JPH02288194A - Discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To make preheating of the electrode of a fluorescent lamp sufficiently and prevent premature blackening of parts near the electrode and severance of the same by supplying DC current to a current transformer for a certain while from the time when the power is put on. CONSTITUTION:When the power is put on, DC current flows through the secondary winding 130b of a current transformer 130 under a certain period when a timer circuit 150 is in operation, and electrodes 118a, 118b are preheated while discharge of a discharge lamp 118 is suppressed by lowering the voltage generated at the ends of a starter capacitor 132. After passage of the preheating time the DC current flowing through the mentioned secondary winding 130b is shut, and the voltage at the end of starter capacitor 132 will rise to start discharging from the discharge lamp 118. Thereby the electrodes 118a, 118b are preheated sufficiently to preclude them from premature blackening or severance.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a discharge lamp lighting device, and particularly to improvements in its inverter circuit.

[Prior Art] In recent years, discharge lamp lighting devices have been developed that use inverter circuits to light discharge lamps such as fluorescent lamps at high frequencies. Flicker-free light output can be obtained.

Conventionally, as such a discharge lamp lighting device, one equipped with a single stone exciter type inverter circuit as shown in FIG. 4 is known.

The discharge lamp lighting device shown in the figure converts AC voltage from an AC power supply 10 into DC voltage using a full-wave rectifier 12 and a smoothing capacitor 14, supplies it to an inverter circuit 16, converts it into high-frequency current, and lights a fluorescent lamp 18. It is something that makes you

The inverter circuit 16 includes a parallel resonant circuit 24 made up of an oscillation choke 20 and a resonant capacitor 22, and a switching transistor 26 that turns the parallel resonant circuit 24 into a 0N10FF state, which are connected in series.

Further, one electrode 18a of a fluorescent lamp 18, which is a load, is connected to the full-wave rectifier 12 via a ballast choke 28, and the other electrode 18b is connected to the primary winding 3 of a current transformer 30.
It is connected to the contact point between the parallel resonant circuit 24 and the collector of the switching transistor 26 via 0a.

Further, a starting capacitor 32 is connected to the non-power side of the fluorescent lamp 18.

On the other hand, one end of the secondary winding 30b of the current transformer 30 is connected to the base of the switching transistor 26, and the other end is connected to the switching transistor 2 through a capacitor 34.
6 emitters.

A series circuit of a resistor 36 and a diode 38 is connected between the base and emitter of the switching transistor 26, and the resistor 40 serves as a starting resistance for the switching transistor 26.
connected to the base of.

The discharge lamp lighting device according to the illustrated example is roughly configured as described above, and its operation will be explained next.

First, when the AC power supply 10 is turned on, the full-wave rectifier 12,
A DC voltage that is rectified and smoothed by the smoothing capacitor 14 is generated. This DC voltage supplies a slight base current to the switching transistor 26 via the starting resistor 40, and the switching transistor 26 is turned on.

Therefore, the parallel resonant circuit 24 and the ballast choke 28
, the electrode 18a1 of the fluorescent lamp, the starting capacitor 32, the electrode 18b1 of the fluorescent lamp, the primary winding 30a of the current transformer 3o, and a current flows through the secondary winding 30b of the current transformer 30 with positive feedback to the switching transistor 26. A current flows and the capacitor 34 is charged so that

As a result, the base current of the switching transistor 26 increases, and the collector current also increases accordingly.

Here, since the base current of the switching transistor 26 is an oscillating current, the base current flows in the opposite direction after a certain period of time, and when the accumulated charge in the switching transistor 26 is exhausted, the switching transistor 26 is turned off. Therefore, the electromagnetic energy accumulated in the oscillation choke 20 causes the oscillation choke 20 and the resonant capacitor 22 to
It resonates with and generates a resonant voltage. This resonant voltage causes
The current limited by the ballast choke 28 flows through the fluorescent lamp 18.
electrode 18a1 of fluorescent lamp 18 starts capacitor 32, electrode 18b1 of fluorescent lamp 18 flows through primary winding 30a of current transformer 30.

Further, a current flows through the secondary winding 30b of the current transformer 30 in a direction that provides a reverse bias to the base of the switching transistor 26. After a certain period of time, the switching transistor 2 is connected to the secondary winding 30b of the current transformer 30 again.
A current flows in the direction in which inverter 6 turns on, and inverter circuit 16 maintains oscillation.

Furthermore, since the starting capacitor 32 resonates with the ballast choke 28 and its impedance becomes small, current flows through the electrodes 18a and 18b of the fluorescent lamp 18, and at the same time, a resonant voltage is generated across both ends of the starting capacitor 32. The fluorescent lamp 18 is turned on. After lighting, the current limited by the ballast choke 28 flows to the fluorescent lamp 18 and performs high frequency lighting.

[Problems to be Solved by the Invention] However, in the discharge lamp lighting device as described above, the electrodes 18a and 18b of the fluorescent lamp 18 are turned on before they are sufficiently preheated, resulting in blackening near the electrodes and disconnection of the electrodes. There were issues such as problems such as problems appearing early.

That is, if the LC condition of the inverter circuit 16 is set to a condition that allows the fluorescent lamp 18 to be turned on and maintained, a high voltage will be generated across the starting capacitor 32 at the same time as the AC power supply 10 is turned on, and the fluorescent lamp 18 will be turned on immediately. This causes the light to turn on.

On the other hand, if the LC resonance conditions of the inverter circuit 16 are set to such a condition that the fluorescent lamp 18 is not turned on and the electrodes 18a and 18b can be sufficiently preheated, the electrodes 18a and 18b are only preheated, and the fluorescent lamp 18 is A problem arises in that discharge cannot be started.

The present invention has been made in view of the problems of the prior art described above, and its purpose is to provide a discharge lamp lighting device that can sufficiently preheat the electrodes of a discharge lamp when the power is turned on, and can discharge the discharge lamp appropriately. It's about doing.

[Means for Solving the Problems] In order to achieve the above object, a discharge lamp lighting device according to the present invention includes a timer circuit that sets a desired preheating time from when the power is turned on, and a timer circuit that is in the preheating period. a preheating circuit that passes a DC current through a secondary winding of the current transformer and interrupts the DC current flowing through the secondary winding of the current transformer when the timer circuit passes a preheating period. It is characterized by

Preferably, the preheating circuit includes a switch that conducts electricity to the timer circuit, and a DC power source that can flow a DC current to the secondary winding of the current transformer via the switch.

Further, the DC power source of the preheating circuit may be a voltage obtained by rectifying and smoothing a voltage generated in a secondary winding wound around an oscillation choke or a ballast choke.

[Function] Since the discharge lamp lighting device according to the present invention has the above-described means, when the power is turned on, a DC current flows through the secondary winding of the current transformer for a certain period of time while the timer circuit is operating, and flows across the starting capacitor. Preheating the electrodes while suppressing the discharge of the discharge lamp by lowering the voltage generated. After the preheating time has elapsed,
Since the DC current flowing to the secondary winding of the current transformer is cut off, the LC resonance condition of the inverter circuit becomes a condition for lighting the discharge lamp, and the voltage at the starting capacitor becomes high and the discharge of the discharge lamp is started. Ru.

Therefore, discharge is started after the electrodes of the discharge lamp have been sufficiently preheated, so that early blackening of the electrodes and disconnection of the electrodes can be prevented, and good starting and lighting can be maintained.

[Embodiments] Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

FIG. 1 shows a circuit configuration of a discharge lamp lighting device according to a first embodiment of the present invention, and portions corresponding to those in FIG.

A characteristic feature of the present invention is that a timer circuit and a preheating circuit are provided in order to take sufficient time to preheat the electrodes of the discharge lamp.For this reason, in this embodiment, a timer circuit 150 and a preheating circuit 152 are provided. It is equipped with

Here, the preheating circuit 152 includes a series circuit consisting of a DC power supply 154, a resistor 156 that limits the DC current of the DC power supply 154, a normally closed switch 158, and a diode 160, and a series circuit that includes a capacitor 134 and a current transformer 130. It is connected between the secondary winding 130b and the secondary winding 130b.

The timer circuit 150 is configured to operate at a certain time after the AC power source 110 is turned on, and turn off the switch 158.

The discharge lamp lighting device according to this embodiment is roughly constructed as described above, and its operation will be explained next.

First, when the AC power source 110 is plugged in, the first-stone excited inverter circuit 116 is activated and starts oscillating by the same operation as in the conventional example.

Here, when the AC power supply 110 is turned on, the switch 158 is closed, and the DC power supply 154 connects the resistor 156 to the switch 1.
58 , the diode 160 , the secondary winding 130 b of the current transformer 130 , and the DC power supply 154 .

Then, by passing a DC current through the secondary winding 130b of the current transformer 130, a DC magnetic flux is generated, so that the apparent saturation magnetic flux density of the current transformer 130 becomes smaller. Therefore, the oscillation frequency of switching transistor 126 is higher than when switch 158 is off.

Due to this high oscillation frequency, the voltage developed across the starting capacitor 132 is so low that the fluorescent lamp 118 cannot be lit, but its electrodes 118a, 118b are sufficiently preheated.

Here, after the timer circuit 150 turns on the AC power supply 110,
It is set to turn off the Sui-Sochi 158 after a certain period of time has elapsed. Then, during this preheating time, the fluorescent lamp 118
If the time is set so that the electrodes 118a and 118b are sufficiently preheated, the switch 15 can be turned off after the electrodes have been sufficiently preheated.
8 is turned off, and the direct current flowing to the current transformer 130 is cut off.

As a result, the apparent saturation magnetic flux density of the current transformer 130 also returns to its conventional value.

Therefore, the oscillation frequency of the switching transistor 126 becomes lower than when the electrodes of the fluorescent lamp 118 are preheated, and at the same time, the terminal voltage of the starting capacitor 132 becomes high, so that the fluorescent lamp 118 starts discharging.

Furthermore, since the switch 158 remains open after lighting, the fluorescent lamp 118 remains lit in the same way as in the conventional case.

As described above, according to the discharge lamp lighting device according to the present embodiment, the electrodes 118a and 118b of the fluorescent lamp 118 are sufficiently preheated during the preheating time set in the timer circuit 150 and are then turned on. Blackening of the vicinity and early disconnection of the electrode can be prevented.

FIG. 2 shows a discharge lamp lighting device according to a second embodiment of the present invention, and parts corresponding to those in the first embodiment are designated by the reference numeral 100 and will not be described again.

What is distinctive about this embodiment is that instead of providing a separate DC power supply 154 as in the first embodiment, the alternating current from an AC power supply 210 is rectified and smoothed to provide a DC power supply.

That is, in this embodiment, the timer circuit 250 includes voltage dividing resistors 272 and 274, a capacitor 276 whose one end is connected between the resistors 272 and 274, and the capacitor 276.
A constant voltage diode 277 and a resistor 2 connected in series with
It consists of 78 pieces. As the accumulated charge in the capacitor 276 increases, its terminal voltage increases, and when it reaches the Zener voltage of the voltage regulator diode 277, it is configured to output a DC current cutoff signal to the preheating circuit 252. .

On the other hand, preheating circuit 252 includes a secondary winding 228a wound around ballast choke 228, and a diode 280 and a capacitor 282 that rectify and smooth the current induced in secondary winding 228a.

Further, the switch is composed of two transistors 284 and 286 and two resistors 288 and 290.

Then, when the AC power supply 210 is turned on, the inverter circuit 216 starts oscillating as in the first embodiment, a voltage is induced in the secondary winding 228a of the ballast choke 228, and the capacitor 282 is immediately charged with the DC current. It becomes a power source.

Then, the base current is supplied to the transistor 284 through the resistor 290, so that the transistor 284 is turned on, and the current limited by the resistor 288 flows from the capacitor 282 to the secondary winding 230b of the current transformer 230. As a result, the oscillation frequency of the switching transistor 226 increases, and the electrodes 218a and 218b of the fluorescent lamp 218 are preheated.

On the other hand, when the AC power supply 210 is turned on, the timer circuit 25
0 is also charged, and when it exceeds the Zener voltage of the constant voltage diode 277, the transistor 286 turns on, and the transistor 284 turns off.
state.

As a result, the direct current flowing through the secondary winding 230b of the current transformer 230 via the resistor 288 is cut off, and the oscillation frequency of the switching transistor 226 becomes lower. Then, the terminal voltage of the starting capacitor 232 becomes high and the fluorescent lamp 218 starts lighting.

As described above, according to the discharge lamp lighting device according to the second embodiment, there is no need to provide a separate DC power source.

FIG. 3 shows a third embodiment of the present invention, and parts corresponding to those in FIG. 2 are designated by the reference numeral 100 and will not be described.

The characteristic feature of this embodiment is that the DC power source is not taken from the ballast choke 328 but from the oscillation choke 328.
It was decided to take it from the secondary winding 320a wound around.

In each of the above embodiments, an example has been described in which a discharge lamp is lit using a DC voltage obtained by rectifying and smoothing an AC power source with an aftereffect rectifier, but it is also possible to use a normal DC power source.

[Effects of the Invention] As explained above, according to the discharge lamp lighting device according to the present invention, since the DC current is passed through the current transformer for a certain period of time from when the power is turned on, the electrodes of the fluorescent lamp are sufficiently preheated. This makes it possible to prevent early blackening near the electrodes, disconnection of the electrodes, etc.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a discharge lamp lighting device according to a first embodiment of the present invention, FIG. 2 is a circuit diagram of a discharge lamp lighting device according to a second embodiment of the present invention, and FIG. 3 is a circuit diagram of a discharge lamp lighting device according to a second embodiment of the present invention. FIG. 4 is a circuit diagram of a conventional discharge lamp lighting device. 10.110,210,310... AC power supply 12.1
12,212,312...Full wave rectifier 16.116,
216,316...Inverter circuit 18.118,218,318...Fluorescent lamp (discharge lamp) 24.124,224,324...Parallel resonant circuit 26
．． 126,226,326...Switching transistor (switching element) 28.128,228,328...Ballast choke 30.130,230,330...Current transformer 32.
132,232,332...Starting capacitor

Claims (3)

[Claims] (1) a rectifier circuit that rectifies alternating current from an alternating current power source and outputs a direct voltage; a parallel resonant circuit connected to the rectifier circuit and consisting of a resonant choke and a resonant capacitor; and a parallel resonant circuit connected in series to the parallel resonant circuit. a switching element; a lighting circuit in which a series circuit of a ballast choke, a discharge lamp, and a current transformer is connected to the parallel resonant circuit, and a starting capacitor is connected to the non-power supply side of the discharge lamp; A discharge lamp lighting device comprising a single-stone self-excited inverter that drives the switching element by a secondary winding of the device, comprising: a timer circuit that sets a desired preheating time from when the power is turned on; and a timer circuit that controls current while the timer circuit is in the preheating period. A preheating circuit that flows a DC current through a secondary winding of the transformer and interrupts the DC current flowing through the secondary winding of the current transformer when the timer circuit has elapsed a preheating period. Discharge lamp lighting device. (2) The device according to claim 1, wherein the preheating circuit comprises: a switch interlocked with a timer circuit; and a DC power supply capable of flowing a DC current to a secondary winding of a current transformer via the switch. A discharge lamp lighting device characterized by: (3) The device according to claim 1 or 2, wherein the DC power source of the preheating circuit is a voltage generated by rectifying and smoothing a voltage generated in a secondary winding wound around an oscillation choke or a ballast choke. Discharge lamp lighting device.