JP3181804B2 - Power input circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rectifier circuit such as a diode bridge which rectifies an input current from a commercial AC power supply, smoothes the rectified current with a smoothing capacitor, and outputs it to a load side such as a DC-DC converter or an inverter. The present invention relates to a so-called capacitor input type power supply input circuit.

[0002]

2. Description of the Related Art FIG. 21 is an electric circuit diagram of a conventional power supply input circuit 1 of the capacitor input type. The AC current from the commercial AC power supply 2 is full-wave rectified in a rectifier circuit 3 composed of a diode bridge, then smoothed by a smoothing capacitor 4 and supplied to the load side. A DC-DC converter 5 and the like are provided on the load side as shown in FIG. 21. For example, in a portable personal computer or the like, the DC-DC converter 5 reduces the input voltage of 100V to 5V or 12V. After that, it is supplied to a load 6 such as an arithmetic circuit, a display device and a printing device.

[0003] Therefore, the power supply circuit such as a transformer can be reduced in size by once rectifying and smoothing the commercial alternating current, and then generating and transforming a high-frequency alternating current. Power supply circuits provided are becoming widespread. Further, the power supply input circuit 1 as described above is also used for creating a three-phase alternating current having a desired voltage and frequency as in an air conditioner or the like.

However, the power supply input circuit 1 as described above
In the steady state, the charging / discharging operation of the smoothing capacitor 4 causes the current waveform when viewed from the commercial AC power supply 2 side to be different from the voltage waveform indicated by reference numeral α1 in FIG. It becomes as shown by. That is, when the input voltage indicated by the reference numeral α1 is full-wave rectified by the rectifier circuit 3, the input voltage becomes as indicated by reference numeral α3 in FIG. 22B, and the voltage between the terminals of the smoothing capacitor 4 becomes as indicated by reference numeral α4. Become. Accordingly, the charging current flows only during the period T near the peak value as indicated by the reference numeral α5 with respect to the voltage waveform indicated by the reference numeral α1, which is a sine wave of the commercial power supply frequency, and is viewed from the commercial AC power supply 2 side. The resulting current waveform is as shown by the above-mentioned reference symbol α2.

For this reason, the charging current has a peak value of 5 to 6 times the effective value or more, and a third, fifth, or
Are distorted waveforms in which the harmonics are superimposed. This also causes a problem that reactive power increases. For this reason, regulation of feedback of such harmonic current to the commercial AC power supply 2 side is about to be started.

Therefore, in order to reduce the above-described harmonic current, conventionally, for example, the power consumption on the load side is reduced by 2%.
When the power consumption is less than 00 W, the power supply input circuit 11 shown in FIG. 23 is used, and in a device with large power consumption, the power supply input circuit 21 shown in FIG. 24 is used.

In the power supply input circuit 11, a choke coil 13 is inserted into a power supply line 12 from the commercial AC power supply 2, and the choke coil 13 prevents the return of the harmonic current to the commercial AC power supply 2.

The power supply input circuit 21 is disclosed in Japanese Unexamined Patent Application Publication No.
No. 6485, a step-up chopper type power factor correction circuit 22 is inserted between the rectifier circuit 3 and the smoothing capacitor 4, and the switching operation of the switching element 24 in response to a control signal from the control circuit 23 is performed. By rectifying the electromotive current generated by the choke coil 25 with the diode 26, the period T of the current waveform in FIG. 22 is extended to suppress harmonics and improve the power factor.

[0009]

SUMMARY OF THE INVENTION The power input circuit 11
For example, in a configuration in which 100 W of power can be supplied to the load side, the size required for the choke coil 13 is 4 × 5
× 4 (cm) = 80 (cm ³ ), which causes a problem that the volume and mass of the power supply circuit increase.

Although the power supply input circuit 21 can use a choke coil 25 having a smaller inductance than the choke coil 13, that is, a small one, the control circuit 23 has a complicated structure to synchronize with a voltage waveform. However, there is a problem in that the switching noise of the switching element 24 is fed back to the commercial AC power supply 2 side.

An object of the present invention is to provide a power supply input circuit that can be reduced in size and cost and that generates less noise.

[0012]

According to a first aspect of the present invention, there is provided a power supply input circuit for rectifying an input current from an AC power supply with a rectifier circuit, smoothing the rectified current with a smoothing capacitor, and outputting the rectified current to a load side. , The first and second 2 connected in series with each other and connected in parallel with the smoothing capacitor.
And One of the capacitors, the connection points of one terminal of said first capacitor and a second capacitor, the other terminal and a one and connected Ru resistance of the pair of input ends of the AC power source, the The capacitances C1 and C2 of the first and second capacitors are set to the maximum value of the power consumption on the load side by Pma.
x, the power supply frequency of the AC power supply is f, and the effective value of the output voltage of the AC power supply is Vin, 0.5 ×
Pmax / (2 × f × Vin ² ) to 1.5 × Pmax /
(2 × f × Vin ² ), preferably Pmax / (2 × f
× Vin ² ), and the product value of the capacitances C1 and C2
Is the charging time constant of the first and second capacitors. The resistance value R of the resistor is set to a value corresponding to the capacitance C1, C2.
By contrast, 0.0001 / C1 to 0.001 / C1 or 0.0001 / C2 to 0.001 / C2, preferably 0.0001 / C1 to 0.0004 / C1 or 0.0
001 / C2 to 0.0004 / C2.

The power supply input circuit according to the second aspect of the present invention is configured such that after the input current from the AC power supply is rectified by the rectifier circuit,
In the power supply input circuit and outputting the smoothed by the smoothing capacitor to the load side, and a capacitor having one terminal is connected to one terminal of the smoothing capacitor, one terminal
There the other terminal of the capacitor, and a resistor other terminal that will be connected to either one of the pair of input ends of the AC power source, the capacitance Ca of the capacitor, the power consumption of the load When the maximum value is Pmax, the power supply frequency of the AC power supply is f, and the effective value of the output voltage of the AC power supply is Vin, Pmax / (2 × f × Vin ² )
３3 × Pmax / (2 × f × Vin ² ), preferably 2
× wish to Pmax / (2 × f × Vin 2), said electrostatic Den'yo
The resistance value Ra of the resistor , whose product value with the amount Ca is the charging time constant of the capacitor, is expressed as a relative ratio with the capacitance Ca.
And is selected from 0.0001 / Ca to 0.001 / Ca, preferably from 0.0001 / Ca to 0.0004 / Ca.

[0014] Furthermore the power supply input circuit according to the invention of claim 3, wherein the rectifier circuit is realized by a diode bridge circuit, and detecting means for detecting the power consumption of the load, in response to a detection result of said detecting means, light Switching means for switching the rectifier circuit to half-wave rectification when a load is detected.

In the power supply input circuit according to a fourth aspect of the present invention, the rectifier circuit is realized by a diode bridge circuit, and a detecting means for detecting power consumption of a load; And capacitance changing means for reducing the capacitance of at least one of the first and second capacitors when it is detected that

[0016]

According to the first aspect of the present invention, an input current from an AC power supply such as a commercial AC power supply is rectified by a rectifier circuit including a diode bridge or the like, and then smoothed by a smoothing capacitor, thereby obtaining a DC-DC converter or an inverter. In a power supply input circuit of a capacitor input type for outputting to a load side, a series circuit in which first and second capacitors are connected in series with each other in parallel with the smoothing capacitor is inserted, and the first and second capacitors are connected to each other. A resistor is connected between a connection point of the second capacitor and one of a pair of input terminals of the AC power supply.

Further, the capacitances C1 and C2 of the first and second capacitors are set to the maximum value of the power consumption on the load side by Pm.
ax, the power supply frequency of the AC power supply is f, and the effective value of the output voltage of the AC power supply is Vin, 0.5 × Pma
x / (2 × f × Vin ² ) to 1.5 × Pmax / (2 ×
f × Vin ² ), preferably Pmax / (2 × f × Vi
n ² ).

The product value of the capacitances C1 and C2 is
The resistance value R of the resistor , which is the charging time constant of the first and second capacitors, is expressed as a relative ratio to the capacitances C1 and C2.
In, 0.0001 / C1~0.001 / C1 or 0.
0001 / C2 to 0.001 / C2, preferably 0.0
001 / C1 to 0.0004 / C1 or 0.0001
/ C2 to 0.0004 / C2.

Therefore, the capacitances C1 and C2 of the first and second capacitors correspond to the power consumed on the load side within a half-wave, so that the output power, that is, the load is stable. In this state, for example, when the power supply voltage becomes positive, the first capacitor is charged with a charging current having a waveform whose rise is regulated by a resistor so as to be substantially equal to the voltage between terminals of the smoothing capacitor. When the voltage between the terminals of the first capacitor and the first capacitor becomes higher than the power supply voltage, the charging is stopped, and a load current is supplied from these smoothing capacitor and the first capacitor to the load side. At this time, with respect to the second capacitor, a discharge path is formed on the AC power supply side via the resistor, and the terminal voltage of the first capacitor decreases as the terminal voltage of the first capacitor increases. go.

Thereafter, when the power supply voltage becomes negative, a charging current is first supplied to the second capacitor via a resistor.
The second capacitor is charged together with the smoothing capacitor. At this time, the first capacitor discharges through the resistor.

Therefore, the voltage between the terminals of the first or second capacitor rises in correspondence with the smoothing capacitor. At this time, the second or first capacitor discharges until the voltage between the terminals becomes substantially zero. ing. Therefore, when the polarity of the power supply voltage is switched, the first or second capacitor is charged from the state where the terminal voltage is substantially zero. As a result, the current waveform rises only in the vicinity of the peak value of the voltage waveform with only the smoothing capacitor, so that a harmonic current is generated and the power factor is reduced, whereas the current from the AC power supply flows. The period becomes longer, the generation of the harmonic current is suppressed, and the power factor can be improved.

In addition, the suppression of the harmonic current and the improvement of the power factor can be realized with a simple configuration of two capacitors and one resistor, and the size and cost can be reduced. Since no switching element or the like is used, there is no danger of generating noise.

According to the second aspect of the present invention, an input current from an AC power source such as a commercial AC power source is rectified by a rectifier circuit including a diode bridge and the like, and then smoothed by a smoothing capacitor to obtain a DC-DC converter or the like. In a capacitor input type power supply input circuit configured to output to a load side such as an inverter, a capacitor and a resistor are connected between one terminal of the smoothing capacitor and one of a pair of input terminals of an AC power supply. Connected in series.

Further, the capacitance Ca of the capacitor is
The maximum value of the power consumption on the load side is Pmax, the power supply frequency of the AC power supply is f, and the effective value of the output voltage of the AC power supply is V
When in, Pmax / (2 × f × Vin ² ) 〜3
× Pmax / (2 × f × Vin ² ), preferably 2 × P
Select max / (2 × f × Vin ² ).

The product value of the capacitance Ca and the capacitance
The resistor resistance value Ra to the charging time constant of the capacitor, before
0.0001 / Ca- in relative ratio to the capacitance Ca
0.001 / Ca, preferably 0.0001 / Ca
Choose 0.0004 / Ca.

Therefore, in a steady state in which the load is stable, for example, when the power supply voltage is on the positive side, the charging current of the capacitor is regulated so as to be substantially equal to the voltage between the terminals of the smoothing capacitor by the charging current whose rising is regulated by the resistor. When the voltage between the terminals of the smoothing capacitor and the capacitor becomes higher than the power supply voltage, the charging is stopped, and the load current is supplied from the smoothing capacitor and the capacitor to the load side.

Thereafter, when the power supply voltage becomes negative, a current for discharging is supplied to the capacitor via a resistor, and the capacitor is discharged in response to charging of the smoothing capacitor.

Therefore, a current for charging or discharging is supplied to the capacitor from the rise of the power supply voltage. Therefore, the current waveform rises only near the peak value of the voltage waveform with the smoothing capacitor alone. As a result, the period during which the current from the AC power supply flows becomes longer, the generation of harmonic current can be suppressed, and the power factor can be improved.

Further, according to the invention of claim 3 , the rectifier circuit is realized by a diode bridge circuit,
The power consumption of the load is detected by detecting the voltage between the terminals of the smoothing capacitor by the detecting means, and when the light load is detected, the rectifier circuit is switched to half-wave rectification by the switching means.

Therefore, when the load becomes light, for example, the first and second capacitors are not sufficiently discharged, and the voltage output to the load exceeds the voltage predetermined for the load. In such a case, by switching from full-wave rectification to half-wave rectification,
The charging current to the first and second capacitors and the smoothing capacitor can be suppressed so that the voltage between the terminals of the smoothing capacitor does not exceed the specified voltage.

According to the invention of claim 4, when the light load is detected by detecting the line current of the load line by detecting the line current of the load line by detecting means, the rectifier circuit is constituted by a diode bridge circuit. The capacitance changing means reduces the capacitance of at least one of the first and second capacitors. That is, for example, a switching element is interposed in series with the first or second capacitor, and when the load becomes light, the switching element is opened and the first element is opened.
Alternatively, the second capacitor may be separated, and the capacitance of the first or second capacitor is divided into a plurality of elements, and when the light load is applied, a part of the capacitance is handled. The element may be opened.

As described above, when the load becomes light, the capacitance of the first or second capacitor is reduced, so that the output voltage to the load side does not undesirably increase and falls within the specified voltage. It can be.

[0033]

1 to 3 show a first embodiment of the present invention.
It is as follows if it explains based on.

FIG. 1 is an electric circuit diagram of a power supply input circuit 31 according to a first embodiment of the present invention. This power input circuit 31
Is a so-called capacitor input type power supply input circuit in which an input current from a commercial AC power supply 32 is rectified by a rectifier circuit 33, and then smoothed by a smoothing capacitor C0 and output. The capacitors C1 and C2 and a resistor R are provided. It is a thing.

The rectifier circuit 33 includes diodes D1 and D2 whose anodes are connected to input power lines L1 and L2 from the commercial AC power supply 32, respectively, and whose cathodes are commonly connected to a high-level output power line L3. Are connected to the input power lines L1 and L2, respectively, and are implemented by diode bridges including diodes D3 and D4 whose anodes are commonly connected to the low-level output power line L4. The full-wave rectified output current output from rectifier circuit 33 is smoothed by smoothing capacitor C0 interposed between output power supply lines L3 and L4, and output to the load side. The output currents from the output power supply lines L3 and L4 may be stepped down by a DC-DC converter 34 as shown in FIG. 1 and then supplied to a load 35 such as an arithmetic processing circuit. Then, it may be converted into a high-frequency current and used for lighting a fluorescent lamp or the like, or may be converted into a three-phase alternating current and supplied to an induction motor or the like of an air conditioner.

Between the output power lines L3 and L4, that is, in parallel with the smoothing capacitor C0,
A series circuit of C2 is connected. The capacitor C
A connection point 36 between the first power supply line C1 and the second power supply line C2 is connected to one of the input power supply lines L1 and L2 via a resistor R, in FIG.

According to the present invention, as shown in FIG. 2B, a period T2 in which a current flows per unit cycle T1 with respect to an input voltage waveform from the commercial AC power supply 32 shown in FIG.
Is intended to suppress the generation of harmonic components. First, the capacitors C1, C
The method for determining the capacitance of No. 2 will be described in detail.

The capacitance of the capacitors C1 and C2 is
Energy of the capacitor C1, the C2 is Ru chosen to be consumed in the half-wave. That is , when represented by the same symbols as the reference symbols, the general formula of the energy stored in the capacitor is given by W = (１ ／) CV ² ,
This is transformed to C = 2W / V ^2, and since there are two, C =
W / V ² is obtained. And, the power supply of the commercial AC power supply 32
If the frequency is f, C = (W / V ² )
(1 / 2f). Accordingly, when the maximum value of the power consumption on the load side is Pmax and the effective value of the input voltage from the commercial AC power supply 32 is Vin, 0.5 × Pmax / ( 2 × f × Vin ² ) ≦ C1, C2 ≦ 1.5 × Pmax / (2 × f × Vin ² ) (1), and when the possibility of the load fluctuation is small, preferably , C2 = Pmax / (2 × f × Vin ² ) (2)

Next, the resistor R is a resistor for shaping the waveform of the current flowing on the commercial AC power supply 32 side. The current waveform when the resistance value of the resistor R is 0 is referred to in FIG. This is indicated by the symbol β1. Even if the resistance value of the resistor R is small, the period T2 can be extended by the operation of the capacitors C1 and C2 as described later, as compared with the case where only the smoothing capacitor C0 is used. Since the rise is steep, harmonic components increase. Therefore, the resistance value of the resistor R is determined as follows.

First, as described above, in order to suppress the generation of the harmonic component due to the rise, it is necessary to smooth the current waveform as indicated by reference numerals β2 to β3. Furthermore,
The maximum value Ima of the current when the resistance value of the resistor R is 0
drop amount ΔI from x is as a guide to complete charging within about 5 percent of the maximum value _{Imax, log e 0.05 = -3 ···} (3) Therefore, -3 = -t / CR From (4), CR = t / 3 (5) is obtained.

If the power supply frequency f is 50 Hz, the half cycle T1 of the input current is 10 msec. From the waveform shown in FIG. 6 msec, and the charging period T
3 is the maximum value, which must be within about 3 msec of 1/2 of the period T2, and the minimum value is about 1/10 of an experimental value described later. Thereby, t = 0.3 to 3 msec (6) is obtained. Therefore , in a relative ratio, R = 0.0001
/ C1 to 0.001 / C1 or R = 0.0001 / C
2 to 0.001 / C2 can be obtained. If the resistance value of the resistor R is 0, the input current becomes as shown in FIG.
At the point indicated by reference numeral β1. On the contrary,
As the resistance value is increased, the waveform becomes dull as indicated by reference numerals β2 to β3. However,
If this resistance is too large, the loss will increase, so
Preferably R = 0.0001 / C1 to 0.0004 / C
1 or R = 0.0001 / C2 to 0.0004 / C2
Choose

The power supply input circuit 31 configured as described above
The operation will be described in detail with reference to FIGS. FIG. 3A illustrates a state in which the output voltage of the commercial AC power supply 32 rises at time t1 and exceeds the peak value until time t2.
In FIG. 2, the smoothing capacitor C0 is charged in the current path indicated by reference numerals i1 to i2, the terminal voltage of the smoothing capacitor C0 changes as indicated by reference numeral γ1 in FIG. 2C, and the terminal voltage is substantially equal to that of the smoothing capacitor C0. So that
The capacitor C1 is charged in the current path indicated by reference numerals i1 to i3, and the voltage between its terminals changes as indicated by reference numeral γ2. At this time, reference numerals i1 and i
The load current is supplied through current paths indicated by 4 to i5. Furthermore, the charge in the capacitor C2 is referenced by i6
Is discharged to the side of the commercial AC power supply 32 through the current path indicated by, and the voltage between its terminals changes as indicated by reference numeral γ3.

Next, until the output voltage of the commercial AC power supply 32 decreases and reaches 0, the capacitors C0 and C1 are lower than the output voltage of the commercial AC power supply 32 until time t3, as shown in FIG. Therefore, no current flows from the commercial AC power supply 32, and a load current is supplied from the smoothing capacitor C0 to the load side through a current path indicated by reference numerals i4 to i5 in FIG. 3B. At the same time, the load current is supplied from the capacitor C1 to the load side through the current paths indicated by reference numerals i7 to i5. A current flows from the capacitor C1 to the smoothing capacitor C0 as indicated by reference numerals i7 to i2.
Drop at substantially the same inter-terminal voltage. Also during this time,
The electric charge in the capacitor C2 is discharged to the commercial AC power supply 32 through a current path indicated by reference numeral i6.

From time when the output voltage of the commercial AC power supply 32 becomes 0 or less to time t4 at which the peak on the negative electrode side is passed, as shown in FIG. As load current, and also from reference numerals i11 to i2
Is supplied for charging the smoothing capacitor C0. At this time, the capacitor C2 is charged at a potential substantially equal to that of the smoothing capacitor C0 through the current paths indicated by reference numerals i11 to i12. At this time, the capacitors C1,
Since C2 is connected in series, although the voltage between the terminals of these two terminals tends to increase, the smoothing capacitor C2
Since the load 0 is connected to the load, the capacitor C1 discharges in the current path indicated by reference numeral i13.

Here, when the charge stored in the capacitor C1 is not consumed on the load side,
The output voltage from the series circuit 1 and C2 exceeds the rated input voltage of the DC-DC converter 34 specified on the load side, for example. Therefore, the capacitance of the capacitor C1 is selected as described above. The same applies to the discharge of the capacitor C2 in FIG. 3A, and accordingly, the capacitance of the capacitor C2 is also selected as described above.
Thus, the capacitor C1 is discharged, and the capacitor C2 is charged to a potential substantially equal to that of the smoothing capacitor C0.

Further, the output voltage of the commercial AC power supply 32 is
When the negative electrode starts to rise as shown after time t4, the voltage between the terminals of the capacitors C0 and C2 becomes higher than the output voltage of the commercial AC power supply 32, and accordingly, FIG.
As shown by, the load current flows through the current paths indicated by reference numerals i14 and i4 to i5, and
In the current path shown by, the capacitor C2 is
Charging to 0 is performed.

After the time t5 when the output voltage of the commercial AC power supply 32 becomes positive, the operation after the above-mentioned time t1 is repeated, and the sum of the voltages between the terminals of the series circuit of the capacitors C1 and C2 becomes the terminal of the smoothing capacitor C0. Since the load and the smoothing capacitor C0 are connected to the series circuit, the capacitor C2 is discharged as the capacitor C1 is charged, though it is going to be larger than the inter-voltage.

Therefore, in the power supply input circuit 31 having such a configuration, after the output voltage of the commercial AC power supply 32 starts to rise and before it rises to a voltage sufficient to charge the smoothing capacitor C0, the terminal By charging the capacitor C1 or C2 whose inter-voltage is 0, the output current from the commercial AC power supply 32 is reduced as shown in FIG.
, The output current from the commercial AC power supply 32 is supplied over a long period T2 with respect to the period indicated by the reference numeral T in FIG. Further, the maximum value of the output current can be reduced to, for example, about twice the effective value.

As described above, the power supply input circuit capable of suppressing the feedback of the harmonic current to the commercial AC power supply 32 and improving the power factor is provided by the capacitor 2.
One resistor and one resistor can be realized with a simple, low-cost and compact configuration, and no new problems such as generation of switching noise occur.

It should be noted that, even if a coil having an extremely small inductance is used instead of the resistor R, the reference
Thus, waveform shaping as shown by β2 and β3 can be performed.

In order to simplify the structure, one of the capacitors C1 and C2 is used as a capacitor Ca as in a power input circuit 41a shown in FIG. 4 or a power input circuit 41b shown in FIG. It may be provided. Note that components corresponding to the above-described embodiments are denoted by the same reference numerals. However, in this case, the capacitance of the capacitor Ca is a combined capacitance of C1 + C2, and the resistance value of the resistor Ra needs to have the same time constant t, so that C1 = C2 Is 1/2
Becomes

FIG. 6 is a waveform diagram for explaining the operation of the power supply input circuit 41a, and FIG.
FIG. 3 is an electric circuit diagram for explaining the operation of FIG. FIG. 6 (a)
, K1 is an output voltage waveform that has been full-wave rectified by the rectifier circuit 33, and is therefore represented by a smoothing capacitor C0.
Is as shown by the reference numeral K2.

Therefore, as shown in FIG. 7A, the smoothing capacitor C0 is charged through the current path indicated by reference numerals i1 to i2, and the load current is supplied through the current path indicated by reference numerals i1 and i4 to i5. You. As shown in FIG. 6B, the capacitor Ca is charged from the time t1a when the inter-terminal voltage rises to the time t2a when the voltage exceeds the peak value by a current path indicated by reference numerals i1 to i21. Thereafter, until time t3a when the power supply voltage becomes the negative electrode side, the capacitor Ca is supplied through the current path indicated by reference numeral i22.
Supplies a load current.

From time t3a when the power supply voltage becomes the negative side, as shown in FIG. 7B, the output current from the commercial AC power supply 32 is supplied to the load side through the current path indicated by reference numeral i23. In the current path indicated by the symbol i24, the capacitor C
When the discharge of the capacitor Ca is completed and the discharge of the capacitor Ca is completed, no current flows to the capacitor Ca from the time t4a to a time t5a when the power supply voltage rises on the positive electrode side. Only the load current is supplied through the indicated current path.

Even in the case where only one capacitor Ca is provided, the output voltage of the commercial AC power supply 32 is charged during the period of one polarity, whereas the capacitor Ca is charged during the period of the other polarity. Represents a period T2 during which a current for discharging flows and a current flows on the commercial AC power supply 32 side.
Can be lengthened.

Further, as another embodiment of the present invention,
As shown by the power supply input circuit 51a in FIG. 8 or the power supply input circuit 51b in FIG.
That is, a voltage detection circuit 52 for detecting a voltage between terminals of the smoothing capacitor C0, a control signal generation circuit 53 for generating a control signal when a voltage increase due to a light load is detected from the detection result of the voltage detection circuit 52, Switching means 5 for switching rectifier circuit 33 to half-wave rectification in response to the control signal.
4 may be provided.

FIG. 10 is an electric circuit diagram of a power supply input circuit 51a for explaining a specific circuit configuration of the voltage detection circuit 52, the control signal generation circuit 53 and the switching means 54. The voltage detection circuit 52 includes output power lines L3, L
This is realized by a pair of voltage dividing resistors r1 and r2 interposed between the four resistors.

The control signal generating circuit 53 includes a voltage detecting transistor Tr1 for detecting a voltage at a connection point 55 of the voltage dividing resistors r1 and r2, a transistor Tr2 for inverting the detection result, and resistors r3 and r4. It is comprised including. The base of the transistor Tr1 is connected to the connection point 55, and the collector is a resistor r for pull-up.
3 and to the high-level output voltage line L3 and to the base of the transistor Tr2. Further, the emitters of the transistor Tr1 and the transistor Tr2 are connected to a low-level output power supply line L4. A control signal is output from the collector of the transistor Tr2 via the resistor r4.

The switching means 54 includes a switching transistor Tr3 interposed between the cathode of the diode D1 and the high-level output power supply line L3, and receives the control signal and controls the transistor Tr3. And a transistor Tr4.

When the output voltage of the smoothing capacitor C0 is a predetermined voltage, for example, when the effective value of the rated input voltage of the DC-DC converter 34 is 100 V, the peak value becomes 1
At 41 V or less, the transistor Tr1 shuts off the voltage at the connection point 55, whereby the base of the transistor Tr2 becomes high level via the pull-up resistor r3, and the transistor Tr2 conducts. The control signal output via r4 becomes low level. Therefore, the transistor Tr4 is turned on, the base current of the transistor Tr3 is supplied, the transistor Tr3 is turned on, and the capacitor C is connected via the diode D1.
A full-wave rectification state in which charging current can be supplied to 0 and C1.

On the other hand, the load becomes light, the charges in the capacitors C1 and C2 are not sufficiently consumed, and the power supply line L
When the voltage of the transistor 3 rises, the base of the transistor Tr1 goes high, the transistor Tr1 conducts, and bypasses the base current supplied to the transistor Tr2. As a result, the transistor Tr2 is cut off, the base current of the transistor Tr4, that is, the base current of the transistor Tr3 is cut off, the supply of the charging current via the diode D1 is stopped, and the rectifier circuit 33 enters a half-wave rectification state.

FIGS. 11 and 12 are waveform diagrams for explaining the operation of the power supply input circuit 51a accompanying the switching of the rectification state as described above. FIG.
Indicates light load. In addition, assuming that C1 = C2, Pmax
= 2 × f × C1 × Vin ² .

At a steady load, in FIG. 11A, when the voltage between the terminals of the smoothing capacitor C0 indicated by reference numeral H1 is equal to or lower than the rated input voltage of the DC-DC converter 34 indicated by reference numeral H2. For the full-wave rectified waveform indicated by H3, the voltage between the terminals of the capacitors C1 and C2 is as shown in FIG.
As shown by reference numerals H5 and H6 in FIG. 6B, the waveform is similar to the waveform shown in FIG. 6B. Therefore, the current flowing from the rectifier circuit 33 is as indicated by reference numeral H4 in FIG.

On the other hand, when the load is light, as shown in FIG. 12 (a), the voltage between the terminals of the smoothing capacitor C0 shown by the reference numeral H11 may exceed the rated input voltage shown by the aforementioned reference numeral H2. And During the period from time t11 to t12, the transistor Tr3 is shut off to be in a half-wave rectification state,
The capacitor C shown by reference numeral i6 in FIG.
2 is cut off, and the voltage between the terminals of the capacitor C2 is maintained as indicated by reference numeral H14 in FIG. On the other hand, the voltage between the terminals of the capacitor C1 stops increasing at the time t11, and
A load current flows from 0 and C1, and the voltage between the terminals of the capacitor C1 gradually decreases as indicated by reference numeral H13. 12A, the current waveform when viewed from the rectifier circuit 33 on the load side is indicated by reference numeral H1 in FIG.
As shown in FIG.

At time t12, the series capacitor C
When the sum of the voltages between the terminals of the terminals C1 and C2 becomes equal to or lower than the rated input voltage, the transistor Tr3 is turned on and the polarity of the power supply voltage is switched at time t13.
2 is higher than the output voltage of the rectifier circuit 33,
The charging of the capacitor C2 is started from the time t14 when both are reversed. Correspondingly, the capacitor C1
Is started.

When it is detected that the load is less than 1/2 of the maximum value Pmax of the light load, for example, the power consumption of the load, by switching to half-wave rectification, the voltage between the terminals of the capacitors C1 and C2 is reduced. It is possible to prevent the sum from becoming higher than the rated input voltage of the load.

Further, the power supply input circuit 6 shown in FIG.
1a and the power input circuit 61b shown in FIG.
At light load, charging may be suppressed by opening one of the capacitors C1 and C2. That is, in these power supply input circuits 61a and 61b, a load current detection circuit 62 for detecting a line current of the load line L5 is provided on a load line L5 from the DC-DC converter 34 to the load 35, and the load current detection circuit 62 For example, when it is detected that the load current has become 以下 or less of the rated current, the control signal generation circuit 63 opens the switch 64.
The switch 64 is provided for the capacitor C1 in the power input circuit 61a, and is provided for the capacitor C2 in the power input circuit 61b.

In such a configuration, the change in the voltage between the terminals of C2 in the capacitor which is not opened by the switch 64 at the time of light load, for example, in the power supply input circuit 61a shown in FIG. 13, is shown in FIG. 6B. The waveform is similar to the waveform, and in this case, it is possible to cope with a change in load.

The power input circuit 51a or 51
The configuration of b and the configuration of the power input circuit 61a or 61b may be arbitrarily combined to form, for example, a power input circuit 71a shown in FIG. 15 and a power input circuit 71b shown in FIG. This allows the load to be, for example, 1
Even when changing in a plurality of stages, such as / 2 and 1/4, it is possible to optimally cope with each of them.

Further, power supply input circuit 8 shown in FIG.
1a and the power input circuit 81b shown in FIG.
With the opening of either one of the capacitors C1 or C2, the capacitance of the remaining capacitor C2 or C1 may be reduced. That is, capacitors C2 and C1 are respectively connected to partial capacitors C2a and C3 and C1a and C1
3 and the load is 1 / the maximum value Pmax.
At a time point when the voltage becomes 2 or less, the control signal generating circuit 63 shuts off the switch 64, and when the voltage becomes 1/4 or less, the switch 8
2, the partial capacitor C3 may be opened. In this case, the partial capacitors C2a, C1a and C3 are set, for example, to be equal to each other, that is, set to a capacitance half of that of the capacitors C2 and C1.

Further, the configuration of the power supply input circuits 81a and 81b may be arbitrarily added to the power supply input circuit 51a or 51b, for example, so that the power supply input circuit 9 shown in FIG.
1a and the power supply input circuit 91b shown in FIG. 20 so as to cope with more minute load fluctuations.

[0072]

According to the first aspect of the present invention, a power supply input circuit includes:
As described above, the first and second capacitors are connected in parallel with the smoothing capacitor.
Are connected in series with each other, and a connection point between the connection point and one of the input terminals of the AC power supply is connected by a resistor, and the capacitances C1 and C2 of the capacitors are changed. , 0.5 × Pmax / (2 × f × Vi
n ² ) to 1.5 × Pmax / (2 × f × Vin ² ), preferably Pmax / (2 × f × Vin ² ), and the resistance value R of the resistor is 0.0001 / C1 to 0.001. / C1
Or 0.0001 / C2 to 0.001 / C2, preferably 0.0001 / C1 to 0.0004 / C1 or 0.0001 / C2 to 0.0004 / C2.

Therefore, the power supply voltage has one polarity,
When one capacitor, for example, the first capacitor is being charged, the other capacitor, that is, the second capacitor, discharges, and as soon as the polarity of the power supply voltage is switched, a charging current flows to the other capacitor. . This allows the charging current to flow only near the peak value of the power supply voltage with only the smoothing capacitor,
The period during which the current flows as viewed from the AC power supply side can be lengthened, the generation of harmonic current can be suppressed, and the power factor can be improved.

Further, such suppression of the harmonic current and improvement of the power factor can be realized with a simple configuration of two capacitors and one resistor, and the size and cost can be reduced. Since no switching element or the like is used, there is no danger of generating noise.

In the power supply input circuit according to the second aspect of the present invention, as described above, a series connection of a capacitor and a resistor is provided between one terminal of the smoothing capacitor and one of the input terminals of the AC power supply. By interposing a circuit, the capacitance Ca of the capacitor is calculated as Pmax / (2 × f × Vin ² ) to 3 ×
Pmax / (2 × f × Vin ² ), preferably 2 × Pm
ax / (2 × f × Vin ² ), and the resistance value Ra of the resistor
Is selected to be 0.0001 / Ca to 0.001 / Ca, preferably 0.0001 / Ca to 0.0004 / Ca.

Therefore, when the power supply voltage is on one polarity side, for example, the capacitor is charged corresponding to the smoothing capacitor, and when it is switched to the other polarity side, the capacitor is discharged immediately after the switching. Will flow. In this way, the period during which the current flows from the side of the AC power supply can be lengthened, the generation of harmonic current can be suppressed, and the power factor can be improved.

Furthermore, the power supply input circuit according to the third aspect of the present invention switches the rectifier circuit to half-wave rectification when the load becomes light as described above.

Therefore, when the load becomes light and, for example, the first and second capacitors may not be sufficiently discharged, the charging current to the first and second capacitors and the smoothing capacitor is reduced. Thus, the voltage between the terminals of the smoothing capacitor can be suppressed within a specified voltage.

In the power supply input circuit according to the fourth aspect of the present invention, when the light load is detected as described above, the capacitance of at least one of the first and second capacitors is determined. Decrease.

Therefore, as in the case described above, the charging current can be suppressed, and the voltage between the terminals of the smoothing capacitor can be suppressed within the above-mentioned specified voltage.

[Brief description of the drawings]

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

FIG. 2 is a waveform chart for explaining an operation of the power supply input circuit shown in FIG. 1;

FIG. 3 is an electric circuit diagram for explaining an operation of the power supply input circuit shown in FIG. 1;

FIG. 4 is an electric circuit diagram of a power supply input circuit according to a second embodiment of the present invention.

FIG. 5 is an electric circuit diagram of a power supply input circuit according to a third embodiment of the present invention.

FIG. 6 is a waveform chart for explaining the operation of the power supply input circuit shown in FIG. 4;

FIG. 7 is an electric circuit diagram for explaining an operation of the power supply input circuit shown in FIG. 4;

FIG. 8 is a block diagram showing an electrical configuration of a power supply input circuit according to a fourth embodiment of the present invention.

FIG. 9 is a block diagram illustrating an electrical configuration of a power supply input circuit according to a fifth embodiment of the present invention.

10 is an electric circuit diagram showing a specific configuration of a voltage detection circuit, a control signal generation circuit, and a switching unit in the power supply input circuit shown in FIG.

FIG. 11 is a waveform chart for explaining the operation of the power supply input circuit shown in FIG. 8 at the time of a steady load.

12 is a waveform chart for explaining an operation of the power supply input circuit shown in FIG. 8 at a light load.

FIG. 13 is a block diagram showing an electrical configuration of a power supply input circuit according to a sixth embodiment of the present invention.

FIG. 14 is a block diagram illustrating an electrical configuration of a power supply input circuit according to a seventh embodiment of the present invention.

FIG. 15 is a block diagram showing an electrical configuration of a power supply input circuit according to an eighth embodiment of the present invention.

FIG. 16 is a block diagram showing an electric configuration of a power supply input circuit according to a ninth embodiment of the present invention.

FIG. 17 is a block diagram showing an electrical configuration of a power supply input circuit according to a tenth embodiment of the present invention.

FIG. 18 is a block diagram showing an electrical configuration of a power supply input circuit according to an eleventh embodiment of the present invention.

FIG. 19 is a block diagram showing an electrical configuration of a power supply input circuit according to a twelfth embodiment of the present invention.

FIG. 20 is a block diagram showing an electrical configuration of a power supply input circuit according to a thirteenth embodiment of the present invention.

FIG. 21 is an electric circuit diagram of a conventional power supply input circuit.

FIG. 22 is a waveform chart for explaining a problem of the power supply input circuit shown in FIG. 21;

FIG. 23 is an electric circuit diagram of a first conventional power supply input circuit for solving the problem of the power supply input circuit shown in FIG. 21;

FIG. 24 is an electric circuit diagram of a second conventional power supply input circuit for solving the problem of the power supply input circuit shown in FIG. 21;

[Explanation of symbols]

 31 power input circuit 32 commercial AC power supply 33 rectifier circuit 34 DC-DC converter 35 load 41a power input circuit 41b power input circuit 51a power input circuit 51b power input circuit 52 voltage detection circuit (detection means) 53 control signal generation circuit 54 switching means 61a power input circuit 61b power input circuit 62 load current detection circuit (detection means) 63 control signal generation circuit 64 switch (capacitance changing means) 71a power input circuit 71b power input circuit 81a power input circuit 81b power input circuit 82 switch ( Capacitance changing means) 91a Power input circuit 91b Power input circuit C0 Smoothing capacitor C1 Capacitor C2 Capacitor Ca capacitor C1a Capacitor C2a Capacitor C3 Capacitor R Resistance Ra Resistance

Claims (4)

(57) [Claims] 1. A power supply input circuit for rectifying an input current from an AC power supply with a rectifier circuit, smoothing the rectified current with a smoothing capacitor, and outputting the rectified current to a load side, wherein the power supply input circuit is connected in series with each other and connected in parallel with the smoothing capacitor. A first terminal connected to a connection point between the first capacitor and the second capacitor, and a second terminal connected to one of a pair of input terminals of the AC power supply. Capacitances C1 and C2 of the first and second capacitors.
When the maximum value of the power consumption on the load side is Pmax, the power supply frequency of the AC power supply is f, and the effective value of the output voltage of the AC power supply is Vin, 0.5 × Pmax /
(2 × f × Vin ² ) to 1.5 × Pmax / (2 × f ×
Vin ² ), and the product value of the capacitances C1 and C2 is equal to the first and second capacitance values.
The resistance value R of the resistor, which becomes the charging time constant of the capacitor
Is 0.000 as a relative ratio to the capacitances C1 and C2.
1 / C1 to 0.001 / C1 or 0.0001 / C2
A power supply input circuit characterized in that the power supply input circuit is selected to be 0.001 to C2 / C2. 2. A power supply input circuit for rectifying an input current from an AC power supply with a rectifier circuit, smoothing the rectified current with a smoothing capacitor, and outputting the rectified current to a load side, wherein one terminal is connected to one of the terminals of the smoothing capacitor. And a resistor having one terminal connected to the other terminal of the capacitor and the other terminal connected to one of a pair of input terminals of the AC power supply. When the maximum value of the power consumption on the load side is Pmax, the power supply frequency of the AC power supply is f, and the effective value of the output voltage of the AC power supply is Vin, Pmax / (2 × f × Vin ² ) to 3 x Pm
ax / (2 × f × Vin ² ), and the resistance value Ra of the resistor whose product value with the capacitance Ca is the charging time constant of the capacitor is represented by a relative ratio with the capacitance Ca, A power supply input circuit selected from 0.0001 / Ca to 0.001 / Ca. 3. The rectifier circuit is realized by a diode bridge circuit, a detecting means for detecting power consumption of a load, and a light load is detected in response to a detection result of the detecting means. 2. The power supply input circuit according to claim 1, further comprising switching means for switching the rectifier circuit to half-wave rectification. 4. The rectifier circuit is realized by a diode bridge circuit, and detecting means for detecting the power consumption of the load; responding to the detection result of the detecting means, when it is detected that the load becomes light, 4. The power supply input circuit according to claim 1, further comprising: capacitance changing means for reducing capacitance of at least one of the first and second capacitors.