JPH0222630B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a constant voltage power supply device that uses a series resonant DC-DC converter and can obtain a stabilized DC voltage at an output terminal.

Conventional configurations and their problems Conventional switching regulators generally use the PWM method, which stabilizes the DC voltage at the output terminal of a constant voltage power supply by controlling the on/off operation ratio of the switching element. It is. However, the disadvantage of the above method is that there is a period in which both current and voltage change sharply when the switching element is turned on and off, resulting in large switching loss and large unnecessary radiation noise. Therefore, if you consider the above switching regulator as a power source for a sounder,
Since it requires noise countermeasures such as inserting a filter in the input/output section to greatly attenuate unnecessary radiation noise and providing a completely hermetically sealed shield, there are problems such as increased costs and decreased reliability.

As a means to solve the above drawbacks, a series resonant DC-DC converter using a series resonant circuit composed of a capacitor and a coil has been proposed.
In this series resonant type DC-DC converter, the current waveform when the switching element is conductive is sinusoidal due to the series resonant circuit, and the current and voltage intersect at approximately zero when the switching element is turned on and off. Therefore, switching loss and unnecessary radiation noise are significantly reduced. However, in the series resonant DC-DC converter, it is difficult to perform control to stabilize the DC voltage at the output terminal of the constant voltage power supply device without impairing the above-mentioned characteristics in response to input/output fluctuations.

Based on the above points, the circuit configuration and operation of a conventionally used series resonant DC-DC converter will be explained.

FIG. 1 is a basic circuit configuration diagram of a conventional series resonant DC-DC converter, and FIGS. 2a, b, and c are its operating waveform diagrams. In FIG. 1, switching elements 3 and 4 (for example, transistors, MOSFETs,
thyristors, etc.) are connected in series, and the primary winding 5a of the conversion transformer 5 and the capacitor 7 are connected in series between the midpoints of the input DC power supplies 1 and 2 and the switching elements 3 and 4. In addition, 2 of the conversion transformer 5
A rectifier circuit 8 and a smoothing capacitor 9 are connected to the next winding 5b.
is connected, and a load 10 is connected to its output terminals a and b. Here, the effective leakage inductance of the conversion transformer 5 and the capacitor 7 constitute a series resonant circuit. Let i be the resonant current flowing through this series resonant circuit, and let V _C be the charging voltage indicating the amount of energy stored in the capacitor 7.

Figure 2 a, b, and c show the on/off states of switching elements 3 and 4, the resonance current i, and the charging voltage V _C
The operating waveform diagram is shown. In FIG. 2, the switching element 3 is turned on at time _t1 , and a sinusoidal resonant current i determined by the effective leakage inductance and the capacitance of the capacitor 7 flows between time _t1 and time _t2 . During the above period, the charging voltage of the capacitor 7 changes from the initial charging voltage -V _c1 to the resonance current i
Therefore, it becomes V _c1 .

Next, at time _t2 , switching element 3 is turned off. During time t ₂ ≦ t ≦ t ₃ , both switching elements 3 and 4 are in the off period, so the resonant current i becomes zero, and the charging voltage V _c1 of the capacitor 7 also remains at V _c1 since there is no discharge path. It will be done. In this state, when the switching element 4 is turned on at time _t3 , the operation waveform is reversed in polarity from the operation waveform between time _t1 and time _t3 . In addition, the resonant current i is transmitted to the secondary side via the conversion transformer 5, and rectified and
After smoothing, load 1 is used as the DC voltage of output terminals a and b.
0.

The above is the circuit configuration and operation of a conventional series resonant DC-DC converter. Above series resonant DC
- As means for controlling the DC converter and stabilizing the DC voltage at the output terminal, there is a control method that changes the capacitance value of the capacitor 7, and a control method that changes the period during which both the switching elements 3 and 4 are in the OFF state, that is, a switching method. Two methods have been proposed to control the frequency. However, in either case, the amount of energy stored in the capacitor 7 changes only slightly. This means that the amount of energy transferred throughout the system changes only slightly, so the amount of energy transferred to the output does not change either. Therefore, with the two control methods described above, it is difficult to control the DC voltage values of the output terminals a and b to be stabilized.

Purpose of the Invention The purpose of the present invention is to stabilize the DC voltage at the output terminal over a wide range of input/output fluctuations without impairing the characteristics of the series resonant DC-DC converter, which has extremely low switching loss and unnecessary radiation. The purpose of this invention is to provide a constant voltage power supply device.

Configuration of the Invention In order to achieve the above object, the present invention provides for first and second input DC power supplies connected in series.
1st and 2nd connected in series for on/off operation
Switching means that conduct in only one direction are connected in parallel, and an inductor and an energy storage means are provided between a midpoint between the first and second DC power sources and a midpoint between the first and second switching means. and a smoothing circuit is connected to the output terminal of the energy storage means to obtain a DC voltage at the output terminal of the smoothing circuit, and the energy storage means includes a capacitor and a smoothing circuit. It consists of a control transformer in which a first winding is connected to both ends of a capacitor, the first winding of the control transformer is connected to the input terminal of the energy storage means, and the second winding of the control transformer is connected to the input terminal of the energy storage means. first control means respectively connected to the output terminals of the storage means and further controlling the inductance of the first winding of the control transformer as a function of the DC voltage at the output terminal of the smoothing circuit; and the output of the smoothing circuit. and second control means for controlling the switching frequencies of the first and second switching means as a function of the DC voltage at the terminal.

Furthermore, the present invention connects in series an inductor, an inductor, and an energy storage means to an input DC power source, and connects a smoothing circuit to an output terminal of the energy storage means. to obtain a DC voltage at the output terminal of the smoothing circuit, and the energy storage means is connected to a capacitor and a first voltage source across the capacitor.
The first winding of the control transformer is connected to the input terminal of the energy storage means, and the second winding of the control transformer is connected to the output terminal of the energy storage means. first control means connected to each other and further controlling the inductance of the first winding of the control transformer as a function of the DC voltage at the output terminal of the smoothing circuit; and second control means for controlling switching frequencies of the first and second switching means.

With the above configuration, the constant voltage power supply device of the present invention can stabilize the current and voltage at the output terminal against wide range input/output fluctuations.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below based on the drawings. First, the operation of the present invention will be described based on the basic circuit configuration diagram of the present invention.

A block diagram of one basic circuit configuration of the present invention is shown in FIG. In Fig. 3, 30 is an input DC power supply;
31 is a switching means, 32 and 34 are inductors, and 33 is an energy storage means composed of a capacitor and a control transformer, whose input terminals are connected to A,
B, output terminals are shown as C and D. Further, 36 is a smoothing circuit, and 37 is a load. In each of the above blocks, an input DC power supply 30, a switching means 31,
The inductor 32 and the input terminals A and B of the energy storage means 33 are connected in series, and the inductor 3 is connected to the output terminals C and D of the energy storage means 33.
4. A smoothing circuit 36 is connected, and a load 37 is connected to the smoothing circuit 36.

In FIG. 3, when the switching means 31 is turned on, energy is injected from the input DC power supply 30 into the energy storage means 33, physically as a current i ₁ . The current i ₁ has a sinusoidal current waveform by providing a resonant circuit in the path through which the current flows, as in the conventional example. The above-mentioned resonant circuit is a circuit composed of the inductor 32 and the impedance on the input terminals A and B sides of the energy storage means 33.

In this way, energy is stored in the energy storage means 33 according to the current i ₁ flowing between the input terminals A and B of the energy storage means 33, and the amount of energy is equal to the energy injected by the current i ₁ per unit time. amount, that is, switching means 3
In addition, the above-mentioned energy amount also depends on the energy storage capacity of the energy storage means 33.

Next, the output terminal CD of the energy storage means 33
When the voltage between them becomes higher than the voltage of the load 37, the energy stored in the energy storage means 33 is transferred to the output terminal C of the energy storage means 33,
i ₂ from D to the smoothing circuit 36 via the inductor 34
is supplied as current energy. The smoothing circuit 36 smoothes the current i ₂ and supplies energy as a DC voltage to the load connected to the output terminals a and b of the constant voltage power supply.

Further, the current i ₂ is generated by forming a resonant circuit with the impedance between the input terminals C and D of the energy storage means 33 and the inductor 34.
The current waveform becomes a sine wave.

Here, the amount of energy released from the energy storage means 33 is determined by the difference between the voltage value between the output terminals C and D indicating the amount of energy stored in the energy storage means 33 and the voltage value of the smoothing circuit 36. It's decided.

With the configuration shown in Figure 3, energy can be transferred from the input DC voltage as DC voltage to the output terminals a and b of the constant voltage power supply, but control to stabilize the DC voltage at the output terminals a and b is necessary. As a method, there are the methods described below. The amount of energy that can be stored in the energy storage means 33 and the switching frequency of the switching means 31 for injecting energy into the energy storage means 33 are set to the DC voltage between the output terminals a and b of the constant voltage power supply. By controlling accordingly, a stable DC voltage can be obtained. Even if such a control method is used, the characteristics of the conventional constant voltage power supply device that utilizes the resonance phenomenon are not impaired.

Next, we will explain embodiments of the present invention that utilize the above circuit configuration and operation, but first, we will explain the variable inductance used in the present invention, which can change the inductance of the first winding depending on the supplied signal. An example of a control transformer having an inductance function will be described. FIG. 4 is a block diagram of the control transformer, FIG. 5 is a characteristic diagram thereof, and FIG. 6 is a diagram showing equivalent symbols. In Fig. 4, AC winding Na,
Nb, Nc, and Nd are provided, a DC winding Ne is provided on the center leg, and a DC current source I is connected between control terminals E and F of the DC winding Ne. Further, A and B are input terminals, and C and D are output terminals. Above AC winding
Na and Nb are connected in series to form the first winding, and are wound in such a way that the magnetic flux induced in the center leg by the alternating current from input terminals A and B is canceled out. In other words, the magnetic fluxes Φ ₂ and Φ ₂ ' induced by the AC windings Na and Nb are equal. Further AC winding
Nc and Nd are connected in series to form the second winding and connected to output terminals C and D, and the AC winding
It is formed at a certain turn ratio for Na and Nb.

Here, by flowing a DC current from the DC current source I, a magnetic flux Φ ₁ is generated in the current winding Ne, and the balance between the magnetic fluxes Φ ₂ and Φ ₂ ' induced by the AC windings Na and Nb is lost, and the input The inductance between terminals A and B changes. Figure 5 shows the change in inductance between input terminals A and B due to direct current. Therefore, the inductance between input terminals A and B can be controlled in a decreasing direction by direct current applied between control terminals E and F.

An equivalent symbol of a control transformer having the functions described above is shown in FIG. 6, and an embodiment of the present invention using this will be described below with reference to FIG. 7 and subsequent drawings.

FIG. 7 is a circuit configuration diagram of the first embodiment of the present invention, in which components having the same functions as those already explained in FIG. 1 are given the same reference numerals. Also,
8a, b, c, and d are operation waveform diagrams of each part in FIG. 7.

In FIG. 7, 13 and 14 are the switching elements 3 and 4 and the unidirectional element 1 connected in series thereto.
1 and 12, the switching means conducts only in one direction, 15 is an inductor, and 16 is a sixth
A control transformer as illustrated in the figure constitutes the energy storage means 17 together with the capacitor 7. 1
8 is a DC current control circuit, and 19 is a control circuit for stabilizing the DC voltage at output terminals a and b. Input terminals A and B of the control transformer 16 are connected to both ends of the capacitor 7, and the energy storage means 17
The output terminals C and D serve as output terminals of the energy storage means 17.
Output terminals C and D of the control transformer 16 are connected to the rectifier circuit 8.
(For example, a bridge type composed of diodes,
The control terminals E and F are connected to the output terminal of a DC current control circuit 18. The output terminal of the rectifier circuit 8 is connected to a smoothing capacitor 9 at output terminals a and b of the constant voltage power supply, and the rectifier circuit and the smoothing capacitor form a smoothing circuit 36 in FIG. 3. The control circuit 19 is composed of a reference voltage source, an error amplifier, an oscillation circuit, a distribution circuit, etc. which are already known.
The error amplifier compares and amplifies the voltage difference between the DC voltage at the output terminals a and b of the constant voltage power supply supplied to the input terminal of the control circuit 19 and a reference voltage given in advance, and the oscillation frequency of the oscillation circuit is determined by the error amplifier. The switching elements 3 and 4 are turned on and off alternately in the distribution circuit, and the signal from the error amplifier is also output to the DC current control circuit 18, Reference numeral 18 supplies a direct current according to the input signal to the control terminals E and F of the control transformer 16 to change the inductance value between the input terminals A and B of the control transformer 16.

The operation of the constant voltage power supply device of this embodiment configured as described above will be explained below with reference to the operation waveform diagram of each part in FIG. 8. In Figure 8, a
are the currents i and b flowing from the switching elements 3 and 4 to the inductor 15 and the energy storage means 17.
is the current i _L flowing between the input terminals A and B of the control transformer 16, c is the current i O flowing between the output terminals C and D of the control transformer 16, and d is the current i _O flowing between the output terminals C and D of the control transformer 16.
The graph shows the respective operating waveforms of the voltage across the terminals V _C , and the horizontal axis is the time axis.

Since this embodiment also utilizes the resonance phenomenon shown in FIG. 1, the explanation that overlaps with the conventional example will be omitted. First, when the switching element 3 is turned on, the current i causes the inductor 15 and the energy storage means 17 to
A series resonant circuit consisting of the capacitor 7 inside and the inductance of the primary winding of the control transformer 16 forms a sine wave, and the period is determined by each constant of the series resonant circuit. The energy generated by the current i is stored in the energy storage means 17, but since the switching means 13 is a unidirectional switch as described above, there is no path for the energy in the energy storage means 17 to move elsewhere. The amount of energy remains stored, and the amount of stored energy is manifested in the phenomenon of an increase in the voltage value of the voltage V _C across the capacitor 7. The above operation results in a waveform from time t ₁ to time t ₃ in FIG. 8. Further, during the above period, the energy storage means 1
The current i _L flowing between the input terminals A and B of the control transformer 16 in the capacitor 7 has a current waveform corresponding to the voltage across the capacitor 7 .

Here, the time point when the voltage Vc across the capacitor 7 becomes higher than the DC voltage V _O of the output terminals a and b converted to the primary side of the control transformer 16 (time t ₂ in FIG. 8).
(which is V _c2 in figure d), the energy of the capacitor 7 is transferred from between the output terminals C and D of the control transformer 16 to the output terminals a and b of the constant voltage power supply via the rectifier circuit 8 and the smoothing capacitor 9. It is supplied to the load 10 as a DC voltage. The current at this time is the current i _O between the output terminals C and D of the control transformer 16. Further, the current i _O has a sinusoidal waveform due to a resonant circuit constituted by the effective leakage inductance as an inductor of the control transformer 16 and the energy storage means 17, and the period is determined by each constant. The above operation results in a waveform from time t ₂ to time t ₄ in FIG. 8. Thereafter, the voltage Vc across the capacitor 7 decreases due to the current i _L flowing between the input terminals A and B of the control transformer 16, and at time _t1 ' when the switching element 4 is turned on, the voltage _Vc across the capacitor 7 decreases. V _c1 .
Thereafter, from time t ₁ ′ to time t ₁ ″, the phenomenon from time t ₁ to time t ₁ ′ described above appears with the polarity reversed, and when the switching element 3 is turned on at time t ₁ ″,
The waveform becomes exactly the same as the waveform from time _t1 , and the same phenomenon repeats.

Next, a control method for stabilizing the DC voltage V _O at the output terminals a and b will be described. The basic principle of the control method is that the voltage on the primary side of the control transformer 16 (in FIG. 7, the voltage across the capacitor 7
Energy is transferred to the secondary side of the control transformer 16 when the voltage (equal to V _C ) becomes higher than the primary side conversion value of the control transformer 16 of the DC voltage V _O at the output terminals a and b of the constant voltage power supply device. The output voltage V _O is stabilized by controlling the amount of energy generated by the
Moreover, the voltage V _C on the primary side of the control transformer 16 is
Since it indicates the amount of energy stored in the energy storage means 17, controlling the energy stored in the energy storage means 17, in other words, stabilizes the output voltage V _O.

A control method that can realize the above method will be specifically described below.

First, as a method of storing energy in the energy storage means 17, there is a switching frequency of the switching elements 3 and 4. The above switching frequency controls the amount of energy injected into the energy storage means 17 per unit time (corresponding to the amount of current i in FIG. 7). By utilizing the fact that the amount of energy injected per hour increases (decreases) and the output energy increases (decreases) according to the injected energy as explained in the operation above, Compare the DC voltage _VO and the reference voltage in the control circuit 18,
The purpose is to control the switching frequency according to the difference.

In addition, input terminals A and B of the control transformer 16
The inductance value between determines the amount of energy stored in said energy storage means 17.
Therefore, input terminals A and B of the control transformer 16
When the inductance value between is increased (decreased), the amount of energy stored in the energy storage means 17 increases (decreases), and as explained in the above operation, the output energy increases in accordance with the amount of stored energy. Taking advantage of this fact, the DC voltage V _O between the output terminals a and b of the constant voltage power supply device is compared with the reference voltage in the control circuit 18, and a signal corresponding to the difference is used to control the DC current control circuit. A direct current flows from 18 to the control terminals E and F of the control transformer 16, and control is performed by changing the inductance value between the input terminals A and B of the control transformer 16.

Therefore, the present invention effectively combines the method of changing the switching frequency and the method of changing the inductance value between the input terminals A and B of the control transformer 16, thereby changing the switching frequency and the inductance value, respectively. In addition, as can be seen from the operating waveform in Figure 8, all the flowing currents are sinusoidal, and the direct current at the output terminal is reduced without impairing the characteristics of a constant voltage power supply that utilizes the resonance phenomenon. It can stabilize the voltage.

FIG. 9 shows a second embodiment of the present invention, and FIG. 10 shows its operating waveforms. In explaining the second embodiment, parts having the same functions as those described in the first embodiment (Fig. 7) are given the same reference numerals.
Furthermore, in the explanation of the operations, cases in which the same operations are performed will not be particularly explained.

The difference in circuit configuration from the first embodiment is the configuration of switching means 21 and 22 in FIG. 9. The switching means 21 and 22 are
The switching elements 3 and 4 are connected so as to be electrically conductive in a direction opposite to the electrically conductive direction of the switching elements 3 and 4. That is, the unidirectional element 1 is connected in parallel with the switching elements 3 and 4 so as to be reverse biased with respect to the input DC power supplies 1 and 2.
1 and 12 (for example, diodes) are connected. The unidirectional elements 11 and 12 are configured to transfer a part of the energy stored in the energy storage means 17 to the input DC power source 1 or 2 via the unidirectional element 11 or 12 as regenerative energy. be.

Next, the operation will be explained with reference to the operation waveform diagram in FIG. 10. In addition, a, in Figure 10
b, c, and d are operation waveform diagrams at the same locations as a, b, c, and d in FIG. 8. Since the basic operation is the same as that of the first embodiment described above, here, the switching means 21 and 22 have a different configuration from the first embodiment, so that the input DC power supply 1, The phenomenon of current flowing to 2 or 2 will be described with reference to FIGS. 9 and 10. First, when the switching element 3 is turned on at time _t1 , the current i flowing through the system is caused by the resonance formed by the inductance between the inductor 15, the capacitor 7 in the energy storage means 17, and the input terminals A and B of the control transformer 16. The circuit flows as a sinusoidal waveform (from time t ₁ to time
_t3 ). Time t ₃ when the sinusoidal current i finishes flowing
When the voltage V _C across the capacitor 7 becomes higher than the input DC power supply 1, the energy in the energy storage means 17 is regenerated as a regenerative current to the input DC power supply 1 via the inductor 5 and the unidirectional element 11. from time t ₃ to time t ₅ ). By utilizing the above phenomenon, the energy storage means 17
The amount of energy stored within can be greatly changed. Moreover, the above phenomenon is caused by the switching frequency of switching elements 3 and 4 and the control transformer 1.
It is closely related to the inductance value between input terminals A and B of 6. In other words, the energy storage means 1
This is because the amount of regenerated energy is determined by the amount of energy stored in 7. Therefore, the control method for stabilizing the voltage V _O at the output terminals a and b of the constant voltage power supply device can be performed in exactly the same manner as in the first embodiment, since all the flowing currents are sinusoidal. , it is possible to stabilize the DC voltage at the output terminal without impairing any of the characteristics of the constant voltage power supply device that utilizes the resonance phenomenon.

Next, a third embodiment of the present invention is shown in FIG. 11, and an operating waveform diagram thereof is shown in FIG. 12. Figure 11, 1st
In FIG. 2, parts having the same functions as those described in the first embodiment (FIG. 7) are given the same reference numerals. This third embodiment changes the switching element 1 from the half-bridge configuration of the first embodiment.
The structure is replaced with a stone structure, and the basic operation is almost the same as the first embodiment.

In FIG. 11, for the input DC power supply 26, an inductor 15, an energy storage means 17,
The switching means 25 is connected in series with a unidirectional element 24 and a switching element 23, similar to the switching means 13 and 14 in FIG. 7. Further, the control circuit 28 for controlling the switching frequency of the switching element 23 has the circuit configuration shown in the first embodiment except for the distribution circuit.

The operation of the third embodiment will be explained below with reference to FIG. 12, but parts that operate the same as those of the first embodiment will be omitted, and only the different parts will be described. Unlike the first embodiment, since there is only one switching means, the energy storage means 1
The energy to be injected into 7 will be injected only from one direction. Therefore, the operating waveform diagram of FIG. 8 of the first embodiment and the operating waveform diagram of FIG. 12 of the third embodiment differ only in the waveform of the current i flowing through the system. Regarding the operation of other parts, see
Since the principle is exactly the same as that of the embodiment, the operating waveforms are also the same. Therefore, the control method is exactly the same to control the DC voltage V _O between the output terminals a and b of the constant voltage power supply.
can be stabilized.

As described above, the first embodiment of the present invention can be configured with a single switching means like the third embodiment, and the resonance phenomenon can be controlled by the same control method as in the first embodiment. It is possible to stabilize the DC voltage at the output terminal without impairing the characteristics of the constant voltage power supply device using the constant voltage power supply.

Next, a fourth embodiment of the present invention is shown in FIG. 13, and an operating waveform diagram thereof is shown in FIG. 14. Figure 13, 1st
In FIG. 4, parts having the same functions as those described in the second embodiment are given the same reference numerals. In this fourth embodiment, the half-bridge configuration of the second embodiment is replaced with a configuration using one switching element, and the basic operation is almost the same as that of the second embodiment.

In FIG. 13, for the input DC power supply 26, an inductor 15, an energy storage means 17,
A switching means 27 is connected in series, and the switching means 27 has a unidirectional element 24 and a switching element 23 connected in parallel, similar to the switching means 21 and 22 of FIG. Further, the control circuit 28 for controlling the switching frequency of the switching element 23 has the circuit configuration shown in the second embodiment except that the distribution circuit is removed.

The operation of the fourth embodiment will be explained below with reference to FIG. 14, but parts that operate the same as those of the second embodiment will be omitted, and only the different parts will be described. Unlike the second embodiment, since there is only one switching means, the energy storage means 17
The injection energy will be injected only from one direction. Therefore, compared to FIG. 10 of the operating waveform diagram of the second embodiment, only the waveform of the current i flowing through the system differs. Furthermore, since the operation of other parts is based on exactly the same principle as the second embodiment, the operation waveforms are also the same. Therefore, the control method is exactly the same, and the output terminals a,
It is possible to stabilize the DC voltage V _O between b.

As described above, the second embodiment of the present invention can be configured with a single switching means like the fourth embodiment, and can control the resonance phenomenon by using the completely same control method as the second embodiment. It is possible to stabilize the DC voltage at the output terminal without impairing the characteristics of the constant voltage power supply device using the constant voltage power supply.

Note that, as an example of the present invention, a half-bridge configuration and a circuit configured with one stone have been described, but the circuit configuration is not limited to the above, and the same can be applied to a full-bridge configuration using, for example, four switching means. The control method can stabilize the DC voltage at the output terminal.

In addition, although the switching means has a circuit configuration in which a switching element and a unidirectional element are combined, it is also possible to use a thyristor or transistor that conducts in only one direction, or a MOSFET that conducts in both directions. It can also be used for.

Although a DC power source is used as an input power source in the embodiment of the present invention, it goes without saying that a DC voltage obtained by using an AC power source in a rectifier circuit can also be used as an input DC power source.

Effects of the Invention As is clear from the above description, the present invention uses a switching means that is connected to an input DC power source and conducts only in one direction, and further comprises an energy storage means consisting of an inductor, a capacitor, and a control transformer. By using a resonant circuit, an amount of energy can be effectively stored in the energy storage means, and this amount of energy is transferred to the first winding of the control transformer by the first control means in accordance with the DC voltage at the output terminal. The DC voltage at the output terminal of the constant voltage power supply is stabilized over a wide range of input/output fluctuations by controlling the inductance value by varying it, and by controlling the switching frequency of the switching means by varying the second control means. can be done. Furthermore, because it does not impair the low switching loss and low radiation noise characteristics of conventional constant voltage power supplies, it has the advantage of being able to be used for acoustic and completely sealed power supplies, which were difficult to use in the past. .

[Brief explanation of drawings]

Fig. 1 is a circuit configuration diagram of a conventional constant voltage power supply device using resonance phenomenon, Fig. 2 is its operating waveform diagram, Fig. 3 is a basic circuit diagram of the present invention, and Figs. 6 is a block diagram, characteristic diagram, and equivalent symbol diagram of the control transformer used in the present invention, FIGS. 7 and 8 are a circuit block diagram and its operating waveform diagram of the first embodiment of the present invention, and FIG. 9 and 10 are circuit configuration diagrams and operation waveform diagrams of the second embodiment of the present invention, and FIGS. 11 and 12 are circuits in which only one switching means is used in the first embodiment. The configuration diagram and its operating waveform diagrams, FIGS. 13 and 14, show the switching means of the second embodiment.
FIG. 3 is a circuit configuration diagram and an operation waveform diagram when the circuit is configured with the following. 1, 2, 26, 30...Input DC power supply, 3, 4,
23... Switching element, 7... Capacitor, 8...
Rectifier circuit, 9... Smoothing capacitor, 10, 37... Load, 11, 12, 24... Unidirectional element, 13, 1
4, 21, 22, 25, 27, 31... switching means, 15... inductor, 16... control transformer, 17, 33... energy storage means, 18... direct current control circuit, 19... control circuit, 20... oscillation circuit, 32 , 34...inductor, 36... smoothing circuit.

Claims (1)

[Claims] 1. A first power source connected in series that operates on and off with respect to a first and second input DC power source connected in series.
and a second switching means that conducts only in one direction are connected in parallel, and an inductor and an energy A series connection circuit formed by connecting storage means is connected, and a smoothing circuit is connected to an output terminal of the energy storage means to obtain a DC voltage at the output terminal of the smoothing circuit, and the energy storage means is The control transformer includes a capacitor and a first winding connected to both ends of the capacitor, and the first winding of the control transformer is connected to the input terminal of the energy storage means, and the second winding of the control transformer is connected to the input terminal of the energy storage means. are respectively connected to the output terminals of the energy storage means, and further for controlling the inductance of the first winding of the control transformer as a function of the DC voltage at the output terminal of the smoothing circuit; and second control means for controlling the switching frequencies of the first and second switching means as a function of the DC voltage at the output terminal of the circuit. 2. The first and second switching means are characterized in that the first and second unidirectional elements are connected in parallel to the first and second switching elements so as to conduct in a direction opposite to the direction of conduction. A constant voltage power supply device according to claim 1. 3 Connecting in series an inductor, an inductor, and an energy storage means to an input DC power source, which conducts only in one direction and which operates on and off, and connecting a smoothing circuit to the output terminal of the energy storage means to generate the smoothing circuit. It is configured to obtain a DC voltage at the output terminal, and the energy storage means is composed of a capacitor and a control transformer having a first winding connected to both ends of the capacitor, and the first winding of the control transformer is connected to the first winding of the control transformer. A second winding of the control transformer is connected to an input terminal of the energy storage means, respectively to an output terminal of the energy storage means, and a first winding of the control transformer is connected as a function of the DC voltage at the output terminal of the smoothing circuit. A first control means for controlling the inductance of the winding, and a second control means for controlling the switching frequency of the first and second switching means as a function of the DC voltage at the output terminal of the smoothing circuit. Constant voltage power supply. 4. The constant voltage power supply device according to claim 3, wherein the switching means has a unidirectional element connected in parallel to the switching element so as to conduct in a direction opposite to the direction of conduction of the switching means.