Patent ID: 9553667
Date: 2017-01-24
CPC Classifications: H04B,H05B

Claim:
1. A visible light communication apparatus comprising: a constant current circuit; a load circuit including light emitting elements connected to output terminals of the constant current circuit; a load variation circuit configured to change load characteristics of the load circuit by electrically connecting to the load circuit, the load variation circuit including a series circuit of a diode and a resistor connected in series to the load circuit; and a switching element configured to electrically connect or disconnect the load variation circuit to the load circuit in response to a binary communication signal, wherein the load variation circuit and the switching element are connected in parallel, wherein the load variation circuit partially changes load characteristics of the load circuit, wherein a resistance value of the resistor is greater than a resistance value of an equivalent resistance of the diode, and wherein a modulation degree MH of illumination light of the light emitting elements as a result of turning the switching element on and off is represented by: where r1 represents the resistance value of the resistor, rd1 represents the resistance value of the equivalent resistance of the diode, i1 represents a load current through the load circuit when the load variation circuit is added to the load circuit, Vd represents a forward voltage of the diode at a point in time when current starts to flow through the diode, N represents a number of the light emitting elements connected in series in the load circuit, and rl1 represents a resistance value of an equivalent resistance of each of the light emitting elements.