JPH0362324B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor switch device that drives a transistor using a method of detecting direct current. Conventionally, DC-CT has been commonly used as a method for detecting direct current, but this requires an AC power source for detection. Katsumata 2
In a system in which a magnetic core is used and the secondary windings wound around the magnetic core are connected in series, a slit ripple is generated each time the magnetic core is saturated.However, in the semiconductor switch device of the present invention, a Since the transistor is driven using a DC current detection method that enables detection with a single DC power supply and has low output ripple, it is possible to control the base current to increase or decrease according to the magnitude of the collector current. It is possible to realize an efficient switch.

FIG. 1 shows an example of a DC current detection device that is the basis of the semiconductor switch device of the present invention, and FIG. The figures are shown according to the indicated polarity. In Figure 1, S _I is a current source to be detected, CT1 and CT2 are current transformers,
Magnetic cores CO1 and CO2, primary windings N11 and N, respectively
12, Secondary winding N21, N22, Tertiary winding N3
1, N32, and quaternary windings N41, N42.
For each winding, the black circle mark indicates the direction in which the induced polarity of the voltage appears to be the same polarity. Q1 and Q2 are transistors, D1 and D2 are diodes, R _D1 , R _D2 and R ₀ are resistors, and V _C is a control DC power supply. Well now, t ₀
Assume that an output current i _S is supplied from the current source S _I at a time , and a signal pulse for triggering the Q1 transistor is applied to a terminal T ₁ at this time. When transistor Q1 switches on,
An indicated polarity voltage is applied to the tertiary winding N31 based on V _C , and as a result, an indicated polarity voltage is induced in the fourth winding N41, and this voltage switches on the transistor Q1 in a positive feedback manner. let As a result, the magnetic flux _φ1 of the magnetic core CO1 of the current transformer CT1 is magnetically oscillated in the reset direction. Primary winding N1 of CT1
1 is supplied with a current of i _S from the current source S _I , so the product of the N11 winding (the number of turns is n1 and the number of turns of the N12 winding is also equal) and i _S , that is, i _S × n1 ampere-turns. The product has almost the same value in the tertiary winding, and the value corresponding to i _S in the current i ₃₁ flowing through the N31 winding (the number of turns is n3, and the same is true for the N32 winding) is i′ ₃₁ The relationship ×n3≒i _S ×n1 holds true.
Since the N41 winding drives the transistor Q1, the current i ₄₁ supplied to its base becomes a load current for the N31 winding, and when this current is defined as i' ₄₁ , the above i ₃₁ becomes this i' ₄₁ The current is the sum of and i′ ₃₁ . Thus, as a result of transistor _Q1 becoming conductive,
Its emitter current is i ₃₁ + i ₄₁ . Then, the main current has a value corresponding to the primary current i _S.

On the other hand, for N21 winding (number of turns = n2, N22
(assuming that the number of winding turns is the same) A voltage of the indicated polarity is induced, and the diode D2 and transistor Q2 for this voltage are immediately cut off. In other words, no current flows through the N21 winding yet. In current transformer CT ₂ , transistor Q2 is momentarily cut off, resulting in N2
A current i ₂₂ flows through the second winding, and between this current and the current i _S flowing through the primary winding N12, i _S ×n1≒i ₂₂ ×n2
This is a value that satisfies the equal ampere-turn law. The emitter current of the transistor Q1 is this i ₂₂
It is necessary for the circuit to match the current. That is, i ₂₂ =i ₃₁ +i ₄₁ , and conversely, the emitter current of transistor Q1 is determined by i ₂₂ . When the emitter current of transistor Q1 is less than this _i22 (such as when the number of turns of N31 winding is large), the shortfall is made up by diode D.
1. When driving the transistor _Q1 through the N41 winding, the emitter voltage _V1 of the transistor Q1 is the value obtained by subtracting the base-emitter voltage of the transistor _Q1 from the N41 winding voltage, which is the voltage that normally cuts off the diode D1. Therefore, diode D1 does not conduct and the _i22 current becomes equal to the emitter current of transistor Q1. Therefore, when the i' ₃₁ current is small, the i ₄₁ current increases, and as i ₄₁ increases, i ₃₁ also increases, and in some cases, the transistor Q1
The base current may be greater than the collector current. In the figure, when the base resistor R _B1 shown by the dotted line is inserted, the base current value is limited to a predetermined range, and as a result, the i ₃₁ current is also limited.
At that time, diode D1 conducts to compensate for the emitter current of transistor Q1 which is less than the _i22 current. When this diode D1 is conductive, the current i ₂₂ flowing through the secondary winding N22 of the current transformer CT2 flows through the resistors R _D2 and R ₀ , and the current i 22 flows through the secondary winding N22 of the current transformer CT2.
A voltage of the indicated polarity is induced in each winding of 2. N42
The voltage in the winding cuts off the transistor Q2, and in the current transformer CT2, current flows only in the N22 winding, and the magnetic core CO
The magnetic flux of 2 is set. Since i ₂₂ flows through the voltage drop across resistor R _D2 , its value, V _RD2 , is the primary current i _S
The value is approximately proportional to .

Now, at time _t1 , when the magnetic core of current transformer CT1 completes its reset, as a result of the saturation of the magnetic core, the transformer action is lost, the N41 winding voltage disappears, and transistor Q1 suddenly disconnects. Then, the secondary current of current transformer CT1 corresponding to the primary current i _S becomes N21
flowing through the windings. It is D2-N21-R _D1 -R ₀ -
Take the path D1, i _S ×n ₁ ≒i ₂₁ ×n ₂ ,
The voltage drop V _RD1 of R _D1 has a value approximately proportional to i _S.
On the other hand, for current transformer CT2, the N22 winding is still used.
i ₂₂ current flows, D1-N22-R _D2 -R ₀ -D1
The voltage drop V _RD2 of R _D2 is as follows.
i The value is approximately proportional to _S.

At time _t2 , when a trigger signal pulse is applied to transistor Q2, transistor Q2 is switched on in a positive feedback manner due to the action of the N42 winding, and the sum of the currents flowing through N42 and N32 flows through the current transformer.
Matches the current flowing through the N21 winding of CT1, N2
The current i ₂₂ flowing through 2 is lost. Thus the current transformer
CT2 is reset. During this period, the current transformer CT1 is in the set mode, and the operation during this period is the same as the inversion of the current transformers CT1 and CT2 and the transistors Q1 and Q2 during the period t ₀ to t ₁ in the above explanation, so the details will be explained below. Omitted.

When the current transformer CT2 completes the reset at time _t3 , the current transformers CT1 and CT2 go into the set mode again, and the operation is the same as that between _t1 and _t2 .

When the trigger pulse is applied to the transistor Q1 again at time _t4 , it coincides with time _t0 of this description, and the same operation is repeated thereafter.

When turning on the transistors Q1 and Q2 alternately, when there is no load current i _S , the magnetic cores CO1,
If CO2 is in an unsaturated state, the impedance of the emitter loads N22 and N21 windings is sufficiently high, almost no current flows in transistors Q1 and Q2 even when they are switched on, and there is also a current limiting resistor in the base circuit. No need for R _B1 and R _B2 . When the magnetic cores CO1 and CO2 are saturated, there is no voltage feedback effect, so the transistors Q1 and Q2 do not continue to switch on.

The above operation is shown in Figure 2 over time, where a represents the current i S flowing from the current source, and b represents the current i _S flowing from the current source.
The movements of the magnetic fluxes φ ₁ and φ ₂ of the magnetic cores CO1 and CO2 of the current transformers CT1 and CT2, c is the N21 winding voltage, and e and d are the voltage drops V _RD1 and V of the resistors R _D1 and R _D2 . Indicates _RD2 .

OR output of voltage V _RD1 and V _RD2 is current
It is proportional to i _S , and when one output is lost, there is another output, so if you take out the output with OR, you can get an output with almost no ripple. It shoots resistor R ₀ and T ₃ ,
This is obtained by connecting a resistor via a diode in the direction in which the output is taken out from the _T4 terminal, and the output of the resistor becomes the OR output.

As is clear from the above explanation, according to the circuit shown in Figure 1, as a result of using two current transformers and resetting them alternately with the DC power supply via the switching means, current detection with almost no ripple can be achieved using a single DC power supply. You can get the output.

FIG. 3 shows a semiconductor switch device according to an embodiment of the present invention, in which a circuit for driving a transistor is constructed based on the current transformer shown in FIG. 1. Figure 1: Resistor in circuit
Since the current flowing through R ₀ is the sum of the currents flowing through R _D1 and R _D2 , there is no interruption while performing a current transformer action by alternately turning on transistors Q1 and Q2, and the current flows through the primary and secondary windings. is inversely proportional to the turns ratio of
Since a current proportional to the primary current i _S can be obtained at least all the time, connect the base circuit of the transistor to the position of the resistor R ₀ so that the collector current of the transistor flows through the primary windings N11 and N12. With this configuration, an efficient switch can be realized. This is shown in Fig. 3, but it differs from the basics of Fig. 1 in that the gate control device GCU, which detects the collector current and controls the drive of the main transistor MTR, is connected to the auxiliary transistor Q.
There is only one base signal that alternately turns on Q1 and Q2. The same applies to the circuit of FIG. 1, but even if pulses are applied to transistors Q1 and Q2 at the same time, only one of the CTs will always enter the reset mode and the other will enter the set mode.
This is because the secondary winding of the CT that entered the reset mode first reverse biases the auxiliary transistor for putting the other CT into the reset mode, thereby cutting it off. Furthermore, if both transistors are saturated on the reset side, both transistors Q1 and Q2 are not turned on and both operate in the set mode. Conversely, if both are saturated on the set side, the MTR is driven in only one reset mode. By configuring the CT with a relatively small magnetic core and shortening the interval between trigger pulses to transistors Q1 and Q2, the circuit shown in Figure 3 can be made smaller, and the base current of the MTR will automatically increase or decrease depending on the magnitude of i _S. Therefore, an excessive base current does not flow unnecessarily, and an efficient transistor switch can be achieved.

In addition, the number of turns of N31 and N32 windings and N21 and N2
The configuration is similar to the number of turns of two windings, and the control power supply V _C
It is desirable to lower the voltage in order to expand the practical range. Transistor Q to cut off MTR
1. If you stop giving the trigger signal to Q2,
The current transformers CT1 and CT2 will eventually become saturated in the set mode, and the MTR base current will be lost and the current will go out naturally. However, if you intend to turn off the current instantly, the transistors Q _X1 and Q _X2 in the diagram should be turn it on
All you have to do is bypass the MTR base current. like this
Based on the GCU, the circuit in Figure 3 can be created at any time.
You can turn MTR on and off.

As is clear from the above explanation, according to the semiconductor switch device of the present invention, the main transistor
In the MTR, since the base current increases or decreases depending on the magnitude of the collector current, Darlington connections are not necessary, and the MTR has the effect of enabling efficient driving.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an example of a DC current transformer for explaining the semiconductor switch device of the present invention, and FIG.
1 is a diagram for explaining the operation of the circuit shown in FIG. 1, and FIG. 3 is a block diagram showing an embodiment of the semiconductor switch device of the present invention. In the figure, CT1 and CT2 are current transformers, Q
1, Q2, and MTR are transistors, D1, D2 are diodes, and V _C is a control power supply. In addition, in the figure,
The same reference numerals indicate the same parts.

Claims (1)

[Claims] 1 A plurality of transformers each having first, second, and third windings wound around a saturable magnetic core, one end of each second winding of these plurality of transformers being connected to the third winding of the other transformer. a plurality of semiconductor switches connected to one end of each of the third windings of the plurality of transformers; a DC power supply having one end connected to the other end of each of the third windings of the plurality of transformers; The base and emitter are connected between the other end of each second winding, and
A semiconductor switch device comprising a transistor in which each first winding of the plurality of transformers is connected in series with a load and connected to a collector, and a gate control device for turning on the plurality of semiconductor switches.