Traditional switching circuits for fluorescent lamps designed to be powered by an alternating current of industrial frequency. Today, the increasing power of such lamps with high-frequency current, which eliminates the flashing and improves the reliability of the launch. Eliminates the need for bulky capacitors and chokes on steel cores, often releases an unpleasant buzz. The proposed high frequency unit is small in size, contains the minimum number of winding elements, simple and easy to repeat.
The block design, intended for powering fluorescent lamps OSRAM L 13W diameter of the bulb 16 mm, shown in Fig. 1. Through FU1 fuse-link and the noise filter C2L1 mains voltage is supplied to the diode bridge VD1-VD4. The inverter on the chip IR2153 (DA1) and field-effect transistors IRF840 (VT1, VT2) converts the rectified voltage into a symmetrical rectangular pulses. Detailed information about the chip IR2153 and transistors IRF series you can find them on the website of the manufacturer www.irf.com.
Fig.1. Schematic diagram of the block
The frequency of the pulses depends on the values of the elements of timing chain R1С4 and in the present case equal to 33 kHz. Between the pulses at the outputs BUT LO and chips, administering field transistors VT1 and VT2 are automatically maintained pause 1.2 μs. This prevents the simultaneous opening of the transistors passes through "pass-through" current.
The voltage supply circuits DA1 is supplied to the terminal 1 through the quenching resistor R2, and an internal Zener diode prevents the increase of the potential difference between pins 1 and 4 over 15.6 V. In operation here 9...10 V.
The output voltage of the inverter is supplied to the lamp EL1 through the coupling capacitor C8 and the ballast inductor L2. The appointment of the latter as a standard used in the circuit of lamp current frequency of 50 Hz, but the frequency in this case is much higher, the inductance of the inductor, its size and weight is much less. The capacitor C6 form a circuit heating of the filaments of the lamps.
The unit is assembled on a printed circuit Board (Fig. 2) size 100x25 mm. Capacitors C1, C2, C8 - K73-17, C4, and C6 - C-2, oxide - C50-35. Inductors L1 and L2 are wound on the magnetic cores Sh ferrite M2500NMS or MNM. Winding of the inductor L1 contain 200 turns of wire sew-2 0.1 mm and is wound in isolated sections of the frame. Half of the magnetic circuit of the throttle stick together without a gap. The winding of the inductor L2 - 220 turns of wire sew-2 0.22 mm. In its magnetic circuit required, non-magnetic gap, the thickness of which (0,3...0,5 mm) is selected empirically with the most gorgeous glow lamp.
Fig.2. Printed circuit Board
Diodes VD1-VD5 can be replaced by any other for a current of less than 0.5 A and a reverse voltage of At least 400, for example, KGA-CDV, KDV-CDD. Thus, the dimensions of the PCB will have to increase. Replacement transistors IFR840 possible to IRF830, IRF820, but will lead to degradation of the thermal regime due to the higher resistance of the channel.
Making the unit small changes, can be powered from him and more powerful lamps. For example, in Fig. 3 shows how to connect two lamps LDC-20-2. The cross section of the magnetic circuit of the inductor L2 is increased to 6x6 mm, the wire diameter - to 0.4 mm, and the number of turns is reduced to 120. The inductor L3 is identical to L2. On the same magnetic core is wound and the inductor L1, increasing the wire diameter of 0.3 mm.
Fig.3. Circuit of two lamps
The capacitance of the capacitors C1 and NW (see Fig. 1) increase to 0.68, respectively and 10 µf) and the transistors VT1 and VT2 are provided with heat sinks and a minimum area of 40 cm2. You must also be increased to 2 And the operating current of a fuse FU1, and in the gap of one of the network cables to install the resistor 4.7 Ohm power 5 watts minimum (e.g. a wire) to limit the charging current of the capacitor C3 at the time the unit is switched on.
Author: A. Taraz, St. Petersburg; Publication: www.radioradar.net