JPH0378997A - Fluorescent lamp lighting circuit - Google Patents

Abstract

PURPOSE:To realize a fluorescent lamp lighting circuit having the stability and the high reliability by making four MOS-FET connected in the full bridge type inverter structure to self-oscillate with the timing signal of the commutation to be generated by a coil connected to a fluorescent law in series. CONSTITUTION:Switching elements Q1-Q4 connected in full bridge type and for operating the oscillation of an inverter, a coil TIE connected to a fluorescent lamp 2 in series and for generating the timing signal of the commutation, and an initial trigger generating unit 3 for forcedly turning ON the predetermined element among the switching elements Q1-Q4 when a power source is closed are provided. In this case, four MOS.FET are formed into a full bridge type inverter, and a stabilizer L is used to supply the high frequency current to the fluorescent lamp 2. Design and manufacture of the stabilizer L is thereby facilitated and, furthermore, a lighting circuit having the high reliability can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a lighting circuit for a fluorescent light using an inverter system, and particularly to a circuit that provides stable lighting operation.

<Summary of the Invention> The present invention provides an all-bridge configuration MOS (M et
al Oxide Sem1conductor)
- This is an inverter-type fluorescent light lighting circuit that performs self-excited commutation for FET (field effect transistor) using a transformer, and is designed to ensure stable circuit operation.

<Prior art> Recently, inverter type circuits have been widely used for fluorescent light lighting circuits because they have less flicker and are not affected by 50/60 cycle regions.

Figure 3 is a lighting circuit diagram of a bush-pull self-excited inverter using NPN transistors Qll and Qll. In Figure 1, 11 is a rectifier that converts AC power to DC power, and Tll is a winding Lll to L14. transformer,
12 is a fluorescent tube, and R11 and R12 are resistors.

When the power is turned on, Qll, Qll due to the difference in characteristics
Either one of them is in the ON state. The subsequent action is the fourth
As shown in the waveform diagram shown in the figure, the winding Lll induces a positive voltage on the side of L13 marked with a positive sign by the ○N current of Qll, turning Q10 on the opposite side into an ON state. Next, due to the ON current of Q10, L12 induces a negative voltage opposite to the above on the ・ mark side of L13, turning Qll ON again and turning Ql2 OFF.
Set it to state F. By repeating this operation, L
A high frequency current is generated at 14 to light up the fluorescent tube 12.

<Problems to be solved by the present invention> In this conventional circuit, the ON current of Qll (I 11) flows through Lll, and the ON current of Ql2 (112) flows through L.
12, if the transformer Tll is operated in a state where Ill≠112, biased magnetization due to the DC component occurs in the transformer Tll.

Gradually, magnetic saturation progresses. As this progresses, the ON current of 211.112(7) naturally increases, and Qll, Q
This will degrade or destroy l2. As a countermeasure to this, a transformer T that is difficult to magnetically saturate even when subjected to biased magnetism.
It is necessary to produce ll. Further, L14 requires an optimum impedance (Z) value to also function as a stabilizer in order to cause the fluorescent tube 12 having negative resistance characteristics to perform a stable discharge operation. Furthermore, it is necessary for L13 to stably generate a self-excited commutation timing signal.

However, the design of the transformer Tll as described above
The production was extremely difficult.

SUMMARY OF THE INVENTION An object of the present invention is to solve these conventional problems and provide a stable and highly efficient inverter type fluorescent light lighting circuit without using special hardware.

Means for Solving Problems> The fluorescent lamp lighting circuit of the present invention is a lighting circuit in which fluorescent tubes 2 are lit by an inverter method using commutation, and is connected in a full bridge type to operate the oscillation operation of the inverter. A winding T1E connected in series with the fluorescent tube 2 to generate the commutation timing signal, and a predetermined element among the switching elements Q1 to Q4 are forced to operate when the power is turned on. It is characterized by the provision of an initial trigger generation section 3 that is turned ON (conductive) at a specific time.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to FIGS. 1 and 2. In FIG. 1, Q1 to Q4 are switching elements of enhancement type MOS-FET, and the rectifying section 1
Connect the circuit to the output side of the inverter to form a full bridge inverter. A winding TIA-TID is connected between the gate and source of each of Q1 to Q4 to form a bias circuit (the protection circuit is not shown).The winding TIA-T1E is a gate trigger transformer. Each winding constitutes T1, one winding T1E is connected in series with the ballast and fluorescent tube 2 to obtain a timing signal for commutation. Reference numeral 3 denotes an initial trigger generating section, which applies a positive voltage to the drain and gate only at the time of turning on the AC power in order to turn Ql on (conducting). Although the circuit is not shown, it is a simple one in which a diode and a diac are connected to a CR circuit of a resistor (R) and a capacitor (C). L is a ballast having an impedance (Z) value appropriate for the fluorescent tube 2 having negative resistance characteristics, and C is a starting capacitor.

The operation of this circuit is as shown in the waveform diagram of FIG.
At the same time, the trigger current flowing through TIA induces a positive voltage on the - side of TIB, and Ql is also turned on. At the same time, voltage is induced in Tic and TID, but since the winding directions are opposite, Q3. Q4 remains in the OFF state. As a result, the circuit current from the rectifier 1+ flows in the order of Q2→L→C−+TIE→Q1, and preheats the filament of the fluorescent tube 2.

Next, as the circuit current flows through T1E, TL
A positive voltage is induced on the ・mark side of C and TID, and Q3 and Q
Turn on 4. At the same time, a voltage is induced that makes the - side of TIA and TIB negative, so Ql and Ql are OFF.
state. As a result, the circuit current is Q4→T1E-+C
-+L-+Q3 flows in the order - preheats the filament in the same way as above, but the direction of the current is opposite. Next, T1
The above circuit currents flowing through E are TIA and TIB, Tic:
The positive and negative voltages induced in the TID again turn Ql and Ql ON, and turn Q3 and Q4 OFF, respectively. By repeating such operations, a high frequency current is supplied to the ballast and the fluorescent tube 2, and the filament is preheated to start discharging and the fluorescent tube 2 lights up. In addition, in the preheating operation of the filament by current, as the current in the tube from the heated electrode gradually increases, discharge starts due to the dynamic characteristics of the fluorescent tube and the impedance (Z) of the stabilizer. When the light is turned on, the voltage across the fluorescent tube 2, that is, the capacitor C, decreases, the current decreases, and the process automatically ends. In this way, the gate trigger transformer T1 is sufficient for generating extremely small power to drive the MOS-FETs Ql to Q4, and it has a structure in which it is wound together with the power transformation coil like the transformer 11 described above. Since there is no such thing, design and manufacture are easy, stable operation, miniaturization, and quality improvement can be realized.

In addition, since the four MOS-FETs are configured as a full bridge inverter and the high frequency current is supplied to the fluorescent tube 2 using stability, magnetic saturation and loss generation as in the case of the transformer T11 described above are avoided. There are no problems, the ballast is easy to design and manufacture, and a highly reliable lighting circuit can be realized. In addition, in consideration of noise, it is also possible to use the ballast (choke coil) L of this embodiment in place of a leakage transformer in which the primary and secondary windings are loosely coupled so that the leakage inductance L is equivalent. It is. Furthermore, the filament preheating circuit could be implemented using only the capacitor C because the current for preheating the filament automatically decreases after the fluorescent tube 2 starts discharging, i.e., after lighting, resulting in a negligible low loss. The lighting circuit of the present invention can be replaced with a conventional glow discharge tube, making it possible to provide a simple and long-life fixture.Furthermore, the lighting circuit of the present invention can be replaced with the ballast and glow discharge tube of a conventional fluorescent lamp. Yes, it can be promoted. It is also possible to connect two ballasts and fluorescent tubes 2 in parallel.

<Effects of the Invention> As explained below, according to the present invention, in the advance lighting circuit for lighting a fluorescent tube using an inverter method, four MOSs connected to a full bridge type inverter configuration are used.
- Since the FET is caused to self-oscillate by the commutation timing signal generated by the winding T1E connected in series with the fluorescent tube,
By using the transformer T1 and the stabilizer, which are easy to design and manufacture without using any special hardware, it is possible to realize a stable and highly reliable front-running light circuit.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a front running light showing an embodiment of the present invention;
2 is a waveform diagram showing the operation of FIG. 1, FIG. 3 is a lighting circuit diagram of a conventional bush-pull type self-excited inverter, and FIG. 4 is a waveform diagram showing the operation of FIG. 3. 1.11: Rectifier section, 2.12: Fluorescent tube, 3: Initial trigger generation section, C: Starting capacitor, Lll to L14,
TIA-TLE: Winding, Q1-Q4: MOS/FET,
Qll, Ql2: NPN transistor, R11, R
12: Resistor, T1: Gate trigger transformer, T11
Nidorance.

Claims (1)

[Claims] In a fluorescent light lighting circuit that lights a fluorescent tube 2 using an inverter method using commutation, switching elements Q1 to Q4 that are connected in a full bridge type and perform an oscillation operation of the inverter are connected in series with the fluorescent tube 2. A winding T1E is connected to generates the commutation timing signal, and an initial trigger generating section 3 is provided to forcibly turn on (conduct) a predetermined element among the switching elements Q1 to Q4 when the power is turned on. A fluorescent lighting circuit characterized by: