JPH0442782A - Inverter circuit - Google Patents

Abstract

PURPOSE:To reduce the number of components and the size of a current feedback type inverter circuit by a method wherein a detection winding for overload protection is added to a current feedback transformer. CONSTITUTION:If a load 11 becomes an overload or a short-circuit, the primary current of an output transformer 7 is increased. The increased current is also applied to the primary winding 17 of a feedback transformer 8. If a current exceeding a rated current is applied to the primary winding 17, the winding voltage of a detection winding 18 added to the feedback transformer 8 is raised. The winding voltage rise of the detection winding 18 charges a capacitor 13 through a diode 12. A transistor 14 is turned ON by the voltage of the capacitor 13 and, by connecting the voltage of a capacitor 3 to GND, an SBS 4 becomes unable to be turned ON. A transistor 5 is turned OFF. The transistor 14 is kept on being ON and the transistor 5 is also kept on being OFF until the capacitor 13 is completely discharged.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an inverter circuit provided with an overload protection circuit in a current feedback inverter.

[Conventional technology]

Conventionally, in a current feedback inverter circuit, a detection resistor 19 is arranged in series with the switching element 5 and used as a detection means for overload protection, as shown in FIG. Therefore, in order to operate the overload protection circuit, it is necessary to increase the detection voltage, which inevitably increases the loss of the detection resistor 19, and also reduces the number of parts by using the detection resistor 19. This increases the size of the inverter circuit, making it impossible to downsize the inverter circuit.

[Problem to be solved by the invention]

The above-mentioned conventional technology does not consider the detection loss of the overload protection circuit, and cannot be miniaturized.

An object of the present invention is to obtain an inverter circuit that can reduce the number of components and be miniaturized by adding a detection winding for overload protection to a current feedback transformer.

[Means to solve the problem]

The above object is achieved by providing a current feedback transformer with a sensing winding for overload protection in a current feedback type inverter circuit.

[Effect]

When a current feedback inverter becomes overloaded, the current flowing through the current feedback transformer increases. Therefore, by adding a detection winding to the winding of the current feedback transformer, it is possible to know the change in the increasing current and detect an overload condition of the current feedback inverter.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram showing an embodiment of an inverter circuit according to the present invention. The embodiment shown in FIG. 1 is a circuit showing an inverter for lighting a halogen lamp, and operates as described below. When an AC voltage is applied to the above circuit, it is rectified by the diode stack 1 and charges the capacitor 3 via the resistor 2, so the charging voltage increases. When the switching voltage of (SBS) 4 increases, 5BS4 suddenly turns ON and the charge stored in the capacitor 3 is applied to the base of the transistor 5, so the transistor 5 turns on and discharges the charge of the capacitor 6. Stream to 7. This turns on the halogen lamp 11.

At that time, current also flows through the primary winding 17 of the feedback transformer 8, and the voltage in the base winding 16 of the transistor 9 rises, and when the transistor 5 turns off, the transistor 9 turns on.
L, the charge in the capacitor 10 flows to the output transistor and the halogen lamp 11 lights up. The transistor 9 is ONL until the feedback transformer 8 is saturated, and when the feedback transformer 8 is saturated, the transistor 9 is 0FFL, the voltage of the base winding 15 of the transistor 5 rises, and the transistor 5 is ONL until the feedback transformer 8 is saturated. Keep doing it. By repeating the above operation, transistor 5 and transistor 9 oscillate, and halogen lamp 11 lights up.

In this embodiment, when the halogen lamp 11 is mistakenly connected to a high-capacity lamp or short-circuited, a detection winding is added to the feedback transformer 8.
It protects overload circuits, and its operation is as follows.

When the load 11 becomes overloaded or short-circuited, the primary current of the output transformer 7 increases, but this increased current also flows to the primary winding 17 of the feedback transformer 8. When a current exceeding the rating flows through the secondary winding 17, the winding voltage of the detection winding 18 provided in addition to the feedback transformer 8 increases. This winding voltage increase of the detection winding 18 is caused by the diode 12
The capacitor 13 is charged via the capacitor 13.
5BS4 turns on by turning on the transistor 14 and dropping the voltage of the capacitor 3 to GND.
The transistor 14 remains ON until the capacitor 13 is no longer charged, and the transistor 5 turns OFF.
Continuing, transistor 5 also remains OFF. When the charge in the capacitor 13 disappears, the transistor 14
turns OFF, the voltage of capacitor 3 rises to the switching voltage of 5BS4, transistor 5 turns ON and starts oscillation, capacitor 13 is charged, and transistor 5 turns OFF as described above. The circuit repeats intermittent oscillation. protect

〔Effect of the invention〕

As described above, the inverter circuit according to the present invention is a current feedback type inverter circuit in which a detection winding for overload protection is provided in the current feedback transformer, so that the current flowing through the detection winding is detected and overload is detected. This is to know the status. According to this, a low-loss inverter circuit can be manufactured in a small size with a small number of parts.

[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 a conventional inverter circuit. 8... Current feedback transformer, 18... Detection winding.

Claims (1)

[Claims] 1. An inverter circuit of a current feedback type, characterized in that a detection winding for overload protection is provided in a current feedback transformer.