ACCURATE CURRENT MONITORING OF TWO OR MORE DIFFERENT LED CHAINS

Abstract

A circuit configured to monitor current through two or more LED strings (218-318, 220-320, 430-434, 425, 530-534, 525, 618-818, 620-820), the circuit comprising: a power converter (202-802); a first current sensing resistor (206-806) arranged between a first node (212-512, 616, 712-812) and a second node (214-814) of the circuit; a second current sensing resistor (207-807) connected in series with the first current sensing resistor (206-806) and arranged between the second node (214-814) and a third node (216-516, 612, 716-816) of the circuit; a first electrical contact element at the first node (212-512, 616, 712-812) and a second electrical contact element at the third node (216-516, 612, 716-816), each coupled to the power converter (201-801); a first controllable switch (208-808); and a second controllable switch (210-810), wherein the first controllable switch (208-808) is configured to selectively connect the first LED chain (218-318, 430-434, 530-534, 618-818) to the power converter (202-801), and the second controllable switch (210-810) is configured to selectively connect the second LED chain (220-320, 425, 525, 620-820) to the power converter (202-801) such that current from the power converter (201-801) is passed in a complementary manner through the first LED chain (218-318, 430-434, 530-534, 618-818) and the second LED chain (220-320, 425, 525, 620-820), that when current flows through the first LED chain (218-318, 430-434, 530-534, 618-818), approximately zero current flows through the second LED chain (220-320, 425, 525, 620-820), and when current flows through the second LED chain (220-320, 425, 525, 620-820), approximately zero current flows through the first LED chain (218-318, 430-434, 530-534, 618-818), wherein a voltage drop between the first electrical contact element and the second electrical contact element is defined by the first current sensing resistor (206-806) when current flows through the first LED chain (218-318, 430-434, 530-534, 618-818), and wherein the voltage drop between the first electrical contact element and the second electrical contact element is defined by the first current sensing resistor (206-806) and the second current sensing resistor (207-807) when current flows through the second LED chain (220-320, 425, 525, 620-820).

Description

[0001] This disclosure relates to circuits for driving and controlling light-emitting diode chains.

[0002] Drivers are often used to control voltage, current, or power at a load. For example, a light-emitting diode (LED) driver can control the power supplied to a string of LEDs. Some drivers may include DC-DC power converters, such as a buck-boost, boost-buck, or other DC-DC converter. Such DC-DC power converters can be used to control and potentially change the power at the load based on a characteristic of the load. DC-DC power converters can be particularly useful for regulating current through LED strings.

[0003] Some LED circuits contain multiple LED strings powered by a common LED driver. In such cases, control circuitry may be useful to enable selection and control of different LED strings at different times. Accordingly, LED drivers may include a DC-DC power converter and a controller configured to control various switches that can electrically couple different LED strings to the LED driver. The switches can be used to select different LED strings at different times, and the switches can also be controlled to define duty cycles of the different LED strings to more efficiently control the power delivered to the different LED strings.

[0004] This disclosure is generally directed to a light-emitting diode (LED) circuit for driving two or more different LED strings. The LED circuit includes current monitoring capabilities configured to monitor a current through the two or more different LED strings. The circuit is designed in a manner that can reduce or eliminate excessive sense pins otherwise required for current monitoring. According to this disclosure, very accurate current monitoring can be achieved with two or more sense resistors while using only two sense pins for current monitoring through two or more different LED strings.

[0005] DE 10 2014 109 466 A1 describes a circuit for supplying power to an LED. The circuit comprises a ballast with a first terminal and several second terminals that support different current intensities. To supply power, an LED can be connected between the first terminal and one of the second terminals. The current flowing through the LED can be adjusted using a trim resistor connected between two of the second terminals.

[0006] US 10 085 314 B1 describes a circuit arrangement with two LED chains, each connected to a power supply via a selection switch.

[0007] One embodiment of the invention relates to a circuit according to claim 1. Further embodiments relate to a system according to claim 11 and a method according to claim 14.

[0008] Details of these and other examples are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims. Fig. Figure 1 is a block diagram showing a known example light-emitting diode (LED) circuit that can control and monitor current through two different complementary LED strings. Fig. Figure 2 is another block diagram showing another example LED circuit that can control and monitor current through two different complementary LED strings. Fig. Figure 3 is another block diagram showing an example LED circuit that can control and monitor current through two different complementary LED strings. Fig. Figure 4 is another block diagram showing an example LED circuit that can control and monitor current through several different complementary LED strings. Fig. Figure 5 is another block diagram showing an example LED circuit that can control and monitor current through several different complementary LED strings. Fig. Figure 6 is another block diagram showing an example LED circuit that can control and monitor current through several different complementary LED strings. Fig. Figure 7 is another block diagram showing an example LED circuit that can control and monitor current through several different complementary LED strings. Fig. Figure 8 is a block diagram showing an example LED circuit that can control and monitor current through three different complementary LED strings. Fig. Figure 9 is a flowchart consistent with techniques performed by an LED circuit configured to monitor current through two or more LED strings.

[0009] Some systems may use power converters, such as direct current (DC)-to-DC converters, to control current supplied to a light-emitting diode (LED) string. This disclosure is directed to an LED circuit for driving two or more different LED strings that can be controlled in a complementary manner. The LED circuit includes current monitoring capabilities configured to monitor current through the two or more different LED strings. The circuit is designed in a manner that may reduce or eliminate excessive sense pins otherwise required for current monitoring. For example, according to this disclosure, very accurate current monitoring may be achieved by using two or more sense resistors, while only two sense pins are used for current monitoring through the two or more different LED strings.The techniques and circuits described herein may be particularly useful in vehicle lighting applications that include multiple LED strings.

[0010] Fig. 1 is a block diagram illustrating an example system 100 including a first LED string 118 and a second LED string 120 and an LED driver 101. The LED driver 101 includes a DC / DC converter 102 configured to regulate current through the first LED string 118 and the second LED string 120. The LED driver 101 may also include a switching controller 104 configured to control switches 108 and 110 to control current flow through the first LED string 118 and the second LED string 120. In some examples, the term "LED string" refers to multiple LEDs coupled in series.

[0011] The first LED string 118 and the second LED string 120 can be controlled by controlling the switches 108 and 110 in a complementary manner. The switch controller 104 can control the switch 108 to be in an on state while controlling the switch 110 to be in an off state. Alternatively, the switch controller 104 can control the switch 108 to be in an off state while controlling the switch 110 to be in an on state. In this way, the switch controller 104 controls the LED string 118 and the second LED string 120 in a complementary manner, ensuring that both LED strings do not receive significant amounts of current at the same time.The switches 108 and 110 can be used to select different LED strings at different times, and in some cases, the switches 108 and 110 can be controlled to define duty cycles of the first LED string 118 and the second LED string 120 to more efficiently control the power supplied to the different LED strings.

[0012] As examples, each of the switches 108 and 110 may comprise a field-effect transistor (FET), a bipolar junction transistor (BJT), a gallium nitride (GaN) switch, or possibly a silicon controlled rectifier (SCR). Examples of FETs may include, but are not limited to, a junction field-effect transistor (JFET), a metal-oxide-semiconductor FET (MOSFET), a double-gate MOSFET, an insulated-gate bipolar transistor (IGBT), or any other type of FET or combination thereof. Examples of MOSFETs may include, but are not limited to, a PMOS, NMOS, DMOS, or any other type of MOSFET or combination thereof.Examples of BJTs may include, but are not limited to, a PNP, NPN, heterojunction, or any other type of BJT, or any combination thereof.

[0013] In order to monitor and detect a current flow through the first LED chain 118 and the second LED chain 120, the Fig. 1 includes a current sense resistor 106 and two current sense pins at nodes 112 and 114. The current sense pins at nodes 112 and 114 are electrical contacts coupled to the DC / DC converter 102. The DC / DC converter 102 can monitor the voltage drop from node 112 to node 114. Based on the resistor 106 and the voltage drop from node 112 to node 114, the DC / DC converter 102 can determine the current flow through the first LED string 118 and the current flow through the second LED string based on Ohm's law.

[0014] However, in many situations, the DC / DC converter 102 may be configured to supply different amounts of current to the first LED string 118 and the second LED string. The problem of supplying different amounts of current can present challenges for accurate current monitoring. For example, the DC / DC converter 102 may be configured to supply 1.5 amperes of current to the first LED string 118 (e.g., corresponding to a dimming level of 100 percent) and may also be configured to supply 0.15 amperes (corresponding to a dimming level of 10 percent) to the second LED string. In this example, the accuracy of the current measurements using the current sensing resistor 106 may vary drastically between the two configurations. When 1.5 amperes are supplied to the first LED string 118, the accuracy of the current measurement by the current sensing resistor 106 may be within approximately 3 percent.In contrast, if 0.15 amperes are supplied to the second LED string 120, the accuracy of the current measurement by the current sensing resistor 106 may be only within approximately 10 percent. This problem can be very significant if the maximum amount of current delivered to one LED string varies drastically with the minimum amount of current delivered to another, complementary LED string.

[0015] Fig. Figure 2 is another block diagram showing another example LED circuit that can control and monitor current through two different complementary LED strings. The LED system 200 of Fig. 2 is very similar in some respects to the LED system 100. The LED driver 201 may be similar to the LED driver 101. The DC / DC converter 202 is similar to the DC / DC converter 102, and the switching controller 204 is similar to the switching controller 104. The first LED string 218 may be similar to the first LED string 118, and the second LED string 220 may be similar to the second LED string 120. The switches 208 and 210 may be similar to the switches 108 and 110, and they may operate in a complementary manner, ensuring that both LED strings (208 and 210) are not on at the same time. The switches 208 and 210 can be used to select different LED strings at different times, and in some cases, the switches 208 and 210 can be controlled to control duty cycles of the first LED string 218 and the second LED string 220 to more efficiently control the power supplied to the different LED strings.

[0016] Relative to the Fig. 1 shown LED circuit can be used in Fig. 2 can achieve more accurate current sensing due to the presence of two different current sensing resistors 206 and 207. In this case, the resistances of resistors 206 and 207 can be chosen or selected during the circuit design process to provide better accuracy of current sensing measurements at different current levels. When current flows through the first LED chain 218, the DC / DC converter 202 can determine the amount of current by measuring the current through the first current sensing resistor 206 based on the voltage drop from node 212 to node 214. Nodes 212 and 214 can define external pins that provide electrical connections of the nodes back to the DC / DC converter 202.When current flows through the second LED string 220, the DC / DC converter 202 can determine the amount of current by measuring the current through the second current sense resistor 207 based on the voltage drop from node 214 to node 216, or by measuring the current through the first current sense resistor 206 and the second current sense resistor 207 based on the voltage drop from node 212 to node 216. Nodes 212, 214, and 216 all define external pins that provide electrical connections from the nodes back to the DC / DC converter 202.In any case, the DC / DC converter 202 can determine the current flow through the first LED chain 218 based on the resistance of the resistors 206 and 207 and the voltage drop between different nodes of the circuit and the current flow through the second LED chain 220 based on the resistance of the resistors 206 and 207 and the voltage drop between different nodes of the circuit based on Ohm's law.

[0017] Relative to the Fig. 1 shown LED circuit can be used in Fig. 2 can achieve more accurate current sensing due to the presence of two different current sensing resistors 206 and 207. In this case, the resistances of resistors 206 and 207 can be chosen or selected during the circuit design process to provide better accuracy of current sensing measurements at different current levels. However, the Fig. 2 has three external pins assigned to nodes 212, 214 and 216, which is more than the two pins used in the LED circuit of Fig. 1. However, the additional pin, which provides an additional electrical connection for current sensing purposes, is undesirable and increases the cost and complexity of the circuit design.

[0018] Fig. Figure 3 is another block diagram showing another example LED circuit that can control and monitor a current through various complementary LED strings. The LED system 300 of Fig. 3 is similar in some respects to the LED System 100 and the LED System 200. Like the LED System 200 of Fig. 2 uses the LED system 300 from Fig. 3 two detection resistors, which help to ensure the accuracy of the current detection relative to the LED system 100 of Fig. 1. In addition, the LED system achieves 300 of Fig. 3 a desirable two-pin configuration for the current sensing of both LED chains, which eliminates the need for the system 200 of Fig. 2 used three electrical pins (corresponding to nodes 212, 214 and 216).

[0019] The LED driver 301 may be similar to the LED driver 101 and the LED driver 201. The DC / DC converter 302 is similar to the DC / DC converter 102, and the switching controller 304 is similar to the switching controller 104. The first LED string 318 may be similar to the first LED string 118, and the second LED string 320 may be similar to the second LED string 120. The switches 308 and 310 may be similar to the switches 108 and 110, and they may operate in a complementary manner, ensuring that both LED strings (308 and 310) are never on at the same time. The switches 308 and 310 can be used to select different LED strings at different times, and in some cases, the switches 308 and 310 can be controlled to define duty cycles of the first LED string 318 and the second LED string 320 to more efficiently control the power delivered to the different LED strings.

[0020] Relative to the Fig. 1 shown LED circuit can be used in Fig. 3 can achieve more accurate current sensing due to the presence of two different current sensing resistors 306 and 307. In this case, the resistances of resistors 306 and 307 can be selected to provide better accuracy of current sensing measurements at different current levels. Nodes 312 and 316 can define external pins that provide electrical connections of the nodes back to the DC / DC converter 302. When current flows through the first LED chain 318, the DC / DC converter 302 can determine the amount of current by measuring the current through the first current sensing resistor 306 based on the voltage drop from node 312 to node 316.When current flows through the second LED string 320, the DC / DC converter 302 can determine the amount of current by measuring the current through the first current sensing resistor 306 and the second current sensing resistor 307 based on the voltage drop from node 312 to node 316. Based on the resistance of resistors 306 and 307 and the voltage drop between different nodes of the circuit, the DC / DC converter 302 can determine the current flow through the first LED string 318 and can determine the current flow through the second LED string 320 using two different resistance values (that of resistor 306 and that of the combination of resistors 306 and 307) based on Ohm's law. As shown in FIG. Fig. 3, the requirement of an additional sense pin at node 314, relative to the one shown in Fig. 2 shown circuit design, completely eliminated.

[0021] Current sense resistors 306 and 307 may be referred to as "shunt" resistors. In some cases, current sense resistors 306 and 307 represent discrete components, although in other examples, integrated resistors may be used. Typical voltage sense levels at the sense pins may range from approximately 100 mV to 150 mV for the nominal current (e.g., 100% analog dimming). In this case, current sense resistor 306 may define a resistance on the order of approximately 100 mOhm to provide a current of approximately 1.5 A through first LED string 318 (which may, for example, represent a typical "high-level" current for an LED headlight HB and LB).If both current sensing resistors 305 and 306 define resistances on the order of approximately 100 mOhm, then the total resistance would be 200 mOhm when the current flows through the second LED chain 320, in which case the current range can be reduced from 1.5 A down to 750 mA (which represents a typical "mid-level" current for a vehicle's daytime running lights (DRL).

[0022] Fig. 3 shows an example of a circuit configured to monitor current through two or more light-emitting diode strings 318 and 320. According to this disclosure, the circuit may include a power converter, such as a DC / DC converter, and a first current sensing resistor 306, wherein the first current sensing resistor 306 is positioned between a first node 312 and a second node 314 of the circuit. The circuit also includes a second current sensing resistor 307 connected in series with the first current sensing resistor 306, wherein the second current sensing resistor 307 is positioned between the second node 314 and a third node 316 of the circuit. Nodes 312 and 316 provide direct electrical connections to the DC / DC converter 302, but node 314 does not include any direct electrical connections to the DC / DC converter.Therefore, the circuit includes a first electrical contact element at the first node 312 and a second electrical contact element at the third node 316, wherein the first electrical contact element and the second electrical contact element are coupled to the power converter (e.g., the DC / DC converter 302). In . Fig. 3, current from the DC / DC converter 302 flows in a complementary manner through the first LED string 318 and the second LED string 320, such that when current flows through the first LED string 318, approximately zero current flows through the second LED string. Approximately zero current flow can refer to situations of zero current flow and situations of very small current flow due to imperfections or leakage current. Similarly, when current flows through the second LED string 320, approximately zero current flows through the first LED string 318. In some examples, approximately zero current flow can refer to current flow that is less than 5% of a nominal current used to drive a given LED string.A voltage drop between the first electrical contact element at node 312 and the second electrical contact element at node 316 is defined by the first current sensing resistor 306 when current flows through the first LED string 318. However, the voltage drop between the first electrical contact element at node 312 and the second electrical contact element at node 316 is defined by both the first current sensing resistor 306 and the second current sensing resistor 307 when current flows through the second LED string 320. Again, e.g., relative to a single resistor design such as that of . Fig. 1, by providing different resistance levels to measure two different current levels to different loads, improved current detection accuracy can be achieved. At the same time, the configuration of Fig. 3 a two-pin solution, which is one of the systems of Fig. 2 while still achieving accurate current sensing of both current levels.

[0023] The Fig. 3 may include a first controllable switch 308 that selectively couples the first LED chain 318 to the DC / DC converter 302. The circuit shown in Fig. The circuit shown in Figure 3 may further include a second controllable switch 310 that selectively couples the second LED string 320 to the DC / DC converter 302. The switch controller 304 is coupled to the DC / DC converter 302, and the switch controller 304 controls the operation of the switches 308 and 310 in the complementary manner such that when the first controllable switch 308 is controlled to be in an on state, the second controllable switch 310 is controlled to be in an off state, and when the first controllable switch 308 is controlled to be in the off state, the second controllable switch 310 is controlled to be in the on state.The switching controller 308 may also incorporate a rise time or other circuit delay to ensure that the current flow is complementary and to ensure that significant current does not flow through both switches 308 and 310 and through both LED strings 318 and 320 at the same time.

[0024] As examples, each of the switches 308 and 310 may comprise a field-effect transistor (FET), a bipolar junction transistor (BJT), a gallium nitride (GaN) switch, or possibly a silicon controlled rectifier (SCR). Examples of FETs may include, but are not limited to, a junction field-effect transistor (JFET), a metal-oxide-semiconductor FET (MOSFET), a double-gate MOSFET, an insulated-gate bipolar transistor (IGBT), or any other type of FET or combination thereof. Examples of MOSFETs may include, but are not limited to, a PMOS, NMOS, DMOS, or any other type of MOSFET or combination thereof.Examples of BJTs may include, but are not limited to, a PNP, NPN, heterojunction, or any other type of BJT, or any combination thereof.

[0025] In the example of Fig. 3, switches 308 and 310 are positioned on a high side of the LED strings. More specifically, the first controllable switch 308 is positioned on a high side of the first LED string 318 between the second node 314 of the circuit and the first LED string 318, and the second controllable switch 310 is positioned on a high side of the second LED string 320 between the third node 316 of the circuit and the second LED string 320. However, in other examples, switches 308 and 310 could be positioned on the low side. Also, although resistors 306 and 307 are illustrated as being positioned on the high side of the LED strings, the current sensing resistors could also be located on the low side.

[0026] Fig. Figure 4 is another block diagram showing another example LED circuit that can control and monitor current through two different complementary LED strings. The LED system 400 from Fig. 4 is very similar to the LED system 300 from Fig. 3. Fig. 4 is a more concrete example than that of Fig. 3. How the LED system 300 from Fig. 3 uses the LED system 400 from Fig. 4 two detection resistors, which helps to increase the current detection accuracy relative to the LED system 100 of Fig. 1. In addition, the LED system achieves 400 of Fig. 3 a desirable two-pin configuration for the current sensing of both LED chains, which eliminates the need for the system 200 of Fig. 2 used three electrical pins (corresponding to nodes 212, 214 and 216).

[0027] The LED driver 401 may be similar to the LED driver 301. The DC / DC converter 402 is similar to the DC / DC converter 302, and the switching controller 404 is somewhat similar to the switching controller 304, although the switching controller 404 controls more switches than the switching controller 304.

[0028] Switches 408 and 410 may be similar to switches 308 and 310, and they may operate in a complementary manner, ensuring that the two LED strings are never on at the same time. Switches 408 and 410 may be used to select different LED strings at different times, and in some cases, switches 408 and 410 may be controlled to define duty cycles of the LED strings to more efficiently control the power delivered to the different LED strings.

[0029] In Fig. 4, a first LED chain is shown as a chain of low beams 430, high beams 432, and corner lighting 434, which can be used as part of a vehicle lighting system. A second LED chain is shown as a chain of daytime running lights (DRLs) 425. To control and select the various lights from the first LED chain, the Fig. 4 includes additional switches 440 and 442 that can selectively couple a subset of the LEDs within the first LED string to the DC / DC converter 402. For example, the switch controller 404 can control the switches 440 and 442 based on input from a user selecting, for example, between low beam headlights 430, high beam headlights 432, and corner lighting. In the low beam configuration, LB 430 can be controlled to emit light, while in the high beam configuration, LB 430 and HB 432 can be controlled to emit light. With corner lighting in a low beam setting, LB 430 and CL 434 are controlled to emit light, and with corner lighting in a high beam setting, LB 430, HB 432, and CL 434 are all controlled to emit light. The switch controller 404 may selectively activate the switches 440 and 442 to implement these lighting settings of the first LED chain.In some cases, level shifters 405 and 409 may be used to adjust the level of the control signals supplied to the various switches.

[0030] Fig. Figure 4 represents another example of a system comprising two different LED strings and a circuit designed to supply current through the two different LED strings with the accuracy achieved with a two-resistor approach (such as that of Fig. 2) is connected, while (instead of the system of Fig. 2) uses only two pins for current sensing. According to this disclosure, a circuit may include a power converter such as the DC / DC converter 402 and a first current sensing resistor 406, wherein the first current sensing resistor 406 is positioned between a first node 412 and a second node 414 of the circuit. The circuit also includes a second current sensing resistor 407 connected in series with the first current sensing resistor 406, wherein the second current sensing resistor 407 is positioned between the second node 414 and a third node 416 of the circuit. Nodes 412 and 416 provide direct electrical connections to the DC / DC converter 402, but node 414 does not include any direct electrical connections to the DC / DC converter.Therefore, the circuit includes a first electrical contact element at the first node 412 and a second electrical contact element at the third node 416, wherein the first electrical contact element and the second electrical contact element are coupled to the power converter (e.g., the DC / DC converter 402). In . Fig. 4, current flows from the DC / DC converter 402 in a complementary manner through one or more of LB 430, HB 432, and CL 434, and flows through DLR 425, such that when current flows through one or more of LB 430, HB 432, and CL 434, approximately zero current flows through DLR 425, and vice versa. Approximately zero current flow can, in turn, refer to situations of zero current flow and situations of very low current flow due to imperfections or leakage current.

[0031] A voltage drop between the first electrical contact element at node 412 and the second electrical contact element at node 416 is defined by the first current sensing resistor 406 when current flows through one or more of LB 430, HB 432, and CL 434. However, the voltage drop between the first electrical contact element at node 412 and the second electrical contact element at node 416 is defined by both the first current sensing resistor 406 and the second current sensing resistor 407 when current flows through DLR 425. Again, by providing different resistance levels for measuring different current levels to two different loads, improved current sensing accuracy can be achieved, e.g., relative to a single resistance design such as that of Fig. 1, can be achieved. At the same time, the configuration of Fig. 4 a two-pin solution that allows one through the system of Fig. 2, while still achieving accurate current sensing of both current levels.

[0032] Fig. Figure 5 is a block diagram showing another example LED circuit that can control and monitor current through two different complementary LED strings. More specifically, Fig. 5 illustrates an LED driver 501 along with circuit elements that provide precise current monitoring of two different LED strings in a two-pin current monitoring configuration. The LED driver 501 may include an inductor circuit 524 having an inductor positioned within an H-bridge of switching elements. The DC / DC controller 502 controls two or more of the switches within the H-bridge of the inductor circuit 524 to charge or discharge energy between the inductor of the inductor circuit 524 and the capacitor 528. Elements 524, 528, and 502 represent an example of a DC / DC power converter consistent with this disclosure, although other types of power converters could be used as well.

[0033] In Fig. 5, a first LED chain is shown as a chain of low beams 530, high beams 532, and corner lights 534, which can be used for vehicle lighting. A second LED chain is shown as a chain of daytime running lights (DRLs) 525, which can also be part of a vehicle lighting system. To control and select different lights from the first LED chain, the Fig. 5 includes additional switches 540 and 542 that can selectively couple a subset of LEDs within the first LED string to the DC / DC converter (e.g., inductor circuit 524, capacitor 528, and DC / DC controller 502). Digital microcontroller 504 can control switches 508, 510, 540, and 542 based on control signals 522 from a user, e.g., input signals from a user selecting low beams 530, high beams 532, corner lights 534, and / or daytime running lights 525. In the low beam configuration, LB 530 can be controlled to emit light, while in the high beam configuration, LB 530 and HB 532 can be controlled to emit light. When corner lighting is in a low beam setting, LB 530 and CL 534 are controlled to emit light and when corner lighting is in a high beam setting, LB 530, HB 532 and CL 534 are all controlled to emit light.Digital microcontroller 504 can selectively enable switches 540 and 542 to implement these lighting settings of the first LED chain. In some cases, level shifters 504 and 509 can be used to adjust the level of control signals supplied to some of the various switches. Digital microcontroller 504 can communicate with DC / DC controller 502 via a digital interface 521, which may include a serial peripheral interface (SPI).

[0034] In some examples, such as motorcycle lighting, the first LED string (defined by LB 530, HB 532, and CL 534) may be used in a first driving mode and the second LED string (defined by DRL 525) may be used in a second driving mode, in which case the first driving mode may include a night mode and the second driving mode may include a daytime driving mode. In this type of example, DRL 525 is not active in the night mode. However, it may be desirable for DRL 525 to be used in conjunction with LB 530, HB 532, and CL 534 in the night mode. For example, DRL 525 may provide aesthetics that enhance the appearance of the vehicle lights in both day and night modes.In this case, the duty cycles of switches 508 and 510 can be defined to provide on-off switching of the first and second LED strings in a complementary manner, so that both LED strings appear active in the night mode. The on-off switching of the LEDs can occur at a frequency significantly higher than the resolution of human vision, and therefore, the illumination can appear continuous even though the lights are turning on and off at a high frequency. In some cases, the duty cycles of switches 508 and 510 can be defined or adjusted to adjust the light intensity of the first and second LED strings.

[0035] According to this disclosure, the Fig. 5 allows the DC / DC controller 502 to control and monitor current through two different complementary LED strings. Switches 508 and 510 can operate in a complementary manner, ensuring that both LED strings (the first string consisting of one or more of LB 530, HB 532, and CL 534 and the second string consisting of DRL 525) are never driven with current at the same time. Switches 508 and 510 can be used to select different LED strings at different times, and in some cases, switches 508 and 510 can be controlled to define duty cycles of the first LED string (one or more of LB 530, HB 532, and CL 534) and the second LED string (DRL 525) to more efficiently control the power supplied to the different LED strings.

[0036] Due to the presence of two different current sensing resistors 506 and 507, the Fig. 5 relative to the LED circuit shown in Fig. 1. The resistances of resistors 506 and 507 can be chosen or selected in the circuit design process to provide better precision in the sensing measurements. When current flows through the first LED chain (one or more of LB 530, HB 532, and CL 534), the DC / DC controller 502 can determine the current by measuring the current through the first current sensing resistor 506 based on the voltage drop from node 512 to node 516. Nodes 512 and 516 can define external pins that provide electrical connections of the nodes back to the DC / DC controller 502. When current flows through the second LED string (DRL 525), the DC / DC controller 502 can determine the current by measuring the current through the first current sense resistor 506 and the second current sense resistor 507 based on the voltage drop from the node 512 to the node 516.

[0037] In Fig. 5, current from the LED driver 501 flows in a complementary manner through the first LED string (one or more of LB 530, HB 532, and CL 534) and the second LED string (DRL 525), such that when current flows through the first LED string, approximately zero current flows through the second LED string. Approximately zero current flow can refer to situations with zero current flow and situations with very low current flow due to imperfections or leakage current. Similarly, when current flows through the second LED string (DRL 525), approximately zero current flows through the first LED string (one or more of LB 530, HB 532, and CL 534). A voltage drop between the first electrical contact element at node 512 and the second electrical contact element at node 516 is defined by the first current sensing resistor 506 when current flows through the first LED string (one or more of LB 530, HB 532, and CL 534).However, the voltage drop between the first electrical contact element at node 512 and the second electrical contact element at node 516 is defined by both the first current sense resistor 506 and the second current sense resistor 507 when current flows through the second LED string (DRL 525). Again, by providing different resistance levels for measuring two different current levels to two different loads, improved current sense accuracy can be achieved, e.g., relative to a single resistor design such as that of . Fig. 1, can be achieved. At the same time, the configuration of Fig. 5 a two-pin solution, which is one of the systems of Fig. 2, while still achieving accurate current sensing of the two current levels delivered to the two different LED strings.

[0038] Fig. Figure 6 is yet another example LED circuit that can control and monitor a current through two different complementary LED chains. The LED System 600 from Fig. 6 is in some respects similar to the LED system 300 from Fig. 3. How the LED system 300 from Fig. 3 uses the LED system 600 from Fig. 6 two detection resistors, which helps to increase the current detection accuracy relative to the LED system 100 of Fig. 1. In addition, the LED system achieves 600 of Fig. 3 a desirable two-pin configuration for the current measurement of both LED chains, which eliminates the need for the system 200 of Fig. 2 used three electrical pins (corresponding to nodes 212, 214 and 216).

[0039] The LED driver 601 may be similar to the LED driver 301. The DC / DC converter 602 is similar to the DC / DC converter 302, and the switching controller 604 is similar to the switching controller 304.

[0040] Switches 608 and 610 may be similar to switches 308 and 310, and they may operate in a complementary manner, ensuring that both LED strings (618 and 620) never receive significant current at the same time. Switches 608 and 610 may be used to select different LED strings at different times, and in some cases, switches 608 and 610 may be controlled to define the duty cycles of the LED strings to more efficiently control the power delivered to the different LED strings.

[0041] Fig. Figure 6 shows another example of a circuit configured to monitor current through two or more chains of LEDs 618 and 620. However, the current sensing resistors 606 and 607 are, in contrast to Fig. 3, which implements the current sensing resistors on a high side of the LED strings 318 and 320, positioned on a low side of the LED strings 618 and 620. In particular, a first current sensing resistor 606 is positioned on a low side of the first LED string 618 between the first LED string 618 and a ground node, and a second current sensing resistor 607 is positioned on a low side of the second LED string 620 between the second LED string 620 and the first LED string 618.

[0042] According to this disclosure, the circuit may include a power converter such as DC / DC converter 602 and a first current sense resistor 606, with first current sense resistor 606 positioned between a first node 616 and a second node 614 of the circuit. The circuit also includes a second current sense resistor 607 connected in series with first current sense resistor 606, with second current sense resistor 607 positioned between second node 614 and a third node 612 of the circuit. Nodes 612 and 616 provide direct electrical connections to DC / DC converter 602, but node 614 does not include any direct electrical connections to the DC / DC converter.Therefore, the circuit includes a first electrical contact element at the first node 616 and a second electrical contact element at the third node 612, wherein the first electrical contact element and the second electrical contact element are coupled to the power converter (e.g., the DC / DC converter 602). In . Fig. 6, current from the DC / DC converter 602 flows through the first LED string 618 and the second LED string 620 in a complementary manner, such that when current flows through the first LED string 618, approximately zero current flows through the second LED string 620. Again, approximately zero current flow can refer to situations of zero current flow and situations of very low current flow due to imperfections or leakage current. Similarly, when current flows through the second LED string 620, approximately zero current flows through the first LED string 618.

[0043] A voltage drop between the first electrical contact element at node 616 and the second electrical contact element at node 612 is defined by the first current sensing resistor 606 when current flows through the first LED chain 618. However, the voltage drop between the first electrical contact element at node 616 and the second electrical contact element at node 612 is defined by both the first current sensing resistor 606 and the second current sensing resistor 607 when current flows through the second LED chain 620. Again, by providing different resistance levels for measuring two different current levels to two different loads, a, e.g., relative to a single resistance design such as that of Fig. 1, improved current detection accuracy can be achieved. At the same time, the configuration of Fig. 6 a two-pin solution that allows one through the system of Fig. 2, while still achieving accurate current sensing of both current levels. In some examples, it may be more desirable to provide the current sensing resistors on the low side (as in Fig. 6), while in other examples it may be more desirable to implement the current sense resistors on the high side (as in Fig. 3 shown).

[0044] Fig. Figure 7 is yet another example LED circuit that can control and monitor a current through two different complementary LED strings. The LED system 700 from Fig. 7 is very similar to the LED system 300 from Fig. 3. How the LED system 300 from Fig. 3 uses the LED system 700 from Fig. 7 two sensing resistors, which can help to increase the current sensing accuracy relative to the LED system 100 of Fig. 1. In addition, the LED system achieves 700 of Fig. 7 a desirable two-pin configuration for the current sensing of both LED chains, which eliminates the need for the current sensing provided by the System 200 of Fig. 2 used three electrical pins (corresponding to nodes 212, 214 and 216).

[0045] The LED driver 701 may be similar to the LED driver 301. The DC / DC converter 702 is similar to the DC / DC converter 302, and the switching controller 704 is similar to the switching controller 304. The current sense resistors 706 and 707 may be similar to the current sense resistors 306 and 307.

[0046] Switches 708 and 710 may be similar to switches 308 and 310, and they may operate in a complementary manner, ensuring that both LED strings (718 and 720) never receive significant current at the same time. Switches 708 and 710 may be used to select different LED strings at different times, and in some cases, switches 708 and 710 may be controlled to define duty cycles of the LED strings to more efficiently control the power delivered to the different LED strings.

[0047] According to Fig. 7, switches 708 and 709 are positioned on a low side of the LED chains. In contrast, in the circuit configuration of Fig. 3, the switches 308 and 309 are positioned on the high side of the LED chains. In particular, according to Fig. 7, a first controllable switch 708 is positioned on a low side of the first LED chain 718 between the first LED chain and a ground node, and a second controllable switch 709 is positioned on a low side of the second LED chain 720 between the second LED chain 720 and the ground node. In some examples, it may be more desirable to position the controllable switches (as in Fig. 7) on the low-side, while in other examples it may be more desirable to have the controllable switches (as shown in Fig. 3) on the high side.

[0048] The techniques described herein can be used to monitor the current of two different LED strings, but the techniques can be extended to achieve accurate current monitoring of three or more LED strings (e.g., using three or more current sensing resistors and a two-pin sensing configuration). Fig. Figure 8 is an example LED circuit that can control and monitor current through three different complementary LED strings, but the techniques can be extended to control and monitor even more LED strings. Fig. 8 is in some respects similar to Fig. 3, but Fig. 8 contains three sense resistors, three LED chains and three controllable switches for controlling the three LED chains in a complementary manner.

[0049] Like the LED System 300 from Fig. 3 uses the LED system 800 from Fig. 8 multiple sensing resistors, which can help to increase the current sensing accuracy relative to the LED system 100 of Fig. 1. In addition, the LED system achieves 800 of Fig. 8 a desirable two-pin configuration for the current sensing of both LED chains, which eliminates the need for the current sensing provided by the System 200 of Fig. 2 used three electrical pins (corresponding to nodes 212, 214 and 216).

[0050] The LED driver 801 may be similar to the LED driver 301. The DC / DC converter 802 is similar to the DC / DC converter 302, and the switching controller 804 is similar to the switching controller 304. The current sense resistors 806 and 807 may be similar to the current sense resistors 306 and 307. Additionally, the system 800 includes a third sense resistor 809.

[0051] The switches 808 and 810 may be similar to the switches 308 and 310, and the system 800 includes a third controllable switch 811. Although they are on the low side of the LED chains 818, 820 and 822 in Fig. 8, the switches 808, 810 and 811 could alternatively be positioned on the high side of the LED chains 818, 820 and 822.

[0052] Switches 808, 810, and 811 can be controlled in a complementary manner by switching controller 804, ensuring that no two LED strings of the multiple LED strings (818, 820, and 822) receive significant current at the same time. Switches 808, 810, and 811 can be used to select different LED strings at different times, and in some cases, switches 808, 810, and 811 can be controlled to define the duty cycles of the LED strings to more efficiently control the power delivered to the different LED strings.

[0053] According to Fig. 8, the third current sensing resistor 809 is connected in series with the second current sensing resistor 807, with the third current sensing resistor 809 being positioned between the second current sensing resistor 807 and the third node 815 of the circuit. Current from the power converter (e.g., DC / DC converter 802) flows through the first LED string 818, the second LED string 820, and the third LED string 822 in a complementary manner such that when current flows through the first LED string 818, approximately zero current flows through the second LED string 820 or the third LED string 822, when current flows through the second LED string 820, approximately zero current flows through the first LED string 818 or the third LED string 822, and when current flows through the third LED string 822, approximately zero current flows through the first LED string 818 or the second LED string 820.The voltage drop between the first electrical contact element at node 812 and the second electrical contact element at node 816 is defined by the first current sensing resistor 806, the second current sensing resistor 807, and the third current sensing resistor 809 when current flows through the third LED chain 822.

[0054] Fig. Figure 9 is a flowchart consistent with techniques performed by an LED circuit configured to monitor current through two or more LED strings. Fig. 9 is viewed from the perspective of the system 300 by Fig. 3, although other systems and circuits may implement the techniques. As described in Fig. 9, the LED driver 301 supplies current through a first LED string and a second LED string 320 (901) in a complementary manner. In particular, the switching controller 304 may control switches 308 and 310 to ensure that when switch 308 is open to cause current to flow through the first LED string 318, switch 310 is controlled to be closed to cause approximately zero current to flow through the second LED string 320. And when switch 310 is open to cause current to flow through the second LED string 320, switch 308 is controlled to be closed to cause approximately zero current to flow through the first LED string 318. Of course, the circuit may accommodate current rise time and responsiveness of the switches, and small amounts of leakage current may still flow when the switches are closed.

[0055] The DC / DC converter 302 measures a first current flow through the first LED chain 318 based on a first voltage difference across the two electrical contacts at nodes 312 and 316, which is based on a voltage drop across a current sensing resistor (e.g., the first current sensing resistor 306) (902). The DC / DC converter 302 also measures a second current flow through the second LED chain 320 based on a second voltage difference across the two electrical contacts at nodes 312 and 316, which is based on a voltage drop across two different current sensing resistors (e.g., the first current sensing resistor 306 and the second current sensing resistor 308) (903). The DC / DC converter 302 may include a DC / DC controller (in Fig.3 not shown) that performs these various current sensing measurements. Based on the measurements, the DC / DC converter 302 can be configured to supply a different current intensity (904), e.g., to more appropriately drive the LED strings with the desired current level.

[0056] The following examples may illustrate one or more aspects of the disclosure.

[0057] Example 1 - A circuit configured to monitor current through two or more light-emitting diode strings, the circuit comprising: a power converter; a first current sensing resistor, the first current sensing resistor positioned between a first node and a second node of the circuit; a second current sensing resistor connected in series with the first current sensing resistor, the second current sensing resistor positioned between the second node and a third node of the circuit; and a first electrical contact element at the first node and a second electrical contact element at the third node, the first electrical contact element and the second electrical contact element coupled to the power converter;wherein current from the power converter flows through a first LED string and a second LED string in a complementary manner such that when current flows through the first LED string, approximately zero current flows through the second LED string, and when current flows through the second LED string, approximately zero current flows through the first LED string, wherein a voltage drop between the first electrical contact element and the second electrical contact element is defined by the first current sensing resistor when current flows through the first LED string, and wherein the voltage drop between the first electrical contact element and the second electrical contact element is defined by the first current sensing resistor and the second current sensing resistor when current flows through the second LED string;

[0058] Example 2 - The circuit of Example 1, further comprising: a first controllable switch, wherein the first controllable switch selectively couples the first LED string to the power converter; and a second controllable switch, wherein the second controllable switch selectively couples the second LED string to the power converter.

[0059] Example 3 - The circuit according to example 1 or 2, wherein the first switch is positioned on a high side of the first LED chain between the second node of the circuit and the first LED chain; and wherein the second controllable switch is positioned on a high side of the second LED chain between the third node of the circuit and the second LED chain.

[0060] Example 4 - Circuit according to example 1 or 2, wherein the first controllable switch is positioned on a low side of the first LED chain between the first LED chain and a ground node, and wherein the second controllable switch is positioned on a low side of the second LED chain between the second LED chain and the ground node.

[0061] Example 5 - The circuit of any one of Examples 1-4, wherein the first controllable switch and the second controllable switch are controlled in a complementary manner such that when the first controllable switch is controlled to be in an on state, the second controllable switch is controlled to be in an off state, and when the first controllable switch is controlled to be in the off state, the second controllable switch is controlled to be in the on state.

[0062] Example 6 - The circuit of any one of Examples 1-5, further comprising a switching controller configured to control the first controllable switch and the second controllable switch, wherein the switching controller is coupled to the power converter.

[0063] Example 7 - The circuit of any of Examples 1-6, further comprising: one or more additional switches configured to selectively couple a subset of LEDs within the first LED string to the power converter.

[0064] Example 8 - The circuit of any one of Examples 1-7, wherein the power converter comprises a DC-DC power converter.

[0065] Example 9 - The circuit of any one of Examples 1-8, wherein the first sense resistor is positioned on a high side of the first LED string, and wherein the second sense resistor is positioned on a high side of the second LED string.

[0066] Example 10 - The circuit of any one of Examples 1-8, wherein the first sense resistor is positioned on a low side of the first LED string between the first LED string and a ground node, and wherein the second sense resistor is positioned on a low side of the second LED string between the second LED string and the ground node.

[0067] Example 11 - The circuit of any of Examples 1-10, further comprising: a third current sensing resistor connected in series with the second current sensing resistor, the third current sensing resistor being positioned between the second current sensing resistor and the third node of the circuit, wherein current from the power converter flows through the first LED string, the second LED string, and the third LED string in a complementary manner such that when current flows through the first LED string, approximately zero current flows through the second LED string or the third LED string, when current flows through the second LED string, approximately zero current flows through the first LED string or the third LED string, and when current flows through the third LED string, approximately zero current flows through the first LED string or the second LED string, and wherein when current flows through the third LED string,the voltage drop between the first electrical contact element and the second electrical contact element is defined by the first sensing resistor, the second sensing resistor and the third sensing resistor.,

[0068] Example 12 - A system comprising: a first light-emitting diode (LED) string; a second LED string positioned in parallel with the first LED string; and a circuit configured to monitor current through the first LED string and the second LED string, the circuit comprising: a power converter; a first current sensing resistor, the first current sensing resistor positioned between a first node and a second node of the circuit; a second current sensing resistor connected in series with the first current sensing resistor, the second current sensing resistor positioned between the second node and a third node of the circuit; and a first electrical contact element at the first node and a second electrical contact element at the third node, the first electrical contact element and the second electrical contact element coupled to the power converter;wherein current from the power converter flows through the first LED string and the second LED string in a complementary manner such that when current flows through the first LED string, approximately zero current flows through the second LED string, and when current flows through the second LED string, approximately zero current flows through the first LED string, wherein a voltage drop between the first electrical contact element and the second electrical contact element is defined by the first current sensing resistor when current flows through the first LED string, and wherein the voltage drop between the first electrical contact element and the second electrical contact element is defined by the first current sensing resistor and the second current sensing resistor when current flows through the second LED string;

[0069] Example 13 - The system of example 12, wherein the system comprises a vehicle lighting system, wherein the first LED string corresponds to the vehicle headlights and the second LED string corresponds to the daytime running lamp (DRL) lighting of the vehicle.

[0070] Example 14 - The system of example 12 or 13, wherein the circuit further comprises: a first controllable switch, the first controllable switch selectively coupling the first LED string to the power converter; and a second controllable switch, the second controllable switch selectively coupling the second LED string to the power converter.

[0071] Example 15 - The system of any of Examples 12-14, wherein the first controllable switch and the second controllable switch are controlled in a complementary manner such that when the first controllable switch is controlled to be in an on state, the second controllable switch is controlled to be in an off state, and when the first controllable switch is controlled to be in the off state, the second controllable switch is controlled to be in the on state.

[0072] Example 16 - The system of any of Examples 12-15, wherein the circuit further comprises a switching controller configured to control the first controllable switch and the second controllable switch, the switching controller coupled to the power converter.

[0073] Example 17 - The system of any of Examples 12-16, further comprising: one or more additional switches configured to selectively couple a subset of LEDs within the first LED string to the power converter.

[0074] Example 18 - The system of any of Examples 12-17, wherein the system comprises a vehicle lighting system, wherein the first LED string corresponds to the vehicle's headlights and the second LED string corresponds to the vehicle's daytime running lamp (DRL) lighting, and wherein the one or more additional switches are configured to selectively control high beams, low beams, and corner lighting via different light-emitting diodes within the first LED string.

[0075] Example 19 - A method comprising: supplying a current through a first light-emitting diode (LED) string and a second LED string in a complementary manner such that when current flows through the first LED string, approximately zero current flows through the second LED string, and when current flows through the second LED string, approximately zero current flows through the first LED string; measuring a first current flow through the first LED string based on a first voltage difference between a first electrical contact and a second electrical contact, the first voltage difference based on a drop across a first current sensing resistor;and measuring a second current flow through the second LED string based on a second voltage difference between the first electrical contact and the second electrical contact, the second voltage difference being based on a voltage drop across both the first current sensing resistor and a second current sensing resistor;

[0076] Example 20 - The method of example 19, further comprising: delivering a different current through the first LED string based on the measured first current flow; and / or delivering a different current through the second LED string based on the second current flow.

Claims

[1] A circuit configured to monitor current through two or more LED strings (218-318, 220-320, 430-434, 425, 530-534, 525, 618-818, 620-820), the circuit comprising: a power converter (202-802); a first current sensing resistor (206-806) arranged between a first node (212-512, 616, 712-812) and a second node (214-814) of the circuit; a second current sensing resistor (207-807) connected in series with the first current sensing resistor (206-806) and arranged between the second node (214-814) and a third node (216-516, 612, 716-816) of the circuit; a first electrical contact element at the first node (212-512, 616, 712-812) and a second electrical contact element at the third node (216-516, 612, 716-816), each coupled to the power converter (201-801); a first controllable switch (208-808); and a second controllable switch (210-810), wherein the first controllable switch (208-808) is configured to selectively connect the first LED chain (218-318, 430-434, 530-534, 618-818) to the power converter (202-801), and the second controllable switch (210-810) is configured to selectively connect the second LED chain (220-320, 425, 525, 620-820) to the power converter (202-801) such that current from the power converter (201-801) is passed in a complementary manner through the first LED chain (218-318, 430-434, 530-534, 618-818) and the second LED chain (220-320, 425, 525, 620-820), that when current flows through the first LED chain (218-318, 430-434, 530-534, 618-818), approximately zero current flows through the second LED chain (220-320, 425, 525, 620-820), and when current flows through the second LED chain (220-320, 425, 525, 620-820), approximately zero current flows through the first LED chain (218-318, 430-434, 530-534, 618-818), wherein a voltage drop between the first electrical contact element and the second electrical contact element is defined by the first current sensing resistor (206-806) when current flows through the first LED chain (218-318, 430-434, 530-534, 618-818), and wherein the voltage drop between the first electrical contact element and the second electrical contact element is defined by the first current sensing resistor (206-806) and the second current sensing resistor (207-807) when current flows through the second LED chain (220-320, 425, 525, 620-820). [2] Circuit according to claim 1, wherein the first switch (208-508) is positioned on a high side of the first LED chain (218-318; 430-434, 530-534, 618-818) between the second node (214-514) of the circuit and the first LED chain (218-318; 430-434, 530-534, 618-818); and wherein the second controllable switch (210-510) is positioned on a high side of the second LED chain (220-320, 425, 525) between the third node (216-516) of the circuit and the second LED chain (220-320, 425, 525). [3] Circuit according to claim 1, wherein the first controllable switch (708, 808) is positioned on a low side of the first LED chain (718, 818) between the first LED chain (718, 818) and a ground node, and wherein the second controllable switch (710, 810) is positioned on a low side of the second LED chain (720, 820) between the second LED chain (720, 820) and the ground node. [4] The circuit of claim 1, wherein the first controllable switch (208-808) and the second controllable switch (210-810) are controlled in a complementary manner such that when the first controllable switch (208-808) is controlled to be in an on-state, the second controllable switch (210-810) is controlled to be in an off-state, and when the first controllable switch (208-808) is controlled to be in the off-state, the second controllable switch (210-810) is controlled to be in the on-state. [5] The circuit of any one of claims 1 to 4, further comprising a switching controller (204-804) configured to control the first controllable switch (208-808) and the second controllable switch (210-810), wherein the switching controller (204-804) is coupled to the power converter (202-802). [6] A circuit according to claim 1, further comprising: one or more additional switches (440, 442, 540, 542) configured to selectively couple a subset of LEDs (430, 432, 530, 532) within the first LED chain (430-434-434, 530-534) to the power converter (402, 502). [7] The circuit of claim 1, wherein the power converter (202-802) comprises a DC-DC power converter. [8] The circuit of any one of claims 1 to 7, wherein the first sense resistor (206-506, 706-806) is positioned on a high side of the first LED chain (218-318; 430-434, 530-534, 718-818), and wherein the second sense resistor (207-507, 707-807) is positioned on a high side of the second LED chain (220-320, 425, 525, 720-820). [9] The circuit of any one of claims 1 to 7, wherein the first sense resistor (606) is positioned on a low side of the first LED chain (618) between the first LED chain (618) and a ground node (616), and wherein the second sense resistor (607) is positioned on a low side of the second LED chain (620) between the second LED chain (620) and the ground node (616). [10] Circuit according to one of claims 1 to 9, further comprising: a third current sensing resistor (809) connected in series with the second current sensing resistor (807), the third current sensing resistor (809) being positioned between the second current sensing resistor (807) and the third node (816) of the circuit, wherein current from the power converter (802) flows in a complementary manner through the first LED chain (818), the second LED chain (820), and the third LED chain (822), such that when current flows through the first LED chain (818), approximately zero current flows through the second LED chain (820) or the third LED chain (822), when current flows through the second LED chain (820), approximately zero current flows through the first LED chain (818) or the third LED chain (822), and when current flows through the third LED chain (822), approximately zero current flows through the first LED chain (818) or the second LED chain (820), and wherein, when current flows through the third LED chain (822), the voltage drop between the first electrical contact element and the second electrical contact element is defined by the first sensing resistor (806), the second sensing resistor (807) and the third sensing resistor (809). [11] System that has: a first light-emitting diode (LED) chain (218-318; 430-434, 530-534, 618-818); a second LED chain (220-320, 425, 525, 620-820) positioned parallel to the first LED chain (218-318; 430-434, 530-534, 618-818); and a circuit (200-800) according to any one of claims 1 to 10, which is configured to monitor current through the first LED chain (218-318; 430-434, 530-534, 618-818) and the second LED chain (220-320, 425, 525, 620-820). [12] The system of claim 11, wherein the system comprises a vehicle lighting system, wherein the first LED string (218-318; 430-434, 530-534, 618-818) corresponds to the vehicle headlights and the second LED string (208-808) corresponds to the daytime running lamp (DRL) lighting of the vehicle. [13] The system of claim 12, wherein one or more additional switches (440, 442, 540, 542) of the circuit (400, 500) are configured to selectively control high beams, low beams, corner lighting via different light emitting diodes within the first LED chain (430-434, 530-534). [14] Method comprising: Supplying a current through a first light-emitting diode (LED) chain (218-318; 430-434, 530-534, 618-818) through a first controllable switch (208-808) and a second LED chain (220-320, 425, 525, 620-820) through a second controllable switch (210-810) in a complementary manner such that when current flows through the first LED chain (218-318; 430-434, 530-534, 618-818), approximately zero current flows through the second LED chain (220-320, 425, 525, 620-820), and when current flows through the second LED chain (220-320, 425, 525, 620-820), approximately zero current flows through the first LED chain (218-318; 430-434, 530-534, 618-818); Measuring a first current flow through the first LED chain (218-318; 430-434, 530-534, 618-818) based on a first voltage difference between a first electrical contact and a second electrical contact, the first voltage difference being based on a drop across a first current sensing resistor (206-806); and Measuring a second current flow through the second LED chain (220-320, 425, 525, 620-820) based on a second voltage difference between the first electrical contact and the second electrical contact, wherein the second voltage difference is based on a voltage drop across both the first current sensing resistor (206-806) and a second current sensing resistor (207-807). [15] The method of claim 14, further comprising: Supplying a different current through the first LED chain (218-318; 430-434, 530-534, 618-818) based on the measured first current flow; and / or Delivering a different current through the second LED chain (220-320, 425, 525, 620-820) based on the second current flow.

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