JPS63244594A - Discharge lamp lighter - 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] [Industrial Application Field] The present invention relates to a device for lighting a preheated discharge lamp such as a fluorescent lamp, and particularly to a device for lighting a preheated discharge lamp such as a fluorescent lamp. Can be lit with two dimming levels and
The present invention relates to a discharge lamp lighting device that preheats the discharge lamp without lighting it by setting the inverter to the same operating state as the predetermined dimming state at startup, thereby ensuring a long lamp life.

[Conventional technology] A preheating type discharge lamp (lamp) is discharged without being sufficiently preheated.
If you repeat the so-called cold start that causes the light to turn on,
The lamp becomes blackened and its lifespan is shortened. Therefore, DC power can be replaced with AC power (e.g. 20 to 10.0 k
Conventionally, devices for lighting such lamps with AC power converted into AC power (Hz) have been used to maintain the voltage applied to the lamp at a level lower than the discharge start voltage of the lamp for a predetermined period of time immediately after power is turned on. It has a so-called soft start function that preheats without turning on the light.

[Problems to be solved by the invention] By the way, in order to provide such a soft start function, conventionally, the terminals of both filaments of the lamp on the side not connected to the inverter transformer were short-circuited only during the preheating period. The winding for lamp current supply and the filament winding are wound independently in the inverter transformer, and the lamp current supply circuit is cut off during preheating.
As described in No. 956, the switching transistor of the constant current push-pull inverter is operated at A only during the preheating period.
Efforts have been made to reduce the voltage applied to the lamp by operating the lamp in parallel mode.

However, since the conventional lighting device is provided with a soft start circuit separately from the dimming circuit, the circuit configuration is complicated and the cost is high.

The purpose of the present invention is to solve the above-mentioned problems in the conventional type.
In a discharge lamp lighting device that modulates the lamp by varying the switching frequency and/or on/off duty in an inverter, we have added a soft start function to ensure lamp life with a simple circuit configuration and at low cost. be.

[Means for Solving the Problems] In order to achieve the above object, the present invention includes an inverter that generates an AC output from a DC power supply, and operates the inverter in two or more modes with different switching frequencies and/or on/off duties. BACKGROUND ART In a discharge lamp lighting device that lights a lamp at full brightness and dimmed by operating the device, at the time of starting, the inverter is set to the same operating state as when lighting is dimmed and the lamp is preheated.

[Operations and Effects] According to the above configuration, the lamp life can be ensured by the soft start function of keeping the voltage applied to the lamp low during preheating of the lamp. Furthermore, since the soft start circuit for this purpose only controls the dimming circuit with a timer, it can be realized with a simple circuit configuration and at low cost.

[Example] The present invention will be described in detail below using the drawings.

FIG. 1 shows a block circuit of a discharge lamp lighting device according to an embodiment of the present invention. The device in the figure includes a DC power supply circuit 1, an inverter circuit 2, a dimming switching circuit 3, an all-light starting circuit 4, a soft start circuit 5, a power supply voltage humidity compensation circuit 6, a no-load stop circuit 7, and a switching improvement circuit. 8.

The DC power supply circuit 1 includes a full-wave rectifier circuit DB and a smoothing capacitor C4, and generates a smoothed DC voltage from an AC power supply (not shown).

The inverter circuit 2 uses a quasi-E class automatic single transistor inverter circuit, and has an LC resonance circuit including an inductor L1 and a capacitor C1 and a current limiting ( A series circuit of an inductor L2 for the ballast (ballast) and a fluorescent lamp FL as a load is connected, and a feedback winding 2f provided on the inductor L2 is connected to one end of the transistor Trl via a series circuit of a capacitor C3 and an inductor L8. The other end is connected to the base and the other end is connected to the negative terminal of the DC power supply. In addition, a variable resistor VR is connected between the base of the transistor Tri and the negative side terminal of the DC power supply, and the transistor Tr
The emitter of i is connected to the negative terminal of the DC power supply via a diode D7. Furthermore, a lamp starting capacitor C2 is connected between the non-power supply side terminals r2 and f4 of each filament of the fluorescent lamp FL.

Next, the operation of the inverter circuit 2 will be explained. In FIG. 1, an AC power supply (not shown) is turned on, and a DC power supply circuit 1
When a DC voltage is generated, a base current is supplied to the transistor Tri via a starting resistor (not shown), and the collector current of the transistor Tri is connected to the parallel resonant circuit of the inductor Ll and the capacitor C1 and the series resonance circuit of the inductor L2 and the capacitor C2. flows through the circuit. This causes transistor Tri to have positive feedback from collector to base via inductor L2, feedback winding L2f, capacitor C3 and inductor L3, and Ll,
L2. Oscillation starts due to resonance of the collector circuit consisting of CI and C2.

In FIG. 1, capacitor C3 and inductor L3
is for drawing out the base current of the transistor Trl when it is turned off to reduce the switching loss of the transistor Tri. Variable resistance VR is transistor T
This is a capacitor reset resistor that discharges the charge charged in the capacitor when the transistor ri is on when the transistor Tri is off.

This inverter circuit 2 can vary the oscillation frequency of the inverter circuit 2 by varying the reset resistor VR. That is, referring to FIG. 2, during the on period Ton of the transistor Tri, the transistor Tr
The base current flows through capacitor C3, and the feedback winding L2f' side of capacitor C3 is +, and the transistor T
The base side of ri is charged in the negative direction. During the next OFF period Toff' of the transistor Trl, the charge in the capacitor C3 is transferred to the variable resistor VR and the inductor L by a voltage induced in the feedback winding L2f' in the opposite direction to that during the ON time.
3.

When the resistance value of variable resistor vR is increased, capacitor C3
The discharge (reset) time constant becomes longer.

Here, the off-period T of'f' of the transistor Tri
is determined by the resonance system connected to the collector of this transistor Tri, so it is almost constant. Therefore, the amount of charge discharged during the off period Toff of the transistor Trl, that is, the amount of charge that can be charged during the on period Ton, decreases. In other words, capacitor C3 is transistor T
When ri is on, when the base current of the transistor Tri flows, it is quickly charged, and the base current of the transistor Trl quickly decreases, and the transistor Trl is turned off due to the above-mentioned positive feedback. As a result, the on period Ton of the transistor Trl is shortened, and the oscillation frequency is increased.

In this device, the natural frequency of the collector load resonance system of the transistor Tri is set lower than the oscillation frequency of this inverter circuit 2, so if the oscillation frequency of the inverter circuit 2 is increased and moved away from the natural frequency, the lamp current will be reduced. On the other hand, if the oscillation frequency of the inverter circuit 2 is lowered to approach the natural frequency, the lamp current will increase.

Therefore, in this device, the resistance value of the variable resistor VR is set to a predetermined value to turn on the lamp FL at full brightness, and the resistance value of the variable resistor VR is varied or switched to a higher value to control the inverter circuit 2. The lamp FL can be dimmed and lit by increasing the oscillation frequency and decreasing the lamp current.

The dimming switching circuit 3 includes a dimming/all-lighting switch and the like, and is a circuit for setting the lighting state of the lamp FL in a steady state.

The soft start circuit 5 operates for a predetermined period of time immediately after the power is turned on.
This circuit operates the inverter circuit 2 in the same state as during dimming, keeps the voltage applied to the lamp FL lower than the discharge start voltage, and preheats the lamp FL without lighting it.

After fully preheating the lamp FL by the above-mentioned preheating, the full-light starting circuit 2 operates the inverter circuit 2 in the same state as in the full-light mode to apply a voltage sufficiently higher than the discharge starting voltage to the lamp FL, thereby starting the lamp FL. This is the circuit for lighting.

The power supply voltage/temperature compensation circuit 6 controls the resistance value of the variable resistor VR of the inverter circuit 2, that is, the oscillation frequency, and compensates for lamp power fluctuations due to power supply voltage fluctuations, and increases the lamp voltage at low temperatures to improve the starting characteristics and the lamp. Compensate for brightness.

The no-load stop circuit 7 is activated when the lamp FL is removed or
This circuit detects a no-load state such as a one-way discharge state and stops the operation of the inverter circuit 2.

The switching improvement circuit 8 is a circuit for further improving the switching characteristics of the transistor Tri of the inverter circuit 2.

Since the operations of these circuits 3 to 8 are common to the device shown in FIG. 3, they will be explained with reference to the more detailed circuit diagram shown in FIG.

FIG. 3 shows a circuit configuration of a discharge lamp lighting device according to a second embodiment of the present invention. This device consists of lamps FLI and FL2.
It is designed so that two strokes of and are lit in series.

Also, in place of the variable resistor VR in FIG.
A variable resistance circuit VR consisting of 8 etc. is used. The variable resistor VRI is used to adjust the operating point of the transistor Tr8.

The equivalent resistance value of this transistor Tr8 changes depending on the base current supplied from the voltage/temperature compensation circuit 6. In the device shown in FIG. 3, a zener diode Z is connected to the base of the transistor Tr8 in accordance with the operations of the soft start circuit 5, all-light starting circuit 4, and dimming switching circuit 3.
The lower voltage determined by the zener voltage of D (during dimming) and the higher voltage determined by the rectified output of diode D6 (
A current flows based on a voltage obtained by further compensating two types of voltages (at full light) and the power supply voltage and temperature.

Next, the operation of the apparatus shown in FIG. 3 will be explained.

In FIG. 3, the rotary switch SWl serves both as a power switch and a full-light/dimmer switch. When dimming, it is set to the position shown in the figure, and the AC power is supplied to the DC power supply circuit 1 and the dimming switch circuit 3. For example, 100v alternating current power from AC is supplied. During full light, AC power is supplied only to the DC power supply circuit 2.

When the low-return switch SWI is switched from the power-off state to the dimming state, the AC voltage from the AC power source AC is transmitted through a protection circuit consisting of a fuse F, a positive temperature coefficient thermistor PTH, etc., a varistor ZNR, a balanced transistor, etc. DC power supply circuit 1 via a noise prevention/surge absorption circuit
supplied to

The DC power supply circuit 1 rectifies this AC voltage with a full-wave rectifier circuit DB, smoothes it with a capacitor C4, and generates a DC voltage. This DC voltage is applied to the starting resistor R3 of the inverter circuit 2.
The signal is supplied to the base of the switching transistor Trl via the switching transistor Trl. As a result, the inverter circuit 2 starts oscillating, and an alternating current voltage Vel (FIG. 2) is generated at the collector of the transistor Tr1. In the autotransformer T2, the winding L1 forms a parallel resonant circuit with the capacitor C6, and the AC voltage Vcl is stepped up and connected via the inductor L2, which is the primary winding of the transformer T3, to the lamp consisting of the capacitor C2, lamps FLI and FL2. Apply to the circuit.

Here, since the lamps FLI and FL2 are not yet lit and are in an open state, the Q of the resonance system connected to the collector of this transistor Trl is high.

Therefore, a larger current flows through the paths of the inductors LL and L2, the capacitor C2, and the fluorescent lamps Fl and F2 than when the lights are turned on due to the resonance of the inductor L2 and capacitor C2, thereby preheating the fluorescent lamps Fl and F2. . At this time, a higher voltage is generated at both ends of the capacitor C2, and therefore at both ends of the series circuit of the fluorescent lamps Fl and F2 than when the fluorescent lamps Fl and F2 are turned on due to the above-mentioned resonance. If the voltage is higher than the starting voltage, the fluorescent lamps Fl and F2 will immediately turn on (cold start) without being preheated after the power is turned on. In order to prevent such a cold start, a soft start circuit 5, which will be described later, is provided.

Further, the AC voltage induced in the secondary winding of the transformer T3 is rectified and smoothed by the diode D6 and the capacitor C17, and is supplied to the circuits 3 to 7.

In the soft start circuit 5, as explained below with reference to the time chart of FIG. 4, when the power is turned on, the terminal voltage of the capacitor C13 of the all-optical start circuit 4 is zero and the transistor Tr5 is turned off. Transistor Tr
8 is on. Therefore, from this soft start circuit 5, the same voltage as during dimming, which is the zener voltage of the zener diode ZD, is applied via the power supply voltage/temperature compensation circuit 7 to the base of the transistor Tr8 of the variable resistance circuit VR. As a result, the equivalent resistance of the transistor Tr8 becomes the same higher resistance value as during dimming, and the oscillation frequency of the inverter circuit 2 is higher than that during all-optical mode operation, resulting in a current flowing through the resonant circuit and a voltage generated across the capacitor C2. operates in a lower dimming mode than when operating in full light mode.

These currents and voltages in the dimming mode can be set by selecting the value of the capacitor C2 with almost no effect on the lighting characteristics. Here, the voltage generated across the capacitor C2 when the lamps Fl and F2 are off is lower than the voltage that causes the lamps FL and F2 to start discharging when the inverter circuit 2 is operated in the dimming mode, and the inverter circuit 2 is operated in the full-light mode. When the lamp Fl, F2
The voltage is set to be higher than the voltage that starts the discharge.

In the all-optical starting circuit 4, capacitor C13 is connected to resistor R9.
is charged via. After the power is turned on, the terminal voltage of the capacitor 013 rises, and this terminal voltage is transferred to the resistor R12.
When the transistor Tr5 is turned on by the voltage divided by and R13 (time tl in FIG. 4), the soft start circuit 5
The transistor Tr8 of the variable resistance circuit VR is turned off, and the base current of the transistor Tr8 of the variable resistance circuit VR is switched to the larger one, so that the inverter circuit 2 enters the all-optical mode. This causes the lamp Fl.

A voltage higher than the discharge starting voltage is applied to F2, and lamps Fl and F2 start discharging and turn on. After lighting, the lamps Fl and F2 connected in parallel to the starting capacitor C2
Since the impedance becomes low, the Q of the load resonance system decreases, and the current of the lamps Fl and F2 is limited by the inductor L2, so that the lamps are lit stably.

In the dimming switching circuit 3, an AC voltage input through the rotary switch SWI set to the dimming state is rectified and smoothed by the diode DI and the capacitor C12, and then supplied to the base of the transistor Tr2. As a result, the transistor Tr2 is turned on and the transistor Tr3 is turned off.

In this state, in the above-mentioned original circuit 4, the capacitor C
13 is further charged through the resistor R9 and its terminal voltage rises. When the voltage obtained by dividing this terminal voltage by the resistors RIG and R11 turns on the transistor Tr4 (time t2 in FIG. 4), the transistor Tr5 turns on. Then, the transistor Tr8 of the soft start circuit 5 is turned on, and the base current of the transistor Tr8 of the variable resistance circuit VR is switched to the smaller one, and the inverter circuit 2 enters the dimming mode. As a result, the lamps Fl and F2 are lit in a dimmed state from now on.

On the other hand, when the low-return switch SWI is set to the full-light lighting position, no AC voltage is supplied to the dimming switching circuit 3, and the transistor Tr2 is turned off. Therefore, transistor Tr8 is on, transistor Tr4 is off,
The transistor Tr5 is turned on and the transistor Tr8 is turned off, and the larger current flows through the base of the transistor Tr8 of the variable resistance circuit VR, and the equivalent resistance value of the transistor Tr8 becomes the lower one, so the inverter circuit 2 enters the all-optical mode. . As a result, the lamps Fl and F2 are fully lit.

In FIG. 4, the solid line shows the operation of each part when the low light switch SWI is set to the dimming state, and the broken line shows the operation of each part when the low light switch SWI is set to the full light state.

As can be seen from the above, in this device, the capacitor C1l and the resistor R9 are connected to the soft start circuit 5.
It also serves as a timer circuit for both the full-light lighting circuit 4 and the full-light lighting circuit 4.

In the power supply voltage/temperature compensation circuit 6, a voltage obtained by dividing the DC power supply voltage by a resistor R1 and a thermistor ER2 is applied to the base of the transistor Tr7. Therefore, when the power supply voltage increases, the base voltage of the transistor Tr7 increases, the collector current of the transistor Tr7, that is, the base current of the transistor Tr8 decreases, the equivalent resistance value of the transistor Tr8 increases, and the oscillation frequency of the inverter circuit 2 increases. and the lamp current decreases. On the other hand, the power supply voltage decreases. Then, contrary to the above, the lamp current increases. Thereby, the lamp current can be stabilized against fluctuations in the power supply voltage.

Also, as the temperature decreases, thermistors ERI and ER
2 resistance value decreases. Then, the emitter voltage of the transistor Tr7 increases due to the decrease in the resistance value of the thermistor ERI, and the base voltage of the transistor Tr7 decreases due to the decrease in the resistance value of the thermistor ER2. Therefore, the collector current of the transistor Tr7, that is, the base current of the transistor Tr8 increases, the equivalent resistance value of the transistor Tr8 decreases, the oscillation frequency of the inverter circuit 2 decreases, and the lamp voltage at the time of starting and the lamp current at the time of lighting decrease. To increase. Thereby, starting performance at low temperatures and light output at low temperature lighting can be ensured.

In the device shown in FIG. 3, when the lamps Fl and F2 are off, that is, when there is no load, a resonant current from the inductor L2, capacitor 02, etc. flows through the transistor Trl. Since this resonant current is larger than when the lamp is lit, if this state continues, stress will accumulate in the transistor Trl, or in the worst case, the transistor Tri will undergo thermal runaway and be destroyed.

The no-load stop circuit 7 is provided to prevent this.

When there is no load, a larger current flows through the inductor L2 than when there is a load. Therefore, the voltage induced in the secondary winding L2s of the transformer T3 is also larger when there is no load. In the no-load stop circuit 7, when there is no load, the rectified output of the diode D6 increases, and when this state continues for a predetermined period of time, the capacitor C14 is charged via resistors R17, R18, etc., and its terminal voltage increases. . Then, when this terminal voltage becomes higher than the on-voltage of constant voltage element SB5, SB5 is turned on. As a result, the thyristor SCR is turned on, the transistor Tr9 is turned on, and the transistor Tri is turned off.
Inverter circuit 2 stops oscillating. This stopped state is
It continues until the power is turned off and then turned on again.

FIG. 5 shows a circuit configuration of a discharge lamp lighting device according to a third embodiment of the present invention. The device shown in the figure is an IC version of the dimming switching circuit 3, full-light lighting circuit 4, soft start circuit 5, and no-load stop circuit 7 of the device shown in FIG. 3, except for the time constant circuit portion. In the apparatus shown in FIG. 5, a time constant for soft start and a time constant for full-light lighting are provided separately.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a discharge lamp lighting device according to an embodiment of the present invention, FIG. 2 is a waveform diagram of each part of the inverter circuit in FIG. 1, and FIG. 3 is a circuit diagram of a discharge lamp lighting device according to another embodiment of the present invention. A circuit diagram of such a discharge lamp lighting device, FIG. 4 is a timing chart for explaining the operation of each part of the device of FIG. 3, and FIG. 5 is a discharge lamp lighting device according to still another embodiment of the present invention. FIG. 1: DC power supply circuit, 2: Inverter circuit, 3: Dimming switching circuit, 4: All-light lighting circuit, 5: Soft start circuit.

Claims (1)

[Claims] 1. An inverter that is equipped with a switching element and generates an AC output from a DC power source, a preheating discharge lamp that is lit by being supplied with this AC output, and an on/off duty and/or of the switching element. Dimming control that varies the frequency and sets the inverter to at least two operating modes: a first mode in which the discharge lamp is lit at full brightness, and a second mode in which the discharge lamp is lit in a predetermined dimming state. In the discharge lamp lighting device, when starting, the inverter is first operated in the second mode to preheat the discharge lamp without discharging the discharge lamp, and then operated in the first mode to warm the discharge lamp. A discharge lamp lighting device characterized in that it is provided with a timer control means for lighting the discharge lamp at full brightness or dimming by starting discharge at a time and then operating in an operation mode set by the dimming control means. .