JPH0564025B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a switching circuit that performs power transfer, and particularly to a power supply circuit that aims to reduce switching loss of a gate turn-off thyristor.

[Technical background of the invention and its problems]

Recently, inverters and DC-DC converters using switching circuits have been widely used as power supply devices for various electronic devices and power devices. In order to improve the power transfer efficiency and reduce the size of the switching circuit, the operating frequency of the switching circuit is being increased to a higher frequency. Conventionally, however, a gate turn-off thyristor (GTO) has generally been used as a switching element in this type of power supply circuit. The upper limit of the switching operating frequency when using this GTO is
It is determined by the accumulation time of the GTO, the existence time of the tail current that flows after its turn-off, and the heat dissipation capacity of the GTO, etc., and it is determined by the GTO's accumulation time, the existence time of the tail current that flows after its turn-off, and the heat dissipation ability of the GTO. It is about 1KHz.

Figure 1 shows a conventional voltage resonance type power supply circuit configured using GTO1 as a switching element, 2 is a DC power supply, and 3 is the first one.
A transformer whose secondary winding is connected to the DC power supply 2 via the GTO 1 and a load circuit 4 connected to the secondary winding; 6 is a power regeneration diode connected in parallel to the resonance capacitor 5. Further, numeral 7 in the figure is a control unit that controls opening and closing of the GTO 1 at a predetermined cycle and with a predetermined conduction width.

In the circuit configured in this way, time t=
When a gate signal is added to the GTO gate at t ₀ , the second
As shown in Figure a, the anode current Ia begins to flow rapidly through the GTO 1 and reaches a constant value Ipk. after that,
The time required for the above GTO1 to turn off is τon
Then, the potential difference Va between the anode and cathode of GTO1 during this period is its saturation voltage
It is kept at Vsat. When a turn-off pulse is applied to GTO1, the anode current flowing through GTO1 starts to be cut off. Assuming that the time required for this turn-off is τ ₁ , the anode-cathode voltage Va rises sharply during this period τ ₁ . Then, at the elapse of the above period τ ₁ , the anode current Ia of GTO 1 becomes zero, and after that, the initial current I ₀ of GTO 1 becomes a tail current of about 1/6 to 1/10 of the anode current (Ipk) at the time of interruption. , flows over time τ ₂ . This tail current It is generated when the current stored in the GTO 1 flows out, and is a phenomenon unique to GTOs. During this period τ ₂ , the anode voltage Va rises while drawing a large sinusoidal arc,
Returns to zero (0) again. Such operations are repeated to transfer power.

By the way, if you perform a switching operation like this
The switching loss Ploss of GTO1 is determined by the anode current Ia and the anode voltage as shown in Figure 2b.
It is expressed by the product with Va. Therefore, the loss during the turn-on period τon is Q ₁ , the loss during the turn-off period τ ₁ is Q ₂ , the loss during the period τ ₂ during which the tail current is flowing is Q ₃ , and from the tail current extinction, the following Assuming that the period until the start of turn-on is τ ₃ , the average loss Ploss is Ploss=(Q ₁ +Q ₂ +Q ₃ )/T. However, T=τon+τ ₁ +τ ₂ +τ ₃ . However, the switching operation of GTO1
When the frequency is 500Hz or less, the ratio of the period τ ₃ to one period T is about 1/2 (0), and τ ₂ is 1/20,
τ ₁ is about 1/100, and τon is about 1/2. Therefore, GTO1
The switching loss Ploss is dominated by (Q ₁ +Q ₂ ). However, when the switching frequency exceeds 5KHz, the ratio of τ ₃ to the period T becomes approximately 1/20,
Since τ ₂ is 7/15, τ ₁ is 1/50, and τon is about 1/2,
In the end, Q ₃ becomes dominant. In other words, when operating at a high frequency of 5 KHz or higher, there is a problem in that the loss due to the tail current increases rapidly.

[Purpose of the invention]

The present invention was made in consideration of these circumstances, and its purpose is to easily increase the frequency of the switching operation of the gate turn-off thyristor responsible for power transfer, and to reduce the tail current of the gate turn-off thyristor. An object of the present invention is to provide a simple and highly practical power supply circuit that can significantly reduce losses caused by .

[Summary of the invention]

In parallel with a gate turn-off thyristor driven by switching, the present invention provides means for passing a reverse current through the gate turn-off thyristor when a tail current flows through the gate turn-off thyristor. The feature is that a flow circuit is provided. In other words, the commutation circuit causes a reverse current to flow through the gate turn-off thyristor, and this reverse current causes the gate turn-off thyristor to pass through the gate turn-off thyristor.
This is designed to cancel the tail current of the off-thyristor.

And, this commutation circuit has the gate turn
A series circuit of a commutating capacitor and a coil connected in parallel to the off thyristor, and a series circuit connected to this series circuit and turned on when the gate turn-off thyristor is turned on to fill the commutating capacitor. A first switch element is connected to the series circuit, is turned on when the gate turn-off thyristor is turned off, and transfers the charge stored in the commutation capacitor to the gate turn-off thyristor. and a second switching element that causes the reverse current to flow.

〔Effect of the invention〕

Thus, according to the invention, when a tail current flows through the gate turn-off thyristor, a reverse current flows into the gate turn-off thyristor from a commutating circuit connected in parallel to the gate turn-off thyristor. , so that the tail current can be effectively canceled, and therefore, the switching loss of the gate turn-off thyristor caused by the tail current can be significantly suppressed. As a result, great practical effects can be achieved, such as the ability to easily increase the switching operating frequency of the gate turn-off thyristor without increasing loss. Furthermore, the commutation circuit in the present invention has gate turn-off,
Since the commutating capacitor is charged via the first switch element provided separately from the thyristor, a power source with a polarity opposite to the main DC power source is not required to charge the commutating capacitor.

Furthermore, when the commutation capacitor charging current flows through the gate turn-off thyristor, the gate turn-off thyristor flows through the primary winding of the transformer.
Since the current flowing through the thyristor decreases by that amount, there is a problem that the power supplied to the load circuit decreases, but in the present invention, since the charging current of the commutation capacitor does not flow to the gate turn-off thyristor, Such problems are solved.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 3 is a basic configuration diagram of the power supply circuit according to the embodiment. The same parts as those of the conventional circuit shown in FIG. 1 will be described with the same reference numerals.

The feature of the embodiment circuit is that a commutation circuit 8 is provided in parallel to the GTO 1 that directly controls power transfer. This commutation circuit 8 causes a reverse current to flow through the GTO 1 when the GTO 1 is turned off and a tail current flows due to the turn off. Furthermore, GTO1 is turned on when a gate signal is applied at a predetermined switching period, for example, a period of 5KHz or more, and is turned on at a predetermined switching period.
It is turned off (cut off) after the on time τon has elapsed.

As shown in FIG. 4, the commutation circuit 8 is composed of a capacitor 11 and a coil 12 connected in series, and two thyristors 13 and 14 connected to this series circuit and their control units 15 and 16. Become. The two thyristors 14 and 15 are connected in antiparallel to each other. For example, as shown in FIG. 5, for the on/off timing a of GTO1, the thyristor 14 is activated at the timing shown in FIG. The thyristors 13 are each turned on at the timing shown in FIG.

According to the power supply circuit configured in this manner, the GTO1
When the tail current is about to flow after the GTO1 is cut off, a reverse current is passed from the commutation circuit 8 connected in parallel to the GTO1 to the GTO1.
The tail current flows will be canceled out. As a result, the tail current of the GTO 1 is substantially suppressed, making it possible to reduce the loss caused by this tail current.

That is, when GTO1 is turned on at time t= _t0 , thyristor 13 is turned on at the same time.
turned on. As a result, the charge in the capacitor 11 flows through the GTO 1 and the thyristor 13, and the capacitor 11 is charged to a potential opposite to the polarity shown. Thereafter, due to the resonance effect of the capacitor 11 and the coil 12, the current flowing therein attempts to reverse, but the thyristor 13 is reverse biased and turned off, so that the current flow is blocked. At this time, the anode current flowing through the GTO1 reaches Ipk, and the potential difference between both ends of the GTO1 is maintained at its saturation voltage Vsat. After that, GTO
When GTO1 turns off, current still tries to flow through GTO1 despite this turn-off. This current is the tail current. However, at the same time as this GTO1 turns off, the commutation circuit 8
Since the thyristor 14 is turned on, the charge stored in the capacitor 11 flows in the opposite direction via the thyristor 14 and the GTO1.
This reverse current has a direction opposite to the tail current flowing through the GTO1, and ultimately reduces the tail current flowing through the GTO1. And the tail current disappears (zero)
However, when the GTO 1 is completely cut off, the current in the capacitor 11 flows through the coil 12 and the diode 6, and the current supplied from the DC power supply 2 through the transformer 3 causes the capacitor 11 to Charged to the polarity shown. When the current is reversed due to the resonance effect of the capacitor 11 and the coil 12, the thyristor 14 is biased in the opposite direction and turned off.
The current flowing through the thyristor 14 and diode 6 is cut off. Further, the current from the DC power supply 2 is cut off by the diode 6.
The above operations are repeated, and power is transferred to the load circuit 4 by the switching of the GTO 1 and the voltage resonance action of the resonance capacitor 5.

According to the power supply circuit configured as described above, the tail current of the GTO 1 can be effectively reduced by the commutation circuit 8. Therefore, the turn
Even if the losses Q 1 and _{Q 2 in} the on-period τon and turn-off period τ ₁ are the same, the loss Q ₃ in the tail current period τ ₂ can be significantly reduced, and the average loss Ploss can be reduced in the end. becomes possible. Therefore, even if the switching operation frequency of GTO 1 is set high to reduce the size of the device, the power transfer efficiency will not be reduced. The maximum current flowing through the thyristors 13 and 14 is 10 times their breaking capacity.
Since the anode current Ia of GTO1 is more than double
It is sufficient to use one with a small capacity that can cut off the Therefore, instead of the thyristors 13 and 14, the commutation circuit 8 can be constructed using other switching elements such as transistors and FETs. Furthermore, it is of course possible to configure the commutation circuit 8 as shown in FIG.

As described above, according to the present invention, the tail current of the GTO 1 that controls power transfer can be significantly suppressed, and the loss can be reduced. In addition, since it is possible to increase the frequency of the switching operation while suppressing loss in this way, when using the same GTO1 as the conventional circuit, the operating frequency can be increased by more than 10 times compared to the conventional circuit. Concerning vessel 3, it is possible to make it smaller and lighter by 1/20 in volume and 1/10 in weight. In addition, tremendous effects such as the ability to downsize and reduce the capacity of the heat radiator necessary for cooling this circuit can be obtained.

It goes without saying that the present invention is not limited to the embodiments described above, and can be implemented with various modifications without departing from the spirit thereof.

[Brief explanation of the drawing]

FIG. 1 is a basic configuration diagram of a conventional power supply circuit, FIG. 2 is a waveform diagram for explaining problems in the conventional circuit, and FIG. 3 is a schematic configuration diagram showing an embodiment of the present invention. FIG. 4 is a diagram showing a configuration example of a commutation circuit in the same embodiment, FIG. 5 is a diagram showing switching operation timing of the GTO and thyristor in the same embodiment, and FIG. 6 is a waveform diagram showing the operation of the same embodiment. FIG. 7 is a configuration diagram showing another embodiment of the present invention. 1...GTO (gate turn off thyristor), 2...DC power supply, 3...Transformer, 4...Load circuit, 5...Resonance capacitor, 6...Power regeneration diode, 7... Control unit, 8... Commutation circuit, 11... Capacitor, 12... Coil, 1
3,14...thyristor.

Claims (1)

[Scope of Claims] 1. A DC power supply, a transformer having a secondary winding connected to a load circuit, and a transformer connected to the DC power supply via the primary winding of the transformer, at a predetermined period and at a predetermined time. a gate turn-off thyristor that is controlled to open and close with a conduction width of a resonant capacitor that resonates between the resonant capacitor; a diode for power regeneration connected in parallel to the resonant capacitor; and a power regeneration diode connected in parallel to the resonant capacitor; and a commutation circuit that flows a reverse current through the gate turn-off circuit.
a series circuit of a commutating capacitor and a coil connected in parallel to the thyristor; and a first circuit connected to the series circuit, which is turned on when the gate turn-off thyristor is turned on and charges the commutating capacitor. a switch element connected to the series circuit and the gate turn-off switch element connected to the series circuit;
a second switch element that is turned on when the thyristor is turned off and causes the charge stored in the commutation capacitor to flow as the reverse current to the gate turn-off thyristor. .