Electronic ballast with interface circuitry for multiple dimming inputs

A gas discharge lamp ballast for use with a power line controller, said ballast comprising:

• only two mains input terminals for connection to a common line and a hot dimmed line from a power line controller, the hot dimmed line carrying an AC mains voltage including dimming control commands encoded by the power line controller;
• a full bridge rectifier connected to the two mains input terminals for providing a full wave rectified DC output voltage, the rectified DC output voltage including the control commands encoded by the power line controller and having a peak voltage;
• a preconditioner circuit connected to the full-bridge rectifier, said pre-conditioner circuit including an up converter for providing a DC supply voltage at a level higher than the peak voltage of the rectified DC output voltage from said full-bridge rectifier;
• an inverter circuit receptive of the DC supply voltage from said pre-conditioner circuit, said inverter converting the DC supply voltage from said preconditioner to a high frequency AC voltage having a frequency substantially greater than the frequency of the AC mains supply;
• a resonant tank output circuit receptive of the high frequency AC inverter output voltage, said output circuit having lamp connection terminals for connection to a gas discharge lamp, said output circuit providing a substantially sinusoidal lamp current to a gas discharge lamp connected at said lamp terminals;
• a control circuit connected to the inverter for controlling the AC inverter output voltage, said control circuit having (i) means for receiving a dimming signal separate from the DC output of the pre-conditioner circuit, (ii) means for sensing the power supplied to the gas discharge lamp, and (iii) means for adjusting the AC inverter output frequency fed to said resonant tank output circuit to thereby control the electrical power supplied to the gas discharge lamp at a level corresponding to the voltage of the dimming signal;
• and
• a dimming interface circuit receptive of the encoded rectified DC output voltage from said full-bridge rectifier, said dimming interface circuit including decoding means for decoding control commands present in the input signal according to any one of at least two of the following:
• (i) a first control technique wherein commands are indicated by the phase angle of a phase angle cut in the nominal waveform;
• (ii) a second control technique wherein commands are indicated by the number of fundamental periods between start and stop points of the command, the stop and start points being fundamental periods having a nominal voltage less than the nominal waveform;
• and
• (iii) a third control technique wherein commands are indicated by an occurrence signature of a pre-selected perturbation in the nominal waveform occurring within a control period of a pre-selected number of fundamental periods;
• and
• said dimming interface circuit further including means coupled to said decoding means for generating a said dimming signal corresponding to the dimming command decoded by said decoding means.

A receiver for use with a controller for an electric lamp, said receiver comprising:

• 1) input means for receiving an input signal carrying control commands, said input signal having a fundamental period with a nominal voltage waveform;
• and
• 2) decoding means for decoding control commands present in the input signal according to at least two of:
• (i) a first control technique wherein commands are indicated by the phase angle of a phase angle cut in the nominal waveform;
• (ii) a second control technique wherein commands are indicated by the number of fundamental periods between start and stop points of the command, the stop and start points being comprising fundamental periods having a nominal voltage less than the nominal waveform;
• and
• (iii) a third control technique wherein commands are indicated by an occurrence signature of a pre-selected perturbation in the nominal waveform within a control period of a pre-selected number of fundamental periods.

A method of controlling an electric lamp, said method comprising the steps of:

• a) receiving an input signal carrying control commands, said signal having a fundamental period with a nominal voltage waveform;
• b) identifying the presence in said input signal of control commands according to any two of:
• (i) a first control technique wherein commands are indicated by the magnitude of a phase angle cut in the nominal waveform;
• (ii) a second control technique wherein commands are indicated by the number of fundamental of the between start and stop points of the command, the stop and start points being fundamental periods having a nominal voltage less than the nominal waveform;
• and
• (iii) a third control technique wherein commands are indicated by an occurrence signature of a pre-selected perturbation in the nominal waveform within a control period of a pre-selected number of fundamental periods;
• c) decoding a control command present according to the identified one of said techniques;
• and
• d) controlling the operation of the electric lamp in response to the decoded command.