JPH0478020B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gate turn-off (GTO) thyristor with an amplified gate structure.

Generally, a thyristor or the like is provided with a part (amplifying gate) that amplifies its on-gate current, thereby allowing it to fire with a small gate current and at the same time greatly improving its turn-off characteristics. On the other hand, in GTO thyristors, which feature a self-turn-off function, there is a trade-off relationship between turn-on characteristics and turn-on characteristics, and the gate firing current tends to be larger than that of thyristors, and the turn-on characteristics tend to be inferior.
For this reason, forming a GTO thyristor with an amplification gate structure is an effective means, but currently requires a special structure to prevent the amplification gate from malfunctioning during turn-off and off periods. Amplification gate malfunctions and countermeasures will be explained below using a gate-embedded GTO thyristor as an example.

Figure 1 shows _{the configuration of} a GTO thyristor with _an amplification gate structure.
and an amplification gate section consisting of P _E , N _B , P _B , N _E1 layers.
AQ is configured on the same wafer, emitter layer N _E1 ,
High concentration impurity layers P _B1 ⁺ and P _B2 ⁺ in the shape of a lattice or strips are embedded in the P _B base layer facing N _E2 , and
The P _B1 ⁺ layer serves as the gate of the amplification gate section AG, and the P _B2 ⁺ layer serves as the gate of the main GTO section. The main GTO section and the amplification gate section AG are separated by a resistor R of the base layer _PB . In this structure, when turning on, a forward gate voltage is applied from the on-gate circuit 1 to the cathode K and the gate G1 in the center of the element, gate G1 → amplification gate N emitter layer N _E1 → gate G
2→The main GTO section is turned on by flowing the amplification gate current to the main GTO section N emitter N _E2 .
The diode D provided in the forward direction from the gate G2 to the G1 side prevents the on-gate current from flowing into the gate G2 without passing through the gate G1. On the other hand, when turning off, a reverse gate voltage is applied from the off-gate circuit 2 between the cathode K and the gate G1,
By passing an off-gate current from the main GTO part N emitter N _E2 → gate G2 → diode D, the main
Turn off the GTO section. Also, in the amplification gate section, gate G2 → N emitter N _E1 → gate G1
This turn-off occurs when the main GTO section is latched and the main current shunted to the amplification gate section is sufficiently small, so it is turned off before the junction recovery of the main GTO section N _E2 .

However, if the element main current is sufficiently small and the amplification gate section latches but the main GTO section does not latch, failure to turn off the amplification gate section is likely to occur. In this case, the time for junction recovery of the emitter N _E2 of the main GTO section due to off-gate bias is extremely short, and the amplification gate section cannot be completely turned off within this period. In other words, due to the junction recovery of N _E2 in the main GTO section, the total off-gate voltage is
Since it is applied to the N _E2 junction, no off-gate bias is applied to the amplification gate section.

When this amplification gate section fails to turn off, the main current flowing through the amplification gate section is
→ Emitter N _E1 → Diode D → Off-gate circuit 2, and the off-gate bias is in the forward direction with respect to this current path. This main current path is indicated by an arrow. In reality, the forward voltage drop of the diode D acts as an off-bias between the N emitter N _E1 of the amplification gate and the gate G1, but this level does not turn off the amplification gate section.

As mentioned above, failure to turn off the amplification gate leads to permanent destruction of the GTO thyristor.
When the thyristor is used in an inverter main circuit, there are problems such as arm short circuits.
Therefore, at present, as shown by the broken line in the figure, a Zener diode ZD for off-biasing of the amplification gate section is provided in series with diode _D , and a large off-bias voltage (5 to 10
degree) to promote the turn-off effect of the amplification gate section.

However, the Zener diode for off-bias
Providing ZD lowers the effective off-gate bias that can be applied to the main GTO section when voltage is applied from the same off-gate circuit 2, leading to a decrease in the controllable current of the element. Also, since the turn-off gate current of a GTO thyristor is large, for example
Turning off the main current of 1000A requires an off-gate current of about 250A, and this large off-gate current is generated by diode D and Zener diode.
There will be a large power loss in ZD, and diode D,
It requires a large capacity ZD, and because it is large, there are problems with its mounting structure.

An object of the present invention is to obtain a gate turn-off thyristor that can reliably turn off an amplification gate section without providing an off-gate bias outside the element.

The present invention is characterized by a structure in which the off-gate current of the main GTO section is routed through the P base directly below the N emitter N _E1 of the amplification gate section.

FIG. 2 shows an embodiment of the invention. The same figure is the first
The difference from the diagram is that _three N emitter N layers are diffused and formed in the P base P _B layer of the main GTO section without providing the diode D and Zener diode ZD circuits.
Electrode G3 on this N emitter _N3 and the amplification gate section
Conductive connection is made between the electrode G4 formed on the P base P _B layer of AG, and the N emitter _N3 layer and electrode G4
In the P base P _B layer facing the gate layer P _B2 ⁺ ,
This is the point where the main current from the anode side is not allowed to flow by using P _B1 ⁺ as a band layer. N emitter layer N _E3
is hidden from the anode A side by the strip layer P _B2 ⁺ layer, thereby preventing erroneous thyristor operation due to the presence of the _N3 layer.

In such a structure, the turn-on operation is similar to that shown in Figure 1, and the on-gate current is from gate G1 → emitter N _E1 → gate G2 → emitter
It flows through the path of N _E2 and turns on. here,
With separation resistor R and gate G3 between P _B2 ⁺ and P _B1 ⁺ layers
The _N3 layer prevents the on-gate current from being shunted to areas other than the emitter N _E1 layer. Next, at turn-off, the off-gate current is emitter N _E2 → gate G
3 → Gate G4 → Embedded gate P _B1 ⁺ → Gate G1
flows along the path of and turns off.

In a state where the conventional amplification gate part AG fails to turn off, in this embodiment, the main current path is as shown by the arrow: anode A → emitter N _E1 → gate G2 → P _B2 ⁺ → emitter N ₃ → gate G3 → It becomes a closed loop path of gate G4 → P _B2 ⁺ → gate G1, and after a transient current actually flows, the main current shifts to the path of anode A → buried gate P _B1 ⁺ → gate G1, and from emitter N _E1 . Electron injection also stops and the amplification gate section AG is quickly turned off.

According to this embodiment, the structure is such that the off-gate current of the main GTO section is drawn out from the gate _G1 through directly under the amplification gate N emitter N E1, so the current flowing through the amplification gate section has only one path that passes directly under the N emitter N _E1 . In the path, it cannot continue to flow as it forms a closed loop by itself, and shifts to the path from the buried gate P _B1 ⁺ to the gate G1, stopping electron injection from N _E1 and rapidly and reliably turning off the amplification gate section.

FIG. 3 shows another embodiment of the invention. The difference between this diagram and Figure 1 is that an off-bias circuit such as a diode D is not provided, and the buried gates P _B1 ⁺ and P _B2 ⁺ of the main GTO section and the amplification gate section are extended in the width direction. to form connections with each other,
The structure eliminates the separation resistor R between the GTO section and the amplification gate section.

In this embodiment as well, the off-gate current of the main GTO section flows from the buried gate P _B2 ⁺ to the gate G via P _B1 ⁺ .
1, the current flows directly under the emitter N _E1 , and the current flowing through the amplification gate transitionally becomes a closed loop shown by the broken line, but when the electron injection from the emitter N _E1 stops, the current circuit shifts to the current circuit shown by the solid line. Thus, quick turn-off of the amplification gate section can be obtained.

As described above, according to the present invention, since the structure is such that the off-gate current of the main GTO section passes through the P base directly under the N emitter of the amplification gate section, the amplification is performed after the junction recovery of the N emitter N _E2 of the main GTO section at turn-off. Even if the gate section is in a conductive state, a closed loop is formed in its current circuit to stop electron injection into the N emitter N _E1 , thereby enabling reliable turn-off of the amplification gate section. As a result, in the present invention, an off-bias external circuit (diode D
etc.), power loss in the external circuit and problems with its connection configuration are eliminated, and the off-gate circuit voltage can be lowered to ensure reliable turn-off operation, which improves the controllable current of the GTO thyristor. Become.

Note that the present invention is not limited to a buried gate type GTO thyristor, but can be applied to a normal GTO thyristor having a strip-shaped gate electrode exposed on the element surface to obtain the same effect.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a GTO thyristor with a conventional amplification gate structure, FIG. 2 is a block diagram showing one embodiment of the present invention, and FIG. 3 is a block diagram showing another embodiment of the present invention. 1...On-gate circuit, 2...Off-gate circuit, D...Diode, ZD...Zener diode, P _B1 ⁺ , P _B2 ⁺ ...Embedded gate, G1, G
2, G3, G4...Gate, K...Cathode, A
……anode.

Claims (1)

[Claims] 1. An amplification gate section consisting of P _E , N _B , P _B , N _E1 layers is provided on the same wafer as a main GTO section consisting of P _E , N _B , P _B , N _E2 layers, and the main current of this amplification gate section is Mainly
In a gate turn-off thyristor with an amplification gate structure that uses the on-gate current of the GTO section, the main
A gate turn-off thyristor having an amplification gate structure, characterized in that the off-gate current of the GTO section is drawn out to the off-gate G1 via the N emitter N _E1 of the amplification gate section.