JPS58127565A - Constant-voltage power source - Google Patents

Abstract

PURPOSE:To enable to stabilize the output DC voltage to the wide input/output variations by connecting a resonance condenser of a DC/DC converter in parallel with a variable inductance and controlling it. CONSTITUTION:Switching elements 3, 4 which turn ON and OFF are connected in series with both termninals of input DC power sources 1, 2, and a resonance codenser 7 and the primary coil 5a of a conversion transformer 5 are connected in series with the intermediate points between the elements 3, 4 and the sources 1, 2. The output voltage from the secondary coil 5b of the transformer 5 is applied through a rectifier 8 to a comparator 13, which compares it with a reference voltage ES. This output of the comparator 13 is supplied through a DC current controller 14 to a control transformer 11, thereby controlling the inductance between the input terminals A and B. The signal voltage obtained from the secondary coil of the transformer 11 is transmitted as a discharge energy to the output terminals a and b of a DC/DC converter through a rectifier 12.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a series resonant DC-
This invention relates to a constant voltage power supply device using a DC converter.

A slave switching regulator is generally of the PWM type that stabilizes the output DC voltage by controlling the duty ratio of the on/off operation of the switching element. However, the disadvantage of the above method is that there is a period in which the current and voltage change sharply when the switching element is turned on and off, resulting in large switching losses and large unnecessary radiation noise. Therefore, if the above switching regulator is considered as a power supply for audio equipment, it is necessary to insert a filter in the input/output section to greatly attenuate unnecessary radiation noise, and also to take noise countermeasures such as applying a completely sealed shield. However, there are problems such as increased cost 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 is proposed.
A complete DCC has been proposed.

In this series resonant DC-DCC set, due to the series resonant circuit, the current waveform when the switching element is conductive becomes a sine wave, and the current and voltage intersect at zero when the switching element is turned on and off. Therefore, switching loss and unnecessary radiation noise are significantly reduced. However, in the above series resonant DC-DCC set, it is difficult to control input/output fluctuations to stabilize the output DC voltage without impairing the above characteristics.

Based on the above points, the conventionally used series resonant type D
The circuit configuration and operation of the C-DCC complete set will be explained.

FIG. 1 is a basic circuit configuration diagram of a conventional series resonant DC-DCC set, and FIGS. 2(a), (b), and (C) are its operating waveform diagrams. In FIG. 1, switching elements (for example, transistors, thyristors, etc.) 3 and 4 that perform on/off operations are connected in series between the terminals of two input DC power supplies 1 and 2 connected in series, and the input A series-connected resonance capacitor 7 and a primary winding 6a of a conversion transformer 6 are connected between the midpoints of the DC power supplies 1 and 2 and the switching elements 3 and 4. Further, a rectifier circuit 8 and a smoothing capacitor 9 are connected to the secondary winding 6b of the conversion transformer 6.
is connected, and a load 10 is connected to its output terminals a and b. Here, the resonant current flowing in the series resonant circuit composed of the resonant capacitor 7 and the effective leakage inductance of the conversion transformer 6 is expressed as L, and the charging voltage of the resonant capacitor 7 is expressed as V.
. shall be. Figure 2 (-), (b).

(C) shows the on/off states of the switching elements 3 and 40;
The above resonance current and charging voltage V. The operating waveform diagram is shown. In FIG. 2, the switching element 3 is turned on at time t1, and the resonance current becomes positive between time t1 and time t2, the cycle of which is determined by the capacitance of the resonance capacitor 7 and the effective leakage inductance.

Next, during time t2≦t≦t3, the switching element 3
, 4 are off, the resonant current becomes zero, and the charging voltage V of the resonant capacitor 7. 1 also remains constant since there is no discharge path. When the switching element 4 is turned on at time t3, the operating waveform is opposite in positive and negative to the operating waveform during time t1≦t≦eclipse, and thereafter, the switching element 3 is turned on again.
When turned on, the same operation repeats. Further, the resonant current is transmitted to the secondary side via the conversion transformer 6, and after rectification and smoothing, is supplied to the load 10 as a predetermined output DC voltage.

The above is the circuit configuration and operation of the conventional series resonant type DC-DC converter. As a means for controlling the series resonant type DC-DC converter, the capacitance value of the resonant capacitor 7 is controlled. , switching element 3
, 4 is proposed to control the off-state period, that is, the switching frequency. However, in either case, control was difficult because the amount of current flowing into the resonance current did not change.

The present invention provides the above series resonant DC-DCC set,
The present invention aims to provide a constant voltage power supply device that can stabilize the output DC voltage over a wide range of input/output fluctuations without impairing the characteristics of the resonance system.

The present invention will be described below, but first a control transformer having a variable inductance function used in the present invention will be described. FIG. 3 is a schematic configuration diagram showing an example,
FIG. 4 is a characteristic diagram thereof, and FIG. 5 is a diagram showing symbols of equal constraints. In Fig. 3, AC windings N, Nb, No, and Nd are provided on each of the legs of a combination of an E-type core and an I-type core, or a combination of two E-type cores, and a DC winding is provided on the center leg. N. and a control terminal Σ of the DC winding N0.

A direct current source I is connected between the two terminals. Also, A, B
is an input terminal, and C2D is an output terminal. Above AC winding N
, Nb are connected in series to constitute the first winding, and are wound in such a way that the magnetic flux induced in the center leg by the alternating current from the input terminals A and B is canceled out. That is, the magnetic flux Φ2. induced by the AC windings Na and Nb. This is a state in which Φ2 is equal. Furthermore, the AC winding N. , Nd are connected in series to the output terminals C and D to form a second winding, and are formed at a constant nine turns ratio with respect to the AC windings Na and Nb.

Here, magnetic flux Φ1 is caused to flow through the DC winding N by flowing a DC current from the DC current source I. occurs, and the inductance between input terminals A and B changes. Input terminal A with direct current,
Figure 4 shows the change in inductance between B and B. Therefore,
DC current applied between control terminals E and F causes input terminal A to
, B can be controlled in a decreasing direction.

The isometric symbol of the control transformer described above is shown in FIG. 5, and embodiments of the present invention using this symbol will be described below with reference to FIG. 6 and subsequent drawings. Figure 6 shows the first embodiment of the present invention.
In this circuit configuration diagram of the embodiment, parts having the same functions as those explained in FIG. 1 are given the same reference numerals. Also,
Figure 7(a),(b).

(C), (d), (@), and (f) are operation waveform diagrams in FIG. 6.

In FIG. 6, 11 is a control transformer as illustrated in FIG. 3, 12 is a rectifier circuit, 13 is a comparison circuit, and 14 is a DC current control circuit. Input terminal A of the transformer 11,
B is connected to both ends of the resonance capacitor 7, output terminals C and D are connected to the rectifier circuit 12, and control terminals E and F are connected to the output terminal of the DC current control circuit 14. Further, the output side of the rectifier circuit 12 is an output terminal a of a DC-DC converter.

connected to b. The comparison circuit 13 has input terminals supplied with the DC output voltage obtained at the output terminals a and b and a predetermined reference voltage E8, compares the respective voltage values, and calculates the difference signal. Supplied to the DC current control circuit 14. The DC current generator 14 supplies a DC current of a magnitude corresponding to the output signal from the comparison circuit 13 to the control terminals Σ and F of the control transformer 110, thereby increasing the voltage between the input terminals A and B of the control transformer 11 (first volume). It changes the inductance of the wire) and constitutes the control means.

Next, the operation of the embodiment shown in FIG. 6 will be explained with reference to the operational waveform diagram shown in FIG. 7. Note that the explanation of the operation of the parts that overlap with the conventional example shown in FIG. 1 will be omitted. The period of the resonant current flowing through the resonant circuit is determined by the effective leakage inductance of the conversion transformer 6, the capacitance of the resonant capacitor 7, and the inductance between the input terminals A and B of the control transformer 11. Further, the control current LL1 flowing between the input terminals A and B of the control transformer 11 becomes a continuous sine wave, and is synchronized with the resonance current S.

Further, the charging voltage v0 of the resonance capacitor 7 increases in proportion to the sum of the resonance current and the control current "L".

The above state is from time t1 when switching element 3 is turned on to time t1. At time /, control transformer 1
The voltage induced between output terminals C and D (second winding) of DC-DC converter 1 (second winding) becomes higher than the DC output voltage obtained between output terminals a and b of DC-DC converter (-), and the resonance capacitor 7 The charging energy stored in is transmitted as discharge energy to the output terminals a and b of the DC-DC converter via the control transformer 11. This state changes from time t1 to t2.
It is. Further, the output current "L2" of the control transformer 11 flowing during the above period becomes a sine wave, and its period is determined by the capacitance of the resonance capacitor 7 and the effective leakage inductance of the control transformer 11. Due to the above phenomenon, the charging voltage V. decreases to vc4 (time t2) as the output current "L2" of the control transformer 11 flows, and the control current "L" remains until time t3 when the next switching element 4 is turned on.
It further decreases due to l and becomes vo2. Thereafter, time t3
The phenomenon of polarity reversal is repeated from to time t6, and after the switching element 3 is turned on at time t6, the operating waveform becomes the same as that from time t1. In addition, the factor that determines the amount of current in the resonance current is the initial charging voltage v of the resonance capacitor 7.
0, by changing the value of the initial charging voltage v0, the amount of current transmitted to the secondary side via the conversion transformer 6 changes, and the energy supplied to the output terminals a and b of the DC-DC converter changes. can be controlled. The initial charging voltage v0 is -V at time t1 in FIG. 2 and v02 at time t3. Above initial charging voltage (-■(+2+
vc2 ) is related to the output current LL2 of the control transformer 11 as described above, and the amount of output current "L2" of the control transformer 11 is also related to the control current "Ll". Therefore, in order to change the output DC voltages obtained at the output terminals a and b, a control configuration that changes the amount of the control current kL1 may be used.

That is, the present invention utilizes the fact that the amount of control current kL1 is inversely proportional to the inductance between the input terminals A and B of the control transformer 11.

FIG. 8 is a circuit configuration diagram of a second embodiment of the present invention, and FIG. 9 is an operation waveform diagram of each part thereof. In addition, in Fig. 8,
Components having the same functions as those explained in FIG. 6 are given the same reference numerals. The difference between the circuit in FIG. 8 and the circuit in FIG. 6 is that the diodes 15 and 16 are conductive in the direction opposite to the conduction direction of the switching elements 3 and 4.
That is, the switching elements 3 and 4 are connected in parallel so as to be reverse biased with respect to the input DC power supplies 1 and 2. This embodiment is basically the same as the operating principle of the first embodiment shown in FIG.
The energy is transferred to the input DC power source 1 or 2 as regenerative energy via the input DC power source 1 or 2. Its operation will be explained with reference to FIG. The output from the control transformer 11 is omitted. Time t when switching element 3 is turned off
At 2 o'clock, the charging energy stored in the resonance capacitor 7 is regenerated as a regenerative current to the input DC power supply 1 via the conversion transformer 6 and the diode 15. The above phenomenon is the 9th
This is the period from time t2 to time t2 in the waveform diagram of the resonant current shown in FIG. Therefore, due to the output current 2 of the control transformer 11 and the regenerative current, the charging voltage V of the resonance capacitor 7 at time t3 when the switching element 4 is turned on. 6
changes significantly. Thereafter, the same phenomenon will be repeated. The control operation by the control means is exactly the same as in the first embodiment shown in FIG.

A third embodiment of the invention is shown in FIG. This third embodiment further expands the range of control over fluctuations in the number of people in the first embodiment shown in FIG. Components having similar functions are given the same reference numerals. In FIG. 10, 17 and 18 are diodes, and 19 and 20 are regenerative coils, which are connected in series. in this case,
The diodes 17 and 18 and the regenerative coils 19 and 20 are connected in parallel to the series connection circuit of the switching elements 3 and 4 and the primary winding 5a of the conversion transformer 5, respectively, and the diodes 17 and 18 are The elements 3 and 4 are connected so as to conduct in a direction opposite to the conduction direction of the elements 3 and 4, that is, to be reverse biased with respect to the input DC power source 1°2.

This embodiment still utilizes the regenerative current from the resonant capacitor 7 described in the second embodiment (FIG. 8), but the regenerative current does not pass through the conversion transformer 6.
Diodes and regenerative coils (17 and 19) connected in series
Alternatively, the difference is that the energy is regenerated to the input DC power source 1 or 2 via the input DC power sources 18 and 20) and therefore does not become the output energy of the DC-DC converter. Furthermore, regenerative coil 1
By changing the inductance of 9 or 2 degrees, the period of the regenerative current can be changed arbitrarily. The control operation by the control means is completely the same as in the first embodiment.

Note that in the above embodiments of the present invention, two switching elements are used.
Although this was explained in the case of a two-bridge configuration using
Similar effects can be obtained even in the case of a full bridge configuration using four switching elements. Furthermore, although the effective leakage inductance of the conversion transformer 5 was used as the inductance of the series resonant circuit in each of the above embodiments, another co-transfer coil may be inserted in series between the resonance capacitor and the primary winding of the conversion transformer. , it is also possible to configure it using the inductance of the resonance coil.

Furthermore, the control transformer having a variable inductance function used in the present invention is not limited to the configuration shown in FIG. Any wire can be used as long as it can vary the inductance of the first winding according to the conditions.

As described above, according to the present invention, with a simple circuit configuration,
It is capable of stabilizing the output DC voltage over a wide range of input/output fluctuations while taking advantage of the features of the series resonant DC-DC converter, and has extremely high industrial value.

[Brief explanation of the drawing]

Figure 1 is a circuit configuration diagram of a conventional series resonant DC-DC converter, Figures 2 (a), (b), and (c) are its operating waveform diagrams, and Figure 3 is a diagram of the control transformer used in the present invention. A schematic diagram showing a configuration example, FIG. 4 is a characteristic diagram thereof, FIG. 6 is an equivalent symbol diagram thereof, FIG. 6 is a circuit configuration diagram of the first electro-male side of the present invention, FIG. 7 (a), (b) , (C) l
(d), (e). (f) is its operating waveform diagram, FIG. 8 is a circuit configuration diagram of the second embodiment of the present invention, and FIGS. 9(a), (b), (C
), (d), (e). (f) is an operating waveform diagram thereof, and FIG. 10 is a circuit configuration diagram of a third embodiment of the present invention. 1.2...Input DC power supply, 3,4...
Switching element, 5...Conversion transformer, 5a
...Primary winding, 6b...Secondary winding, 7
... Resonance capacitor, 8 ... Rectifier circuit, 9 ... Smoothing capacitor, 10 ...
・Load, 11...Control transformer, 12...
... Rectifier circuit, 13... Comparison circuit, 14...
...DC current control circuit, 15, 16.17.18 ・
...Diode, 19.20...Regeneration coil, a, b...Output terminal. Name of agent: Patent attorney Toshio Nakao and one other person
〉 y -6g 13 Figure 14 Figure 5 Figure 16 Figure 17 Figure Time Figure 8

Claims (1)

[Scope of Claims] (1) A series connection circuit including at least a switching element that operates on and off, a primary winding of a conversion transformer, and a resonant capacitor is connected to an input DC power source, and the conversion transformer A DC-DC converter configured to connect a first rectifying circuit and a smoothing circuit to the secondary winding of the converter to obtain a DC output voltage at an output terminal, and a first winding connected in parallel to the resonant capacitor. a control transformer having a second winding for output extraction, and capable of changing the inductance of the first winding depending on an electric signal supplied; and a second winding of the control transformer. a second rectifier circuit that rectifies a signal voltage and supplies the signal voltage to an output terminal of the DC-DC converter;
A constant voltage power supply device, characterized in that it comprises control means for controlling the inductance of the control transformer as a function of the DC output voltage obtained at the output terminal of the converter. (2. The constant voltage power supply according to claim (1), characterized in that a unidirectional element is connected in parallel to the switching element so as to conduct in a direction opposite to the conduction direction of the switching element. (3) In the description of claim (1), a circuit in which a coil and a unidirectional element that conducts in a direction opposite to the conduction direction of the switching element are connected in series is referred to as a switching element. A constant voltage power supply device characterized in that the transformer is connected in parallel to a series connection circuit of a primary winding of a conversion transformer.