JPH0815393B2 - AC switching circuit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an alternating current switching circuit that switches alternating current supplied to a load at a speed higher than that of an alternating current power supply to change its conduction ratio.

(Background of the Invention) A load, a main switching circuit, and an AC power supply are connected in series to form a main circuit, while a flywheel switching circuit is connected in parallel to the load, and these main switching circuit and flywheel switching are performed. An AC switching circuit has been considered in which the circuit is alternately switched at a frequency higher than that of the AC power supply.

FIG. 8 is a diagram showing a conventional circuit of this type. In the circuit of FIG. 8A, a closed main circuit is formed by a load 1, a main switching circuit 2 and an AC power supply 3, while a load 1 is formed. A flywheel switching circuit 4 is connected in parallel with the. Here, the main switching circuit 2 and the flywheel switching circuit 4 are formed by a bridge composed of a diode D and a transistor TR. Further, in the circuit of FIG. 3B, the main switching circuit 2A and the flywheel circuit 4A are formed by connecting a series circuit of a diode D and a transistor TR in antiparallel.

In the case of such a conventional switching circuit 2,2A, 4,4A, since the potentials of the transistor TR used in the main switching circuit 2,2A and the flywheel switching circuit are different, that is, the voltage for controlling the transistor TR Since the reference potentials are different, there is a problem that the control circuit for controlling each of these transistors TR becomes complicated.

(Object of the Invention) The present invention has been made in view of such circumstances,
An object of the present invention is to provide an AC switching circuit in which a control circuit for a main switching circuit and a switching circuit for a flywheel can be constructed very easily.

(Structure of the Invention) According to the present invention, the object is to connect a load, a main switching circuit, and an AC power supply in series to form a main circuit, while connecting a flywheel switching circuit in parallel to the load, In the AC switching circuit, wherein the main switching circuit and the flywheel switching circuit are alternately switched at a frequency higher than the AC power supply, the main switching circuit and the flywheel switching circuit have one end of a semiconductor switching element as an external reference potential. It is formed by an AC 3-terminal high-speed switching circuit serving as a side terminal, the reference potential side terminals of each AC 3-terminal high-speed switching circuit are connected to each other, and a control signal having a frequency higher than that of the AC power supply and its inverted signal are supplied to each AC. Connect to each external control terminal of 3-terminal high-speed switching circuit AC switching circuit characterized by being continued.

Here, the AC three-terminal high-speed switching circuit has two sets of reverse conducting semiconductor switching elements whose input terminals are connected to each other, and a control input from an external control terminal using the output terminal of one of the reverse conducting semiconductor switching elements as a reference potential. A control unit for turning on both of the two sets of reverse conducting semiconductor switching elements by a signal, and connecting the respective output terminals of the two sets of reverse conducting semiconductor switching elements to the main circuit.

The AC three-terminal high-speed switching circuit is connected to the main circuit and is connected in anti-parallel between two terminals to which an AC voltage is applied, and includes two sets of series circuits each including a diode and a reverse blocking transistor, and the external input / output. It can be configured by including a control unit that turns on or off both of the two reverse blocking transistors based on a control signal input from an external control terminal with one of the terminals as a reference potential.

Further, the AC three-terminal high-speed switching circuit includes a diode and a reverse blocking transistor connected in series between two external input / output terminals connected to the main circuit and to which an AC voltage is applied, a base of the reverse blocking transistor, and one terminal. And a control transistor interposed between and, and the base of the reverse blocking transistor is connected to the other terminal of the reference potential.

(Embodiment) FIG. 1 is a circuit diagram showing an embodiment of the present invention. In this figure, the main switching circuit A and the flywheel switching circuit B are composed of AC 3-terminal high-speed switching circuits, and terminals b on the reference potential side thereof are connected to each other. C is a control circuit, which sends a control signal of a predetermined potential to the external control terminal c of the main switching circuit A on the basis of the potential of the external input / output terminal b on the reference potential side, while the control signal is reversed by the NOT circuit D. It is converted into a logic signal and input to the external control terminal c of the flywheel switching circuit B. As a result, the control circuit C outputs the control signal which is turned on / off at a frequency higher than that of the AC power supply 3 with the external input / output terminal c as a reference, and the two switching circuits A and B are turned on / off alternately. To be done. Therefore, the configuration of the control circuit C becomes very simple.

Next, the configuration of the AC 3-terminal high-speed switching circuit will be described.

 FIG. 2 is a circuit diagram of the first embodiment.

In this figure, reference numerals 10 and 12 are N-channel depletion MOS type field effect transistors (hereinafter referred to as FETs) as reverse conducting semiconductor switching elements. The reverse conducting semiconductor switching elements 10 and 12 are provided with drains D and D which are input terminals for inputting current, sources S and S which are output terminals, and gates G and G which are control terminals for controlling current. The FETs 10 and 12 are respectively provided with reverse conducting diodes 10a and 12a on the same semiconductor chip in advance. The drains D and D that are the input ends of these FETs 10 and 12 are connected to each other, and the sources S and S that are the output ends are connected to terminals a and b, respectively.

Reference numeral 13 is a control unit, and a resistor 14 interposed between a gate G which is a control end of the FET 10 and a source S which is an output end thereof,
A PNP transistor 16 as a control semiconductor switching element connected between the gates G and G of both FETs 10 and 12. The emitter of the transistor 16 is directly connected to G of the FET 12, and its collector is connected to the FE via the resistor 18 and the diode 20.
Each is connected to the gate G of T10. The gate of the transistor 16 is connected to the terminal b via the resistor 22. The terminal b serves as the reference potential of the control signal input to the external control terminal c. The terminal b serving as the reference potential and the external control input terminal c are connected by the resistor 24.

Next, the operation of this embodiment will be described. First, the positive half cycle of the AC power supply in which the terminal a is positive with respect to the terminal b will be described. At this time, if the control signal of the external control terminal c is substantially equal to or negative to the potential (reference potential) of the terminal b, the FET 12 is turned off and no current flows from the terminal a to the terminal b. That is, this switching circuit is turned off. If the control signal becomes high potential with respect to the terminal b, the FET 12
The gate-source voltage V _GS becomes positive and FET12 turns on. Therefore, a current flows from the terminal a to the terminal b through the diode 10a and the drain / source of the FET 12. That is, the switching circuit is turned on. Thus, in the positive half cycle of the power supply, the switching circuit is turned on / off as the potential of the control signal changes to high / low potential with the terminal b as a reference.

Next, the operation in the negative half cycle in which the terminal a has a lower potential than the terminal b will be described. At this time, if the control signal becomes substantially the same potential or a negative potential with respect to the terminal b, the FET 12 is turned off and the control transistor 16 is also turned off.
Current does not flow to the gate, the gate voltage of FET10 becomes low and FET10
Turns off. Therefore, the switching circuit is turned off.
When the control signal has a high potential with respect to the terminal b, the FET 12 is turned on, and at the same time, the control transistor 16 is also turned on and a current flows through the resistor 14 in the direction of the terminal a. For this reason FET10
Is also turned on. Therefore, the current from terminal b
12a or FET12 and FET10 and flows to the terminal a. That is, the switching circuit is turned on. In this way, in the negative half cycle of the power supply, the switching circuit is turned on / off as the potential of the control signal changes to high / low potential with reference to the terminal b.

Figure 3 is a characteristic diagram of the switching circuit, V _{ab
Represents the} voltage between terminals a and b, V _cb represents the voltage between terminals c and b, and I represents the current flowing between terminals a and b.

FIG. 4 is a circuit diagram of the second embodiment. Since the FETs 10A and 12A in this embodiment do not have a reverse conducting diode built therein, a switching element capable of reverse conducting by connecting separate diodes 30 and 32 in parallel. FET10A (12A) and diode 30 (3
2) Formed by and. Also, a P-channel depletion FET1 is used as a semiconductor switching element of the control unit 13A.
I am using 6A.

The embodiment shown in FIG. 5 is a circuit diagram of the third embodiment. This embodiment uses the FETs 10A and 12A shown in FIG.
0B and 12B, and the switching element of the control unit 13B is the PNP transistor 16.

Since other configurations and operations in the embodiment shown in FIGS. 4 and 5 are the same as those in the embodiment shown in FIG. 2, the same parts are designated by the same reference numerals and the description thereof will not be repeated.

FIG. 6 is a circuit diagram of still another embodiment of the AC 3-terminal high-speed switching circuit. In this figure, reference numerals 100 and 200 are series circuits composed of diodes 120 and 220 and NPN transistors 140 and 240, respectively. These series circuits 100 and 200 are connected in antiparallel between the terminals a and b. An alternating current is input to the terminals a and b from the outside. The terminal b is set to the reference potential.

A control unit 300 is a transistor connected to a terminal a on the side opposite the reference potential and a direction in which a current flows toward the terminal a.
A resistor 320 interposed between the base of 240 and a control PNP transistor interposed between the bases of both transistors 140 and 240.
340 and. The emitter of the transistor 340 is directly connected to the base of the transistor 140, and the collector is connected to the base of the transistor 240 via the resistor 360 and the diode 380. Also control transistor 340
The base of is connected to a terminal b on the reference potential side via a resistor 400. A control signal supplied from an external control circuit (not shown) is led from the external control terminal c to the base of the transistor 140.

Next, the operation of this embodiment will be described. First, a positive half cycle in which the AC voltage input between the terminals a and b increases on the terminal a side will be described. At this time, if the control signal is substantially equal to or lower than the reference potential of the terminal b, the transistor 140 is turned off,
Therefore, no current flows from the terminal a to the terminal b. That is, this switching circuit is turned off. When the control signal has a high potential, the transistor 140 is turned on. That is, the switching circuit is turned on. In this way, in the positive half cycle, the transistor 140
Turns on and off.

When the control signal has a low potential in the negative half cycle of the alternating current, the control transistor 340 is turned off and therefore the transistor 240 is also turned off, so that no current flows from the terminal b to the terminal a. When the control signal has a higher potential than the reference potential of the terminal b, the control transistor 340 is turned on. Therefore, a current flows from the external control terminal c through the control transistor 340, the resistor 360, the diode 380 and the resistor 320 to the terminal a. Therefore, the transistor 240 is turned on, and a current flows from the terminal b through the diode 220 and the transistor 240 to the terminal a.
Flows to That is, the switching circuit is turned on / off in response to the change of the control signal to the high or low potential.

FIG. 7 is a circuit diagram of still another embodiment. In this embodiment, one of the series circuits 200 in the embodiment of FIG. 6 is omitted, and corresponding parts are designated by the same reference numerals.

In this embodiment, in the positive half cycle of the alternating current input to the terminals a and b, the current from the terminal a is supplied to the diode 120 and the transistor 140 only when the control signal is at a high potential, just as in the case of FIG. Through to the terminal b.

In the negative half cycle of the alternating current input to the terminals a and b, when the control signal has substantially the same potential as the terminal b, the control transistor 34
Although 0 is off, when the control signal changes to a high potential, the control transistor 340 is turned on, and a considerably large base current flows from the terminal b to the terminal a. That is, this embodiment uses the base current of the control transistor 340 to perform the negative half cycle switching of the AC voltage.

(Effects of the Invention) As described above, the present invention uses the AC 3-terminal high-speed switching circuit for the main switching circuit of the AC circuit and the flywheel switching circuit, and connects the reference potential side of each switching circuit to each other. From
The effect is that the control circuit becomes very simple.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention, and FIGS. 2 and 4 to 7 are circuit diagrams of an embodiment of an AC 3-terminal high-speed switching circuit.
FIG. 8 is a characteristic diagram of an AC 3-terminal high-speed switching circuit, and FIG. 8 is a circuit diagram of a conventional AC switching circuit. 1 ... Load, 3 ... AC power supply, A ... Main switching circuit, B ... Flywheel switching circuit.

Claims (6)

[Claims] 1. A load, a main switching circuit, and an AC power supply are connected in series to form a main circuit, and a flywheel switching circuit is connected in parallel to the load, and the main switching circuit and flywheel switching are performed. In an AC switching circuit in which circuits are alternately switched at a frequency higher than the AC power supply, the main switching circuit and the flywheel switching circuit are AC 3-terminal high-speed switching in which one end of a semiconductor switching element is an external reference potential side terminal. Circuit, the terminals on the reference potential side of each AC three-terminal high-speed switching circuit are connected to each other, and a control signal having a frequency higher than that of the AC power supply and its inverted signal are external control terminals of each AC three-terminal high-speed switching circuit. Are each connected to AC switching circuit. 2. An AC three-terminal high-speed switching circuit, wherein two sets of reverse conducting semiconductor switching elements whose input terminals are connected to each other and one output terminal of the reverse conducting semiconductor switching element are input as reference potentials from an external control terminal. A control unit for turning on both of the two sets of reverse conducting semiconductor switching elements in response to the control signal. Each output terminal of the two sets of reverse conducting semiconductor switching elements is connected to the main circuit. The AC switching circuit according to claim 1. 3. The AC switching circuit according to claim 2, wherein the reverse conducting semiconductor switching element is formed of a transistor and a diode connected in parallel to the transistor. 4. The AC switching circuit according to claim 3, wherein the transistor is a field effect transistor. 5. An AC three-terminal high-speed switching circuit includes two sets of series circuits each connected to a main circuit and connected in antiparallel between two terminals to which an AC voltage is applied, each series circuit including a diode and a reverse blocking transistor. The control unit that turns on or off both of the two reverse blocking transistors based on a control signal input from an external control terminal using one of the terminals as a reference potential. AC switching circuit described. 6. An AC three-terminal high-speed switching circuit includes a diode and a reverse blocking transistor connected in series between two terminals connected to a main circuit and receiving an AC voltage.
A control transistor provided between the base of the reverse blocking transistor and one terminal thereof, wherein the base of the reverse blocking transistor is connected to the other terminal having a reference potential. The AC switching circuit according to item 1.