JP2946557B2 - Fluorescent lamp lighting circuit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a filament preheating circuit used in a fluorescent lamp lighting circuit to which a high frequency inverter is applied.

2. Description of the Related Art In recent years, fluorescent lamp lighting circuits using a high-frequency inverter have become mainstream. Hereinafter, a conventional technique will be described with reference to the drawings. FIG. 3 is a diagram showing a configuration of a conventional fluorescent lamp lighting circuit. In FIG. 3, reference numeral 11 denotes a power supply circuit, 12 denotes a preheating timer circuit for determining a preheating time of the filament at the time of lighting, 13 denotes a switch circuit controlled by the preheating timer circuit, 14 denotes an inverter driving circuit that outputs a driving signal of the inverter, Reference numeral 15 denotes a drive transistor for driving an inverter transformer, 16 denotes an inverter transformer, 17 denotes a capacitor, and 18 denotes a fluorescent tube. The operation of the fluorescent lamp lighting circuit configured as described above will be described.

First, when the power supply circuit 11 starts, the inverter drive circuit
14 and the preheating timer 12 start. Preheating timer
Reference numeral 12 determines the preheating time of the filament, and keeps the switch circuit 13 open during the preheating time. The inverter drive circuit 14 drives the drive transistor 15, and the drive transistor
15 drives the inverter transformer 16. The inverter transformer 16 generates an AC voltage on the secondary side. Switch circuit 13
Because of the open state, S ₂ winding of the inverter transformer 16 is a voltage between both electrodes of the fluorescent tube 8 becomes the open state is not applied. Therefore, S ₁ winding and the fluorescent tube filament F ₁ of the inverter transformer 16, the filament F ₁ of the fluorescent tube current flows through a combination of filaments F ₂ of S ₃ winding the fluorescent tube 8 of the inverter transformer 16, F ₂ is preheated Is done. Eventually, the preheating timer circuit
When the time of 12 is up, the preheating timer circuit 12 connects the switch circuit 13. When the switch circuit 13 is connected, spike-like high voltage generated in S ₂ winding of the inverter transformer 16 is applied, the fluorescent lamp 8 is lighted, the lighting state of normal.

However, in the above configuration, however, the method of insulating the switch circuit 13 and the preheating timer circuit 12 and the case where it is difficult to obtain an optimum element because the switch circuit 13 requires an element with a very high withstand voltage or cost There is a problem of getting up.

Means for Solving the Problems In order to achieve the above object, the present invention provides a preheating timer circuit and a spike voltage absorption circuit controlled by the preheating timer circuit. A spike voltage component generated in the transformer due to surplus energy inside the transformer during the filament preheating time is absorbed by the spike voltage absorption circuit so that a spike-like high voltage is not applied between the two poles of the fluorescent lamp during the filament preheating time. doing.

Operation According to the above configuration, a preheating circuit can be constituted by relatively low withstand voltage elements in a state where the primary circuit and the secondary circuit of the inverter transformer are completely insulated.

Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an embodiment of the present invention. In FIG. 1, 1 is a power supply circuit, 2 is a preheating timer circuit that determines a filament preheating time at the time of lighting, 3 is a spike voltage absorption circuit that is controlled by the preheating timer circuit, and absorbs a spike voltage generated in the inverter transformer. An inverter drive circuit that outputs an inverter drive signal, 5 is a drive transistor that drives an inverter transformer, 6 is an inverter transformer, 7 is a capacitor, and 8 is a fluorescent tube.
The operation of the fluorescent lamp lighting circuit configured as described above will be described.

First, when the power supply circuit 1 starts, the inverter drive circuit 4 and the preheating timer 2 start. The preheating timer 2 determines the preheating time of the filament and operates the spike voltage absorbing circuit 3 to absorb the spike voltage generated in the inverter transformer 6. Inverter drive circuit 4 drives drive transistor 5, and drive transistor 5 drives inverter transformer 6. Inverter transformer 6 is 2
An AC voltage is generated on the secondary side. Voltage spike voltage absorbing circuit 3 generates in the secondary winding S _1, S _2, S ₃ of the inverter transformer for absorbing spikes component generated inverter transformer 6 has a waveform shown sometimes preheating of Figure 2. Thus, voltage generated at S ₂ the fluorescent tube 8 through the capacitor 7
However, since there is no spike component, the peak value becomes smaller than the starting voltage of the fluorescent tube 8, and no current flows between the two poles of the fluorescent tube 8. Therefore, the inverter transformer 6
Filament F ₁ of S ₁ winding and the fluorescent tube 8, the filament F _1, F ₂ of the fluorescent tube 8 a current flows in the combination of the filaments F ₂ of S ₃ winding the fluorescent tube 8 of the inverter transformer 6 is preheated. Eventually, when the preheating timer circuit 2 times out, the preheating timer 2 terminates the operation of the spike voltage absorption circuit 3. When the spike voltage absorbing circuit 3 ends its operation,
A spike voltage is generated in each winding of the inverter transformer 6 with a waveform as shown at the time of starting in FIG. Spike voltage generated in S ₂ winding of the inverter transformer 6 is applied between both electrodes of the fluorescent tube 8 through the capacitor 7. This spike voltage reaches the starting voltage of the fluorescent tube 8 and soon the fluorescent tube 8
Is in the normal lighting state, and the waveform of each winding of the inverter transformer 6 is the lighting state waveform shown in FIG.

Effect of the Invention As described in detail above, in the fluorescent lamp lighting circuit of the present invention, the preheating circuit is formed by a relatively low withstand voltage element while the primary circuit and the secondary circuit of the inverter transformer are completely insulated. It can be realized, and the effect is great.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of a fluorescent lamp lighting circuit of the present invention, FIG. 2 is an operation waveform diagram of each mode in an embodiment of the fluorescent lamp lighting circuit of the present invention, and FIG. It is a figure showing composition of a fluorescent lamp lighting circuit. 1 ... power supply, 2 ... preheating timer, 3 ... spike absorption circuit, 4 ... drive circuit, 5 ... transistor, 6 ... transformer, 7 ... capacitor, 8 ... fluorescent tube.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H05B 41/24 H05B 41/18

Claims (1)

(57) [Claims] 1. An inverter-type fluorescent lamp lighting circuit having an inverter transformer, wherein a preheat timer circuit and a spike voltage absorbing circuit controlled by the preheat timer circuit are set by the preheat timer circuit when the fluorescent lamp is turned on. A fluorescent lamp lighting circuit characterized in that a spike voltage component generated in the transformer due to surplus energy inside the transformer is absorbed by the spike voltage absorption circuit during the filament preheating time.