JPH072011B2 - Multi-stage connection DC / DC converter device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a multi-stage connection DC capable of obtaining a constant voltage DC that is insulated from a DC power supply with large voltage fluctuations.
/ DC converter device.

[Conventional technology]

If the DC power supply voltage is higher than the rated voltage of the semiconductor switch element used in the switching circuit, DC / D
Use multiple C converters connected in multiple stages.

FIG. 2 is a main circuit connection diagram showing a conventional example of a multistage DC / DC converter device. This Fig. 2 shows a two-stage series-connected DC
In the example of the / DC converter device, reference numeral 11 is a DC / AC conversion switching circuit, and diodes are respectively connected in antiparallel to the gate turn-off thyristors 11A and 11B as semiconductor switching elements, and these are connected to a capacitor. It constitutes a phase bridge circuit. Reference numeral 12 is an insulation transformer, which transforms and insulates the output AC voltage of the switching circuit 11 and supplies the AC voltage to the rectifier circuit 13 at the next stage. The rectifier circuit 13 is composed of a diode full-wave rectifier bridge and outputs a DC voltage E ₃ . The combination of the switching circuit 11, the insulating transformer 12, and the rectifying circuit 13 constitutes a unit circuit of the DC / DC converter, and similarly, the switching circuit 21, the insulating transformer 22, and the rectifying circuit 23 corresponding to the respective circuits are formed. The combination with and also constitutes the unit circuit of the DC / DC converter.

In these two sets of DC / DC converters, the switching circuits 11 and 21 on the input side are connected in series to input the DC voltage from the DC power supply 2, and the rectifying circuit 13 on the output side and
23 is also connected in series, and the output voltage E ₃ of the rectifier circuit 13 and the rectifier circuit
The smoothing circuit composed of the smoothing reactor 3 and the smoothing capacitor 4 absorbs and removes the ripple component contained in the combined voltage E ₅ of the output voltage E _{4 of} 23, and smooths the DC output voltage.
E ₀ is supplied to the load 5. Reference numeral 9 is a dummy resistor, the role of which will be described later.

In multistage connection DC / DC converter apparatus shown in FIG. 2, but to synchronize to on-off operation of the respective switching circuits 11 and 21 are usually, in this case, the synthesis DC voltage of the output side E ₅ Since a large amount of ripples is contained in the device, a large capacity is required for the smoothing reactor 3 and the smoothing capacitor 4 in order to obtain a smooth direct current, and the device is large and expensive. There is an inconvenience.

Therefore, the switching content of the combined DC output voltage E ₅ is reduced by switching both switching circuits 11 and 21 not at the same time but with an appropriate phase difference.
Therefore, a control method for reducing the capacity of the smoothing circuit is described in "Japanese Patent Application No.
62-272556 ”.

FIG. 3 is a control block diagram proposed in Japanese Patent Application No. 62-272556 for controlling the multi-stage connection DC / DC converter device shown in FIG. 2, which includes an oscillator 31, a voltage regulator 32, and a voltage setter. 33, phase shifters 34 and 35, pulse distribution circuits 36 and 37, and gate drive circuits 38, 39, 40, 41.

Although detailed description of the operation of the control block diagram shown in FIG. 3 is omitted, in short, the gate turn-off thyristors 11A, 21A, 11B and 21B shown in FIG. It is operated with a phase difference equivalent to / 4 cycle.

[Problems to be solved by the invention]

The multi-stage connection DC / DC converter device composed of the main circuit shown in FIG. 2 is controlled by the control device shown in FIG. 3, but the switching circuits 11 and 21 are used for the voltage fluctuation of the DC power supply 2. Gate turn-off thyristor 11
The output DC voltage is maintained at a predetermined value by changing the conduction rate α of A, 11B, 21A, 21B. Further, the conductivity rate α is changed depending on the magnitude of the electric power to the load 5.

FIG. 4 is a time chart showing the voltage waveform when the conductivity α is larger than 0.5. FIG. 4 (a) shows the waveform of the output voltage E ₃ of one rectifying circuit 13, (B) shows the waveform of the output voltage E ₄ of the other rectifier circuit 23 as shown in FIG.
Shows the waveform of the combined output voltage E ₅ of both. Here, E in the figure is the voltage of the DC power supply 2, N is the turn ratio of the insulation transformers 12 and 22, and E ₀ is the DC output voltage smoothed by the smoothing circuit.

FIG. 4 shows the case where the conductivity α is larger than 0.5, that is, the voltage E of the DC power supply 2 is low, or the capacity of the load 5 is large, and the voltage E of the DC power supply 2 is high.
Alternatively, when the capacity of the load 5 is small, this conductivity α
May be less than 0.5.

Fig. 5 is a time chart showing the voltage waveform when the conductivity α is smaller than 0.5. Fig. 5 (a) shows the output voltage E ₃ of the rectifier circuit 13, and Fig. 5 (b) shows the rectification. The output voltage E ₄ of the circuit 23 and FIG. 5C show the waveforms of the combined output voltage E ₅ , respectively. As is apparent from FIG. 5, when the conductivity α becomes smaller than 0.5, The ripple content rate of the combined output voltage E ₅ becomes large.

By the way, the gate turn-off thyristor and other semiconductor switching devices have a minimum on-time, and therefore the conductivity α cannot be made smaller than a certain degree. Therefore, when the load 5 is unloaded, even if the conductivity α is reduced to the minimum value, the smoothing capacitor 4 is peak-charged to a peak value of N · E / 2 as shown in FIG. become.

FIG. 6 is a time chart showing the voltage waveform in the case of no load. FIG. 6 (a) shows the output voltage of the rectifier circuit 13.
E ₃ and FIG. 6 (b) show the waveforms of the output voltage E ₄ of the rectifier circuit 23, and FIG. 6 (c) show the combined output voltage E ₅ , respectively.

When the load 5 is unloaded, the peak-charged voltage of the smoothing capacitor 4, that is, the value N · E / 2 of the combined output voltage E ₅ is directly applied to the load 5, and this is no load. N · E / 2 is continuously applied as it is. That is, the voltage cannot be controlled.

Therefore, in order to prevent the peak charge value from being continuously output, the dummy resistor 9 is used in the conventional circuit shown in FIG.
However, since the dummy resistor 9 consumes useless electric power, there are disadvantages such as heat generation and a reduction in the efficiency of the device, and there is a disadvantage that energy consumption is reversed.

Therefore, an object of the present invention is to enable the output voltage of the multi-stage DC / DC converter device to be controlled to a desired value regardless of the presence / absence of a load when the multi-stage DC / DC converter device is used.

[Means for solving problems]

In order to achieve the above object, the multi-stage connection DC / DC of the present invention
The converter device includes a switching circuit that converts input direct current into alternating current, and an insulating transformer that insulates the alternating current.
Prepare a plurality of sets of DC / DC converters composed of this rectifier circuit that converts the secondary side AC to DC, and connect these switching circuits in series to the DC power source to connect each switching circuit. Multi-stage connection DC / DC converter device having a configuration in which switching operations are performed with an appropriate phase difference between each other, the rectifier circuits are connected in series, and the DC output from these rectifier circuits is smoothed and taken out by a smoothing circuit including a capacitor. In the above, the number of the DC / DC converters used is a value greater than the ratio of the maximum output voltage and the minimum output voltage of the DC power supply, and the turns ratio of each insulation transformer is output via the smoothing circuit. The selected DC voltage should be smaller than the value obtained by dividing the DC voltage by the maximum output voltage of the DC power supply and the number of used DC / DC converters.

[Action]

This invention selects the number of multi-stage series connection of DC / DC converters larger than the voltage ratio when the DC power supply outputs the maximum voltage and when it outputs the minimum voltage, and when the power supply voltage is the maximum when the load is applied. However, by selecting the turns ratio N of the insulation transformer so that the conductivity α becomes larger than 0.5, when the value of the conductivity α is smaller than 0.5, the peak value of the combined output voltage is set to the multistage. Since it is lower than the rated output voltage value of the connected DC / DC converter, the output voltage can be controlled to a desired value even when there is no load.

〔Example〕

 FIG. 1 is a main circuit connection diagram showing an embodiment of the present invention.

In FIG. 1, the switching circuit 11 and the isolation transformer
One of the DC / DC converter is formed by 12 and the rectifying circuit 13, and the other DC / DC converter is formed by the switching circuit 21, the insulating transformer 22, and the rectifying circuit 23. And 21 connected in series to the DC power supply 2, and the rectifier circuits 13 and 23
And are connected in series, and smoothing reactor 3 and smoothing capacitor 4
Since a direct current of a predetermined voltage is supplied to the load 5 via the smoothing circuit consisting of, the same as in the case of the conventional circuit described above in FIG.

The number M of switching circuits in series is equal to the number of gate turn-off thyristors 11A, 11B, 21 that constitute this switching circuit.
It is usually determined by the balance between the rated voltage of A and 21B and the output voltage E of the DC power supply 2, but in the present invention, when the output voltage fluctuation of the DC power supply 2 is large, the maximum output The number of series M is determined with respect to the voltage ratio between the voltage E _max and the minimum output voltage E _min .

That is, each of the DC / DC converters with the number of series M is 2π /
Assuming that the operation is performed with a phase difference of M, the peak value E _p of the combined output voltage E ₅ after rectification is when the conduction rate α ≦ 1 / M, The output voltage E _{0 under} load is When E = E _max , the no-load output voltage is equal to E _p . To make this smaller than the predetermined DC output voltage E ₀ , When E = E _min , if the conductivity rate under load is α = 1, then from equation (2), E ₀ = E _min · N (4) From equations (3) and (4) above, M shown in the equation (5) is an integer, and this integer M is the number of series. However, from the relationship between the rated voltage of the semiconductor element and the DC power supply voltage, it is not prohibited to make the number of series larger than the value M obtained by the equation (5).

From the above formula (3), the winding ratio N of the insulation transformer is Becomes

In the above formula (3), the DC power source 2 outputs the maximum output voltage E _max.
At the time of, it means that the output voltage of each DC / DC converter becomes the value shown on the left side. That is, in the embodiment of FIG. 1, since M = 2, Therefore, the peak value E _p of the combined output voltage E ₅ is
If it is less than 0.5, it will be lower than the rated output voltage. Therefore, even if the smoothing capacitor 4 is peak-charged with no load, this peak charge value does not exceed the rated output voltage. Therefore, even when there is no load, the output can be obtained by changing the conductivity α near 0.5. The voltage value can be maintained at the desired value.

〔The invention's effect〕

According to the present invention, a plurality of sets of DC / DC converters each composed of a switching circuit, an insulation transformer and a rectifier circuit are connected in multiple stages, and the number of the multiple stages connected is the maximum value of the voltage fluctuation of the DC power supply. And the minimum value, and the winding ratio of the insulation transformer divides the DC voltage output through the smoothing circuit by the maximum output voltage of the DC power supply. The peak charge value of the smoothing capacitor can be made lower than the rated output voltage even when there is no load by selecting it so that it is smaller than the value obtained by multiplying the number of series. Even if there is, and even if the load changes, the DC output voltage can be arbitrarily controlled, so that the dummy resistor can be omitted, wasteful consumption of energy can be suppressed, and the efficiency of the device can be improved.

[Brief description of drawings]

FIG. 1 is a main circuit connection diagram showing an embodiment of the present invention,
FIG. 2 is a main circuit connection diagram showing a conventional example of a multi-stage connection DC / DC converter device, and FIG. 3 is a multi-stage connection DC / DC shown in FIG.
Control block diagram for controlling converter device, fourth
The figure shows the time chart showing the voltage waveform when the conductivity α is larger than 0.5. Fig. 5 shows the time waveform showing the voltage waveform when the conductivity α is smaller than 0.5. Fig. 6 shows no load. 6 is a time chart showing a voltage waveform in the case of. 2 ... DC power supply, 3 ... Smoothing reactor, 4 ... Smoothing capacitor, 5 ... Load, 9 ... Dummy resistor, 11, 21 ...
Switching circuit, 11A, 11B, 21A, 21B …… Gate turn-off thyristor, 12,22 …… Insulation transformer, 13,23 …… Rectifier circuit, 31 …… Oscillator, 32 …… Voltage regulator, 33 …… Voltage setting , 34, 35 ...... Phase shifter, 36, 37 ...... Pulse distributor, 38, 3
9,40,41 …… Gate drive circuit.

Claims (1)

[Claims] 1. A DC / DC circuit comprising a switching circuit for converting input DC into AC, an insulating transformer for insulating this AC, and a rectifying circuit for converting secondary side AC of this insulating transformer into DC. Prepare a plurality of sets of DC converters, connect these switching circuits in series and connect them to a DC power supply to cause each switching circuit to perform switching operation with an appropriate phase difference, and connect each of the rectifier circuits in series. In a multi-stage connection DC / DC converter device configured to extract the DC output from a rectifier circuit by smoothing it with a smoothing circuit including a capacitor, the number M of DC / DC converters used and the number of turns N of each insulation transformer. And However, E _{max is} the maximum output voltage of the DC power supply E _{min is} the minimum output voltage of the DC power supply E _{0 is} the DC output voltage of the smoothing circuit.
Converter device.