JPH07114153B2 - Discharge lamp lighting circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application] 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 a commercial AC power source 1, a power transformer 2, a power factor improving capacitor 3, a choke coil 4, and the like, as shown in FIG. 3, for example. Is connected to the ballast 5, and the discharge lamp 6 is connected to the output terminal 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, 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 output of a discharge lamp 6 such as a high pressure sodium lamp or a metal halide lamp is from 100W.
Since the ballast 5 is as large as about 2 KW and the ballast 5 is large and heavy, it is generally installed in a place different from the lamp in which the discharge lamp 6 is provided.

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

That is, since the pulse frequency of the high voltage pulse is as high as several tens KHz to several MHz, the high voltage pulse is attenuated by the stray capacitance of the wiring between the ballast 5 and the discharge lamp 6,
The generated pulse voltage must be higher than the voltage required for starting the discharge lamp 6, and the length of the wiring from the ballast 5 to the discharge lamp 6 is also limited.

Therefore, a high voltage pulse generating circuit 7 is built in the lamp, and in this case, the no-load secondary voltage of the ballast 5 used in combination with the lamp is the high voltage pulse generating circuit incorporated in the lamp. Must match the operating voltage of.

Further, even in the discharge lamp 6 which does not require a high voltage pulse for starting, a discharge lamp such as a high color rendering high pressure sodium lamp or a metal halide lamp has a large variation in color temperature due to a difference in applied voltage. The unloaded secondary voltage of the ballast 5 is determined to be a constant value.

Therefore, the ballast 5 is a combination of a leakage transformer or a power transformer and a choke coil in order to generate a specified unloaded secondary voltage.

(Problems to be Solved by the Invention) As described above, even when the secondary voltage of the ballast 5 is higher than the specified unloaded secondary voltage, it is applied to the discharge lamp 6 by using a leakage transformer or a power transformer. Therefore, there is a problem that the ballast 5 is large and heavy, and the cost is high.

The present invention has been made in view of the above problems, and an object thereof is to provide an economical discharge lamp lighting circuit with a small, lightweight, and simple circuit.

[Structure of Invention]

(Means for Solving the Problem) The discharge lamp lighting circuit of the present invention has an intermediate tap drawn from the intermediate portion of one winding, and one side of this intermediate tap is formed in the main winding and the other side is formed. A choke coil formed in a series resonance winding, the intermediate tap being connected to one end of a power supply, and the main winding being connected to the other end of the power supply via a discharge lamp, and the series resonance winding of the choke coil and the power supply. And a power factor improving capacitor connected between the other ends of the.

(Operation) The present invention uses the inductance of the series resonance winding in which a current flows from the power source to the power factor improving capacitor when there is no load and the capacitance of the power factor improving capacitor, so that the voltage across the power factor improving capacitor is Higher than the voltage. Then, the voltage that is the difference between the voltage of the power factor improving capacitor and the voltage of the power supply is transformed by the turns ratio of the series resonant winding and the main winding, and the no-load secondary voltage applied across the discharge lamp. Is 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 connected to an intermediate tap 15 of a choke coil 14 having a main winding 12 and a series resonance winding 13. The 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. The end of the choke coil 14 on the side of the series resonance winding 13 is connected in parallel to the other end of the commercial AC power supply 11 via a power factor improving capacitor 17 and a discharge resistor 18.

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

When no load is applied, a current flows through the series resonance winding 13 of the choke coil 14 and the power factor improving capacitor 17, and the inductance of the series resonance winding 13 and the capacitance of the power factor improving capacitor 17 cause the series resonance winding 13 Then, a series resonance voltage is induced. This series resonance voltage is generated in the direction of the sum with respect to the power supply voltage, and since the main winding 12 is provided on the opposite side of the series resonance winding 13 across the intermediate tap 15, The induced voltage of the main winding 12 induced in the same direction is generated so as to have a direction different from the voltage of the commercial AC power supply 11, and the no-load secondary voltage between the discharge lamps 16 is the voltage of the commercial AC power supply 11. Lower voltage. Then, this voltage can be arbitrarily set by the turn ratio of the main winding 12 and the series resonance 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 discharge lamp 16 maintains stable lighting.

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

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

This high-voltage pulse generation circuit 21 connects a coil 22 between the choke coil 14 and the discharge lamp 16, and
A resistor 23, a capacitor 24, and a triac 25, for example, as a switching element are connected in series between the middle of the above and the other end of the commercial AC power supply 11. Also a choke coil
A capacitor 26 is connected between the connection point of the 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 source 11, for example, a parallel circuit of an SSS 27 and a capacitor 28 and a resistor 29 is connected in series as an auxiliary switching element,
Connection point of choke coil 14 and coil 22, SSS27,
Between the connection point of capacitor 28 and resistor 29, resistor 30
Are connected.

Since the voltage between the filaments of the discharge lamp 16 is high before the discharge lamp 16 is turned on, the voltage of the capacitor 26 rises. Then, the charge is accumulated in the capacitor 28, the voltage of the capacitor 28 rises, the SSS 27 breaks over and turns on, and the triac 25 is triggered to discharge the charge accumulated in the capacitor 24,
A high-voltage pulse is generated to start the discharge lamp 16.

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

〔The invention's effect〕

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 improving capacitor were connected in series to the power supply, the choke coil provided a no-load secondary voltage lower than the voltage of the power supply. No need for a transformer, small size,
Economical with a lightweight and simple circuit.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a discharge lamp lighting circuit of the present invention, FIG. 2 is a circuit diagram showing another embodiment of the same as above, and FIG. 3 is a circuit diagram showing a conventional discharge lamp lighting circuit. FIG. 4 is a circuit diagram showing another conventional example of the above. 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. A winding having an intermediate tap drawn from an intermediate portion of one winding, one side of the intermediate tap being formed as a main winding and the other side being formed as a series resonance winding, the intermediate tap serving as a power source. A choke coil connected to one end and the main winding connected to the other end of the power supply via a discharge lamp, and a power factor improving capacitor connected between the series resonance winding of the choke coil and the other end of the power supply. And a discharge lamp lighting circuit comprising: