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Electronic ballast for fluorescent tubes 8 - 144W

     I developed a simple and inexpensive electronic ballast for one or more fluorescent lamps with total power up to 144W.
     Electronic ballast has a much higher efficiency than a conventional magnetic ballast, eliminates the stroboscopic effect and blinking, allows fast start with no flicker and extends the life of fluorescent lamps. Also it eliminates the use of glow starters and problems with compensation of phase shift. Moreover, high-frequency excited fluorescent tube has about 10% more light output at the same power. Comparison of their traditional power inductors and electronic ballast for typical lamps shown below:

FLUORESCENT TUBES 18W 2x 18W 3x 18W 4x 18W 36W 2x 36W 3x 36W 4x 36W 58W 2x 58W
Conventional (magnetic) ballast self consumption 9W 18W 27W 36W 9W 18W 27W 36W 13W 26W
Electronic ballast self consumption 2,5W 2,9W 3,5W 4,3W 2,8W 3,8W 4,9W 6W 3,2W 4,2W

     Circuit works as a halfbridge with MOSFETs. They are driven from IR2153 integrated circuit. Working frequency is 35kHz (ideal frequency RF excitation fluorescent lamps). This ballast can power almost any fluorescent lamps. The values of C1 and L1 adapts to the power (ie the current) of desired fluorescent tube. For thin fluorescent lamps (T5 size, diameter 16mm, 4 - 21W) and Small fluorescent DZ (U-shape or 2U, 5 - 18W, without integral starter - 4-pin) can be used capacitor and choke from almost any energy saving lamps (CFL). Capacity of starter capacitor is about 2n2 to 3n3. The converters can be connected the broken tube-saving lamps with the original choke and starting capacitor. Output voltage and frequency corresponds to the halfbridege used in compact fluorescent lamps (rectangular waveform approximately 160V 35kHz). For bigger fluorescent lamps (T8 26 mm or 38 mm and large T12 fluorescent DZ, 15 - 65W, 0.38 to 0.43 A) you must wind a coil with appropriate inductance and sufficiently dimensioned, or combine 2 to 3 chokes from CFL in parallel. Large fluorescent lamps are rated from 0.38 to 0.43 A. The current through fluorescent lamp can be fine-tuned by changing the inductance coils (change of air gap) or a small change in operating frequency. Change is possible in the range of about 30 - 40 kHz and is achieved by changing the value of components in the oscillator (330p, 68k). Starter capacitor C1, C2 is chosen to be close to resonance with the choke. For large fluorescent lamps are selected about 10nF. After switching there is increased voltage of around 500V, the lamp ignites. C1, C2 has to be rated 1000V. Capacitor C3 protects MOSFETs against voltage peaks from the inductance and reduces the value of the voltage rate of rise (dU / dt). Its capacity is chosen so to avoid hard switching (about 5 - 6nF to 1A of current to fluorescent lamps). Should be pulse, rated 1000V. Due to the high efficiency, the total power into fluorescent lamps can be accurately estimated by the current, which is measured at the filter electrolyte. The voltage here is about 300V. Subtracted own consumption ballast around 3W. The ballast can add more lamps in parallel. Each then has its own capacitors and inductors.

     Used transistors (IRF840 or STP9NK50Z) do not need to have heatsink up to 72W of output power. Own consumption of the circuit is about 2.5 - 6W (under load). Input power is connected RFI filter and thermistor to limit peak inrush current during switching on. For low power it can be replaced by ordinary resistor. Voltage 15V for circuit IR2153 is obtained the power resistor from the rectified mains voltage 300V. Zener diode is not needed - that is already built in IO (Uz = 15V). Precipitation resistance 33k has a loss of about 2.3 watts and is the largest dissipator in the circuit. But the loss of ballast is nevertheless much smaller than when using conventional inductors. (If you want to get rid of this dissipation, you can use a micropower startup resistor of about 1M and derive the power for IR2153 from the output of the halfbridge via a little capacitor, like it is done in most of electronic ballasts.) The capacitance of the filter electrolyte capacitor depends on the power of the lamps. It is calculated about 0.3 - 1uF per Watt.

     Warning! The entire circuit is galvanically connected to the mains! All its parts must be protected against accidental contact. Improper construction can cause fluorescent lamps explosion.

The schmematic of the electronic ballast for fluorescent tubes.
The schmematic of the electronic ballast for fluorescent tubes.

Completed homemade electronic ballast for tubes 2x 36W.
Completed homemade electronic ballast for tubes 2x 36W.

testing the homemade electronic ballast
testing the homemade electronic ballast on tubes DZ 36W. The coils have 200 turns of wire diameter 0.35mm, they are on ferrite core EE 40mm2 and have air gap of 1.3mm between Es. C1 and C2 are 10n 1000V, C3 is 4n7 1000V.