JPH078133B2 - Gate drive device for thyristor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to gate driving of thyristors used in power converters such as inverters, and more particularly to a device suitable for driving gates of many thyristors.

<Prior Art> In recent years, a power converter using a thyristor has remarkably increased in capacity, and particularly in a fusion device or the like, higher voltage and higher current have been attempted. On the other hand, increasing the capacity of the thyristor does not keep up with increasing the capacity of the power conversion device, and a large number of thyristors are connected in series / parallel or multiphase to cope with increasing the capacity. At present, it is not uncommon for a device to use several hundred thyristors.

In such a large power conversion device using a large number of thyristors, the gate drive device also becomes large in size, and there is a problem that heat generation increases and reliability decreases.

When using a large number of these thyristors, the gate current condition is to prevent variations at turn-on, so that a large-current gate pulse with a steep rise and turn-off due to an oscillating current at turn-on of another phase thyristor are prevented. Therefore, the gate pulse having a small current and a long time width is the most important point.

As this type of device, for example, those shown in FIGS. 3 and 4 have been proposed. The former (Fig. 3) is
Two DC power sources Ea and Eb (Ea> Eb) with series resistance Ra and Rb
A capacitor Ca is connected via a diode Da and Db, the primary winding of the gate transformer Ta is connected between the terminals of this capacitor Ca via a transistor Qa, and a diode is connected between the terminals of the primary winding. It is configured by inserting Dc.

Then, when the transistor Qa is in the cutoff state,
Ea of the capacitor Ca is charged by the DC power supply Ea,
When the transistor Qa becomes conductive, the electric charge of the capacitor Ca is discharged through the primary winding of the gate transformer Ta. Since the resistance Ra is set to a sufficiently large value, the DC power supply Ea
The current supplied from is sufficiently smaller than the discharge current of the capacitor Ca. When the terminal voltage of the capacitor Ca is equal to the DC power supply Eb, energizing current i _T a gate transformer Ta is a DC power source Eb
The gate pulse signal having a large rising current and a small wide current is supplied to the thyristor Tha as shown in FIG. is there.

In the latter (FIG. 4), the DC power source Ec includes a series circuit including a diode Dd, a series resistor Rc, and a capacitor Cb, a diode De, a DC reactor La, and a transistor Qb.
Connected to a series circuit consisting of the above resistor Rc and capacitor
Both terminals of a diode Df provided between the connection point of Cb and the connection point of the DC reactor La and the transistor Qb are connected to the primary winding of the gate transformer Tb.

Then, assuming that the capacitor Cb is charged to Ed (Ed> Ec), the electric charge of the capacitor Cb is discharged through the primary winding of the gate transformer Tb due to the conduction of the transistor Qb. The discharge continues until the voltage of the capacitor Cb becomes equal to the DC power supply Ec, after which the diode Dd becomes conductive and the DC power supply Ec causes a resistance in the primary winding of the gate transformer Tb.
It flows through energizing current i _T b via Rc, as shown in FIG. 4 (b), and supplies a small gate pulse signal rising current is large wide current to the thyristor Thb. On the other hand, since the transistor Qb is turned to the conductive state, starts to flow current i _L a by the DC power supply Ec is the DC reactor La, the current i _L a increases over time. When the transistor Qb is cut off, the current i due to the DC reactor La
_The current due to the excitation energy stored in _L a, that is, the inductance, charges the capacitor Cb through the diode Df and raises the terminal voltage of the capacitor Cb to Ed (JP-B-63-37712).

<Problems to be Solved by the Invention> However, in the former case, in order to supply the gate pulse signal, the terminal voltage of the capacitor Ca must be charged to Ea through the resistor Ra by the DC power supply Ea. Therefore, the resistance Ra requires energy of 1 / 2Ca · (Ea−Eb) ² , which causes a problem of large capacitance and large heat generation when a large number of thyristors are gate-driven. . Further, the current due to the excitation energy accumulated in the gate transformer Ta is designed to flow back through the diode Dc and be reduced when the transistor Qa is cut off. Since it has an L / R time constant with the winding resistance R and decreases, it does not abruptly become zero. Therefore, when the repetition frequency is high, the gate transformer is magnetically saturated when the next gate pulse signal is supplied, and the desired value is obtained. However, there is a possibility that the turn-on of a large number of thyristors may be varied, and the reliability is lowered.

In the latter case, a DC reactor requiring an iron core of the same degree is required in addition to the gate transformer, and there is a problem that the device becomes large when a large number of thyristors are gate-driven. . Moreover, the energy stored in the gate transformer is not used, and therefore, like the former case, it does not become zero rapidly, and the excitation energy of the DC reactor simply charges the capacitor to a voltage Ed higher than the DC power supply Ec. Since it is used only for the purpose, there is a problem that the power loss becomes large and the heat generation becomes large when the gate drive of many thyristors is performed. In addition, the voltage Ed (Ed> Ec) that charges the capacitor is set by the excitation energy of the DC reactor, so the first gate pulse signal rises because the capacitor terminal voltage is charged only to the DC power supply Ec. Has a problem that a pulse with a large current can be obtained. Moreover, since a general power supply controls the load “ON”, “OFF” and phase with a thyristor, the load “OFF” time, that is, the gate OFF period. Is not constant,
When this period becomes long, the self-discharge of the capacitor is also added, and the initial gate pulse signal becomes low, and there is a problem that reliability is remarkably deteriorated in the case of gate driving a large number of thyristors. Furthermore, since the charging voltage Ed of the capacitor is determined by the value of the DC reactor and the gate pulse width, the fluctuation of the charging voltage becomes very large.To stabilize this, if the accuracy of the DC reactor is increased, it becomes expensive and the pulse width becomes The control circuit for keeping the constant value also has a problem that it takes a lot of time and effort to adjust the control circuit in the case of multiple phases, the cost is high, and the versatility is lacking.

The present invention has been made in view of the above points, and an object of the present invention is to save power and miniaturize a gate pulse signal having a large current with a sharp rise and a wide small current. It is intended to provide a device that can be supplied, has high reliability of gate driving, and has high versatility.

<Means for Solving the Problems> In order to achieve the above object, the present invention provides a gate transformer 1
The reset winding and the drive winding are connected in series on the next side, and the common end of both windings is connected to the other end of the discharging capacitor whose one end is circuit grounded. The cathode of a diode whose anode is circuit-grounded is connected to the other end of the drive winding, the other end of the drive winding is connected to the circuit ground via a switching element, and a capacitor between the terminals of the capacitor is connected via a charging resistor. One DC power supply is connected, and a second DC power supply having a voltage lower than that of the first DC power supply is connected via a forward diode.

<Operation> When the capacitor is charged to the voltage of the first DC power supply and the switching element is turned on, the capacitor discharges its charge through the drive winding, generating a large-current gate current with a sharp rise, When the terminal voltage of is equal to the voltage of the second DC power supply, the second DC power supply excites the gate transformer to generate a wide and small current gate current, and the thyristor has a steep rise and a wide gate. Supply pulse signal. When the switching element is cut off, the current due to the excitation energy of the gate transformer charges the capacitor through the reset winding and returns.
It is rapidly reduced to zero. After that, the gate pulse signal is supplied from the second DC power source and the discharge of the capacitor charged by the excitation energy of the gate transformer.

<Example> An example of the present invention will be described with reference to Figs.
In FIG. 1, Th ₁ , Th ₂ , ... Thn are a large number of thyristors inserted in a main circuit to which loads (not shown) are connected.
1, 1, ... Are connected to the first DC power supply E ₁ and the second DC power supply E ₂ (E ₁ > E ₂ ) having a voltage lower than this, and the thyristors Th ₁ , Th ₂ , ...... A drive circuit that outputs a gate pulse signal to the gate of Thn. This is _one of the gate transformer T ₁ with output winding N ₃ on the secondary side.
The reset winding N ₂ and the drive winding N ₁ are connected in series on the next side, and the common end (connection of N ₂ and N ₁₎ between the reset winding N ₂ and the drive winding N ₁ is arranged. Point) to the other end of the discharging capacitor C ₁ whose one end is circuit grounded, and to the other end of the reset winding N ₂ which is connected to the cathode of the diode D ₂ whose anode is circuit grounded. The other end of N ₁ is connected to the collector of a transistor Q ₁ whose emitter is circuit-grounded, and a DC power supply E ₁ is connected between the terminals of the capacitor C ₁ via a high resistance charging resistor R ₁ , and Connect DC power supply E ₂ via diode D _{1 in the} forward direction, and output winding of gate transformer T ₁ .
A gate pulse signal is output from N ₃ via a diode D ₃ and a gate resistor R ₂ .

Next, the operation for the thyristor Th ₁ will be described.
The operation for the thyristors Th ₂ , Th ₃ , ... Thn is performed in the same manner, and thus the description thereof is omitted.

Now transistor Q ₁ is in the cut off state and capacitor C ₁
When the DC power supplies E ₁ and E ₂ are supplied while the electric charge of is also zero,
The capacitor C ₁ is charged by the DC power supply E ₂ with the diode D ₁ conducting and is also charged by the DC power supply E ₁ through the resistor R ₁ with a time constant of C ₁ R ₁ and the charging voltage is DC. Power E ₂
When the voltage becomes higher than the voltage V _{E2 of} V ₁ , the diode D ₁ becomes non-conductive, and thereafter, the voltage V _E1 of E ₁ is charged by the DC power supply E ₁ .

In this state, when the transistor Q ₁ conducts at time t _{0 in} FIG. 2, the capacitor C _{1 transfers} the electric charge to the gate transformer T ₁
Discharge (Fig. 2 (e)), which causes a current i _T1 with a steep rising and high peak value to flow in the drive winding N ₁ (Fig. 2 (c)), and the output winding N ₃ The gate current i _G having a high peak value with a sharp rise is output to the gate of the thyristor Th ₁ via the diode D ₃ and the resistor R ₂ (FIG. 2 (b)), and turns on the thyristor Th ₁ .

Then, the discharge of the capacitor C ₁ continues until its terminal voltage becomes equal to the voltage V _E2 of the DC power source E ₂ (see FIG. 2, t ₁
Point), then the diode D ₁ is conducting, by the DC power supply E _2, electric current i _T1 to the drive winding N ₁ of the gate transformer T ₁ (FIG. 2 (c)), thereby, the gate current i _G Is
A current having a value sufficiently higher than the gate trigger current I _GP of the thyristor Th ₁ is held in the conduction period of the transistor Q ₁ (FIG. 2A) and output from the output winding ₃ to the gate of the thyristor Th ₁ (second). Figure (b)).

On the other hand, the exciting current iex flows through the gate transformer T ₁ from the time when the transistor Q ₁ is turned on, and this increases with the passage of time (FIG. 2 (c)).

When the transistor Q ₁ is cut off at time t 2 in Fig. ₂ ,
Current i _T2 by the excitation energy accumulated in the gate transformer T ₁ by the excitation current iex flows from refluxing route _{N 2 → C 1 → D 2} → N 2 through the reset winding N _2, a capacitor C ₁ Charge and charge the terminal voltage V _C1 to the voltage V _{E1 of the} DC power supply E _1.
The battery is charged (Fig. 2 (e)). At the same time, since the above excitation energy is used to charge the capacitor C ₁ , its current i
_T2 rapidly decreases to zero (Fig. 2 (c)).

After that, the gate pulse signal to the thyristor Th ₁ is discharged by the capacitor C ₁ charged by the excitation energy and the DC power source E ₂ .

<Advantages of the Invention> According to the present invention, the excitation energy of the gate transformer is effectively used to charge the capacitor, so that the power loss can be made extremely small and a large number of thyristors are gate-driven. Even if it is a thing, heat generation can be extremely reduced. Moreover, unlike the conventional case, a series reactor as an energy charger is not required, and the device can be downsized and the cost can be reduced. Further, since the first DC power supply (power supply with a higher voltage) is used only for the initial charging of the capacitor, the charging resistance can be set to a high resistance, and the first DC power supply described above can be used. The second DC power supply having a voltage lower than that of the power supply may be a power supply sufficient to output a gate current having a value that sufficiently holds the gate trigger current of the thyristor, so that the power supply capacity can be reduced and power consumption can be reduced. Can be extremely small. Furthermore, since it is charged by the first DC power supply when it is at rest, a stable gate pulse signal can be output accurately, and even if it drives the gates of many thyristors, the reliability is much higher. Can be Furthermore, since the current due to the excitation energy of the gate transformer charges the capacitor and causes it to flow back, it can be rapidly reduced to zero, and the gate of the thyristor that is bridge-connected and phase-controlled can be double-pulsed. Even when driving, the desired gate pulse signal can be output accurately, and even if the pulse width becomes small and the excitation energy decreases, auxiliary charging can be performed by the first DC power supply, so the pulse width remains constant. Since there is no need to make adjustments, the need for adjustment is eliminated, the range of application can be expanded, and versatility can be further improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a diagram for explaining the operation thereof, FIG. 3 is a conventional example, FIG. 1 (a) is a circuit diagram, and FIG. FIG. 4A is a circuit diagram, and FIG. 4B is an operation explanatory diagram thereof. E _1, E _2: first, second DC power supply R _1: charging resistor, C _1: the discharge resistance D _1, D _2: Diode T _1: the gate transformer Q _1: switching element Th _1, Th _2, ...... Thn: Thyristor

Claims (1)

[Claims] 1. A reset winding and a drive winding are connected in series on the primary side of a gate transformer, and a common end of both windings has a discharge capacitor whose one end is circuit-grounded. The other end of the reset winding is connected to the cathode of a diode whose anode is circuit-grounded, the other end of the drive winding is circuit-grounded via a switching element, and between the terminals of the capacitor. , A first DC power supply is connected via a charging resistor, and a second DC power supply having a voltage lower than that of the first DC power supply is connected via a forward diode. Gate drive device for thyristor.