JPH037919Y2 - - Google Patents

Description

[Detailed explanation of the idea] This invention relates to a discharge lamp lighting device.

In a discharge lamp lighting device, when performing high-frequency lighting using a high-frequency inverter, the filament of the discharge lamp is preheated by a DC power source prior to lighting in order to improve lighting startability. In this case, in order to suppress the filament current, the secondary coil of the oscillation transformer that constitutes the high-frequency inverter is used as an impedance element for suppressing the filament current, and the secondary coil and the filament are connected in series when viewed from the preheating DC power source. I was trying to connect to. However, in this configuration, 2
When a direct current flows through the next coil, the iron core of the oscillation transformer becomes biased.

To solve this problem, two secondary coils are provided, and the DC current is configured to flow in opposite directions to both secondary coils, thereby preventing biased magnetization. However, even in this configuration, both secondary coils are connected in series to the filament.
Therefore, unless a high-voltage DC power source is prepared as a preheating DC power source, it is difficult to adjust the voltage applied to each filament to a predetermined value.

The purpose of this invention is to prevent biased magnetization of the oscillation transformer while also making it possible to use a low-voltage DC power source for preheating the filament.

This invention is characterized by using two secondary coils to connect the filament in parallel and preheat it.

An embodiment of this invention will be described with reference to the drawings. 1 is a DC power supply such as a battery, 2 is a high frequency inverter, and in the example shown, a transistor 3 and an oscillation transformer 4.
and a feedback coil 5, etc., and 6 is a switch element for starting. These configurations are not particularly different from conventional ones. 7 is a discharge lamp. Two secondary coils 9 and 10 having the same number of turns are prepared in an oscillation transformer 4 in which a primary coil 8 is connected to a transistor 3. And 2
The next coil 9 is the filament 7A, 7B of the discharge lamp 7.
, and the secondary coil 10 is connected between each local end. Further, a DC power supply 1 is connected between intermediate taps 11 and 12 of each secondary coil 9 and 10 via a switch element 13 for preheating and a resistor 14 for limiting filament current. Intermediate tap 11,1
2 is preferably a center tap.

According to the above configuration, when viewed from the DC power source 1, the filaments 7A and 7B are connected in parallel via each half of each secondary coil 9 and 10. That is, when the switch element 13 is turned on during preheating, the current from the DC power supply 1 is divided from the intermediate tap 11 to both halves of the secondary coil 9 as shown by the arrows in the figure, and from there the filaments 7A and 7B are connected. The current flows from the end of the secondary coil 10 and joins at the intermediate tap 12 to reach the DC power supply 1. In this way, each filament 7A, 7B is connected in parallel to the DC power supply 1, so compared to the case where the same voltage is applied to each filament but connected in series, the DC power supply 1 A low voltage one will suffice. In other words, even when the voltage of the DC power source 1 is low, it is possible to preheat each filament by applying a predetermined voltage to each filament. Since current flows in opposite directions in each half of each of the secondary coils 9 and 10, the oscillation transformer 4 is not biased.

Note that when both the secondary coils 9 and 10 have the same number of turns, if the intermediate taps 11 and 12 are set to the center tap, the high-frequency potential difference between the two taps becomes zero, and therefore a high-frequency current flows through the DC power supply 1. This will no longer be the case. Also, each secondary coil 10,1
Since the impedance value of each half of 1 is the same, the value of the current flowing through each filament is also conveniently the same.

In order to light up the discharge lamp 7 whose filament has been preheated, the switch element 6 may be turned on and the switch element 13 may be turned off. By turning off the switch element 13, preheating of the filament is stopped. Further, when the switch element 6 is turned on, the high frequency inverter 2 starts an oscillating operation, and a high frequency voltage is generated in the secondary coils 9 and 10. This voltage is applied to the discharge lamp 7,
This causes the discharge lamp 7 to light up. In this case, the voltages of the secondary coils 9 and 10 are both applied to the discharge lamp 7. It is therefore possible that a lamp current will flow between the ends of the filaments 7A, 7B. Alternatively, the lamp current flows through both secondary coils 9, 1.
Since the current is shunted to zero, loss as an oscillation transformer is also reduced.

As detailed above, according to this invention, when performing high-frequency lighting using a high-frequency inverter and DC preheating of the filament of a discharge lamp, each filament is connected to each half of the two secondary coils of the oscillation transformer. Since it is connected in parallel to the DC power supply through the oscillation transformer, biased magnetization of the oscillation transformer can be prevented, and a low power supply voltage can be used for preheating the filament.

[Brief explanation of the drawing]

The figure is a circuit diagram showing an embodiment of this invention. 1...DC power supply, 2...High frequency inverter, 4
...Oscillation transformer, 7...Discharge lamp, 7A, 7B...
...Filament, 9, 10...Secondary coil, 1
1, 12...middle tap.

Claims (1)

[Claims for Utility Model Registration] (1) A high-frequency inverter equipped with an oscillation transformer having two secondary coils, and a high-frequency inverter connected between the ends of each of the secondary coils, when the high-frequency inverter oscillates. A discharge lamp that is lit by a high-frequency voltage induced in the secondary coil, and a discharge lamp for preheating the filament of the discharge lamp, which is connected between one intermediate tap and the other intermediate tap of the secondary coil. A discharge lamp lighting device consisting of a DC power source and a DC power source. (2) The discharge lamp lighting device according to claim 1, wherein the intermediate tap is a center tap.