JP2002153068A - Power factor improving circuit and electric apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power factor improving circuit which can reduce a noise element by reducing a loss of a rectifying circuit, and improving the efficiency thereof through good balance of an AC line impedance of a single AC power supply while controlling harmonics in a power source current. SOLUTION: The power factor improving circuit is provided with a converter control means 9 for converting a power source current to the sine-wave and controlling a DC voltage to a predetermined voltage. The rectifying circuit 30 is formed of a bridge circuit of diode 3; the AC lines 1a, 1b of the single AC power source 1 are connected to an input side connecting point 30a of the rectifying circuit 30; a voltage step-up circuit is formed of a switching element 4, a reactor, and a diode 4 provided at the upper stage of the rectifying circuit 30; and the reactor 2 is provided for both AC lines 1a, 1b, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power factor improving circuit and an electric apparatus, and more particularly to a power factor improving circuit provided with a rectifying circuit and a boosting circuit for outputting a DC voltage by improving a power factor of a single-phase AC power supply. It is suitable for circuits and electric equipment.

[0002]

2. Description of the Related Art As a conventional motor control device, a power supply circuit having a rectifier circuit for rectifying a single-phase AC power supply and converting it to a DC voltage is provided, which suppresses harmonics and outputs a predetermined DC voltage. There is one described in JP-A-7-115788 (prior art 1).

The circuit of the prior art 1 will be described with reference to FIG. The motor control device controls a rectifier circuit 3 connected to the single-phase AC power supply 1, a booster circuit including the reactor 2, the switching element 4, and the diode 11, a smoothing circuit including the capacitor 5, and a switching operation of the booster circuit. A power factor improving circuit including a converter control means 9 is provided, and a motor 7 is connected to an output side of the power factor improving circuit via an inverter circuit 6. The converter control means 9 controls the switching element 4 of the booster circuit based on the power supply voltage waveform, the DC current, and the reference value of the DC voltage. With this control, the power supply current can be made a sine wave and a predetermined output voltage can be obtained.

A conventional power supply device is disclosed in
As shown in FIGS. 1 to 7 of JP-A-114372 (prior art 2), a rectifier circuit and a smoothing circuit for converting a single-phase AC power supply to DC, a booster circuit for boosting the single-phase AC power supply, A control device for turning on / off the switching element to make the power supply current a sine wave and controlling the DC voltage to a predetermined voltage, forming a rectifier circuit with a diode bridge circuit, and rectifying the AC line of the single-phase AC power supply. Connect to the input side connection point of the circuit, connect the smoothing circuit to the output side connection point of the rectifier circuit, and form the booster circuit as two switching elements, one reactor and the upper diode of the rectifier circuit, The two switching elements are connected in parallel in the reverse direction to the lower diode of the rectifier circuit between the input connection points of the rectifier circuit, and one reactor is connected to the AC line of the single-phase AC power supply. Some are provided only on one side.

[0005]

However, in the power factor correction circuit of the prior art 1, two diodes are energized when the switching element 4 of the booster circuit is on and three diodes are energized when the switching element 4 is off. However, there is a problem that the loss due to the diode is large.

The reason will be described below with reference to FIGS. 9 to 11. 9 is an equivalent circuit of the power supply circuit, FIG. 10 is a power supply equivalent circuit when the switching element is on, and FIG. 11 is a power supply equivalent circuit when the switching element is off. Since the reactor 2 and the switching element 4 are connected to the DC line after the rectifier circuit 30 as shown in FIG. 9 when the switching element 4 is turned on, the power factor improvement circuit of the prior art 1 is shown in FIG. Thus, the two diodes 3 constituting the rectifier circuit 30 are inevitably supplied with electricity, and when the switching element 4 is turned off, the other diode 11 constituting the booster circuit is also supplied with electricity as shown in FIG. It was a circuit configuration. In addition, it is not possible to refer to the power supply voltage waveform only after the rectifier circuit 30. When the switching element 4 of the booster circuit is turned on, loss occurs in the two diodes constituting the rectifier circuit 30, and when the switching element 4 is turned off, the two diodes constituting the rectifier circuit 30 are turned off.
Diode 3 and diode 11 forming a booster circuit
This is a major reason why losses occur in the three diodes 3 and 11 in total.

Further, in the power supply device of the prior art 2, since the reactor is provided only on one of the AC lines of the single-phase AC power supply, it is necessary to use a reactor having a large inductance, which results in a large reactor. Therefore, it is difficult to mount the components on the same substrate as other components, and the impedance of both AC lines becomes large, resulting in a large noise.

SUMMARY OF THE INVENTION It is an object of the present invention to reduce the loss of a rectifier circuit while improving the efficiency while suppressing harmonics of a power supply current, and to improve the impedance balance of the AC line of a single-phase AC power supply to reduce noise. An object of the present invention is to provide a power factor improvement circuit and an electric device that can be reduced.

Another object of the present invention is to reduce the loss of the rectifier circuit while suppressing harmonics of the power supply current by mounting the reactor of the booster circuit on each component mounting board of the power factor correction circuit to reduce the cost. It is another object of the present invention to obtain a power factor improving circuit which can improve efficiency and improve the balance of impedance of an AC line of a single-phase AC power supply to reduce noise.

Another object of the present invention is to accurately detect a single-phase AC power supply voltage and reliably suppress harmonics of the power supply current.
It is an object of the present invention to provide a power factor improving circuit capable of improving efficiency by reducing a loss of a rectifier circuit and improving the impedance balance of an AC line of a single-phase AC power supply to reduce noise.

Another object of the present invention is to make the switching element and the diode constituting the power factor correction circuit modular and inexpensive, to suppress the harmonics of the power supply current, to reduce the loss of the rectifier circuit, and to improve the efficiency. It is another object of the present invention to provide a power factor improving circuit capable of improving noise and reducing noise by improving the balance of impedance of an AC line of a single-phase AC power supply.

[0012]

A first feature of the present invention to achieve the above object is that a rectifier circuit and a smoothing circuit for converting a single-phase AC power supply to DC, and a booster for boosting the single-phase AC power supply. And a control device for turning on and off the switching element to make the power supply current a sine wave and controlling the DC voltage to a predetermined voltage.The rectifier circuit is formed by a diode bridge circuit, and the single-phase AC An AC line of a power supply is connected to an input-side connection point of the rectifier circuit, the smoothing circuit is connected to an output-side connection point of the rectifier circuit, and the booster circuit has two switching elements, two reactors, and the rectifier circuit. And the two switching elements are connected in parallel in the opposite direction to the lower diode of the rectifier circuit between the input side connection points of the rectifier circuit. Lies in the provision of the said reactor in both the single-phase AC power source AC lines.

Preferably, the two reactors are also mounted on a board on which components constituting a power factor correction circuit are mounted.

Preferably, the control device is configured to control the switching element based on a detection value of a power supply voltage reference circuit for detecting a power supply voltage and a detection value of a detection resistor for detecting a power supply current, The power supply voltage reference circuit is configured to detect a power supply voltage from both of the AC lines via power supply voltage detection diodes.

Preferably, the control device is configured to control the switching element based on a detection value of a detection resistor for detecting a power supply current, and the switching element and the switching element are connected in parallel in opposite directions. That is, the connected diode is modularized.

Preferably, the control device is configured to control the switching element based on a detection value of a detection resistor for detecting a power supply current, and the switching element and the switching element are connected in parallel in opposite directions. And the detection resistor is provided on the AC line, and the diode and the switching element of the rectifier circuit are all modularized.

A second feature of the present invention is that a rectifier circuit and a smoothing circuit for converting a single-phase AC power supply to DC, a booster circuit for boosting the single-phase AC power supply, and a power supply current by turning on and off the switching element. A control device for forming a sine wave and controlling the DC voltage to a predetermined voltage, an inverter circuit to which DC is input from the smoothing circuit, and a motor whose rotation speed is controlled by the inverter circuit; Formed by a diode bridge circuit, connected the AC line of the single-phase AC power supply to the input side connection point of the rectification circuit, connected the smoothing circuit to the output side connection point of the rectification circuit, Two switching elements, two reactors and an upper diode of the rectifier circuit are also formed, and the two switching elements are connected to the input side of the rectifier circuit. Parallel connected in reverse direction to the lower diode of the rectifier circuit between the reactor is to provided both AC lines of the single-phase AC power source.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. In the second and subsequent embodiments, the description overlapping with the first embodiment will be omitted. The same reference numerals in the drawings of the embodiments and the drawings of the conventional example indicate the same or corresponding components.

First, a first embodiment of the present invention will be described with reference to FIGS.
This will be described with reference to FIG.

First, an electric circuit of an electric device will be described with reference to FIG. FIG. 1 is an electric circuit diagram of an electric apparatus according to a first embodiment of the present invention. Although the case of an air conditioner will be described as the electric apparatus of the present embodiment, the present invention is applied to a power supply that rectifies a single-phase AC power supply such as a refrigerator and other home appliances and outputs a predetermined DC voltage, and an AC power supply. It can be applied to all electric devices that require a power supply that improves the power factor.

The single-phase AC power supply 1 is a commercial power supply for home use, and outputs an AC voltage to the AC lines 1a and 1b. The rectifier circuit 30 and the smoothing capacitor 5 convert a single-phase AC power supply to DC. The rectifier circuit 30 is formed by a bridge circuit of four diodes 3, and includes AC lines 1a, 1
b has an input-side connection point 30a connected thereto, and an output-side connection point 30b connected to both ends of the smoothing capacitor 5, and outputs a pulsating DC voltage having a full-wave rectified waveform of the power supply voltage.

The booster circuit includes two reactors 2, two switching elements 4, two diodes 3 in the upper stage of the rectifier circuit 30, etc., and boosts the voltage by the switching operation of the switching element 4 and the energy storage effect of the reactor 2. . The two reactors 2 are composed of the same thing, and are connected to both the AC lines 1a and 1b. The two switching elements 4 are composed of the same power element, and are connected in parallel in the opposite direction to the power supply current detection resistor 8 and the diode 3 below the rectifier circuit 30 between the input side connection points 30a. A power supply current detection resistor 8 is provided between the circuits.

The smoothing capacitor 5 constitutes a smoothing circuit, and converts the pulsating DC voltage boosted by the boosting circuit into a stable DC voltage and outputs it. The inverter circuit 6 connected to the motor 7 is connected to the smoothing capacitor 5 and drives the motor 7 by converting a DC voltage supplied from the smoothing capacitor 5 into an arbitrary AC voltage. The motor 7 drives a compressor, a fan, and the like in the air conditioner.

The control device comprises a converter control means 9, a power supply current detecting resistor 8, a power supply voltage reference circuit 10, and other control means.
And so on. The converter control means 9 receives a power supply current from the power supply current detection resistor 8, a full-wave rectified waveform from the power supply voltage reference circuit 10, a DC voltage from the smoothing capacitor 6, and a sine of the power supply current based on the input. The switching operation of the booster circuit is controlled so that the voltage and the output voltage become predetermined values. The power supply voltage reference circuit 1
Reference numeral 0 denotes power supply voltage detecting diodes 10a and 10b connected to the AC lines 1a and 1b, and voltage dividing resistors 10c and 10d for dividing the detected voltage.
Thus, by forming the power supply voltage reference circuit,
The single-phase AC power supply voltage can be accurately detected, and the harmonics of the power supply current can be reliably suppressed using the detected value.

Next, the operation of the power factor improving circuit in the circuit of the electric equipment will be described with reference to FIGS. 2 is an equivalent circuit diagram of the power factor correction circuit in the electric device of FIG. 1, FIG. 3 is an equivalent circuit diagram of the switching element in FIG. 2 when on, FIG. 4 is an equivalent circuit diagram of the switching element in FIG. FIG. 5 is a diagram comparing the efficiency of the power factor correction circuit in the electric device of FIG. 1 with that of the conventional example.

When the switching element 4 in the power factor correction circuit shown in FIG. 2 is turned off after the switching element 4 is turned off, an energizing circuit shown in FIG. 3 is formed. That is,
With respect to the single-phase AC power supply 1, a reactor 2, a switching element 4, a power supply current detection resistor 8, a diode 3, and an energizing circuit of the reactor 2 are formed. In this case, one diode 3 is energized, and the loss due to the diode 3 can be reduced by half as compared with the case where the two diodes 3 of the conventional example shown in FIG. 10 are energized.
Next, when the switching element 4 is turned off, the energization circuit shown in FIG. 4 is configured. That is, for a single-phase AC power supply 1, a reactor 2, a diode 3, a smoothing capacitor 5,
Power supply current detection resistor 8, diode 3, and reactor 2
Is formed. In this case, the two diodes 3 are energized, and the loss due to the diodes 3 can be significantly reduced as compared with the case where the three diodes 3 of the conventional example shown in FIG. 11 are energized. .

As shown in FIG. 5, the efficiency of the power factor correction circuit is improved from a small input power at a low output voltage to a large input power at a high output voltage.
Within the range of 0 V to 300 V and the input power of 230 W to 1500 W, the efficiency can be improved by about 1.5% to 1.2%.

3 and 4, the reactor 2 connected to the AC lines 1a and 1b
Therefore, noise can be reduced by improving the impedance balance of the AC lines 1a and 1b of the single-phase AC power supply 1.

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 6 is an electric circuit diagram of the electric apparatus according to the second embodiment of the present invention.

In this embodiment, the diode 3 is connected in parallel to the switching element 4 in the opposite direction, and the switching element 4 and the diode 3 connected in parallel are modularized, and the power supply current detection is performed between the parallel connected circuits. Resistance 8
This embodiment differs from the first embodiment in that a power supply current is input from the power supply current detection resistor 8 to the converter control means 9 via a diode (not shown). Is basically the same as the first embodiment.

By modularizing the switching element 4 and the diode 3 connected in parallel in this way, it is possible to reduce the cost.

Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 7 is an electric circuit diagram of an electric device according to a third embodiment of the present invention.

In this embodiment, the diode 3 is connected in parallel to the switching element 4 in the reverse direction, the power supply current detecting resistor 8 is provided on the AC line 1b, and the diode 3 and the switching element 4 of the rectifier circuit are all modularized. A power supply current detection resistor 8 is provided between the parallel connection circuits, and the power supply current is input to the converter control means 9 from the power supply current detection resistor 8 via a diode (not shown). This is different from the first embodiment, and the other points are basically the same as the first embodiment.

By making all the diodes 3 and switching elements 4 of the rectifier circuit modular, the cost can be further reduced.

[0035]

As described above, according to the present invention,
A power factor improvement circuit that suppresses harmonics of the power supply current, reduces losses in the rectifier circuit, improves efficiency, and improves the impedance balance of the AC line of the single-phase AC power supply to reduce noise. And electrical equipment.

Further, according to the present invention, the reactor of the booster circuit is mounted on each component mounting board of the power factor correction circuit to make it inexpensive, and the harmonic of the power supply current is suppressed, and the loss of the rectifier circuit is reduced. As a result, it is possible to obtain a power factor improving circuit capable of improving efficiency and improving the impedance balance of the AC line of the single-phase AC power supply to reduce noise.

Further, according to the present invention, while accurately detecting a single-phase AC power supply voltage and reliably suppressing harmonics of the power supply current, the loss of the rectifier circuit is reduced and the efficiency is improved.
A power factor improving circuit capable of reducing noise by improving the impedance balance of the AC line of the single-phase AC power supply can be obtained.

Further, according to the present invention, the switching element and the diode constituting the power factor correction circuit are modularized to be inexpensive, and while suppressing harmonics of the power supply current,
It is possible to obtain a power factor improving circuit capable of improving the efficiency by reducing the loss of the rectifier circuit and improving the impedance balance of the AC line of the single-phase AC power supply to reduce noise.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram of an electric device according to a first embodiment of the present invention.

FIG. 2 is an equivalent circuit diagram of a power factor improvement circuit in the electric device of FIG.

FIG. 3 is an equivalent circuit diagram when the switching element in FIG. 2 is turned on.

FIG. 4 is an equivalent circuit diagram when the switching element in FIG. 2 is off.

5 is a diagram comparing the efficiency of a power factor correction circuit in the electric device of FIG. 1 with that of a conventional example.

FIG. 6 is an electric circuit diagram of an electric device according to a second embodiment of the present invention.

FIG. 7 is an electric circuit diagram of an electric device according to a third embodiment of the present invention.

FIG. 8 is an electric circuit diagram of a conventional electric device.

9 is an equivalent circuit diagram of a power factor correction circuit in the electric device of FIG.

10 is an equivalent circuit diagram when the switching element in FIG. 9 is turned on.

11 is an equivalent circuit diagram when the switching element in FIG. 9 is off.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Single phase AC power supply, 1a, 1b ... AC line, 2 ... Reactor, 3 ... Diode, 4 ... Switching element, 5 ...
Smoothing capacitor, 6… Inverter circuit, 7… Motor, 8
... Power supply current detection resistor, 9 ... Converter control means, 10 ...
Power supply voltage reference circuit, 10a, 10b ... power supply voltage detection diode, 11 ... diode, 30 ... rectifier circuit, 30a
... input side connection point, 30b ... output side connection point.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Makoto Ishii 800 Tomita, Odaicho, Ohira-cho, Shimotsuga-gun, Tochigi Prefecture Within Hitachi Tochigi Technology Co., Ltd. (72) Inventor Yasuo Notohara 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture 5H006 AA01 AA02 BB05 CA01 CA07 CB01 CB08 CC01 CC08 DB01 5H740 NN03

Claims (6)

[Claims] 1. A rectifier circuit and a smoothing circuit for converting a single-phase AC power supply to DC, a booster circuit for boosting the single-phase AC power supply, and turning on and off the switching element to make a power supply current a sine wave and reduce a DC voltage. A control device for controlling the voltage to a predetermined voltage, wherein the rectifier circuit is formed by a bridge circuit of a diode, and an AC line of the single-phase AC power supply is connected to an input side connection point of the rectifier circuit, and the smoothing is performed. A circuit is connected to an output side connection point of the rectifier circuit, and the booster circuit is formed by also using two switching elements, two reactors, and an upper diode of the rectifier circuit.
Two switching elements are connected in parallel in the opposite direction to the lower diode of the rectifier circuit between the input side connection points of the rectifier circuit, and the reactor is provided on both of the AC lines of the single-phase AC power supply. Power factor improvement circuit. 2. The power factor improving circuit according to claim 1, wherein said two reactors are also mounted on a substrate on which components constituting the power factor improving circuit are mounted. 3. The power factor improving circuit according to claim 1, wherein the switching element is controlled based on a detection value of a power supply voltage reference circuit for detecting a power supply voltage and a detection value of a detection resistor for detecting a power supply current. Wherein the power supply voltage reference circuit is configured to detect a power supply voltage from both of the AC lines via respective power supply voltage detection diodes. 4. The power factor correction circuit according to claim 1, wherein the control device is configured to control the switching element based on a detection value of a detection resistor for detecting a power supply current, and A power factor improving circuit, wherein a diode connected in parallel in the opposite direction to the switching element is modularized. 5. The power factor correction circuit according to claim 1, wherein the control device is configured to control the switching element based on a detection value of a detection resistor for detecting a power supply current, and wherein A power factor improving circuit, which is connected in parallel to the switching element in the opposite direction, the detection resistor is provided on the AC line, and all of the diode and the switching element of the rectifier circuit are modularized. 6. A rectifier circuit and a smoothing circuit for converting a single-phase AC power supply to DC, a booster circuit for boosting the single-phase AC power supply, turning on / off the switching element to make a power supply current a sine wave, and to reduce a DC voltage. A control device for controlling to a predetermined voltage, an inverter circuit to which DC is input from the smoothing circuit, and a motor whose rotation speed is controlled by the inverter circuit are provided, and the rectifier circuit is formed by a diode bridge circuit. Connecting the AC line of the single-phase AC power supply to an input-side connection point of the rectifier circuit, connecting the smoothing circuit to an output-side connection point of the rectifier circuit, and connecting the booster circuit to two switching elements, The reactor and the upper diode of the rectifier circuit are also formed,
Two switching elements are connected in parallel in the opposite direction to the lower diode of the rectifier circuit between the input side connection points of the rectifier circuit, and the reactor is provided on both of the AC lines of the single-phase AC power supply. And electrical equipment.