JPH0336339B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gate drive circuit for an amplification gate structure GTO.

GTOs generally have a larger ignition current than normal thyristors, so they have the disadvantage of requiring larger gate circuits. In order to improve this point, a GTO having an amplified gate (hereinafter referred to as A.G.) structure has recently been developed. This A/G structure
The operation of GTO is no different from that of an ordinary thyristor, but
The part called the auxiliary thyristor also has a GTO structure. FIG. 1 is an explanatory diagram of the configuration of an A/G structure GTO, and the GTO in FIG. 1 is an example of a buried gate structure. In Figure 1, GTO1 is the main GTO,
GTO2 is the auxiliary GTO, and this buried gate structure
To turn on the GTO, apply a gate signal to the gate terminal _G1 . This signal first assists
When the GTO turns on, the main current that flows at that time is supplied to the main GTO as an amplification gate current, and the GTO
turn on. On the other hand, it is used as an auxiliary gate drive circuit to turn off this GTO.
A diode D with the polarity shown is connected between terminal _G2 drawn out from the cathode electrode of the GTO (gate electrode of the main GTO) and gate terminal _G1 drawn out from the gate electrode of the auxiliary GTO.
There is a means to turn off the GTO by applying a reverse bias voltage (positive terminal K, negative terminal _G1 ) between the cathode terminal K and terminal _G1 of the GTO to cause an off-gate current to flow. The diode D is auxiliary
This is to apply a reverse bias between the gate and cathode of the GTO. In an A/G structure GTO that has such a function, it is possible to improve the firing sensitivity of the GTO by increasing the firing sensitivity of the auxiliary GTO, but in this case, it becomes difficult to reverse turn-off, When there is only one diode D, turn-off fails at a reverse bias voltage (approximately 1V). For this reason, it is necessary to connect multiple diodes in series, or to connect a Zener diode (the connection direction of this Zener diode is such that the cathode is G ₂
, the anode is connected to G ₁ . ) is being considered. However, increasing the reverse bias voltage using such means will cause the main GTO
Since most of the off-gate current flows through this reverse bias element, the loss there can no longer be ignored.

Figure 2 shows a gate drive circuit devised to improve the above drawbacks, and is equipped with an independent power supply E _OFF2 for turning off GTO2. Next, the operation of the circuit shown in FIG. 2 will be described.

When turning on the GTO, _the transistor Tr 1 is turned on (thyristor Th ₁ and transistor Tr ₂ are in the off state at this time). Then, an on-gate current I _gf flows from the on-gate power supply E _ON through the resistors R ₁ and R ₂ between G ₁ and K. At this time,
Immediately after the transistor Tr ₁ is turned on, the charge stored in the capacitor C is discharged through the resistor R ₂ , so the on-gate current I _gf has a waveform as shown in Figure 3, and when the GTO is turned on, it becomes an over-gate current. Become. These measures reduce switching loss when the GTO is turned on, and are well-known measures.

Next, when turning off the GTO, transistor Tr ₁ is turned off, thyristor Th ₁ and transistor Tr ₂ are turned on, and the off-gate power supply is turned off.
Main GTO (GTO1) and auxiliary GTO by E _OFF1 and E _OFF2
This is done by flowing off-gate currents I _gr1 and I _gr2 between the gate and cathode of (GTO2), respectively. However, even if the gate-cathode junction of the main GTO is restored, the lateral resistance of the P base layer shown in Figure 1
The off-gate current I _gr2 is allowed to flow between G ₂ and G ₁ through R _P during the off period. Normally R _P is about several ohms, so if E _OFF2 =5V and R _P =5Ω, for example, I _gr2 =1A will continue to flow even during the off period of the GTO.

In order to improve the above-mentioned drawbacks, a gate drive circuit shown in FIG. 4 has been devised. In this FIG. 4, instead of the off-gate power source E _OFF2 shown in FIG. 2, the electric charge charged in the capacitor C by the on-gate power source E _ON during the on period of the GTO (transistor Tr ₁ is on) is used. If the charge of the capacitor C is used in this way, once the charge is completely discharged, the off-gate current I _gr1 will continue to flow between G ₂ and G ₁ through the lateral resistor R _P during the off period of the GTO. This will solve the problem. In addition, if the resistance value is set such that resistance R ₂ < resistance R ₁ in the figure, the on-gate current as shown in Figure 3 can be obtained.
I can flow _gf . In Figure 4, diode
_D1 is for preventing the charge in the capacitor C from being discharged from the resistor _R2 through the resistor _R1 . In addition, after the charge of capacitor C is discharged, diode D ₂ connects between the gate and cathode of auxiliary GTO (G _2
-G1 ) to maintain low impedance and provide dv/dt tolerance. Even with such measures in place, the dv/dt tolerance was insufficient for the auxiliary GTO (which maintains a low impedance state between _G2 and _G1 ). The reason for this is that although it is not shown in Figure 1, as shown in Figure 6, the gate terminal
Naturally, a lateral resistance R'p also exists in the P base layer between N ⁺ of the N emitter of G ₁ and the auxiliary GTO. Therefore, G ₁ and G ₂ are connected to low impedance (diode D ₂
), the displacement current due to dv/dt flows.
When the voltage drop due to R'p becomes equal to or higher than the enlayer voltage of the PN junction, the displacement current flows through the cathode of GTO ₂ , so electrons are injected from N ⁺ into PN and easily turned on. Furthermore, if the auxiliary GTO accidentally fires, the main current of the auxiliary GTO flows through the thyristor Th ₁ → off-gate power supply E _OFF → main circuit load Z → main circuit power supply E _M , and the GTO is destroyed by this current. There was a risk that it would not only be damaged, but also destroy the gate drive circuit.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a gate drive circuit for a GTO with an amplified gate structure, which increases the dv/dt withstand capability of the auxiliary GTO and prevents damage due to erroneous firing of the auxiliary GTO. With the goal.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Parts that are the same as those shown in FIGS. 1 to 4 are designated by the same reference numerals. In Figure 5, the negative side of the on-gate power supply E _ON is connected to the cathode terminal K of the GTO, and its positive side is connected to the transistor
Connected to the anode side of diode _D1 via _Tr1 . The anode side is connected to one end of the capacitor C via a resistor _R2 . The other end of the capacitor C is connected to the gate terminal _G1 of the auxiliary GTO (GTO2) and also to one end of the resistor _R1 . The other end of the resistor _R1 is connected to the anode side of the diode _D1 .
Also, capacitor C has dv/
A diode D ₂ is connected in parallel to improve dt.

The above circuit is used to turn on the GTO. At this time, the transistor _Tr1 is turned on and the capacitor C is charged to the polarity shown.

The positive side of the off-gate power supply E _OFF is connected to the cathode terminal K, and the negative side thereof is connected to the common connection point between the resistor R ₂ and the capacitor via the transistor Tr ₂ . Further, the cathode side of a thyristor Th ₁ for energizing the off-gate current of the main GTO is connected to the negative side of the off-gate power supply E _OFF , and the anode side of the thyristor Th ₁ is connected to the terminal G ₂ of the GTO. Tr ₃ is a transistor for conducting off-gate current of the auxiliary GTO, and its collector is a thyristor.
It is connected to the cathode side of Th ₁ , and its emitter side is connected to the anode side via a diode D ₃ of the illustrated polarity. This diode D ₃ is a transistor
This prevents reverse voltage (E _OFF is applied when GTO is on) from being applied to Tr ₃ .

Note that in the above embodiment, the transistors Tr ₁ to _{Tr 3}
And thyristor _Th1 can be used as long as it is a switching element. Furthermore, the diode _D3 may be unnecessary when an element having a reverse breakdown voltage, such as a thyristor, is used in place of the transistor _Tr3 .

Next, to describe the operation of the above embodiment, since it was mentioned above when turning on the GTO, here we will explain the operation of the GTO.
Let's discuss the case of turning off. first,
Turn off transistor Tr ₁ , turn off transistor Tr ₂ ,
Tr ₃ turns on thyristor Th ₁ . By turning on these, the off-gate currents I gr1 and _{I gr2 are} generated between the gate and cathode of GTO1 and GTO2, respectively, at the voltage of the off-gate power supply E _OFF and the charging voltage of the capacitor C.
flow and then turn off. After turning off completely (approximately 10μS to 20μS), the thyristor
Th ₁ and transistor Tr ₃ are turned off. In addition,
If a certain amount of voltage remains in the capacitor C when the gate-cathode junction of GTO ₁ is restored, the thyristor will turn off when the transistor Tr ₃ is turned off.
Since a reverse voltage is applied to Th ₁ , thyristor Th ₁ is turned off without a special commutation circuit. G.T.O.
During the off period even after the transistor turns off,
Tr ₂ remains on. By doing this, the cathode of GTO ₁ and the gate G ₁ of GTO ₂
Since a reverse bias voltage is applied between them by the off-gate power supply E _OFF , it is possible to improve the dv/dt tolerance. This means that GTO ₁ 's reverse bias is
Although it is not directly related to the improvement of GTO ₂ 's DV/DT tolerance,
Even if the displacement current attempts to flow through the cathode of GTO ₂ as described above, the current will not flow because thyristor Th ₁ in Figure 5 is in the off state and diode D ₃ is present, and as a result, the displacement current will not flow through the cathode of GTO 2. ₂ 's dv/dt resistance is improved. On the other hand, for GTO ₂ , the thyristor
Since Th ₁ is in the off state, E _OFF → Z → E _M →
Since no loop is formed in which the main current flows through GTO ₂ → Th ₁ (off state), the gate drive circuit will not be destroyed.

As described above, according to this invention, GTO
During the off-period, a reverse bias voltage is applied between the gate and cathode of the main GTO.
It is possible to improve DV/DT tolerance and also provide supplementary
For the GTO, the switching element installed between the cathode of the auxiliary GTO and the negative side of the off-gate power supply is turned off.
This has advantages such as being able to prevent damage to the gate drive circuit due to erroneous firing of the GTO.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the configuration of the amplification gate structure GTO,
Figures 2 and 4 are conventional gate drive circuit diagrams, Figure 3 is an on-gate current waveform diagram, Figure 5 is a circuit diagram showing an embodiment of the present invention, and Figure 6 is a partial enlargement of Figure 1. It is a diagram. GTO1...Main GTO, GTO2...Auxiliary GTO,
E _ON ... Power supply for on-gate, E _OFF power supply for off-gate, Tr ₁ , Tr ₂ , Tr ₃ ... Transistor, Th ₁ ...
Thyristor, D ₁ , D ₂ , D ₃ ...diode, C...
...Capacitor, R ₁ , R ₂ ...Resistance.

Claims (1)

[Claims] 1 A pair of power supplies are provided independently for gate on and gate off, and the positive and negative sides of each are commonly connected and connected to the cathode of the main GTO, and the positive side of the gate on power supply and the auxiliary power supply are connected to the main GTO cathode.
A series circuit of a first resistor and a first switching element in an OFF state inserted in an electric path connecting the gate terminal of the GTO, and an anode terminal at a common connection point of the first resistor and a first switching element in an OFF state. a first diode whose cathode terminal is connected to the gate terminal of the auxiliary GTO through a series circuit of a resistor and a capacitor, and whose anode terminal is connected in parallel to the capacitor and whose anode terminal is connected to the gate terminal of the auxiliary GTO. a second diode, a second switching element in an on state connected between the negative side of the gate-off power supply and the cathode terminal of the second diode, and a second switching element connected between the negative side of the gate-off power supply and the gate terminal of the main GTO. ,auxiliary
The third in the on state for off-gate current conduction of the GTO.
A gate drive circuit for an amplified gate structure GTO, comprising a switching element and a fourth switching element in an on state for an off-gate current of a main GTO.