Patent ID: 8250873

Claim:
An anti-condensation control apparatus comprising: a sensor circuit comprising a humidity sensor and configured to provide a sensor signal indicative of a relative humidity (RH) on or near a control surface; and a control circuit comprising a phase control circuit configured to: receive the sensor signal and a high-voltage AC power input, and modulate a phase of the high-voltage AC power input at least partly in response to the sensor signal indicative of the RH on or near the control surface and without use of a temperature sensor, the phase control circuit configured to modulate the phase of the high-voltage AC power input in such a manner that a phase-modulated AC power output provided to a heater is: a) substantially constant at a minimum power level (P min ) in a low RH region ranging from 0% RH to a first RH (RH 1 ), b) linearly varying from P min to a maximum power level (P max ) in an intermediate RH region ranging from RH 1 to a second RH (RH 2 ), and c) substantially constant at P max in a high RH region ranging from RH 2 to 100% RH, wherein the phase control circuit does not comprise a digital logic circuit.