JPS6037712B2 - gate control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gate control circuit for driving semiconductor-controlled rectifying elements used in semiconductor power conversion devices such as rectifiers, choppers, and inverters.

Semiconductor power control rectifying elements such as thyristors and transistors have been increasing in capacity in recent years, and elements that can switch on and off currents of several hundred amperes or more have been put into practical use and are widely used in power conversion devices such as choppers and inverters.

Semiconductor power control rectifier devices, such as thyristors and gate turn-off thyristors, have so-called Switching loss PA occurs. This switching loss PA becomes a considerably large value in a high voltage, large current element. In order to complete the mode transition period in which the switching loss PA occurs in a short time, it is essential to have a supply stand that provides sufficient control power.

Conventionally, various circuit systems have been devised to compensate for the lack of control power particularly during mode transition, and for example, a gate drive circuit as shown in FIG. 2a has been used.

The operation of the gate drive circuit shown in FIG. 2a will now be described. The gate drive circuit uses two types of power supplies E, E2 (however, E,
>E2), and series resistance R,, R2 (where R, >
R2) and the capacitor C via the diodes D, , D2
It is connected to the. Since the voltage of the power supply positive is higher than that of the power supply E2, the capacitor C is charged to E when the transistor S is in the off state. When the transistor S becomes conductive, the charge on the capacitor C starts discharging through the pulse transformer T.

Since the resistance R, is set to a sufficiently large value, the power supply E
, the supply current from the capacitor C is sufficiently small compared to the discharge current of the capacitor C. When the terminal voltage of the capacitor C becomes equal to E2, the pulse transformer current cT is supplied from the power source 2, and the current continues to flow as long as the transistor S remains conductive. With this gate circuit, as shown in Figure 2b, sufficient gate power can be obtained during periods when sufficient gate power is required, such as when the device turns on, and it is also sufficient during periods when large gate power is not required. power can be obtained. However, these gate control circuits have E,
, E2 is required. Particularly in uninterruptible power supply systems and auxiliary power supplies for railway vehicles, the control DC power source is limited to one type of power source obtained from a storage battery, so if two types of power sources are required, as shown in Figure 3. Therefore, a power conversion device such as a DC/DC converter must be separately provided to obtain the second power supply voltage, which causes a decrease in reliability and increases the cost of the device. SUMMARY OF THE INVENTION An object of the present invention has been made in view of the above-mentioned points, and it is an object of the present invention to provide a gate control circuit with improved reliability and reduced cost.

The present invention will be explained below with reference to the circuit shown in FIG. 4, which shows one embodiment.

In FIG. 4, E is a DC power supply, and a series circuit consisting of a diode D, a resistor R, and a capacitor C, and a series circuit consisting of a diode D2, a DC reactor L, and a transistor S are connected between the DC power supply terminals. Further, a diode D3 of the polarity shown is connected to the connection point between the DC reactor L and the transistor S, and the connection point between the resistor R and the capacitor C, and the primary winding of the pulse transformer T is connected in parallel to this diode D3. A pulse derived from the secondary winding of the pulse transformer T is applied to the gate circuit of the semiconductor element SCR. In FIG. 4 configured as described above, assuming that the capacitor C is charged to Ec,
Due to the conduction of the transistor S, the charge in the capacitor C is discharged through the pulse transformer T.

Discharging continues until the voltage on capacitor C becomes equal to power supply voltage E, after which diode D. becomes conductive, and a current flows through the pulse transformer T from the power source E. Here the resistor R,
acts as a current limiting resistance for the crab flow 'T of the pulse transformer. On the other hand, when the transistor S becomes conductive, the current flowing through the DC reactor L starts flowing from the power source E and increases with time as shown in FIG.
When the transistor S is turned off, the current flowing through the pulse transformer T, that is, the current due to the energy stored in the leakage reactance of the pulse transformer T, circulates through the diode D3 and rapidly decreases to zero. on the other hand,
The current LL flowing through the DC reactor L is the diode D3.
The capacitor C is charged through the capacitor C and the voltage of the capacitor C is increased. The voltage Ec charged to the capacitor C is
Since it is determined by the peak current flowing through the DC IJ factor L, the conduction period of the transistor S must be constant in order to always keep the charging voltage of the capacitor C constant. In the case of FIG. 4, if the conduction period of the transistor S is t [seconds], the following relationship holds true. Assuming that the peak value of the current flowing through the DC reactor L is lp, approximately the following relationship holds true.・p=Hayabusa t The energy stored in L is U=Kyo LIP2=Gei L (Hataket)2=Kyo Eki2 This energy transfers to capacitor C, so if the overcharge voltage is V, then U=YoV Side V2 = Western. ．． ．． v: Has a nasal voice.

By the way, since the terminal voltage of the capacitor C is maintained at the power supply voltage E until immediately before overcharging of the capacitor C starts, the voltage Ec after charging is completed has the following relationship.

EC=HV=E+younger brother The above explanation took as an example a gate circuit that provides an ON signal for a general thyristor, but the present invention is effective as an OFF gate drive circuit for a gate turn-off thyristor that requires a large amount of power as gate control power. can make the most of it.

Figure 6 shows the OFF state of the gate turn-off thyristor GTO.
The configuration when used as a gate drive circuit OFF○ is shown. Of course, if the switching element is a semiconductor element with a self-extinguishing function, it can be a gate turn-off thyristor GT.
The material is not limited to O, and may be a transistor, for example. Of course, it is also possible to connect directly to the gate circuit without using the gate transformer T. As described above, the present invention does not require an auxiliary power supply, provides sufficient power during switching mode transition with a single gate power supply, and can provide a high-performance gate control circuit without unnecessary power loss. .

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the loss that occurs during mode transition of a semiconductor element, Fig. 2 a is a diagram of a subordinate gate control circuit, Fig. 2 b is an explanatory diagram of its operation, and Fig. 3 is a conventional gate circuit. FIG. 4 is a circuit diagram showing an embodiment of the present invention,
FIG. 5 is an explanatory diagram of the operation of FIG. 4, and FIG. 6 is a configuration diagram when the present invention is used as an OFF gate circuit of a gate turn-off thyristor. D, ~D3...Diode, SCR...
・Thyristor, T...Pulse transformer, L...
...DC reactor, S...transistor, C...
Capacitor, R. ······Resistor. Figure 1 Figure 3 Figure 2 Figure 4. Figure 5 Figure 6

Claims (1)

[Claims] 1 DC power supply and the first terminal connected between this DC power supply terminal.
a first series circuit consisting of a diode and a capacitor; a second series circuit consisting of a second diode, a DC reactor, and a switching element; and a connection point between the first diode and the capacitor and the DC reactor and switching element. A gate control circuit comprising a third diode provided between the connection point and the third diode, and both terminals of the third diode are connected to a gate transformer or a gate terminal of a semiconductor element.