Power factor improving circuit
First Claim
1. A power factor improving circuit in which AC power supply voltage of an AC power supply is rectified by a rectification circuit to obtain rectified voltage, the rectified voltage is inputted to a series circuit comprising a step up reactor and a main switch, the main switch being turned ON/OFF to improve a power factor of the AC power supply, and DC output voltage being obtained by a rectification smoothing circuit, the power factor improving circuit comprising:
- a current detector detecting current conducting through the step up reactor or current conducting through the main switch;
an error voltage generator amplifying a difference between the output voltage and a reference voltage to generate an error voltage;
a variable gain amplifier amplifying voltage being proportional to current detected by the current detector by varying a gain in accordance with a value of the error voltage; and
a pulse width controller generating a pulse signal whose pulse width is controlled in accordance with a value of output of the variable gain amplifier that has a negative correlation with a duty of the pulse signal, and applying the pulse signal to the main switch to control the output voltage with respect to predetermined voltage.
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Accused Products
Abstract
The power factor improving circuit has a current detecting resistor Rsh for detecting current conducting through a set up reactor L1 or current conducting through a switch Q1, an output voltage detector 11 which amplifies a difference between output voltage Eo and reference voltage Vref to generate error voltage, a variable gain amplifier 15 which amplifies voltage which is proportional to current detected by the current detecting resistor Rsh by varying gain in accordance with a value of the error voltage of the output voltage detector 11, and a pulse width modulator 14 which generates a pulse signal whose pulse width is controlled in accordance with a value of output of the variable gain amplifier 15 and which applies the pulse signal to the switch Q1 to control the output voltage Eo to predetermined voltage.
66 Citations
19 Claims
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1. A power factor improving circuit in which AC power supply voltage of an AC power supply is rectified by a rectification circuit to obtain rectified voltage, the rectified voltage is inputted to a series circuit comprising a step up reactor and a main switch, the main switch being turned ON/OFF to improve a power factor of the AC power supply, and DC output voltage being obtained by a rectification smoothing circuit, the power factor improving circuit comprising:
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a current detector detecting current conducting through the step up reactor or current conducting through the main switch; an error voltage generator amplifying a difference between the output voltage and a reference voltage to generate an error voltage; a variable gain amplifier amplifying voltage being proportional to current detected by the current detector by varying a gain in accordance with a value of the error voltage; and a pulse width controller generating a pulse signal whose pulse width is controlled in accordance with a value of output of the variable gain amplifier that has a negative correlation with a duty of the pulse signal, and applying the pulse signal to the main switch to control the output voltage with respect to predetermined voltage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 13, 16, 19)
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11. A power factor improving circuit which obtains DC output voltage, the circuit comprising:
- a first series circuit including an AC power supply and a step up reactor;
a bridge circuit being connected to both ends of the first series circuit and including a first diode, a second diode, a first switch and a second switch; and
a smoothing capacitor being connected to a connection between the first diode and the second diode, and to a connection between the first switch and the second switch;
in which the first switch and the second switch are simultaneously turned ON/OFF to improve a power factor of the AC power supply, the circuit further comprising;a current detector detecting AC current conducting through the first series circuit; a rectification circuit rectifying the detected AC current; an error voltage generator amplifying a difference between the output voltage and a reference voltage to generate an error voltage; a variable gain amplifier amplifying voltage being proportional to current rectified by the rectification circuit by varying gain in accordance with a value of the error voltage; and a pulse width controller generating a pulse signal whose pulse width is controlled in accordance with a value of output of the variable gain amplifier, and which applies the pulse signal to the first switch and the second switch to control the output voltage with respect to predetermined voltage. - View Dependent Claims (14, 17)
- a first series circuit including an AC power supply and a step up reactor;
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12. A power factor improving circuit which obtains DC output voltage, the circuit comprising:
- a first series circuit being connected to both ends of a rectification circuit which rectifies AC power supply voltage of an AC power supply and which includes a step up reactor, a first switch, a third switch and a current detector;
a second series circuit being connected to a connection between the step up reactor and the first switch and to a connection between the third switch and the current detector and which includes a second switch and a fourth switch;
a primary winding of a transformer connected to a connection between the first switch and the third switch and to a connection between the second switch and the fourth switch; and
a rectification smoothing circuit which rectifies and smoothens voltage of secondary output winding of the transformer;
in which the first to the fourth switches are turned ON/OFF to improve a power factor of the AC power supply, the circuit further comprising;an error voltage generator amplifying a difference between the output voltage and a reference voltage to generate an error voltage; a variable gain amplifier amplifying voltage being proportional to current detected by the current detector by varying gain in accordance with a value of the error voltage; a pulse width control device generating a pulse signal whose pulse width is controlled in accordance with a value of output of the variable gain amplifier; and a switch control device generating a pulse inverted signal obtained by inverting the pulse signal, which applies one of the pulse signal and the pulse inverted signal to the second switch and the third switch, which applies the other one of the pulse signal and the pulse inverted signal to the first switch and the fourth switch, and which ON/OFF controls the first to the fourth switches to control the output voltage with respect to predetermined voltage. - View Dependent Claims (15, 18)
- a first series circuit being connected to both ends of a rectification circuit which rectifies AC power supply voltage of an AC power supply and which includes a step up reactor, a first switch, a third switch and a current detector;
Specification