JP4547813B2 - DC-DC converter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a DC-DC converter that converts n (arbitrary integer) DC outputs from a DC power source through a transformer, and in particular, by a magnetic flux control of a saturable reactor against changes in input voltage and load. The present invention relates to a DC-DC converter capable of making an output voltage constant and having a function of changing an oscillation frequency in response to a change in input voltage.
[0002]
[Prior art]
FIG. 8 shows a conventional example of a multi-output power source.
As shown in the figure, the DC power source 1, the semiconductor switch element 21, the primary winding 31 of the transformer 3 and the semiconductor switch element 22 are connected in series, and the connection point between the semiconductor switch element 21 and the primary winding 31 of the transformer 3. The transformer reset diode 151 is connected between the connection point of the semiconductor switch element 22 and the DC power source 1, the connection point of the semiconductor switch element 22 and the primary winding 31 of the transformer 3, and the semiconductor switch element 21. And a connection point between the DC power source 1 and a transformer reset diode 152 are connected, and the oscillator 6 is connected to the gate terminals of the semiconductor switch elements 21 and 22, respectively.
[0003]
Also, transformer secondary windings 32a and 33a, saturable reactors 91a and 92a, diodes 101a, 101b, 102a and 102b, smoothing reactors 141 and 142, smoothing capacitors 81 and 82, and output voltage detection / regulation circuits 121 and 122 The output circuit composed of the magnetic flux control circuits 131 and 132 and the reset diodes 111a and 112a is provided according to the output number n (an arbitrary integer).
[0004]
FIG. 9 shows an example of the operation in FIG. Only the operation of the output circuit including the transformer secondary winding 32a will be described.
First, in the period {circle around (1)}, when the semiconductor switch elements 21 and 22 are turned on, a DC power supply voltage is applied to the transformer primary winding 31, and a voltage proportional to the DC power supply voltage is also applied to the transformer secondary winding 32a. Is done. At this time, since the saturable reactor 91a is in an unsaturated state and has a high inductance value, no current flows through the diode 101a.
In the period {circle around (2)}, when the saturable reactor 91a becomes saturated, a current flows through the diode 101a, stores energy in the smoothing reactor 141, and supplies power to the load.
[0005]
In the period {circle around (3)}, when the semiconductor switch elements 21 and 22 are turned off, a DC power supply voltage having a reverse polarity is applied to the transformer primary winding 31, and the transformer secondary winding 32a is also applied to that time. A voltage proportional to the reverse polarity DC power supply voltage is applied. At this time, due to the energy stored in the smoothing reactor 141, a current continues to flow through the smoothing reactor 141 via the diode 101b. The output voltage detection / adjustment circuit 121 and the magnetic flux control circuit 131 adjust the reset amount of the saturable reactor 91a so that the output voltage becomes constant.
By repeating such an operation, the DC power insulated from the DC power supply is supplied. The operation of the output circuit including the transformer secondary winding 33a is the same as described above.
[0006]
[Problems to be solved by the invention]
That is, in the conventional example shown in FIG. 8, the current change rate at the start of conduction of the diode is large, and it is difficult to improve the accuracy of output voltage control by the magnetic flux control circuit. Further, the magnetic flux density change ΔB of the transformer and the saturable reactor can be expressed by the following equation (1), and ΔB increases when the input voltage increases. For this reason, it is necessary to design a transformer and a saturable reactor under the condition where the input voltage is maximum, and there arises a problem that the transformer and the saturable reactor are increased in size.
ΔB = ET / (N · Ae) (1)
ET: product of voltage applied to winding and time N: number of turns of winding Ae: effective core area The object of the present invention is to control the output voltage without increasing the size of the transformer and the saturable reactor. It is to be able to increase the accuracy.
[0007]
[Means for Solving the Problems]
In order to solve such a problem, in the invention of claim 1, in an n (arbitrary integer) output DC-DC converter for converting from a DC power supply to another DC output via a transformer,
A first semiconductor switch element, a transformer primary winding, and a first capacitor are connected in series to the DC power source, and a parallel circuit of a second semiconductor switch element and a second capacitor is connected to the transformer primary winding. Connected in parallel between a line and the first capacitor, an oscillation circuit is connected to the gate terminals of the first and second semiconductor switch elements, respectively, a saturable reactor for the transformer secondary winding, A diode and a smoothing capacitor are connected in series, an output voltage detection / regulation circuit is connected to the DC output terminal, an output of the output voltage detection / regulation circuit is connected to the magnetic flux control circuit, and an output of the magnetic flux control circuit is connected to the saturable reactor. N output circuits are provided which are connected to a connection point with a diode through a reset diode.
An input voltage detection circuit is connected to a DC input terminal, and an oscillation frequency of the oscillation circuit is determined by an output from the input voltage detection circuit .
[0008]
According to the invention of claim 2, in a DC-DC converter of n (arbitrary integer) output for converting from a DC power source to another DC output via a transformer,
A first semiconductor switch element, a transformer primary winding, and a first capacitor are connected in series to the DC power source, and a parallel circuit of a second semiconductor switch element and a second capacitor is connected to the transformer primary winding. Connected in parallel between the line and the first capacitor, an oscillation circuit is connected to the gate terminals of the first and second semiconductor switch elements, respectively, and the first transformer secondary winding is One saturable reactor, a first diode and a first smoothing capacitor are connected in series, and a second saturable reactor, a second diode and a second smoothing capacitor are connected to the second transformer secondary winding. Are connected in series, the output voltage detection / regulation circuit is connected to the DC output terminal, the output of the output voltage detection / regulation circuit is connected to the magnetic flux control circuit, and the output of the magnetic flux control circuit is connected to the first saturable reactor and the first output. 1 Daio An output circuit is connected to the connection point between the second saturable reactor and the second diode via a first reset diode, and to the connection point between the second saturable reactor and the second diode via a second reset diode. Provide output,
An input voltage detection circuit is connected to a DC input terminal, and an oscillation frequency of the oscillation circuit is determined by an output from the input voltage detection circuit .
[0009]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a block diagram showing a first embodiment of the present invention.
As shown in the figure, a DC power source 1, a semiconductor switch element 21, a transformer primary winding 31, and a capacitor 4 are connected in series, and a parallel circuit of the semiconductor switch element 22 and the capacitor 5 is connected to the transformer primary winding 31. And the capacitor 4 are connected in parallel, the oscillation circuit 6 is connected to the gate terminals of the semiconductor switch elements 21 and 22, respectively, and the saturable reactor 91a and the diode 101a are connected to the secondary winding 32a of the transformer 3. And a smoothing capacitor 81 are connected in series, an output voltage detection / regulation circuit 121 is connected to the DC output terminal, an output of the output voltage detection / regulation circuit 121 is sent to the magnetic flux control circuit 131, and an output of the magnetic flux control circuit 131 is sent to the output An output circuit connected to a connection point between the saturable reactor 91a and the diode 101a via a reset diode 111a is provided for n outputs. 2 circuit component in FIG. 1) provided configured.
[0010]
FIG. 3 is a waveform diagram for explaining the operation in FIG.
In the period {circle around (1)}, the semiconductor switch element 21 is turned on and the semiconductor switch element 22 is turned off, whereby the voltage difference between the DC power supply voltage and the voltage of the capacitor 4 is applied to the transformer primary winding 31. A voltage proportional to the difference voltage is also applied to the secondary winding 32a. At this time, since the saturable reactor 91a is in an unsaturated state and has a high inductance value, no current flows through the diode 101a.
In the period {circle around (2)}, when the saturable reactor 91a becomes saturated, a current flows through the diode 101a. This current is determined by the resonance between the transformer leakage inductance and the capacitor 4 and rises gently in a sine wave shape to charge the smoothing capacitor 81 and supply power to the load.
[0011]
In period {circle around (3)}, the semiconductor switch element 21 is turned off and the semiconductor switch element 22 is turned on, whereby the voltage of the capacitor 4 is applied to the transformer primary winding 31, and the secondary winding 32 a of the transformer 3 is also applied. A voltage proportional to the voltage of the capacitor 4 is applied, but the diode 101a is turned off, and power is supplied from the smoothing capacitor 81 to the load. Further, the output voltage detection / adjustment circuit 121 and the magnetic flux control circuit 131 adjust the reset amount of the saturable reactor 91a so that the output voltage becomes constant. By repeating such an operation, the DC power insulated from the DC power supply is supplied. The operation of the output circuit including the transformer secondary winding 33a is the same as described above.
[0012]
In the circuit of FIG. 1, the current flowing through the diode 101a is determined by the resonance between the transformer leakage inductance and the capacitor 4, so that the current change rate is small. In this case, since the output constant voltage control by the magnetic flux control circuit can be controlled with respect to a gradual current change, the accuracy is improved.
FIG. 2 shows a modification of FIG.
This is characterized in that the positive terminal of the DC power source 1 is connected to the semiconductor switch element 22 and the negative terminal is connected to the semiconductor switch element 21, respectively. Omitted.
[0013]
FIG. 4 is a circuit diagram showing a second embodiment of the present invention.
As shown in the figure, a semiconductor switch element 21, a transformer primary winding 31 and a capacitor 4 are connected in series to the DC power source 1, and a parallel circuit of the semiconductor switch element 22 and the capacitor 5 is connected to the transformer primary winding 31. The oscillation circuit 6 is connected to the gate terminals of the semiconductor switch elements 21 and 22, respectively. The saturable reactor 91a, the diode 101a, and the smoothing capacitor 81 are connected to the transformer secondary winding 32a. A saturable reactor 91b, a diode 101b and a smoothing capacitor 81 are connected in series to the transformer secondary winding 32b, and an output voltage detection / regulation circuit 121 is connected to the DC output terminal of the transformer secondary winding 32b. The output of the adjustment circuit 121 is supplied to the magnetic flux control circuit 131, and the output of the magnetic flux control circuit 131 is connected to the saturable reactor 91a and the diode. The output circuit connected to the node between the node 101a via the first reset diode 111a and the node between the saturable reactor 91b and the diode 101b via the reset diode 111b is provided for n outputs (in FIG. 4). 2 circuits).
[0014]
The basic operation of this circuit is the same as that of FIG. 1, except that the saturable reactors 91b and 92b are in an unsaturated state during the period when the semiconductor switch element 21 is off and the semiconductor switch element 22 is on, the diodes 101b and 102b When the current does not flow and becomes saturated, power is supplied to the load from the transformer secondary windings 32b and 33b via the diodes 101b and 102b.
Also in this circuit, the current flowing through the diodes 101a, 101b, 102a, 102b is determined by the resonance between the transformer leakage inductance and the capacitor 4, so that the current change rate is small. In this case, since the output constant voltage control by the magnetic flux control circuit 131 can be controlled with respect to a gradual current change, the accuracy is improved.
[0015]
FIG. 5 shows a modification of FIG.
This is characterized in that the positive terminal of the DC power source 1 is connected to the semiconductor switch element 22 and the negative terminal is connected to the semiconductor switch element 21, respectively, and functionally the same as FIG.
[0016]
FIG. 6 is a circuit diagram showing a third embodiment of the present invention. The difference from FIG. 4 is that an input voltage detection circuit 7 is connected to the DC input terminal, and the oscillation frequency of the oscillation circuit 6 is changed based on the output from the input voltage detection circuit 7.
That is, the input voltage detection circuit 7 detects a DC input voltage and inputs the result to the oscillation circuit 6. Based on the output result from the input voltage detection circuit 7, the oscillation circuit 6 operates to lower the oscillation frequency when the DC input voltage is low and to increase the oscillation frequency when the DC input voltage is high.
[0017]
FIG. 7 shows an example of the oscillation frequency.
As shown in the figure, by changing the oscillation frequency according to the DC input voltage value, the numerator ET shown in the above equation (1) becomes substantially constant, and ΔB can be made substantially constant regardless of the input voltage. As a result, it is not necessary to design the transformer and the saturable reactor under the maximum input voltage condition, and the transformer and the saturable reactor are not increased in size.
[0018]
【The invention's effect】
According to the present invention, since the output constant voltage control by the magnetic flux control circuit can be controlled with respect to a gradual current change, the accuracy can be improved. Further, by changing the operating frequency with respect to the change in the input voltage, the change in the magnetic flux density of the transformer and the saturable reactor becomes substantially constant regardless of the input voltage, so that the transformer and the saturable reactor do not increase in size.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing a first embodiment of the present invention.
FIG. 2 is a configuration diagram showing a modification of FIG. 1;
FIG. 3 is a waveform diagram for explaining the operation of FIG. 1;
FIG. 4 is a block diagram showing a second embodiment of the present invention.
FIG. 5 is a configuration diagram showing a modification of FIG. 4;
FIG. 6 is a block diagram showing a third embodiment of the present invention.
7 is a characteristic diagram for explaining the operation of FIG. 6; FIG.
FIG. 8 is a circuit diagram showing a conventional example.
9 is an operation explanatory diagram of FIG. 8. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... DC power source, 21, 22 ... Semiconductor switch element, 3 ... Transformer, 31 ... Transformer primary winding, 32a, 32b, 33a, 33b ... Transformer secondary winding, 4, 5 ... Capacitor, 6 ... Oscillation Circuit, 7 ... Input voltage detection circuit, 81, 82 ... Smoothing capacitor, 91a, 91b, 92a, 92b ... Saturable reactor, 101a, 101b, 102a, 102b ... Diode, 111a, 111b, 112a, 112b ... Reset diode, 121, 122 ... output voltage detection and adjustment circuit, 131, 132 ... magnetic flux control circuit, 141, 142 ... smoothing reactor, 151, 152 ... transformer reset diode.

Claims (2)

In an n (arbitrary integer) output DC-DC converter that converts from a DC power source to another DC output via a transformer,
A first semiconductor switch element, a transformer primary winding, and a first capacitor are connected in series to the DC power source, and a parallel circuit of a second semiconductor switch element and a second capacitor is connected to the transformer primary winding. Connected in parallel between a line and the first capacitor, an oscillation circuit is connected to the gate terminals of the first and second semiconductor switch elements, respectively, a saturable reactor for the transformer secondary winding, A diode and a smoothing capacitor are connected in series, an output voltage detection / regulation circuit is connected to the DC output terminal, an output of the output voltage detection / regulation circuit is connected to the magnetic flux control circuit, and an output of the magnetic flux control circuit is connected to the saturable reactor. N output circuits are provided which are connected to a connection point with a diode through a reset diode.
A DC- DC converter characterized in that an input voltage detection circuit is connected to a DC input terminal, and an oscillation frequency of the oscillation circuit is determined by an output from the input voltage detection circuit . In an n (arbitrary integer) output DC-DC converter that converts from a DC power source to another DC output via a transformer,
A first semiconductor switch element, a transformer primary winding, and a first capacitor are connected in series to the DC power source, and a parallel circuit of a second semiconductor switch element and a second capacitor is connected to the transformer primary winding. Connected in parallel between the line and the first capacitor, an oscillation circuit is connected to the gate terminals of the first and second semiconductor switch elements, respectively, and the first transformer secondary winding is One saturable reactor, a first diode and a first smoothing capacitor are connected in series, and a second saturable reactor, a second diode and a second smoothing capacitor are connected to the second transformer secondary winding. Are connected in series, the output voltage detection / regulation circuit is connected to the DC output terminal, the output of the output voltage detection / regulation circuit is connected to the magnetic flux control circuit, and the output of the magnetic flux control circuit is connected to the first saturable reactor and the first output. 1 Daio An output circuit is connected to the connection point between the second saturable reactor and the second diode via a first reset diode, and to the connection point between the second saturable reactor and the second diode via a second reset diode. Provide output,
A DC- DC converter characterized in that an input voltage detection circuit is connected to a DC input terminal, and an oscillation frequency of the oscillation circuit is determined by an output from the input voltage detection circuit .

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