JPS6173576A - Power converter - Google Patents

Abstract

PURPOSE:To prevent a high voltage from inducing at an output winding side by turning ON a shortcircuiting semiconductor switch during the OFF period of a drive switch, and preventing the output winding side from opening when a current is flowed to the current feedback winding of a current transformer. CONSTITUTION:A main circuit current flowed through a main switching semicon ductor element 1 is flowed as a reverse bias current through a current trans former 4 to the element 1 when the element 1 is turned OFF. The secondary side of the transformer 4 is shortcircuited by a shortcircuiting semiconductor switch 16 until the element 1 is turned OFF.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a current feedback type device equipped with a switching semiconductor element such as a transistor or a GTO.

[Conventional technology]

First, a conventional IL current feedback type power conversion device (for example, Japanese Patent Laid-Open No. 59-70181) will be explained with reference to Figure 6. 1 is a main switching semiconductor element (for example, a bipolar transistor, hereinafter referred to as main transistor). ), 2 is a drive switch such as a transistor that drives the main transistor 17 on and off, 6 is a drive winding N1 which is the first winding, a feedback winding N2 which is the second winding, and a third winding. In a drive transformer with a short-circuited winding N, the black dots in the diagram indicate the same short-circuited windings N,
Show polar ends. Further, 4 is a current transformer having a current feedback winding 1MNa and a current feedback winding Nb connected in series to the feedback winding N2 of the drive transformer 6, 5 is a resistor through which the excitation current of the drive transformer 6 flows, and 6 is a diode that becomes conductive at the initial stage of conduction of the drive switch 2 to form a short-circuit loop; 7 is a diode for preventing reverse current; 8 is a primary winding N;
and the main transformer with secondary windings Nll and 1, 9 and 10
is the secondary winding MN, a rectifier that rectifies the voltage between 11.1
2 constitutes a smoothing circuit, an accelerator, a capacitor, 13
．． 13' is a DC input terminal, 14.14' is a control power input terminal, and 15.15' is a DC output terminal. Figure 4 is a diagram showing the operating waveforms of each part of the power converter shown in Figure 3.
(a) is the voltage applied to both sides of the drive switch 2, (b)
) is the current flowing through the drive switch 2t, (C), (
d) U is the collector current and pace current of the main transistor 1, and (e) is the current flowing through the diode 6t.

Next, the operation of the power converter shown in FIG. 3 will be explained using FIG. 4.

First, when the drive switch 2 is turned on at time t1 to turn off the main transistor 1 which is in a conductive state,
As a result, carriers accumulated in the main transistor 1 are transferred to the drive winding N1 of the drive transformer 3 and the short-circuit winding N1.
Due to the transformer action of , the drive switch 2 and the diode 6
The closed circuit of the short-circuited winding N, and the shorted winding N, are closed. In other words, the short-circuited winding N becomes short-circuited, and the drive winding N1 and the feedback winding N
The transformer action of 2 is lost, and the pace current that was being supplied from the feedback winding N2 to the drive winding N1 is also changed to the short-circuited winding lfMNS.
11IIIK is sucked out. Further, at time t1, when the drive switch 2 is turned on, the variable grf, the
The main circuit current flowing through the feedback winding Na is also transferred to the closed loop consisting of the output current winding Nb1, the diode 7, the short-circuit winding N, and the drive switch 2. Since a current that is inversely proportional to the ratio, that is, a current whose magnitude depends on the main circuit current flows, a current whose magnitude is equal to the sum of the currents flowing through these two closed loops flows through the shorted winding N of the drive transformer 6. (Figure 4 (groan)
Accordingly, a voltage of an effective value is induced in the drive winding N1, with the unmarked side being positive and the black side being negative. This voltage is effectively reverse biased between the pace and emitter of the main transistor 1, and a sufficiently effective reverse base current is caused to flow through the pace pole of the main transistor 1 as shown in Fig. 4 (Φ).
significantly reduces storage time. Next, the same figure (c)
As shown in FIG. 2, when the main transistor 1 is completely turned off at time t2 and its collector current becomes zero, the current flowing through the windings Na and Nb of the current transformer 4 also becomes zero. Therefore, after time t2, an excitation current flows from the control power input terminal 14 to the winding N of the drive transformer 30 via the resistor 5t, and the drive transformer 3t is excited. As the excitation progresses further, the current flowing through the resistor 5 becomes constant and the voltage across the shorted winding N becomes 12 zero. Thereafter, when the drive switch 2 is turned off at time t, a voltage is induced in the drive winding N1 due to the energy stored in the drive transformer 3, and a voltage is induced between the pace and emitter of the main transistor 1. forward bias to bring it into conduction. When the main transistor 1 is switched on, the main transistor 1 rapidly becomes conductive due to the positive feedback action of the feedback winding N2. Next, at time t4, the drive switch 2 is turned on, and the same operation is repeated thereafter.

[Problems to be solved by the present invention]

However, in this conventional device, when the drive switch 2 is in the off state, the main circuit current flows through the current feedback windings N and K of the current transformer 4, and the current feedback winding Nb is in the open state, so the winding The drawback is that a very high voltage must be applied to each part on the Nb side, causing damage and deterioration of each part.

[Problem t - Means for Solving] In order to eliminate the drawbacks of the conventional device as described above, the present invention provides a short-circuiting semiconductor switch in parallel to the current feedback winding Nb of the conventional current transformer 4. It is characterized by the following:

[For production]

By turning on this short-circuiting semiconductor switch gold-driven switch during the off period, the current feedback winding of the current transformer is set to 1!
This prevents the feedback winding from becoming open when current is flowing, thereby completely preventing high voltages from being induced in the feedback winding.

〔Example〕

One embodiment of the present invention will be described with reference to FIG. 1. In this embodiment, a shorting semiconductor switch 161 is connected between the cand side of the diode 7 shown in FIG. 6 and the unmarked side of the output current winding Nb of the current transformer 4. :The setup is the same. Note that the same symbols in FIG. 1 as those used in FIG. 3 indicate components corresponding to those in FIG. 6, and the circuit operation when the main transistor 1 is turned off is the same as that in FIG. Since it is almost the same as the above, it will be omitted and the circuit operation at turn-on will be mainly described.

When the main transistor is in the on state, the drive switch 2 is in the off state, and the shorting semiconductor switch 16 is in the on state.The main circuit current flows through the current feedback winding N& of the current transformer 4, and its output T! A closed loop consisting of a Li winding N1, a diode 7 and a short circuit semiconductor switch 16 also has a winding iN,
A current flows that is inversely proportional to the turns ratio between L and winding Nb.

Main transistor-t-turn-off time t1
Drive switch 2t - close, short circuit semiconductor switch 1
6t- When the output current of the current transformer 4 is opened, a current proportional to the current of the main transistor, which has been flowing through the closed loop consisting of the output current winding Nb, the diode Z, and the short-circuit semiconductor switch 16, flows through the winding Nb. The current flows from the black side to the unmarked side of the winding Nb via the diode 6, the winding N of the drive transformer 6, and the drive switch 2. At this time, the winding N,
Since ta also flows through the closed loop consisting of the S drive switch 2 and the diode 7, it is preferable that the phases of these currents be in an open state in the winding mN of the drive transformer 6, but after the main transistor 1 is completely turned off. If so, it may be closed before time t.

In addition, if the diode ft-Zener diode is used, it will perform the same function as the conventional diode I, and at the same time, from time t1 to
It serves to suppress the voltage of the winding Nb when the impedance in the closed loop of the winding Nb, the diode toy, the winding N3, and the drive switch 2 is high at t2.
, the withstand voltage of the short-circuit semiconductor switch 16 is reduced.

Furthermore, as shown in the second port, a control a is connected in parallel to the resistor 5.
If the diode 17 is provided so that the power supply input terminal 14 side becomes the cathode, the winding aN will be
bs diode 8, diode 1-”18, winding Ns,
If the impedance in the closed loop of the drive switch 2, such as a FET, is high, the t position at the connection point on the unmarked side of the diode 18 and the winding N will be clamped by the control power supply voltage, resulting in a short circuit between the drive switch 2 and the FET. Semiconductors for use... Can be reduced in terms of withstand voltage for one person. This voltage effectively reverse biases the base-emitter of the main transistor to cause a sufficiently effective reverse pace current to flow through the base pole of the main transistor. Next, at time t2, when the transistor is completely turned off and the current flowing through the current transformer 4 becomes zero, the current flowing through the windings N and Nbt of the current transformer 4 also becomes zero. Therefore, after time t, the drive transformer 6 is energized from the control current input terminal via the resistor 5.

Next, at time t, the shorting semiconductor switch 16 is closed, the drive switch 2 is opened, and the main transistor 1 is turned on. Here, time t.

By closing the shorting semiconductor switch 16 and shorting the output current winding Nb of the current transformer 4, the voltage applied to each component connected to the winding Nb is completely suppressed, thereby preventing deterioration and destruction of the components. It is possible to prevent this, reduce losses in each component, and increase efficiency. Note that the shorting semiconductor switch 16 is operated until time t3 in order to increase the noise margin.

Here, the diode 18 is a diode for preventing backflow of excitation current and the like.

〔effect〕

As described above, in the present invention, when the main switching semiconductor element is turned off, the main circuit current flowing through the main switching semiconductor element is passed through the current transformer as a reverse bias current, and the main switching semiconductor element is turned off. Up to this point, the secondary side of the current transformer is short-circuited using a short-circuiting semiconductor switch, which prevents deterioration and damage to the parts connected to the secondary side of the current transformer and ensures stable operation. can.

Furthermore, if current detection is performed by connecting a current detection resistor or the like in series with the winding Nb of the current transformer 40, it is economically effective since there is no need to provide a separate current transformer for current detection.

[Brief explanation of the drawing]

1 and 2 are diagrams showing different embodiments of the power conversion device according to the present invention, FIG. 3 is a diagram showing an example of a conventional power conversion device, and FIG. 4 is the circuit shown in FIG. 6. It is a figure which shows the waveform of each part in. 1... Main switching semiconductor element 2... Drive switch 6... Drive transformer 4... Current transformer 8... Main transformer 13, 13'... DC input terminal 14, 14'... Control power input terminals 15, 15'
...DC output terminal 16...Semiconductor switch for short circuit - meridian diagram

Claims (1)

[Claims] A control pole of a main switching semiconductor element is connected to a first winding of a first transformer having at least three windings, and a second winding exhibiting a positive feedback characteristic with respect to the first winding. A drive switch is connected in series to the main terminal of the main switching semiconductor element, further connected in series to the third winding thereof, and a drive switch is connected in series to the main terminal of the main switching semiconductor element and the second winding of the first transformer. A second transformer having at least a current feedback winding and a current output winding inserted in series is provided, and by turning on or off the drive switch, the main switching semiconductor element is turned off or on, and During the turn-off period of the main switching semiconductor element, a current whose magnitude is dependent on the main circuit current flowing through the main switching semiconductor element is passed through the second transformer;
In the power conversion device that supplies a reverse bias current to the control pole of the main switching semiconductor element, a short-circuiting semiconductor switch is provided in parallel with the output current winding of the second transformer, and the short-circuiting semiconductor switch is provided in parallel with the output current winding of the second transformer. A power conversion device characterized in that a shorting semiconductor switch is turned on to suppress the voltage applied to each component on the output current winding side of the second transformer.