JPH04163889A - Discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To improve efficiency and make size smaller and weight lighter by lighting a discharge lamp using an LC parallel resonance circuit which becomes high impedance against a high voltage pulse for starting and becomes low impedance against low frequency rectangular wave current for lighting. CONSTITUTION:When the resonance frequency of an LC parallel resonance circuit Z is set to be equal to a high voltage pulse frequency generated by a pulse generator(PG), the circuit becomes high impedance against a high voltage pulse and low impedance against a low frequency rectangular wave. At starting time, the high voltage pulse being applied to a lamp (la) via condenser C2, which becomes low impedance against the pulse, from the PG, the circuit Z prevents the inflow to a rectangular wave source 1 so that the pulse is efficiently applied to the la. While during the lamp being lighted, the rectangular wave current being supplied to the la via the low impedance circuit Z, the inflow to the PG is prevented by the high impedance condenser C2. Thereby it is possible to improve efficiency and make size smaller and weight lighter.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a discharge lamp lighting device that includes a high-voltage pulse generator for starting and lights a discharge lamp in a rectangular wave.

[Prior Art] FIG. 10 shows a basic lighting circuit for a high intensity discharge lamp (HID lamp) (see Japanese Patent Application No. 164388/1988). A low-frequency rectangular wave power source containing many high-frequency ripple components due to the switching operation of a fribridge circuit or a half-bridge circuit is connected between terminals a and b. Ll
is a current-limiting inductor, L2 is an inductor that acts as a low-pass filter, and C5 is a capacitor that acts as a bypass filter. The high frequency ripple component is bypassed by the capacitor CI, and the low frequency rectangular wave component passes through the inductor L2, so that a rectangular wave current flows through the lamp 1a. Inductor L that limits this square wave current
In No. 1, the current-limiting impedance is determined by the frequency of the high-frequency ripple component, so the device can be made smaller and lighter.

Figure 11 shows a starting lighting circuit (see Japanese Patent Application No. 60-164387) in which a starter is added to the above lighting circuit.
An igniter IG is connected to the next winding. Pulse transformer PT, when starting, igniter 1. The high voltage pulse generated by G is boosted and applied to both ends of the lamp 1a via a capacitor C1 which acts as a bypass filter, and when lit, acts as a low pass filter to remove high frequency ripple components of the rectangular wave lamp current.

[Problems to be Solved by the Invention] In the circuit shown in FIG. 11, since a low frequency (several hundred Hz) rectangular lamp current flows through the secondary side of the pulse transformer PT,
The noise gets pretty loud. The number of turns of the secondary winding of the pulse transformer PT is limited by the step-up ratio of the primary and secondary voltages, so it is difficult to reduce it. Also, in order to improve efficiency, the winding of the pulse transformer PT must be made thicker, so the pulse transformer PT
.

becomes quite large in shape. Of course, the cost will also be higher.

Therefore, in order to solve the above problems, the 12th
As shown in the figure, it is conceivable to apply the output of the pulse generator PG to the lamp 1a via the capacitor C2.

In this circuit, when a pulse transformer is used as the pulse generator PG, the lamp current does not flow through the secondary side of the pulse transformer, making it possible to reduce noise and make the pulse transformer smaller in size. However, in this circuit, the high voltage pulse generated by the pulse generator PG is transmitted to the inductor L.
2. Since the voltage applied across the lamp 1a is divided by the inductor L2 and the pulse transformer, it is difficult to obtain a sufficient value. lamp 1a
Trying to get a high enough pressure pulse to start the
It is necessary to increase the impedance of inductor L2, and the shape of the pulse transformer becomes considerably large.
The cost will also be higher. Therefore, a circuit system was needed that could apply the high voltage pulses generated by the pulse generator PG to both ends of the lamp 1a without attenuating them.

The present invention has been made in view of the above points,
The purpose of this is to efficiently apply the high-voltage pulse for starting to the discharge lamp in a discharge lamp lighting device that is equipped with a high-voltage pulse generator for starting and lights the discharge lamp with a square wave. The goal is to achieve weight reduction.

[Means for Solving the Problems] In order to solve the above problems, the discharge lamp lighting device of the present invention has a pulse generator PG that generates a high-voltage pulse for starting, as shown in FIG. are connected in parallel between both ends of the discharge lamp βa via a capacitor C2 having a low impedance with respect to the high-voltage pulse, and a low-frequency rectangular wave power source and the discharge lamp ! An LC parallel resonant circuit is connected in series between the high-voltage pulse and the low-frequency rectangular wave power supply.

In the circuit shown in Fig. 1, the DC power supply VDC is switched by the switching circuit 1 to output a rectangular wave voltage containing many high frequency ripple components between points a and b, and this is connected to a low-pass voltage source consisting of an inductor L1 and a capacitor C1. By smoothing with a filter, a rectangular wave voltage with few high frequency ripple components is obtained between points c and b.

[Operation] In the circuit shown in Fig. 1, when the pulse generator PG generates a high voltage pulse at the time of starting, the lamp 1 is supplied via the capacitor C2.
A high voltage pulse is applied to a. Further, since the high voltage pulses that try to escape from the lamp 1a to the rectangular wave power source are blocked by the LC parallel resonance circuit, the high voltage pulses can be efficiently applied to the lamp Na. On the other hand, when lighting, the lamp 1a is supplied from the rectangular wave power source via the LC parallel resonant circuit.
A low frequency rectangular wave current flows through the circuit, but this rectangular wave current is blocked by the capacitor C2 and therefore does not flow into the pulse generator PG. Therefore, the pulse generator PG
There is no need to make the output winding thicker, making it possible to reduce the size and weight.

In the circuit shown in FIG. 2, a high voltage pulse generated by a pulse generator PG is applied to the discharge lamp 1th via two capacitors C2 and C1.

[Example 1] FIG. 3 is a circuit diagram of a first embodiment of the present invention.

The circuit configuration will be explained below. DC power supply V[]
c includes a series circuit of transistors Q, , Q2, and transistors Q3 . The series circuits Q, are connected in parallel. Transistor Q2. Q, has a diode D2. D, are connected in antiparallel. Transistor Q,,Q
2 connection point a and the transistor Q.

A series circuit of an inductor L1 and a capacitor C3 is connected between the connection point of Q4, and a series circuit of the HID lamp 1a on the LCC parallel resonant circuit is connected in parallel to both ends of the capacitor CI. The LC parallel resonant circuit 2 is configured by connecting an inductor Lb and a capacitor cb in parallel. A pulse generator PG is connected to both ends of the lamp Na via a capacitor C2.

Transistors Q,,Q2. Q3. Q operates as a low frequency square wave inverter. First, in the first period,
Transistor Q2. Q is off, transistor Q4 is on, and transistor Q1 is turned on and off at high frequency. When transistor Q1 is on, DC power supply VD
Current flows from C through transistor Q1, the load circuit between points a and b, and transistor Q (see broken line A in FIG. 3). When transistor Q is off, regenerative current flows to the load circuit via transistor Q4 and diode D2. Next, in the second period, the transistor Q,
,Q.

is off, transistor Q2 is on, and I/transistor Q3 is turned on and off at high frequency. Transista Q
3 is on, a current flows from the DC power supply VDC through the transistor Q3, the load circuit between I and A, and the transistor Q2. When transistor Q3 is off,
A regenerative current flows to the load circuit via I to transistor Q2 and diode D4.

Each current is smoothed by a low-pass filter consisting of an inductor L1 and a capacitor C1.
polarity, and in the second period, the DC voltage of the second polarity is at point e,
A rectangular wave voltage generated between points c and b and having one period equal to the alternating period of the first and second periods is obtained between points c and b.

FIG. 4 shows a circuit example of the pulse generator PG. DC power supply E
The capacitor C is charged via the resistor R1, and the charged charge is transferred to the triac 3 triggered by the control circuit 2.
Through the pulse transformer PT.

is discharged into the primary winding of the motor, and a high-voltage pulse is obtained at its secondary winding.

In this embodiment, the resonant frequency fLC on the LCC parallel resonant circuit constituted by the parallel connection of the capacitor cb and the inductor Lb is set to be approximately equal to the frequency fp of the high voltage pulse generated on the secondary side of the pulse transformer PT. Therefore, the LCC parallel resonant circuit has high impedance for high voltage pulses and low impedance for rectangular wave current. Therefore, the high voltage pulse generated on the secondary side of the pulse transformer PT during startup is almost blocked by the LC parallel resonance circuit 2, and the two ends of the pulse transformer PT are connected to both ends of this resonance circuit Z (between c and d). A voltage approximately equal to the next-side voltage will be applied. Therefore, the high voltage pulse is applied to the lamp 1a, as shown by the solid line B in FIG. 3, with almost no attenuation.

Note that since no high voltage pulse is applied between points a and b,
It will not destroy the semiconductor elements of the bridge circuit. Furthermore, since the capacitor C2 is inserted in series, almost no current flows through the secondary side of the pulse transformer PT when the lamp la is lit.

Furthermore, the inductor Lb also serves as a low-pass filter that removes ripples in the rectangular wave lamp current during lighting.

[Embodiment 2] FIG. 5 is a circuit diagram of a main part of a second embodiment of the present invention. This embodiment embodies the circuit shown in FIG. 2, and the high voltage pulse generated on the secondary side of the pulse transformer PT at the time of starting is transmitted to the discharge lamp 1 via two capacitors C, C2.
applied to a. The high voltage pulse generated on the secondary side of the pulse transformer PT at the time of startup is almost parallel resonance diagram Fl! ! z
It extends between both ends c and d. Further, since the capacitor C1 is a bypass filter and has a low impedance against high-frequency pulses, almost no voltage is applied to both ends of the capacitor C1. Therefore, the high voltage pulse is directly applied to the lamp 1th. Further, as in the first embodiment, since no high voltage pulse is applied between points a and b during startup, the semiconductor of the bridge circuit will not be destroyed. When the lamp la is turned on, the capacitor C2 cuts off the rectangular wave lamp current, and almost no lamp current flows through the secondary side of the pulse transformer PT.

In both the first and second embodiments, a single pulse may be generated on the primary side of the pulse transformer PT at the time of startup using a triac 3 as shown in FIG. Two or more pulses may be generated.

As a rectangular wave power supply, a full bridge system as shown in FIGS. 6 and 7, and a half bridge system as shown in FIG. 8 are very suitable. At points a, b, and c in Figures 6 to 8,
It is assumed that points a, b, and c of the circuit shown in the figure are connected to each other.

The circuits shown in FIGS. 6 to 8 will be explained below.

First, the circuit shown in FIG. 6 is a full-bridge type rectangular wave inverter circuit, and its configuration and operation are the same as those shown in FIG. 3.

The circuit shown in FIG. 7 is a combination of a step-down chopper circuit made up of a transistor Q5, a diode D, and an inductor L1, and a full-bridge low frequency inverter circuit made up of transistors Q6 to Q. Transistor Q5 of the step-down chopper circuit is always switching at a high frequency, and when transistor Q5 is on, current flows from the DC power supply Voc to the inverter circuit consisting of transistor Q5, l-transistors Q6 to Q, via inductor L1, and transistor Q When , is off, inductor L
A storage energy key of 1 causes current to flow through the inverter circuit through the diode D5. In this inverter circuit, during the first operation period, the transistors Q6, Q, are turned on, and the transistors Q, , Q7 are turned off, and during the second operation period, the transistors Q8, . The transistor Q is controlled so that it is turned on and the transistors Qa and Qs are turned off. The first operating period and the second operating period are alternately repeated at low frequency. Therefore, during the first operation period, a sawtooth current flows from point C to point C, and during the second operation period, a similar current flows from point C to point C. Note that obtaining a rectangular wave current from a sawtooth current using a low-pass filter is the same as in each of the embodiments described above.

Figure 9 shows a half-bridge type rectangular wave inverter circuit, with a capacitor c connected to the DC power supply VDC.4. A series circuit of cS and a series circuit of transistors Q+o+Qz were connected in parallel, and a load circuit 71@ was connected between the connection point a of capacitors C+ and Cs and the connection point of transistors Q + o + Q + +. It is something. 1 to transistor Q + o + Q11 has diode Dlo, I) 11
are connected in antiparallel. During the first operation period, transistor Q I O switches at high frequency, and transistor Qll is in an off state. Further, during the second operation period, the transistor Q11 switches at high frequency, and the transistor Q + o is turned off. This first
The operation period and the second operation period are alternately repeated at low frequency. Therefore, during the first operation period, the point a
During the second operation period, a sawtooth current flows in the direction from point a to point a. Note that obtaining a rectangular wave current from a sawtooth current using a low-pass filter is the same as in the above embodiment.

In each of the above embodiments, the switching transistor is not limited to a bipolar transistor, but also a power MO
A 3FET may also be used.

"Effects of the Invention" As described above, in the present invention, a pulse generator that generates a high-voltage pulse for starting is connected between both ends of a discharge lamp via a capacitor that has a low impedance with respect to the high-voltage pulse. An LC parallel connected in parallel between the low frequency rectangular wave power source and the discharge lamp, which has a high impedance to the high voltage pulse and a low impedance to the current from the low frequency rectangular wave power source. Because the resonant circuits are connected in series, the high-voltage starting pulse output from the pulse generator can be efficiently applied to the discharge lamp during startup, making the pulse generator smaller and lighter. In addition, the capacitor connected in series with the pulse generator prevents the rectangular wave lamp current from flowing into the pulse generator during lighting.
This has the effect of reducing noise from the pulse generator.

[Brief explanation of drawings]

Figures 1 and 2 are circuit diagrams showing the basic configuration of the present invention, Figure 3 is a circuit diagram of the first embodiment of the present invention, Figure 4 is a circuit diagram of the same essential parts, and Figure 5 is a circuit diagram of the present invention. Main part circuit diagram of the second embodiment of
6 to 8 are circuit diagrams showing various circuit examples of the rectangular wave power source used in the present invention, FIG. 9 is a circuit diagram of a load circuit used in the same, FIG. 10 is a circuit diagram of a conventional example, and FIG. The figure is a circuit diagram of another conventional example, and FIG. 12 is a circuit diagram of still another conventional example. Z is an LC parallel resonant circuit, C2 is a capacitor, la is a lamp, and PG is a pulse generator.

Claims (1)

[Claims] (1) A pulse generator that generates high-voltage pulses for starting,
A capacitor is connected in parallel between both ends of the discharge lamp via a capacitor that has a low impedance with respect to the high-voltage pulse, and has a high impedance with respect to the high-voltage pulse between a low frequency rectangular wave power source and the discharge lamp. A discharge lamp lighting device comprising an LC parallel resonant circuit connected in series and having a low impedance to the current from the low frequency rectangular wave power source.