Adjusting feedback gain in a fluorescent lamp dimming control

A method for normalizing current feedback in a fluorescent lamp dimming control connected to a fluorescent lighting system by adjusting feedback gain of the dimming control, said method comprising the steps of:

• (1) turning on full power to said fluorescent lighting system;
• (2) setting said feedback gain to an initial value;
• (3) measuring current flowing to said lighting system after initial transients decay and before the lamps of said lighting system begin conducting, using said feedback gain to obtain a measured current value;
• (4) comparing said measured current value with a control reference value to ascertain any difference therebetween;
• and
• (5) if the ascertained difference is greater than a predetermined value, then adjusting said feedback gain in a manner which causes said measured current value to approach said control reference value.

A method for adjusting feedback gain of a fluorescent lamp dimming control connected to a fluorescent lighting system, said method comprising the steps of:

• (1) turning on full power to said fluorescent lighting system;
• (2) setting said feedback gain to its highest permissible value;
• (3) measuring current flowing to said lighting system after initial transients decay and before the lamps of said lighting system begin conducting, using said feedback gain to obtain a measured current value;
• (4) subtracting a control reference value from said measured current value;
• (5) if the result of said subtracting step is positive, than decreasing said feedback gain by a single predetermined step;
• and
• (6) repeating steps 3-5 until the result of said subtracting step is not positive, whereby the first feedback gain value giving a non-positive result in said subtracting step is the final value.

Apparatus for providing adjustable current feedback in a microprocessor controlled fluorescent lamp dimming system comprising:

• current sensing means adapted to be coupled to a fluorescent lighting system including a ballast for providing a voltage proportional to the current flowing to the ballast of said fluorescent lighting system;
• adjustable scaling means coupled to said current sensing means for scaling said voltage with an adjustable gain, said adjustable scaling means being adapted to be coupled to said microprocessor for receiving the amount of said adjustable gain;
• voltage-controlled oscillator means coupled to said adjustable scaling means for providing a signal having a frequency proportional to the magnitude of the output signal of said scaling means;
• and
• counter means coupled to said voltage-controlled oscillator means for counting the pulses in said signal provided by said voltage-controlled oscillator means, said counted pulses representing the integral of said output signal of said scaling means, said counter means being adapted to be coupled to said microprocessor for providing the results of said counting to said microprocessor.

A fluorescent lamp dimming system comprising:

• a microprocessor;
• current sensing means adapted to be coupled a fluorescent lighting system for providing a voltage proportional to the current flowing to the ballast of said fluorescent lighting system;
• adjustable scaling means coupled to said current sensing means and said microprocessor for scaling said voltage with an adjustable gain, the amount of said gain being controlled by said microprocessor;
• voltage-controlled oscillator means coupled to said adjustable scaling means for providing a signal having a frequency proportional to the magnitude of the output signal of said scaling means;
• and
• counter means coupled to said voltage-controlled oscillator means and said microprocessor for counting the pulses in said signal provided by said voltage-controlled oscillator means, said counted pulses representing the integral of said output signal of said scaling means, said counter means separately counting pulses during each half-cycle of current supplied to said fluorescent lighting system.