JPH01217894A - Discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To facilitate effective supply of both high frequency power and DC power without instability in arc, in a lighting device for supplying alternately the high frequency power and DC power by setting the frequencies of both high frequency power and DC power at respective desired values. CONSTITUTION:A high voltage discharge lamp 1a is supplied alternately with a high frequency power having a frequency of fPH via a high frequency generation circuit 2, and a DC power interrupted at a frequency of fDC. The high frequency generation circuit 2 is connected to the primary coil L31 of a transformer Tf, while the secondary coil L32 of the transformer Tf, a capacitor C1 and a discharge lamp 1a form a closed circuit. A switching transistor Q1 for the DC power, a capacitor C1 and an inductance element L1 are connected together in series. By making frequency fHP higher than frequency fDC, and fDC higher than the resonance frequency fLC between the capacitor C1 and the inductance element L1, generation of arc instability due to the high frequency component is eliminated, and the high frequency power and the DC power are effectively supplied.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a discharge lamp lighting device for lighting a high-pressure discharge lamp by switching a semiconductor switching element at high frequency.

[Prior Art] A discharge lamp lighting device that uses a commercial power source has a low operating frequency, so the dimensions and weight of components such as an inductance element, a transformer, and a capacitor that constitute the lighting device are large. Therefore, as a means to reduce the size and weight of the lighting device,
2. Description of the Related Art High-frequency lighting systems have been proposed. For example, high-frequency lighting devices using switching transistors and the like have already been put into practical use in lighting devices for fluorescent lamps. On the other hand, if the lighting frequency of a high-pressure discharge lamp lighting device is set to a high frequency, the lighting device can be made smaller and lighter in the same way as in the case of fluorescent lamps, but when a high-pressure discharge lamp is lit at a high frequency, so-called acoustic resonance phenomenon It has been known that arc instability occurs due to

When the frequency of this acoustic resonance phenomenon is gradually increased, the arc gradually becomes more stable, but in order to completely stabilize the arc, a very high frequency of, for example, 200 kHz or higher must be used. This increases noise, switching loss, etc. Therefore, in practice, it is extremely difficult to continuously supply power to a high-pressure discharge lamp using such a frequency. Therefore, it is possible to consider a method of finding a frequency at which the arc is stable from 20 to 50 kHz, which is a frequency that is easy to use in practice, and lighting the lamp using that frequency. The frequency at which the arc becomes stable varies depending on the type of lamp, and the frequency at which the arc becomes stable varies depending on variations between high-pressure discharge lamps even if the type and wattage are the same. Therefore, it is difficult to ensure that the arc is stable, and circuit design is difficult. It becomes very difficult.

Therefore, in order to take advantage of the advantages obtained by lighting high-pressure discharge lamps at high frequencies, power in a frequency band in which no acoustic resonance phenomenon occurs and power in a frequency band in which an acoustic resonance phenomenon may occur are divided at a predetermined period. A lighting device has been proposed that alternately supplies power to high-pressure discharge lamps.
No. 8663). This conventional example is shown in FIG. 8. The lighting device of FIG. 8 uses a DC generating circuit 1 as a power source in a frequency band where no acoustic resonance phenomenon occurs, and a power source in a frequency band where acoustic resonance phenomenon can occur. The high frequency generation circuit 2 is used as the RF generator. The DC generation circuit 1 consists of a series circuit of a DC power supply V1 and a transistor Q, and its output terminal is connected to the high pressure discharge lamp 1a via a resistor R serving as a current limiting element. The high frequency generation circuit 2 includes a DC power supply V2, a series circuit of transistors Q a and Q b, and capacitors Ca and C.
It consists of series circuits b connected in parallel, and transistors Qa,
A high pressure discharge lamp la is connected via a current limiting impedance Z between the connection point of Qb and the connection point of capacitors Ca and Cb. Diodes Da and Db are connected in antiparallel between the collector and emitter of each transistor Qa and Qb, respectively. The current limiting impedance Z consists of a series circuit of an inductance element Lo+ and a capacitor C0l.

FIG. 9 is a waveform diagram of the lamp current Ila flowing through the high pressure discharge lamp 1a in the above circuit. The transistor Q is turned on during the DC operation period T'oc from time t to t2, and is connected to the high-pressure discharge lamp through the resistor R! DC current engineering l).

During the high-frequency operation period THF, the transistor Q is turned off and the transistors Q a and Q b are alternately turned on, causing a high-frequency current IMF to flow through the high-pressure discharge lamp 1a through the current-limiting impedance Z. Operating period T
By appropriately selecting the ratio between Dc and THF during the high frequency operation period, it is possible to prevent the occurrence of acoustic resonance phenomena and to stabilize the arc.

[Problems to be Solved by the Invention] However, in the above-mentioned conventional technology, since the current limiting element for the DC component is the resistor R, there is a problem in that the power loss is large and the circuit efficiency is significantly reduced. . Therefore, it is conceivable to use a chopper circuit to switch the DC power supply voltage, to intermittently flow a DC current to a 1m high-pressure discharge lamp, and to limit the intermittent DC current with an inductance element. If the frequency component is superimposed on the DC component IDC of the discharge lamp current 11a and the amount included as ripple increases, the lamp power will pulsate at a high frequency, causing an acoustic resonance phenomenon and leading to instability of the arc. Sometimes. Furthermore, when the high frequency power generated by the high frequency generation circuit flows into the LC circuit of the chopper circuit, there is a problem in that the high frequency power supplied to the high pressure discharge lamp decreases, resulting in a decrease in efficiency.

The present invention has been made in view of the above points, and its purpose is to solve the problem of arc instability due to high frequency components in a discharge lamp lighting device that alternately supplies high frequency power and DC power to a high pressure discharge lamp. The object of the present invention is to efficiently supply high frequency power and DC power without causing any problems.

[Means for Solving the Problems] In the present invention, in order to solve the above problems, the first
As shown in Figures 3 to 3, the high pressure discharge lamp lIL and the first
A high-frequency generating circuit 2 that generates a high-frequency wave with a frequency fHF, a transformer Tf having a primary winding L31 connected to the output of the high-frequency generating circuit 2, and a secondary winding L of the transformer Tf are connected to a high-pressure discharge lamp. Capacitor C1 connected to form a closed circuit
, an inductance element connected in series with the capacitor CI, and a switching element (transistor Q,) that supplies DC power intermittent at a second frequency fDc to the series circuit of the capacitor CI and the inductance element L1.
In the lighting device, the lighting device is configured to alternately switch between a DC operation wI interval TDc in which only the switching element operates at the second frequency fDc and a high frequency operation period T) IF in which at least the high frequency generation circuit 2 operates. 1 frequency fHF is higher than the second frequency fDc, and the second frequency rpc is set to the capacitor CI and the inductance element L.
The resonant frequency fLc is higher than the resonant frequency fLc of 1.

[Function] In the present invention, as a current limiting element for DC power,
Since the inductance element L+ can be used in place of the resistance element, loss is reduced and efficiency is improved. Also,
During the high frequency operation period THE during which the high frequency generation circuit 2 operates, high frequency power is supplied to the high pressure discharge lamp 1a, so the transformer Tf of the lighting device can be made smaller and lighter. Here, in order to effectively supply high frequency power to the high pressure discharge lamp 1a during the high frequency operation period THF, the capacitor CI
Reduce the impedance (1/2πfHFce) of
The impedance 2πfHFL+ of the inductance element L1 connected in series with the capacitor CI must be increased. If the impedance 2πfHpL+ of the inductance element L1 is too small, the high frequency power generated in the secondary winding L32 of the transformer Tf will leak through the inductance element L1 and cannot be effectively supplied to the high pressure discharge lamp 1a. On the other hand, during the DC operation period T'oc, it is necessary to supply DC power through the inductance element LI, so the impedance 2πfDcLl of the inductance element L1 during the DC operation period TDC is equal to the impedance 2πfDcLl of the inductance element during the high frequency operation period THF. , must be smaller than the impedance 2πfHFLI.

Therefore, it is necessary to satisfy fDc<fHF. That is, in the present invention, by satisfying the condition fDc<fHF, there is an effect of increasing the efficiency of supplying high frequency power and DC power to the high pressure discharge lamp 1a.

In addition, the switching frequency fDc during the DC operation period TDc is determined by the resonance frequency fLc of the inductance element L1 and the capacitor C3 (= 1 / 2 r (L + ・C
+)" If it is lower than 2), the circuit becomes capacitive, the oscillating current becomes a phase advance mode, and the stress on the switching element increases. On the other hand, as in the present invention, the switching frequency rpc in the DC operation period TDc When is made higher than the resonant frequency fLc, the circuit becomes inductive, so
The oscillating current becomes a slow phase mode, which has the effect of reducing stress on the switching element.

[Embodiment 1] FIG. 2 is a circuit diagram of the first embodiment of the present invention, and FIG. 3 is an operating waveform diagram thereof. The collector of transistor Q is connected to the positive terminal of DC power supply ■1, and
One end of an inductance element is connected to the emitter of . Diode D is connected to the negative terminal of DC power supply ■1.
The anode of the diode D0 is connected to the anode of the diode D0, and the cathode of the diode D0 is connected to the emitter of the transistor Q1. A step-down chopper circuit is formed by six or more circuits in which a smoothing capacitor C3 is connected between the other end of the inductance element and the negative terminal of the DC power supply V. A high-pressure discharge lamp 1a is connected to both ends of the capacitor C1 via a secondary winding L+2 of a transformer Tf. The high frequency generation circuit 2 includes switching transistors Q a and Q b, and generates a high frequency voltage, similar to the circuit shown in FIG. The output of the high frequency generation circuit 2 is connected to the primary winding Lff+ of the transformer Tf via an inductance element L2.
is applied to. A capacitor C3 is connected in parallel to the primary winding L31 of the transformer Tf. Transistor Q.

is on during the DC operation period TDc from time t to t2.
OFF operation, inductance element, and transformer Tf
A direct current I is applied to the high pressure discharge lamp 1a through the secondary winding L3□ of
Run DC.

First, when the transistor Q is on, the positive terminal of the DC power supply v1 is connected to the transistor Ql and the inductance element L.
1. High pressure discharge lamp 1a, secondary winding L of transformer '17f)
2, a current flows in a path leading to the negative terminal of the DC power supply V1. Furthermore, when the transistor Q1 is turned off, the energy stored in the inductance element R causes the inductance element R to be turned off by the high-pressure discharge lamp 1a and the transformer T.
Current flows through the next winding L)2, through the diode D0, through the inductance element, and back to the inductance element. Thereafter, this series of operations is repeated, and the high pressure discharge lamp 1a is supplied with a DC power supply ■.

A positive DC voltage obtained by stepping down the voltage is applied. This DC voltage has a switching frequency rp of the transistor Q1.
Contains a high frequency ripple component of c.

Next, during the high-frequency operation period THE from time 2 to t3, the transistor Q1 is turned off, and the transistors Q a and Q b are turned on alternately at high frequency, and the primary of the transformer T is connected via the inductance element L2. Winding L
A high frequency current is applied to 31. Secondary winding L3 of transformer Tf
The high frequency voltage generated at 2 is applied to the high pressure discharge lamp 1a via the capacitor C1. By appropriately selecting the ratio between the DC operation period TDo and the high frequency operation period TH,
The occurrence of acoustic resonance phenomenon can be prevented and the arc can be stabilized.

The capacitor C5 and the inductance element R constitute a smoothing filter circuit, and during the DC operation period TDC, the high frequency ripple component IR included in the DC component I DC
In addition to reducing P, the high frequency component IHF is connected to the diode D during the high frequency operation periods T, , F. , has the effect of preventing wasteful consumption via the inductance element L1. In this embodiment, as shown in FIG. 1, the switching frequency fl-IF in the high frequency operation period THF is set higher than the switching frequency roe in the DC operation period TDc, so that the inductance for the high frequency component IMF is Since the impedance of the element 1 is high and the impedance of the capacitor CI is low, the high frequency component IHF is effectively supplied to the high pressure discharge lamp 1a. In addition, as shown in FIG. 1, the switching frequency fDc during the DC operation period T'oc is changed to the resonance frequency f of the inductance element L1 and the capacitor C1.
Since it is set higher than Lc (= 1 / 2 re (L, C1)""), the oscillating current generated in the first LC circuit 3 due to the switching of the transistor Q becomes a slow phase mode, and the switching transistor The stress on Q is reduced.

Although the present invention does not limit the configuration of the high frequency generation circuit 2, when the high frequency generation circuit 2 is composed of a switching circuit as shown in FIG. 8, the oscillating current generated in the second LC circuit 4 is also slow. To set the phase mode, the switching frequency rHF of the transistors Q a and Q b is set to the resonant frequency hc' = 1/2 of the second LC circuit 4.
It is sufficient to set it higher than π((L 2+ L 31) ・C2)/2. This makes it possible to reduce the stress on all transistors Q + , Q a , and Q b of the lighting device.

Further, in this embodiment, the transistor Q is in an inoperative state during the high frequency operation period THF, but the transistor Q may also be made to operate during the high frequency operation period THF. The waveform is a waveform in which the high frequency component IHF is superimposed on the DC component IDC, so the amplitude on the positive side in the high frequency operation period THF becomes high.

[Example 21 FIG. 4 is a circuit diagram of a second embodiment of the present invention.

One end of the high-pressure discharge lamp 1a is connected to the positive terminal of the DC power supply 1 through the collector-emitter of the transistor Q1 and the inductance element L1, and the other end of the high-pressure discharge lamp 1a is connected to the secondary winding of the transformer Tf. , 2 to the negative terminal of the DC power supply v1. High pressure discharge lamp 1a and transformer T
A capacitor CI is connected in parallel to the series circuit of the secondary winding L32 of f.

The collector-emitter of a transistor Q2 is connected between the emitter of the transistor Q1 and the negative terminal of the DC power supply V1. Transistor Q,,Q.

A diode D is connected between the collector and emitter of each
+ and D2 are connected in antiparallel. A primary winding L31 of a transformer T' is connected between the collector and emitter of the transistor Q2 via a capacitor C2 and an inductance element L2.A primary winding L31 of a transformer Tf is connected between the collector and emitter of the transistor Q2.
A capacitor C1 is connected in parallel to 3H. In this circuit, the first LC circuit 3 surrounded by a broken line is
The second LC circuit 4 surrounded by a dashed line has a low impedance during the high-frequency operation period THF, and is a smoothing filter circuit for supplying DC power to the high-pressure discharge lamp. This is a high frequency generation circuit that serves as an impedance and supplies high frequency power to the high pressure discharge lamp 1a via the transformer T.

FIG. 5 shows the operations of transistors Q and Q2 in this embodiment. In the same figure, 'T'oc is the DC operation period in which the first LC circuit 3 operates, and THF is the second L
This is a high frequency operation period in which the C circuit 4 operates. In this embodiment, transistor Q is turned on at high frequency throughout the period.
Performing off operation.

Transistor Q2 performs on/off operation at high frequency only during high frequency operation period THF, and during DC operation period T
At Dc, it remains off.

First, during the DC operation period TDc, the transistor Q
2 remains off, there is no discharge path for the capacitor C2, the primary winding L31 of the transformer Tf has almost no effect, and the transistor Q1 turns on and off, causing the high-pressure discharge lamp to flow through the inductance element Ll. Supply DC power to Muhe. When the transistor Q1 is on, a current flows in a path from the positive terminal of the DC power supply 1 to the negative terminal of the DC power supply V1 via the transistor Q3, the inductance element 3, the high-pressure discharge lamp 1a, and the secondary winding L+2 of the transformer Tf. flows. When transistor Q1 is off, inductance element L1 becomes a power source, and inductance element L
1 to high pressure discharge lamp 1a, secondary winding L32 of transformer Tf
, a current flows through the inductance element through the diode D2 and back to the inductance element. Each current is also shunted to a capacitor C1 connected in parallel to the series circuit of the high-pressure discharge lamp 1g and the secondary winding L32 of the transformer Tf. The capacitor C3 is connected to bypass the high-frequency components flowing through the inductance element L1, and therefore, a direct current with few high-frequency components can flow through the high-pressure discharge lamp 1h.

Next, during the high frequency operation period THF, the transistors Q1 and Q2 are alternately turned on and off at high frequency after a predetermined dead time, and the high pressure discharge lamp 1
Supplies high frequency power to m. Hereinafter, the operation for one cycle of high frequency will be explained in four cases.

■When transistor Q is on and transistor Q2 is off, the positive terminal of DC power supply ■ is connected to transistor Q1.
, a current flows through a path leading to the negative terminal of the DC power supply (1) via the capacitor C2, the inductance element L2, and the primary winding Lat of the transformer Tf.

■When transistors Q, , Q2 are both turned off, inductance element L2 and primary winding Lffl of transformer Tf
Due to the stored energy, a current flows from the inductance element L2 through the primary winding L31 of the transformer Tf, the diode D2, and the capacitor C2, and returns to the inductance element L2.

■When transistor Q is off and transistor Q2 is on, capacitor C2 becomes a power source, and capacitor C
2 charges are applied to the transistor Q2, the primary winding L31 of the transformer Tf, and the inductance element.

is discharged through.

■When both transistors Q and Q2 are turned off, energy stored in the inductance element L2 and the primary winding Ls+ of the transformer Tf causes the inductance element L2 to
A current flows through a path returning to the inductance element L2 via the capacitor C2, the diode L, the DC power supply V5, and the primary winding LSI of the transformer Tf.

Hereafter, by repeating the same operation, the transformer Tf
Current flows alternately in the opposite direction through the primary winding LSI, and a high frequency voltage is generated in the secondary winding 2. This high frequency voltage is applied to the high pressure discharge lamp 1a via the capacitor C1.

During this high frequency operation period T)(F, the magnitude of the current flowing through the inductance element L1 is the magnitude of the current flowing through the inductance element L1, the capacitor C1, and the secondary winding L32 of the transformer Tf.
Although it changes depending on the constant of , switching frequency fHF, etc., in this embodiment, the current flowing through the inductance element is reduced during the high frequency operation period THE.
Switching frequency fH during high frequency operation period THF
F is the switching frequency r during the DC operation period TDc
It is set higher than oc. Further, the capacitor C3 forms a low impedance closed circuit for easily supplying the high frequency voltage output from the secondary winding L32 of the transformer Tf to the high pressure discharge lamp 1a. In other words, the high frequency current is not passed through the inductance element, and the capacitor C3 is
is supplied to the high-pressure discharge lamp 1a via the.

As described above, in this embodiment, the transistor Q.

By operating the circuit in both the DC operation period TDc and the high frequency operation period THE, the circuit configuration can be simplified. In this circuit, the waveform of the discharge lamp current 11a flowing through the high-pressure discharge lamp 1& is the same as the waveform shown in FIG.

Further, as described above, each circuit element effectively acts on the operation during the rainy period. That is, during the DC operation period TDo, the capacitor C2 bypasses the high frequency to reduce the content of the high frequency component of the current flowing through the high pressure discharge lamp 1a. Therefore, during the DC operation period, the discharge lamp current 11a is mostly a DC component, which is a stable component that can suppress instability of the arc due to the acoustic resonance phenomenon. Furthermore, during the high frequency operation period THF, the capacitor C1 forms a closed circuit as described above and has the role of efficiently applying high frequency to the high pressure discharge lamp la. Transformer Tf 2
The next winding L32 blocks high frequency components during the DC operation period TDc to facilitate bypass of high frequencies to the capacitor C1, and acts as a high frequency power source during the high frequency operation period THE. Further, the inductance element L1 acts as a smoothing choke during the DC operation period TDc, and acts as a high frequency block filter during the high frequency operation period THF.

[Third Embodiment] FIG. 6 is a circuit diagram of a third embodiment of the present invention, and FIG. 7 is an operating waveform diagram thereof. This embodiment uses a half-bridge circuit as a switching circuit. A series circuit of transistors Q, , Q, and capacitors C, , C, are connected to both ends of the DC power supply ■1.

series circuits are connected in parallel. transistor Q,
, Q2, a series circuit of diodes Dz+D+2 and a series circuit of diodes Dz++Dzz are connected in parallel. Between the connection points of the diodes D, , D, and □ and the connection points of the capacitors C= and C5, there is a circuit in which a capacitor C2 is connected in parallel to a series circuit of the high-pressure discharge lamp 1a and the secondary winding L32 of the transformer Tf. is an inductance element and is connected through.

A diode D1 is connected in antiparallel between the connection point of the diodes Dll, D12 and the collector of the transistor Q1, and a , diode D2
are connected in antiparallel. In addition, the diode D 2 +
A diode D is connected in antiparallel between the connection point of diodes D 21 and D 2 and the collector of the transistor Q1, and a diode D is connected between the connection point of the diodes D 21 and D 2□ and the emitter of the transistor Q2. are connected in antiparallel. One end of the primary winding Lco1 of the transformer T is connected to the connection point of the capacitors C, , C, and the other end is connected to the diode D21, D2□ through a series circuit of the inductance element L2 and the capacitor C2. Connected to the dots.

Each of the capacitors C, , CS is charged by a DC power supply (1). Transistors Q, Q2 both perform switching operations at high frequencies, and the supply of rectangular wave power is achieved by performing a chopper operation during the DC operation period TDc from time t1 to t2 and from time ta to t in FIG. be done.

First, from time 1+ to t2, transistor Q2 remains off. In this state, when transistor Q is turned on, capacitor C4 is connected to transistor Q, diode DI1, and inductance element LI.
, the high-pressure discharge lamp la, and the secondary winding Lco2 of the transformer Tf, a current flows in a path returning to the capacitor C4. When the transistor Q is turned off, the energy stored in the inductance element R causes the inductance element R to
A current flows through the high-pressure discharge lamp 1a, the secondary winding L32 of the transformer Tf, the capacitor C5, and the diode D2, and returns to the inductance element L1. The high frequency components of each current are shunted to the capacitor C1, and a positive direct current flows through the high pressure discharge lamp 1a.

Next, at times t to t4, the transistor Q1 remains off. In this state, when transistor Q2 is turned on, transformer T
A current flows in a path returning to the capacitor C2 via the secondary winding Lff2 of f, the high-pressure discharge lamp in, the inductance element L1, the diode DI2, and the transistor Q2. When the transistor Q2 is turned off, the energy stored in the inductance element L1 causes a current to flow through the inductance element through the diode D1, the capacitor C1, the secondary winding L32 of the transformer Tf, and the high-pressure discharge lamp 1a, and return to the inductance element LI. flows. The high frequency components of each current are shunted to the capacitor C1, and a negative direct current flows through the high pressure discharge lamp 1a.

Switching frequency r during this DC operation period TDc
Since pc is higher than the resonant frequency fLc of the inductance element L1 and capacitor C1, the oscillating current becomes the slow phase mode as described above, and the switching transistor Q
1. It is possible to prevent stress from being applied to Q-.

In FIG. 7, the high-frequency power is supplied from time t2 to time t,
This is achieved by performing an inverter operation during the high frequency operation period THF from time t4 to time t5. During this high frequency operation period THE, transistors Q1 and Q2 are alternately turned on and off. When transistor Q1 is on and transistor Q2 is off, the DC power supply ■1 supplies transistor Q1, diode D21, capacitor C2, inductance element L2, primary winding L+ of transformer Tf, etc.
A current flows through the capacitor C6 and returns to the DC power source 1. Transistor Q1 is off and transistor Q
2 is turned on, the DC power supply V, to the capacitor C4,
Primary winding L31 of transformer Tf, inductance element L
2. Current flows through the path returning to the DC power supply V via the capacitor C2, diode D22, and transistor Q2.

Hereafter, by repeating the same operation, the transformer Tf
Current alternately flows in the opposite direction through the primary winding L31, and a high frequency voltage is generated in the secondary winding L'+2. This high frequency voltage is applied to the high pressure discharge lamp 1a via the capacitor C1.

In this embodiment, since the switching frequency rHF during the high frequency operation period THF is set higher than the switching frequency rpc during the DC operation period T'oc, the high frequency current during the high frequency operation period THF is blocked by the inductance element L1. Therefore, almost no current flows in the first LC circuit 3. Also, during the DC operation period TDc, current flows only in one direction of the capacitor C2, so there is no discharge path for the capacitor C2, and the second LC circuit 4 Almost no current flows through. Note that the first LC circuit 3
The current flowing between the diodes D + +, D +□, p211D2□, and D
, , blocked by D4.

In this embodiment, the waveform of the discharge lamp current Ila as shown in FIG. 7 is obtained by alternately repeating one or more DC operation periods TDc and high frequency operation periods THF.
Since the polarity of the DC component IDC is periodically alternated, it is possible to prevent only one electrode of the high-pressure discharge lamp 1a from being consumed, and the life of the high-pressure discharge lamp 1a can be extended.

[Effects of the Invention] As described above, in the present invention, the secondary winding of the transformer that outputs the high frequency of the first frequency is connected to the high pressure discharge lamp via the capacitor to form a closed circuit, Through an inductance element connected in series with this capacitor, DC power that is intermittent by a switching element at a second frequency is supplied, and a high frequency operation period in which a high frequency wave of at least the first frequency is output and a second In a lighting device that alternately switches between a DC operating period in which only the switching element operates depending on the frequency, the first frequency is set higher than the second frequency, so that an inductance element acts as a smoothing choke during the DC operating period. The impedance of the capacitor becomes higher during the high frequency operation period and acts as a high frequency blocking filter, and together with the lower impedance of the capacitor, high frequency power can be efficiently supplied to the high pressure discharge lamp. Further, since DC power is supplied by a switching operation and the inductance element is used as a current limiting element, circuit loss is reduced compared to the case where a resistive element is used as a current limiting element. Therefore, it is possible to obtain a lighting device with stable arc and high efficiency. Furthermore, since the second frequency at which the switching element operates is set higher than the resonant frequency of the capacitor and inductance element, the oscillating current flowing through the circuit becomes a slow phase mode, which has the effect of reducing stress on the switching element.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the operation of the present invention, Fig. 2 is a circuit diagram of the first embodiment of the invention, Fig. 3 is an operation waveform diagram of the same as above, and Fig. 4 is a circuit diagram of the second embodiment of the invention. , FIG. 5 is an operating waveform diagram of the same as above, FIG. 6 is a circuit diagram of the third embodiment of the present invention, FIG. 7 is an operating waveform diagram of the same as above, FIG. 8 is a circuit diagram of the conventional example, and FIG. It is an operation waveform diagram same as the above. ! a is a high-pressure discharge lamp, Tf is a transformer, Li+ is a primary winding, L3 is a secondary winding, C1 is a capacitor, L is an inductance element, 2 is a high frequency generation circuit, Q + +Q2 is a transistor, THE is a high frequency During the operation period, TDc is the DC operation period, fHF is the switching frequency during the high frequency operation period, roc is the switching frequency during the DC operation period, and fLc is the resonance frequency.

Claims (1)

[Claims] (1) A high-pressure discharge lamp, a high-frequency generating circuit that generates a high-frequency wave of a first frequency, a transformer with a primary winding connected to the output of the high-frequency generating circuit, and a secondary winding of the transformer in a high-pressure discharge lamp. A capacitor that is connected to form a closed circuit, an inductance element that is connected in series with the capacitor, and a switching element that supplies DC power that is intermittent at a second frequency to the series circuit of the capacitor and the inductance element, In a lighting device that alternately switches between a DC operation period in which only a switching element operates at a second frequency and a high frequency operation period in which at least a high frequency generation circuit operates, the first frequency is set higher than the second frequency. A discharge lamp lighting device characterized in that the second frequency is higher than the resonance frequency of the capacitor and the inductance element.