JP2005276594A - Discharge lamp lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent flickering and fading-out of a metal halide lamp such as a mercury-less discharge lamp used as a vehicular headlight or the like, and secure stable lighting. <P>SOLUTION: It is so set that during a period other than the proximity of a positive and negative polarities switching time of a square wave alternate current, routine electric power is supplied to the discharge lamp 4, and so that in the proximity of the positive and negative polarities switching time, the electric power supplied to the discharge lamp 4 will be increased based on an electric power increase setting signal Sg which CPU 53 outputs. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a discharge lamp lighting device for controlling lighting of a discharge lamp such as a metal halide lamp used for a headlamp of an automobile.

  In the rectangular wave AC lighting of high-pressure discharge lamps, the current to the discharge lamp is momentarily interrupted (pause) when the positive / negative polarity switching (reversal) of the rectangular wave AC is switched on (lighting below the rated power). This phenomenon can cause flickering and disappearance. Examples of conventional discharge lamp lighting devices that have improved such a phenomenon include the following.

  As a first conventional example, a power supply circuit that outputs a predetermined DC voltage V1, and a power conversion circuit that outputs a DC voltage V2 using the DC voltage V1 output from the power supply circuit as a power source and supplies desired power to a discharge lamp, A polarity reversing circuit for converting the DC voltage V2 output from the power conversion circuit into a rectangular wave voltage having a low frequency of several tens to several hundreds Hz and applying the voltage to the discharge lamp, and a dimming power for setting a target dimming power from the outside. It is composed of a dimmer that outputs an optical signal, and by increasing the target output of the power conversion circuit during the polarity inversion operation of the rectangular wave output by the polarity inversion circuit, the re-ignition of the discharge lamp is facilitated, and the discharge lamp There is one in which the current resting period is shortened and the discharge lamp is stably dimmed to prevent it from going out. Further, there is a circuit that realizes the same function as described above by operating a discharge lamp starting circuit for starting the discharge lamp during a current pause period at the time of polarity reversal (see, for example, Patent Document 1).

  As a conventional example No. 2, a control circuit to which a target value of lamp (discharge lamp) power by a dimmer, a voltage detection signal of a DC voltage by a voltage detection circuit, and a current detection signal of an inductor current by a current detection circuit are input, In response to the voltage detection signal, set the target value of the peak value of the inductor current so as to achieve the target lamp power, and turn on the switching element until the current detection signal detected by the current detection circuit reaches the target value. In the dimming lighting, the lamp current flowing through the discharge lamp is set to a desired value, and the lamp current pause period at the time of polarity reversal is suppressed so that the lamp does not go out (for example, Patent Documents) 2).

  In addition to the above, as a conventional example in which the rest period of the discharge lamp current is shortened by increasing the output voltage to the discharge lamp at the time of polarity reversal at the time of dimming lighting, the discharge lamp is stably dimmed as follows. There exists patent document 3. FIG.

JP 2002-289391 A JP 2003-109788 A JP 2003-133092 A

Conventional discharge lamp lighting devices are configured as described above, but these conventional examples are intended for dimming lighting of high pressure discharge lamps containing mercury.
However, high-pressure discharge lamps, like discharge lamps such as mercury-free metal halide lamps used in automobile headlamps, arc discharge ceases during positive / negative polarity switching (reversal) in rectangular wave AC lighting, and rated again. There is a discharge lamp in which a current less than a rated current flows before an arc discharge that becomes a voltage occurs. In general, mercury-free discharge lamps contain a large amount of metal halide (solid) instead of mercury, so the concentration of iodine is high, and since this concentration is high, current is less likely to flow than discharge lamps using mercury. As a result, it has the property that the discharge lamp current is likely to pause. ,
That is, in the mercury-less discharge lamp as described above, the rated current is satisfied in addition to the normal current pause period at the time of switching between positive and negative polarity in the process from the start of lighting to the steady lighting and the steady power lighting other than the time of dimming lighting. There is a problem that cannot be dealt with in the configuration of the above-mentioned conventional example that a peculiar current quiescent period in which no current flows is generated.

  The present invention has been made to solve the above-described problems.In the process from starting lighting to steady lighting except during dimming lighting and in steady power lighting, the normal current resting period at the time of switching between positive and negative polarity is used. In addition, in a discharge lamp such as a mercury-less lamp that has the characteristic of generating a unique current quiescent period in which a current that is less than the rated current flows, the occurrence of this current quiescent period is prevented or shortened, and the current that does not satisfy the rated current It is an object of the present invention to obtain a discharge lamp lighting device that shortens the time until arc discharge (re-ignition) occurs again even when the lamp flows, and achieves stable lighting without causing flickering or extinction.

  The discharge lamp lighting device according to the present invention has a DC power supply circuit, and based on a rectangular wave AC converted from the generated DC voltage, power is supplied to the discharge lamp so as to shift the discharge lamp from cold lighting to steady lighting. Supplying steady-state power to the discharge lamp based on the current detection signal in periods other than the vicinity of when the discharge lamp lighting section to supply, the current detection section that detects the current flowing to the discharge lamp, and the positive / negative polarity switching of the rectangular wave AC The power supply unit is configured to control the DC power supply circuit so as to increase the steady power in the vicinity of the positive / negative polarity switching.

  According to the present invention, control is performed so that steady power is supplied to the discharge lamp in a period other than the vicinity when the rectangular wave AC is switched between positive and negative polarities, and the supplied power is increased in the vicinity of when switching between positive and negative polarities. Since it has a configuration, the process from the start of lighting other than the time of dimming lighting to the steady lighting and the steady power lighting has the property that a current pause period occurs at the time of switching between positive and negative polarity, while arc discharge stops and arc discharge occurs again In a mercury-less discharge lamp that has the property that a current that does not reach the rated current flows before the occurrence of this current interruption period is prevented or shortened, and when a current that does not satisfy the rated current flows again The time until the arc discharge occurs is shortened, thereby preventing flickering and extinguishing, and the lighting of the discharge lamp can be stabilized.

An embodiment of the present invention will be described below.
Embodiment 1 FIG.
1 is a basic circuit diagram showing a basic configuration of a discharge lamp lighting device according to Embodiment 1 of the present invention.
In FIG. 1, the discharge lamp lighting device includes a power source 1, a discharge lamp lighting unit 2, a current detection unit 3, a high-pressure discharge lamp (hereinafter referred to as “discharge lamp”) 4, and a power control unit 5.

In the above configuration, the power source 1 generates a predetermined DC voltage Vo.
The discharge lamp lighting unit 2 has a DC power supply circuit that generates a predetermined DC voltage V1 based on the DC voltage Vo from the power supply 1, converts the generated DC voltage V1 into a rectangular wave AC, and the rectangular wave Based on the alternating current, electric power is supplied to the discharge lamp 4 so as to shift the discharge lamp 4 from the discharge at the start-up by the glow discharge to the steady lighting by the arc discharge.

  The current detection unit 3 detects a current flowing to the discharge lamp 4 by supplying power from the discharge lamp lighting unit 2 and outputs a current detection signal.

  The discharge lamp 4 is a rectangular wave alternating current in the process from lighting start to steady lighting other than dimming lighting and steady lighting, such as a mercury-free metal halide lamp used for automobile headlamps and the like. In addition to the normal current quiescent period when switching between positive and negative polarity (reversal) during lighting, there is a unique current quiescent period in which current less than the rated current flows before arc discharge stops and arc discharge reaches the rated voltage again. It means a discharge lamp having the property of

The power control unit 5 controls the conversion to the rectangular wave alternating current in the discharge lamp lighting unit 2, while receiving the current detection signal from the current detection unit 3, and switching the positive / negative polarity in the conversion control to the rectangular wave alternating current In a period other than the vicinity of the, the DC power supply circuit of the discharge lamp lighting unit 2 is controlled so as to supply steady power to the discharge lamp 4 based on the current detection signal. Then, the DC power supply circuit of the discharge lamp lighting unit 2 is controlled so that the power supplied to the discharge lamp 4 is increased from the steady power.
The power control unit 5 includes an error amplifier 51, a comparator 52, a CPU 53, and the like.

Next, the internal configuration of the discharge lamp lighting unit 2 will be described with reference to FIG.
FIG. 2 is an internal configuration diagram of the discharge lamp lighting unit 2.
In FIG. 2, the discharge lamp lighting unit 2 includes a DC power supply circuit (hereinafter referred to as “DC / DC converter”) 21, an H-type bridge circuit 22, an igniter 23, and a takeover circuit 24.

In this configuration, the DC / DC converter 21 includes a step-up transformer (flyback transformer) 21a, and a rectifier diode 21b and a smoothing capacitor 21c for rectifying and smoothing AC power generated on the secondary winding side of the transformer 21a into DC. And a power MOS type FET 21d that performs a switching operation according to a power control signal Sa output from the power control unit 5 and controls a current flowing through the primary winding of the transformer 21a. A predetermined DC voltage V1 is generated and output based on the DC voltage Vo.
The power control signal Sa is a pulse signal having a variable width. The wider the pulse width, the higher the DC voltage V1, and the output power as the DC / DC converter 21 increases.

The H bridge circuit 22 converts the DC voltage V1 generated by the DC power supply circuit 21 into a rectangular wave AC. The conversion to the rectangular wave AC is processed according to the rectangular wave control signal Sb output from the CPU 53 of the power control unit 5.
The igniter 23 superimposes a high voltage pulse on the rectangular wave alternating current converted by the H-shaped bridge circuit 22 and applies the high voltage pulse between the electrodes of the discharge lamp 4 to cause breakdown, thereby generating a glow discharge between the electrodes.
The takeover circuit 24 shifts the discharge lamp 4 from the discharge at the start-up by glow discharge to the steady lighting by arc discharge.

Next, the basic operation of FIG. 1 will be described with reference to FIG.
In the DC / DC converter 21 of the discharge lamp lighting unit 2, a power control signal Sa is set by the power control unit 5 so as to output a DC voltage V <b> 1 that is power necessary for flowing a target current to the discharge lamp 4. .
The discharge lamp lighting unit 2 generates a predetermined DC voltage V1 based on the DC voltage Vo from the power source 1 in the DC / DC converter 21 in accordance with the above settings, and the H-type bridge circuit 22 performs power control on the DC voltage V1. According to the rectangular wave control signal Sb output from the unit 5, the rectangular wave AC is converted. The igniter 23 superimposes a high voltage pulse on the rectangular wave alternating current, and applies the high voltage pulse to the discharge lamp 4 to generate glow discharge. The takeover circuit 24 shifts the discharge lamp 4 from the discharge at the start-up by the glow discharge to the steady lighting by the arc discharge.

In the above operation, the current flowing through the discharge lamp 4 by the power supplied from the discharge lamp lighting unit 2 is detected by the current detection unit 3, and the current detection signal Sc is input to the negative phase input terminal (− of the error amplifier 51 of the power control unit 5. ). A target current setting signal Sd for setting a target current value to be passed through the discharge lamp 4 is applied from the CPU 53 to the positive phase input terminal (+) of the error amplifier 51 via the resistor 54.
The error amplifier 51 detects an error (difference) in the current detection signal Sc with respect to the target current setting signal Sd, amplifies it, and converts it into a power control error signal Se. The power control error signal Se is input to the positive phase input terminal (+) of the comparator 52 via the resistor 55. A triangular wave signal Sf is input to the negative phase input terminal (−) of the comparator 52.
The power increase setting signal Sg output from the CPU 53 is input to the positive phase input terminal (+) of the comparator 52 via the resistor 56. As a result, the signals from the two systems of the power control error signal Se and the power increase setting signal Sg are applied to the positive phase input terminal (+) of the comparator 52.

The difference between the power control error signal Se and the power increase setting signal Sg is as follows.
The power control error signal Se is a signal that represents a difference between the target current value and the current value detected by the current detection unit 3, eliminates this difference, and sets the current value detected by the current detection unit 3 to the target current value. It is a signal used to set the power supplied to the discharge lamp 4 to a steady power.
On the other hand, the power increase setting signal Sg is a signal used for setting to increase the target current value in the vicinity of the switching of the positive and negative polarity of the rectangular wave current flowing through the discharge lamp 4, thereby increasing the power supplied to the discharge lamp 4. It is.

The reason why the two systems of the power control error signal Se and the power increase setting signal Sg described above are used will be described with reference to FIGS.
FIG. 3 is a waveform diagram showing the voltage (a) of the discharge lamp 4 and the current (b) of the discharge lamp 4 when only the power control error signal Se is excluded from the power increase setting signal Sg.
On the other hand, FIG. 4 shows the voltage (a) of the discharge lamp 4, the current (b) of the discharge lamp 4, and the target current setting (when the two systems of the power control error signal Se and the power increase setting signal Sg are used. It is a wave form diagram which shows c).
In FIG. 3, the voltage and current of the discharge lamp 4 show a normal rectangular waveform during the period T1, and no current interruption occurs when the rectangular wave current (b) is switched between positive and negative polarity.

On the other hand, during the period T2, the current is momentarily interrupted when the rectangular wave current (b) is switched between positive and negative polarity. When this current interruption occurs, the voltage of the rectangular wave voltage (a) increases as shown by e1, but returns to the normal voltage when re-ignited (arc discharge). The reason why the voltage rises in this way is that the power supplied to the discharge lamp 4 by the DC / DC converter 21 of the discharge lamp lighting unit 2 is controlled to be constant. This is because the applied voltage rises sharply.
In the period T3, it is shown that a current interruption longer than that in the period T2 occurs when the rectangular wave current (b) is switched between positive and negative polarity.
In addition, in the period T4, after the current is momentarily interrupted when the rectangular wave current (b) is switched between the positive and negative polarities, the current less than half of the normal current (rated current) flows before re-ignition. .

In the case of a phenomenon such as this period T4, as shown by e2, the rectangular wave voltage (a) is required to reach a voltage required for re-ignition because current flows through the discharge lamp 4 even if it is below the rated current. Time will increase. The reason why this time is increased is that the power supplied to the discharge lamp 4 by the DC / DC converter 21 is kept constant as described above, so that even if a small amount of current flows, the voltage is its current value. This is due to the fact that the voltage rises slowly. Accordingly, the time until the re-ignition is delayed as the increase in the voltage is delayed.
The phenomenon such as the period T4 is a phenomenon that occurs remarkably in the mercury-less discharge lamp 4, and can be said to be a current pause period that occurs remarkably in the mercury-less discharge lamp 4.
Further, the phenomena such as the periods T2 and T3 are similar to the phenomenon that occurs when the high pressure discharge lamp containing mercury is dimmed, and in this respect, it can be said to be a normal current pause period that is distinguished from the current pause period described above. Is. However, even in the normal current rest period, the mercury-less discharge lamp 4 is prominently generated during the switching from positive to negative polarity in the process from lighting start to steady lighting other than dimming lighting and steady power lighting. Is different.

Next, in FIG. 4, the period T1 and the period T2 are the same as the state of FIG. 3, and the period T5 corresponding to the period T3 in FIG. 3 and the period T6 corresponding to the period T4 in FIG. It shows that the interruption of current at the time of switching between positive and negative polarity of b) is improved. It is the power increase setting signal Sg that achieves this improvement. As shown in FIG. 4C, this power increase setting signal Sg has a period Tw in the vicinity of the switching of the positive and negative polarity of the rectangular wave current (b). The target current set by the power control error signal Se is increased.
Due to the action of the power increase setting signal Sg, the DC / DC converter 21 of the discharge lamp lighting unit 2 is controlled so as to increase the power supplied to the discharge lamp 4 during the period Tw. Even in a state where current is interrupted or a small amount of current less than the rated current flows within the period Tw, the voltage rises quickly and the time until re-ignition is shortened.

For example, as indicated by e3, the rectangular wave voltage (a) for the period T5 in which the current is interrupted has a rapid increase in voltage and improved re-ignition performance.
In addition, in the rectangular wave current (b) in the period T6, the current flowing before re-ignition increases as the voltage continues to rise, leading to stable re-ignition. In the rectangular wave voltage (a), As indicated by e4, the increase in power supply maintains the voltage rise even when a small amount of current flows, ensuring re-ignition.

Next, a specific measure for increasing the target current shown in FIG. 4C will be described with reference to FIG.
FIG. 5 is a waveform diagram showing the voltage (a) of the discharge lamp 4, the current (b) of the discharge lamp 4, the input (c) of the comparator 52, and the output (d) of the comparator 52 near the square wave positive / negative polarity switching. It is.
In FIG. 5, the period T6 of the voltage (a) and current (b) of the discharge lamp 4 is an enlargement of T6 of FIG. 4, and even if a small amount of current less than the rated current flows before re-ignition. As the voltage rise continues, the current increases, indicating re-ignition.
As shown in FIG. 1 and FIG. 4 (c), the input of the comparator 52 for ensuring such re-ignition is applied to the positive phase input terminal (+) in the period Tw in the vicinity of the positive / negative polarity switching. A signal (Se + Sg) obtained by adding the power increase setting signal Sg to the power control error signal Se is input, and only the power control error signal Se is input in a period other than the period Tw, and a triangular wave signal is input to the negative phase input terminal (−). Sf is input.

In response to such an input, the comparator 52 outputs a pulse signal whose pulse width is a period of the triangular wave signal Sf that is equal to or lower than the level of the signal Se or the signal (Se + Sg), as shown in FIGS. (FIG. 5D). Therefore, the pulse width Te is applied to the signal Se having a low level, and the pulse width Tg is applied to the signal (Se + Sg) added with the level. As can be understood from the figure, “pulse width Tg> pulse width Te”.
In this way, the comparator 52 outputs a pulse signal having a wide pulse width in the period Tw near the time of switching between positive and negative polarity, and this output signal is used as the above-described power control signal Sa, and the DC / DC converter 21 of the discharge lamp lighting unit 2. Is applied to the FET 21d (FIG. 2).

The DC / DC converter 21 to which the power control signal Sa is applied has a higher on-period (on-duty) of the FET 21d as a switching element when a signal with a wide pulse width is compared with a signal with a narrow pulse width. The operation is to increase V1 by increasing the output power. As a result, in the period Tw in the vicinity of the switching of the positive and negative polarity of the rectangular wave, the voltage rise continues due to the increase in the power supplied to the discharge lamp 4, and the effect described in FIG. 4 is obtained.
As can be understood from FIGS. 5C and 5D described above, switching occurs when the level of the signal obtained by adding the power increase setting signal Sg to the power control error signal Se exceeds the peak value of the triangular wave signal Sf. The FET 21d as an element is always on and does not switch, and does not function as a DC / DC converter.
Accordingly, it is necessary to always set the level of the signal obtained by adding the power increase setting signal Sg to the power control error signal Se within the peak value of the triangular wave signal Sf.

Next, the setting period of the period Tw in relation to the lighting process of the discharge lamp 4 is set in advance in the CPU 53 in consideration of the characteristics of the discharge lamp 4 and the like. For example, the period Tw is set when a transition is made from cold lighting due to a large current after long-time extinction to steady lighting, and the power supplied to the discharge lamp 4 is increased.
Here, the state of transition from cold lighting to steady lighting is almost determined for each discharge lamp 4, and can be set in the CPU 53 in advance.
Alternatively, the period Tw may be set even during steady lighting so that the power supplied to the discharge lamp 4 is increased. In this case as well, the CPU 53 is set in advance in consideration of the characteristics of the discharge lamp 4 and the like.

Further, the specific period of the period Tw set in the vicinity of the square wave positive / negative polarity switching is set in advance in the CPU 53 in consideration of the characteristics of the discharge lamp 4 and the like. For example, the start point of the period Tw is set immediately before, immediately after or simultaneously with the switching of the positive / negative polarity, and the end point of the period Tw is appropriately set.
However, this period Tw is set to a period longer than the period in which the current increases from the current less than the rated current to the rated current in consideration of at least the specific current pause period described above.
Here, as explained in FIG. 2, the CPU 53 controls the conversion to the rectangular wave AC by the H-shaped bridge circuit 22 of the discharge lamp lighting unit 2 by the rectangular wave control signal Sb. The above timing Tw can be set.

  As described above, according to the first embodiment, the power control unit 5 uses the discharge lamp based on the current detection signal from the current detection unit 3 in a period other than the vicinity of when the rectangular wave alternating current is switched. 4 is configured to control the DC power supply circuit 21 of the discharge lamp lighting unit 2 so as to supply the steady power to 4 and to control the DC power supply circuit 21 so as to increase this steady power in the vicinity of the positive / negative polarity switching. Therefore, as in the case of discharge lamps such as mercury-free metal halide lamps used for automobile headlamps, etc. In discharge lamps that have the unique property that the arc discharge is interrupted and the current that is less than the rated current flows before the arc discharge occurs again, In addition, when a current less than the rated current flows, the time until arc discharge occurs again is shortened, thereby preventing flickering and extinguishing, and stabilizing the lighting of the discharge lamp. Can be

Embodiment 2. FIG.
6 is a circuit diagram showing a configuration of a discharge lamp lighting device according to Embodiment 2 of the present invention.
6, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.
6 basically differs from the configuration of the first embodiment (FIG. 1) in that a circuit using an NPN transistor 57 is provided in the power increase setting signal Sg line of the power control unit 5a. The other circuits are basically the same as those in FIG. 1 although the circuit configuration is different. The function as the power control unit 5a is also the same as that of the power control unit 5 in FIG.

Next, the operation will be described focusing on differences from the power control unit 5 of FIG.
In the configuration of FIG. 1, the power increase setting signal Sg output by the CPU 53 during the power increase period Tw is input to the positive phase input terminal (+) of the comparator 52 via the resistor 56.
In contrast, the CPU 53a of the power control unit 5a shown in FIG. 6 outputs Hi (high to 5V, for example) as the power increase setting signal Sg during the power increase period Tw. Further, in a period other than the period Tw, the CPU 53a maintains Lo (low to, for example, 0 V).
The output Hi power increase setting signal Sg is applied to the base (B) of the transistor 57 via the resistor 58 and the diode 59. As a result, the collector (C) and the emitter (E) of the transistor 57 are turned on, and the voltage from the DC power source Vcc (for example, 5 V) is input to the comparator 52 via the resistor 60 as the power increase setting signal Sg ′. Applied to terminal (+).

This power increase setting signal Sg ′ is the emitter (E) voltage of the transistor 57. This emitter (E) voltage is obtained when the power increase setting signal Sg of Hi output from the CPU 53a in the power increase period Tw is 5V. The voltage between BE of the transistor 57 (Vbe: normally 0.7 V) and the forward voltage between the anode (A) and the cathode (K) of the diode 59 (usually 0.7 V) indicate “5V− (0.7V × 2 ) = 3.6V ”, and clipped to 3.6V or less unless Hi = 5V is increased.
Therefore, even if the collector current of the transistor 57 is increased for some reason, the emitter (E) voltage of the transistor 57 does not exceed the above-mentioned 3.6 V, and an unnecessary increase in power is prevented.

  In the Lo output period of the CPU 53a, the power control error signal Se generated by the error amplifier 51, the diode 61, and the resistors 62 and 63 is applied to the positive phase input terminal (+) of the comparator 52 via the resistor 64. This power control error signal Se is used for setting at the time of steady power output as in the first embodiment.

The input side of the comparator 52 to which the power increase setting signal Sg ′ and the power control error signal Se are input will be described with reference to FIG. FIG. 7 is an input waveform diagram of the comparator 52.
As shown in FIG. 7, in contrast to the triangular wave signal Sf input to the negative phase input terminal (−) of the comparator 52, the positive phase input terminal (+) has the power increase setting signal Sg ′ in the power increase period Tw. It is set to 3.6 V, and is set to the power control error signal Se generated by the error amplifier 51 or the like in a period other than the period Tw.
Thus, steady power is supplied to the discharge lamp 4 by the power control error signal Se in a period other than the period Tw, and steady power is supplied to the discharge lamp 4 by 3.6 V of the power increase setting signal Sg ′ in the period Tw. Increased power is supplied.
Further, as the power increase setting signal Sg ′ is clipped to 3.6 V as described above, the power increase setting signal Sg ′ is always set within the peak value (4 V) of the triangular wave signal Sf. The function stop of the DC / DC converter 21 of the described discharge lamp lighting unit 2 is prevented.
The subsequent operation is the same as described with reference to FIGS. 5C and 5D, and the description thereof is omitted.

  As described above, according to the second embodiment, a circuit using the diode 59, the transistor 57, and the like is provided in the line of the power increase setting signal Sg of the power control unit 5a, and the CPU 53a switches the positive / negative polarity of rectangular wave alternating current. In the vicinity of the hour, Hi is output to turn on the transistor 57, and in the vicinity other than the time of switching between positive and negative polarity, Lo is output to turn off the transistor 57. When this is turned on, the power supplied to the discharge lamp 4 is increased. Since it is configured to supply steady power, the same effect as in the first embodiment, that is, the occurrence of a current pause period when switching between positive and negative polarity is prevented or shortened, and arc discharge is interrupted and arc discharge is generated again. Even if a current that is less than the rated current flows before the arc discharge, the time until the arc discharge occurs again is reduced, thereby preventing flickering and extinction. It is possible to stabilize the lighting of the silver-less discharge lamp 4.

  Further, the emitter (E) voltage of the transistor 57, that is, the power increase setting signal Sg ′ is reduced to a certain value (for example, 3.6 V) or less by the BE voltage of the transistor 57 (Vbe) and the forward voltage of the diode 59. As a result, the rise of the emitter (E) voltage can be suppressed even when the collector current of the transistor 57 is increased, and an unnecessary increase in power can be prevented.

  Further, by clipping the power increase setting signal Sg ′, the power increase setting signal Sg ′ is always set within the peak value of the triangular wave signal Sf, and the function of the DC / DC converter 21 of the discharge lamp lighting unit 2 is stopped. Can be prevented.

Embodiment 3 FIG.
FIG. 8 is a circuit diagram showing a configuration of a discharge lamp lighting device according to Embodiment 3 of the present invention.
8, the same components as those in FIG. 1 or FIG. 6 are denoted by the same reference numerals, and description thereof is omitted.
The configuration in the third embodiment shown in FIG. 8 is that a PNP transistor 65 is provided in the power control unit 5b as compared with the configuration of the power control unit 5a in FIG. 6 (second embodiment). The purpose of the transistor 65 is to suppress an increase (increase) of the power increase setting signal Sg ′ more than necessary, and to suppress power supplied to the discharge lamp 4 by the DC / DC converter 21 of the discharge lamp lighting unit 2. That is, the transistor 65 serves as power increase limiting means for limiting an increase in power supplied to the discharge lamp 4.

As described in FIG. 6, when the CPU 53a outputs Hi (for example, 5 V) during the power increase period Tw, the transistor 57 is turned on. When the emitter (E) voltage of the transistor 57 due to this ON is Ve, this Ve becomes the forward bias of the transistor 65 and the transistor 65 is turned on. With this ON, the collector current Ic of the transistor 57 is The current Ie flowing from the emitter (E) to the grounded collector (C) is divided into the current Ia flowing to the resistor 64 side. A resistor 60 provided at the collector (C) of the transistor 57 prevents the DC power source Vcc from being grounded when the transistor 65 is turned on.
If the base (B) voltage of the transistor 65 in the above state is Vb, the potential difference from Ve, which is also the emitter (E) voltage of the transistor 65, is always constant as the BE voltage (usually 0.7 V) of the transistor 65. And Vb <Ve.

  Here, the base voltage Vb of the transistor 65 means the power control error signal Se generated by the error amplifier 51 and the like, and the emitter voltage Ve of the transistor 57 (or transistor 65) is the power increase setting signal Sg ′. Thus, the power increase setting signal Sg ′ is always clipped to the voltage obtained by adding the BE voltage (0.7 V) of the transistor 65 to the power control error signal Se from the above, and the increase to this voltage is suppressed. The Thereby, the electric power supplied to the discharge lamp 4 is limited, and an unnecessary electric power supply is avoided.

The input side of the comparator 52 to which the power increase setting signal Sg ′ and the power control error signal Se are input will be described with reference to FIG. FIG. 9 is an input waveform diagram of the comparator 52.
As shown in FIG. 9, with respect to the triangular wave signal Sf input to the negative phase input terminal (−) of the comparator 52, the positive phase input terminal (+) has an error amplifier 51 and the like in a period other than the power increase period Tw. In the power increase period Tw, the power increase setting signal Sg ′ is set to a voltage obtained by adding the BE voltage (0.7 V) of the transistor 65 to the power control error signal Se. Clipped.
Thus, steady power is supplied to the discharge lamp 4 by the power control error signal Se in a period other than the period Tw, and the voltage between BE of the transistor 65 (0.7 V) is supplied to the power control error signal Se in the period Tw. The increased power is supplied to the discharge lamp 4 by the added power increase setting signal Sg ′.

As a setting method of the power increase limitation by the transistor 65 described above, for example, the steady power by the power control value signal Se is normally set to the rated power of the discharge lamp 4, but this steady power is set lower than the rated power, The average value of the increased power set by the power increase setting signal Sg ′ in the increase period Tw and the steady power is set to the rated power of the discharge lamp 4 to prevent excessive power supply.
The subsequent operation is as described in the first embodiment or the second embodiment, and the description thereof is omitted.

  As described above, according to the third embodiment, since the power increase limiting means using the transistor 65 is provided in the configuration of the second embodiment, unnecessary power supply to the discharge lamp 4 is suppressed. The necessary and sufficient power can be supplied.

Embodiment 4 FIG.
FIG. 10 is a circuit diagram showing a configuration of a discharge lamp lighting device according to Embodiment 4 of the present invention.
10, the same components as those in FIG. 1, FIG. 6, or FIG. 8 are denoted by the same reference numerals, and description thereof is omitted.
In the second embodiment (FIG. 6) or the third embodiment (FIG. 8), the transistor 57 that is turned on in the power increase period Tw is provided.
On the other hand, the configuration of the fourth embodiment shown in FIG. 10 is that an NPN transistor 66 that is turned off in the power increase period Tw by the power control unit 5c is provided as shown in FIG.

A diode 67 is provided between the collector (C) and the emitter (E) of the transistor 66 in the direction shown in the figure, and there is an error at the connection point between the cathode (K) of the diode 67 and the emitter (E) of the transistor 66. The output terminal of the amplifier 51 is connected, and resistors 68 and 69 are provided at the base (B) of the transistor 66. The power increase setting signal Sg is applied to the base (B) of the transistor 66 from the CPU 53b via the resistor 68.
A DC power source Vcc (for example, 5 V) is connected to a resistor 62 and a resistor 63 at a connection point between the positive phase input terminal (+) of the comparator 52 and the collector (C) of the transistor 66 and the anode (A) of the diode 67. A DC voltage divided by is applied.

Here, in the steady power period other than the power increase period Tw, the CPU 53b controls to turn on the transistor 66. The power control error signal Se applied to the positive phase input terminal (+) of the comparator 52 in this on state is an output signal of the error amplifier 51 because the transistor 66 is on. For example, if the output signal of the error amplifier 51 is “3V”, the power control value signal Se applied to the positive phase input terminal (+) of the comparator 52 is “3V”. This power control error signal Se becomes a voltage lower than the DC voltage obtained by dividing the DC power supply Vcc by the resistors 62 and 63. This is because the voltage across the resistor 63 is drawn into the output signal of the error amplifier 51 when the transistor 66 is turned on.
Based on the power control error signal Se, the comparator 52 sets the DC / DC converter 21 of the discharge lamp lighting unit 2 so that the power supplied to the discharge lamp 4 is in a steady power state.

Next, in the power increase period Tw, the CPU 53b turns off the transistor 66. By turning off the transistor 66, the positive phase input terminal (+) of the comparator 52 and the output terminal of the error amplifier 51 are connected via the diode 67. The forward voltage from the anode (A) to the cathode (K) of the diode 67 is normally “0.7 V”. Therefore, for example, if the output signal of the error amplifier 51 is “3 V”, the power control value in the power increase period Tw applied to the anode (A) side of the diode 67, that is, the positive phase input terminal (+) of the comparator 52. The signal Sg ′ becomes “3.7 V” obtained by adding the forward voltage (0.7 V) to the output signal “3 V” of the error amplifier 51.
Since the forward voltage of the added diode 67 is constant, the power increase setting signal Sg ′ during the power increase period Tw is always in this order with respect to the power control error signal Se other than the power increase period Tw (steady power period). The directional voltage is clipped to the added voltage, and the rise above this voltage is suppressed. Thereby, the electric power supplied to the discharge lamp 4 is limited, and an unnecessary electric power supply is avoided. Thus, the diode 67 serves as a power increase limiting unit that limits an increase in power supplied to the discharge lamp 4.

  As described above, according to the fourth embodiment, the configuration in which the transistor 66 is turned off in the power increase period Tw is different from the configuration in the second or third embodiment in which the transistor 57 is turned on in the power increase period Tw. Therefore, this configuration also has the same effect as that of the first embodiment, that is, prevents or shortens the occurrence of a current pause period at the time of switching between positive and negative polarity, and is rated before arc discharge stops and arc discharge occurs again. Even when a current less than the current flows, the time until arc discharge occurs again is shortened, thereby preventing flickering and extinguishing, and lighting of the mercury-less discharge lamp 4 can be stabilized.

  In addition, since the power increase limiting means by the diode 67 provided between the collector (C) and the emitter (E) of the transistor 66 is provided, unnecessary power supply to the discharge lamp 4 is suppressed, and necessary and sufficient. Electric power can be supplied.

It is a basic circuit diagram which shows the basic composition of the discharge lamp lighting device by Embodiment 1 of this invention. It is an internal block diagram of the discharge lamp lighting part in FIG. It is a wave form diagram which shows the voltage (a) and electric current (b) of a discharge lamp for demonstrating the discharge lamp lighting device by Embodiment 1 of this invention. It is a wave form diagram which shows the voltage (a) of the discharge lamp, current (b), and target current setting (c) for demonstrating the discharge lamp lighting device by Embodiment 1 of this invention. In order to explain the discharge lamp lighting device according to Embodiment 1 of the present invention, the voltage (a), current (b), input (c) of the comparator, input of the comparator, and the comparator It is a wave form diagram which shows an output (d). It is a circuit diagram which shows the structure of the discharge lamp lighting device by Embodiment 2 of this invention. It is an input waveform figure of the comparator for demonstrating the discharge lamp lighting device by Embodiment 2 of this invention. It is a circuit diagram which shows the structure of the discharge lamp lighting device by Embodiment 3 of this invention. It is an input waveform figure of the comparator for demonstrating the discharge lamp lighting device by Embodiment 3 of this invention. It is a circuit diagram which shows the structure of the discharge lamp lighting device by Embodiment 4 of this invention.

Explanation of symbols

  1 power supply, 2 discharge lamp lighting unit, 3 current detection unit, 4 high pressure discharge lamp, 5, 5a, 5b, 5c power control unit, 21 DC / DC converter, 22 H bridge circuit, 23 igniter, 24 takeover circuit, 51 Error amplifier, 52 Comparator, 53, 53a, 53b CPU, 57, 65, 66 Transistor, 59, 61, 67 Diode.

Claims (3)

It has a DC power supply circuit that generates DC voltage, converts the generated DC voltage into rectangular wave alternating current, and based on this rectangular wave alternating current, the discharge lamp is switched from discharge at start-up by glow discharge to steady lighting by arc discharge. A discharge lamp lighting unit for supplying power to the discharge lamp so as to maintain the steady lighting;
A current detection unit for detecting a current flowing to the discharge lamp by power supply by the discharge lamp lighting unit;
While controlling the conversion to the rectangular wave alternating current, a current detection signal is input from the current detection unit, and the discharge is performed based on the current detection signal in a period other than the vicinity when the positive / negative polarity switching of the rectangular wave alternating current is performed. The output power in the DC power supply circuit of the discharge lamp lighting unit is controlled so as to supply the steady power to the electric lamp, and the electric power supplied to the discharge lamp is changed to the steady power in the vicinity of the positive / negative polarity switching of the rectangular wave alternating current. A discharge lamp lighting device comprising: a power control unit that controls output power in the DC power supply circuit so as to further increase.   The power control unit controls to increase the power supplied to the discharge lamp in the vicinity of the switching of the positive and negative polarity of the rectangular wave alternating current during the process of transitioning to the steady lighting from immediately after lighting and during steady lighting. The discharge lamp lighting device according to claim 1.   The discharge lamp lighting device according to claim 1, wherein the power control unit includes a power increase limiting unit that limits an increase in power supplied to the discharge lamp in the vicinity of the switching of the positive / negative polarity of the rectangular wave alternating current.

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