JPH078148B2 - Bridge inverter circuit - Google Patents

Description

The present invention relates to a bridge inverter circuit for outputting an AC voltage from a DC power supply by alternately conducting bridge-connected semiconductor switches.

[Conventional technology]

FIG. 4 shows a basic circuit of the bridge inverter circuit. In FIG. 4, (1) is a first semiconductor switch, (2) is a second semiconductor switch, and (3) is a third semiconductor switch.
(4) is a fourth semiconductor switch, which is composed of a transistor. (5) is a DC power supply of 100V to 200V, and (6) is a load. The first semiconductor switch (1) and the second semiconductor switch (2) are connected to the negative side of the DC power supply (5), and the third semiconductor switch (3) and the fourth semiconductor switch (4) are connected to the DC power supply (5). It is connected to the plus side.

In this inverter circuit, semiconductor switches (1) (2)
(3) and (4) are turned on and off to apply an AC voltage to the load (6). In this case, since the emitters of the first and second semiconductor switches (1) and (2) are connected to the negative terminal of the power source (5), the semiconductor switches (7) and (8) should be provided as shown in FIG. Thus, the first and second semiconductor switches (1) and (2) can be turned on and off, but it is difficult to turn on and off the third and fourth semiconductor switches (3) and (4) by the power supply (5). Therefore, as shown in FIG. 6, a drive power source (9) (10) is usually provided separately (a separate power source of about 10 V is also used for driving the first and second semiconductor switches (1) and (2)). Often provided.). Also, semiconductor switches for driving (7) (8)
The power supply for the control circuit (13) that turns on (11) and (12) is often obtained from the DC power supply (14). A signal for turning on and off the semiconductor switches (7) and (8) can be easily obtained by the circuit configuration shown in FIG. 7 because one end of the power supplies (5) and (14) is connected. In order to turn the semiconductor switches (3) and (4) on and off, the power supply (14) of the control circuit (13) and the power supplies (9) and (10) are not directly connected, so the conventional photo coupler (15) and It was turned on and off with insulation using a transformer or the like.

[Problems to be solved by the invention]

Therefore, conventionally, a photo coupler or the like is required, the circuit configuration is very complicated, and the manufacturing cost is high.

In view of the above problems, the present invention has a simple circuit configuration without using a photocoupler, a transformer, etc., and is capable of reliably turning on and off the positive side semiconductor switch in correspondence with the negative side semiconductor switch. is there.

[Means for solving problems]

The technical means of the present invention for solving this technical problem is to provide negative side first and second semiconductor switches (1) and (2) and positive side third and fourth semiconductors which are bridge-connected to a DC power source (5). A switch (3) (4) and a first and a fourth
The alternating conduction between the semiconductor switches (1) (4) and the second and third semiconductor switches (2) (3) causes the connection points of the first and third semiconductor switches (1) (3) and the second and fourth semiconductor switches. In a bridge inverter circuit that outputs an AC voltage between the connection points of the semiconductor switches (2) and (4),
The first, second, third and fourth semiconductor switches 1, 2, 3, 4
Are respectively composed of NPN transistors, and DC power sources 18 and 19 for supplying a base current are respectively connected to the bases of the third and fourth semiconductor switches 3 and 4 via resistors 20 and 21, respectively.
A diode 22 for flowing a current from the DC power supply 18 to the first semiconductor switch 1 so as to block a base current to the third semiconductor switch 3 when the semiconductor switch 1 is turned on, and a fourth semiconductor switch when the second semiconductor switch 2 is turned on. A diode 23 for supplying a current from the DC power supply 19 to the second semiconductor switch 2 so as to block the base current to the fourth semiconductor switch 4, the base side of the third and fourth semiconductor switches 3 and 4, and the first and second semiconductor switches. The first semiconductor switch 1 and the second semiconductor switch 4 are connected between the first semiconductor switch 1 and the second semiconductor switch 2, respectively, so that the third semiconductor switch 3 and the fourth semiconductor switch 4 are turned on and off by driving the first semiconductor switch 1 and the second semiconductor switch 2. The point is that a control circuit for alternately conducting the semiconductor switches 2 is provided.

〔Example〕

The present invention will be described below with reference to the illustrated embodiment.
In the figure, (18) and (19) are direct current power supplies of about 10 V for driving, which are connected to the bases of the third and fourth semiconductor switches (3) and (4) via resistors (20) and (21), respectively. A base current is supplied to the semiconductor switches (3) and (4). (2
2) (23) (24) (25) (26) (27) are diodes,
The diode (22) is connected between the base side of the third semiconductor switch (3) and the first semiconductor switch (1).
DC power supply (18) so as to block the base current to the third semiconductor switch (3) when the semiconductor switch (1) is turned on.
To the first semiconductor switch (1). The diode (23) is connected to the base side of the fourth semiconductor switch (4) and the second semiconductor switch (4).
The second semiconductor switch (2) is connected between the semiconductor switch (2) and the DC power source (19) so as to block the base current to the fourth semiconductor switch (4) when the second semiconductor switch (2) is turned on. ) To the current. The first semiconductor switch (1) and the second semiconductor switch (2) are ON / OFF controlled by a control circuit (not shown) so that they are alternately conducted as in the conventional case.

Next, the operation will be described. When the first semiconductor switch (1) is off, the base current IB flows from the DC power source (18) through the resistor (20) to the third semiconductor switch (3) as shown in FIG. ) Is on. When the first semiconductor switch (1) is turned off, the diode (22)
(24) is turned on, the current flowing through the resistor (20) flows through the diodes (22) (24), and the base current IB to the third semiconductor switch (3) stops flowing. 3 The semiconductor switch (3) is turned off. That is, the voltage at the point (b) shown in FIG. 2 is about 0V with respect to the point (a) (point (c) is -0.6V, point (b) is -0.6V + 0.6V = 0V).

Similarly, when the second semiconductor switch (2) is off, the base current IB flows from the DC power source (19) to the fourth semiconductor switch (4) through the resistor (21), and the semiconductor switch (4) is turned on. Is on. When the first semiconductor switch (1) is turned off, the diodes (23) (25) are turned on, and the current flowing through the resistor (7) is changed to the diode (23) (2
5), the base current IB to the fourth semiconductor switch (4) stops flowing, and the fourth semiconductor switch (4)
Turn off.

FIG. 3 shows another embodiment, in which diodes (30) (31)
(32) (33) (34) and diodes (35) (36) (37)
(38) and (39) are provided. In the circuit shown in FIG. 1, when the load (6) is not connected and the load current IL is not flowing, the diodes (24) (25) are turned off and the current flowing through the resistors (20) (21). Flows to the base of the third semiconductor switch (3) or the fourth semiconductor switch (4),
Although the third and fourth semiconductor switches (3) and (4) will be turned on, such inconvenience can be prevented by using the circuit configuration shown in FIG. That is, in the case of this circuit, when the first semiconductor switch (1) is turned on, the voltage at the point (b) with respect to the point (a) becomes the diode (2
The voltage of 6) is 0.6V, the voltage between the collector of the first semiconductor switch (1) and the emitter is about 1V, and the voltage of the diode (22) is
Since it is 0.6V, it suffices to add these voltages to obtain 2.2V, but the diode (30) (31) (32) (3
If the point (b) is not turned on unless the point (b) becomes 3 V or more according to 3), the third semiconductor switch (3) is not turned off when the first semiconductor switch (1) is turned on. The same applies to the fourth semiconductor switch (4).

〔The invention's effect〕

According to the invention, third and fourth semiconductor switches (3)
DC power supply (18) that supplies base current to the base of (4)
(19), a diode (22) for blocking a base current to the third semiconductor switch (3) when the first semiconductor switch (1) is on, and a fourth diode (22) when the second semiconductor switch (2) is on.
Since the diode (23) for blocking the base current to the semiconductor switch (4) is provided, it is a very simple circuit configuration without using a photocoupler or a transformer as in the conventional case, and the first side on the minus side or When the second semiconductor switches 1 and 2 are turned on, the positive side third or fourth semiconductor switch 3 or 4 can be reliably turned off in response to this.
It is possible to prevent the semiconductor switch 1 and the third semiconductor switch 3, and the second semiconductor switch 2 and the fourth semiconductor switch 4 from being simultaneously conducted. Moreover, by driving one of the first semiconductor switch 1 and the second semiconductor switch 2, the other third
Since the semiconductor switch 3 and the fourth semiconductor switch 4 can be turned on and off, only the first semiconductor switch 1 and the second semiconductor switch 2 need to be controlled so as to be alternately conducted, and the control circuit of the inverter circuit is very simple. In addition, since the first, second, third and fourth semiconductor switches 1, 2, 3 and 4 are each composed of NPN transistors, even if high breakdown voltage transistors are used, PNP
Since it is cheaper than the case of using a transistor, the entire inverter circuit can be provided easily and at low cost. Moreover, since the other third semiconductor switch 3 and the fourth semiconductor switch 4 can be turned on and off by driving the first semiconductor switch 1 and the second semiconductor switch 2 as described above, the semiconductor switches 1, 3 or the semiconductor switches can be switched from the power source. There is no fear that a short circuit current will flow through 2,4 and the failure of the semiconductor switches 1,2,3,4 due to the short circuit current can be prevented, and its practical effect is remarkable.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a circuit diagram for explaining the same operation, FIG. 3 is a circuit diagram showing another embodiment,
4 to 7 are circuit diagrams showing a conventional example. (1) (2) (3) (4) …… Semiconductor switch, (5)
...... DC power supply, (18) (19) ...... DC power supply, (22) (2
3) …… Diode.

Claims (1)

[Claims] 1. A negative-side first and second semiconductor switch (1) (2) and a positive-side third and fourth semiconductor switch (3) (4) bridge-connected to a DC power source (5). The first and fourth semiconductor switches (1) (4) and the second
And the connection points of the first and third semiconductor switches (1) and (3) and the connection points of the second and fourth semiconductor switches (2) and (4) by alternating conduction with the third and third semiconductor switches (2) and (3). A bridge inverter circuit configured to output an AC voltage between the first, second, third and fourth semiconductor switches (1)
(2), (3) and (4) are respectively composed of NPN transistors, and DC power supplies (18) and (19) for supplying a base current are provided to the bases of the third and fourth semiconductor switches (3) and (4), respectively. The DC power supply (18) is connected to the first semiconductor switch (1) via the resistors (20) (21) so as to block the base current to the third semiconductor switch (3) when the first semiconductor switch (1) is turned on.
Diode (22) that sends current to semiconductor switch (1)
And a diode (23) for flowing a current from the DC power supply (19) to the second semiconductor switch (2) so as to block a base current to the fourth semiconductor switch (4) when the second semiconductor switch (2) is turned on. Are connected between the base sides of the third and fourth semiconductor switches (3) and (4) and the first and second semiconductor switches (1) and (2), respectively. Control for alternately conducting the first semiconductor switch (1) and the second semiconductor switch (2) so that the third semiconductor switch (3) and the fourth semiconductor switch (4) are turned on and off by driving the second semiconductor switch (2). A bridge inverter circuit characterized in that a circuit is provided.