JPH08251806A - Protective circuit in the case of short circuit - Google Patents

Abstract

PURPOSE: To obtain a protective circuit in which the number of fuses or the like can be reduced without spoiling a protective function in the case of a short circuit by a method wherein a fuse or a fusing resistance is inserted into a common ground on the secondary side of a transformer. CONSTITUTION: When an output voltage line +B1 on the secondary side of a transformer(TR) 1 is short-circuited with a ground, a large current flows, in a circuit on the secondary side of the TR 1, to the ground again from the ground via a fuse or a fusing resistance 15 via a coil on the secondary side of the TR 1 via a diode 9. By the large current, the fuse or the fusing resistance 15 is made open. When an output voltage line +B2 on the secondary side of the TR 1 is short-circuited with the ground and, in addition, when an output voltage line +B3 on the secondary side of the TR 1 is short-circuited with the ground, the fusing resistance 15 is made simultaneously open. Thereby, even when any of the output lines is short-circuited, a protective function in the case of a short circuit can be satisfied when the fusing resistance 15 which is inserted into a common ground is made open.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is intended to prevent the transformer from smoking or igniting when the secondary output line of the transformer is short-circuited.
The present invention relates to a rationalization circuit of a protection circuit at the time of a short circuit, which is composed of a fuse or a fusing resistance (commonly known as a fuse resistance).

[0002]

2. Description of the Related Art FIG. 2 shows a circuit diagram of a conventional short-circuit protection circuit. In the figure, reference numeral 1 is a transformer. Reference numeral 2 is a secondary side of the transformer + B1 output terminal, 3 is a secondary side of the transformer + B2 output terminal, 4 is a secondary side of the transformer + B3 output terminal, and 5 is a secondary side common ground terminal of the transformer. 6 ~
Reference numeral 8 is a fuse or a fusing resistance (fuse resistance). 9 to 11 are rectifying diodes. 12 to 14 are smoothing capacitors.

[0003]

However, in such a configuration, it is necessary to insert a fuse or a fusing resistance for protection at the time of short circuit into all the output lines on the secondary side of the transformer.

SUMMARY OF THE INVENTION The present invention is based on the above problems, and an object thereof is to eliminate the drawbacks and to provide a short-circuit protection circuit with a simple structure.

[0005]

The short-circuit protection circuit of the present invention is a secondary circuit of a transformer in a circuit such as a power supply circuit or a deflection circuit using a transformer such as a switching mode transformer or a flyback transformer. When the side output line is short-circuited, a fuse or a fusing resistance (commonly known as a fuse resistance) is provided to prevent smoke and fire from the transformer.

[0006]

According to the short-circuit protection circuit of the present invention, the number of fuses or fusing resistances (commonly called fuse resistances) used is reduced without impairing the short-circuit protection function of each secondary output line of the transformer. can do.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A short circuit protection circuit according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration circuit diagram of a main part according to an embodiment of the present invention. In the figure, the same parts as those in FIG. 2 are designated by the same reference numerals. + B1
~ + B3 is the transformer secondary side output voltage.

In FIG. 1, + B on the secondary side of the transformer 1
The output terminal 1 is connected to the anode of the rectifying diode 9, and the cathode of the diode 9 is connected to the smoothing capacitor 12. The + B2 output terminal 3 on the secondary side of the transformer 1 is connected to the anode of the rectifying diode 10, and the cathode of the diode 10 is connected to the smoothing capacitor 13. The + B3 output terminal 4 on the secondary side of the transformer 1 is connected to the anode of the rectifying diode 11, and the cathode of the diode 11 is connected to the smoothing capacitor 14. The common ground terminal 5 on the secondary side of the transformer 1 is connected to a fuse or a fusing resistance (common name: fuse resistance) 15, and a fuse or a fusing resistance (common name: fuse resistance) is connected.
The other terminal of 15 is grounded.

The operation of the short-circuit protection circuit configured as described above will be described below. When the secondary output voltage line + B1 of the transformer 1 is short-circuited to the ground, in the secondary side circuit of the transformer 1, the secondary side coil of the transformer 1 is passed from the ground through a fuse or a fusing resistance (common name: fuse resistance) 15. A large current flows again to the ground through the diode 9 and the diode 9. This large current causes the fuse or fusing resistance (common name: fuse resistance) 15 to open.

Secondary output voltage line of transformer 1 + B2
Is also short-circuited to the ground, and when the secondary side output voltage line + B3 of the transformer 1 is also short-circuited to the ground, the fusing resistance 15 is similarly opened.

Therefore, even when any output line is short-circuited, the fusing resistance 15 inserted in the common ground is opened, so that the protection function at the time of short-circuit can be satisfied.

As described above, according to the embodiment of the present invention,
The structure of the protection circuit at the time of short circuit may be a structure other than the above as long as it has a function of opening the circuit when the output line is short-circuited.

[0013]

As described above, according to the present invention, the fuse or the fusing resistance is inserted between the common grounds on the secondary side of the transformer, so that the protection function at the time of short circuit of the secondary side of the transformer is not impaired. The number of fuses or fusing resistances to be used can be reduced, and excellent practical effects can be obtained.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a protection circuit configuration circuit at the time of a short circuit according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of a main part of a conventional protection circuit.

[Explanation of symbols]

 1 transformer 2 + B1 voltage output terminal 3 + B2 voltage output terminal 4 + B3 voltage output terminal 5 ground terminal 9, 10, 11 rectifying diode 12, 13, 14 smoothing capacitor 15 fusing resistance (common name: fuse resistance)

Claims (1)

[Claims] 1. In a circuit such as a power supply circuit or a deflection circuit which uses a transformer such as a switching mode transformer or a flyback transformer, when the secondary output line of the transformer is short-circuited, smoking or ignition of the transformer is prevented. Therefore,
A protection circuit at the time of a short circuit, which is provided with means constituted by a fuse or a fusing resistance (commonly known as a fuse resistance).