Signal transmitting device, signal receiving device, lighting system, illumination fixture, and illumination system

A signal transmitting device comprising:

• an input unit including first and second input terminals configured to receive a DC input voltage:
• an output unit including first and second output terminals configured to output a DC output voltage, the first output terminal being electrically connected to the first input terminal;
• and
• a step-down circuit that is provided between the input unit and the output unit, and is configured to controllably adjust the output voltage by stepping down the input voltage, the step-down circuit including:
• a first capacitor electrically connected between the first and second input terminals;
• a second capacitor electrically connected between the first and second output terminals;
• a switch circuit that includes a series circuit of first and second switches, and is electrically connected in parallel to the first capacitor;
• an inductor that includes a first terminal electrically connected to a connection point of the first and second switches, and a second terminal electrically connected to a connection point of the second capacitor and the second output terminal;
• a first diode that is electrically connected in parallel to the first switch and has a cathode electrically connected to a terminal of the first switch on a high potential side of the first switch and an anode electrically connected to a terminal of the first switch on a low potential side of the first switch;
• a second diode that is electrically connected in parallel to the second switch and has a cathode electrically connected to a terminal of the second switch on a high potential side of the second switch and an anode being electrically connected to a terminal of the second switch on a low potential side of the second switch;
• and
• a control circuit configured to control the first and second switches, the control circuit being configured to control the first and second switches to change a voltage value of the output voltage in order to transmit transmission data from the output unit.