JP4088926B2 - Discharge lamp lighting device - Google Patents

Description

  The present invention relates to a discharge lamp lighting device for lighting a discharge lamp with high-frequency power from a self-excited inverter circuit, and in particular, includes a preheating timer circuit for a filament and a protection circuit for protecting the circuit from abnormalities due to the end of the life of the discharge lamp. The present invention relates to a discharge lamp lighting device.

In the prior art relating to the preheating timer circuit for the filament of the discharge lamp, when starting the discharge lamp, the oscillation frequency of the transistor of the inverter circuit is made higher than during normal lighting and the output voltage is made lower. When increasing the oscillation frequency, the transistor is turned on to reduce the load of the control winding of the output control means. When starting, the voltage of the discharge lamp is detected by the lamp voltage detecting means and integrated by the time constant circuit. When the charge accumulated in the capacitor rises above the voltage set by the Zener diode, the Zener diode is turned on. The transistor is turned off and the load of the control winding is increased so that the normal voltage is obtained, and the output control means lowers the oscillation frequency of the transistor of the inverter circuit and increases the output voltage.
(For example, Patent Document 1)

  Further, in the related art relating to a protection circuit for protecting a circuit against an abnormality at the end of the life of a discharge lamp, a rectifying / smoothing circuit for rectifying and smoothing an AC power source and two switching elements connected between output terminals of the rectifying / smoothing circuit A self-excited inverter circuit including a load circuit including a current transformer connected to both ends of the switching element, a smoothing capacitor charged by a current generated in the secondary winding of the current transformer, and a smoothing circuit An end-of-life detection circuit having a Zener diode that monitors the voltage across the capacitor, and an end-of-life holding circuit that holds the output suppression state of the inverter circuit when an abnormal state is detected. (For example, Patent Document 2)

JP-A-5-82270 (paragraphs 0030-0036, FIG. 1) JP 2001-93690 A (paragraphs 0026-0033, FIGS. 1 to 3)

  According to the circuit diagram showing the embodiment of the invention of FIG. 1 of Patent Document 1, the oscillation frequency of the inverter circuit (discharge lamp lighting means in Patent Document 1) during preheating and lighting is controlled by the transistor of the output control means. This is done by turning the control winding on or off to reduce or increase the load on the control winding. However, when a plurality of discharge lamps can be mounted on the load circuit, a combined current of the plurality of discharge lamps flows through the current transformer, and a plurality of voltages electromagnetically coupled to the current transformer are also present. Will be affected by the combined current of the discharge lamp. In particular, in the case of a lighting device capable of so-called thinning-out lighting that allows a plurality of discharge lamps to be mounted on the load circuit and can be lit without mounting all the discharge lamps, 1 There was a problem that the circuit constant of the output control means was not the same when the lamp was mounted and when multiple lamps were mounted.

  According to the circuit diagrams showing the embodiments of the invention of FIG. 1 and FIG. 2 of Patent Document 2, a secondary of a current transformer in which a signal for identifying and detecting normal and end-of-life currents of a discharge lamp is connected to a load circuit. The voltage of the smoothing capacitor is charged by the current generated in the winding. However, when a plurality of discharge lamps can be mounted on the load circuit, the voltage of the capacitor C5 becomes a detection signal obtained from the combined current of the plurality of discharge lamps, so that it is difficult to reliably detect the end of life. there were. In particular, when it is possible to mount a plurality of discharge lamps in the load circuit, and in the case of a lighting device capable of so-called thinning-out lighting that enables lighting without mounting all the discharge lamps, it is normal. Since the load current value is not constant, there is a problem that the method of Patent Document 2 cannot cope with.

  Further, since the filament preheating timer circuit and the end-of-life protection circuit of the discharge lamp are formed of independent and independent circuits, there is a problem that the shape is large and expensive.

  The present invention has been made to solve the above-described problems of the conventional apparatus, and a first object of the present invention is to provide a filament preheating timer circuit for preheating a filament of a discharge lamp for a certain period when the power is turned on, An object of the present invention is to provide a small and inexpensive discharge lamp lighting device sharing a part of a protection circuit for stopping the discharge lamp lighting device at the end of the life of the discharge lamp.

  In addition, a second object of the present invention is to provide a discharge lamp that can detect the end of life under the same detection conditions as when all the discharge lamps are mounted even if any of the plurality of discharge lamps is removed. An object is to provide a lighting device.

A discharge lamp lighting device according to the present invention comprises a DC power supply, an inverter circuit comprising a half bridge circuit having two switching elements for converting a DC supplied from the DC power supply into a high-frequency current, and two secondary windings. A choke coil having a series circuit of a coupling capacitor connected to the choke coil via a discharge lamp, wherein the two secondary windings are connected to the two switching elements via resistors, while alternately oN / oFF control of two switching elements, a plurality of lamp load circuit for lighting the discharge lamp by a high frequency current from the inverter circuit, and each provided in the choke coil of the discharge lamp load circuits 2 Occurs in each secondary winding connected to any one of the two secondary windings. A peak-to-peak voltage detection circuit that detects each voltage between peaks, and a period from when the power source is turned on to when the discharge lamp is started and turned on, with a voltage obtained by wired-oring the detected peak-to-peak voltage detected by the peak-to-peak voltage detection circuit. A preheating timer circuit for controlling the current flowing through the filament of the discharge lamp by controlling the on / off timing of the switching element on the side having the peak-to-peak voltage detection circuit of the two switching elements, and the peak When the voltage obtained by wired-ORing the peak-to-peak detection voltage detected by the peak-to-peak voltage detection circuit exceeds a predetermined value, of the two switching elements of the inverter circuit, the side having the peak-to-peak voltage detection circuit stops oscillation of the switching element, holds the oscillation stop state, the output of the inverter circuit is stopped quality A protection circuit for kicking manner, those having a.

The present invention relates to a DC power supply, an inverter circuit composed of a half-bridge circuit having two switching elements for converting a direct current supplied from the DC power supply into a high-frequency current, a choke coil having two secondary windings , and the choke A series circuit of a coupling capacitor connected to a coil via a discharge lamp, wherein the two secondary windings are connected to the two switching elements via resistors, respectively, and the two switching elements are staggered; in addition to the on / off control, and a plurality of lamp load circuit for lighting the discharge lamp by a high frequency current from the inverter circuit, each provided with two secondary windings to the choke coil of the discharge lamp load circuit Peak-to-peak detection of the voltage generated in each secondary winding connected to one of the switching elements The peak-to-peak voltage detection circuit, and the two switching elements for a period from when the power is turned on to when the discharge lamp is started and lit, using a voltage obtained by wired-oring the peak-to-peak detection voltage detected by the peak-to-peak voltage detection circuit as a control voltage Among them, a preheating timer circuit for controlling the current flowing through the filament of the discharge lamp by controlling the on / off timing of the switching element on the side having the peak-to-peak voltage detection circuit, and detection by the peak-to-peak voltage detection circuit When the voltage obtained by wired-ORing the detected peak-to-peak voltage exceeds a predetermined value, the oscillation of the switching element on the side having the peak-to-peak voltage detection circuit among the two switching elements of the inverter circuit is stopped. protection of times, and holds the oscillation stop state, so that the output of the inverter circuit is continuously stopped If so equipped, and can be made inexpensive small.

Embodiment FIG. 1 is a circuit diagram of a discharge lamp lighting device showing an embodiment of the present invention, and FIG. 2 is an operation characteristic explanatory diagram of an embodiment of the present invention.
In FIG. 1, a DC power source 1 is obtained, for example, by rectifying a commercial power source with a diode bridge and then smoothing it with an electrolytic capacitor. A series circuit of 2, 3 which is a switching element made of a MOSFET is connected to the DC power source 1 to constitute an inverter circuit.

  In the discharge lamp load circuit L1 (illustrated by a one-dot chain line), a choke coil 5 and a coupling capacitor 8 connected to the choke coil 5 via a discharge lamp 6 are connected in series. And a capacitor 7 is connected to the discharge lamp 6 in parallel. The anode of the diode 17 is connected to the negative electrode of the DC power supply 1, and the cathode is connected to the connection point between the coupling capacitor 8 and the discharge lamp 6. The anode of the diode 18 is connected to the cathode of the diode 17, and the cathode is connected to the positive electrode of the DC power supply 1.

  The discharge lamp load circuit L2 has the same configuration as the discharge lamp load circuit L1, the choke coil 9, the discharge lamp 10, and the coupling capacitor 12 are connected in series, and these series circuits are connected in parallel to the switching element 3, A capacitor 11 is connected to the discharge lamp 10 in parallel. The anode of the diode 19 is connected to the negative electrode of the DC power supply 1, and the cathode is connected to the connection point between the coupling capacitor 12 and the discharge lamp 11. The anode of the diode 20 is connected to the cathode of the diode 19, and the cathode is connected to the positive electrode of the DC power supply 1.

  Note that the capacitance values of the coupling capacitors 8 and 12 are determined so that current flows alternately to the power supply 1 in each half cycle via the diodes 17, 18, 19, and 20 when the discharge lamps 6 and 10 are normally lit. ing.

  The choke coils 5 and 9 of each discharge lamp load circuit L1 and L2 are each provided with two secondary windings 5a, 5b and 9a, 9b, and the secondary windings 5a, 5b and 9a, 9b are shown and marked. It is connected between the gate and the source via the resistors 13 and 15 and the resistors 14 and 16 so that the switching elements 2 and 3 are alternately turned ON / OFF by polarity (the primary windings and 2 of the choke coils 5 and 9 are connected). In order to show the coupling of the next winding, it is shown by a dashed line and a broken line). Note that an equivalent diode built in parallel between the drain and source of the switching elements 2 and 3 and a startup circuit for starting the inverter circuit are not shown. Here, when the discharge lamp 6 and the discharge lamp 10 have the same rated output, the circuit constants of the discharge lamp load circuits L1 and L2 are selected to be equal. Further, when the rated outputs of the discharge lamp 6 and the discharge lamp 10 are different, the resonance frequencies when the discharge lamp load circuits L1 and L2 are turned on are approximately equal, and the secondary winding voltage of each choke coil at the time of lighting is Set to be approximately equal.

  In the peak-to-peak voltage detection circuit P1 (illustrated by broken lines) for detecting the voltage generated in the secondary winding 5b provided in the choke coil 5 of the discharge lamp load circuit L1 (Peak to Peak detection), capacitors 21 and 22 are used. Are connected in series, the other end of the capacitor 22 is connected to the negative electrode of the DC power source 1, and the other end of the capacitor 21 is connected to the connection point between the secondary winding 5 b of the choke coil 5 and the resistor 13. The anode of the diode 23 is connected to the negative electrode of the DC power supply 1, and the cathode is connected to the connection point between the capacitor 21 and the capacitor 22. The anode of the diode 24 is connected to the cathode of the diode 23, and the cathode is connected to the capacitor 29. The other end of the capacitor 29 is connected to the negative electrode of the DC power supply 1.

  In this peak-to-peak voltage detection circuit P1, the peak-to-peak voltage of the voltage generated in the secondary winding 5b of the choke coil 5 is the inverse ratio of the capacitance values of the capacitors 21 and 22, and the diode 24 It is obtained as the anode voltage, that is, the voltage of the capacitor 29.

  In the peak-to-peak voltage detection circuit P2 that detects the voltage generated in the secondary winding 9b provided in the choke coil 9 of the discharge lamp load circuit L2, the capacitors 25 and 26 are connected in series, and the other end of the capacitor 26 is connected. Is connected to the connection point between the secondary winding 9 b of the choke coil 9 and the resistor 15. The anode of the diode 27 is connected to the negative electrode of the DC power supply 1, and the cathode is connected to the connection point between the capacitor 25 and the capacitor 26. The anode of the diode 28 is connected to the cathode of the diode 27, and the cathode is connected to the cathode of the diode 24.

In this peak-to-peak voltage detection circuit P2, the peak voltage of the voltage generated in the secondary winding 9b of the choke coil 9 is converted to the anode voltage of the diode 28, that is, the capacitor by the inverse ratio of the capacitance values of the capacitors 25 and 26. It is obtained as 29 voltages.
The capacitor 29 can obtain the higher output voltage of the peak-to-peak voltage detection circuits P1 and P2.

One end of the resistor 30 is connected to the cathode of the diode 28, the other end is connected to the capacitor 31, and the other end of the capacitor 31 is connected to the negative electrode of the DC power supply.
The resistor 30 and the capacitor 31 are circuits for integrating the peak detection voltage obtained in the capacitor 29, and the voltage of the capacitor 31 serves as a common input signal for a preheating timer circuit T10 and a protection circuit H1 described later.

In the preheating timer circuit T10 that controls the current flowing through the filaments of the discharge lamps 6 and 10 for a certain time from when the DC power supply 1 is turned on, the resistor 33 and the resistor 32 are connected in series, and one end is a connection point between the resistor 30 and the capacitor 31. The other end is connected to the negative electrode of the DC power source 1. The base of the transistor 34 is connected to the connection point of the resistors 33 and 32, the emitter is connected to the negative electrode of the DC power supply 1, and the collector is connected to the connection point of the resistors 35 and 36. The other end of the resistor 35 is connected to the connection point between the secondary winding 5 b and the resistor 13, and the other end of the resistor 36 is connected to the connection point between the secondary winding 9 b and the resistor 15. The anode of the diode 37 is connected to the negative electrode of the DC power supply 1, and the cathode is connected to the collector of the transistor 34. The capacitor 38 is connected in parallel with the diode 37. The transistor 39 has a base connected to the collector of the transistor 34, an emitter connected to the negative electrode of the DC power supply 1, and a collector connected to one end of the resistor 40.
The other end of the resistor 40 of the preheating timer circuit T10 is connected to the cathode of the diode 45, and the anode of the diode 45 is connected to the gate of the MOSFET 3.

  In the protection circuit H1 that stops the oscillation of the inverter circuit at the end of the life of the discharge lamps 6 and 10, stops the supply of power to the discharge lamp load circuits L1 and L2, and maintains the state until the DC power source 1 is shut off The Zener diode 41 has a cathode connected to the connection point between the resistor 30 and the capacitor 31, and an anode connected to the negative electrode of the DC power supply 1 through the resistor 42. The thyristor 43 has a cathode connected to the negative electrode of the DC power supply 1, a gate connected to the anode of the Zener diode 41, and an anode connected to the cathode of the diode 45. The resistor 44 has one end connected to the anode of the thyristor 43 and the other end connected to the positive electrode of the DC power source 1.

  Next, the operation of the discharge lamp lighting device showing the embodiment of the present invention will be described with reference to FIGS. FIG. 2 (5) shows the voltage waveform of the capacitor 31 after the DC power source 1 is turned on at time t = t0. (A) to (4) in FIG. 2 (1) show the operation waveforms of the respective parts in FIG. 1 during the preheating time T1 from t = t0 to t = t1, and (a) in (1). The voltage of the secondary winding 5b or 9b, (2) (a) is the collector-emitter voltage VCE of the transistor 34, (3) (a) is the collector-emitter voltage VCE of the transistor 39, ( (A) of 4) shows the gate-source voltage of the switching element (MOSFET) 3. The waveforms (b) of (b) to (4) of (1) are the discharge lamps 6 and 10 after time t = t1 corresponding to (a) of (a) to (4) of (1). The waveform at normal lighting is shown.

In FIG. 1, when the DC power source 1 is turned on at time t = t0, the switching elements 2 and 3 are alternately driven at a high frequency by a starting circuit not shown. Secondary winding 5b and 9 b to a voltage generated in the choke coil 5 and 9 is detected by the peak voltage detection circuit P1, P2, the capacitor 29, of the peak voltage detection circuit P1, P22, higher An output voltage is obtained. The peak detection voltage obtained in the capacitor 29 is integrated by the integrating circuit of the resistor 30 and the capacitor 31, and the voltage charged in the capacitor 31 becomes a common input signal for the preheating timer circuit T10 and the protection circuit H1.

In the preheating timer circuit T10, the transistor 34 is turned off during the preheating timer period T1 in which the voltage of the capacitor 31 satisfies the following expression (1).
VC31 × R32 / (R32 + R33) <VBE (TR34) (1)
However, the symbols in the above formula (1) indicate the following.
VC31: voltage of capacitor 31 R32: resistance value of resistor 32
R33: Resistance value of the resistor 33 VBE (TR34): Base-emitter threshold voltage of the transistor 34 (approximately 0.6 V)
During the period in which the transistor 34 is OFF, the collector-emitter voltage of the transistor 34 has a waveform shown in FIG. That is, since the base-emitter voltage of the transistor 34 has the waveform (a) in (2) above, the transistor 39 is turned off during the period Tb and then turned on during the period Tb as shown in (3) (a). become.
In this way, after the switching element 3 is reliably turned on for a predetermined period Tb for each drive cycle of the oscillation frequency, the gate current is bypassed and turned off.

  When the transistor 39 is turned on, the switching element (MOSFET) 3 cannot be kept on because the gate current is bypassed by the path of the diode 45, the resistor 40, and the transistor 39 as shown in (4) (a). , Turn on after turning on for Tb. The period of Ta + Tb is shorter than when the gate current of the switching element 3 is not bypassed through the transistor 39. That is, the oscillation frequency fPH of the inverter circuit during the preheating period of T1 is higher than the oscillation frequency fOP in the period after time t1. Here, if the resonance sharpness (Q) of the discharge lamp load circuit is set to be small with respect to the oscillation frequency fPH and large with respect to the oscillation frequency fOP, direct current is applied during the preheating period (operating at the oscillation frequency fPH). The current flowing from the power source 1 into the discharge lamp load circuit can be controlled to be smaller than that during normal lighting (operating at the oscillation frequency fOP).

Here, if the capacitance values of the capacitors 7 and 11 connected in parallel to the discharge lamps 6 and 10 are appropriately selected, the capacitors 7 and 11 are caused by the current flowing through the filaments of the discharge lamps 6 and 10 (filament preheating current). Can be made to be equal to or lower than the voltage required for starting the discharge lamps 6 and 10, and the discharge lamps 6 and 10 are not lit during the preheating timer period T1. Next, when time advances and time t = t1, the voltage of the capacitor 31 satisfies the following expression (2).
VC31-1 × R32 / (R32 + R33) = VBE (TR34) (2)
However, the symbols in the above formula (2) indicate the following.
VC31-1: voltage VC31 of capacitor 31 at t = t1

  During the period after t = t1, the transistor 34 is turned on and the transistor 39 is turned off, and the oscillation frequency of the inverter circuit is lowered from fPH to fOP. Therefore, as described above, the resonance sharpness (Q) of the discharge lamp load circuit increases with fOP, so that the current flowing from the DC power source 1 to the discharge lamp load circuit increases and the voltages of the capacitors 7 and 11 increase. The discharge lamps 6 and 10 are turned on. If the discharge lamps 6 and 10 are lit, the equivalent resistance of the discharge lamps 6 and 10 is connected in parallel to the capacitors 7 and 11, so that the sharpness of resonance of the discharge lamp load circuit is reduced. A current determined by the circuit constant of the discharge lamp load circuit and the oscillation frequency fOP flows through 10, and the discharge is stably continued thereafter.

  Next, in the protection circuit H1, after the discharge lamps 6 and 10 are turned on, for example, when the discharge lamp 6 reaches the end of its life due to exhaustion of the discharge material of the filament at time t = t2, the voltage across the discharge lamp 6 is Increases from the time of normal lighting, and the voltage across the choke coil 5 also increases. The change in voltage is detected by the peak-to-peak voltage detection circuit P1 provided in the secondary winding 5b of the choke coil 5, and the voltage of the capacitor 31 also increases. Further, the zener diode 41 and the resistor 42 of the protection circuit H1 are appropriately selected, and the thyristor 43 is not turned on at the voltage VC31-2 obtained at the capacitor 31 when the discharge lamp 6 is normally lit. When the voltage of the discharge lamp 6 rises at the end of the life, the voltage VC31-3 obtained at the capacitor 31 is turned on.

  If the thyristor 43 is turned on at time t = t3, the current flowing through the gate of the switching element 3 from the secondary winding of the choke coil via the resistors 13 and 15 is bypassed via the diode 45 and the thyristor 43. 3 is turned OFF and the oscillation of the inverter circuit stops. Even if the oscillation stops, since the holding current continues to flow from the DC power supply 1 to the thyristor 43 through the resistor 44, this state is maintained until the DC power supply 1 is shut off, so that the discharge lamp 6 continued to abnormally discharge. It is possible to prevent driving in a state. In addition, although the case where the discharge lamp 6 is not normal discharge was demonstrated above, when the discharge lamp 10 is not normal discharge and when any discharge lamp is not normal discharge, it is operated in the state which continued abnormal discharge similarly. Can be prevented.

  As described above, a plurality of discharge lamp load circuits L1 and L2 are provided, and the voltages generated in the secondary windings 5b and 9b provided in the choke coils 5 and 9 of the discharge lamp load circuits L1 and L2, respectively, are detected between peaks. The discharge lamps 6 and 10 are turned on when the power is turned on using a voltage obtained by wired-ORing the peak-to-peak detection voltages detected by the peak-to-peak voltage detection circuits P1 and P2 and the peak-to-peak detection voltages P1 and P2 The preheated timer circuit T10 for controlling the current flowing through the filaments of the discharge lamps 6 and 10 and the voltage obtained by wired-or-detecting the peak-to-peak detection voltages detected by the peak-to-peak voltage detection circuits P1 and P2 exceed a predetermined value. And a protection circuit H1 that stops the oscillation of the switching elements 2 and 3 of the inverter circuit and maintains this oscillation stopped state. P1, the detection voltage of P2 is used as the input voltage of the sharing of the preheating timer circuit T10 and the protection circuit H1, it can be made inexpensive small.

  Even if one of the discharge lamps is removed due to a failure due to the end of the life of the discharge lamp 6 or the discharge lamp 10, the peak-to-peak voltage detection circuits P1, P2 correspond to the discharge lamp load circuits L1, L2. Since the timer period is controlled by a voltage with their outputs wired or ORed independently, even if one of the two lamps is removed, the timer period is the same as when all two lamps are installed. Can be set.

  Further, even if one of the discharge lamps is removed due to a failure due to the end of the life of the discharge lamp 6 or the discharge lamp 10, the peak-to-peak voltage detection circuits P1, P2 are independent of each other corresponding to each discharge lamp load circuit. Since the control voltage is a voltage obtained by wired-oring their outputs, even if one of the two lights is removed, the abnormal lighting state can be detected under the same conditions as when all the two lights are installed. it can.

  In addition, since the preheating timer circuit T10 reliably turns on the switching element 3 for a predetermined Ta period for each drive cycle of the oscillation frequency, the gate current is bypassed and turned off to increase the oscillation frequency. During the timer period T1, the discharge lamps 6 and 10 can be reliably oscillated at an oscillation frequency that does not cause a cold start.

  In addition, since the common input voltage of the preheating timer circuit T10 and the protection circuit H1 is the detection voltage of the peak-to-peak voltage detection circuits P1 and P2, it is possible to detect the discharge state of both electrodes of the discharge lamps 6 and 10. Since the operation of the protection circuit H1 is delayed using the timer time of the preheating timer T10, the protective operation can be performed when an abnormal discharge state continues corresponding to the preheating timer time. Can be prevented from malfunctioning.

  Further, the cathodes are connected to the connection points of the coupling capacitors 8 and 12 and the discharge lamps 6 and 10 respectively, and the diodes 17 and 19 whose anodes are respectively connected to the negative electrode of the DC power source 1 and the coupling capacitors 8 and 12 and the discharge capacitors. Since the anodes are connected to the connection points of the electric lamps 6 and 10 and the cathodes are respectively connected to the positive electrodes of the DC power supply 1, the discharge lamps 6 and 10 have an asymmetric phenomenon of the discharge current. Even in this case, it is possible to prevent the current flowing in the discharge lamp load circuits L1 and L2 from increasing, and to prevent the circuit element from being defective due to the increase in current.

  In FIG. 1 showing the present embodiment, the case where two discharge lamp load circuits are connected has been described. However, one or three or more discharge lamps may be connected, and the same effect can be obtained.

It is a circuit diagram of a discharge lamp lighting device showing an embodiment of the present invention. It is an operation characteristic figure of a discharge lamp lighting device showing an embodiment of this invention.

Explanation of symbols

1 DC power supply, 2, 3 SW element, 5, 9 choke coil, 6, 10 discharge lamp, 7, 11 capacitor, 8, 12 coupling capacitor, 17, 18, 19, 20 diode, 31 capacitor, 39 transistor, 41 Zener diode, 43 thyristor, L1, L2 discharge lamp load circuit, P1, P2 peak-to-peak voltage detection circuit, T10 preheating timer circuit, H1 protection circuit.

Claims (2)

DC power supply,
An inverter circuit composed of a half-bridge circuit having two switching elements for converting a direct current supplied from the direct current power source into a high frequency current;
A choke coil having two secondary windings and a series circuit of a coupling capacitor connected to the choke coil via a discharge lamp. The two secondary windings are respectively switched by the two switching devices via resistors. is connected to the element, while alternately turning on / off controlling the two switching elements, a plurality of lamp load circuit for lighting the discharge lamp by a high frequency current from the inverter circuit,
A peak-to-peak detection of a voltage generated in each secondary winding connected to any one of the two secondary windings provided in the choke coil of the discharge lamp load circuit. A voltage detection circuit;
The peak-to-peak voltage detection circuit of the two switching elements is a period from when the power is turned on to when the discharge lamp is started and turned on, with a voltage obtained by wired-oring the peak-to-peak detection voltage detected by the peak-to-peak voltage detection circuit as a control voltage. A preheating timer circuit for controlling the on / off timing of the switching element on the side having a current to control the current flowing through the filament of the discharge lamp;
Of the two switching elements of the inverter circuit, the side having the peak-to-peak voltage detection circuit when a voltage obtained by wired-oring the peak-to-peak detection voltage detected by the peak-to-peak voltage detection circuit exceeds a predetermined value A protection circuit that stops the oscillation of the switching element, maintains this oscillation stop state, and continues to stop the output of the inverter circuit ;
A discharge lamp lighting device comprising: A diode whose cathode is connected to the connection point of the coupling capacitor and the discharge lamp, and whose anode is connected to the negative electrode of the DC power supply;
A diode in which an anode is connected to a connection point between the coupling capacitor and the discharge lamp, and a cathode is connected to a positive electrode of the DC power supply;
The discharge lamp lighting device according to claim 1 Symbol mounting characterized by comprising a.

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