JPH05344732A - Switching regulator type power supply - Google Patents

Abstract

(57) [Summary] (Modified) [Purpose] It is possible to charge the output capacitor at a low input voltage and level the charging current of the output capacitor to reduce the crest factor and prevent the device from becoming large. Provided is a switching regulator type power supply device that can be used. A main switching regulator A that obtains a predetermined output voltage from an AC power supply connected to a rectifier circuit, and a low voltage that operates at an input voltage lower than the peak voltage of an AC power supply connected to a rectifier circuit to obtain a predetermined output voltage. An AC power supply includes input voltage operation switching regulators B and C, a main switching regulator and a rectifying element 9 connected to the output side of the low input voltage operation switching regulator, and an output capacitor 10 commonly connected via the rectifying element 9. The output capacitor 10 is charged from the low input voltage operation switching regulators B and C in a phase in which the input voltage is low.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a rectifying / smoothing circuit in which a primary winding of a transformer and a switching element are connected in series on the output side of a rectifying circuit and a rectifying / smoothing circuit is connected to a secondary winding of the transformer. The present invention relates to a switching regulator type power supply device that includes a switching regulator that detects a circuit output voltage and controls a switching element, and that supplies a stabilized DC output to a load from a rectifying and smoothing circuit.

[0002]

2. Description of the Related Art FIG. 3 is a diagram showing a configuration example of a conventional rectifying and smoothing type DC power supply device, FIG. 4 is a diagram showing a configuration example of a conventional switching regulator type DC power supply device, and FIG. 5 is an AC input and a load. It is a figure which shows the waveform of a voltage, and an input current waveform.

In the rectifying and smoothing type DC power supply device, as shown in FIG. 3, a rectifying circuit composed of a rectifier 22 and a smoothing capacitor 23 are connected to the secondary side of the input transformer 21, and the input transformer 21 is connected by these rectifying and smoothing circuits. The secondary side AC output of (1) is rectified and smoothed, and the smoothed DC voltage as shown by the load voltage V _L of FIG. 5A obtained between the terminals of the smoothing capacitor 23 is supplied to the load 24.

[0004] In contrast, in the switching regulator type DC power supply, transformer T _1, as shown in FIG. 5
The primary winding is connected in series with the switching transistor 33 and connected to the output side of the rectifying circuit 31 and the input capacitor 32, and the rectifying / smoothing circuit 34 is connected to the secondary winding. Then, the voltage obtained in the output capacitor 35 of the rectifying / smoothing circuit 34 is detected by the voltage dividing circuit 39, compared with the reference voltage 40 by the error amplifier 36, and the control circuit 3 is output according to the output.
By controlling the transistor 33 via the control transistor 38 and the pulse transformer T ₂ at 7, the stabilized DC output is supplied to the load.

As described above, the DC power supply device that obtains a DC output from an AC input requires a rectifier circuit, and after that, a capacitor is connected for smoothing and the DC output smoothed by the capacitor is supplied to the load. It is configured to do. This is called the capacitor input type rectifying and smoothing method.

[0006]

However, in the DC power supply device having the capacitor for smoothing the output as described above, there is a problem that a large inrush current flows near the peak of the AC input in order to charge the capacitor. is there. FIG. 6 is a diagram for explaining the crest factor of the input current, and FIG. 7 is a diagram for explaining the influence on the entire power supply equipment of the capacitor input type rectifying and smoothing system.

That is, the smoothing capacitor 23 shown in FIG.
In the input capacitor 32 shown in FIG. 4 and FIG. 5, the charging from the AC power source and the discharging to the load are repeatedly performed for each half wave of the AC voltage through the rectifying circuit as shown in FIG. Therefore, when the smoothing capacitor 23 and the input capacitor 32 are charged, an input current as shown in FIG. 5B flows from the AC power supply. Moreover, this input current instantaneously becomes a large value (rush current), and the crest factor (crest factor) becomes large.

This crest factor is expressed by the peak value of the crest divided by the effective value. As shown in FIG. 6, the current is i (t), the cycle is T,
If the peak value is i _peak , Calculated by The value of the crest factor is 1 in the case of direct current and 1.414 in the case of sine wave, while it becomes 2.3 to 3.5 in the above-mentioned capacitor input type rectifying and smoothing method.

In the power supply circuit of the capacitor input type rectifying and smoothing system as described above, the increase of the crest factor means that a large current momentarily flows to the DC power supply side from the AC power distribution side which supplies power to the DC power supply. Is. Therefore, as shown in FIG. 7, the input transformer 21 of the DC power supply device
In addition, there are problems that heating and loss increase due to saturation of the magnetic circuit of the power supply transformer 25 installed in the power receiving system, and that the power supply cable 26 vibrates or growls due to the force of the inrush current.

Therefore, in order to avoid the above-mentioned state, it is necessary to make the power supply transformer 25 and the cable 26 have a larger capacity for the supplied effective power.
As a result, the equipment becomes larger in capacity and larger than necessary, and the equipment cost also increases.

The present invention has been made to solve the above-mentioned problems, and makes it possible to charge the output capacitor even at a low input voltage and level the current flowing into the output capacitor, thereby reducing the crest factor and reducing the device's crest factor. An object of the present invention is to provide a switching regulator type power supply device capable of preventing an increase in size.

[0012]

To this end, according to the present invention, a primary winding of a transformer and a switching element are connected in series on the output side of a rectification circuit, and a rectification smoothing circuit is connected to the secondary winding of the transformer. A switching regulator type power supply device that is provided with a switching regulator that detects an output voltage of the rectifying and smoothing circuit and controls a switching element, and that supplies a stabilized DC output to the load from the rectifying and smoothing circuit. Main switching regulator that obtains a specified output voltage from the connected AC power supply, low input voltage operation switching regulator that operates with an input voltage that is lower than the peak voltage of the AC power supply connected to the rectifier circuit, and main Rectifier connected to output side of switching regulator and low input voltage operation switching regulator And an output capacitor commonly connected via the rectifying element, the output capacitor is configured to be charged from the low input voltage operation switching regulator in a phase where the input voltage of the AC power supply is low. is there.

Furthermore, a plurality of low input voltage operation switching regulators having different operation voltages are provided, or a switching circuit is connected in series to the input side of the low input voltage operation switching regulator, and the input voltage of the AC power supply is detected to switch the switching circuit. And an input control circuit for controlling the output voltage is provided, and the input control circuit is configured to turn on the switching circuit at a phase where the input voltage of the AC power supply is low to charge the output capacitor from the low input voltage operation switching regulator. It is a thing.

[0014]

In the switching regulator type power supply device of the present invention, the main switching regulator that obtains a predetermined output voltage from the AC power supply connected to the rectifier circuit and the input voltage lower than the peak voltage of the AC power supply connected to the rectifier circuit operate. And a rectifying element connected to the output side of the main switching regulator and the low input voltage operating switching regulator, and an output capacitor commonly connected via the rectifying element. Therefore, the output capacitor can be charged from the low input voltage operation switching regulator even when the AC power supply is in the low voltage phase. Therefore, the main switching regulator and the low input voltage operation switching regulator are connected in parallel to the output capacitor via the rectifying element, and the input control circuit turns on the switching circuit in the phase where the input voltage of the AC power supply is low to operate the low input voltage. By charging the output capacitor from the switching regulator, the current flowing into the output capacitor can be leveled and the crest factor can be reduced.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an embodiment of a switching regulator type power supply device of the present invention, and FIG. 2 is a diagram for explaining the operation of the switching regulator type power supply device of the present invention. In the figure, 1 is a rectifier circuit, 2 is a main transistor,
3 is a rectifying / smoothing circuit, 4 is a voltage detection circuit, 5 is a reference power supply,
6 is an error amplifier, 7 is a control circuit, 8 is a control transistor, 9 is a diode, 10 is an output capacitor, 11 and 1
2 is a switching circuit, 13 is an input control circuit, T ₁ is a transformer, T ₂ is a pulse transformer, A is a main switching regulator, and B and C are low input voltage operation switching regulators.

In FIG. 1, the low input voltage operation switching regulator B operates at a medium input voltage higher than C,
Main switching regulator A is a switching regulator having the same structure further work close high input voltage to a peak higher than the AC input, the transformer T ₁
The input operating voltage varies depending on the winding ratio and the setting of the control circuit. That is, in a phase where the AC input is a low input voltage, only a predetermined output voltage is obtained from the low input voltage operation switching regulator C, and a predetermined output voltage is obtained from the low input voltage operation switching regulator B and the main switching regulator A. Absent. When the phase of the medium input voltage is reached, the predetermined output voltage is obtained even in the low input voltage operation switching regulator B, and the predetermined output voltage is also obtained in the main switching regulator A only after the high voltage input close to the peak of the AC input. become.
The low input voltage operation switching regulators B and C are connected to an AC power source through the switching circuits 11 and 12, and the switching circuit 12 is connected in a phase where the input voltage is low.
Is turned on, and the switching circuit 12 is turned on at a higher phase. The input control circuit 13 is
The voltage of the AC input is detected, and the switching circuits 11 and 12 are turned on / off based on the detection result.

In each switching regulator, an AC input is supplied to the rectifier circuit 1, the primary winding of the transformer T ₁ and the switching main transistor 2 are connected in series on the output side of the rectifier circuit 1, and the secondary winding thereof is connected. An output capacitor 10 is connected via a rectifying / smoothing circuit 3 and a diode 9. Then, the output side of the rectifying / smoothing circuit 3 is connected to a voltage detection circuit 4 composed of a resistance voltage dividing circuit, and the control system of the main transistor 2 includes a pulse transformer T ₂ , a control transistor 8, a control circuit 7, and an error amplifier 6. , The reference power source 5 and the like. The error amplifier 6 compares and amplifies the detection voltage of the voltage detection circuit 4 and the reference voltage of the reference power supply 5, and the control circuit 7 controls the output side of the rectifying / smoothing circuit 3 that is comparatively amplified by the error amplifier 6. The control transistor 8 is turned on / off according to an error signal between the detected voltage and the reference voltage. The main transistor 2 is controlled via the pulse transformer T ₂ according to the on / off state of the control transistor 8.

As described above, in the switching regulator type power supply device of the present invention, an input capacitor is not connected to the output side of the rectifying circuit 1 connected to the input side of the switching regulator, and the capacitor of the rectifying / smoothing circuit 3 has a small capacity. Use the one. Then, by the input control circuit 13, the switching circuit 12 is turned on at the low voltage phase of the AC input to charge the output capacitor 10 from the low input voltage operation switching regulator C only at the low voltage phase, and the switching circuit 11 is The output capacitor 10 is charged from the low input voltage operation switching regulator B when the input voltage rises by turning on to a higher middle input voltage phase. When the AC input further approaches the peak, the switching circuits 11 and 12 are turned off, and the output capacitor 10 is charged from the main switching regulator A that operates at a high input voltage. Therefore, in the vicinity of the peak of the AC input that charges the output capacitor 10 from the main switching regulator A, the inrush current at the time of charging the output capacitor 10 can be suppressed by the amount that is previously charged by the low input voltage operation switching regulators C and B. it can.

An outline of the operation of the switching regulator type power supply device will be described with reference to FIG. That is, with respect to the AC input having the voltage waveform v _i as shown in FIG. 2A, the input control circuit 5 outputs the voltages V _C and V
Detect _B. Then, as shown in (b), the switching circuit 11 is turned on at a phase where the AC input is lower than the voltage V _C and turned off when the AC input becomes higher than that, and the switching circuit 12 is turned on at a phase lower than the voltage V _B. Turn off when it gets higher. Therefore, the charging current of the output capacitor 10 initially flows from the low input voltage operation switching regulator C, and when it reaches T ₁ , the switching circuit 1
Since 1 is turned off, it flows from the low input voltage operation switching regulator B. Further, since the switching circuit 12 is turned off at T ₂ , the current flows from the main switching regulator A.

Therefore, the input current can be a leveled input current waveform as shown by the solid line in contrast to the waveform flowing in the case of only the main switching regulator A as shown by the dotted line in FIG. ..

The present invention is not limited to the above embodiment, but various modifications can be made. For example, in the above-described embodiment, the switching circuits 11 and 12 are connected to the low input voltage operation switching regulators B and C, respectively, and the input control circuit 13 detects the input voltage to perform on / off control. The circuit may be omitted and the switching may be automatically performed by setting the reference voltage of each switching regulator. That is, the reference power source 5 is set so that B is higher than the switching regulator C and A is higher than B, and when the input voltage becomes, for example, V _C or more shown in FIG. The output voltage set by is obtained and the input voltage is V
_If the output voltage set in the reference power source 5 is obtained from the switching regulator A when the voltage exceeds _B , the charging circuit can be automatically switched by the diode 9 according to the input voltage.

Further, the reference power source is provided to control the output voltage by comparing it with the output voltage. However, such a voltage control system is omitted and the switching regulator is configured to convert an AC input into a DC output in a constant control mode. Alternatively, the voltage control system may be provided only in the main switch regulator.

Further, the switching regulator for converting an AC input into a DC output has been described. However, a capacitor input type rectifying and smoothing system for obtaining a DC output by rectifying and smoothing from AC-DC-AC, DC-AC-DC, and other AC. It goes without saying that the present invention can be applied to all power supply devices adopting. In addition, switching regulators of the same configuration with different operating voltages were connected in parallel to switch according to the voltage phase.However, from another power system, the switching capacitors were connected in parallel to the output capacitor, and the AC input peak The charging current may be supplied to the output capacitor at low voltage phases near the rising and falling edges on both sides. In this case, the phase at which the switching circuit is turned on may be set in advance, or the phase may be controlled according to the voltage of the output capacitor.

[0024]

As is apparent from the above description, according to the present invention, switching regulators that sequentially operate from a low input voltage are connected in parallel, and an output capacitor is connected from a low input voltage according to the voltage phase of an AC input. Since charging is performed, the crest factor of the input current can be reduced. Therefore, the current capacity of the power supply transformer of the power supply system can be reduced, and heat generation and efficiency can be reduced. In addition, vibration and roar of the power supply cable can be reduced, and the power supply device can be made compact and lightweight.

[Brief description of drawings]

FIG. 1 is a diagram showing one embodiment of a switching regulator type power supply device of the present invention.

FIG. 2 is a diagram for explaining the operation of the switching regulator type power supply device of the present invention.

FIG. 3 is a diagram showing a configuration of a conventional rectifying and smoothing type DC power supply device.

FIG. 4 is a diagram showing a configuration example of a conventional switching regulator type DC power supply device.

FIG. 5 is a diagram showing waveforms of an AC input, a load voltage, and an input current waveform.

FIG. 6 is a diagram for explaining a crest factor of an input current.

FIG. 7 is a diagram for explaining the influence of the capacitor input type rectifying and smoothing system on the entire power supply equipment.

[Explanation of symbols]

1 ... Rectifier circuit, 2 ... Main transistor, 3 ... Rectifier smoothing circuit, 4 ... Voltage detection circuit, 5 ... Reference power supply, 6 ... Error amplifier, 7 ... Control circuit, 8 ... Control transistor, 9 ... Diode, 10 ... Output capacitor , 11 and 12 ... Switching circuit, 13 ... Input control circuit, T ₁ ... Transformer, T ₂ ...
Pulse transformer, A ... Main switching regulator, B and C ... Low input voltage operation switching regulator

Claims (4)

[Claims] 1. A primary winding of a transformer and a switching element are connected in series on the output side of the rectifying circuit, and a rectifying and smoothing circuit is connected to the secondary winding of the transformer to detect the output voltage of the rectifying and smoothing circuit. A switching regulator type power supply device that is configured to supply a stabilized DC output from a rectifying / smoothing circuit to a load by using a switching regulator that controls a switching element by a predetermined output voltage from an AC power supply connected to the rectifying circuit. Of the main switching regulator, the main switching regulator and the low input voltage operating switching regulator, which operates at an input voltage lower than the peak voltage of the AC power supply connected to the rectifier circuit to obtain a predetermined output voltage. Rectifying element connected to the output side, and common connection via the rectifying element A switching regulator type power supply device characterized in that the output capacitor is configured to be charged from a low input voltage operation switching regulator at a phase where the input voltage of the AC power supply is low. 2. The switching regulator type power supply device according to claim 1, further comprising a plurality of low input voltage operation switching regulators having different operation voltages. 3. A switching circuit is provided in series on the input side of a low input voltage operation switching regulator, and an input control circuit for detecting the input voltage of the AC power supply and controlling the switching circuit is provided. The input control circuit inputs the AC power supply. 2. The switching regulator type power supply device according to claim 1, wherein the switching circuit is turned on in a low voltage phase to charge the output capacitor from the low input voltage operation switching regulator. 4. A primary winding of a transformer and a switching element are connected in series on the output side of the rectifying circuit, and a rectifying / smoothing circuit is connected to the secondary winding of the transformer to supply a DC output to the load from the rectifying / smoothing circuit. In the switching regulator type power supply device configured as described above, a main switching regulator that obtains a predetermined DC output from an AC power supply, a low input voltage operation switching regulator that obtains a higher output voltage for the same input voltage as the main switching regulator, and a main switching A rectifier element connected to the output side of the regulator and the low input voltage operation switching regulator, an output capacitor commonly connected via the rectifier element, a switching circuit connected in series to the input side of the low input voltage operation switching regulator, and Detects the input voltage of the AC power supply and switches And an input control circuit for controlling the switching circuit, wherein the input control circuit is configured to turn on the switching circuit in a phase where the input voltage of the AC power supply is low to charge the output capacitor from the low input voltage operation switching regulator. Switching regulator type power supply device.