JPS59201682A - Inverter - Google Patents

Abstract

PURPOSE:To enable to balance currents at both normal and transient times and to simplify the structure by connecting balance transformers to both ends of a load and taking a current balance. CONSTITUTION:The connecting point of transistors 1a, 3a is connected to the starting end of a coil C11a of a balance transformer BL11, the connecting point of transistors 1b, 3b is connected to the finishing end of a coil C11b, and the winding end of the coil C11a and the winding starting end of the coil C11b are connected to one end of a load L. The connecting point of transistors 2a, 4a is connected to the starting end of the coil C12 of a balance transformer BL12, the connecting point of transistors 2b, 4b is connected to the finishing end of the coil C12b, and the winding end and starting end of the coils C12a, C12b are connected to the other end of the load L. The currents of the transistors la, 1b- 4a, 4b driven in parallel are balanced by the transformers BL11, BL12.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inverter using a plurality of switching elements connected in parallel.

High-frequency, high-power inverters often use multiple small-capacity, high-frequency transistors connected in parallel, but in this case, balancing the current of each transistor during high-speed switching is an extremely important issue. Become.

Conventionally, as a method of balancing this current, as shown in Fig. 1, a balancing reactor Lr is inserted into the collector circuit of each transistor, and this balances the current during a transient period, or an emitter circuit of each transistor is used. A known method is to insert a resistor into each of the two, thereby balancing the current during steady state. In FIG. 1, the symbol E is a DC power supply, the symbol E is a load, and the symbol E is a flywheeling diode. However, these methods have the disadvantage that power loss due to the balance reactor Lr or resistance is large, and therefore the inverter efficiency is significantly reduced. By the way, in the circuit shown in Figure 1, if the current of each transistor is 5OA, the inductance of balance reactor/I/I, r is 54H, and the output frequency of the inverter is 20Kuz, the total loss due to all balance reactors Lr is Become. Also, if a resistor is inserted into the emitter circuit of each transistor and a voltage drop of 0.2V is generated by each resistor, the total loss due to all resistors is 50(A)Xo, 2(lX0.5X8= 40 (W). Note that rO and J in the above equation mean a duty ratio of 50 degrees.

Further, a circuit shown in FIG. 2 is conventionally known as a circuit that can maintain current balance during steady state and current balance during transient state. The circuit shown in this figure includes transistors la driven in parallel.

Balance transformers BL and -BL4 are respectively extended to the collector circuits 1b to 4a and 4'b.

Note that the dots in the figure indicate the beginning of winding of each coil. In the circuit shown in this figure, if the collector currents M and 1B of the transistors la and lb (see Figure 3 (a)) are the same, a voltage will be generated across each coil of the balance transformer BL1. Many.

However, if, for example, TA) TB occurs, voltages in the directions shown in FIG.
Furthermore, when TA is greater than TA, a voltage in the opposite direction to that shown in the figure is generated in each coil to compensate for the difference in currents Em and TB.

As a result, the currents M and IB are always the same during transient and steady states, respectively.

By the way, the circuit shown in FIG. 2 has the following problems. That is, the cutoff times of transistors la and lb usually vary on the order of μS. Now, for example, as shown in FIG. 3(b), the transistor 1a
When the transistor 1b shifts to the cut-off state and, on the other hand, the transistor 1b is still in the on state, the current d begins to decrease. When the current Th decreases, the torque current TB also decreases due to the action of the balance transformer BL%. On the other hand,
Since the load\L current Th tries to maintain the same current, the electric current I&
The decrease in Th+rB flows through diode p, so diode D becomes conductive, and the potential at point P1 shown in the figure becomes equal to the potential at the negative voltage terminal of DC power supply E. Here, if the transistor 1b is still in the on state, the voltage EB across the coil C2 of the balance transformer BL
is equal to the power supply voltage Ev, and therefore Coi, 11/
The voltage Em across Q is +im E v and in the direction shown in the figure, and as a result, a voltage 2 Ev is applied between the emitter and collector of the transistor 1a. Next, transistor 1b is cut off, so that both currents M and Y become 0, and all load current IL is transferred to diode D.
, and also the transistor la.

The emitter-collector voltages of lb are both XV.

Incidentally, even when there are variations in the on-time of the transistors i'a and tb, substantially the same operation as described above is performed.

In this way, in the circuit shown in FIG.
A voltage of 100 mL is applied. Therefore, for φIJ, if the power supply voltage Ev is 300 (v) and the transistor breakdown voltage is 1.5 times the maximum applied voltage using the force line as a line of force, then 300x2x1.5=900 (v). A voltage-resistant transistor is required. However, 1.
The withstand voltage of transistors used at high frequencies of 10Kilz or higher is approximately 6oo (v) at most.

Therefore, the circuit shown in FIG. 2 is particularly suitable for high frequencies.

There is a problem with high voltage inverters that it is difficult to put them into use.

In view of the above circumstances, this invention is capable of balancing the current during both steady and transient conditions, is applicable to high frequency and high voltage impark, and has a simpler configuration than conventional ones. This invention provides an inverter in which one end of the load is connected to a first inverter having a winding ratio inversely proportional to the magnitude of the current to be balanced and magnetically coupled to each other. The second coil is connected to the beginning and end of each winding of the first coil. Second
The end and beginning of each turn of the coil are connected to a line of the current to be balanced, and the other end of the load has a winding ratio inversely proportional to the magnitude of the current to be balanced. and connect to the beginning and end of each winding of the third and fourth coils which are magnetically coupled to each other, and connect the end and beginning of each winding of the fourth coil to the current line to be balanced. It's something that will happen.

Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 4 is a diagram showing the configuration of the first embodiment of the present invention, and in this figure, the transistor la.

The connection point of 3a is the coil C11 of the balance transformer 13LH.
The transistor lb is connected to the beginning of the winding No. 11.

The connection point of 3b is connected to the end of coil O+1b, and the end of coil Oua and the beginning of coil C1 are each connected to one end of the commonly connected rear load. Further, the connection point of transistors 2a and 4a is connected to the beginning of winding of coil 012a of balance transformer BL, , the connection point of transistors 2b and 4b is connected to the end of winding of coil C+zb, and the end of each winding of coils 012&10+zb and The beginning of the winding is connected in common and then the other end of the load is connected. In this case, the number of turns of the coils Oha and Cub and the number of turns of the coil Cl2m+0+zb are the same.

In the above configuration, first, the transistor ta.

When 11+, 4a, and 4b are turned on at the same time, a current flows in the direction of arrow Y through the load, and then transistor la
, lb, 4a, 4b are off, tiger/jista 2a, 2b,
When 3a and 3b are turned on, the arrow Y! A current flows in the direction, and the above operation is repeated, thereby supplying alternating current to the load. In this case, the currents of the transistors Ia, lb to 4a, 4b driven in parallel are balanced by balance transformers BL, . . . BL, 2 on the same principle as in the case of FIG.

Next, the operation of the circuit shown in FIG. 4 during current switching will be described with reference to FIG. 5. Now, for example, the transistor l
Assuming that a transitions to the OFF state and, on the other hand, the transistor lb is still in the ON state, the emitter current TA of the transistor 1a decreases, and with this decrease, the transistor lb increases due to the action of the balance transformer BL, . The emitter a T B decreases similarly (while maintaining the same value as the if flow Th). On the other hand, since the load current IL tries to maintain the same current, the decrease from 'Kamekuni8^+' is the diode D.
.

As a result, the diode D becomes conductive, and the potential at the point P becomes equal to the potential 0 at the negative voltage terminal of the DC power source E. That is, voltage EV is applied between the emitter and collector of transistor la. At this time,
If transistor lb is still in the on state, the potential at point P3 is +E■9 point P! Since the potential of the coil becomes 0, the potential of the coil becomes 0.
The voltages across both terminals of 11□ and Qllb are y:v/2 as shown in the figure.

Then, transistor ib is also turned off, and current Xl
, Dn both become O, the load current Tb is equally supplied through the diodes Da and Db.

Note that even when there are variations in the on-times of the transistors la and 1b, substantially the same operation as described above is performed.

In this way, in the circuit shown in FIG. 4, even in a transient state, the maximum voltage applied between the emitters and collectors of transistors la, lb... is the power supply voltage Bv, and therefore , one of the conventional circuits shown in FIG.
Only a voltage of /2 is applied. In addition, the circuit shown in Fig. 4 is a balance transformer BL, .

There is also an advantage that the number of B L, , is only half that of the one in FIG.

FIG. 6 is a diagram showing the configuration of a second embodiment of the present invention, and the embodiment shown in this figure is for a case where the number of switching elements operated in parallel at 1JA is three. In this embodiment, switch elements 5a, 5b, 5ck! and switch elements 8a, 8
When b and 8c are turned on, a current flows in the direction of arrow Y1 through the load, and when switch elements 6a, 6b, 6c and switch elements 7a, 7b, and 7c are turned on,
Current flows in the direction of arrow Y through the load. Here, balance transformer BL,, is line! , and l, and the turns ratio of each coil is 1:l. In addition, the balance transformer BL□ balances the currents flowing in lines 1 and 14, and
The ratio of the current flowing to line 7I4 and the current flowing to line 7I4 is 2:l.
Therefore, coil C+5a and C! The turns ratio with +sb is 1=2. Similarly, balance transformer B
L,4 is line β,.

16 current balance, the turns ratio is 1:1
, the balance transformer B'Lta is 2 in l? ,l.

It balances the current of Koi fi/Q 16
The turns ratio of a and cr6b is 1:2.

FIG. 7 is a diagram showing the configuration of a third embodiment of the present invention. In the embodiment shown in this figure, the number of switch elements driven in parallel is four, and when the switch cables 5a to 5d and 9a to 9d are turned on, a current flows in the direction of arrow Y8 to the load. , switch cords 6a-6d and 7a-7
When d is turned on, a current flows in the direction of arrow Y1L through the load.

In the case of this circuit, balance coils BL18 to B Lza
The turns ratio of each is 1:1.

In addition, the balance transformer BL has 2 magnetic fluxes that close the magnetic path.
It may be made by winding a coil on one side, or it may be made by eliminating the magnetic material and tightly magnetically coupling two coils.

As explained above, according to the present invention, a balance transformer is connected to each end of the load to balance the current, so that the current can be balanced both in steady state and in transient state. Since the voltage applied across the element is 1/2 that of the conventional one, there is an advantage that it can be applied to a high frequency, high voltage inverter, and there is also an advantage that the structure is simpler than the conventional one.

[Brief explanation of drawings]

Figures 1 and 2 are diagrams each showing an example of the configuration of a conventional inverter, Figures 3 (a) and 3) are explanatory diagrams for explaining the operation of the circuit shown in Figure 2, and Figure 4 is an explanatory diagram for explaining the operation of the circuit shown in Figure 2. FIG. 5 is a block diagram showing the configuration of the first embodiment of this invention, FIG. 5 is an explanatory diagram for explaining the operation of the same embodiment, and FIGS. FIG. 3 is a block diagram showing the configuration of a third embodiment. la, lb~4a, 4b...transistor (switch element), 5a, 5b, 5c, 5d~8a. 8b, 8c, 8d-・-switch cord,
B.L.H. BLHIBL16 +BI116 +BL20. BL2
3...Balance transformer, C++a + C++b
, Cl2a , Cl2b+ Cl6a l Cl5b
+C+6a + O+6b °”” Coil. Applicant Shinko Electric Co., Ltd. Figure 3 Figure 4 Figure 6

Claims (1)

[Claims] In an inverter in which a plurality of switching elements are driven in parallel, one end of the load is connected to a first switching element having a winding ratio inversely proportional to the magnitude of the current to be balanced and magnetically coupled to each other. The second coil is connected to the beginning and end of each winding of the first coil. The end and beginning of each turn of the second coil are respectively connected to the line of the current to be balanced, and the other end of the load has a turns ratio inversely proportional to the magnitude of the current to be balanced. and connected to the beginning and end of each winding of the third and fourth coils which are magnetically coupled to each other, and
．． An inverter in which the end and beginning of each winding of the fourth coil are connected to current lines to be balanced.