JPS5926113B2 - Discharge lamp lighting circuit - Google Patents

Description

[Detailed description of the invention] The present invention relates to a discharge lamp lighting circuit.

As shown in Fig. 1, a conventional discharge lamp lighting circuit connects a series circuit body consisting of a discharge wrap 2 such as a high-strength discharge wrap and an inductance (current-limiting impedance) 3 between both ends of an AC power source 1. A series circuit body of an inductance (current limiting isohedance) 4 and a discharge lamp 5 such as a high-strength discharge wrap is connected between both ends of the AC power supply 1 so that the connection order is reversed to the series circuit bodies 2 and 3, and the discharge lamp 2 A capacitive starting current limiting impedance 6 consisting of a capacitor 6a and an inductance 6b is connected between the connection point of the inductance 3 and the connection point of the inductance 4 and the discharge lamp 5, and the power factor is connected between both ends of the AC power supply 1. A capacitor T for improvement is connected. In this case, the starting current limiting impedance 6 is set to a value that allows harmonic current (third harmonic) to flow. Figure 2 A shows the voltage V across the starting current limiting impedance 6 when starting the lamp.
FIG. 2B shows the voltage V and current I across the starting current limiting impedance 6 when the lamp voltage increases, and FIG. 2C shows the voltage across the starting current limiting impedance 6 when the lamp is stable. V and current I are shown.

Fig. 3A shows the lamp current IL when the starting current limiting impedance 6 is disconnected from the circuit, Fig. 3B shows the current I flowing through the starting current limiting impedance 6 when the lamp is stable, and Fig. 3C shows the lamp current IL when the starting current limiting impedance 6 is disconnected from the circuit. The wrap current IL is shown when the starting current limiting impedance 6 is connected to the circuit, and the third
The waveforms in Figures A and B are superimposed. In this discharge lamp lighting circuit, when the discharge lamps 2 and 5 are stably lit, the current I flowing through the starting current limiting impedance 6 becomes a harmonic current as shown in FIG. 3B.
This current I is superimposed on the lamp current IL shown in Fig. 3A, resulting in the result as shown in Fig. 3C, so even if the values of inductances 3 and 4 are set large, the wrap current IL cannot be kept at the rated value. can.

As a result, the wrap current (late phase) at startup can be reduced,
In addition, the current I flowing through the starting current limiting impedance 6
When starting the lamp, the phase leads the power supply voltage by 90 degrees as shown in FIG. 2A, so that the input current at starting can be reduced. Furthermore, since the starting input current can be reduced as described above, low starting current characteristics can be obtained without increasing the capacity of the power factor correction capacitor 7, and therefore no-load input current does not increase. Figure 4 shows discharge lamp 2.
When a high-pressure mercury lamp (H4OO) is used as . According to this figure, without increasing the capacitor capacity, the starting input current A1 and the no-load input current A can be adjusted to the stable input current A2. It can be seen that the currents A and K are approximately equal. However, in the discharge lamp lighting circuit shown in FIG. 1, when pulse-start type discharge lamps 2 and 5 are used, for example, if one discharge lamp 2 is started and lit before the inductance of 3K, the other In the discharge lamp 5, the inductance 4 is connected in parallel with the starting current limiting impedance 6 and the series circuit of the previously lit discharge lamp 2, so that the pulses generated by the inductance 4 are connected to the series circuit 6, It had the disadvantage that it absorbed more than 2VC and would not start.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a discharge lamp lighting circuit which is capable of reducing the input current at the time of starting (input current at no-load) and which is capable of reliably starting two discharge lamps. be.

An embodiment of this invention is shown in FIG.

That is, this discharge lamp lighting circuit connects a series circuit of a pulse-starting discharge lamp 2' with a built-in bimetal switch such as a high-intensity discharge lamp 2' and an inductance (current limiting impedance) 3 between both ends of an AC power supply 1. At the same time, a pulse-start discharge lamp 5' having a built-in bimetallic switch such as an inductance (current-limiting impedance) 4 and a high-intensity discharge lamp is connected in series so that the connection order is reversed with the series circuit bodies 2' and 3. A circuit body is connected between both ends of the AC power source 1, and a starting current limiter is applied between the connection point of the inductance 3 of the pulse-start discharge lamp 2' and the connection point of the inductance 4 and the pulse-start discharge lamp 5'. A series circuit of a capacitor (starting current limiting impedance) 8 and a saturable reactance 9 is connected, and a power factor improving capacitor 7 is further connected between both ends of the AC power source 1. In this case, the saturable reactance 9 has a high impedance in response to a high-voltage pulse for starting, and has a low impedance when the pulse-starting discharge lamps 2 and 5 are stably lit. As a result of this configuration, for example, even after one pulse-start discharge lamp 2' is started and lit before the inductance 3VC, the saturable reactance 9 has a high impedance with respect to the high voltage pulse, so The pulse-starting discharge lamp 5' can be reliably lit without the generated high-voltage pulse being absorbed by the series circuit of the starting current limiting capacitor 8 and the saturable reactance 9, and the pulse-starting discharge lamp 2 Since the impedance becomes low during stable lighting of '5', the input current at startup and the input current at no load can be reduced.

Furthermore, since pulse absorption is prevented by the saturable reactance of 9 VC and the pulse-start type discharge lamps 2', 5/ are reliably started, withstand voltage against high-voltage pulses is not a problem. Also, since it is a non-contact type, it is highly reliable. The power factor correction capacitor 7 can be connected as needed to reduce the input current during startup and during no-load conditions, and is not required. Some devices use a semiconductor switch or the like to separate the starting current limiting capacitor 8 from the circuit to prevent pulse absorption and ensure the discharge lamp starts. Since high voltage pulses are applied during the switch opening period, their withstand voltage becomes a problem, and
A detection circuit is required to drive them.

As described above, the discharge lamp lighting circuit of the present invention comprises a series circuit of an AC power source and a first pulse-starting discharge lamp connected across the AC power source and a first inductive current limiting impedance. a second pulse-started discharge lamp connected across the alternating current power supply in reverse order to the first pulse-started discharge lamp and the first inductive current-limiting impedance series circuit; A series circuit of a second inductive current-limiting impedance, the first pulse-starting discharge lamp, and a connection point of the first inductive current-limiting impedance and the second pulse-starting discharge lamp. Since it is equipped with a capacitive starting current limiting impedance consisting of a series circuit of a capacitor and a saturable reactance connected between the connection point of the second inductive current limiting impedance, the input at the time of starting is It is possible to reduce the current value and the input current at no-load, and also to ensure the starting of two pulse-start discharge lamps.Furthermore, it has a high withstand voltage and will not break down even when a high-voltage pulse for starting is applied. Since it is a non-contact type, it has the effect of being highly reliable.

[Brief explanation of the drawings] Figure 1 is a circuit diagram of a conventional discharge lamp lighting circuit, Figure 2 A and B
．． Figure C and Figure 3 A, B, and C are waveform diagrams of each part, respectively, Figure 4 is the conventional example Vc input current at the time of failure, input current at no load, and the starting current limit for the input current at stable time. A characteristic diagram of capacitor capacitance in impedance, FIG. 5 is a circuit diagram of an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... AC power supply, 2, 5... Pulse-start discharge lamp, 3, 4... Inductance, 8... Starting current limiting capacitor, 9... Saturable reactance.

Claims (1)

[Claims] 1 an alternating current power supply, a series circuit body of a first pulse-started discharge lamp and a first inductive current-limiting impedance connected across the alternating current power supply; a series circuit of a second pulse-start discharge lamp and a second inductive current-limiting impedance connected across the AC power supply in reverse order to the series circuit of the inductive current-limiting impedance; A capacitor and a capacitor connected between the connection point of the first pulse-start discharge lamp and the first inductive current-limiting impedance and the connection point of the second pulse-start discharge lamp and the second inductive current-limiting impedance. A discharge lamp lighting circuit comprising a capacitive starting current limiting impedance consisting of a series circuit of saturated reactance.