JPS5928877A - Constant-voltage power source - Google Patents

Abstract

PURPOSE:To enable to obtain a stable output voltage for the variation in the input of a wide range with a simple structure by connecting a circuit of a diode connected in series with a coil in such a manner that a current flows from a resonance condenser toward an input DC power source. CONSTITUTION:A series connection circuit of a diode 20 and a resonance coil 22 and a series connection circuit of a diode 21 and a resonance coil 23 are connected so that a current can flow from a resonance condenser 5 directly toward DC power sources 1, 2. The initially charging voltage of the condenser 5 is controlled by the diode 20, the coil 22 or the diode 21 and the coil 23 connected in series, thereby stabilizing the output. In this manner, a constant-voltage power which has controlling function of wide range with simple structure can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application 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.

Conventional Structures and Problems The most popular conventional constant voltage power supply is a switching regulator that uses a pulse width control method for the on/off operation of a switching element. This switching regulator has high efficiency and is useful for making equipment smaller and lighter. However, because there is a switching time, which is a time during which the voltage and current change sharply, switching loss occurs. It has disadvantages such as large noise, large unnecessary radiation noise, and large conduction noise. Therefore, the scope of use of switching regulators is limited, especially when trying to use them as power sources for audio equipment.
Noise countermeasures must be taken, such as inserting a filter with a large amount of noise attenuation into the input/output section, or applying a completely sealed shield, resulting in problems such as increased costs and decreased reliability.

One solution to this problem, as shown in Figure 1, is to connect a converter, transformer, and capacitor in series, and turn the switches on and off alternately to generate a predetermined output energy through the zimverter transformer. A series resonant DI-DC converter has been proposed that obtains the following. To explain this, in Fig. 1, 1 and 2 are DC power supplies, 3 and 4 are switching elements (for example, transistors, silices, etc.), 6 is a resonance capacitor, and 7 is a converter transformer with leakage inductance Ll. The primary winding 9 is connected in series with the resonance capacitor 5 described above. 8 is a secondary winding of a converter transformer 9, the output of which is rectified by a rectifier circuit 1o and smoothed by an electrolytic capacitor 11 for normal lh. 12 is an electrical load to which the DC output voltage is supplied. The switching elements 3 and 4 are alternately switched by a control circuit 13.
When switch element 3 is on and switch element 4 is off, a sinusoidal current flows in the loop of DC power supply 1 → 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 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 morain inductance Ll of the converter/transformer 9.
− becomes. The operating waveforms are shown in FIG. In FIG. 2, (a) shows the switch element 3, and (b) shows the switch element 4.
(C) shows a corresponding current waveform. As is clear from Fig. 2, when the switching elements 3 and 4 are switched, the current becomes zero, so the switching loss is significantly reduced, resulting in not only high efficiency but also a reduction in unnecessary radiation noise and conduction noise. can be achieved.

However, in the series resonant DC-DC converter shown in Figure 1, it is difficult to stabilize the output against large changes in input and load, and a major problem remains as to how to stably control the output voltage. was.

OBJECTS OF THE INVENTION The present invention aims to provide a constant voltage power supply device that is easy to control and has a wide range of control functions in such a series resonant DC-DC converter.

[Configuration of the Invention] In order to achieve the object 2-1], the present invention provides at least a switching element that performs on/off operations with respect to an input DC power supply, a resonant capacitor, and a primary winding of a first conversion transformer. a series resonant DC-DC converter configured to connect a series connection circuit including a diode, connect an electrical load to a secondary winding of a first conversion transformer, and supply a DC voltage; and a coil connected in series are connected so that current flows from the resonance capacitor toward the input DC power source.

Description of examples FIG. 3 shows a circuit configuration diagram of an 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. 1 is that the diode 20 and the resonant coil 22
The series connection circuit between the diode 21 and the resonant coil 23 is connected in such a way that a current can flow directly from the resonant capacitor 5 toward the DC power supply 1°2. .

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 flows through primary winding 7 of converter transformer 9.
is expressed by the following equation.

0≦t≦π! [q Ec: Voltage value of DC power supply 1 or 2 o: Output voltage converted to the primary side vo: Initial charging voltage value of resonance capacitors R6:
The SF average value of the resonant current shown by the two people in "Equivalent series loss resistance" in Figure 1 is the current transmitted to the secondary side through the converter transformer 9 with an appropriate primary-secondary winding ratio, that is, the load It becomes an electric current. (Ec
By controlling the initial charging voltage value ■c of the resonance capacitor 6, the resonance current '+(t) is controlled, and as a result, the load current is controlled.

The present invention is an application of this principle, and the initial charging voltage value of the capacitor 6 is set to a resonance value by a diode 20 and a resonance coil 22 connected in series, or by a diode 21 and a resonance coil 23 connected in series. The purpose is to return the electric charge of the resonant capacitor 5 to the DC power supplies 1 and 2, control the initial charging voltage value of the resonant capacitor 5, and stabilize the output.

Now, let's talk about the operation of the embodiment of the present invention shown in FIG.
This will be explained with reference to the waveform diagram in the figure.

In FIG. 4, (a) shows a timing chart of switch element 3, (b) shows a timing chart of switch element 4, and (C) shows a timing chart of switch element 4.
i + (t) is the current flowing to the primary winding 7 of the converter transformer 90, i 2 (t) is the feedback current flowing to the diode 20 or diode 21, and ■op(t
) indicates the voltage across the resonance capacitor 6. In FIG. 3, the initial charging voltage value of the resonance capacitor 5 at time t1 is ~vop2. Time t 1 color t 4 (7
), switch element 3 is on and switch element 4 is on, then the positive side of DC power supply 1 → switch-i element 3 →
Resonant current i flows through the loop of primary winding 7 of converter transformer 9 → resonant capacitor 6 → negative side of DC power supply 1
+ (t) flows.

The voltage vcp(t) across the resonance capacitor 5 rises due to the resonance current i+(t), and reaches V at time t4. It becomes pl.

When the value of vopl becomes larger than that of the DC power source 1, a feedback current 12(t) flows in the loop of the resonant capacitor 5→resonant coil 22→diode 2o→DC power source 1. As a result, the initial charging voltage value of the resonance capacitor is V. pl to V. It changes to p2.

If the switch element 3 is off and the switch element 4 is on at time js, the resonant current i,(t) changes the initial charging voltage value to V. It starts flowing as p2.

When repeating the above operation, switch element 3.40
By changing the periodic sound, the initial charging voltage value V of the resonance capacitor 6 can be determined. Not only p(t4) can be changed, but also the average current of the resonant current i j (t), that is, the output current can be changed. In other words, the output can be controlled.

From the second point, when the output increases, the period T is lengthened.
When the output decreases, by shortening the period T, IJ
” It is possible to control the force at a constant level.

In addition, in the embodiment of the present invention, which is a double series DO-D with a half-bridge configuration having two switch elements,
Although the description has been made regarding the C converter, it goes without saying that a similar effect can be expected in a series co-installed DO-DC converter having a full bridge configuration having four switching elements.

Furthermore, in the embodiment of the present invention described above, the converter
Although the leakage inductance Lβ of the transformer 9 is used as a resonance coil, it is also possible to connect a resonance coil in series with the resonance capacitor 5.

Effects of the Invention As described above, the present invention provides a constant voltage power supply device 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 with a simple configuration. It is possible to realize this, and its industrial value is significant.

[Brief explanation of drawings]

Figure 1 is a basic circuit diagram of a series resonant DC-DC converter, and Figures 2 (a), (b), and (c) are the basic circuit diagram of a series resonant DC-DC converter.
FIG. 3 is a circuit configuration diagram of an embodiment of the present invention, and FIG. 4 (a), (b), (C
) is an operation waveform diagram of each part in FIG. 3. 1.2...DC power supply, 3,4...Switch element, 6...Resonance capacitor, 7...
...Primary winding, 8...Secondary -1,9...
・Converter transformer, 10 rectifier circuit, 11...
... Electrolytic capacitor, 12 ... Electrical load, 13
...Control circuit, 20, 21...Diode, 22.23...Resonance coil. 1st Figure 1jAz diagram Figure 4 direction

Claims (1)

[Claims] A series connection circuit including at least a switching element for on/off operation, a resonant capacitor, and a primary winding of a first conversion transformer is connected to an input DC power supply,
A series oscillator DC-type configured to connect an electrical load to the secondary winding of the first conversion transformer to supply a DC voltage.
A constant voltage power supply device comprising a DC converter and a circuit in which a diode and a coil are connected in series so that current flows from the resonance capacitor toward the input DC power supply.