JPH06203990A - Fluorescent lamp dimmer system - Google Patents

Abstract

PURPOSE:To easily regulate luminance by connecting the secondary winding of a current transformer between across terminals on electrodes of a fluorescent lamp and a capacitor across the terminals of the other-side to change the frequency of a high frequency constant current to the primary winding of the transformer. CONSTITUTION:The current to the secondary winding 4 of a current transformer 3 after lighting a fluorescent lamp 5 is the sum of the discharge current of the fluorescent lamp 5 and the current carried to a capacitor C, and its effective value is kept at a fixed value determined depending on the winding ratio of the transformer 3. The phases of both currents are shifted by 90 deg., and the voltage on across the capacitor C is equal to the discharge voltage of the fluorescent lamp, and regularly kept constant. When the frequency of the current is increased, thus, the current to the capacitor C is increased, and the discharge current of the fluorescent lamp 5 is reduced, resulting in a reduction in its luminance. Namely, the luminance of the fluorescent lamp can be regulated with simple mechanism and operation without changing the current value of the power source current.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluorescent lamp dimming system in a high frequency constant current power supply for supplying electric power to a fluorescent lamp by using a current transformer.

[0002]

2. Description of the Related Art The present applicant has developed a connectionless discharge tube lighting device in which a high frequency constant current power source is used to supply power to a fluorescent lamp using a current transformer, and has already been registered as a utility model ( See Japanese Utility Model Publication No. 64-5360). An outline thereof will be described with reference to FIG. 4. A single power supply line 12 connected to a high frequency constant current power supply 11 is allowed to pass a current transformer 13 and its secondary winding 14 is directly connected to both terminals of a fluorescent lamp 15. Since the current does not flow in the secondary winding 14 before the fluorescent lamp 15 starts discharging, the iron core of the current transformer 13 is saturated, and thus the discharge starting voltage of the fluorescent lamp 15 in the secondary winding 14 is increased. A higher voltage appears, and after the fluorescent lamp 15 starts to discharge due to this voltage, a constant current according to the number of turns of the secondary winding 14 flows.

After the light is turned on and the discharge is stabilized, the power supply line 12
Since the discharge current of the fluorescent lamp 15 can be increased / decreased by increasing / decreasing the value of the current flowing in the fluorescent lamp 15, the brightness of the fluorescent lamp 15 can be easily and surely adjusted, but the current of a relatively large value (load (The current value increases as the number increases)
In order to increase / decrease, the inverter used as a power source is required to have a large rated current adjusting function, resulting in a large size.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a high frequency constant current power supply system capable of adjusting the brightness of a fluorescent lamp by an extremely simple means without changing the value of the power supply current. It is to provide a dimming method.

[0005]

In order to solve the above-mentioned problems, a fluorescent lamp dimming system of the present invention applies a high frequency constant current to the primary winding of a current transformer and causes both terminals of the secondary winding to be fluorescent. The brightness of the fluorescent lamp is adjusted by connecting to one terminal of each electrode of the lamp and connecting a capacitor between the other terminals of both electrodes to change the frequency of the high frequency constant current flowing in the primary winding. I am trying.
The brightness of the fluorescent lamp is adjusted by changing the capacity of the condenser.

[0006]

[Function] The current flowing through the secondary winding of the current transformer after the fluorescent lamp is turned on is the sum of the discharge current of the fluorescent lamp and the current flowing through the capacitor, and its effective value is a constant determined by the winding ratio of the current transformer. It is kept at the value. The discharge current of the fluorescent lamp and the current flowing through the condenser are 90 degrees out of phase, and the voltage across the condenser is always equal to the discharge voltage of the fluorescent lamp and is always kept constant. The flowing current increases, the discharge current of the fluorescent lamp decreases, and its brightness decreases. Also, as the capacity of the condenser is increased, the current flowing therethrough is increased, so that the discharge current of the fluorescent lamp is also reduced and the brightness thereof is also reduced.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram of the whole, and FIG. 2 is an operation explanatory diagram thereof. A power supply line 2 which is connected to the output terminal of the inverter 1 and through which a high frequency constant current flows passes through an annular current transformer 3 (that is, is wound as a primary winding of one turn). A secondary winding 4 is wound around the current transformer 3 for N turns, and both terminals thereof are connected to one terminal of each of the two electrodes 6 and 7 of the fluorescent lamp 5. Further, a capacitor C is connected between the other terminals of the electrodes 6 and 7, respectively. The inverter 1 can continuously change the frequency of the high frequency constant current flowing through the power supply line 2.

When the fluorescent lamp 5 is turned on and the discharge is stabilized, the voltage between the electrodes 6 and 7 (that is, the terminal voltage of the capacitor C) is kept substantially constant at the unique discharge voltage, and the discharge current Id and the capacitor are maintained. As shown in FIG. 2, the current Ic flowing through C is 90 degrees out of phase with each other, and the vector sum thereof is equal to the current I flowing through the secondary winding 4 of the current transformer 3. The current I flowing through the secondary winding 4 of the current transformer 3 is 1 / N of the high frequency constant current flowing through the power supply line 2.

Now, when the frequency of the high frequency constant current is f ₁ , a current Ic ₁ which is determined by the discharge voltage of the fluorescent lamp 5 flows through the capacitor C and a current I flowing through the secondary winding 4.
Has the phase shown in the figure, and Id ₁ =
A discharge current of √ (I ² −Ic ₁ ² ) flows. When the frequency changes to f ₂ (> f ₁ ) here, the current flowing through the capacitor C increases by f ₂ / f ₁ times to Ic ₂ , so the phase of the current I changes as shown in the same figure. Then, the discharge current decreases to Id ₂ = √ (I ² −Ic ₂ ² ) and the brightness of the fluorescent lamp 5 also decreases accordingly. If a plurality of fluorescent lamp loads are connected to the power supply line 2, all fluorescent lamps can be dimmed simultaneously by this method.

FIG. 3 shows a second embodiment of the present invention. The difference from the first embodiment is that instead of the capacitor C connected between the electrodes 6 and 7, a plurality of capacitors C ₁ , C ₂ and C ₃ that can be switched by a switch S are provided, and the frequency of the high frequency constant current is changed. F ₁
The point is that these capacitors are switched instead of being changed from the above, and other configurations are exactly the same as in the first embodiment.

The dimming operation will be described with reference to FIG. Now, the frequency of the high frequency constant current is f ₁ and the switch S
Is switched to the capacitor C ₁ , and a current I flows through the secondary winding 4 and a current Ic ₁ flows through the capacitor C ₁ , the current I has the phase shown in FIG. Discharge current of Id ₁ = √ (I ² −Ic ₁ ² ) flows. Next, when the switch S is switched to the capacitor C ₂ without changing the frequency from f ₁ , the capacitor C ₂ has Ic ₂ (where C ₁ / C ₂ = f ₁ / f ₂ is assumed to be Ic ₂ = Current Ic ₁ × f ₂ / f ₁ ) flows, the phase of the current I changes as shown in the figure, and the discharge current Id ₂
= √ (I ² −Ic ₂ ² ) and the brightness of the fluorescent lamp 5 decreases. According to this method, it is possible to individually dimmer a plurality of fluorescent lamps connected to the power supply line 2, and it is possible to continuously dimmer by using a variable capacitor as a capacitor.

If the methods of the first and second embodiments are used together, the dimming of the entire fluorescent lamps and the dimming of the individual fluorescent lamps can be appropriately combined as needed. The frequency and current value of the high-frequency constant current flowing through the power supply line, the winding ratio of the current transformer, the rating and number of fluorescent lamps, the capacity of the condenser, and the like can be changed as appropriate.

[0013]

As described above, the fluorescent lamp dimming method of the present invention is a high frequency constant current power supply method, and discharges the fluorescent lamp by an extremely simple mechanism and operation without changing the current value of the power supply current. This has an effect that the brightness can be adjusted by changing the current.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of its operation.

FIG. 3 is a schematic diagram of a second embodiment of the present invention.

FIG. 4 is a schematic view of a conventional device.

[Explanation of symbols]

1 Inverter 2 Feed line 3 Current transformer 4 Heating wire 5 Fluorescent lamp 6, 7
Electrode C Condenser S switch

Claims (2)

[Claims] 1. A high-frequency constant current is passed through the primary winding of a current transformer, and both terminals of the secondary winding are connected to one terminal of each electrode of a fluorescent lamp and between the other terminals of both electrodes. A fluorescent lamp dimming system characterized in that the brightness of the fluorescent lamp is adjusted by connecting a capacitor and changing the frequency of a high frequency constant current flowing through the primary winding. 2. A high frequency constant current is applied to the primary winding of a current transformer and both terminals of the secondary winding are connected to one terminal of each electrode of a fluorescent lamp and between the other terminals of both electrodes. A fluorescent light dimming method, wherein a brightness is adjusted by connecting a condenser and changing the capacity of the condenser.