JPH053229B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a snubber circuit for a self-arc-extinguishing thyristor, such as a gate turn-off thyristor or an electrostatic induction thyristor, which skillfully processes power in the self-arc-extinguishing thyristor. [Prior Art] Conventionally, gate turn-off thyristors (hereinafter referred to as GTO thyristors) have been commonly used as self-extinguishing thyristors, and electrostatic induction thyristors (hereinafter referred to as SI thyristors) are also known as a new type. ing. Similar to GTO thyristors, this SI thyristor can be turned off by applying a reverse bias voltage between the cathode and gate of the energized element. Regarding turn-on, there are normally-off types that require forward bias to be applied between the gate and cathode, similar to GTO thyristors.
There are two types of normally-on types that turn on simply by removing the reverse bias between the gate and cathode. All of them are characterized by extremely fast switching times, and together with the fact that they can easily be made to withstand high voltages, they are viewed as promising switching elements for high frequency and high power applications. Next, FIG. 1 shows a typical example of a DC switch circuit using a GTO thyristor or SI thyristor. In order to simplify the explanation, an example in which an SI thyristor is used as a self-extinguishing thyristor will be explained. Figure 1 shows an example of the configuration of a DC switch circuit using a normally-off type SI thyristor, where 1 is the SI thyristor, 2 is the main current, 3 is the load,
4 is a switch, 5 is a snubber capacitor, 6 is a snubber resistor, 7 is a snubber diode, and 8 is a gate circuit. The operation of the circuit configuration using such an SI thyristor is as follows. Further, in order to facilitate understanding of this effect, the states of waveforms at various parts in FIG. 1 are shown in FIGS. 2a and 2b. In the figure, T ₁ indicates the turn-on start point where SI thyristor 1 starts turning off, and T ₂ indicates the turn-off starting point where SI thyristor 1 starts turning off. represents. Now, in FIG. 1, the gate circuit 8
When a reverse bias voltage is applied between the gate and the cathode of the SI thyristor 1 and the switch 4 is closed, the main power supply 2 voltage is applied between the anode and the cathode of the SI thyristor 1 via the load 3, so that the snubber capacitor 5 is charged through the snubber diode 7 and becomes equal to the power supply voltage. Here, in order to turn off the SI thyristor 1, it is sufficient to supply a forward current from the gate circuit 8 to the gate of the SI thyristor 1, and when the SI thyristor 1 is turned on, the charge stored in the snubber capacitor 5 is transferred to the snubber resistor 6. is discharged through
The energy is consumed by the snubber resistor 6 and converted into heat. Further, in order to turn off the SI thyristor 1 while it is energized, a reverse current may be supplied from the gate circuit 8 to the gate of the SI thyristor 1. At this time,
The SI thyristor 1 is rapidly turned off, and the snubber capacitor 5 is charged to the power supply voltage via the snubber diode 7. [Problem to be Solved by the Invention] In this way, in the first circuit, the charge of the snubber capacitor 5 is repeatedly charged and discharged according to the on/off of the SI thyristor 1. The power P _C flowing in and out can be expressed by equation (1). P _C = C・E ²・f (1) where C is the capacity of the snubber capacitor 5, E is the voltage of the main power supply 2, and f is the operating frequency. In addition, since the snubber resistor 6 is energized only when the snubber capacitor 5 is discharging, the power consumed here is
P _R is half of the electric power P _C , and P _R = (1/2) C・E ²・f (2). Therefore, as the power P _R generated by the snubber resistor 6 increases, particularly when the voltage and frequency increase, the amount of heat generated increases rapidly, causing problems in heat treatment, and the power treatment of the snubber circuit becomes a major problem. was. In view of the above-mentioned points, the present invention provides a special snubber circuit for a self-extinguishing thyristor that can effectively reduce power loss in the snubber circuit. [Means for Solving the Problems] In order to improve such power loss, the present invention has the following configuration. That is, a first series circuit in which the cathode of the first diode is connected to the first capacitor is connected in parallel to a self-extinguishing thyristor so that the anodes are common, forming a snubber circuit, and connecting the cathode of the first diode to the first capacitor. One end of a second series circuit consisting of two reactors is connected to the anode of the self-extinguishing thyristor, and the other end is connected to the second series circuit consisting of two reactors.
and the anode of the second diode is connected to the first capacitor,
A first closed circuit including a first capacitor, a second diode, a second series circuit, a self-extinguishing thyristor, and a first capacitor;
The anode of the third diode is connected to the connection point between the series circuit of and the second diode, the cathode of the third diode is connected to the power supply side terminal of the first reactor, and the other end of the first reactor is Connect to the anode of the self-extinguishing thyristor to
The second closed circuit includes a series circuit, a third diode, a first reactor, and a second series circuit. [Operation] With the above-described solution, the electric charge of the first capacitor that is charged when the self-arc-extinguishing thyristor is turned off is transferred to the first capacitor that flows through the first closed circuit when the self-arc-extinguishing thyristor is turned on. The charge transferred to the second capacitor is transferred to the second capacitor by the discharge current of the capacitor, and the rise in the anode voltage of the self-turning thyristor that occurs when the self-turning thyristor turns off next time causes the charge transferred to the second capacitor to be transferred to the second capacitor. By discharging through the second closed circuit, power can be supplied to the first reactor, which is a load. [Embodiment] FIG. 3 is a circuit diagram showing the main part configuration of an example similar to FIG.
2 and 15 are reactors. In the figure, the same reference numerals as in FIG. 1 indicate the same components. Note that although the load is not shown in the figure, an application to an inductive load will be described here. next,
The function of this circuit will be explained in detail below when the SI thyristor 1 is turned on and turned off. Here, FIG. 4 is a time chart showing the states of waveforms of various parts at turn-on in FIG. 3 in the same way as FIG. 2. Now, in FIG. 3, when the switch 4 is closed while the reverse bias voltage of the SI thyristor 1 is applied by the gate circuit (not shown), the voltage of the main power supply 2 is E _S
is applied between the anode and cathode of the SI thyristor 1 via the reactor 15, and the capacitor 9 is further charged through the diode 10 to become equal to the voltage E _S. Here, if a forward current is supplied to the gate of the SI thyristor 1 by the gate circuit, the SI thyristor 1 is turned on. Therefore, the operation up to this point is no different from that of the snubber circuit shown in FIG. Then, when SI thyristor 1 turns on, the charge stored in capacitor 9 is transferred as follows: capacitor 9 → diode 11 → reactor 1
2 → capacitor 13 → SI thyristor 1 → capacitor 9 through the resonant circuit, the signal is transferred to capacitor 13. Such an effect is also clear from the waveform transition shown in FIG. Also, the charge transferred to the capacitor 13 charges its terminal voltage to the polarity shown in Figure 3, but since the SI thyristor 1 is on, the negative terminal potential of the capacitor 13 is 2
diode 14 is reverse biased. Therefore, the charge in the capacitor 13 is not discharged throughout the turn-on period of the SI thyristor 1, and the capacitor 13 remains charged. Furthermore, the above-mentioned turn-on operation will be explained with reference to FIG. 5, which is shown as an equivalent circuit of the snubber circuit section of FIG. 3. That is, in FIG. 5, parts having the same functions as those in FIG. 3 are given the same reference numerals, and 17 indicates a switch. Here, if the capacitance and charge of capacitor 9 and capacitor 13 are C ₁ , C ₂ and Q ₁ , Q ₂ respectively, and the inductance of reactor 12 is L, then the turn-on operation of SI thyristor 1 can be considered ignoring its loss. For example, this corresponds to closing the switch 17 by setting the initial value of the charge Q ₁ to Q _K. The circuit equation at this time can be shown as follows. (-1/C ₁ )・Q ₁ +L・(d ² /d)Q ₂ ² =0
………(3) Q ₁ + Q ₂ = Q _K ………(4) Therefore, since equations (3) and (4) are simultaneous equations regarding charges Q ₁ and Q ₂ , solving them yields the following It becomes like this. Q ₁ (t)＝Q _K [(C _P /C ₂ ) + {1−(C _P /C ₂ )} ・cos√{1/(L・C _P )}・t] ………(5) Q ₂ (t)=Q _K {1-(C _P /C ₂ )} ・[1-cos√{1/(L・C _P )}・t]
......(6) However, C _P = (C ₁・ C ₂ ) / (C ₁ + C ₂ ) Therefore, from formula (5), the charge Q ₁ of the capacitor 9
It can be seen that it oscillates periodically. Now, considering the charge Q ₁ after half a cycle has passed since the switch 17 was turned on, it is as shown in equation (7). cos√{1/(L・C _P )}・(T/2)=1
......(7) However, T=2〓√(L・C _P ) Substituting this equation (7) into equation (5), we get the following. Q ₁ (T/2) = Q _K {(C ₁ − C ₂ )/(C ₁ + C ₂ )} ………(8) Q ₂ (T/2) = Q _K {2C ₂ / (C ₁ + C ₂ )}
......(8') Here, if we choose (C ₁ = C ₂ ), the right-hand side of equation (8) becomes zero, and the right-hand side of equation (8') becomes Q _K. Therefore, all of the charge Q _K initially stored in capacitor 9 is transferred to capacitor 13. Also, when (C ₁ > C ₂ ), [Q ₁ (T/2)] becomes positive and the charge on the capacitor 9 has not been completely discharged, and when (C ₁ < C ₂ ), [Q ₁ (T/2)] becomes positive. T/2)] is negative and reverse biases the SI thyristor 1, which is obviously not desirable. Next, the operation at turn-off shown in FIG. 3 will be explained. Further, FIG. 6 is a time chart showing the states of waveforms of various parts at turn-off, similar to FIG. 4. Now, the current for SI thyristor 1 to turn off is
i _T becomes (i _T = 0), but the charging current of capacitor 9 follows the following path: main power supply 2 → reactor 15 → diode 10 →
It flows from capacitor 9 to main power supply 2, and the current i _CH does not become zero immediately. Further, as the potential of the capacitor 9 increases, the diode 14 becomes forward biased, so that the charge in the capacitor 13 is discharged through the following path. Capacitor 13 → Reactor 12 → Diode 14 → Reactor 15 → Capacitor 13 The current i _CH immediately after turn-off is a combination of the aforementioned charging current i _SC11 of the capacitor 9 and discharging current i _SC2 of the capacitor 13. The current ratio can be expressed as follows. (i _SC1 /C ₁ ) = (i _SC2 /C ₂ ) ......(9) Then, when the turn-off process progresses further and the capacitor 9 voltage becomes equal to the voltage E _S , the diode 16 becomes forward biased and freewheels. current
i _FW will start flowing. Therefore, since the voltage of capacitor 13 also becomes zero,
The charge accumulated in the capacitor 13 at the beginning of turn-off is discharged through the reactor 15. As described above, in the example shown in FIGS. 3 to 6, especially when the SI thyristor 1 is turned off, the charge stored in the first capacitor 9 is transferred to the second capacitor 13 by turning off the SI thyristor 1. When the SI thyristor is turned off next time, the power can be consumed by the load. In this example, it is possible to eliminate a component that generates heat as seen in the snubber resistor 6 shown in FIG. 1, and it is possible to suppress wasteful power consumption. Next, a modification of FIG. 3 is shown in FIG. 7.
In the figure, the same reference numerals as in FIG. 3 indicate the same components. That is, FIG. 7 shows an example in which the SI thyristor 1 is placed on the power supply side. In this configuration, the capacitor 13 must be placed on the cathode side of the SI thyristor 1 in order to discharge and consume the charge stored in the capacitor 13 to the load. [Effects of the Invention] As explained above, according to the present invention, a simple method for effectively processing the power stored in the snubber capacitor portion can be conveniently applied to high frequency or pulse width modulation type inverters. It is possible to provide a snubber circuit with extremely high practical value.

[Brief explanation of the drawing]

1 and 2 are circuit diagrams showing a configuration example of a DC switch circuit using a self-extinguishing thyristor, and time charts showing waveform states of each part thereof. FIG. 3 is an example of a snubber circuit according to the present invention. 4 is a time chart showing the state of the waveforms of each part at turn-off in FIG. 3; FIG. 5 is an equivalent circuit diagram showing the operation at turn-on in FIG. 3; FIG. 6 is a time chart showing the state of waveforms at various parts during turn-off in FIG. 3, and FIG. 7 is a circuit diagram showing a modification of FIG. 3. 1... Electrostatic induction thyristor (SI thyristor),
2... Main power supply, 3... Load, 9, 13... Capacitor, 10, 11, 14, 16... Diode,
12, 15...Reactor, _T1 ...Turn-on starting point, _T2 ...Turn-off starting point.

Claims (1)

[Claims] 1 A first series circuit in which the cathode of a first diode is connected to a first capacitor is connected in parallel to a self-extinguishing thyristor so that the anode is common,
One end of a second series circuit including a second capacitor and a second reactor is connected to the anode of the self-extinguishing thyristor, and the other end is connected to the cathode of the second diode. The anode of the third diode is connected to the first closed circuit connected to the first capacitor, and the anode of the third diode is connected to the connection point of the second series circuit and the second diode. A second closed circuit having a cathode connected to the power supply side terminal of the first reactor and the other end of the first reactor being connected to the anode of the self-extinguishing thyristor. A snubber circuit for a self-extinguishing thyristor.