JPS6236465B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a constant voltage power supply device using a new series resonant DC-DC converter capable of obtaining a stabilized DC output voltage. The most popular conventional constant voltage power supply device is a switching regulator that uses a pulse width control method for on/off operation of a switching element. This switching regulator is highly efficient and is useful for making equipment smaller and lighter.However, in principle, there is a period of time during which the voltage or current changes abruptly, that is, switching time. It has disadvantages such as large switching loss, large unnecessary radiation noise, and large conduction noise. For this reason, the scope of use of switching regulators is limited, and when trying to use them as power sources for audio equipment, it is necessary to insert filters with a large amount of noise attenuation into the input and output sections, or to apply completely sealed shields. Noise countermeasures must be taken, leading to problems such as increased costs and decreased reliability. As one solution to this problem, as shown in Figure 1, a converter transformer and a capacitor are connected in series, and by alternately turning on and off switches, a predetermined output energy is generated through the converter transformer. Series resonant type to obtain
A DC-DC converter has been proposed. To explain this, in Fig. 1, 1 and 2 are DC power supplies,
3 and 4 are switch elements (for example, transistors, thyristors, etc.), 5 is a resonance capacitor, and 7
The primary winding of the converter transformer 9 has a leakage inductance L _l and is connected in series with the resonance capacitor 5 . 8 is the secondary winding of the converter transformer 9, and its output is sent to the rectifier circuit 10.
and smoothed by a smoothing electrolytic capacitor 11. 12 is an electrical load to which the DC output voltage is supplied. Switch elements 3 and 4 are designed to switch alternately, and when switch element 3 is on and switch element 4 is off, DC power supply 1→
A sinusoidal current flows in the loop of switch element 3 → primary winding 7 of converter transformer 9 → resonance capacitor 5 → DC power supply 1. On the other hand, when switch element 3 is off and switch element 4 is on, a sinusoidal current flows through the loop of DC power supply 2 → resonance capacitor 5 → primary winding 7 of converter transformer 9 → switch element 4 → DC power supply 2. flows. The period is determined by the capacitance _C5 of the resonance capacitor 6 and the leakage inductance L of the converter transformer 9.
It becomes 2π√ _{5 l} determined by _l . The operating waveforms are shown in FIG. In Fig. 2, a is the switch element 3.
, b shows the timing chart of the switch element 4, and c shows the corresponding current waveform. As is clear from FIG. 2, the switch element 3,
At the time of switching 4, the current becomes zero, so the switching loss is significantly reduced, and not only high efficiency is achieved, but also unnecessary radiation noise and conduction noise can be reduced. However, a series resonant DC as shown in Figure 1
In DC converters, it is difficult to stabilize the output in response to large changes in input and load, and how to stably control the output voltage remains a major problem. The present invention aims to provide a constant voltage power supply device for such a series resonant DC-DC converter that is easy to control and has a wide range of control functions. FIG. 3 shows a circuit configuration diagram of the first embodiment of the present invention. In FIG. 3, parts having the same functions as those in FIG. 1 are given the same reference numerals. The difference between the circuit in FIG. 3 and the circuit in FIG. A rectifier 16 composed of bridge diodes is connected to both ends of the winding 15, and the anode side of the rectifier 16 is connected to the DC power supply 1.
Connect the cathode side of the rectifier 16 to the negative side of the DC power supply 2, and connect the intermediate tap of the secondary winding 15 of the control transformer 14 to the connection point of the DC power supplies 1 and 2 connected in series. It was connected. In addition, 17 is a control circuit, an error amplification circuit,
It is composed of an oscillation circuit, a distribution circuit, a drive circuit, etc., and turns the switch elements 3 and 4 on and off alternately at appropriate intervals. Before explaining the operation of this embodiment of the present invention, the control principle of a series resonant DC-DC converter will first be explained with reference to FIG. In FIG. 1, when switch element 3 or 4 is on and switch element 4 or 3 is off, a sinusoidal current i flowing through primary winding 7 of converter transformer 9 is expressed by the following equation. Otπ√ _{5 l} , α=R _S /2L _l ,

[Formula] E _c : Voltage value of DC power supply 1 or 2 V _O : Output voltage converted to the primary side V _c : Initial charging voltage value of resonance capacitor 5 R _S : Equivalent series loss resistance in Fig. 1 The average value of the resonant current shown by the formula becomes the current transmitted to the secondary side via the converter transformer 9 with an appropriate primary-secondary winding ratio, that is, the load current. (E _c −V _O ) = From V _c , by controlling the initial charging voltage value V _c of the resonance capacitor 5, the resonance current i ₁ (t) is controlled, and as a result, the load current is controlled. . The present invention applies this principle, and includes a control converter/transformer 1 in which the initial charging voltage value of the resonance capacitor 5 is added in parallel to the resonance capacitor 5.
4 to stabilize the output DC voltage. Now, the operation of the embodiment of the present invention shown in FIG. 3 will be explained with reference to the waveform diagram in FIG. 4. In FIG. 4, a shows the timing chart of the switch element 3, b shows the timing chart of the switch element 4, and i ₁ of c shows the timing chart of the switch element 4.
(t) is the current flowing in the primary winding 7 of the converter transformer 9, i ₂ (t) is the current flowing in the primary winding 13 of the control converter transformer 14, and V _cP (t) is the resonance current. The voltage across capacitor 5 is shown. In FIG. 3, at time t= _t1 , the initial charging voltage value of the resonance capacitor 5 is set to -V _cP3 . Between time t ₁ and t ₄ , switch element 3 is on and switch element 4 is off, then the positive side of DC power supply 1 → switch element 3 → 1 of converter transformer 9
A resonant current i ₁ (t) flows in a loop from the next winding 7 to the resonant capacitor 5 to the negative side of the DC power supply 1. Primary winding 1 of control converter transformer 14
The current i ₂ (t) flowing through the control converter transformer 14 becomes an exciting current for the control converter transformer 14 during t ₁ t≓t ₂ .
The voltage V _cP (t) across the resonant capacitor 5 increases due to the resonant current i ₁ (t) and the above excitation current i ₂ (t), and the secondary winding of the control converter transformer 14 increases accordingly. 15 also rises, and at time _t2 , when it becomes equal to or higher than (output voltage + forward drop voltage of rectifier 16), rectifier 16 is turned on, and DC power supply 1
Or current flows towards 2. As this current flows, the direction of the current flowing through the primary winding 13 of the control converter transformer 14 is reversed, that is, the charge in the resonance capacitor 5 starts discharging. The period of this discharge current i ₂ (t) is determined by the capacitance C ₅ of the resonance capacitor 5 and the leakage inductance L _l2 of the control converter transformer 14, and has a value of approximately π√ _{5 l2} . Next, at t ₂ tt ₃ , a resonance current i ₁ (t) flows into the resonance capacitor 5, and at the same time a discharge current i ₂ (t) flows out via the control converter transformer 14. In this period, |i ₁ (t)|>
Since |i ₂ (t)|, the voltage of the resonance capacitor 5 increases, and when |i ₁ (t)|=|i ₂ (t)|, that is, when t=t ₃ , the voltage of the resonance capacitor 5 increases to the maximum value V _cP1 have. Next, in the period t ₃ tt ₅ |i ₁ (t) |
<|i ₂ (t)|, so the resonance capacitor 5
The voltage begins to drop below V _cP1 . Furthermore, during the period t ₅ tt ₆ , the voltage of the resonance capacitor 5 further decreases due to the exciting current component i ₂ (t) of the control converter transformer 14.
At time _t6 , it becomes V _cP2 . At time _t6 , the switch element 4 sets V _cP2 as the initial charging voltage value of the resonance capacitor 5, and the resonance current i ₁ (t) shown by the above equation starts to flow. When repeating the above operation, by changing the period T of the switch elements 3 and 4, the initial charging voltage value V _cP2 of the resonance capacitor 5 can be changed, as is clear from the above operation description. That is, by changing the period T of the switch elements 3 and 4, it becomes possible to change the resonance current i ₁ (t) shown by the above equation, and the output can be controlled. From the above, the output can be controlled by lengthening the period T when the output increases and by shortening the period T when the output decreases. A second embodiment of the invention is shown in FIG. In FIG. 5, parts having the same functions as those explained in FIG. 3 are given the same reference numerals. FIG. 5 shows switch elements 3 and 4 in parallel with switch elements 3 and 4.
diodes 18 and 19 are added that allow current to flow in the opposite direction to the direction of current flowing therein. The circuit of FIG. 5 connects the DC power source 1 through the diode ₁₈ or 19 during t ₂ tt ₅ in FIG. Alternatively, by flowing a feedback current i ₃ (t) to the resonant capacitor 2, the voltage V _cP of the resonant capacitor 5 is greatly changed. In other words, in the embodiment shown in FIG.
However, in the embodiment shown in FIG. 5, in addition to _{i 2 (} t), the feedback current i ₃
(t) is added. Therefore, the embodiment of FIG. 5 has the advantage that the range of change in the period T required for control is smaller than that of the embodiment of FIG. 3. 6a, b, and c show the operating waveforms of FIG. 5. The details of the operating waveforms in FIG. 5 are clear from the above description, and therefore will not be described here. A third embodiment of the invention is shown in FIG. Also in FIG. 7, parts having the same functions as those explained in FIG. 3 are given the same reference numerals. In FIG. 5, the feedback current i ₃ (t) returns to the DC power supply 1 or 2 via the primary winding 7 of the converter transformer 9, but in FIG. Feedback current directly from resonance capacitor 5 to DC power supply 1 or 2 without going through the next winding
This is intended to cause i ₃ (t) to flow. For this purpose, a series connection circuit of the diode 20 and the resonance coil 22 and a series connection circuit of the diode 21 and the resonance coil 23 are connected so that current flows directly from the resonance capacitor 5 toward the DC power supplies 1 and 2. Connect as you like. With this configuration, the feedback current i ₃ (t) can be directly returned to the DC power supply 1 or 2 from the resonance capacitor 5.
Furthermore, in Fig. 5, the period of the feedback current i ₃ (t) is the same as that of the resonant current i ₁ (t), but in Fig. 7, by changing the inductance value of the resonance coil 22 or 23, Current i ₃ (t)
The period of can be changed as necessary. Further, in the first, second and third embodiments described above, the intermediate tap of the secondary winding 15 of the control converter transformer 14 is not connected to the connection point of the DC power supplies 1 and 2, but is left open, and the rectifier 16 is left open. the anode to the positive side of the DC power source 1 or 2, and the rectifier 16
It is clear that a similar effect can be expected even if the cathode of is connected to the negative side of the DC power supply 1 or 2. In addition, in the embodiment of the present invention described above, a series resonant DC-DC converter with a half-bridge configuration having two switch elements was shown, but a series resonant DC-DC converter with a full bridge configuration having four switch elements has been described. It goes without saying that similar effects can be expected in converters as well. Furthermore, in the embodiment of the present invention described above, the leakage inductance L _l of the converter transformer 9 is used as a resonant coil, but it is also possible to connect a resonant coil in series with the resonant capacitor 5. be. As described above, according to the present invention, a constant voltage power supply device can be realized with a simple configuration that can stabilize the output voltage over a wide range of input/output fluctuations while taking advantage of the features of a series resonant DC-DC converter. Its industrial value is remarkable.

[Brief explanation of the drawing]

Figure 1 is a basic circuit configuration diagram of a series resonant DC-DC converter, Figure 2 a, b, and c are operational waveform diagrams of each part in Figure 1, and Figure 3 is a diagram of the first embodiment of the present invention. The circuit configuration diagram, Figures 4a, b, and c are operation waveform diagrams of each part in Figure 3.
6a, b, and c are the circuit configuration diagrams of the embodiments of
The operation waveform diagram of each part in the figure, and FIG. 7 is a circuit configuration diagram of a third embodiment of the present invention. 1, 2...DC power supply, 3, 4...Switch element, 5
... Resonance capacitor, 7... Primary winding, 8... Secondary winding, 9... Converter transformer, 10... Rectifier circuit, 11... Electrolytic capacitor, 12... Electrical load,
13... Primary winding, 14... Control converter transformer, 15... Secondary winding, 16... Rectifier, 17... Control circuit, 18, 19, 20, 21... Diode, 2
2, 23... Resonance coil.

Claims (1)

[Claims] 1. A series connection circuit including at least a switch element for on/off operation, a resonant capacitor, and a primary winding of a first conversion transformer is connected to an input DC power source, and A rectifier/smoothing circuit is connected to the secondary winding of the conversion transformer No. 1, and an electrical load is connected to the output side of the converter to supply a DC voltage. The primary winding of another second conversion transformer is connected in parallel with the resonance capacitor, and the second
A constant voltage power supply device, characterized in that a secondary winding of a conversion transformer is connected to the input DC power supply via a rectifier circuit. 2. A constant voltage power supply device as set forth in claim 1, characterized in that a diode is connected in parallel with the switch element so as to conduct in a direction opposite to the conduction direction of the switch element. 3. A constant voltage power supply device as set forth in claim 1, characterized in that a circuit in which a diode and a coil are connected in series is connected so that current flows from a resonant capacitor toward an input DC power source. .