Light emitting diode driving circuit
View Patent ↗A LED driving circuit that may control current flow into an LED on a current path according to the amount of light sensed from the LED. An LED driving circuit for driving at least one LED may include at least one of: An optical sensor for receiving light emitted from the LED and generating a feedback signal having a level corresponding to an amount of the received light. A current regulator provided on a path through which current of the LED flows for regulating an amount of current flowing into the LED according to a comparison of the feedback signal with a first reference signal.
1. An apparatus comprising a light emitting diode (LED) driving circuit configured to drive at least one LED, wherein the circuit comprises:
an optical sensor configured to receive light emitted from said at least one LED and generate a feedback signal corresponding to an amount of light received by the optical sensor; and
a current regulator configured to regulate an amount of current flowing into said at least one LED according to a comparison of the feedback signal with a first reference signal,
wherein the current regulator comprises:
a first reference signal generator configured to generate the first reference signal,
a comparator configured to compare a level of the feedback signal with a level of the first reference signal;
a first transistor connected between a negative electrode of said at least one LED and a reference voltage source, where the first transistor is driven in response to the comparison of the feedback signal with the first reference signal; and
a first load connected between the first transistor and the reference voltage source,
wherein the first reference signal generator comprises:
an operational amplifier comprising a positive input terminal configured to receive a second reference signal;
a second load connected between a negative input terminal of the operational amplifier and the reference voltage source;
a second transistor configured to supply a reference current to the second load in response to an output of the operational amplifier;
a current mirror configured to generate a mirror current of the reference current; and
a first resistor, wherein the mirror current flows into the first resistor and wherein the first reference signal corresponds to a voltage across both ends of the first resistor.
2. The apparatus of claim 1 , wherein the reference voltage source is grounded.
3. The apparatus of claim 1 , comprising a switch configured to selectively supply the feedback signal to the current regulator.
4. The apparatus of claim 1 , wherein the current regulator is connected between a negative electrode of said at least one LED and the reference voltage source.
5. The apparatus of claim 4 , wherein the reference voltage source is grounded.
6. The apparatus of claim 1 , comprising:
a voltage inspector configured to inspect a voltage of said at least one LED and generate a control signal; and
a charge pump configured to supply a voltage to said at least one LED according to the control signal.
7. The apparatus of claim 2 , wherein:
the charge pump is configured to supply to said at least one LED the voltage corresponding to an operation mode; and
the operation mode is determined according to the control signal designating one of a plurality of operation modes having different voltage gains.
8. The apparatus of claim 2 , wherein the voltage of said at least one LED is a voltage supplied to said at least one LED.
9. The apparatus of claim 6 , wherein the voltage of said at least one LED is a voltage across both electrodes of said at least one LED.
10. The apparatus of claim 1 , wherein the optical sensor comprises:
a light receiving diode configure to receive light emitted from said at least one LED; and
a third load connected between the light receiving diode and the reference voltage source, wherein the feedback signal is derived from a voltage at a connection point of the light receiving diode and the third load.
11. The apparatus of claim 10 , wherein the reference voltage source is grounded.
12. The apparatus of claim 10 , wherein the light receiving diode comprises:
a negative electrode connected to a charge pump; and
a positive electrode connected to the third load.
13. The apparatus of claim 10 , wherein the light receiving diode comprises:
a negative electrode connected to a positive electrode of said at least one LED; and
a positive electrode connected to the third load.
14. The apparatus of claim 10 , wherein:
the first load comprises a second resistor connected between a positive electrode of the light receiving diode and the reference voltage source; and
the feedback signal is a voltage across both ends of the second resistor.
15. An apparatus comprising light emitting diode (LED) driving circuit configured to drive at least one LED, wherein the circuit comprises:
an optical sensor configured to receive light emitted from said at least one LED and generate a feedback signal corresponding to an amount of light received by the optical sensor; and
a current regulator configured to regulate an amount of current flowing into said at least one LED according to a comparison of the feedback signal with a first reference signal,
wherein the current regulator comprises:
a comparator configured to compare the feedback signal with the first reference signal;
a reference signal generator configured to generate a second reference signal in response to the comparison of the feedback signal with the first reference signal;
an operational amplifier comprising a positive input terminal connected to the reference signal generator;
a first transistor connected between a negative electrode of said at least one LED and a reference voltage source, wherein the first transistor is driven by an output of the operational amplifier; and
a load connected between a negative input terminal of the operational amplifier and the reference voltage source, wherein reference signal generator comprises:
a second transistor through which a reference current flows, wherein the second transistor is driven in response to the comparison of the feedback signal with the first reference signal;
a first resistor connected between the second transistor and the reference voltage source;
a current mirror configured to generate a mirror current of the reference current; and
a second resistor, wherein the mirror current flows into the second transistor and wherein the second reference signal corresponds to a voltage across both ends of the second resistor.
16. The apparatus of claim 15 , wherein the reference voltage source is grounded.