JPH0898533A - Power-supply circuit - Google Patents

Abstract

PURPOSE: To obtain a power-supply circuit which is made small, lightweight and low-cost and whose power factor is improved by a method wherein a DC power supply in which a pulse-current power supply appearing across a first capacitor has been added to a DC power supply appearing across a second capacitor is used as an output. CONSTITUTION: A pulse-current power supply which has been charged in a first small-capacitance capacitor C01 is used as a first power supply V1, and a DC power supply which has been made by the high-frequency switching operation of a switching transistor Q1 by making use of the puls-current power supply V1 as a step-up power supply is used as a second power supply V2. Then, the first power supply V1 and the second power supply V2 are connected in series to use as a third power supply V3. Consequently, the second power supply V2 which in formed by an active filter circuit is at 50% or lower of the whole, respective elements inside the active filter circuit are made small, lightweight and low-cost, the thrid power supply V3 as an output voltage is a high voltage, its power-supply capacity is large, and a high power factor can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of power factor and harmonic distortion of a power supply circuit such as a high frequency fluorescent lamp lighting device. More specifically, it is required to have a small size, a light weight, a high power factor and a low cost. The present invention relates to a power supply circuit effective for equipment such as a high-frequency fluorescent lamp lighting device.

[0002]

2. Description of the Related Art An example of a power supply circuit used in a typical conventional fluorescent lamp lighting device will be described with reference to FIGS.

FIG. 7A shows a capacitor input type power supply circuit, which has been used frequently historically, but the power factor is poor and demand for improvement is increasing from the viewpoint of energy saving.

That is, commercial AC power supply (50/60 Hz) 1
Is the input (Vin) of the power supply circuit, 2 is the rectifier circuit,
A smoothing circuit 3 rectifies the positive electrode side by the diode D1 and charges the electrolytic capacitor C1. Also, the diode D
2, the negative electrode side is rectified and the electrolytic capacitor C2 is charged. Therefore, the output voltage Vo, the input voltage Vin,
The input current Iin has the waveform shown in FIG. 7B, and the positive and negative input current Iin flows in at a small conduction angle α every half cycle.

The circuit is often used because it is simple and efficient, but the power factor is 50 because the conduction angle α is narrow.
It becomes about 70%, the apparent power is large, and the power loss in the transmission path cannot be ignored, and energy saving is not achieved as a whole.

As a countermeasure against the above problem, a so-called choke input type composed of a low frequency choke coil Lo, a bridge rectifier circuit 4 and an electrolytic capacitor C1 as shown in FIG. 8 has been used for a long time. The low-frequency choke coil Lo itself connected to is extremely large, is shunned in terms of cost, weight, and space, and is only used as a power source with a slightly small capacity (tens of watts or less). .

Next, in the case of the current compensation type shown in FIG. 9A, double-wave rectification is performed by the diodes D1 to D4 of the bridge rectification circuit 4, and the electrolytic capacitor C is smoothed by the smoothing / current compensation circuit 5.
1 → diode D6 → inductor L1 → electrolytic capacitor C2 charges C1 and C2 for t1 period (FIG. 9).
(See (B)). At this time, it is a necessary condition that the electrolytic capacitors C1 and C2 have the same capacitance.

When the voltage Vo after rectification decreases with time and reaches 50% of the peak value, the charges accumulated in the electrolytic capacitors C1 and C2 are electrolytic capacitor C1 → load → diode D5, electrolytic capacitor C2 → diode D.
7 → t2 power is supplied to the load in parallel through each path of the load
It will be supplied for a period.

As described above, in the case of the current compensation type rectifying / smoothing circuit, the period t1 of up to 50% of the AC voltage peak value is obtained.
The input current Iin flows in, and the conduction angle α is expanded and the power factor is improved as compared with the case of the capacitor input type voltage doubler rectifier circuit (FIG. 7) as shown in FIG. 9B.

In the above circuit, the power factor can be improved to about 90%. However, since the output voltage is necessarily determined (the minimum value is 50% of the peak value), there is a disadvantage that when a high voltage is required, it is necessary to boost the voltage separately.
Further, in terms of the circuit configuration, the charging voltage of the electrolytic capacitors C1 and C2 is half of the maximum Vo, which makes it difficult to apply the voltage doubling rectifier circuit, which is another factor that narrows the range of application.

Further, since the recent demand for power factor improvement is targeted at 95% or more, this circuit is not sufficient.

Next, FIG. 10 (A) shows a so-called active filter type power supply circuit, which basically aims at a power factor of 100%, and an inflowing current Iin is an input voltage V.
The switching operation of the switching transistor Q1 in the active filter circuit 7 is controlled by the switching control circuit 6 so as to be proportional to in, and as shown in the input current / voltage waveform diagram of FIG. The average value 9 (input average current) of Ir) is made proportional to the rectified voltage 10 (Vi).

The features of the active filter circuit 7 will be described in detail. The instantaneous values of the line voltage and the line current are detected, and the choke coil L1 inserted in series in the line,
And the switch of the switching transistor Q1 causes the effective value (ΔV / Δ
I = R) is controlled to be constant. The switching frequency is generally selected to be several tens KHz or more.

The switching control system includes a variable frequency system and a pulse width control system, and a system suitable for the application is selected.

The various power supply circuits described above constitute a high frequency power supply such as a high frequency fluorescent lamp lighting device by supplying electric power Vo as a DC power supply to a high frequency circuit (so-called inverter circuit) connected to the power supply circuit.

[0016]

Recently, there has been a problem of waveform distortion (harmonic distortion) of a power supply line caused by harmonics generated from electronic equipment. When the waveform distortion becomes large, the waveform is connected to the same power supply line. May cause malfunction or damage to electronic equipment or substation equipment as a power supply source (referred to as harmonic interference).

On the other hand, when the equipment connected to the power supply line is composed of pure resistors, inductors, and capacitors only, the power factor decreases according to the phase difference between the power supply line voltage and current, so that the reactive current is reduced. It increases but does not distort the line voltage. However, now that many devices have been converted to direct current, the rectifier circuit consisting of a diode and a capacitor acts as a non-linear load on the power supply line, and the peak value of the current flowing in the power supply line is the average current. The current flows 5 to 10 times and causes a significant distortion in the power supply line, and the problem of harmonic interference appears. Therefore, in order to reduce the harmonic distortion, it is necessary to make the input voltage waveform (sine wave) of the commercial AC power supply and the input current waveform proportional to each other, that is, to increase the power factor.

On the other hand, as described above, the improvement of the power factor in the conventional rectifying / smoothing circuit (FIGS. 7 and 9) is not satisfactory, and the power factor is poor because the reactive power is large in addition to the above harmonic distortion. This is one of the factors that increase the loss in the power transmission path on the side and also increase the load on the power switch and the connector, which impairs reliability.

In this respect, when the power factor is improved by using the above-mentioned active filter system (FIG. 10), (1) the input current is reduced, (2) the input voltage is widened, and (3) the voltage due to the input wiring. Drop reduction, (4) Harmonic current reduction, (5)
The ripple reduction of the input smoothing capacitor can be improved.

However, although the above method is almost perfect from the viewpoint of improving the power factor, as is apparent from FIG.
Since all the input current Iin of (1) is switched, there is a problem that output loss occurs with respect to input and efficiency deteriorates. In addition, there is a problem that each element becomes large and costly. Therefore, it will be difficult to apply it as it is to a fluorescent lamp lighting device or the like in which demand for low cost is severe.

As described above, in the conventional power supply circuit, the power factor of the current compensation type is considerably improved, but the output voltage is low due to the circuit configuration, and boosting is required, and double voltage rectification cannot be applied. The active filter method has an ideal power factor, but has a problem in that the circuit is complicated and the cost is high.

The present invention has been made in view of the above circumstances, and the power source portion of the active filter system is 50%.
It is intended to provide a power supply circuit which has a power factor improved while achieving the reduction in size, weight and cost while suppressing the following.

[0023]

SUMMARY OF THE INVENTION The present invention is directed to a bridge rectifier circuit having a commercial AC power source as an input, and a first capacitor connected to the output of the bridge rectifier circuit and having a small capacity to the extent that harmonic distortion does not occur. And an inductor, a switching transistor, and a switching control circuit configured to create a DC power supply across a second capacitor connected in series with the first capacitor by high-frequency switching from a pulsating current power supply appearing across the first capacitor. And a pulsating current power supply appearing at both ends of the first capacitor and a DC power supply made at both ends of the second capacitor are output as a DC power supply. The above object is achieved by providing a power supply circuit.

[0024]

In the power supply circuit according to the present invention, the pulsating current power supply is charged in the first capacitor C01 having a small capacity to the extent that harmonic distortion connected to the output of the bridge rectification circuit having the commercial AC power supply as the input does not occur. Is the first power source (V1),
The pulsating current power supply V1 is used as a step-up power supply, and the DC power supply created by high-frequency switching of the switching transistor Q1 is used as the second power supply (V2). The first power source V1 and the second power source V2 connected in series are used as the third power source V3.

Therefore, since the second power source portion (V2) formed by the active filter circuit is 50% or less of the whole (see FIG. 3), each element in the active filter circuit is small, lightweight and low cost. Regardless of the output voltage V
3 has a high voltage, a large power supply capacity, and a high power factor of about 98% can be obtained.

The third power supply V3 as an output contains ripples and is not a complete DC power supply, but is sufficient as a power supply for a high frequency circuit used in a fluorescent lamp lighting device or the like.

Since the output voltage (V3) is kept constant with respect to input voltage fluctuations and load fluctuations, load fluctuation stability, which is a necessary condition for the power supply circuit of the fluorescent lamp lighting device for multiple lamps, is improved.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a power supply circuit according to the present invention and experimental results will be described in detail with reference to FIGS. The same parts as those in the above-mentioned conventional example are designated by the same reference numerals.

FIG. 1 is a circuit example of a high-frequency fluorescent lamp lighting device using a power supply circuit 15 according to the present invention.
Reference numeral 5 denotes a bridge rectifier circuit 4 having a commercial AC power supply (50/60 Hz) 1 as an input, and a first capacitor C01 connected to the output of the bridge rectifier circuit 4 and having a small capacity to the extent that harmonic distortion does not occur. , A second capacitor C connected in series with the first capacitor C01 by high frequency switching from a pulsating current power supply V1 appearing at both ends of the first capacitor C01
02 Active filter circuit 1 composed of inductor L2, switching transistor Q1, and switching control circuit 16 configured to form a DC power supply V2 at both ends
7, a pulsating current power source V1 appearing across the first capacitor C01 and the second capacitor C1.
02 DC power supply V added with DC power supply V2 created at both ends
3 is an output.

The power supply circuit 15 is a high frequency circuit 20.
A direct current power supply V3 is supplied to a so-called inverter circuit, and a high-frequency output of the high-frequency circuit 20 provides a fluorescent lamp F as a load.
L (single or multiple lights) is connected.

The lighting system of the above high-frequency fluorescent lamp lighting device is L
The C resonance method is a series resonance method of an inductor LX connected in series with the fluorescent tube FL and a capacitor CX connected in parallel with the fluorescent tube FL. In this prototype, the above fluorescent tube F
Five L32S were connected in parallel.

A commercial AC power source (50H in this prototype)
The noise filter circuit 11 connected to z) 1 is for noise prevention.

Next, the first capacitor C01 is a film capacitor, which was 2.2 μF in this prototype. The C01
If the capacitance is large, it becomes a capacitor input type and waveform distortion occurs and the power factor deteriorates. Further, since switching is performed as described later, it is necessary to store it to some extent although it is a high frequency. Therefore, the C01 capacity determination should be carefully examined.

The second capacitor C02 is an electrolytic capacitor, and in this prototype, it is set to 560 μF.

Next, the resistors R1 and R2 and the electrolytic capacitor C
03 is for averaging and monitoring the voltage of the DC power supply V3 as an output in FIG.
The switching control circuit 16 operates so that V3 is returned to and the V3 becomes constant.

The control method is a variable frequency method.
In this prototype, the oscillation frequency of the active filter circuit 17 is set to 50 KHz.

The results of the trial production will be described in detail below.

FIG. 2 shows the voltage waveform of the pulsating current voltage V1 across the first capacitor C01, and FIG. 3 shows the voltage waveform of the DC power supply V3. 4 shows the current waveform of the inductor L2 of the active filter circuit, and FIG. 5 shows the inductor L2.
It is an enlarged view of the current IL waveform of FIG. Further, FIG. 6 shows an input voltage Vin and an input current Iin supplied from the commercial AC power supply 1.
It is a waveform diagram of.

It can be seen from FIG. 2 that a maximum pulsating voltage (first power source) V1 of 141 V appears across the film capacitor C01 which is the first capacitor. The switching input current Ir (maximum 5.2 A) shown in FIG. 4 flows through the inductor L2 by the switching operation of the switching transistor Q1 of the active filter circuit 17 using the pulsating current voltage V1 as a step-up power source, and energy is accumulated, The second capacitor C02 of the electrolytic capacitor is charged through the diode D8 and 84V is applied to both ends.
DC power supply (second power supply) V2 of

The above switching operation will be described in detail with reference to FIG.
As shown in an enlarged view of the Ir waveform of the above, energy is stored in the inductor L2 when the switching transistor Q1 is on (“a” part), and the stored energy is a second capacitor when the switching transistor Q1 is off.
Charge to 02 (“B” part).

As a result, the pulsating current voltage V1 including ripples and the DC voltage V2 with almost no ripple generated by the active filter circuit 17 are added across the first capacitor C01 and the second capacitor C02 connected in series. Voltage waveform of the third power supply V3 shown in FIG.
V) is obtained.

In the figure, the DC component of 84 V is V2 generated by the switching power supply (active filter circuit 17).
Then, the pulsating current voltage component of 141 V becomes the first power source V1 only by full-wave rectifying the commercial AC power source 1.

The third power supply V3 contains some ripples, but it is at a level that does not cause any problem as a DC power supply in the case of a fluorescent lamp load. However, it can be said that the present power supply circuit 15 is suitable for a power supply device of an inverter device that does not directly use the DC power supply V3 as in the above embodiment but is used as a power supply for the high frequency circuit 20.

According to the experimental result of the high frequency fluorescent lamp lighting device of the present embodiment, as shown in FIG. 6, the input voltage Vin =
100V; input current Iin = 1.377A at 50Hz,
The input power was 135 W, the conduction angle reached almost 100%, and although the input current Iin waveform was slightly distorted at the rising edge, it was almost similar to the input voltage Vin waveform, and a power factor of 98% was obtained.

As described above, the power supply circuit of the present invention uses the active filter circuit, but adds not only the DC power supply generated by the active filter circuit but also the pulsating current power supply, so that the power supply capacity is large and the active filter circuit is large. Has the advantage of being small and efficient. Moreover, the power factor of about 98%, which is equivalent to that of the conventional active filter circuit (FIG. 10), is secured.

Therefore, it is clear that the use of the present power supply circuit provides a margin in the power supply capacity and improves the stability against the load fluctuation of the multi-lamp fluorescent tube or the like.

[0047]

Since the power supply circuit according to the present invention is configured as described above, it has the following effects.

(1) A power circuit with a high power factor of about 98% is realized while being compact, lightweight, and low cost, and in particular, it is excellent in improving the power factor of a high-frequency fluorescent lamp lighting device and reducing the cost. Have the effect.

(2) The power supply voltage can be easily stabilized, and the load fluctuation stability of the fluorescent lamp lighting device for multiple lamps can be improved.

[Brief description of drawings]

FIG. 1 is a circuit example of a high-frequency fluorescent lamp lighting device using a power supply circuit according to the present invention.

FIG. 2 is a voltage waveform diagram of a pulsating current voltage V1 across a first capacitor C01.

FIG. 3 is a voltage waveform diagram of a DC power supply V3.

FIG. 4 is a current waveform diagram of an inductor L2 of the active filter circuit.

FIG. 5 is an enlarged view of a current IL waveform of the inductor L2.

FIG. 6 is an input voltage Vi supplied from a commercial AC power supply 1.
It is a waveform diagram of n, the input current Iin.

7A is a conventional capacitor input type power supply circuit, and FIG. 7B is an input voltage / input current waveform diagram of the circuit.

FIG. 8 is a conventional choke input type power supply circuit.

FIG. 9A is a conventional current compensation type power supply circuit,
FIG. 3B is a waveform diagram of output voltage, input voltage, and input current of the same circuit.

FIG. 10A is a conventional active filter type power supply circuit, and FIG. 10B is an input current / input voltage waveform diagram.

[Explanation of symbols]

 C1, C2, C03 Electrolytic capacitor D1 to D8 Diode Lo Low frequency choke coil L1 Choke coil L2 Inductor LX Inductor CX capacitor C01 First capacitor (film capacitor) C02 Second capacitor (electrolytic capacitor) C03 Electrolytic capacitor R1, R2 Resistance FL Fluorescent tube Q1 to Q3 Switching transistor Vo Output voltage Vin Input voltage V1 Pulsating current power source (first power source) V2 DC power source (second power source) V3 Added DC power source (third power source) Iin Input current α Conduction angle 1 Commercial AC power supply (50 / 60Hz) 2 Rectifier circuit 3 Smoothing circuit 4 Bridge rectifier circuit 5 Smoothing / current compensation circuit 6, 16 Switching control circuit 7, 17 Active filter circuit 8 Switching input current (= Ir) 9 Input average Current 10 Rectifier 11 Noise filter 15 power supply circuit 20 high-frequency circuit

Claims (1)

[Claims] 1. A bridge rectifier circuit having a commercial AC power supply as an input, a small-capacity first capacitor connected to the output of the bridge rectifier circuit that does not generate harmonic distortion, and appearing at both ends of the first capacitor. An active filter circuit including an inductor configured to create a DC power supply across a second capacitor connected in series with a first capacitor by high-frequency switching from a pulsating current power supply, a switching transistor, and a switching control circuit. At the same time, a pulsating current power supply appearing at both ends of the first capacitor and a direct current power supply made at both ends of the second capacitor are added to output a DC power supply.