JPH036735B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a constant voltage power supply device using a series resonant DC-DC converter that stabilizes the output DC voltage.

Conventional configuration and its problems Conventional switching regulators generally use the PWM method, which 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 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 the above switching regulator is considered as a power supply for audio equipment, it is necessary to take noise countermeasures such as inserting a filter in the input/output section to greatly attenuate unnecessary radiation noise, and also applying a completely sealed shield. Therefore, 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 control input/output fluctuations in order to stabilize the output DC voltage without impairing the above characteristics.

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,
thyristor, etc.) are connected in series, and the primary winding 5a of a conversion transformer 5 is connected in series between the input DC power supplies 1 and 2 and the midpoints of the switching elements 3 and 4.
and capacitor 7 are connected. Further, a rectifier circuit 8 and a smoothing capacitor 9 are connected to the secondary winding 5b of the conversion transformer 5, and a load 10 is connected to its output terminals a and b. Here, conversion transformer 5
The effective leakage inductance and the capacitor 7 form a series resonant circuit. Let i be the resonant current flowing through the series resonant circuit, and let Vc 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 Vc.
The operating waveform diagram is shown. In FIG. 2, the switching element 3 is turned on at time _t1 , and the resonant current i is determined by the effective leakage inductance and the capacitance of the capacitor 7, and this sinusoidal resonant current i flows from time _t1 to time _t2. flows to During the above period, the charging voltage of the capacitor 7 is the initial charging voltage -
Vc ₁ becomes Vc ₁ due to resonance current i.

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 Vc ₁ of the capacitor 7 also remains at Vc ₁ 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 . During this period, the effective leakage inductance of the conversion transformer 5 also acts to determine the peak of the resonant current i. Further, the resonant current i is transmitted to the secondary side via the conversion transformer 5, and after being rectified and smoothed, is supplied to the load 10 as a predetermined output DC voltage.

The above is the circuit configuration and operation of a conventional series resonant DC-DC converter. Above series resonant DC
- Two methods have been proposed for controlling the DC converter: one is to change the capacitance value of capacitor 7, and the other is to change the period during which both switching elements 3 and 4 are in the OFF state, that is, to control the switching frequency. has been done. 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 perform control to stabilize the output DC voltage value.

Purpose of the Invention The purpose of the present invention is to provide a regulator that stabilizes the output DC voltage 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 present invention attempts to provide a voltage power supply device.

Composition of the Invention In order to achieve the above object, the constant voltage power supply device of the present invention includes a switching means that at least turns on and off with respect to an input DC power supply, and a parallel switching means that connects a capacitor in parallel to the input terminal of a conversion transformer. A series resonant circuit including a resonant circuit and an inductance is connected, and a rectifier circuit and a smoothing circuit are connected to the output terminal of the conversion transformer. The structure includes a control means for controlling the switching frequency as a function of the output DC voltage obtained from the smoothing circuit so as to be between the parallel resonance frequencies of the parallel resonance circuit, thereby making it possible to utilize resonance development. This is a constant voltage power supply device that can provide a stable output DC voltage over a wide range of input/output fluctuations.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described based on the drawings. FIG. 3 is a basic circuit configuration diagram of the first embodiment of the present invention, and parts having the same functions as those already explained in FIG. 1 are given the same reference numerals. Further, FIGS. 4a, b, c, and d are voltage/current waveform diagrams at various parts in FIG. 3.

In FIG. 3, reference numerals 13 and 14 indicate switching means constituted by a circuit in which switching elements 3 and 4 and unidirectional elements 11 and 12 are connected in series. 15 is inductance, 19 is capacitor 7
and a conversion transformer 16, the capacitor 7 and the primary winding 16a of the conversion transformer 16 are connected to the input terminals c and d of the parallel resonant circuit 19, and the output terminals e and f A secondary winding 16b of the conversion transformer 16 is connected to the secondary winding 16b of the conversion transformer 16.
In addition, the above inductance 15 and the parallel resonant circuit 1
9 are connected in series to form a series resonant circuit, and this series resonant circuit is connected to the switching means 1.
3 and 14 and between the midpoints of the input DC power supplies 1 and 2. Further, a rectifier circuit 8 and a smoothing capacitor 9 serving as a smoothing circuit are connected to output terminals e and f of the parallel resonant circuit 19, so as to supply an output DC voltage to a load 10. The output terminals g and h of this constant voltage power supply device are connected to a control circuit 17 composed of a reference voltage source, an error amplifier, an oscillation circuit, etc., and the output DC voltage between the output terminals g and h is It is compared with the voltage value of the reference voltage source,
The control circuit 17 uses an oscillator circuit to generate a signal that alternately turns on and off the switching elements 3 and 4 in the switching means 13 and 14 according to the difference, and after the signals are distributed by the distribution circuit, the signals are output to the switching means 13 and 14. do.

The constant voltage power supply device of this embodiment configured as described above will be described below with reference to the operating waveform diagram of FIG. 4. The operating waveform diagram in Fig. 4 is
In the figure, inductance 15 and parallel resonant circuit 1
Figure 4a shows the series resonant current i flowing between the capacitor 7 in the parallel resonant circuit 19 and the conversion transformer 1.
The parallel resonant current i _L flowing through the primary winding 16a of 6 is shown in FIG. 4b, and the charging voltage of the capacitor 7 is
Vc is shown in Fig. 4d, and the output current _i0 between the output terminals e and f of the parallel resonant circuit 19 is shown in Fig. 4c.
The horizontal axis is the time axis.

Since this embodiment also utilizes resonance development as described with reference to FIG. 1, explanations that overlap with those of the conventional example will be omitted. When the switching element 3 is turned on at time _t1 in FIG. and the impedance between the input terminals c and d of the parallel resonant circuit 19. The above current is the series resonance current i, and corresponds to the period from time t ₁ to time t ₃ in FIG. 4a.
The energy due to the series resonant current i increases the charging voltage Vc of the capacitor 7 of the parallel resonant circuit 19,
As from time t ₁ to time t ₃ in FIG. 4d, −
Increase from Vc ₁ to Vc ₃ .

Here, the input terminal c of the parallel resonant circuit 19,
The parallel resonant current i _L flowing in the parallel resonant circuit composed of the capacitor 7 and the primary winding 16a of the conversion transformer 16 connected in parallel between A current determined by the corresponding impedance and the charging voltage of the capacitor 7 flows as shown in FIG. 4b.

In this state, the time point when the charging voltage Vc of the capacitor 7 becomes higher than the value obtained by converting the value of the output DC voltage to the primary side of the conversion transformer 16, that is, corresponds to Vc ₂ in FIG. 4d. time t ₂
So, the energy of capacitor 7 is the parallel resonant circuit 1
The output current i0 is supplied from the output terminals e and f of 9 to the output terminals g and h of the constant voltage power supply device, and _the output current
i ₀ is a resonant current determined by the capacitor 7 of the parallel resonant circuit 19, the primary winding 16a of the conversion transformer 16, and the leakage inductance of the conversion transformer 16, and from time t ₂ to t ₄ in FIG. 4c. It flows like a waveform up to. Due to the development, the charging voltage Vc of the capacitor 7 decreases by supplying the output current i ₀ and further decreases due to the influence of the parallel resonance current i _L , and at time t ₁ '. is Vc ₁
becomes. The absolute values of the charging voltage Vc ₁ at time t ₁ ′ and the charging voltage −Vc ₁ at time t ₁ are exactly the same, and henceforth,
When the switching element 4 is turned on at time t ₁ ', a waveform whose polarity is opposite to that from time t ₁ to time t ₁ ' appears. Next, the time when switching element 3 turns on
The charging voltage at time t ₁ ′ becomes −Vc ₁ , which is exactly the same as that at time t 1.Hereafter, the waveform from time _{t 1 to} time t ₁ ″ will be repeated.

Here, the function of the unidirectional elements 11 _and 12 will be explained. Since the unidirectional elements 11 and 12 have the same function, the unidirectional element 11
I will only talk about. As described above, when the switching element 3 is turned on, energy is transferred to the capacitor 7 in the parallel resonant circuit 19 to the charging voltage.
This unidirectional element 11 is accumulated as Vc.
prevents this stored energy from returning to the input DC power supply 1. Therefore, if switching elements 3 and 4 are unidirectional elements, unidirectional elements 11 and 12 are not necessary.

Next, a limiting method for stabilizing the output DC voltage will be described. Output terminals g, h of constant voltage power supply
Energy is supplied to the conversion transformer 16 because the voltage of the primary winding 16a of the conversion transformer 16 (a voltage equal to the charging voltage Vc of the capacitor 7 in FIG. 3) converts the output DC voltage of the constant voltage power supply into the conversion transformer 16. 16
When the value is higher than the value converted to the primary side of This means that the voltage can be controlled.

A control method for realizing the above method will be specifically described below. The amount of energy stored in the capacitor 7 is determined by the impedance between the inductance 15 and the input terminals c and d of the parallel resonant circuit 19. The above impedance changes depending on the switching frequency, and when the switching frequency is lowered (higher), the above impedance becomes larger (smaller), and the parallel resonant circuit 1
The amount of energy supplied to 9 decreases (increases). In other words, the amount of the series resonant current i decreases (increases).
This means that the charging voltage Vc of the capacitor 7 also becomes lower (higher), and the energy transmitted to the output terminals g, h becomes less (more). As described above, the output DC voltage of the constant voltage power supply device can be controlled by the switching frequency,
It is possible to stabilize even input/output fluctuations.

To set such a state, the series resonant frequency of the series resonant circuit composed of the inductance 15 and the parallel resonant circuit 19, the capacitor 7 in the parallel resonant circuit 19, and the primary winding of the conversion transformer 16 must be adjusted. 16a and the switching elements 3 and 4 are alternately turned on and off.
This can be achieved by setting the relationship with the switching frequency to be turned off as shown below.

(Parallel Resonance Frequency) < (Switching Frequency) < (Series Resonance Frequency)... In this case, if the switching frequency is set outside the above range, resonance development will no longer occur and the characteristics of a constant voltage power supply using resonance development will be lost. It turns out.

Further, as a method for changing the switching frequency, a conventional frequency control method is sufficient, and the circuit for this is the control circuit 17.

Therefore, in the present invention, the impedance between the input terminals c and d of the parallel resonant circuit 19 can be controlled by changing the switching frequency. Furthermore, as can be seen from the operating waveform diagram in Figure 4, all the flowing currents are sinusoidal, making it possible to stabilize the output DC voltage without impairing any of the characteristics of the constant voltage power supply that uses resonance development. can.

Here, the inductance 15 is the series resonant current i
This is one factor that determines the peak value of , but it can be made sufficiently small as long as it is within the allowable range of the current capacity of the elements used in the actual circuit, and furthermore, it can be made zero.

Next, FIG. 5 shows a second embodiment of the present invention, and FIG. 6 shows its operating waveform diagram. In Figure 5, the first
Components having the same functions as those in the embodiment are given the same reference numerals, and in the explanation of operations, no particular explanation will be given for cases where the same operations are performed.

The difference in circuit configuration between the second embodiment and the first embodiment is the configuration of the switching means 22 and 23 in FIG. Therefore, only the switching means 22 and 23 will be described in the circuit configuration. The switching means 22, 23 are
Switching elements 3 and 4 and unidirectional elements 11 and 1
2 constitute a unidirectional switching means, and the unidirectional elements 20 and 21 are connected to the unidirectional element 1.
The switching elements 3 and 4 and the unidirectional element 1 are electrically connected in a direction opposite to the direction of conduction between the switching elements 3 and 12
It has a configuration in which it is connected in parallel to 1 and 12 series circuits. With this configuration, the switching means has a switching function in only one direction. The switching means 22, 2
3 is an example, and it is also possible to replace it with an element (for example, MOSFET) that enables the above operation. Here, the operation will be explained using a configuration such as the switching means 22 and 23 shown in FIG.

Next, the operation of the second embodiment will be explained.
The operating waveforms of each part in Figure 5 are shown in Figure 6 a, b, c, d.
This is an operation waveform diagram at the same location as in FIGS. 4a, b, c, and d.

Since the basic operation of this second embodiment is the same as that of the first embodiment, only the different parts will be described.
When the switching element 3 is turned on at time _t1 , a series resonant current i determined by the impedance between the inductance 15 and the input terminals c and d of the parallel resonant circuit 19 flows. This corresponds to the current waveform from time t ₁ to time t ₃ in FIG. 6, and is the same operation as the first embodiment. Due to the above DC resonance current i,
Charging voltage of capacitor 7 in parallel resonant circuit 19
Vc increases from −Vc ₁ . Here, at time _t3 when the series resonant current i finishes flowing, the charging voltage Vc of the capacitor 7 is equal to the Vc waveform of FIG. 6d.
Vc ₃ is higher than the input DC power supply 1, and the energy of the capacitor 7 in the energy storage means 19 is regenerated to the input DC power supply 1 as a regenerative current via the inductance 15 and the unidirectional element 20. This corresponds to the current waveform from time t ₃ to time t ₅ in Fig. 6a, and from time t ₁ to time t 5.
Since the series resonance current up to t ₃ and the flowing path are the same, the resonance frequency is the same and the waveform has the same period.

Next, when the switching element 4 is turned on at time t ₁ ', a waveform with the same absolute value and opposite polarity appears from time t ₁ to time t ₁ ', and the regenerative current flows through the unidirectional element 21 and the inductance 15. , are regenerated to the input DC power supply 2 via the parallel resonant circuit 19. Below is the time
The waveform from t ₁ to time t ₁ ″ is repeated.

As a control method, a method is used in which the energy in the parallel resonant circuit 19 is changed more greatly by utilizing the development, thereby controlling the energy transmitted to the output terminal of the constant voltage power supply device. Further, the amount of energy due to the regenerative current is determined by the value of the charging voltage Vc of the capacitor 7 in the parallel resonant circuit 19, and the charging voltage Vc
As explained in the first embodiment, changes depending on the switching frequency for alternately turning on and off the switching elements 3 and 4, so the amount of energy due to the regenerative current changes depending on the switching frequency.

In addition, the inductance 15 and the parallel resonant circuit 19
The series resonant frequency of the series resonant circuit constituted by the impedance between the input terminals c and d of Since the relationship between the frequency and the switching frequency is the same as the conditional expression of the first embodiment, the second embodiment can be performed using the completely same control method as the first embodiment, and the resonance development can be performed using the same control method as the first embodiment. The output DC voltage can be stabilized without impairing the characteristics of the constant voltage power supply used.

Further, in the first embodiment, it was described that the inductance 15 can be controlled regardless of the magnitude of the element value, but the same is true in the second embodiment.

Next, a third embodiment of the present invention realized with a different configuration from the first embodiment is shown in FIG. 7, and its operating waveform diagram is shown in FIG.
As shown in the figure. In FIGS. 7 and 8, parts having the same functions as those in FIGS. 3 and 4 of the first embodiment are given the same reference numerals.

In the third embodiment, the half-bridge configuration of the first embodiment is replaced with a configuration using a single switching element. In FIG. 7, an inductor 15, a parallel resonant circuit 19, and a switching means 24 are connected in series to an input DC power source 27, and the switching means 24 has a switching element 26 and a unidirectional element 25 connected in series. is connected and configured. Further, the control circuit 28 corresponds to the control circuit 17 of the first embodiment except for the oscillation frequency distributing circuit that was necessary for turning the switching elements 3 and 4 on and off alternately. They are exactly the same.

The operation of the third embodiment will be explained below with reference to FIG. 8, but parts that operate the same as those of the first embodiment will be omitted, and only the different parts will be described.

In the first embodiment, the DC resonant current i flowing through the series resonant circuit composed of the inductance 15 and the parallel resonant circuit 19 flows in both directions because there are two switching means, but in the third embodiment Since there is only one switching means, parallel resonant circuit 1
The current injected into 9 is only from one direction. Therefore, the waveform of the series oscillating current i in FIG. 4 showing the operating waveform of the first embodiment is different from that in FIG. 8 showing the operating waveform of the third embodiment. Furthermore, since the same principle is used for other operations and waveforms, the waveforms are also the same.

Therefore, the control method of the third embodiment can stabilize the output DC voltage between the output terminals g and h of the constant voltage power supply device in exactly the same manner as the first embodiment.

As described above, since the first embodiment of the present invention can be configured with one switching means, the third embodiment can perform resonance development using the completely same control method as the first embodiment. The output DC voltage can be stabilized without impairing the characteristics of the constant voltage power supply used.

Next, FIG. 9 shows a fourth embodiment in which the second embodiment of the present invention is realized with a different configuration, and its operation waveform diagram is shown in FIG.
Shown in Figure 0. In FIGS. 9 and 10, parts having the same functions as those in FIGS. 5 and 6 of the second embodiment are given the same reference numerals.

In the fourth embodiment, the half-bridge configuration of the second embodiment is replaced with a configuration using a single switching element. In FIG. 9, an inductance 15, a parallel resonant circuit 19, and a switching means 29 are connected in series to an input DC power source 27, and the switching means 29 has a switching element 26 and a unidirectional element 25 connected in series. A switching element 30 which is connected and conducts in a direction opposite to the conduction direction of the unidirectional element 25 is connected in parallel with the series circuit of the switching element 26 and the unidirectional element 25. Further, the control circuit 28 is similar to the control circuit 1 of the second embodiment.
7 except for the oscillation frequency distributing circuit that was necessary to alternately turn on and off the switching elements 3 and 4, and the rest are exactly the same.

The operation of the fourth embodiment will be described below with reference to FIG. 10, but parts that operate the same as those of the second embodiment will be omitted, and only the different parts will be described.

In the second embodiment, the series resonant current i flowing through the series resonant circuit composed of the inductance 15 and the parallel resonant circuit 19 and the regenerative current regenerated to the input DC power supply are bidirectional because there are two switching means. However, in the fourth embodiment, since there is only one switching means, the series resonant current and regenerative current to the parallel resonant circuit 19 flow only from one direction.
Therefore, the waveforms of the series resonant current i in FIG. 6 showing the operating waveforms of the second embodiment and FIG. 10 showing the fourth operating waveforms are different. Furthermore, since the same principle is used for other operations and waveforms, the waveforms are also the same.

Therefore, the control method of the fourth embodiment can stabilize the output DC voltage between the output terminals g and h of the constant voltage power supply device in exactly the same manner as the second embodiment.

As described above, since the second embodiment of the present invention can be configured with one switching means, the fourth embodiment can perform resonance development using the completely same control method as the second embodiment. The output DC voltage can be stabilized without impairing the characteristics of the constant voltage power supply used.

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 four switching means, for example. The output DC voltage can be stabilized using a control method.

In the present invention, a DC power source was used as the input power source, but
Needless to say, a highly variable DC voltage obtained by rectifying an AC power source can also be used as an input power source.

Effects of the Invention As is clear from the above description, the present invention configures a series resonant circuit of a constant voltage power supply using resonance development with an inductance and a parallel resonant circuit, and provides energy that can be stored in the parallel resonant circuit. By controlling the amount, the output DC voltage of a conventional constant voltage power supply device using resonance development can be stabilized even over a wide range of input/output fluctuations. Furthermore, the characteristics of low switching loss and low radiation noise of the conventional constant voltage power supply device described above are not impaired in any way.

[Brief explanation of the drawing]

Figures 1 and 2 are circuit configuration diagrams and operating waveform diagrams of a conventional constant voltage power supply using resonance development, and Figures 3 and 4 are circuit configuration diagrams of a first embodiment of the present invention. FIGS. 5 and 6 are circuit configuration diagrams and operation waveform diagrams of the second embodiment of the present invention, and FIGS. 7 and 8 show how the first embodiment can be implemented using only one switching means. FIGS. 9 and 10 are diagrams of the realized circuit configuration and its operating waveforms. FIGS. 9 and 10 are diagrams of the circuit configuration and its operating waveforms in which the second embodiment is realized using only one switching means. 1, 2, 27...Input DC power supply, 3, 4, 26
... Switching element, 5, 16 ... Conversion transformer, 5a, 16a ... Primary winding of conversion transformer, 5b, 16b ... Secondary winding of conversion transformer, 7 ... Capacitor, 8 ... Rectifier circuit , 9...
Smoothing capacitor, 10...Load, 11, 12,
20, 21, 25, 30...unidirectional element, 1
3, 14, 22, 23, 24, 29... Switching means, 15... Inductance, 17, 28
...Control circuit, 19...Parallel resonant circuit.

Claims (1)

[Scope of Claims] 1. Switching means that operates at least on and off with respect to an input DC power source, and a series resonant circuit consisting of an inductance and a parallel resonant circuit in which a capacitor is connected in parallel to the input terminal of a conversion transformer. and a rectifying circuit and a smoothing circuit are connected to the output terminal of the conversion transformer, and the switching frequency of the switching means is between the series resonant frequency of the series resonant circuit and the parallel resonant frequency of the parallel resonant circuit. 2. A constant voltage power supply device comprising: control means for controlling the switching frequency as a function of the output DC voltage obtained from the smoothing circuit. 2. The constant voltage power supply device according to claim 1, wherein the switching means is configured to be conductive in only one direction. 3. The switching means has a circuit configuration in which a unidirectional element is connected in parallel with a switching element that conducts in only one direction so as to conduct in a direction opposite to the direction of conduction of the switching element. The constant voltage power supply device according to item 1.