JPS6188499A - High voltage discharge lamp lighting apparatus - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a high pressure discharge lamp lighting device having a dimming function.

[Technical Background of the Invention] Conventionally, as this type of high-pressure discharge lamp lighting device, one shown in FIG. 4, for example, is known. This is a lighting circuit that controls the current flowing through the lamp by controlling the switching of transistors.The specific configuration is an NPN switching transformer between the DC power terminals (+) and (-), a transistor 1, and a current detection circuit. A diode 3 is connected to the polarity shown in the figure through a resistor 2 in series, and a capacitor 5 and a starting circuit 6 are connected roughly through a current limiting coil 4, and a pulse transformer of the starting circuit 6 is connected to the capacitor 5. The high pressure discharge lamp 7 is connected via the secondary winding 61. The starting circuit 6 has an SSS element 6 connected to a capacitor 63 of a series time constant circuit consisting of a resistor 62 and a capacitor 63.
It is formed by connecting the primary windings of the pulse transformer 61 in parallel via 4. The switching transistor 1 is operated in response to the voltage across the resistor 2 by a control circuit 8 that controls, for example, its switching duty ratio. The control circuit 8 includes an average value circuit 81 that integrates and averages the voltage across the resistor 2, a reference voltage a82, and inputs the output voltage of this reference power source 82 to an input terminal (-), and calculates the average value. An error amplifier 84 inputs the output of the circuit 81 to the input terminal (+) and connects a feedback resistor 83 between the input terminal (-) and the output terminal, and P that controls the switching duty ratio
WM (pulse width modulation) control circuit 85.

In this device, when the impedance of the high-pressure discharge lamp 7 decreases during lighting operation of the high-pressure discharge lamp 7, the current flowing through the discharge lamp 7 increases, but at this time, the voltage generated across the resistor 2 also increases, and the error amplifier 84 input terminals (
+) becomes larger. Here, if the gain of the error amplifier 84 is set small, the output type B
does not reach that extent. Therefore, the switching duty ratio of the switching transistor 1 by the PWM control circuit 85 does not change significantly, and the amount of current supplied to the discharge lamp 7 is maintained at a relatively large amount. In this way, it is possible to keep the lamp power approximately constant.

[Problems with the Background Art] Recently, the applicant has been trying to develop a high-pressure discharge lamp lighting device of this type that is equipped with a dimming function to dimly light the high-pressure discharge lamp (for example, the error amplifier 8
This can be achieved by lowering the voltage input to the input terminal (-) of No. 4. ), but when lighting dimly in such a device, the lamp current is lower than when lighting at full brightness, so the problem is that the arc discharge cannot be maintained properly immediately after the transition from glow discharge to arc discharge at the time of starting and restarting. This causes a problem in that it is practically impossible to maintain the discharge of NM after transition to arc discharge, especially when restarting the tube immediately after extinguishing the lamp while it is still warm.

[Purpose of the Invention] This invention was devised to solve such problems, and it does not only work when the light is turned on in the full-light mode, but also when it is turned on in the dimming mode, regardless of whether it is first turned on or re-lighted. It is an object of the present invention to provide a high-pressure discharge lamp lighting device that can reliably maintain arc discharge immediately after transition from glow discharge to arc discharge, and can always perform good starting and lighting operations.

[Summary of the Invention] The present invention provides a high-pressure discharge lamp lighting device having a dimming function, which includes a mode selection means for selecting a full light mode and a dimming mode, and a mode selection means that selects the dimming mode and starts lighting. This lamp is equipped with a control means that causes the same lamp current to flow through the high-pressure discharge lamp for a short period of time immediately after starting the lamp when the lamp is started, and is equivalent to that when starting the lamp in full-light mode. During the first short period of time, the lamp current is made to flow in the same way as when starting the lamp in full light mode.

[Embodiments of the invention] Embodiments of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, a DC power supply 10 includes an NPN switching transistor 11 and current detection resistors 12 and 13.
The diode 14 is connected in series with the polarity shown, and the capacitor 16 is connected roughly through the current limiting coil 15.
are connected. A starting circuit 17 is connected in parallel to the capacitor 16, and a high pressure discharge lamp 18 is connected in parallel via the secondary winding of a pulse transformer 171 of the starting circuit 17.

The starting circuit 17 is similar to the starting circuit shown in FIG. It is formed by

The switching transistor 11 is switched in response to the voltage across the resistor 12 by a control circuit 19 that controls, for example, its switching duty ratio. This control circuit 19 includes the resistor 1
Average value circuit 191 that integrates and averages the voltage between both ends of 2.
The output of this average value circuit 191 is inputted to an input terminal (+), and a feedback resistor 192 is connected between the input terminal (-) and the output terminal of the error amplifier 193, and the output of this error amplifier 193. It is formed by a PWM (pulse width modulation) control circuit 194 that controls the switching duty ratio of the switching transistor multiplicity 11 according to the voltage level. Note that a reference voltage is supplied to the input terminal (-) of the error amplifier 193 from a reference power supply 20 via an all-light mode/dimming mode switching circuit 21. The switching circuit 21 connects a series circuit of a resistor 212 and an all-light mode/dimming mode changeover switch 213 to a resistor 211 in parallel, and connects a resistor 214 in series to the parallel circuit to connect the series circuit to the reference power source. 20, and a PNP type transistor 215 connected to the changeover switch 213.
The resistors 211.
212, a parallel circuit consisting of a changeover switch 213 and a resistor 2
14 is connected to the input terminal (-) of the error amplifier 193.
) is connected to.

Furthermore, resistors 22, 23, 24 and NPN are added to the resistor 13.
A series circuit of the resistor 24 and the transistor 25 is connected in parallel, and a series circuit of the resistor 24 and the transistor 25 is connected in parallel to the reference power supply 20. In addition, the reference power source 2
0 has a resistor 26.27 and an NPN type transistor 28.
Series circuits consisting of are connected in parallel. A capacitor 29 is connected in parallel to the transistor 28, and the base of the transistor 28 is connected to the collector of the transistor 25 via a resistor 30.

Further, the connection point of the resistors 26 and 27 is connected to the base of the transistor 215.

An amplifier circuit 31 for current detection is connected between the connection point between the resistors 22 and 23 and the connection point between the resistors 12 and 13. This amplifier circuit 31 includes an operational amplifier 311 and an input terminal (+) connected to one input terminal (+) of this operational amplifier 311.
A resistor 314 is connected to the other input terminal (-), and a diode 315 is connected to the output terminal. In detail, a series circuit of resistors 312 and 313 constituting a voltage dividing circuit is connected to the reference power supply 20.
The input terminal (+) is connected to the connection point between the resistors 312 and 313, and the other input terminal ( −
) is connected to the connection point between the resistors 21 and 22, and is also connected to the output terminal via a resistor 314 that determines the gain.

Its output terminal is connected to the timer circuit 32 via a diode 315 in the forward direction.

The timer circuit 32 includes a CR time constant circuit including a resistor 321 and a capacitor 322, and a capacitor 32 of this time constant circuit.
The transistor 25 responds to the charging voltage of 2.

In the device according to the embodiment of the present invention configured as described above, when the full-light mode/dimming mode selector switch 213 is turned on to set the full-light mode and starting lighting is started in this state, the starting circuit 17 is first turned on. When activated, the charging voltage of the capacitor 173 causes the SSS element 174 to conduct, generating a high-voltage pulse voltage in the pulse transformer 171, and this pulse voltage is applied to the high-pressure discharge lamp 18. By repeating the application of this pulse voltage several times, the high-pressure discharge lamp starts glow discharge, and then transitions to arc discharge.

Since the changeover switch 213 is on at this time, the level of the reference voltage applied to the input terminal (-) of the error amplifier 193 is relatively high, and therefore a relatively large current flows through the switching transistor 11. The output of the error amplifier 193 becomes non-inverted for the first time, and PWMυ1
The 111 circuit 194 performs switching control in a direction to suppress the current of the switching transistor 11. This thing is ^^
This allows a relatively large lamp current to flow through the pressure discharge lamp 18, thereby ensuring that arc discharge is maintained immediately after the transition from glow discharge to arc discharge in the high pressure discharge lamp 18.

When the high-pressure discharge lamp 18 is operated in full-light mode in this way, a large lamp current flows, so not only when the lamp is first lit, but also immediately after the transition from glow discharge to arc discharge, even when lighting it again. The arc discharge is maintained reliably, and the high-pressure discharge lamp 18 always starts and lights satisfactorily.

In addition, when the full light mode/m light mode selector switch 213 is turned off to set the dimming mode and start lighting is started in this state, the starting circuit 17 is activated first and the charging voltage of the capacitor 173 is used. The SSS element 174 becomes conductive and a high voltage pulse voltage is generated in the pulse transformer 171, and the pulse voltages of 1 and 1 are applied to the high pressure discharge lamp 18. By repeating the application of this pulse voltage several times, a high voltage discharge occurs. The electric light begins to glow discharge, and then transitions to arc discharge.At this time, selector switch 2 is pressed.
13 is off, so if the transistor 215 is off, the level of the reference voltage applied to the input terminal (-) of the error amplifier 193 becomes the divided voltage of the resistors 211 and 214, and the selector switch 213 is turned on. This will be lower than if you had done so.

However, immediately after the start of lighting, the charge level of the capacitor 322 of the timer circuit 32 due to the output of the amplifier circuit 31 has not reached the level that turns on the transistor 25, so the transistor 25 is in an off state.

Therefore, both transistors 28 and 215 are turned on, and the transistor 215 causes the changeover switch 2 to turn on.
13 is turned on. Therefore, the level of the reference voltage applied to the input terminal (-) of the error amplifier 193 is relatively low as in the all-light mode, and in this dimming mode, the starting lighting is started in the same way as in the all-light mode described above. Immediately after, a large lamp current flows through the high pressure discharge lamp 18.

To explain the operation around the amplifier circuit 31, the potential at the connection point between the resistors 22 and 23, which determines the input level of the input terminal (-) of the operational amplifier 311, is higher after the arc of the high-pressure discharge lamp 18 has shifted. It will be lower than before the arc transition. At this time, the resistance values of the resistors 312 and 313 are set appropriately, and the operational amplifier 311 changes from an inverted state before the arc transition to a non-inverted state after the arc transition due to the change in the input level of the input terminal (-). The output is then supplied to the timer circuit 32. As a result, capacitor 322 is gradually charged and transistor 25 is turned on after a short period of time. This time is preferably 0.2 to 3 seconds, for example. As a result, transistor 28, which had been on until then, is turned off, and transistor 215, which had been on until then, is also turned off. Further, in this embodiment, the transistor 215 does not suddenly turn off, but because a charging current flows through the capacitor 29, the impedance of the transistor 215 gradually decreases, and finally it turns off.

In this way, immediately after the start of lighting, as shown by the solid line waveform in FIG. 2, the lamp current IL is larger than the dotted line waveform when the changeover switch 213 is turned off without connecting the transistor 215 in parallel to the changeover switch 213. As a result, the high-pressure discharge lamp 18 reliably maintains arc discharge immediately after the transition from glow discharge to arc discharge, similarly to when starting lighting in the full light mode. At this time, the lamp voltage Vt changes as shown in FIG. Here, time t1 represents the time until the transistor 25 is turned on and until the transistor 28 is turned off, and time 1t2 is the time when the transistor 215 is completely turned off after the transistor 25 is turned on (after the transistor 28 is turned off). It represents the time until.

After a short period of time, when the transistor 25 is turned on by the charging voltage of the capacitor 322 of the timer circuit 32, the transistor 28 is inverted from on to off, and the transistor 28 is turned on.
15 also begins to be inverted from on to off, and during this transition period, transistor 28 does not invert immediately but gradually shifts to off as the charge level of capacitor 29 increases. As mentioned above, the transistor 215 also gradually turns off.
The input level of the input terminal (-) of the error amplifier 193 will gradually decrease. As a result, the lamp current flowing through the high-pressure discharge lamp 18 gradually decreases, and eventually reaches a dimming lighting level.

At this time, the arc discharge of the old pressure discharge lamp 18 has become stable, and stable lighting is maintained thereafter.

In this way, even when the pressure discharge lamp 18 is lit in the dimming mode, a large lamp current flows immediately after the start of lighting, just as in the full light mode, so in this case as well, of course, when lighting for the first time, even if Even in the case of relighting, the arc discharge is reliably maintained immediately after the transition from glow discharge to arc discharge, and the pressure discharge lamp 18 always starts and lights satisfactorily.

In the above embodiment, the golden light mode/dimmer mode changeover switch 213 was connected in parallel with the resistor 211, but it is not necessarily limited to this, and may be connected in parallel with the resistor 214. In this example, the on/off state of the switch is reversed between the full light mode and dimming mode.

Further, the present invention is applicable not only to DC lighting but also to AC lighting, and the control method is not limited to PWM control but can also be applied to frequency modulation and other communication systems.

C. Effects of the Invention As detailed above, according to the present invention, arcs are removed from glow discharge regardless of initial lighting or relighting, not only when lighting in full-light lighting mode but also when lighting in dimming mode. It is possible to provide a high-pressure discharge lamp lighting device that can reliably maintain arc discharge immediately after transition to discharge, and can always perform good starting and lighting operations.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a waveform diagram showing changes in lamp current during dimming in the same embodiment.
FIG. 3 is a waveform diagram showing changes in lamp voltage during dimming in the same embodiment, and FIG. 4 is a circuit diagram showing a conventional example. 11... Switching transistor, 12.13...
・Resistor for current detection, 17... Starting circuit, 18...
High pressure discharge lamp, 19... Control circuit, 20... Reference power supply, 21... Full light mode/dimming mode switching circuit, 213
...Full light mode/dimming mode selector switch, 215.
...PNP type transistor, 32...timer circuit.

Claims (1)

[Claims] A high-pressure discharge lamp lighting device having a dimming function includes a mode selection means for selecting a full light mode and a dimming mode, and when the dimming mode is selected by the mode selection means and the lighting is started, immediately after the lighting is started. 1. A high-pressure discharge lamp lighting device comprising: a control means for causing a lamp current to flow through the high-pressure discharge lamp for a short period of time equivalent to that during starting lighting in full light mode.