Visible light communication apparatus
View Patent ↗A visible light communication apparatus includes a constant current circuit and a load circuit including light emitting elements connected to output terminals of the constant current circuit. Further, the visible light communication apparatus includes 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.
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:
MH
=
(
r
1
+
rd
1
)
×
i
1
+
Vd
(
r
1
+
rd
1
+
N
×
rl
1
)
×
i
1
+
Vd
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.
2. The visible light communication apparatus of claim 1 , wherein the diode is a rectifier diode.
3. The visible light communication apparatus of claim 1 , wherein the diode is a light emitting diode.
4. The visible light communication apparatus of claim 1 ,
wherein a magnitude of a load current flowing through the load circuit when the load variation circuit is electrically connected to the load circuit is smaller than a magnitude of a load current flowing through the load circuit when the load variation circuit is electrically disconnected from the load circuit.