JPS5952628B2 - inverter circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inverter circuit that converts a DC voltage into a desired DC voltage, and in particular has a simple configuration so that the oscillation frequency of an oscillator constituting the inverter circuit can be easily determined and adjusted. It is.

Conventionally, an inverter circuit as shown in FIG. 1 has been proposed. In FIG. 1, 1a and 1b indicate a positive terminal and a negative terminal, respectively, which are connected to the positive and negative terminals of a DC power supply, and the positive terminals 1a are connected to the N-type transistors 2a and 3a, respectively, which constitute switching elements. An N-type transistor 2b is connected to the collector and the emitters of the transistors 2a and 3a respectively constitute a switching element.
and 3b, and the emitters of these transistors 2b and 3b are respectively connected to the negative terminal lb. Furthermore, the control coils 4a, 4b, 4c and 4d of the oscillation transformer 4, which is a saturable transformer, are connected to the transistor 2a.
, 2b, 3a and 3b. In this case, the winding direction of the control coils 4a and 4d is the same, and the winding direction of the control coils 4b and 4C is opposite to that of the control coils 4a and 4d. The connection point between the emitter of the transistor 3a and the collector of the transistor 3b is connected to the connection point between the emitter of the transistor 2a and the collector of the transistor 2b through a series circuit of the input coil 5a of the output transformer 5 and the primary coil 6a of the current feedback transformer 6. Connecting. Also, the feedback coil 5b of the output transformer 5
One end is connected to one end of a voltage feedback coil 8 provided in the oscillation transformer 4 via a resistor 7, and this feedback coil 5b
The other end is connected to the other end of the voltage feedback coil 8, and one end and the other end of the secondary coil 6b of the current feedback transformer 6 are connected to one end and the other end of the current feedback conoil 9 provided in the oscillation transformer 4. Connect each. Output coil 5 of this output transformer 5
The output signal obtained at C is supplied to DC voltage output terminals 11a and 11b via a rectifier circuit and a smoothing circuit 10. Further, 12 indicates a starting coil provided in the oscillation transformer 4. In the conventional inverter circuit as shown in FIG. 1, positive feedback is performed by a voltage feedback coil 8 and a current feedback coil 9, and the bases of each transistor 2a, 2b, 3a, and 3b are driven through an oscillation transformer 4. However, the oscillation transformer 4 eventually becomes saturated and cannot supply driving power to the bases of the transistors 2a, 2b, 3a, and 3b, and at this moment the voltages generated in the control coils 4a, 4b, 4C, and 4d are reversed. The pair of transistors 2a and 3b and the pair of transistors 2b and 3a alternately turn on and off to maintain oscillation, and this oscillation output is supplied to the rectifier circuit and smoothing circuit 10 via the output transformer 5. A desired DC voltage is obtained at the DC voltage output terminals 11a and 11b.

The oscillation frequency F of an oscillator constituting such a conventional inverter circuit.

It is.

Here, S is the cross-sectional area of the core of the oscillation transformer 4, Bm is the saturation magnetic flux density, and N is the control coils 4a, 4b, 4C, 4d.
(assuming that the number of turns of the control coil is all equal), VBE is the base-emitter voltage of the transistors 2a, 2b, 3a, and 3b. Therefore, this oscillation frequency F. are coils 4a14b, 4C, 4d of oscillation transformer 4
The number of turns of the oscillation transformer 4 becomes complicated, and the adjustment of the oscillation frequency of the oscillator becomes complicated. In view of these points, the present invention is designed to simplify the configuration of the oscillation transformer 4 of the oscillator in the above-mentioned inverter circuit, and to facilitate adjustment of the oscillation frequency of the oscillator.

Hereinafter, one embodiment of the inverter circuit of the present invention will be explained with reference to FIG.

In FIG. 2, parts corresponding to those in FIG. 1 are designated by the same reference numerals, and detailed explanation thereof will be omitted. In the example shown in FIG. 2, the connection point between the emitter of the transistor 3a and the collector of the transistor 3b is connected to the emitter of the transistor 2a and the collector of the transistor 2b through a series circuit of the input coil 5a of the output transformer 5 and the saturable inductance 13. one end and the other end of the saturable inductance 13 are connected to one end and the other end of the current feedback coil 9 provided in the oscillation transformer 4, respectively.

Furthermore, a non-saturated transformer is used as the oscillation transformer 4. The rest of the structure is the same as in FIG. Since the present invention is configured as described above, positive feedback is performed by the voltage feedback coil 8 and the current feedback coil 9, and the bases of the transistors 2a, 2b, 3a, and 3b are driven through the oscillation transformer 4. However, the saturable inductance 13 eventually becomes saturated, and at this time, the inductance value of the saturable inductance 13 becomes approximately zero, and no feedback current is supplied to the current feedback coil 9, and at this moment, the control coils 4a, 4b, 4C, and The voltage generated at 4d operates in reverse, and the pair of transistors 2a and 3b and the transistors 2b and
3a alternately turns on and off, oscillation is maintained, and this oscillation output is supplied to the rectifier circuit and smoothing circuit 10 via the output transformer 5, so that a desired DC voltage is obtained at the DC voltage output terminals 11a and 11b. It will be done.

The oscillation frequency f of the oscillator constituting the inverter circuit of the present invention is.

Here, N is the number of turns of the current feedback coil 9, and Nl3 is the number of turns of the saturable inductance 13. Therefore, in the present invention, the oscillation frequency of the oscillator constituting this inverter circuit can be determined by the number of turns Nl3 of the saturable inductance 13.

As described above, according to the present invention, the saturable inductance 1
Since the oscillation frequency of the oscillator constituting the inverter circuit can be determined by 3, the oscillation transformer 4 can have a simple configuration, a non-saturable transformer can be used, which makes it cheaper, and the saturable inductance 13
The oscillation frequency of this oscillator can be adjusted by adjusting the number of turns of the oscillator, making it easy to adjust the oscillation frequency. Furthermore, the saturation characteristics of the saturable inductance 13 improve the current waveforms fed back to the bases of the transistors 2a, 2b, 3a, and 3b, improving efficiency. Further, at the time of startup, a large amount of current feedback can be obtained due to the self-inductance of the saturable inductance 13, which has the advantage of facilitating startup. Further, FIGS. 3 and 4 respectively show other embodiments of the present invention.

In FIGS. 3 and 4, parts corresponding to those in FIGS. 1 and 2 are designated by the same reference numerals, and detailed explanation thereof will be omitted. In this figure 3, the saturable inductance 1 in figure 2
A primary coil 6a of a current feedback transformer 6 is provided in parallel with the current feedback transformer 3, and one end and the other end of the secondary coil 6b of the current feedback transformer 6 are connected to one end and the other end of the current feedback coil 9 provided in the oscillation transformer 4, respectively. It is connected at the end. In the example shown in Fig. 3, as in Fig. 2, when the saturable inductance 13 is saturated, the inductance value of the saturable inductance 13 becomes approximately zero, so current feedback is not performed at this time, and the operation is the same as in Fig. 2. That's easy to understand. Therefore, it goes without saying that FIG. 3 has the same effect as FIG. 2. In addition, in the example of FIG. 3, if the number of turns of the primary coil 6a'' of the current feedback transformer 6 is N5a, and the number of turns of the secondary coil 6b is N6b, the oscillation frequency f1 of the example of FIG. Coil 6 of feedback transformer 6
This oscillation frequency f1 can be finely adjusted by selecting the turns ratio of a and 6b.

Furthermore, FIG. 4 shows an oscillator having a half-bridge circuit configuration instead of the oscillator having the fribridge circuit configuration shown in FIG. 2, and it is easy to understand that this FIG. 4 also has the same effect as that shown in FIG. 2.

It goes without saying that the present invention is not limited to the above-described embodiments, and can take various other configurations without departing from the gist of the present invention.

[Brief explanation of the drawing]

Figure 1 is a connection diagram showing an example of a conventional inverter circuit, Figure 2 is a connection diagram showing an example of a conventional inverter circuit.
The figure is a connection diagram showing one embodiment of the inverter circuit of the invention, and FIGS. 3 and 4 are connection diagrams showing other embodiments of the invention, respectively. 1a, 1b are terminals to which DC power is supplied, 2a, 2b,
3a and 3b are transistors, 4 is an oscillation transformer,
5 is an output transformer, 8 is a voltage feedback coil, 9 is a current feedback coil, 10 is a rectifier circuit and a smoothing circuit, 11a and 11b are DC voltage output terminals, and 13 is a saturable inductance.

Claims (1)

[Claims] 1 The input DC voltage is supplied across the series circuit of the first and second switching elements constituting the oscillator, and the oscillation output signal of the oscillator is supplied to the input coil of the output transformer and the series circuit of the saturable inductance. The alternating voltage obtained from the output transformer is supplied to the control electrodes of the first and second switching elements through the voltage feedback coil of the oscillation transformer constituting the oscillator, and in parallel with the saturable inductance. A current feedback coil is connected to the oscillation transformer, and the current flowing to the input coil of the output transformer is connected to the first and second coils.
The first and second switching elements were alternately turned on and off to rectify and smooth the output signal obtained from the output coil of the output transformer to obtain a desired DC voltage. An inverter circuit characterized by: