Electronic Ballasts

Electronic ballast uses solid state circuitry to transform voltage, but unlike EM ballasts, can also alter the frequency of power. High-frequency operation of >20KHz increases the fluorescent lamp efficiency by 10% since the conversion rate of UV radiation increases. The advantage of this is that the lamp requires less input power for the same light output leading to an energy saving. Because it uses solid-state circuitry instead of magnetic coils, it is also more efficient and therefore runs cooler.

Electronic ballasts were first introduced as simple inverter ballasts. They perform the basic function of starting the lamp and controlling the lamp current. These ballasts were typically used in retrofit Compact Fluorescent Lamps but suffered from problems of low power factor (around 0.5) and high THD (~120%).

Active Power Factor Correction ballasts incorporate filters and active control circuits to correct the power factor closer to unity and also minimize the Total Harmonic Distortion to >10%.

Inverter Electronic Ballast

Inverter electronic ballast

  1. An AC input is fed to AC-DC converter, which converts the AC voltage to DC
  2. DC is Inverted into high frequency AC using an inverter, which is fed to the lamp using lamp circuit.

Electronic ballasts with Active Power Factor Correction

Electronic ballasts with active power factor correction
  1. A/C input is converted to DC using a AC-DC converter and gives input to the Active Harmonic Filter.
  2. Active Harmonic filter comprises of Buck/Boost circuit along with HF rectifier and control circuit
  3. Filter maintains the voltage at its output constant at 400 V (DC).
  4. The output voltage of DC-AC inverter and wattage input to the lamp remains constant (for input line voltage variation 145V-275V).
  5. Constant wattage operation and constant light output is achieved.