JPS61250998A - Fluorescent lamp lighting circuit - 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 invention] The present invention relates to a lighting circuit for a fluorescent lamp.

[Technical background of the invention and its problems]

Conventionally, there is a lighting circuit for a fluorescent lamp which increases the lighting frequency of a fluorescent lamp using a high-frequency AC power source using a high-frequency inverter circuit, increases the luminous efficiency of the fluorescent lamp, and is miniaturized. Such a lighting circuit is shown in FIG. - In FIG. 6, DC power from an input DC power source E is converted into an AC voltage of a predetermined frequency in an inverter circuit INV, and is applied to a primary winding Np of a transformer T. transformer T
Three windings N , N , and N are wound on the secondary side of. Winding Nl2 and S HI H
2 and N112 are the heater electrodes H of the fluorescent lamp FL, respectively.
This is a heater winding that supplies power to 1 and 1-12. The first and second heater circuits each include a closed circuit of the heater winding N111 and the heater electrode H1, and a closed circuit of the heater winding N□2 and the heater electrode H2, each of which has a heater voltage adjusting resistor R1. °R2 is inserted.

The winding N8 is a lamp current winding that drives the fluorescent lamp FL, and one end of this winding N8 is connected to the stabilizing capacitor C1.
The other end of this winding NS is connected to the other end of the switch S. Also, the connection midpoint A between the capacitor C1 and the switch S is connected to the first heater circuit, and the winding 1i! A connection midpoint B between the current outflow side terminal of N8 and the switch S is connected to the second heater circuit.

In such a lighting circuit, when the switch S is closed, the lamp current winding N8 is connected to the winding N8 → the capacitor C.
Only a reactive current flows in the path 1→switch S→winding NS, and the electromotive force of the winding NS is not applied between both heater electrodes H1 and 82, so the fluorescent lamp FL does not discharge and is not lit. However, at this time, heaters H1 and R
2 is a heater based on the electromotive force of the heater winding NN]1
1.R2 A current flows and it becomes preheated.

When the switch S is opened from this preheating state, the electromotive force of the lamp current winding N5 is applied between both heater electrodes H1 and 82 via the stabilizing capacitor C1, and discharge occurs and the lamp current flows to the fluorescent lamp FL. lights up immediately. When the lamp current flows, the voltage drops across the stabilizing capacitor C1,
Keeps the lamp current to a constant value.

By turning the switch S on and off in this manner, the light can be turned on and off as required.

However, in such a lighting circuit, the electromotive force of the heater winding N or NR2 may be extremely small compared to the electromotive force of the lamp current winding NS, and therefore, in practice, the number of turns of the heater windings NH1 and NH2 is 1-2
It becomes about the size of a tan. If the optimal number of turns is not an integer but, for example, 1.5 turns, the number of turns is larger than 2.
There was a problem in that the electromotive force became too large when the wire was wound around the winding. For this reason, the voltage larger than the optimum value was lowered by increasing the resistance values of the heater voltage adjustment resistors R1 and R2, but in this case, the resistance R1゜R
There is a problem that power loss occurs due to 2.

[Purpose of the invention]

The present invention has been made in consideration of the above circumstances, and it is an object of the present invention to provide a lighting circuit for a fluorescent lamp that can select a heater voltage to an appropriate value without causing extra power loss.

[Summary of the invention]

In order to achieve the above object, a lighting circuit for a fluorescent lamp according to the present invention includes an inverter circuit that converts a DC voltage into an AC voltage, and a transformer to which the output AC voltage from the inverter circuit is applied to a primary winding. , a lamp current winding that is provided on the secondary side of the transformer and supplies lamp current to the fluorescent lamp; a switch that controls on/off the supply of the lamp current to the fluorescent lamp; The present invention is characterized by comprising a heater winding provided on the secondary side and supplying a heater current to the heater electrode of the fluorescent lamp, and a capacitor connected in series to the heater winding.

[Embodiments of the invention]

A first embodiment of a lighting circuit for a fluorescent lamp according to an embodiment of the present invention
As shown in the figure. Components that are the same as those in FIG. 6 are designated by the same reference numerals. In FIG. 1, a heater circuit consisting of a heater winding N81 and a heater electrode H1, a heater circuit consisting of a heater winding N1 (2) and a heater electrode H2, each have 1. Capacitor CHI-CH
2 is connected.

Each capacitor C, C has HI flowing when it is lit.
R2 is inserted in a position where the lamp current and heater current flow in the same way.

The secondary circuit of the transformer T in the lighting circuit of FIG. 1 can be equivalently represented as shown in FIG. 2. Here, z
z<z=z> is the impedance of the capacitor CH1, C[12, respectively, CI' C2CI C2, 2° is the impedance of the stabilizing capacitor C1, EH1E1
1□ (EI11 = E82) are the heater windings.
The induced voltage of HIN and El are the induced voltages of the lamp current winding N8. The part consisting of the heater electrodes H1 and H2 and the fluorescent lamp FL is the resistance R and R (R=R) of each heater electrode H1 and H2, respectively) It H2+11
82 1/2 points C and D can be equivalently represented as if the lamp resistor R1 was connected.

Figure 1 shows each winding N□1. “H?”s are wound in the same direction, so the induced instantaneous voltage E11゜E112
．． "L has the same polarity as shown in FIG.

Therefore, the voltage EH1-El□2. E, new current'
111- IH2 (IHl” ■H2), IL is also the second
Flows in the direction shown in the figure. Note that while the switch S is open and the lamp is on, it is stabilized by the stabilizing capacitor C1, so the voltage E due to the lamp current winding, the impedance Z, and the power source are approximately constant current sources (
E, /Z, )”.

The operation will be explained below using FIG. 2. When switch S is closed, the lamp current due to voltage E, ■
, only circulates as a reactive current in a closed circuit consisting of voltage E and impedance Z, and does not flow through the lamp resistor R[, which is the load, so the fluorescent lamp FL does not light up.

At this time, each heater current 1. 1 is each old
H2 Power supply E) I, → impedance Zc shown by the broken line in Figure 2
1-→1/2 heater resistance 1/2RH1→point C→1/2 heater resistance 1/2R-+power supply EH1 path and power supply E□
Flows through the following path: 2 old → 1/2 heater resistance 1/2 RH2 → point D → 1/2 heater resistor, 2 → impedance 2°2 → power supply E■2.

Therefore, in the preheating state of the heater without lighting, each impedance Z Z has a heater current C1'C2'111. Only Ill□ is played. Therefore, if the desired heater preheating voltage is VH, each impedance Zc1. By selecting Zo2, a desired heater preheating voltage vl can be obtained without unnecessary loss.

By the way, impedance z z is the imaginary part CI'
C2, so depending on the resistor, it may not be possible to select it optimally, but capacitor C■1. The optimum value can be selected depending on C■2.

When the switch S is in the open state, a voltage E1 is applied to the heater circuit, a discharge occurs between the heater electrodes iH1 and 1''2, a lamp current T flows, and the fluorescent lamp FL is lit.

At this time, the lamp current ■, as shown by the solid line arrow in FIG. 2, changes from the power source E to the impedance 2. After passing through, the flow is divided and one side is connected to heater M source E□1 → impedance ZC1 → first
reaches point C through 1/2 heater resistance 1/2R, ,
The other reaches point C through the second 1/2 heater resistor 1/2R1 (1), and after being merged at point C, flows to the lamp resistor R6.Then, the current is divided at the lamp point, and one flows to the second 1/2 heater resistance 1/2RH2 → impedance Zc2
→It reaches point B through the heater power supply EH2, and the other reaches point B through the first 1/2 heater resistance 1/2R2, and after being merged at point B, it takes a route back to the power supply E.

Therefore, when lit, the impedance is 2°1. ZC2 has IH1+1/2 I, , I +1/2 respectively
I [of] 12 Current flows. Since the current flows 1/2 I more than when the lights are off, the heater voltage when the lights are on is equal to the voltage vH mentioned above.
It becomes lower by 1/2zo11L or 1/2ZC2TL. That is, during lighting, heater electrodes H1 and H2
Therefore, the power loss at the heater electrodes 1-11. H2, the reliability of the fluorescent lamp FL can be improved.

As described above, according to the circuit of FIG. 1, the capacitor C,
By selecting the value of C so as to satisfy equations (1) and (2), the heater power source EH4゜E)12 can be adjusted to avoid unnecessary loss in the heater circuit.
can be set. Furthermore, since the desired heater voltage is lowered during lighting, the efficiency of the circuit can be increased, and wear and tear on the heater electrode and the fluorescent lamp can be suppressed to achieve high reliability.

Figure 3 shows that the winding direction of heater windings N and N is old.
H2 shows an example for the opposite case, in this case the capacitor 0
．． 2 may be inserted between the connection midpoint B and the heater electrode H2 so that the directions of the lamp current ■1 and the heater current 'H2 match, and the same effect as in the above embodiment can be obtained. .

Moreover, FIG. 4 shows an embodiment in which the switch S is connected in series with the lamp current winding N, and in this case, compared to the above-mentioned embodiment, the on/off operation for turning on or off the lamp is easier. It is only the opposite, and the same effect as in the above embodiment can be obtained.

Furthermore, although the above-mentioned embodiment has been shown for the case where there is one fluorescent lamp FL, it can also be applied to the case where there is a plurality of fluorescent lamps FL, for example, there are two fluorescent lamps.
In the case of a book, the structure may be as shown in FIG. That is, one of the lamp current driving circuit and the heater circuit is connected to the fluorescent lamp FL1. Each FL2 is constructed as in the above embodiment, and the other heater circuit of each of the fluorescent lamps FL1 and FL2 is connected to one common closed circuit, that is, a heater winding N□2, a heater electrode H2, and a heater electrode H2. Electrode H3, capacitor CH2, and heater winding N)1
2.

〔Effect of the invention〕

As described above, according to the present invention, since a capacitor is inserted in series with a heater circuit having a heater winding and a heater electrode, the induced voltage of the heater winding can be reduced so as not to cause extra loss in the heater circuit. Can be set.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a lighting circuit for a fluorescent lamp according to one embodiment of the present invention, FIG. 2 is an equivalent circuit thereof, and FIGS. 3 to 5 are respective circuit diagrams showing a lighting circuit for a fluorescent lamp according to other embodiments of the present invention. FIG. 6 is a circuit diagram showing a lighting circuit for a conventional fluorescent lamp. INV...Inverter circuit, T...Transformer, N. Nsi, N32...Lamp current winding, N111~N
□3...Heater winding, FL, FLl, FL2...
Fluorescent lamp, H1-H4...Heater electrode, S, S,
S... Switch, C1, C2... Stability capacitor, CH1~C] 13... Capacitor for heater circuit control. Applicant's agent Setsu Ino Situation Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. An inverter circuit that converts a DC voltage into an AC voltage, a transformer to which the output AC voltage from the inverter circuit is applied to a primary winding, and a transformer provided on the secondary side of the transformer. a lamp current winding for supplying a lamp current to the fluorescent lamp; a switch for controlling on/off the supply of the lamp current to the fluorescent lamp; A lighting circuit for a fluorescent lamp, comprising: a heater winding that supplies heater current to a heater electrode of the lamp; and a capacitor connected in series to the heater winding. 2. A fluorescent lamp lighting circuit according to claim 1, wherein the capacitor is connected to a position where the direction of the lamp current and the direction of the heater current match.