JPS6115599Y2 - - Google Patents

Description

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

When lighting a discharge lamp using a high-frequency power source, it is known that if a high-frequency high voltage is applied to the discharge lamp at the same time as the power is turned on, the discharge lamp will darken more quickly and its life will be shortened. ing. In order to prevent this, the electrodes of the discharge lamp may be preheated by turning on the power, and after a certain period of time, a high frequency and high voltage for starting the discharge lamp may be applied to the discharge lamp. However, if a high frequency high voltage is generated when the power is turned on, it is necessary to prevent that voltage from being applied to the discharge lamp during preheating.If a semiconductor switch is used for this purpose, Since the high frequency and high voltage will be applied to the semiconductor switch after lighting, this type of switch must have a high breakdown voltage. Also, a preheating coil is required to preheat the electrodes of the discharge lamp.

The purpose of this invention is to make it possible to use a semiconductor switch with low withstand voltage to prevent high frequency and high voltage from being applied to the discharge lamp during electrode preheating, and to omit the use of a preheating coil.

An embodiment of this invention will be described with reference to the drawings. 1 is a DC power supply, 2 is a lighting switch, 3 is a high frequency inverter device that converts DC voltage to high frequency voltage,
4 is an oscillation transformer, and 5 is a discharge lamp. These configurations are not particularly different from conventional high-frequency lighting devices that use a DC power source as a power source. According to this idea, an intermediate tap 7 is provided on the secondary coil 6 of the oscillation transformer 4 to divide the secondary coil 6. 6A, 6B
is each divided secondary coil. The intermediate tap 7 is connected to one end of a series circuit consisting of an impedance element (for example, a resistor) 8 for limiting the preheating current and a semiconductor switch, for example, a transistor 9. A diode 10 and a discharge lamp 5 are connected to the other end of this series circuit.
to the end of the secondary coil 6A via one electrode 5A of the diode 11, and the other electrode 5 of the discharge lamp 5.
are connected to the ends of the secondary coil 6B via B, respectively.

According to the above configuration, the diodes 10 and 11 are connected in series across both electrodes 5A and 5B, but in this case, both diodes 10 and 11 are connected in series so that their forward directions are opposite to each other. In the example shown in the figure, the transistor 9 is in the forward direction toward the intermediate tap 7, so the cathodes of the diodes 10 and 11 are connected together. However, if the forward direction of the transistor 9 is reversed, each The anodes of the diodes 10 and 11 may be connected together.
When a bidirectional thyristor is used in place of the transistor 9, the diodes 10 and 11 may be connected either between anodes or cathodes. 12 is a connection point between both diodes, and 13 is a timer circuit which operates when the switch 2 is turned on and turns on the transistor 9 by the output from this. When a predetermined time limit has elapsed, the output ends and the transistor 9 is turned off.

In the above configuration, when the switch 2 is turned on, the inverter device 3 operates, thereby generating a high frequency high voltage in the secondary coil 6 of the oscillation transformer 4. This voltage value is preset to a value sufficient to start and light the discharge lamp 5, but at this time, the transistor 9 is turned on by the operation of the timer circuit 12, so the voltage induced in the secondary coil 6 is Since the voltage applied to the discharge lamp 5 becomes lower than the original voltage value and is lower than the voltage sufficient to start the discharge lamp 5, the discharge lamp 5 does not start. The reason for this is, for example, when the voltage induced in the secondary coil 6A is negative on the intermediate point 7 side, and the voltage induced in the secondary coil 6B is positive on the intermediate point 7 side, the electrode 5A,
The circuit connecting the diode 10, the impedance element 8, and the transistor 9 becomes a load circuit, and the voltage drop caused by the electrode 5A and the impedance element 8 causes the secondary coil 6 to
The induced voltage becomes lower than that of A. On the other hand, the current in the secondary coil 6B is blocked by the diode 11, so the electrode 5
B, impedance element 8, etc. do not serve as a load, so the original voltage is induced in the secondary coil 6B. Thus, the sum of the induced voltages of both the secondary coils 6A and 6B becomes lower than the original induced voltage of the secondary coil 6. The same applies when the polarity of the induced voltage in the secondary coil 6 is reversed.

On the other hand, as mentioned above, when the voltage induced in the secondary coil 6A is negative at the intermediate point 7 side and the voltage induced in the secondary coil 6B is positive at the intermediate point 7 side, the voltage induced in the secondary coil 6A is Based on this, a current flows through a circuit connecting the electrode 5A, the diode 10, the impedance element 8, and the transistor 9, thereby preheating the electrode 5A. At this time, since the direction of the diode 11 is opposite to the induced voltage of the secondary coil 6B, no current flows and the electrode 5B is not preheated.
If the induced voltage in the secondary coil 6 is then reversed, the electrode 5B will be preheated, but the electrode 5A will not be preheated. That is, the electrodes 5A and 5B are alternately preheated for each half wave of the induced voltage of the secondary coil 6.

When each electrode 5A, 5B is charged and preheated in this manner, when the transistor 9 is turned off by the operation of the timer circuit 13, each preheating current is cut off, thereby causing the secondary coil 6 to The induced voltage returns to its original value and is applied to the discharge lamp 5. As a result, the discharge lamp 5 is activated and enters the lighting state. After lighting, the induced voltage of the secondary coils 6A and 6B is applied to the transistor 9, but since this voltage is naturally lower than the induced voltage of the secondary coil 6, the induced voltage of the secondary coil 6 is applied to the discharge lamp 5. Compared to a transistor for cutting off the secondary circuit so that no voltage is applied, a transistor with a low withstand voltage is sufficient.

As detailed above, according to this invention, when lighting a discharge lamp with high frequency and high voltage, a preheating coil for preheating the electrodes is unnecessary, and after preheating, high frequency and high voltage is applied to the discharge lamp. The effect is that a semiconductor switch with a low breakdown voltage is sufficient for starting the switch.

[Brief explanation of the drawing]

The figure is a circuit diagram showing an embodiment of this invention. 3...High frequency inverter device, 4...Oscillation transformer, 6...Secondary coil, 5...Discharge lamp, 5A,
5B... Electrode, 7... Intermediate point, 8... Impedance element, 9... Semiconductor switch (transistor), 12... Connection point.

Claims (1)

[Scope of utility model registration request] A circuit in which both ends of the secondary coil of an oscillation transformer of a high-frequency inverter device are connected to one end of each electrode of a discharge lamp, and a pair of diodes with opposite forward directions are connected in series across the other end of each electrode. and an impedance element for preheating current limitation between the connection point of both the diodes and the intermediate point of the secondary coil, and an impedance element that is turned on when the induced voltage of the secondary coil is applied to the discharge lamp. A high-frequency discharge lamp lighting device is formed by connecting a series circuit with a semiconductor switch that is turned off after a certain period of time.