Light-emitting element driving device
The present disclosure provides a light emitting element driving device. The light emitting element driving device includes a constant current circuit and a current detection unit. The constant current circuit includes: a first transistor including a first end, a second end and a control end connected to an external terminal; a current setting resistance connected to the second end of the first transistor; and a drive amplifier including a first input end connected to a first node to which the first transistor and the current setting resistance are connected, a second input end to which a current set voltage is applied, and an output end connected to the control end of the first transistor. The current detection unit generates a current detection signal based on a feedback voltage generated in the first node.
1. A light emitting element driving device, comprising:
an external terminal, configured to connect to a first terminal of a light emitting element;
a constant current circuit, connected to the external terminal; and
a current detection unit, configured to detect a current flowing through the constant current circuit, wherein
the current detection unit includes:
a first transistor, including a first end, a second end and a control end connected to the external terminal;
a current setting resistance, connected to the second end of the first transistor; and
a drive amplifier, including:
a first input end, connected to a first node to which the first transistor and the current setting resistance are connected;
a second input end, to which a current set voltage is applied; and
an output end, connected to the control end of the first transistor, and wherein
the current detection unit converts the current flowing through the light emitting element into a voltage signal based on a feedback voltage generated in the first node, and generates a current detection signal.
2. The light emitting element driving device of claim 1 , wherein the current detection unit includes:
a second transistor, including:
a control end, connected to the output end of the drive amplifier;
a first end, connected to the first node; and
a second end,
a first current mirror, including an input end and an output end connected to the second end of the second transistor; and
an I-V conversion resistor, connected to the output end of the first current mirror.
3. The light emitting element driving device of claim 2 , wherein a size of the second transistor is less than a size of the first transistor.
4. The light emitting element driving device of claim 1 , wherein
the current set voltage is generated based on a first reference voltage, and
the light emitting element driving device includes window comparators that compare a comparative reference voltage obtained by dividing a second reference voltage with the current detection signal.
5. The light emitting element driving device of claim 2 , wherein
the current set voltage is generated based on a first reference voltage, and
the light emitting element driving device includes window comparators that compare a comparative reference voltage obtained by dividing a second reference voltage with the current detection signal.
6. The light emitting element driving device of claim 3 , wherein
the current set voltage is generated based on a first reference voltage, and
the light emitting element driving device includes window comparators that compare a comparative reference voltage obtained by dividing a second reference voltage with the current detection signal.
7. The light emitting element driving device of claim 4 , wherein the first reference voltage and the second reference voltage are common voltages.
8. The light emitting element driving device of claim 4 , wherein in a normal condition, Vdet=αVref×0.5, in which the current detection signal is Vdet and the first reference voltage is αVref.
9. The light emitting element driving device of claim 7 , wherein in a normal condition, Vdet=αVref×0.5, in which the current detection signal is Vdet and the first reference voltage is αVref.
10. The light emitting element driving device of claim 1 , wherein
the current set voltage is generated based on a third reference voltage, and
the light emitting element driving device includes an A/D converter including an analog input end to which the current detection signal is input and a reference voltage input end to which a fourth reference voltage is input.
11. The light emitting element driving device of claim 2 , wherein
the current set voltage is generated based on a third reference voltage, and
the light emitting element driving device includes an A/D converter including an analog input end to which the current detection signal is input and a reference voltage input end to which a fourth reference voltage is input.
12. The light emitting element driving device of claim 10 , wherein the third reference voltage and the fourth reference voltage are common voltages.
13. The light emitting element driving device of claim 10 , wherein in a normal condition, Vdet=αVref×0.5, in which the current detection signal is Vdet and the third reference voltage is αVref.
14. The light emitting element driving device of claim 12 , wherein in a normal condition, Vdet=αVref×0.5, in which the current detection signal is Vdet and the third reference voltage is αVref.
15. The light emitting element driving device of claim 1 , wherein the current detection unit includes a PMOS transistor including a gate connected to the first node.
16. The light emitting element driving device of claim 1 , wherein
the light emitting element driving device includes a current setting unit that generates the current set voltage, and
the current setting unit includes:
a third transistor, including a control end, a first end, and a second end;
an error amplifier, including:
a first input end, to which a reference voltage is input;
a second input end, to which a voltage generated in a second node to which the first end of the third transistor and a first resistor are connected is input; and
an output end, connected to the control end of the third transistor
a second current mirror, including an input end and an output end connected to the second end of the third transistor; and
a second resistor, connected to the output end of the second current mirror.
17. The light emitting element driving device of claim 2 , wherein
the light emitting element driving device includes a current setting unit that generates the current set voltage, and
the current setting unit includes:
a third transistor, including a control end, a first end, and a second end;
an error amplifier, including:
a first input end, to which a reference voltage is input;
a second input end, to which a voltage generated in a second node to which the first end of the third transistor and a first resistor are connected is input; and
an output end, connected to the control end of the third transistor
a second current mirror, including an input end and an output end connected to the second end of the third transistor; and
a second resistor, connected to the output end of the second current mirror.
18. The light emitting element driving device of claim 16 , wherein the reference voltage is variable.
19. The light emitting element driving device of claim 1 , further comprising:
a DC/DC controller, controlling a generation of an output voltage supplied to the second terminal of the light emitting element based on a voltage of the external terminal; and
a protection circuit unit, performing a protection by detecting at least one of an open circuit abnormality of the external terminal and a ground abnormality of the external terminal based on the current detection signal and the output voltage.
20. The light emitting element driving device of claim 2 , further comprising:
a DC/DC controller, controlling a generation of an output voltage supplied to the second terminal of the light emitting element based on a voltage of the external terminal; and
a protection circuit unit, performing a protection by detecting at least one of an open circuit abnormality of the external terminal and a ground abnormality of the external terminal based on the current detection signal and the output voltage.