JPH0357118Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a self-excited self-limiting inverter circuit called the Royer system.

BACKGROUND ART This type of inverter has a simple circuit and high reliability, so it is widely used as a mobile AC power supply device using a storage battery or the like as a power source.

FIG. 2 shows an example of a conventional inverter circuit of this type. In FIG. 2, the output of a DC power source 1 such as a storage battery is switched by transistors 2 and 3, and an AC output is obtained from a secondary coil 42 of a transformer 4. A resistor 71 is for starting, and a resistor 72 is for limiting the base currents of transistors 2 and 3.

A tertiary coil 43 for controlling the transformer 4 is used to supply base current to the transistors 2 and 3 for self-oscillation, and a rectifying element 8 is inserted for efficient operation.

Problems that the invention aims to solve Since it is mainly used as an AC power source for transportation, storage batteries are often used as an input DC power source.
Therefore, a charging clip or the like that is easy to attach and detach is used to connect the storage battery and the inverter. As a result, in some cases, the polarity of the storage battery and inverter could be incorrect, resulting in reverse connections.

If it were to be connected incorrectly, a large reverse current would flow, causing an arc at the connection, as well as burning out the inverter circuit, so there was a need for protection and safety against reverse polarity connections.

Means for Solving the Problems In FIG. 2, which shows an example of a conventional inverter circuit of this kind, when the DC power supply 1 is connected in reverse to the circuit, the reverse current flows through the rectifier 8, the resistor 72, and the transistors 2 and 3. The current flows through the base-collector of the transformer 4 and the primary and tertiary coils of the transformer 4.

Therefore, in order to eliminate the reverse connection current, it can be prevented by instantly opening the current circuit when the reverse connection occurs.

The present invention was developed from this viewpoint, and emitters are installed at both ends of the primary coil of a transformer, which consists of a primary coil with a center tap for input, a secondary coil for output, and a tertiary coil with a center tap for control. In a self-excited self-limiting Royer inverter circuit in which the collectors of the first and second transistors which are made common are connected to each other, and both ends of the tertiary coil of the transformer are connected to the bases of the first and second transistors, respectively, the transformer A series circuit consisting of a first resistor, a second resistor, and a third resistor is inserted between the center tap of the primary coil of the transformer and the center tap of the tertiary coil of the transformer. A reverse blocking three-terminal thyristor (hereinafter referred to as a thyristor) is connected such that the gate is connected between the second resistor and the third resistor, the cathode is connected between the second resistor and the third resistor, and the emitters of the first and second transistors are connected as the anode. It is something.

Embodiment An embodiment of the present invention is shown in FIG. In the figure, 1 is a DC power supply, 2 and 3 are transistors, and 6
indicates a thyristor, 4 indicates a transformer, 51 and 52
The resistor 53 serves as a triggering resistor for the thyristor 6 and a starting resistor for the inverter, and a resistor 53 serves as a resistor for controlling the base currents of the transistors 2 and 3.

First, when the DC power supply 1 is connected to the circuit, the thyristor 6 is kept in the ON state by the resistors 51 and 52, and a starting current is applied to the bases of the transistors 2 and 3 via the resistor 53 and the tertiary coil 43 of the transformer 4. flows.

At that time, transistor 2 or 3, whichever comes first
Transformer 4 is connected through the transistor that is in the ON state.
is excited, and the voltage generated in the control tertiary coil 43 causes a base current to flow to the transistor 2 or 3 via the thyristor 6 and the resistor 53, turning one of the transistors ON and the other OFF.

However, when the iron core of transformer 4 reaches saturation,
The voltage developed in the coil of transformer 4 decreases and its polarity is reversed.

Therefore, transistors 2 and 3 change from ON to OFF by reversing the voltage of the tertiary coil for control.
The other one changes from OFF to ON, energizing the transformer again.

That is, due to the saturation of the iron core of the transformer 4, the transistors 2 and 3 alternately turn on and off repeatedly and enter an oscillating state. Therefore, an AC output can be obtained from the secondary coil of the transformer 4.

Therefore, if the DC power supply 1 is connected opposite to the polarity of the circuit (reverse connection), a + voltage is applied to the anode terminal of the thyristor 6 and a - voltage is applied to the cathode terminal, but the gate voltage becomes a negative potential than the cathode voltage. Thyristor 6 cannot be triggered. That is, since a closed circuit due to reverse connection is not formed, no reverse connection current flows. Of course, since a reverse voltage is also applied to transistors 2 and 3, they cannot be turned on and no current flows.

Effects of the invention As stated above, in the inverter circuit according to the invention, even if the DC power supply is accidentally connected in the opposite direction to the inverter polarity, no reverse current will flow, which may cause damage to the inverter circuit or arcing. The danger caused by the outbreak can be prevented.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of an inverter circuit according to the present invention, and FIG. 2 is a circuit diagram showing an example of a conventional inverter circuit of this type. 1...DC power supply, 2, 3...Transistor, 4
...Transformer, 51-53...Resistor, 6...Thyristor.

Claims (1)

[Scope of utility model registration request] A transformer consists of a primary coil with a center tap for input, a secondary coil for output, and a tertiary coil with a center tap for control.The collectors of the first and second transistors with a common emitter are placed at both ends of the primary coil of the transformer. In a self-excited self-limiting Royer inverter circuit in which both ends of the tertiary coil of the transformer are connected to the bases of the first and second transistors, the center tap of the primary coil of the transformer and the third Between the center taps of the next coil, the first resistor,
A series circuit consisting of a second resistor and a third resistor is inserted, a gate is connected between the first resistor and the second resistor, a cathode is connected between the second resistor and the third resistor, and a series circuit is connected between the first and second resistors.
An inverter circuit characterized in that a reverse blocking three-terminal thyristor is connected so that the emitter of a transistor serves as an anode.