started.

10 . The lighting device according to claim 1 , wherein
the control circuit is configured to cut off power supply, which is supplied to the error amplifier, when the operation of the at least two switching elements is stopped.

11 . The lighting device according to claim 1 , wherein
the control circuit includes a timer configured to time a predetermined period of time, the predetermined period of time is a period of time from a point of time at which the operation of the at least two switching elements is stopped to a point of time at which the difference output from the error amplifier becomes less than a specific value, and the control circuit is configured to start the operation of the at least two switching elements after the timer has timed the predetermined period of time when the operation of the at least two switching elements has stopped.

12 . The lighting device according to claim 1 , wherein
the control circuit is confi

Assignees

• Panasonic Ip Man Co Ltd

Inventors

• Nakajo Akira

Classifications

• H02M1/36 Primary

  Means for starting or stopping converters · CPC title

• H05B45/10

  Controlling the intensity of the light · CPC title

• H02M3/3376

  with automatic control of output voltage or current · CPC title

• H05B37/02

  Electricity · mapped topic

• H02M1/42

  Circuits or arrangements for compensating for or adjusting power factor in converters or inverters · CPC title