JPS59221030A - Balancing circuit of load current - Google Patents

Abstract

PURPOSE:To eliminate the use of many balancing transformers or a transistor which has a margin of breakdown strength by adding a collector current negative feedback winding to a driving transformer to correct an unbalanced current. CONSTITUTION:For a driving transformer DT, a winding N2 is used for negative feedback and a winding N3 is used to give the positive feedback of the sum of collector currents of all transistors TRQ1-Qn to the base of each TR and then supply a base current after these TRs are turned on. In such constitution of driving circuits A1-An, the current flowing to the winding N3 is positively fed back to a base winding N1. However the collector current of each TR flowing to the winding N2 is negatively fed back to the N1. This current can balance the current in a saturated ON state of plural switching TRs connected in parallel to each other and also can balance the variance of turn-off characteristics. Thus the voltage waveform obtained in a turn-off state of each TR can be balanced even with the inductance load.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention (・When switching a common load current by multiple transistors at the same time,
The present invention relates to a load current balance circuit that can easily achieve a balance of collector current (load sharing current).

When using a transistor as a switch element to switch the load current, it is not possible to use a single transistor, but if the current capacity or internal loss type terminals (collector, emitter, base) are connected in parallel, the characteristics between the transistors will change. This difference causes an imbalance in the current flowing through each transistor. For this reason, conventionally, the current flowing through each transistor was balanced by a circuit as shown in FIG. 1, for example.

Fig. 1 shows the DC power supplied from the DC power supply Ei. When it is desired to obtain the switching voltage by the switch circuit fτ'5S driven by the drive signal from the drive pulse generation circuit P, the main transformer for external voltage or voltage step-down is used. If we consider that the load zL includes a rectifier circuit, a smoothing circuit, etc., and is obtained by them, the switch circuit section S itself is the first
The circuit shown in the figure may be used.

In FIG. 1, P is a drive pulse generation circuit, A1 to An
are R%b circuits for switching transistors Q1 to Qn, and each has a drive transformer DT, and transistors Q1 to Q, n are once turned ON by an on signal from drive winding N4, and then the collector current winding is turned on. 11Nz (
The current remaining after subtracting the base current flowing through the winding N1 from the emitter current, that is, the current flowing through the winding N2, flows through the winding N2.The base winding Nx supplies the base current by positive feedback of the collector current. It constitutes a current feedback type drive circuit.

In this circuit, the unbalance of the collector current caused by the variation in characteristics between each transistor is balanced by the balancing current transformer (BT12 to BT11), and the load sharing current amount 1 to il of each transistor is almost balanced. . However, this conventional circuit not only requires the same number of balancing current transformers as switching transistors, but also requires two balancing current transformers to be inserted into the load circuit seen from the transistor, resulting in a large wiring inductance. This increases the surge voltage between the collector and emitter when the transistor is turned off.Also, if there are variations in the storage time of the transistor, the surge voltage between the collector and emitter of the transistor with a short storage time that turns off first will be particularly large. This causes an imbalance in the voltage waveform at turn-off, and it is necessary to use a transistor with sufficient voltage resistance.

As described above, the conventional circuit has the disadvantage of high cost due to the necessity of a large number of balancing current transformers and the necessity of using transistors with sufficient voltage resistance.

The present invention has been made in order to eliminate the disadvantages of the prior art as mentioned above, and it is therefore an object of the present invention to solve the problem of parallel connected switching transistors which require a large number of balancing current transformers. The purpose of this invention is to provide a load current balance circuit.

”: In order to achieve the above object, the present invention provides a load current balance circuit for parallel-connected switching transformers, comprising:
A drive transformer having at least three windings is provided for each of the transistors, and a first winding υ of a corresponding drive I-lance is connected between the base and emitter of each transistor. One end of the h'520 winding of the corresponding drive transformer is connected to the emitter of the same, and all the circuits from the collector of each transistor to the other end of the second winding are connected in parallel, and each of the drive transformers A current proportional to the sum of the collector currents of the transistors (load current) is passed through the third winding of the transistor.
When the second winding final current increases, the base current flowing through the first winding decreases, and when the third winding current increases, the base current flowing through the first winding decreases. Each of the first to third windings is wound around the drive transformer so that the current increases.

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 2 is a circuit diagram showing one embodiment of the present invention.

This embodiment is based on the balancing current transformer (
Drive transformer I) T instead of 13T12~BTn1)
It is characterized by having a collector current negative feedback winding for correcting unbalanced current.

In the drive transformer DT shown in Figure 2, N2 is used as a negative feedback winding, and N3 is used to positively feed back the sum of the collector currents of all transistors to the base of each transistor to supply the base current after turn-on. Use as winding wire. If a g-dynamic circuit is constructed in this way, the current flowing in the N3 winding (collector current sum of all transistors Σjk) will be given positive feedback to the base winding N1, but the collector current of each transistor flowing in the N2 winding will be positive feedback. The current is negatively fed back to the base current i +3 (
m) has a value expressed by the following formula.

However, from the collector current of the 'Inrmth transistor, the following can be seen from equation (1) above. For a certain load (if the collector current im increases, the base current I of the transistor
If B(m) decreases and, conversely, collector current im decreases, base current iB(.1) increases.

In other words, this negative feedback operation distributes the load of each transistor (
1. Working as a balance of collector current 11~In). Cru. Here N3 = -N2 ... song -
(2) However, if n is the number of parallel circuits, the total amount of current feedback to the base winding NNx can be made exactly the same as in the case of FIG.

Next, there are variations in program time between each transistor.
Considering the case where the turn-off characteristics of the l-th transistor are different from those of the others, a) If the accumulation time is short and the turn-off is fast, the collector current im of the m-th transistor becomes 0 faster than the collector current of the other transistors. Also, as shown in the above equation (1), the collector currents of other transistors are fed back as the base current r B (m), so an effect occurs that prevents the collector current im from quickly reaching O.

b) When the accumulation time is long and the turn-off is slow In the above equation (1), if the collector currents other than the collector current im of the m-th transistor become 0, the base current in(m
) becomes. From equation (2), since N3≦N2 (n≧2), the base current i B (m) becomes O or a negative current, and the base current immediately becomes 0 or a reverse bias current occurs, and the collector current im quickly becomes 0. The effect of

In other words, in the present invention, the circuit has the effect of balancing not only the current in the ON state of a plurality of switching transistors used in parallel, but also the variation in turn-off characteristics, and is effective even in the case of an inductance load. Since the voltage waveforms at turn-off of each transistor are balanced, the practical effect is very large.

Figures 2q and 3 are circuit diagrams showing other practical AC+j examples of the present invention. Embodiment Q11 shown in the figure shows a circuit 1 that is an improvement to the circuit shown in Fig. 2 for the case where there is a large number of parallel uses.
, In the circuit shown in Figure 2, the positive feedback winding of each drive transformer? N3 are connected in series, and the load current flows directly through them. Therefore, when a large number of transistors are used in parallel, the wiring inductance of the main circuit becomes a problem, causing a large surge voltage when the transistors are turned off.

In the circuit shown in Fig. 3, the current flowing through the N3 winding is converted into a small current through the load current.L - By preventing large load currents from flowing directly through each drive transformer, the wiring inductance of the main circuit is reduced, and the N3 winding of the drive transformer is The winding has a small current and is easy to manufacture.

In this case, the relationship between the turns ratios of the drive transformer DT and the current transformer CT for load current conversion is N = = (N2'/N1') - N2 ・
If we use (3), we can achieve exactly the same effect as in Figure 2. However, Nl' and N2' are current transformer C
The number of turns of the primary winding and the secondary winding of T.

In FIG. 3, diode D1 serves to ensure that the magnetic flux of current transformer CT is reset.

As described above, the circuit according to the present invention uses the winding that carries the collector current of the current feedback drive transformer for negative feedback operation for collector current balance, and further uses a current proportional to the total collector current as the base current. Is it possible to switch multiple transistors by adding new windings for positive feedback? There is a story in 21'j that it was made to balance Cj i5f and voltage ζ.

1) The current balance circuit is the same as the conventional one (using a current transformer for balance),
[<It is easy to apply it no matter how many transistors are used in the 51r' row, so in a circuit that uses transistors as a switch resistor, the capacity of the switch circuit can be easily reduced by A large-capacity accelerator that can be increased to 1:, jli, J')
T biq inverter.

]) C-+) There are some difficulties in the application of C-variant t・1 convergence, etc., (:).

4 f7iJ r'+'- explanation of the drawings Figure 1 shows the parallel switching transistor load '1', TM (Ha57
, /(Time 1ii O) Time 1i' showing the conventional example); I>
<l, 2F 2 [wish.

j:'j', :3 figures are 1 to -1 of unexploded pIJ, respectively.
Draw the 3 examples with 4 scrap circuit diagrams.

Code explanation] 1...-7i'j jl+: Scar voltage, E.
・・・・Electrical voltage for μIK dynamic circuit.

ZJ,...Load, Q1~Qn...--0
1; Conveniently used suites, Q...-
... Drive transistor, A1 to An... Drive circuit for transistors Ql to Qn, BT12 to B T n
l......ノ(Bflr for Lance.

device, P...drive) pulse generation circuit, DT...
...B dynamic transformer, R...resistance, D, DI
・・・・・・－Diode.

CT...---change (&'dL S...Switch circuit section.

Daitanukito Bu “Buried Earth Namiki Akio Agent Patent Attorney Kiyoshi Matsuzaki

Claims (1)

[Claims] 1) A load current balance circuit for parallel-connected switching transistors, in which a driving transformer having at least three windings is provided for each of the transistors, and a driving transformer is provided between the base and emitter of each transistor.
, 1. Q), connect ε) to the first winding of the lance, connect one end of the second winding of the Takato transformer corresponding to the emitter of each transistor, and connect the 20th winding from the collector of each transistor to the The other 91 circuits are all connected in parallel, and a current proportional to the sum of the collector currents (load current) of the respective transistors is caused to flow through the third winding of each of the four drive transformers, and the g2 When the current in the third winding increases, the base current flowing through the first winding decreases, and when the current in the third winding increases, the base current flowing through the first winding increases,
A load current balance circuit characterized in that each of the first to third windings is wound in the drive transformer.