Digital communication interface circuit for line-pair with duty cycle imbalance compensation

A device comprising:

• an interface circuit configured to interface a controller with a Digital Addressable Lighting Interface (DALI) bus, wherein the interface circuit comprises:
• a diode bridge having polarity-independent input terminals configured to be coupled to the DALI bus, and further having a positive output terminal and a negative output terminal;
• a variable edge delay circuit configured to receive a transmit signal generated by the controller and to delay rising edges of the transmit signal substantially more than falling edges of the transmit signal, or to delay falling edges of the transmit signal substantially more than rising edges of the transmit signal;
• an optocoupler having a pair of input terminals configured to receive the transmit signal from the variable edge delay circuit and having first and second output terminals;
• an amplifier having an input terminal and an output terminal, wherein the input terminal is connected to one of the first and second output terminals of the optocoupler;
• a voltage-controlled variable resistance element connected across the positive and negative output terminals of the diode bridge, and having a control terminal for varying a resistance thereof;
• and
• a first filter connected between the output terminal of the amplifier and the control terminal of the voltage-controlled variable resistance element, wherein the first filter includes decoupled charge and discharge paths so as to decouple a rise time of the transmit signal from a fall time of the transmit signal,
• wherein the voltage-controlled variable resistance element is configured to couple the transmit signal to the DALI bus via the diode bridge.