JPH03155096A - Discharge lamp lighting circuit - Google Patents

Abstract

PURPOSE:To make a power source transformer unnecessary by providing an intermediate tap on a choke coil, and connecting a series resonance winding formed on one side of the intermediate tap and a capacitor for power-factor improvement to a power source in series. CONSTITUTION:When no load is imposed, a current flows to the series resonance winding 13 of a choke coil 14 and a capacitor 17 for power-factor improvement, and a series resonant voltage is induced in the series resonance winding 13 by the inductance of the series resonance winding 13 and the capacitance of the capacitor 17 for power-factor improvement. The series resonant voltage is generated on the side to add to the power source voltage, and since a main winding 12 is provided at the opposite side to the series resonance winding 13 placing the intermediate tap 15 at the center, the inducted voltage on the main winding 12 induced in the same direction as the series resonant voltage is generated on the side to reduce the voltage of a commercial AC power source 11. And the nonload secondary voltage between a discharge lamp 16 is reduced to the voltage lower than the voltage of the commercial AC power source 11, and the voltage can be set as desired by the winding number ratio of the main winding 12 and the series resonance winding 13. Consequently, no power source transformer is required.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a discharge lamp lighting circuit for lighting a discharge lamp such as a high-pressure sodium lamp or a metal halide lamp.

(Prior Art) A conventional discharge lamp lighting circuit of this type includes, for example, a commercial AC power source 1, a power transformer 2, a power factor correction capacitor 3, a choke coil 4, etc., as shown in FIG. A ballast 5 is connected to the ballast 5, and a discharge lamp 6 is connected to the output end of the ballast 5.

Further, since the discharge lamp 6 such as a high pressure sodium lamp or a metal halide lamp needs to be started by applying a high voltage pulse, a ballast 5 is used as shown in FIG.
A high voltage pulse generation circuit 7 is provided between the discharge lamp 6 and the discharge lamp 6 .

However, the discharge lamp 6 such as a high-pressure sodium lamp or a metal halide lamp has a lamp output of 100W.
Since the ballast 5 is large and heavy, it is generally installed at a separate location from the lamp in which the discharge lamp 6 is installed.

Therefore, when the high voltage pulse generation circuit 7 is built into the ballast 5, special measures are required for the wiring from the ballast 5 to the discharge lamp 6.

In other words, the pulse frequency of high voltage pulses is several 10 K)
Since the frequency is as high as several MHz from It, ballast 5 and discharge lamp 6 are required.
The high voltage pulse is attenuated by the stray capacitance of the wiring between the ballast 5 and the ballast 5.
There is also a restriction on the length of the wiring from the discharge lamp 6 to the discharge lamp 6.

Therefore, lamps with a built-in high-voltage pulse generation circuit 7 are manufactured, and in this case, the no-load secondary voltage of the ballast 5 used in combination with the lamp is determined by the high-voltage pulse generation circuit built into the lamp. operating voltage.

Further, even in the discharge lamp 6 that does not require a high voltage pulse for starting, discharge lamps such as high pressure sodium lamps or metal halide lamps with high color rendering properties have large variations in color temperature due to differences in applied voltage. The no-load secondary voltage of the stabilizer 5 is determined to be a constant value.

Therefore, the ballast 5 combines a leaky transformer or power transformer and a choke coil to generate a specified no-load secondary voltage.

(Problem to be Solved by the Invention) As described above, even if the secondary voltage of the ballast 5 is higher than the specified no-load secondary voltage, it is not possible to apply it to the discharge lamp 6 using a leakage transformer or a power transformer. Therefore, the ballast 5 is large and heavy, and furthermore, it is expensive.

The present invention was made in view of the above problems, and an object of the present invention is to provide an economical discharge lamp lighting circuit that is small, lightweight, and simple.

[Structure of the invention]

(Means for Solving the Problems) The discharge lamp lighting circuit of the present invention has an intermediate tap drawn out from the middle part of one winding, and one side of the intermediate tap is formed as the main winding, and the other side is formed as the main winding. a choke coil formed into a series resonant winding, the intermediate tap connected to one end of the power source, and the main winding connected to the other end of the power source via a discharge lamp; the series resonant winding of the choke coil; and the power source. A capacitor for power factor correction is connected between the other ends.

(Function) In the present invention, the voltage across the power factor correction capacitor is controlled by the inductance of the series resonant winding and the capacitance of the power factor correction capacitor, through which current flows from the power supply to the power factor correction capacitor when there is no load. Higher than the voltage. The voltage difference between the voltage of this power factor correction capacitor and the voltage of the power supply is transformed by the turns ratio of the series resonant winding and the main winding, and is applied to the no-load secondary voltage across the discharge lamp. becomes a predetermined no-load secondary voltage lower than the power supply voltage.

(Example) Hereinafter, a discharge lamp lighting circuit of the present invention will be described with reference to an example.

In FIG. 1, 11 is a commercial AC power supply, and one end of this commercial AC power supply 11 is a series resonant winding with the main winding 12! 913 to the intermediate tap 15 of the choke coil 14. An end of the choke coil 14 on the main winding 12 side is connected to the other end of the commercial AC power supply 11 via a discharge lamp 16. In addition, the series resonant winding 1 of the choke coil I4
The end on the third side is connected to the other end of the commercial AC power supply 11 via a power factor improving capacitor 17 and a discharge resistor 18 in parallel.

Next, the operation of the embodiment shown in FIG. 1 will be explained.

When there is no load, current flows through the series resonant winding 13 of the choke coil H and the power factor improving capacitor 17, and the series resonant winding 13 is , a series resonant voltage is induced. This series resonant voltage is generated in the sum direction with respect to the power supply voltage, and since the main winding 12 is provided on the opposite side of the series resonant winding I3 across the intermediate tap 15, the series resonant voltage and The induced voltage in the main winding I2 induced in the same direction is generated in the direction of the difference from the voltage of the commercial AC power supply 11, and the no-load secondary voltage across the discharge lamp 16 is the voltage of the commercial AC power supply 11. The voltage will be lower. This voltage can be arbitrarily set by changing the turn ratio between the main winding 12 and the series resonant winding 13.

Further, when the discharge lamp 16 is lit, the main winding 12 operates as a choke coil, the power factor improving capacitor 17 improves the power factor, and the stable lighting of the discharge lamp 16 is maintained.

As another embodiment, a discharge lamp lighting circuit including a high voltage pulse generating circuit 21 will be described with reference to FIG.

The circuit shown in FIG. 2 has a circuit between the choke coil 14 and the discharge lamp 16 of the discharge lamp lighting circuit shown in FIG.
A high voltage pulse generation circuit 21 is connected thereto.

This high voltage pulse generation circuit 21 includes a choke coil 14
A coil 22 is connected between the coil 22 and the discharge lamp 16, and a resistor 23, a capacitor 24, and a switching element such as a triac 25 are connected in series between the middle of the coil 22 and the other end of the commercial AC power supply 11. . Further, a capacitor 26 is connected between the connection point of the choke coil 14 and the coil 22 and the other end of the commercial AC power supply 11. Further, between the gate of the triac 25 and the other end of the commercial AC power supply 11, a parallel circuit of, for example, a 5S827 and a capacitor 28 and a resistor 29 is connected in series as an auxiliary switching element, and the choke coil 14 and the coil 22 are connected. Point and S S S 27,
A resistor 30 is connected between the connection point of the capacitor 28 and the resistor 29.

Then, before the discharge lamp 16 lights up, the discharge lamp 16
Since the voltage across the filaments is high, the voltage across capacitor 26 increases. Then, charge is accumulated in the capacitor 28 and the voltage of the capacitor 28 increases, causing 5
S827 breaks over and turns on, triac 2
By triggering 5, the charge stored in the capacitor 24 is discharged and becomes a high voltage pulse, which causes a discharge lamp! 6
start.

Further, after the discharge lamp 16 is turned on, the potential difference between the filaments of the discharge lamp 16 decreases, so the voltage of the capacitor 26 decreases and high voltage pulses are not generated.

〔Effect of the invention〕

According to the present invention, the choke coil is provided with an intermediate tap,
Since the DC resonant winding formed on one side of this intermediate tap and the power factor correction capacitor are connected in series to the power supply, the choke coil provides a no-load secondary voltage lower than the voltage of the power supply. No transformer required, compact size,
Economical with lightweight and simple circuitry.

[Brief Description of the Drawings] Fig. 1 is a circuit diagram showing one embodiment of the discharge lamp lighting circuit of the present invention, Fig. 2 is a circuit diagram showing another embodiment of the same, and Fig. 3 is a circuit diagram of a conventional discharge lamp lighting circuit. FIG. 4 is a circuit diagram showing a lighting circuit, and FIG. 4 is a circuit diagram showing another conventional example. 11...Commercial AC power supply, 12...Main winding, 13...Series resonance winding, 14...Choke coil, 15...Intermediate tap, 16...Discharge lamp, 17...Capacitor for power factor improvement.

Claims (1)

[Claims] (1) It has an intermediate tap drawn out from the middle part of one winding, one side of this intermediate tap is formed as a main winding, and the other side is formed as a series resonant winding, and the intermediate tap is connected to one end of the power supply. a choke coil connected to the main winding and whose main winding is connected to the other end of the power source via a discharge lamp; and a power factor correction capacitor connected between the series resonant winding of the choke coil and the other end of the power source. A discharge lamp lighting circuit characterized by comprising: