JPH0290496A - Electric discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To reduce the amount of a rash current flowing through a condensor for power-factor improvement to a small value and also cause the condensor to produce the effect of power-factor improvement by connecting a non-linear element in series with the condensor, the non-linear element having negative temperature-resistance property. CONSTITUTION:A thermistor 8, which is connected in series with a condensor 6 for power-factor improvement, restrains a rush current flowing through the condensor 6. A switch 2 is therefore prevented from being welded at contact. Since the temperature-resistance property of the thermistor 8 is negative and it therefore exhibits self-heating ability, resistance is made smaller to allow the condensor to produce the effect of power-factor improvement.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a discharge lamp lighting device in which a power factor correction capacitor is connected in parallel to a discharge lamp circuit equipped with a coil.

2. Description of the Related Art Conventionally, a discharge lamp lighting device in which a power factor improving capacitor is connected in parallel to a discharge lamp circuit (ballast) is known, for example, from Japanese Utility Model Application Publication No. 49-93569. Since this type of circuit device uses a switching power supply, an inrush current may occur in the capacitor in the discharge lamp circuit.

If such an inrush current to the ballast is large, problems such as welding of the contacts of the open/close switch may occur.

Therefore, conventionally, a reactor is connected in series with a power factor correction capacitor to reduce the rush current to the capacitor.

Problems to be Solved by the Invention However, if such actors are used, the cost will be high.

[Means for solving the problem] In a discharge lamp lighting device in which a power factor improvement capacitor is connected in parallel to a discharge lamp circuit equipped with a power factor correction capacitor, a non-linear circuit having a negative temperature-resistance characteristic is connected in series to the power factor improvement capacitor. Connect the sexual elements.

When an inrush current is about to flow into the operating discharge lamp circuit, the presence of a nonlinear element with a negative temperature-resistance characteristic, such as a thermistor, suppresses the inrush current into the capacitor to a small value. Such nonlinear elements with negative temperature-resistance characteristics can be inexpensive.

Additionally, although there is a nonlinear element with a negative temperature-resistance characteristic in series with the capacitor, during normal use, the resistance value decreases due to self-heating of the non-linear element with a negative temperature-resistance characteristic. Therefore, the power factor improving effect of the power factor improving capacitor is not impaired.

Example An embodiment of the present invention will be described based on the drawings.

First, a discharge lamp circuit 3 is provided in the power supply 1 via an opening/closing switch 2 for starting, and a discharge lamp 4 is connected to the discharge lamp circuit 3. Here, the discharge lamp circuit includes a coil 5 for limiting the circuit current to a constant value, a power factor correction capacitor 6 connected in parallel to this coil 5, and a discharge lamp connected in parallel to this capacitor 6. It consists of a resistor 7.

Therefore, in this embodiment, a nonlinear element having a negative temperature-resistance characteristic, such as a thermistor 8, is connected in series with the power factor improving capacitor 6. That is, this thermistor 8 has a characteristic that the higher the temperature, the lower the resistance value.

According to such a configuration, when a rush current is about to flow into the power factor correction capacitor 6, the thermistor 8 is present in series with the capacitor 6, so that the rush current to the capacitor 6 is suppressed. Therefore, welding of the contacts of the open/close switch 2 due to rush current is also prevented. In other words, the purpose can be achieved with a relatively inexpensive and simple configuration using the thermistor 8.

Also, during normal use, this thermistor 8
Since the temperature-resistance characteristic is negative and the resistance value decreases due to self-heating, the power factor improving capacitor 6 can sufficiently exhibit the power factor improving effect.

Effects of the Invention The present invention provides a discharge lamp lighting device in which a power factor improvement capacitor is connected in parallel to a discharge lamp circuit equipped with a coil as described above. Since a non-linear element is connected, when an in-rush current is about to flow into the discharge lamp circuit, the presence of an inexpensive and simple non-linear element with negative temperature-resistance characteristics suppresses the in-rush current into the capacitor to a small value. This also prevents welding of the contacts of the open/close switch.In addition, during normal use, the resistance value decreases due to self-heating of the nonlinear element, which has a negative temperature-resistance characteristic, improving the power factor. The power factor improvement effect of the capacitor can be fully demonstrated.

3...Discharge lamp circuit, 5...Coil, 6...Capacitor for power factor improvement, 8...Nonlinear element with negative temperature-resistance characteristic

Claims (1)

[Claims] A discharge lamp lighting device in which a power factor correction capacitor is connected in parallel to a discharge lamp circuit equipped with a coil, characterized in that a nonlinear element having a negative temperature-resistance characteristic is connected in series with the power factor correction capacitor. discharge lamp lighting device.