JPH05244796A - Bridge circuit - Google Patents

Abstract

PURPOSE:To provide a bridge circuit which responds at a high speed by driving an H bridge circuit directly by an output of a drive circuit, in a DC-AC converter. CONSTITUTION:An H bridge is constituted of a DC motor 1 and FETs 4A to 4F for driving the DC motor 1, to connect a DC power supply 17 in parallel to the H bridge. Further, the FETs 4A, 4C are used to serve as P gate FETs, and the FET4B, FET4D to 4F are used to serve as an N gate FETs. Here, relays 2A, 2B are actuated by an external signal to switch a DC power supply 5 for on-off turning the FETs 4E, 4F, and a potential difference is generated between gate/source of the FET depending on the voltage division ratio of resistors 3A to 3D and resistors 3E to 3H, to switch the direction of rotation of the DC motor 1 by turning the FET on-off. In this way, a circuit scale can be contracted by simplifying an FET driving circuit without using a transformer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bridge circuit, and more particularly to a bridge circuit used in a DC-AC converter or the like.

[0002]

2. Description of the Related Art Conventionally, a bridge circuit of a DC-AC converter used to drive an AC power supply motor or fan is
As shown in FIG. 3, the drive circuit 16 alternately outputs, for example, a positive pulse of Q-Q1 and a negative pulse of R-R1 to switch the transistors 13 and 14 and the transistors 12 and 15 on and off. That is, the transistors 12 to 15 combined with the transformer are a switching unit combining the transformer and the transistor, and the shape sandwiching the load 11 is H.
Because it is a type, it is also called an H bridge. By outputting a pulse signal of a constant frequency from Q-Q1 and R-R1 by the drive circuit 16, the switching section of this H bridge is switched on and off, and an alternating current is alternately supplied to the load 11. The DC power supply 17 can be converted into an AC power supply and driven.

[0003]

The above-mentioned conventional bridge circuit requires a transformer that insulates the transistor circuit forming the H-bridge from the drive circuit, so that the circuit scale becomes large and the power consumption becomes large. is there. In addition, since a transformer is used, a DC component is not propagated, which makes it difficult to drive a DC power load.

An object of the present invention is to provide a bridge circuit which does not use a transformer and which can reduce the circuit scale and easily drive a DC power supply load.

[0005]

In the bridge circuit of the present invention, a first P-gate field effect transistor and a second N-gate field effect transistor are connected in series at a common connection point A as a first arm, and a second arm is provided. A third P-gate field effect transistor and a fourth N-gate field effect transistor are connected in series at a common connection point B as an arm of the, and a bridge is formed by the first arm and the second arm. A direct current power source is connected to the bridge, and a load operating with an alternating current is connected between the common connection points A and B, and the first, second, and
The voltage dividing resistors for applying a bias voltage to the respective gates of the third and fourth field effect transistors are the first and second voltage dividing resistors.
Connected to the side of the voltage effect transistor and the sides of the third and fourth field effect transistors, and connecting the fifth N-gate field effect transistor in parallel with the voltage dividing resistor of the second field effect transistor. A sixth N-gate field effect transistor is connected in parallel to the voltage dividing resistor of the fourth field effect transistor, and pulsed bias voltages having different polarities are applied to the respective gates of the fifth and sixth field effect transistors. Drive circuits for alternately applying are connected.

[0006]

The present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram of an embodiment of the present invention. In FIG. 1, a DC motor 1 and a FET 4 for driving the DC motor 1
An H bridge is constructed with A to 4F. A DC power supply 17 is connected in parallel with the H bridge. The FETs 4A and 4C are P-gate FETs, and the FETs 4B and 4D to 4F.
Is an N-gate FET. The resistors 3A to 3H are resistors for voltage division, the relays 2A and 2B are operated by the external ground, and FE
It is a switching drive circuit of the DC power supply 5 that turns on and off T4E and 4F. A potential difference is generated between the gate and source of the FET by the voltage division ratio of the resistors 3A to 3D and the resistors E to H to turn the FET on and off. For example, when the FET 4E is turned on, the resistors 3C and 3D are short-circuited. The FET 4B is off, a potential difference occurs between the gate and source of the FET 4A due to the voltage division ratio of the resistors 3A and 3B, and the FET 4A is turned on. next,
When the FET4F is off, set the voltage division ratio of the resistors 3E to 3H to F.
Since ET4C is turned off and FET4D is turned on, the current to the DC motor 1 is FET4A.
, And the DC motor 1 rotates in a fixed direction. When the FET 4E is turned off and the FET 4F is turned on by switching the switching circuit by the relays 2A and 2B, the current to the DC motor 1 flows through the FETs 4C and 4B, so that the rotation direction can be switched. Further, as another embodiment, it is possible to use a flip-flop circuit as a circuit for supplying the bias power for switching the FETs to the terminals 6A and 6B, and to supply the bias power for switching the FETs. The load can also be operated with an AC fan. By changing the clock frequency of the switching circuit, it is possible to supply AC power of any frequency to the AC fan.

[0007]

As described above, the present invention eliminates the need for a transformer, and simplifies the circuit for driving the FET to reduce the circuit scale and reduce the power consumption. Further, since the H bridge circuit can be directly driven by the output signal of the drive circuit, there is an effect that a bridge circuit which responds at high speed can be provided even with a pulse signal of any frequency.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention.

FIG. 2 is a circuit diagram of a conventional bridge circuit.

[Explanation of symbols]

 1 DC motor 2A, 2B relay 3A-3H resistance 4A-4F FET 5 DC power supply 6A, 6B terminal 17 DC power supply

Claims (2)

[Claims] 1. A first P-gate field effect transistor and a second N-gate field effect transistor as a first arm are connected in series at a common connection point A, and a third P-gate field effect transistor as a second arm. The transistor and the fourth N-gate field effect transistor are connected in series at a common connection point B, a bridge is formed by the first arm and the second arm, and a direct current power source is connected to the bridge to connect the common. A load operating with an alternating current is connected between the connection points A and B, and a voltage dividing resistor for applying a bias voltage to each gate of the first, second, third and fourth field effect transistors is connected to the first voltage dividing resistor. And the side of the second voltage effect transistor and the third
And a fourth field effect transistor side, and a fifth field effect transistor connected in parallel to the voltage dividing resistor of the second field effect transistor.
The N-gate field effect transistor is connected, and the sixth N-gate field effect transistor is connected in parallel to the voltage dividing resistor of the fourth field effect transistor.
2. A bridge circuit, characterized in that a drive circuit for alternately applying pulsed bias voltages having different polarities is connected to each gate of the field effect transistor of. 2. The bridge circuit is made to respond at a high speed by driving the flip-flop by making the frequency of a drive pulse signal from the outside variable by forming the drive circuit by a flip-flop. Bridge circuit.