JPH05292736A - Dc power source - Google Patents

Abstract

PURPOSE:To alleviate a voltage load of a chopper, to reduce a ripple, to further synchronize a chopping operation with an AC power source and to simplify a circuit by superposing a voltage part to be intermittently conducted by chopping on a constant voltage part under a chopper control and applying it to a load. CONSTITUTION:A first DC power source is formed of a first transistor 11 and a first rectifier 13. A second DC power source is composed of a second transformer 12 and a second rectifier 14. An AC power source 2 is connected to the first DC power source and the second DC power source. Then, an output voltage of the rectifier 14 is applied to a load 6 as a constant voltage part by an operation of a diode 15, and an output voltage of the rectifier 13 is applied to the load 6 by chopping by a chopper 5. Accordingly, a value obtained by superposing both the voltages is applied to the load 6. Thus, the chopper 5 may switch a low DC voltage, and a ripple of a DC flowing to the load 6 is reduced. Accordingly, a smoothing circuit becomes a small capacity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC power supply device having a chopper for controlling a DC current supplied to a load.

[0002]

2. Description of the Related Art FIG. 4 is a circuit diagram showing a conventional example of a DC power supply device having a chopper for controlling a DC current supplied to a load. In FIG. 4, the AC power from the AC power supply 2 is transformed into a desired voltage by the transformer 3 and then converted into DC power by the rectifier 4. If the load 6 is, for example, a field winding of a DC motor, the rotation speed of the DC motor can be controlled by changing the current flowing through this field winding. Therefore, the chopper 5 is inserted between the rectifier 4 and the load 6 so that the current flowing to the load 6 can be changed, and the conduction ratio α of the chopper 5 is changed. However, in FIG. 4, a smoothing circuit for absorbing / removing the ripple included in the DC power output by the rectifier 4, and a smoothing circuit for absorbing / removing the ripple included in the DC power output by the chopper 5. Illustration of a circuit, a reactor, a freewheel diode and the like attached to the chopper 5 is omitted.
Further, as the chopper 5, only the transistor as the semiconductor switch element is shown.

FIG. 5 is an operation waveform diagram showing the operation of the conventional circuit shown in FIG. 4. FIG. 5 shows changes in the voltage applied to the load 6, and FIG. 5 shows changes in the current flowing through the load 6. Each represents. When the chopper 5 operates to turn on / off the DC circuit, the voltage waveform applied to the load 6 is as shown in FIG.
As shown in. Here, T represents the time of one cycle of the ON / OFF operation of the chopper 5 and t represents the ON time, so that the conduction ratio α = t / T. Further, the ON / OFF operating frequency f = 1 / T. In the figure, E is the output voltage of the rectifier 4.

If the load 6 is composed only of resistors and the inductance component is zero, the current waveform flowing through this load 6 is the same as the voltage waveform shown in FIG. Since the magnetic winding etc.) includes an inductance component, the current waveform has many ripples as shown in FIG. Here, I _m shown by the alternate long and short dash line is the average value of the current flowing through the load 6. In FIG. 5, the conduction ratio α = 50%, but if the output voltage E of the rectifier 4 is lowered and the conduction ratio α is increased by that amount, the average value I _{m of the} current supplied to the load 6 is the same value. This is convenient because the load on the chopper 5 can be reduced by the amount that the output voltage of the rectifier 4 is reduced.

[0005]

However, since there is a room for increasing the supply current, there is a limit to the decrease of the output voltage of the rectifier 4, and as described above, the direct current supplied from the chopper 5 to the load 6 is limited. Since the current contains a large amount of ripples, the ripples cause inconveniences such as noise generation and overheat generation. When the load 6 is a field winding, rectification failure occurs in the DC motor. There are also inconveniences. Therefore, in order to remove the ripple that causes such an inconvenience, although not shown in the figure, a large-capacity smoothing circuit is actually installed on the output side of the chopper 5, so that this DC power supply device has a large size.・ There is a disadvantage that it becomes expensive. There is also a method to increase the frequency of on / off operation in order to reduce the generated ripple, but for that purpose it is necessary to equip an oscillator corresponding to this operating frequency, and nevertheless the ripple reduction effect is large. There is no.

Therefore, an object of the present invention is to reduce the load on the chopper and reduce the ripple contained in the load current even when the rectifier output voltage is high.

[0007]

In order to achieve the above object, a direct current power supply device of the present invention includes a first transformer and a first rectifier which are connected to an alternating current power source and output a direct current of a desired voltage, and the alternating current. A second transformer and a second rectifier, which are connected to a power supply and output a direct current of a desired voltage, and a DC output side of the first rectifier and a DC output side of the second rectifier, which are connected in series to each other. A chopper for supplying a predetermined DC current to a load by chopping, and a DC output side of any one of the rectifiers and a diode connected in parallel to a series circuit of the chopper, or alternatively, the chopper. Is equipped with a control circuit that operates in synchronization with the frequency of the AC power supply.

[0008]

In the prior art, since all the DC voltage applied to the load was chopped by the chopper, a high voltage was applied to the chopper and the burden was heavy, and the generated ripple was large. Since there is a constant voltage part and a voltage part that is intermittent due to chopping, and both are superimposed and applied to the load, the value of the chopping voltage part is significantly lower than in the past. The load on the chopper is reduced and the ripple is reduced. Furthermore, the chopper control circuit is simplified by synchronizing the operation of the chopper with the AC power supply.

[0009]

1 is a circuit diagram showing a first embodiment of the present invention. As is apparent from FIG. 1, the present invention provides a first transformer 1
1 and the first rectifier 13 constitute a first DC power source, and a second DC power source
The transformer 12 and the second rectifier 14 constitute a second DC power supply, and the AC power supply 2 supplies AC power to the first DC power supply and the second DC power supply. The chopper 5 is connected in series to a circuit in which the DC output side of the first rectifier 13 and the DC output side of the second rectifier 14 are connected in series, and DC power is supplied to the load 6 via this chopper 5. A diode 15 is connected in parallel to the series circuit of the first rectifier 13 and the chopper 5. However, a smoothing circuit for removing a ripple included in the DC output of the first rectifier 13 and the second rectifier 14, a smoothing circuit for removing a ripple included in the DC output of the chopper 5, and a chopper. The illustration of the reactor and the freewheel diode accompanying 5 is omitted, and only the transistor as the semiconductor switch element is described as the chopper 5 in the case of the conventional example circuit already described in FIG. Is the same as.

Here, the output voltage of the first rectifier 13 is E ₁ ,
It is assumed that the output voltage of the second rectifier 14 is E ₂ and E ₁ = E ₂ . 2 is an operation waveform diagram showing the operation of the embodiment circuit shown in FIG. 1. FIG. 2 shows the waveform of the DC voltage applied to the load 6, and FIG. 2 shows the waveform of the DC current flowing through the load 6. Represents. As is apparent from the circuit of the first embodiment shown in FIG. 1, the output voltage E ₂ of the second rectifier 14 is applied to the load 6 as a constant voltage component by the action of the diode 15, and the output voltage of the first rectifier 13 is increased. The E ₁ is chopped by the chopper 5 and applied to the load 6. Therefore, a value obtained by superposing these two voltages is applied to the load 6 (see FIG. 2).

Although FIG. 5 shows the case where the input voltage of the chopper 5 is E and the conduction ratio α = 50%, the average voltage of the same value as this is obtained in the case of FIG. Then, if the flow rate α is also 50%, then E ₁ + E ₂
The value of will be 2/3 of E. Therefore, the value of E ₁ is E
1/3 of that. That is, the collector-emitter voltage of the transistor as the semiconductor switch element constituting the chopper 5 is 1/3 of that in the case of the conventional example circuit of FIG. 4, so the load on this transistor is greatly reduced. Will be. Further, the ripple of the DC current flowing through the load 6 becomes 1/3 of that of the conventional circuit (see FIG. 2), so that the smoothing circuit for removing this ripple can have a small capacity.

FIG. 3 is an operation waveform diagram showing the principle of the second embodiment of the present invention, which is applied to the circuit of the first embodiment shown in FIG. 1, and FIG. FIG. 3 shows the waveform of the triangular wave and the voltage command value for forming the operation pulse of the chopper 5, and FIG. 3 shows the operation pulse waveform of the chopper 5, respectively. In FIG. 3, a triangular wave for forming the operation pulse of the chopper 5 is generated in synchronization with the voltage waveform of the AC power supply 2. That is, since the triangular wave is generated each time the voltage waveform passes through the zero point, the operating frequency f of the chopper 5 is twice the power supply frequency (see FIG. 3). In this case, since the oscillator for generating the operating frequency f is unnecessary, the control circuit of the chopper 5 can be simplified. However, the second embodiment is more effective when used in combination with the first embodiment circuit described above. ..

[0013]

In the direct current power supply device in which the current supplied to the load after rectifying the alternating current is adjusted by using the chopper, two sets of direct current power supply devices are provided as in the present invention, and the respective direct current output sides are provided. The chopper and the chopper are connected in series to be connected to the load. A diode is connected in parallel to the series circuit of the DC output side of one DC power supply and the chopper. When the chopper is turned on and off with such a circuit configuration, the chopper can open and close a DC voltage that is significantly lower than before, so the load on the chopper can be greatly reduced and the DC current flowing to the load can be reduced. Since the ripple included in is also reduced, the smoothing circuit has a small capacity, and the device can be made small and inexpensive. Further, by performing the on / off operation of the chopper in synchronization with the AC power supply, an oscillator for determining the operating frequency is not required, and the effect that the chopper control circuit can be simplified can be obtained.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention.

2 is an operation waveform diagram showing the operation of the embodiment circuit shown in FIG.

FIG. 3 is an operation waveform diagram showing the principle of the second embodiment of the present invention.

FIG. 4 is a circuit diagram showing a conventional example of a DC power supply device that includes a chopper and controls a DC current supplied to a load.

5 is an operation waveform diagram showing the operation of the conventional circuit shown in FIG.

[Explanation of symbols]

 2 AC power supply 3 Transformer 4 Rectifier 5 Chopper 6 Load 11 1st transformer 12 2nd transformer 13 1st rectifier 14 2nd rectifier 15 Diode

Claims (2)

[Claims] 1. A first transformer and a first rectifier which are connected to an AC power source to output a DC of a desired voltage, and a second transformer and a second rectifier which are connected to this AC power source and output a DC of a desired voltage. And a chopper for connecting a direct current output side of the first rectifier and a direct current output side of the second rectifier in series with each other to supply a predetermined direct current to the load by chopping, A DC power supply device comprising a DC output side of a rectifier and a diode connected in parallel to a series circuit of the chopper. 2. A first transformer and a first rectifier that are connected to an AC power source to output a direct current of a desired voltage, and a second transformer and a second rectifier that are connected to this AC power source and output a direct current of a desired voltage. And a chopper for connecting a direct current output side of the first rectifier and a direct current output side of the second rectifier in series with each other to supply a predetermined direct current to the load by chopping, A DC power supply device comprising: a diode connected in parallel to a series circuit of a DC output side of the rectifier and the chopper; and a control circuit for operating the chopper in synchronization with the frequency of the AC power supply.