JP2576098B2 - Gate control method for forward conversion circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gate control system of a forward conversion circuit using a photosensitive semiconductor element such as a light trigger thyristor as a control element.

B. Summary of the Invention The present invention relates to a gate control method of a forward conversion circuit using a photosensitive semiconductor element as a control element, comprising: a neutral point of an input transformer connected to an AC side of the forward conversion circuit; By inserting a resistor separately in the electric circuit connecting the negative output terminal and the negative output terminal, a reliable forward conversion operation can be performed by a minute single pulse, and the life of the photosensitive semiconductor element is extended. is there.

C. Prior Art Conventionally, a rectifier circuit using a forward converter is configured, for example, as shown in FIG. In FIG. 4, 1 is a semiconductor element,
For example, it is a forward converter formed by three-phase bridge connection of thyristors u _g , v _g , w _g , x _g , y _g , and z _g . A resistor R is connected between the positive and negative output terminals of the forward converter 1. U, V, and W are input transformers (not shown) connected to the AC input side of the forward converter 1.
The next side is equivalently shown. Gate control of each thyristor of the forward converter 1 is performed by giving a double pulse from a control circuit (not shown) at a timing as shown in FIG. As a result, a three-phase AC input voltage as shown in FIG. 5A is converted into a DC voltage _VDC as shown in FIG. 5C. The pulse width of the gate signal needs to have a value that becomes the holding current of the thyristor, and is determined by the magnitude of the power source impedance, the load current, and the like. In addition, in the case of complete no-load, the current does not flow through the thyristor and the double pulse does not allow the current to flow, so the gate needs to be a communication gate.

D. Problems to be Solved by the Invention When the control element of the forward converter 1 is a thyristor,
There is no problem even if a continuous gate signal as shown in FIG. 5 (b) is applied. However, when a photosensitive semiconductor device, for example, a light trigger thyristor is used, there is a problem in providing the continuous gate signal because of the life of the optical gate. That is, since the gate width of a light trigger thyristor currently on the market is 100 μS or less at a cycle of 20 ms, if the control is performed by a continuous gate signal as shown in FIG. I will.

The present invention has been made in view of the above points, and a gate of a forward conversion circuit capable of performing a reliable forward conversion operation even if the gate is controlled by a single pulse of a minute width which does not shorten the life of the photosensitive semiconductor element. It is intended to provide a control method.

E. Means and Action for Solving the Problems The present invention provides a forward converter formed by bridge-connecting photosensitive semiconductor elements, a neutral point of an input transformer connected to the AC side of the forward converter, and A resistor connected separately to an electric path connecting the positive output terminal and the negative output terminal of the converter, and performing a gate control by supplying a single pulse to each photosensitive semiconductor element of the forward converter. Features.

Each time the single pulse is supplied, a current flows through each photosensitive semiconductor element via the input transformer and the resistor. Therefore, a DC voltage is obtained at the output side of the forward converter.

F. Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In FIG. 1, reference numeral 10 denotes an input transformer in which a secondary winding has a three-phase star connection, and an AC power supply (not shown) is connected to the primary winding. Light trigger thyristor u _g is the secondary side of the input transformer _{10, v g, w g,} x g, y g, forward converter 11 where the z _g was Buritsuji connection is connected. One end of a resistor R ₁ is connected to a positive bus P of the forward converter 11, and a resistor R ₂ is connected to a negative bus N of the forward converter 11.
Are connected at one end. The other ends of these resistors R ₁ and R ₂ are collectively connected to the neutral point of the input transformer 10. 12 light trigger thyristor u _g of single pulse 2 forward converter 11 of small width, as shown in FIG. 2 _{(b), v g, w} g, x g, y g, the gate control is supplied to the z _g Is a control circuit.

First, the gate pulse signal to the optical trigger thyristor u _g of the forward converter 11 is supplied at a time t ₁ of FIG. 2, the secondary side of the U-phase current of the input transformer 10 is light trigger thyristor u _g →
The resistance R ₁ flows through the neutral point of the input transformer 10. In this case the equivalent circuit is as shown in FIG. 3 (a), the light trigger thyristor u _g flows as indicated by arrows currents. Next, when a gate pulse signal is supplied to the light trigger thyristor z _g at time t ₂ , the W-phase current on the secondary side of the input transformer 10 is changed from the resistance R ₂ → the light trigger thyristor z _g → the neutral point of the input transformer 10 Flow through At this time, the equivalent circuit is shown in FIG.
And a current flows through the light trigger thyristor z _g as shown by the arrow in the figure. Also it becomes the same operation at time t ₃ ~t _6. As described above, the current is diverted to each light trigger thyristor every time a single-shot gate pulse signal is supplied, so that the operation is the same as that when a continuous gate signal as shown in FIG. 5B is given. . Therefore, a DC pulse waveform as shown in FIG. 5 (c) can be obtained by giving a small pulse of a single pulse to the forward converter 11 as shown in FIG. 2 (b).

G. Effects of the Invention As described above, according to the present invention, even a forward conversion circuit using a photosensitive semiconductor element to which a gate signal cannot be continuously supplied due to a problem of life, a single pulse of a minute width can be used. By simply performing gate control, the forward conversion operation can be reliably performed in the same manner as when a conventional continuous gate signal is applied. Further, since the gate signal width is very small, effects such as prolonging the life of the photosensitive semiconductor element can be obtained.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG.
3 (a) and 3 (b) are equivalent circuit diagrams when a gate signal is input, FIG. 4 is a conventional forward conversion circuit diagram, and FIG. 5 is a time chart for explaining the operation of FIG. FIG. 9 is a signal waveform diagram for describing a conventional forward conversion operation. 10 ...... input transformer, 11 ...... forward converter, 12 ...... control circuit, R _1, R ₂ ...... _{resistors, u g, v g, w} g, x g, y g, z g ...... light trigger thyristor .

Claims (1)

(57) [Claims] 1. A forward converter comprising bridged photosensitive semiconductor elements, a neutral point of an input transformer connected to an AC side of the forward converter, a positive output terminal and a negative output of the forward converter. A gate control method for a forward conversion circuit, comprising: a single path supplied to each photosensitive semiconductor element of the forward converter to perform gate control;