JPS624948B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inverter circuit that converts DC voltage to a desired DC voltage, and in particular, common parts and cost reduction when changing transistors due to changes in destination or output power, etc. It was designed to do this.

Conventionally, an inverter circuit as shown in FIG. 1 has been proposed. 1a and 1 in Figure 1
b indicates a positive terminal and a negative terminal connected to the positive and negative terminals of the DC power source, respectively, and the positive terminal 1a is connected to an NPN transistor 2 constituting a switching element.
an npn transistor 2b which is connected to the respective collectors of transistors 2a and 3a and whose respective emitters constitute switching elements;
and 3b, and the emitters of these transistors 2b and 3b are respectively connected to the negative terminal 1b. Control coils 4a, 4b, 4c and 4d of the oscillation transformer 4, which is a saturable transformer, are connected to transistors 2a, 2b, 3a and 3b.
are connected between the base and emitter of each. In this case, the winding directions of the control coils 4a and 4d are the same, and the control coils 4b and 4c are connected to the control coil 4.
The winding direction is opposite to that of a 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, one end of the feedback coil 5b of the output transformer 5 is connected to one end of the voltage feedback coil 8 provided in the oscillation transformer 4 via a resistor 7, and this feedback coil 5
Connect the other end of b to the other end of the voltage feedback coil 8,
Further, 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. The output signal obtained from the output coil 5c of the output transformer 5 is supplied to DC voltage output terminals 11a and 11b via a rectifier circuit and a smoothing circuit 10. Further, reference numeral 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 reverse. 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 the oscillator constituting such a conventional inverter circuit is f=V _BE /4×S×Bm×N (1). 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 coil 4.
The number of turns of a, 4b, 4c and 4d (in this case, the number of turns of the control coil is all equal), and V _BE is the base of transistors 2a, 2b, 3a and 3b.
It is the voltage between emitters.

By the way, in the case of a conventional inverter circuit having such a configuration, if the destination is changed, for example from Japan to Europe, the power supply voltage will be different, so the V _BE of the transistors 2a, 2b, 3a, 3b will change, or The oscillation frequency f of the oscillator changes as a result of changing the transistors as the output power changes, and the oscillation transformer 4, which has a complicated structure, has to be redesigned each time.

In view of these points, the present invention provides a versatile inverter circuit in which the oscillator components are common in the above-mentioned inverter circuit, and costs are reduced.

Embodiments of the inverter circuit of the present invention will be described below with reference to FIGS. 2 and 3. In FIGS. 2 and 3, parts corresponding to those in FIG. 1 are designated by the same reference numerals, and detailed explanation thereof will be omitted.

FIG. 2 shows an embodiment of the inverter circuit of the present invention. In the example of FIG. 2, the saturable type oscillation transformer 4 of FIG.
A drive transformer 13 for driving transistors 2a, 3a, and 3c is provided, and drive coils 13a, 13b, 13c, and 13d are provided in this drive transformer 13 corresponding to transistors 2a, 2b, 3a, and 3c, respectively, and a voltage feedback coil 14 is provided. and a current feedback coil 15, and the drive coils 13a, 13b, 13c and 13d are connected to the feedback coils 14 and 15 in the same manner as the control coils 4a, 4b, 4c and 4d and the feedback coils 8 and 9 in FIG. Connect to. Further, the current feedback transformer 6 in FIG. 1 is replaced with a saturable current feedback transformer/oscillation transformer 16, and its primary coil 16a
and the secondary coil 16b are connected in the same manner as the primary coil 6a and secondary coil 6b of the current feedback transformer 6 in FIG. 1, respectively. 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 14 and the current feedback coil 15, and the bases of the transistors 2a, 2b, 3a, and 3b are driven through the drive transformer 13. However, eventually the oscillation transformer 16
is saturated, and at this time, the inductance value of the oscillation transformer 16 becomes approximately zero, and no feedback current is supplied to the current feedback coil 15, and at this moment, the voltages generated in the drive coils 13a, 13b, 13c, and 13d are reversed. Similarly to FIG. 1, the pair of transistors 2a and 3b and the transistors 2b and 3a are connected.
The oscillation output is supplied to the rectifier circuit and smoothing circuit 10 via the output transformer 5, and the desired DC voltage is obtained at the DC voltage output terminals 11a and 11b. . The oscillation frequency f of the oscillator constituting the inverter circuit of the present invention is f=V _BE /4×S ₁ ×Bm ₁ ×N ₁₅ /N ₁₆ b×N
₁₃ ......(2). Here, S ₁ is the cross-sectional area of the core of the oscillation transformer 16, Bm ₁ is its saturation magnetic flux density, and N ₁₃ is the number of turns of the drive coils 13a, 13b, 13c, and 13d.In this case, the number of turns of the drive coils is all equal.) , N ₁₅ is the number of turns of the current feedback coil 15,
N ₁₆ b is the number of turns of the secondary coil 16b of the oscillation transformer 16. The oscillation transformer 16, which also serves as a current feedback transformer, sets a current feedback ratio, and the base feedback current I _bf is expressed by the following equation.

I _bf =N ₁₅ ×N ₁₆ a/N ₁₃ ×N ₁₆ bI _T ………(
3) Here, N ₁₆ a is the primary coil 1 of the oscillation transformer 16.
The number of turns of 6a and I _T are the currents flowing through the input coil 5a of the output transformer 5. Furthermore, the following equation must be satisfied as a condition for the oscillator to oscillate.

I _T /I _bf > h _fe ………(4) Here, h _fe is the transistor 2a, 2b, 3a,
3b is the current amplification factor.

Therefore, by designing the oscillation transformer 16 according to the V _BE and h _fe of the transistors used from equations (2), (3), and (4), the inverter circuit of the present invention can be made compatible with various transistors. be able to.

As is clear from the above description, according to the present invention, the oscillation frequency of the oscillator constituting the inverter circuit can be determined by the saturable oscillation transformer 16, which has a simple structure. can be used by changing the transistor without having to redesign each time, and the drive transformer 13 can be made of an unsaturated type to make it inexpensive. Oscillation transformer 1 with even simpler structure
By changing the design of only 6, it is possible to adapt to various transistors, so it is possible to easily cope with changes in destination, output power, etc., and thus a versatile inverter circuit can be obtained.

FIG. 3 shows another embodiment of the inverter circuit of the present invention, in which the oscillator with the full bridge circuit configuration of FIG. 2 is replaced with a half bridge circuit configuration.
It is easy to understand that FIG. 3 has the same effect as FIG. 2.

[Brief explanation of the drawing]

FIG. 1 is a connection diagram showing an example of a conventional inverter circuit, FIG. 2 is a connection diagram showing an embodiment of the present invention,
FIG. 3 is a connection diagram showing another embodiment of the present invention. 1a and 1b are terminals to which DC power is supplied, 2
a, 2b and 3a, 3b are transistors, 5 is an output transformer, 10 is a rectifier circuit and a smoothing circuit, 1
1a and 11b are DC voltage output terminals, 13 is a drive transformer, 14 is a voltage feedback coil, 15 is a current feedback coil, and 16 is a current feedback transformer/oscillation transformer.

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 to the input coil of the saturable oscillation transformer. 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 unsaturated drive transformer constituting the oscillator. At the same time, a current feedback coil is provided in the drive transformer connected in parallel with the secondary coil of the oscillation transformer, and the current flowing through the input coil of the output transformer is connected to the control electrodes of the first and second switching elements. The inverter circuit is configured to take out a DC voltage by rectifying and smoothing the output signal obtained by the output coil of the output transformer by alternately turning on and off the first and second switching elements.