JPS6110965A - Multioutput converter - Google Patents

Abstract

PURPOSE:To accurately produce an output and to perform a small size, high efficiency and low cost by connecting a magnetic amplifier and a filter circuit with the output side. CONSTITUTION:A magnetic amplifier 12 and a filter circuit 13 are connected through a rectifier 3 with the side of an output B. On end of a load winding of the amplifier 12 is connected with a transformer 2, the other end is connected with the rectifier 3 to flow a load current to a load winding, a constant DC current is flowed to a control winding to form the DC output B obtained through the filter circuit 13 constantly.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to DC-DCs used in telephone offices, etc.
This invention relates to a multi-output converter as a DC converter.

In other words, the main power source at telephone offices and the like is 48V DC, but after converting this DC to AC using DC/AC conversion means consisting of switching transistors, etc.
A multi-output converter further rectifies and smooths and supplies it to various types of loads, and the present invention is directed to such a multi-output converter, particularly a multi-output converter that obtains independent constant DC voltage output and independent constant current output. It is about improvement.

[Conventional technology]

FIG. 4 is a block diagram showing a conventional example of a fourth multi-output converter. Although we say multiple outputs, we will explain the case of two outputs (constant voltage output for human output, constant current output for B output) as an example below, but the circumstances to be explained are the same even if there are three or more outputs. be.

In the figure, 1 is a DC-AC conversion circuit (switching circuit), 2 is a transformer with multiple secondary windings, 3 is a rectifier circuit, 4 is a smoothing circuit, 5 is an output voltage detection circuit, and 6 is a switching circuit. A and B are output terminals of the circuit that controls the pulse width of the ON/OFF driving pulses of the switching elements constituting the circuit.

In the multi-output converter configured in this way, the output voltage detected by the side forming the feedback loop, that is, the detection circuit 5, is used to control the switching elements constituting the conversion circuit 1 via the pulse width control circuit 6. The output (human output) on the side that controls the pulse width of the on/off drive pulse is stabilized with high precision, but the other output (B output) is connected to the input/output side, for example. When a change in the load occurs and the pulse width of the on/off drive pulse in the conversion circuit 1 is controlled, the average value of the voltage applied to the primary winding of the transformer 2 changes, and the amount of the change is Since the output current fluctuates as it is, a highly accurate current output cannot be obtained on the B output side.

Furthermore, in order to eliminate such drawbacks, it has been conventional to adopt circuit configurations as shown in FIGS. 5 and 6, respectively. In these figures, parts that are common to those in FIG. 4 are given the same reference numerals, and this point is also the same in each of the following figures.

Now, in FIG. 5, 7 is a series dropper circuit, 8 is a series dropper control circuit, and 9 is a current detection circuit.

In FIG. 6, 9 is a current detection circuit, 10 is a switching circuit, and 11 is a control circuit for the switching circuit 10.

Each of the configurations shown in FIGS. 5 and 6 has a means for controlling the B output to a constant value on the secondary side of the transformer 2, so that high accuracy can be obtained for both the A and B outputs. Fifth
In the circuit configuration shown in the figure, high efficiency cannot be achieved due to the large loss of the series dropper circuit 7, and in the circuit configuration shown in FIG. 6, the switching circuit 10 and control circuit 11 become complicated, and the number of smoothing circuits 4 increases However, the disadvantage is that it is not possible to obtain a compact, highly efficient, and low-cost multi-output converter.

[Problem that the invention seeks to solve]

The problem to be solved by the present invention is to improve the precision of each output in a multi-output converter, as well as to reduce the size, increase efficiency, and reduce cost.
The point is to try to achieve this.

Therefore, an object of the present invention is to provide a multi-output converter in which not only each of the multi-outputs has high precision, but also a small size, high efficiency, and low cost. be.

[Means and operations for solving the problems] FIG. 7 is a block diagram showing the operating principle of the present invention. The circuit configuration shown in this figure differs from the conventional circuit shown in FIG. 4 in that the magnetic amplifier 12 and filter circuits 13t-e are connected on the B output side as shown.

As is well known, a magnetic amplifier consists of a saturable reactor, which is formed by providing a control winding and a load winding (also referred to as an AC winding) to a sharp square magnetic core having saturation characteristics. When DC current is passed through the control winding, the load winding current connected to the AC power source changes.

When a magnetic amplifier is used in this way, the current flowing through the load winding can be controlled to a constant level by the direct current flowing through the control winding by utilizing the nonlinearity of the magnetic material. Therefore, in the circuit shown in FIG. One end of a load winding (not shown) is connected to the transformer 2 and the other end to the rectifier circuit 3, and a load current is passed through the load winding, and a constant DC current is caused to flow through a control winding (not shown). In this way, the DC B output obtained through the filter 13 is made to be a constant current.

FIG. 8 is a block diagram illustrating the operating principle of a further developed form of the present invention. The circuit configuration shown in this figure differs from that shown in FIG. 7 in that a current detection circuit 9 and a magnetic amplifier control circuit 14 are added as shown.

In other words, the output current of the B output is detected by the detection circuit 9,
By feeding back the detection results to the control winding of the magnetic amplifier 12 via the control circuit 14, higher accuracy and a wider stabilization range of the B output current are ensured.

In each of the circuits shown in FIGS. 7 and 8, the transformer 2 can be omitted if insulation is not required between the input and output. In addition, if insulation is not required between the A and B outputs, the rectifier circuit 3 and magnetic amplifier 120 on the human output side
The input (the input flowing to the load winding) can be taken out from the same output winding of the transformer 2. Furthermore, isolation from other B outputs can also be obtained by inserting a transformer between the magnetic amplifier 12 and the rectifier circuit 3 on the B output side.In this way, insulation between input and output and from other outputs can be achieved. It goes without saying that the present invention can also be applied to unnecessary circuit configurations.

〔Example〕

The present invention will now be described in detail with reference to the drawings.

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

In the same figure, 15 is a DC power supply, 16 is a transformer, and 17
．． 18 are respectively switching transistors, 19.2
0 is a feedback diode, and 21 is 1 of the transformer 16.
The next windings L22 and 23 are the secondary windings of the transformer 16, respectively.
24.25 are rectifier diodes, 26 are chokes, 27 are capacitors, and 28.29 are voltage detection.
Resistor, 30 is an error amplifier, 31 is a pulse width control circuit, 3
2 to 35 are rectifier diodes, 36 is a capacitor, 37 is a saturable reactor that constitutes a magnetic amplifier, 37
A is a load winding of the reactor, 37b is a control winding, 38 is a restraining choke, and 39 is a control DC current source. Note that the turn ratio between the load winding 37a and the control winding 37b is 1:nn.

Next, circuit operation will be explained.

By alternately driving the switching transistors 17 and 18 on and off using the output signal of the pulse width control circuit 31, the DC power supply 15 is converted into a square wave AC voltage, and then a predetermined square wave voltage is generated via the transformer 16. can get. The square wave voltage from the A output side secondary winding 22 of the transformer 16 is rectified by rectifier diodes 24 and 25,
It is smoothed by a choke 26 and a capacitor 27, and becomes a constant DC voltage m force as a human output.

On the other hand, the square wave voltage from the secondary winding 23 on the B output side is converted into a constant current by flowing through the load winding 37a of the saturable reactor 37, and a constant DC current is obtained at the B output.

In the circuit configured in this manner, even if the voltage of the DC power supply 15 or the load (not shown) connected to the human output fluctuates, the fluctuation is detected by the voltage detection resistors 18, 19 . [Since the driving pulse width of the switching transistors 17 and 18 is changed via the difference amplifier 30 and the pulse width control circuit 31, the output voltage on the input/output side is stabilized and does not fluctuate. On the other hand, the output current IB on the B output side is the control DC constant current source 3
9 to the control winding 37b, which is a stable DC constant current determined by the current ISB flowing from the control winding 37b to the control winding 37b.

Therefore, even if the unillustrated load connected to the B output fluctuates,
The output current of the B output does not change, and its influence does not appear on the input/output side. Further, even if an excessive fluctuation occurs such as shorting or opening of the B output, the effect will not appear on the input/output side. Moreover, the saturable reactor 37 can be used without applying feedback to the control DC current source 39 from the output side.
Since a stable constant current can be obtained, the circuit can be simplified and a low-cost, highly efficient power supply can be achieved.

Figure 2 is a graph showing the output current and voltage characteristics of the B output side when the pulse width of the on/off drive pulse input to the switching transistors 17 and 18 changes as the human output fluctuates in Figure 1. Indicated by

Pulse width of on/off drive pulse is 20μs to 14μs
It can be seen that good constant current characteristics can be obtained in the S region even when the current is changed. Therefore, if a power supply circuit is designed to operate in the S region, a stable constant current output can be obtained at the B output even if the on/off drive pulse width of the switching transistor changes to stabilize the output. become.

Note that the graph in FIG. 6 shows the operating frequency of the switching transistor at 20 KHz (period: 50 μs).

Therefore, this is a graph obtained when the maximum drive pulse width was 25 μs.

FIG. 3 is a circuit diagram showing another embodiment of the present invention. The embodiment shown in the figure is the actual flow side corresponding to FIG.

In this embodiment, the output current on the B output side is detected by the output current detection circuit 4.
This is an embodiment in which negative feedback is applied to the control DC current source 39 via the error amplifier 41 to widen the stabilization region of the B output. There is no need to further explain this embodiment.

The above explanation is for a two-output, multi-output constant current converter that uses transistors as switching elements, but it can also be applied to converters with three or more outputs, even when other switching elements are used. However, similar effects can be obtained by implementing the present invention.

In addition, we have explained square wave AC sources that have a push-pull configuration, but in addition to half bridges and full bridges, there are also parallel connections of switching elements, parallel connections of the primary windings of transformers, series connections of the secondary windings, etc. It goes without saying that the present invention can also be applied to devices having a circuit configuration for increasing the output capacitance of the device.

Further, in the above description, a load having a rectifier circuit is assumed as the load, but the same effect can be obtained even if the load is a general load such as a heater lamp. Further B
Similar effects can be obtained by implementing the present invention even when the output rectifying circuit, smoothing circuit, and load are located far away.

〔Effect of the invention〕

As explained above, according to the present invention, each output of a multi-output converter can be easily stabilized with high precision with a simple circuit configuration, and severe load fluctuations such as short-circuiting and opening of constant current output can be prevented. Even if it occurs, it does not affect the constant voltage output, so it has the advantage of providing a high-quality power source. Further, since the multi-output converter according to the present invention has a simple circuit configuration, it has the advantage of being able to be made smaller, more efficient, and less expensive.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing one embodiment of the present invention, and Fig. 2 is a circuit diagram showing an embodiment of the present invention.
Graph showing the voltage-current characteristics on the B output side in the figure, 3rd
The figure is a circuit diagram showing another embodiment of the present invention, FIG. 4 is a block diagram showing a conventional example of a multi-output converter, FIG. 5 is a block diagram showing another conventional example, and FIG. FIG. 7 is a block diagram showing the operating principle of the present invention, and FIG. 8 is a block diagram showing the operating principle of the present invention in a further developed form. Description of symbols 1...DC/AC conversion circuit, 2...Transformer, 3...Rectifier circuit, 4...Smoothing circuit, Death... Voltage detection circuit, 6...Pulse width control circuit, 7...Series dropper circuit,
8...Series four-flange control circuit, 9...
... Current detection circuit, 10 ... Song switching circuit, 11
...Switching circuit control circuit, 12...
... Magnetic amplifier, 13 ... Filter circuit, 14
......Control circuit for magnetic amplifier, 15...
DC power supply, 16...Transformer, 17, 18...
...Switching transistor, 19.20・Song・
Feedback diode, 21... Primary winding L of transformer
22, 23... Secondary winding of transformer, 24, 2
Rectifier diode, 26...Choke, 2
7... Capacitor, 28.29... Voltage detection resistor, 3o... Error amplifier, 31...
...Pulse width control circuit, 32-35... Rectifier diode, 36... Capacitor, 37...
...Saturable reactor, 37a...Load winding, 37b...Control winding, 38...Choke for restraint, 39...For control DC current source, 4
0... Output current detection circuit, 41... Error amplifier representative Patent attorney Akio Namiki Patent attorney Kiyoshi Matsuzaki Figure 1 Figure 3 Figure 4

Claims (1)

[Claims] 1) A DC/AC converter that converts DC to AC and outputs the same, and at least two output circuits, a first and a second output circuit, that rectify and smooth the AC voltage obtained by the means and generate a DC output. , means for negative feedback of the output signal obtained from the first output circuit to the DC/AC conversion means to make the output from the first output circuit a constant voltage; A multi-output converter comprising: a magnetic amplifier connected to a second output circuit and serving to make the output constant current.