Single driver circuit for driving a visible light source and an infrared light source
Systems, apparatuses, and techniques are described for driving a plurality of light sources, such as a combination of infrared and visible light sources for a camera. Example systems and apparatuses are described which may comprise a control circuit including a buck driver for providing various currents to a bridge circuit. Each branch of the bridge circuit may include a respective light source which may require a respective current to operate safely and effectively. The bridge circuit may further include a voltage divider which may couple the different branches of the bridge circuit to a feedback pin of the buck driver. Each light source may be driven by the control circuit utilizing a common buck driver. The control circuit may activate or turn on any of the light sources and/or the control circuit may deactivate or turn off all of the light sources.
1 . An electronic device comprising:
a camera;
a power supply;
a printed circuit board (PCB);
a control circuit coupled to the PCB, wherein the control circuit comprises:
a bridge circuit comprising a voltage divider; and
a buck light-emitting diode (LED) driver comprising:
a power input coupled to the power supply,
a feedback input coupled to a voltage output of the voltage divider, and
a current output coupled to a first branch and a second branch of the bridge circuit;
a visible light source comprising a visible LED coupled to the first branch of the bridge circuit between the current output of the buck LED driver and the voltage divider; and
an infrared light source comprising an infrared LED coupled to the second branch of the bridge circuit between the current output of the buck LED driver and the voltage divider.
2 . The electronic device of claim 1 , wherein the bridge circuit further comprises:
a first resistor coupled to a first node, wherein the first node is coupled to an output of the visible LED and the voltage divider;
wherein the first resistor comprises a first resistance value that limits a first current, through the visible LED, to less than or equal to a first maximum current associated with the visible LED when a feedback voltage value of the voltage divider is at a first maximum voltage value to a tolerance of within 10%;
a second resistor coupled to a second node, wherein the second node is coupled to an output of the infrared LED and the voltage divider; and
wherein the second resistor comprises a second resistance value that limits a second current value, through the infrared LED, to less than or equal to a second maximum current value associated with the infrared LED when the feedback voltage value of the voltage divider is at a second maximum voltage value to a tolerance of within 10%.
3 . The electronic device of claim 2 , wherein the voltage divider further comprises:
a third resistor comprising a third resistance value, wherein the first resistance value is less than or equal to 0.1% of the third resistance value, and wherein the first resistance value defines the first maximum current; and
a fourth resistor comprising a fourth resistance value that is equal to the third resistance value to a tolerance of within 10%, wherein the second resistance value is less than or equal to 0.1% of the fourth resistance value, and wherein the second resistance value defines the second maximum current value, wherein the feedback voltage value is measured at the voltage output of the voltage divider, wherein the voltage output of the voltage divider is coupled to a node between the third resistor and the fourth resistor.
4 . A control circuit comprising:
a bridge circuit comprising:
a voltage divider;
a first resistance coupled to a first node; and
a second resistance coupled to a second node;
a driver comprising:
a feedback input coupled to the voltage divider, and
a current output coupled to the bridge circuit;
a first light source coupled to the bridge circuit, wherein the first node is coupled to an output of the first light source and the voltage divider; and
a second light source coupled to the bridge circuit, wherein the second node is coupled to an output of the second light source and the voltage divider.
5 . The control circuit of claim 4 , wherein the first resistance limits a first current, through the first light source, to within a first maximum current associated with the first light source when a feedback voltage of the voltage divider is at a first maximum voltage to a tolerance of within 10%.
6 . The control circuit of claim 5 , wherein the second resistance limits a second current, through the second light source, to within a second maximum current associated with the second light source when the feedback voltage of the voltage divider is at a second maximum voltage to a tolerance of within 10%.
7 . The control circuit of claim 6 , wherein the voltage divider further comprises:
a third resistance, wherein the first resistance is less than or equal to 0.1% of the third resistance, and wherein the first resistance defines the first maximum current; and
a fourth resistance that is equal to the third resistance to a tolerance of within 10%, wherein the second resistance is less than or equal to 0.1% of the fourth resistance, and wherein the second resistance defines the second maximum current.
8 . The control circuit of claim 7 , wherein the voltage divider further comprises:
a feedback node that is coupled between the third resistance and the fourth resistance, wherein the feedback node is further coupled to the feedback input of the driver, and wherein a feedback voltage is determined at the feedback node.
9 . The control circuit of claim 8 , wherein the driver is configured to cause transmission, via the current output, of a current to the first light source;
wherein the current results in a first voltage at the first node between an output of the first light source and the voltage divider; and
wherein a first feedback voltage at the feedback node results in the first voltage at the first node.
10 . The control circuit of claim 9 , wherein the first voltage at the first node between the output of the first light source and the voltage divider is represented by
V
1
=
R
3
+
R
4
R
4
·
V
FB
1
;
wherein V FB1 is a first feedback voltage;
wherein R 4 is the fourth resistance of the voltage divider;
wherein R 3 is the third resistance of the voltage divider; and
wherein V 1 is the first voltage at the first node between the output of the first light source and the voltage divider.
11 . The control circuit of claim 8 , wherein the driver is configured to cause transmission, via the current output, of a current to the second light source;
wherein the current results in a second voltage at the second node between an output of the second light source and the voltage divider; and
wherein a second feedback voltage at the feedback node results in the second voltage at the second node.
12 . The control circuit of claim 11 , wherein the second voltage at the second node between an output of the second light source and the voltage divider, is represented by
V
2
=
R
3
+
R
4
R
3
·
V
FB
2
;
wherein V FB2 is the second feedback voltage;
wherein R 4 is the fourth resistance of the voltage divider;
wherein R 3 is the third resistance of the voltage divider; and
wherein V 2 is the second voltage at the second node between an output of the second light source and the voltage divider.
13 . The control circuit of claim 4 , further comprising:
a switch; and
wherein:
the bridge circuit further comprises a first transistor associated with the first light source and a second transistor associated with the second light source;
the first transistor and the second transistor are further coupled to the switch; and
the switch is configured to:
activate and deactivate, via the first transistor, the first light source; and
activate and deactivate, via the second transistor, the second light source.
14 . An electronic device comprising:
driver circuitry comprising:
a feedback input terminal, and
an output terminal; and
bridge circuit comprising:
a voltage divider,
a first branch coupled to the feedback input terminal and the output terminal, the first branch comprising a first node, a first resistor and a first light source, wherein the first resistor is coupled to the first node, wherein an output of the first light source and the voltage divider are coupled to the first node, wherein the first resistor has a first resistance that limits a current through the first light source to within a first maximum current associated with the first light source, and
a second branch coupled to the feedback input terminal and the output terminal, the second branch of circuit components comprising a second node, a second resistor and a second light source, wherein the second resistor is coupled to the second node, wherein an output of the second light source and the voltage divider are coupled to the second node, wherein the second resistor has a second resistance that limits a current through the second light source to within a second maximum current associated with the second light source.
15 . The electronic device of claim 14 , wherein the electronic device is a security camera device.
16 . The electronic device of claim 14 , wherein the electronic device is a video doorbell device.
17 . The electronic device of claim 14 ,
wherein the first resistor limits the current through the first light source when the first light source is on and the second light source is off or when a feedback voltage is at a maximum voltage to a tolerance of within 10%; and
wherein the second resistor limits the current through the second light source when the first light source is off and the second light source is on or when the feedback voltage is at the maximum voltage to a tolerance of within 10%.
18 . The electronic device of claim 17 ,
wherein the first branch of circuit components comprises a third resistor;
wherein the second branch of circuit components comprises a fourth resistor;
wherein a resistance of the first resistor is less than or equal to 0.1% of a resistance of the third resistor, and wherein the first resistor primarily determines the first maximum current; and
wherein a resistance of the second resistor is less than or equal to 0.1% of a resistance of the fourth resistor, and wherein the second resistor primarily determines the second maximum current.
19 . The electronic device of claim 18 , wherein a resistance of the third resistor is within 10% of a resistance of the fourth resistor.
20 . The electronic device of claim 17 ,
wherein the first branch of circuit components comprises a third resistor;
wherein the second branch of circuit components comprises a fourth resistor;
wherein a resistance of the first resistor is less than 1% of a resistance of the third resistor, and wherein the first resistor primarily determines the first maximum current; and
wherein a resistance of the second resistor is less than 1% of a resistance of the fourth resistor, and wherein the second resistor primarily determines the second maximum current.