JPH088157B2 - Discharge lamp lighting device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a discharge lamp lighting device that limits a tube current of a high pressure discharge lamp by a chopper circuit.

[Prior Art] Conventionally, a high-pressure discharge lamp such as a metal halide lamp has been widely used for outdoor lighting. This type of high-pressure discharge lamp has a feature that it has a large luminous flux and has a long life as a point light source. Therefore, recently, the number of cases where it is introduced indoors is increasing. For indoor use, a lightweight and small-sized ballast for the above high-pressure discharge lamp is required. An electronic circuit is generally considered as a discharge lamp lighting device that satisfies the above requirements, and recently, there is an example in which some high pressure discharge lamps are commercialized.

On the other hand, the discharge lamp lighting device having the electronic circuit has some characteristics as compared with the lighting device using the conventional transformer and choke coil. Among them, looking at the lamp power factor, the conventional transformer and choke coil are used. In the case of the lighting device according to 1., it was about 0.7 to 0.9, whereas in the discharge lamp lighting device with an electronic circuit, most of it was about 1.
The point of 0 is a major feature. That is, the values of the tube voltage and the tube current when consuming the same power are different combinations depending on the two lighting methods. More specifically, it is general that the discharge lamp lighting device in which both the tube voltage and the tube current under the same tube power are integrated into an electronic circuit have smaller values. In a discharge lamp lighting device with an electronic circuit, particularly, the tube current is smaller than in the case of a conventional lighting device using a transformer or a choke coil, so it is expected that the power loss as a lighting device will be reduced, but it is expected to be advantageous. Since a problem to be solved in characteristics has been found, a specific example will be described below.

FIG. 3 shows an example of the above-described lighting device having an electronic circuit. The AC power supply V ₁ is full-wave rectified by the full-wave rectifier DB ₁ , smoothed by the smoothing capacitor C ₁ , and converted into a DC voltage. A series circuit of transistors Q ₁ and Q _{3 and} a series circuit of transistors Q ₂ and Q ₄ are connected in parallel to both ends of the capacitor C ₁ via a resistor R ₁ for current detection.
The transistors Q ₁ and Q ₂ are switched at high frequencies, and the transistors Q ₃ and Q ₄ are switched at low frequencies. Diodes D ₁ and D ₂ are connected in antiparallel to the transistors Q ₁ and Q ₂ , respectively. The diode D ₃ is connected in antiparallel to the series circuit of the transistor Q ₃ and the resistor R ₁ , and the diode D ₄ is connected in antiparallel to the series circuit of the transistor Q ₄ and the resistor R ₁ . A series circuit of an inductor L ₁ and a capacitor C ₂ is connected between a connection point b of the transistors Q ₁ and Q _{3 and} a connection point d of the transistors Q ₂ and Q ₄ , and a high voltage is applied across the capacitor C _2. The discharge lamp DL and the inductor L ₂ series circuit are connected in parallel.

FIG. 4 shows a waveform of a main part when the high pressure discharge lamp DL is in a steady lighting state in the above circuit. In the figure,
(A), (b), (c), and (d) show open / closed states of the transistors Q ₁ , Q ₂ , Q ₃ , and Q ₄ , respectively. As shown,
Transistors Q ₁ and Q ₄ , and transistors Q ₂ and Q ₃ are operating in pairs, respectively. FIG. 4 (e) shows the waveform of the current flowing through the inductor L ₁ . When transistor Q ₁ is turned on, inductor L ₁ is connected to capacitor C ₁
A gradually increasing current determined by the inductor L ₂ and the capacitor C ₂ flows through the transistor Q ₄ and the resistor R ₁ during the on period, and when the transistor Q ₁ is off, the inductor L ₁ stored when the transistor Q ₁ is on is stored. Energy flows through the transistor Q ₄ , the resistor R ₁ and the diode D ₃ during the ON period and is released to the circuit formed by the high pressure discharge lamp DL, the inductor L ₂ and the capacitor C ₂ . Therefore, the transistor
The current of the inductor L ₁ in _one ON / OFF cycle of Q ₁ has a triangular waveform as shown in FIG. 4 (e). The above operation is repeated during the ON period of the transistor Q ₄ , but when the transistor Q ₄ is turned off, the same operation as described above is performed by the combination of the transistors Q ₂ and Q ₃ . In the operation of the pair of transistors Q ₂ and Q ₃ , the current flowing in the inductor L ₁ (see FIG. 4 (e)) is
It is in the opposite direction to the operation of the pair of Q ₁ and Q ₄ . The current I _L1 having a waveform as shown in FIG. 4 (e) flows through the inductor L ₁ by the above operation, but the inductor L ₂ acting as a low pass filter is connected in series to the high pressure discharge lamp DL. Since the capacitor C ₂ acting as a high-pass filter is connected in parallel to the high-pressure discharge lamp DL and the inductor L ₂ , only the low-frequency component of the current I _L1 appears in the high-pressure discharge lamp DL as shown in FIG. ) Flows like a waveform. In addition,
The high frequency component of the current I _L1 flows through the capacitor C ₂ ,
It forms the current I _L1 as a whole.

Since the lighting device shown in FIG. 3 operates as described above,
Inductor L _1, which is the main current limiting element, operates at high frequency, so the inductance value is small and small
Weight reduction can be achieved. In addition, as described above, the low-frequency, substantially rectangular-wave current flows through the high-pressure discharge lamp DL.
It is possible to avoid the instability of the arc due to the acoustic resonance phenomenon, which is one of the problems when the DL is lit at a high frequency.

[Problems to be Solved by the Invention] As a result of trial manufacture of the lighting device shown in FIG. 3 and a lamp life test, the lamp life is longer than that of a conventional so-called copper-iron type lighting device including a choke coil, a transformer and the like. It turns out that there is one that becomes 1/2, for example. 5 (a) and 5 (b) are the electronic lighting device shown in FIG.
The load characteristics of each of the above-mentioned copper-iron type lighting devices are shown.
In the figure, the solid line shows the load characteristics of the electronic lighting device, and the broken line shows the load characteristics of the copper-iron lighting device. The combination of V ₀₁ and I _{01 and} the combination of V ₀₂ and I ₀₂ in FIG. 5 (a) are combinations of the tube voltage and the tube current for obtaining the rated output power when the same discharge lamp is used. The case where the combination of V ₀₁ and I ₀₁ is an electronic lighting device, and the combination of V ₀₂ and I ₀₂ is a copper iron lighting device is shown. As described above, the lamp power factor is different between the two lighting devices, and thus the combination of the tube voltage and the tube current at the same output power is different. V ₀₁ and V _{02 in} FIG. 5 (b) are tube voltages when the rated output power W ₀ is taken, and respectively represent the case of the electronic lighting device and the case of the copper iron lighting device.

Generally, in the case of an electronic lighting device, due to its good lamp power factor, the tube current and tube voltage required to obtain the rated output power are smaller than those of a copper iron lighting device. Seems small. Further, the maximum value of the output power with respect to the tube voltage is also generally set smaller than that of the copper-iron type lighting device, so that the effective temperature stress on the lamp is also considered to be small. Therefore, we thought that the local temperature of the arc tube of the discharge lamp might be the cause of the deterioration of the lamp life, and conducted the following experiments. That is, the discharge lamp was lit horizontally, and the maximum brightness of the arc considered to have a correlation with the local temperature of the arc tube was determined for two cases, an electronic lighting device and a copper iron lighting device.

Fig. 6 shows an example of the lamp characteristics used in the experiment. As the lamp, the data when the metal halide lamp 150W (manufactured by Osram) is horizontally lit is shown for the copper iron lighting device and the electronic lighting device, respectively. It is shown by connecting it with a broken line and a solid line. The lamp, and V ₁ a small lamp where a initial lighting products, and V ₁ a of lamp corresponding to a so-called test lamps, V ₁ a where a lifetime end product
Three large lamps were used as parameters. here,
V ₁ a represents the tube voltage and W ₁ a represents the tube power. Number 1 in the graph
2 and 3 represent the points where the maximum arc brightness is the same, and have a relationship of 3>2> 1. Also,
The line connecting the points 1, 2, and 3 with a substantially straight line is the characteristic of the above three types of lamps in which V ₁ a and W ₁ a are variable in each lighting device by adjusting the output of the lighting device. Also, the lines connecting the same numbers with a broken line and a solid line connect the points of the same maximum brightness in the copper-iron lighting device and the electronic lighting device, respectively. In addition, regarding the point of maximum brightness,
When the arc A as shown in the figure is formed between the electrodes E ₁ and E ₂ , it is common that the position is as shown by the point P. That is, it can be said that the line connecting the same numbers is an isoluminance curve in each of the copper-iron type and electronic type lighting devices.

In FIG. 6, when the copper-iron type lighting device and the electronic lighting device are viewed from the viewpoint of the maximum brightness, that is, the local temperature of the arc tube, the local parts of the arc tube according to the two lighting methods can be used up to a substantially rated tube voltage. There is no difference in the target temperature, and it can be seen that the difference due to the lighting method becomes extremely large after the voltage is exceeded. As a description of the above phenomenon, the electric power of the electronic lighting device is higher as described above, so that the current for obtaining the same output power can be small. That is, in order to maintain the effective temperature of the arc, the arc tends to be thinner in the electronic lighting device, but when the tube voltage V ₁ a exceeds a certain level, the arc is concentrated at the center. From this, it is estimated that the arc center brightness is unavoidably increased, and it can be interpreted as meaning that the level of the tube voltage V ₁ a is approximately in the vicinity of the rated voltage.

Against the above background, focusing on the load characteristics of the lighting device represented by FIG. 3 (for example, the solid line in FIG. 5B), the arc tube of the high-pressure discharge lamp DL corresponds to the load characteristics. Considering the local temperature of the above, it is never a desirable characteristic, that is, the local temperature of the arc tube of the high pressure discharge lamp DL is as shown in Fig. 6 for the combination of tube power and tube voltage. Since it exhibits characteristics (in the case of an electronic lighting device, if the rated tube voltage is exceeded, it is necessary to reduce the tube power in order to prevent the arc tube temperature from rising),
In the case of a load characteristic exhibiting a characteristic as shown by the solid line in FIG. 5 (b) (for example, a characteristic in which the tube power gradually increases as the tube voltage rises), the arc tube temperature is reached after the voltage exceeds the rated voltage. Rises, the temperature stress of the arc tube increases,
The lamp life characteristics may be adversely affected.

The present invention has been made in view of these points,
The purpose thereof is to prolong the lamp life in a discharge lamp lighting device in which the tube current of a high pressure discharge lamp is limited by a chopper circuit.

[Means for Solving the Problems] In the present invention, in order to solve the above problems, as shown in FIGS. 1 to 3, the tube current of the high pressure discharge lamp DL is limited by a chopper circuit. A discharge lamp lighting device for
The chopper circuit is a switching element Q ₁ (or Q ₂ )
Includes both detection resistor R ₁ which can detect the increasing current flowing during the ON and decreasing current flowing at the time of off, the detecting resistor R ₁
By turning on the switching element at the time of a decrease in the gradually decreasing current detected by, and turning off the switching element in a predetermined cycle, the turning-on phase of the switching element is advanced as the tube voltage of the high pressure discharge lamp increases. Means for controlling the ON period of the switching element in an increasing direction, and the switching element when the tube voltage of the high pressure discharge lamp exceeds substantially the rated voltage and the average value of the current detected by the detection resistor falls below a predetermined value. It has means for advancing the phase to be turned off to control the maximum value of the ON period of the switching element in a decreasing direction.

[Operation] First, the control technique which is the premise of the present invention will be described. As shown in FIG. 3, in the lighting circuit composed mainly of the so-called chopper behavior by the transistor Q ₁ or Q _2, when controlling the transistor Q ₁ or Q _2, the maximum value of the current flowing through the transistor Q ₁ or Q ₂ In order to suppress
It is becoming common to set the maximum on-duty. This will be described by exemplifying a specific control circuit.

FIG. 8 shows a basic portion of the control circuit for the transistors Q _{1 to} Q ₄ shown in FIG. ₁ , particularly relating to high frequency switching of the transistors Q ₁ and Q ₂ . FIG. 8 mainly shows a part of an equivalent circuit of an IC represented by, for example, a switching regulator IC (IR3MO2) manufactured by Sharp Corporation. Points h and g in FIG. Both ends h and g of resistor R _{1 in} the figure
Respectively connected to. In FIG. 8, the part surrounded by the alternate long and short dash line is a part of the equivalent circuit of the IC. In the figure, 1
Is a differential amplifier, 2 and 3 are comparators, 4 is an OR circuit, and 5
Is a negative circuit, 6,7 is an AND circuit, 8 and 9 is a NOR circuit, Tr ₁ , Tr
₂ is a transistor, OSC is an oscillator, and TFF is a T-flip-flop.

FIG. 9 is a waveform diagram for explaining the operation of the above circuit.
In Figure 3, the transistors Q _1, Q _2, for example, the transistor Q ₁ is turned on, as described above, the inductor
When an increasing current flows through L ₁ and transistor Q ₁ turns off,
Also as described above, a gradually decreasing current flows through the inductor L ₁ . The resistor R _1, since the current to direct the current of the inductor L ₁ flows, a voltage detected by the resistor R ₁ is a voltage V _R1 as shown in FIG. 9 (a). The above voltage V _R1 is the 8th
When input to the terminals of the figure, the output of the differential amplifier 1 exhibits a waveform like the voltage V _A shown in FIG. One of the inputs. The voltage V ₅ shown in FIG. 9 is input to the other input of the comparator 2. This voltage V ₅ is a sawtooth wave determined by a capacitor and a resistor that are externally connected to the oscillator OSC and the terminal, respectively. When the voltages V _A and V ₅ are input to the comparator 2, the transistor Tr ₁ which is the output of the switching regulator IC is turned off when V ₅ > V _A. The situation is shown in FIG. 9 (c). The voltage in FIG. 9 (b)
V ₄ indicates the input to another comparator 3 and the voltage V ₅
At the same time, it is a so-called dead time control voltage for determining the minimum value of the OFF period in FIG. 9 (c).

In the above description, it was explained that the on / off state of the transistor Tr ₁ in FIG. 8 is as shown in FIG. 9 (c), but this description is for either the transistor Q ₁ or Q _{2 in} FIG. It holds even in the on / off state of. This is because the current when the transistors Q ₁ and Q ₂ are on / off flows through the resistor R ₁ . Actually, the ON / OFF signal of the transistor Q ₁ or Q ₂ shown in FIG. 9C is turned ON / OFF of the transistor Q ₂ when the ON signal of the transistor Q ₃ is output from the control unit (not shown). It is used as a signal and is used as an on / off signal for transistor Q ₁ when the on signal for transistor Q ₄ is being output.This operation is the on / off time of transistors Q ₃ and Q _4. Since it can be easily achieved by the combination of the setting timer and the logic circuit, the presentation and description of the circuit diagram will be omitted.

The above is a description of the case where the control circuit of the transistors Q _{1 to} Q ₄ is stationary, particularly the part relating to high-frequency switching of the transistors Q ₁ and Q ₂ . Next, a case where the characteristics of the high-pressure discharge lamp DL change due to aging will be described. The high-pressure discharge lamp DL generally has a tendency that the tube voltage increases and the tube current decreases with the life. That is, the equivalent resistance component increases. At this time, as shown in FIG. 3, in the so-called chopper circuit that mainly limits the current by the inductor L ₁ , the slope of the current that gradually increases when the transistor Q ₁ or Q ₂ is turned on becomes smaller. First
FIG. 10 is a reprint of FIG. 9 for explaining the situation, and the broken line shows the state where the life of the high pressure discharge lamp DL in the state shown by the solid line has advanced. The voltage V _R1 shown in FIG. 10 (a) corresponds to the tube current I _DL , but the slope of this current waveform becomes gentle as the life advances. When the tube current I _DL is in the state shown by the broken line, the voltage V _A has a waveform as shown by the broken line in FIG. 10B, and the intersection with the voltage V ₅ changes. This change in the intersection with the voltage V ₅ is caused by the transistor Q ₁ or
It works to extend the ON period of Q ₂ , and the situation is shown in Figs. 10 (c) and (d). That is, when the life of the high pressure discharge lamp DL has advanced, as described above, the transistor Q ₁ or Q ₂
Since the on-state of the
The control circuit is set to suppress the decrease of I _DL .
Now, when the life of the high pressure discharge lamp DL is advanced and the intersection of the voltage V _A and the voltage V ₅ comes before the intersection of the voltage V ₄ and the voltage V ₅ , the function of suppressing the decrease of the tube current I _DL is stopped. Does not work, high pressure discharge lamp D
Since the characteristics are left to the L, the tube current I _DL tends to decrease gradually.

As described above, since the ON period of the transistor Q ₁ or Q ₂ is controlled, the intersection of the voltage V _A and the voltage V ₅ is the transistor Q ₁
Or while it is dominant in determining the on-time of Q ₂ , the tube current I _DL
As the tube voltage V _DL rises, the tube power W _DL also rises, and the intersection of the voltage V ₄ and the voltage V ₅ is dominant in determining the ON period of the transistor Q ₁ or Q _2. After that, the tube power W _DL tends to decrease. In a so-called chopper circuit, the above control is general, and the load characteristic of the lighting device (for example, the solid line in FIG. 5 (b)) when such control is performed is the high pressure discharge lamp DL. progression of life, i.e. at elevated process tube voltage V _DL, exceeds a certain tube voltage V _DL, it is assumed that the local temperature of the arc tube rises rapidly, equiluminance indicated by a solid line in FIG. 6 It is by no means desirable for the curve (ie the local maximum temperature of the arc tube).

Therefore, according to the present invention, when the voltage becomes equal to or higher than a predetermined tube voltage (specifically, a voltage substantially equal to the rated voltage, hereinafter), the maximum value of the on-duty of the high-frequency switching element is set in the decreasing direction. A means for doing so is added. Therefore, according to the present invention, it is possible to prevent the local high temperature of the arc tube, which has occurred with the progress of the lamp life, from being generated, and to improve the lamp life.

[Embodiment] FIG. 1 shows a main configuration of a control circuit for explaining an embodiment of the present invention. The same elements as those of the circuit of FIG. 8 are designated by the same reference numerals, and duplicated description will be omitted. In the circuit shown in FIG. 1, resistors R ₁₃ , R ₁₄ and capacitors C ₁₁ , C
₁₂ and diode D ₁₁ are newly added and are connected as shown. Although not shown in FIG. 8, the differential amplifier 10 and the terminals are included in the IC from the beginning and have the same configuration as the differential amplifier 1 and the terminals. This embodiment uses this differential amplifier 10 and differs from FIG. 8 in that the input to the comparator 2 is an OR configuration of the outputs of the differential amplifiers 1 and 10.

FIG. 2 is an operation waveform diagram of this embodiment. 2 (a), (b) and (c) are reprints of FIG. FIG. 2 (d) shows the input relation of the differential amplifier 10, and the voltage V of the solid line
_{Reference numeral 15} indicates a state in which the tube voltage V _DL is equal to or lower than the predetermined voltage, that is, the tube current I _DL is equal to or higher than the predetermined current, and the broken line voltage V ₁₅ ′ is the tube voltage V _DL.
This shows the state when _DL is equal to or higher than a predetermined voltage, that is, the tube current I _DL is equal to or lower than a predetermined current. Since V ₁₅ and V ₁₅ ′ are the average value of the tube current I _DL detected by the resistor R ₁ due to the diode D ₁₁ , the capacitor C _12, and the resistor R ₁₄ , they have the above relationship. The voltage V ₁₆ is the triangular wave voltage generated by the oscillator OSC directly supplied to the terminals. FIG. 2 (e) shows a differential amplifier 10 when the tube voltage V _DL exceeds a predetermined voltage.
The output width increases as the tube voltage V _DL increases. In FIG. 2 (f), the voltage V _A when the differential amplifier 10 is in the state shown in FIG. 2 (e)
Is indicated by a broken line. Therefore, when the tube voltage V _DL exceeds a predetermined voltage, the timing at which the transistor Q ₁ or Q ₂ is turned on, become voltage V _B of FIG. 2 (e) dominates, the transistor Q ₁ or Turning on and off of Q ₂ is as shown in Fig. 2 (g). In Fig. 2 (g), the time
t ₁ ′ is located before time t ₁ , and as described with reference to FIG. 8, the direction in which the ON period of the transistor Q ₁ or Q ₂ is extended,
That is, it works to suppress the decrease of the current I _DL , but since the time t ₂ ′ also acts to be positioned earlier than the time t ₂ ,
It works to shorten the ON period of the transistor Q ₁ or Q ₂ .
By setting the change width from time t ₂ to time t ₂ ′ to be larger than the change width from time t ₁ to t ₁ ′, the tube current I _DL exceeds the tube voltage V _DL at a certain predetermined value. From the point in time, the decrease becomes steeper, and as a result, the operation of decreasing the tube power W _DL can be achieved. FIG. 2 (h) shows how the current of the inductor L ₁ is decreased by the above operation.

Since the present embodiment operates as described above, it is possible to have a load characteristic such that the tube power W _DL is reduced by an arbitrary curve after the tube voltage V _DL exceeds a certain predetermined value, so that the lamp life is shortened. It is possible to prevent local high temperature of the arc tube, which has occurred with the progress of, and to improve the life of the lamp.

In the present embodiment, the predetermined value of the tube voltage V _DL is set at the intersection of the effective value of the tube current I _DL and the reference triangular wave voltage, but the tube voltage V _DL is set instead of the effective value of the tube current I _DL. It may be directly detected, or another reference waveform may be used instead of the reference triangular wave voltage. That is, as a result, at the maximum value of the on-duty of the so-called chopper transistor, the on-period of the transistor is set to be equal to or less than the maximum value of the on-duty up to a predetermined tube voltage, and the on-duty is set to the predetermined tube voltage or higher. The same effect can be achieved if the circuit sets the maximum value of the duty in the decreasing direction.

[Advantages of the Invention] According to the present invention, as described above, in the discharge lamp lighting device in which the tube current of the high pressure discharge lamp is limited by the chopper circuit, until the tube voltage of the high pressure discharge lamp reaches substantially the rated voltage. As the tube voltage rises, the ON period of the switching element of the chopper circuit is controlled to increase, and when the tube voltage of the high-pressure discharge lamp exceeds approximately the rated voltage, the maximum value of the ON period of the switching element of the chopper circuit changes in the decreasing direction. Since the control means is provided for controlling the load voltage, the load characteristic can be such that the tube power is reduced after the tube voltage exceeds substantially the rated voltage, and therefore, the local part of the arc tube that has occurred with the progress of the lamp life. It is possible to prevent the generation of extremely high temperature and to improve the life of the lamp.

Further, in the present invention, on the premise that a chopper circuit including a detection resistor capable of detecting both a gradually increasing current flowing when the switching element is turned on and a gradually decreasing current flowing when the switching element is turned off is used as a lighting device of a high pressure discharge lamp, The switching element is turned on when the gradually decreasing current detected by the detection resistor is decreased, and is turned off at a predetermined cycle, so that the switching element is turned on as the tube voltage of the high pressure discharge lamp rises. Is to control the ON period of the switching element in an increasing direction earlier, and when the average value of the current detected by the detection resistor falls below a predetermined value, the tube voltage of the high-pressure discharge lamp is substantially rated. It is judged that the voltage has been exceeded,
Since the phase in which the switching element is turned off is advanced to control the maximum value of the ON period of the switching element in the decreasing direction, a voltage detection circuit for detecting the tube voltage is separately connected to both ends of the high pressure discharge lamp. One detection resistor may be used both as a detection means for controlling the timing when the switching element is turned on and as a detection means for controlling the timing when the switching element is turned off. There is an advantage that the circuit system becomes very simple.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a control circuit used in one embodiment of the present invention,
2 is an operation waveform diagram of the same, FIG. 3 is a circuit diagram of a conventional discharge lamp lighting device, FIG. 4 is an operation waveform diagram of the same, FIG. 5 and FIG. 6 are operation explanatory diagrams of the same, and FIG. The figure is a diagram for explaining the highest point of the brightness of the arc in the same as above, FIG. 8 is a control circuit used in a conventional discharge lamp lighting device, and FIGS. 9 and 10 are operation waveform diagrams in the same. Q _{1 to} Q ₄ are transistors, and DL is a high pressure discharge lamp.

Claims (1)

[Claims] 1. A discharge lamp lighting device for limiting a tube current of a high pressure discharge lamp by a chopper circuit, wherein the chopper circuit can detect both a gradually increasing current flowing when a switching element is on and a gradually decreasing current flowing when the switching element is off. A detection resistor is provided, and when the gradually decreasing current detected by the detection resistor is decreased, the switching element is turned on, and the switching element is turned off at a predetermined cycle, so that the switching is performed as the tube voltage of the high-pressure discharge lamp increases. Means for controlling the ON period of the switching element in an increasing direction by advancing the ON phase of the element, and the average value of the current detected by the detection resistor when the tube voltage of the high pressure discharge lamp exceeds substantially the rated voltage. When it is lower than a predetermined value, the phase in which the switching element is turned off is advanced to maximize the ON period of the switching element. The discharge lamp lighting apparatus characterized by comprising means for controlling the decreasing direction.