Discharge lamp igniting device and light appliance

Abstract

Provided is a discharge lamp lighting device and a light apparatus capable of stabilizing an output to a load circuit against a change in the temperature of a current transformer. The device comprises a driving circuit (5) equipped with a current transformer (CT1) having a detection winding (CT2a) to detect a current flowing in a load circuit (4) and positive feedback windings (CT1b, CT1c) which feedback currents to first and second switching means (Q1, Q2), respectively, by magnetic coupling, a magnetic energy control means (6) to control the magnetic energy of the current transformer (CT1), a current detecting means (7) to detect a mean value of an output current of a direct current power source (2) or a current flowing in a switching circuit (3), and a current control means (8) to control the magnetic energy control means (6) so that the mean value of the current falls on a preset value.

Description

technical field [0001] The present invention relates to a discharge lamp lighting device equipped with a switching means for self-oscillation by feedback current and a lighting fixture using the device. Background technique [0002] In a discharge lamp lighting device having a half-bridge inverter circuit, a technique is currently used to form a drive signal for a switching element by feeding back a current flowing through a load circuit and self-oscillating. Furthermore, such a discharge lamp lighting device generally includes a current transformer with a detection coil for detecting a load current and a feedback coil for generating a drive signal for a switching element by magnetic coupling with the detection coil. The current transformer has temperature characteristics because the magnetic core is made of a magnetic material, so when there is a temperature rise due to a rise in ambient temperature due to heat generation of other circuit components constituting the dischar...

AI Technical Summary

Problems solved by technology

With this circuit configuration, the current flowing through the saturable transformer Tr11 flows through the capacitor capacitor C12 and the aforementioned primary winding Tr12a, so in the load current detection circuit 24, the current flowing through the load circuit including the saturable transformer Tr11 cannot be obtained.

Therefore, although the current flowing through the fluorescent lamps FL1 and FL2 can be controlled to a constant value due to the change in the magnetic characteristics due to the self-heating of the saturable transformer Tr11, the current flowing through the load circuit cannot be controlled to a constant value.

[0012] That is, although the technique of Patent Document 1 can actually perform constant current control on the connected discharge lamp, it cannot expect low-power control on a different type of discharge lamp.

[0013] Furthermore, in the invention described in Patent Document 2, the ambient temperature is detected by the thermosensitive element 53, so the change in the resistance value is delayed in response to a change in the ambient temperature, and the output of the inverter circuit 54 cannot be stabilized quickly.

Especially for the change of the magnetic properties by the self-heating of the current transformer CT4, it has the disadvantage of not being able to follow

[0014] In addition, in the invention described in Patent Document 3, constant power is achieved by using a control IC or the like, so the problem of high cost cannot be avoided.

In addition, although it has been proposed to achieve constant power by the so-called self-excited method using control ICs, it has not been possible to achieve high-level constant power by using the self-excited method using a current transformer.

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