Detection of a single LED short circuit in LED strings

Abstract

Circuit diagram, including: a short-circuit detection circuit, comprising: a single short-circuit detection output element; and a selection circuit designed to receive a series load voltage from each output element of the one or more output elements and to select a series load voltage from the one or more output elements, the short-circuit detection circuit is designed as follows: to compare the selected series load voltage with a predetermined threshold voltage value, and responding to the fact that the selected series load voltage meets the predetermined threshold voltage value, the short-circuit detection circuit is designed to output a short-circuit detection signal at the single short-circuit detection output element.

Description

TECHNICAL AREA

[0001] The disclosure relates to fault detection in chains of electrical loads. BACKGROUND

[0002] US Patent 9,835,668 B2 discloses a circuit for detecting short-circuit faults in strings of LEDs. US Patent 2010 / 264,828 A1 discloses another circuit for fault detection in strings of LEDs, in which electrical potentials are compared. US Patent 9,544,971 B2 discloses yet another method for short-circuit detection in strings of LEDs.

[0003] For a circuit device that drives one or more branches with strings of electrical loads, such as a string of light-emitting diodes (LEDs), it can be useful to detect a fault in one of the loads. In the example of a load failing due to a circuit break, the current to the branch with the open circuit will cease to flow. The circuit device can detect that the current to this branch has stopped flowing and therefore detect the circuit break fault. In the example of a load failing due to a short circuit, detecting a load fault in a string of loads can be more challenging. Therefore, providing a solution for such cases is a task. SUMMARY OF THE INVENTION

[0004] To solve this problem, a circuit according to claim 1, a system according to claim 8, and a method according to claim 12 are provided. The dependent claims define further embodiments.

[0005] In general, the disclosure relates to a circuit that can detect a single short circuit in a chain of loads, such as light-emitting diodes (LEDs). The circuit can drive either multiple LED chains or a single LED chain to determine whether one or more of the LEDs in the LED chain have stopped working due to a short circuit. The circuit determines whether the LED chain voltage meets a threshold based on a single LED voltage drop. Therefore, the same circuit can be used for applications regardless of the number of LEDs in an LED chain. Additionally, according to the techniques of this disclosure, the circuit does not use any output contact pins other than those used to supply current to LED chains, regardless of the number of LED chains the circuit drives.The “fulfillment” of a threshold and the like means that a given criterion with respect to the threshold is fulfilled, in particular that the stress is greater than the threshold or less than the threshold, whereby the nature of the relation (greater or less) may depend on the signs of the stresses.

[0006] In one example, the disclosure relates to a circuit comprising a short-circuit detection circuit, comprising: a single short-circuit detection output element; and a selection circuit designed to receive a series load voltage from each output element of the one or more output elements and to select a series load voltage from the one or more output elements, wherein the short-circuit detection circuit is designed to: compare the selected series load voltage with a predetermined threshold voltage value, and responding to the fact that the selected series load voltage satisfies the predetermined threshold voltage value, the short-circuit detection circuit is designed to output a short-circuit detection signal at the single short-circuit circuit output.

[0007] In another example, the disclosure relates to a system comprising: a plurality of LED strings, wherein: each LED string in the plurality of LED strings has N LEDs in series, where N is an integer greater than one, and each of the N LEDs in an LED string has an expected forward voltage drop; a driver circuit comprising a plurality of output elements, wherein: each respective output element is coupled to a respective LED string; and the driver circuit is designed to supply a respective output current from each respective output element to each respective LED string; a selector circuit designed to select a series load voltage from a plurality of series load voltages, wherein each respective series load voltage of the plurality of series load voltages corresponds to a respective LED string of the plurality of LED strings;a comparison circuit designed to determine whether the selected series load voltage meets a predetermined threshold voltage value, and, in response to the determination that the selected series load voltage meets the predetermined threshold voltage value, to output a short-circuit detection signal.

[0008] In another example, the disclosure relates to a method comprising: supplying, through a short-circuit detection circuit and to each output element of one or more output elements of the short-circuit detection circuit, an output current to each series load coupled to each output element, wherein: each series load comprises N loads, and N is an integer greater than one; determining, through the short-circuit detection circuit, a respective series load voltage for each series load of the one or more series loads coupled to the one or more output elements; selecting, through the short-circuit detection circuit, a selected series load voltage from the one or more series load voltages; determining, through the short-circuit detection circuit, whether the selected output voltage satisfies a predetermined threshold voltage value;and responding to the determination that the selected output voltage meets the threshold voltage value, output, through the short-circuit detection circuit, a short-circuit detection signal.;

[0009] The details of one or more examples of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the disclosure will become apparent from the description, the drawings, and the claims. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1A is a schematic representation and block diagram illustrating an example of a high-side driver, a multi-channel circuit for detecting a short-circuited load in a series of loads, according to one or more techniques of this disclosure. Fig. Figure 1B is a conceptual time graph representing the operation of a short-circuit detection circuit with an attached high-side driver circuit according to one or more techniques of this disclosure. Fig. 2A is a schematic representation and block diagram illustrating an example of a low-side driver, a multi-channel circuit that drives multiple series loads of LEDs. Fig. Figure 2B is a conceptual time graph representing the operation of a short-circuit detection circuit with an attached low-side driver circuit according to one or more techniques of this disclosure. Fig. 3A is a schematic representation and block diagram illustrating an example of a high-side multi-channel driver circuit driving a single series load and which can be used to detect a short-circuited load in a series of loads according to one or more techniques of this disclosure. Fig. Figure 3B is a conceptual time graph representing the operation of a short-circuit detection circuit with an attached high-side multi-channel driver circuit driving a single LED series load, according to one or more techniques of this disclosure. Fig. Figure 4A is a schematic representation illustrating an example of a low-side driver, a multi-channel circuit that drives a single series load of LEDs. Fig. Figure 4B is a conceptual time graph illustrating the operation of a short-circuit detection circuit for an attached low-side multi-channel driver circuit supplying a single LED series load, according to one or more techniques of this disclosure. Fig. Figure 5 is a conceptual and schematic block diagram of an example of an implementation of a short-circuit detection circuit according to one or more techniques of this disclosure. Fig. Figure 6 is a flowchart illustrating an example of an operating mode of a circuit device that detects a short circuit in one load of a series of loads according to one or more techniques of this disclosure. DETAILED DESCRIPTION

[0010] The disclosure relates to a circuit capable of detecting a single short circuit in a chain of loads, such as a chain of light-emitting diodes (LEDs). The circuit can drive either multiple LED chains or a single LED chain to determine whether one or more of the LEDs in the chain have failed due to a short circuit. The circuit determines whether the LED chain voltage meets a threshold based on the voltage drop across a single LED. Therefore, the same circuit can be used regardless of the number of LEDs in the chain.

[0011] The techniques described in this disclosure are based on comparing the maximum and / or minimum voltage of LED strings with a threshold voltage. The threshold voltage can be generated internally within the circuit, for example, within an integrated circuit (IC), or it can be supplied externally. One advantage of the techniques described in this disclosure is that there are no additional or dedicated output contact pins other than those used to supply current to the LED strings. Other examples of short-circuit detection circuits may require additional and dedicated contact pins. In some examples, a dedicated short-circuit detection contact pin is required for each string of LEDs. In other words, some short-circuit detection circuits driving five strings of LEDs may require at least five additional short-circuit detection output contact pins.Other examples of LED short-circuit detection circuits may include a digital communication bus along with digital logic and registers to determine whether an LED has failed in multiple strings of LEDs. In contrast, a circuit according to the techniques of this disclosure may not employ any additional or dedicated output contact pins other than those used to supply current to LED strings. A circuit according to this disclosure may offer advantages over other detection circuits by having fewer contact pins, a smaller size, and reduced complexity.

[0012] The techniques of this disclosure can be applied to both single- and multi-channel LED drivers. A circuit according to the technique of this disclosure can provide the flexibility to use a multi-channel driver with some or all channels short-circuited together without losing the ability to detect the individual LED short circuit. For example, in some applications, the operator may short-circuit one or more of the channels of a multi-channel driver circuit together to increase the current flowing through a single string of LEDs. A multi-channel circuit according to this disclosure, where all channels are short-circuited together to drive a single LED string, can still detect a single short-circuited LED in that single LED string.A circuit according to this disclosure may offer advantages over other types of short-circuit detection circuits, including providing a model of an IC that can be used in either multi-channel or single-channel applications. The ability of a single model to serve many applications may offer advantages such as reduced inventory, reduced manufacturing costs, simplified product selection, and similar benefits.

[0013] Fig. Figure 1A is a schematic diagram and block diagram illustrating an example of a high-side driver, a multi-channel circuit for detecting a short-circuited load in a series of loads, according to one or more techniques of this disclosure. The circuit 10 may include current sources 14 to 18 to supply, at each output element of one or more output elements (34A to 34C) of the circuit, an output current (Iout1 to Iout3) to a series load (32A to 32C) coupled to each output element. The circuit 10, comprising both the circuit 10A and the current sources 14 to 18, may be considered a short-circuit detection circuit. In other examples, the circuit 10A may be considered a short-circuit detection circuit and be separate from the current source circuits, but connected to the current source outputs 34A to 34C via terminals 36A to 36C.In other words, a short-circuit detection circuit may only include circuit elements such as a selector circuit and a comparator circuit, as shown in Circuit 10A. In other examples, a short-circuit detection circuit may also include driver elements such as current sources 14 to 18, or other types of driver elements. In this disclosure, the term current driver may also be used to refer to a current source. In other words, in some examples, a short-circuit detection circuit may include sources, such as current sources, to supply the series loads. In other examples, a short-circuit detection circuit may not include sources to supply the series loads but may be coupled to the output of a source to determine the series load voltage at the output.

[0014] Power sources 14 to 18 can be any type of power source, such as a current regulator capable of supplying current. Power sources 14 to 18 receive energy from Vbat 12, as in the example of Fig. 1A is shown, but Vbat can denote any energy source, such as a regulated power supply, and is not limited to a battery. Each current source has an output element (34A to 34C). Current sources 14 to 18 supply an output current (Iout1 to Iout3) to the anode side of each series load (32A to 32C) coupled to each output element 34A to 34C. The cathode side of each series load 32A to 32C is coupled to ground.

[0015] Fig. 1A and Fig. 2A represents three series loads; however, other examples of circuits 10 and 40 may have more or fewer than three series loads. In this entire disclosure, a series load can also be referred to as a branch load, such as an LED string. In other words, the series loads 32A to 32C can be considered branch loads 32A to 32C of the multitude of loads supplied by circuits 10 or 40. Another way of describing circuits 10 or 40 is as a multi-channel circuit supplying three channels. Other examples, such as Fig. 3A and Fig. 4A, can be described below as a multi-channel circuit that supplies a single-channel or single series load.

[0016] Power source 14 is connected to series load 32A, which includes an LED 25. To simplify the figures and explanation, this diagram focuses on each load in the series as an LED. In other examples, the loads may be other types of loads, such as incandescent bulbs, power supplies, and similar loads. The other LEDs in series loads 32A to 32C are not numbered. The example of Fig. 1A represents each series load as having three LEDs, but in other examples the series load can have any number of LEDs.

[0017] Circuit 10A can be considered the short-circuit detection unit of circuit 10. The terms short-circuit detection circuit and short-circuit detection unit may be used interchangeably in this disclosure. Circuit 10A comprises a selection circuit, a minimum selector 20, a comparison circuit, a comparator 22, a threshold voltage, Vthresh 24, and an output Vflag 28. Circuit 10A can be coupled to any series load 32A to 32C via terminals 36A to 36C and receives the load voltages Vout1 to Vout3. Terminal 36A is connected to the anode side of the series load 32B and receives the load voltage Vout1, terminal 36B is connected to the anode side of the series load 32B and receives the load voltage Vout2, and terminal 32C is connected to the anode side of the series load 32C and receives the load voltage Vout3. Terminal 36B is in Fig. 1A is not marked for the sake of simplicity.

[0018] A driver circuit connected to the anode side of a series load of LEDs can be considered a high-side driver circuit. A similar example of a high-side driver circuit is shown in Fig. Figure 3A illustrates this. A driver circuit connected to the cathode side of a series load of LEDs can be considered a low-side driver circuit. Examples of low-side driver circuits are shown in Fig. 2A and Fig. 4A to be found.

[0019] The load voltages Vout1 to Vout3 depend on the series load instead of the output of the current sources 14 to 18. For example, the 32A series load has three LEDs, each with an LED voltage drop, V. LEDi The series load voltage is then the sum of the LED voltage drops, V. LEDi , according to the equation: Vload=∑i=1NVLEDi

[0020] In the example where all LED voltage drops in the series load of 32A are approximately the same, the series load voltage Vout1 for the series load of 32A is Vout1 = N × V LED = 3 × V LED , where N is an integer representing the number of loads in the series load 32A.

[0021] The selection circuit of the 10A circuit can include a minimum selector 20. A minimum selector circuit, such as the minimum selector 20, can be implemented using various techniques, including logic circuits, microprocessor circuits, and other types of circuits that may be built from discrete components, integrated circuits (ICs), or similar techniques. The minimum selector 20 receives a variety of input voltages and selects the voltage with the lowest value. For example, if each LED in the series loads is rated from 32A to 32CV, the minimum selector 20 would select the lowest voltage. LED That would mean every series load voltage would be approximately the same. In other words: Vout1=Vout2=Vout3=N×VLED=3×VLED and the output of the minimum selector 20, Vselect 38, can be approximately 3V LED In the example where LED 25 fails due to a short circuit, Vout1 = 2×V LED , and the minimum selector 20 would select the lowest voltage. Therefore: V SELECT = Vout1 = 2V LED In some examples, a selection circuit, such as the minimum selector 20, may include a voltage divider / scaler to reduce the common-mode voltage at the input of comparator 22. The voltage scaler can be applied to any output (36A to 36C) or directly to VSELECT 38. An example of this solution is shown in the conceptual schematic of Fig. 5 used below.

[0022] Circuit 10A features a comparison circuit, which in the example of Fig. In this example, comparator 22 is used. In other examples, circuit 10A may contain other types of comparator circuits. Comparator 22 receives Vselect 38 into its inverting input and compares Vselect 38 to a predetermined threshold voltage V. THRESH 24. Responding to the fact that the selected series load voltage, Vselect 38, meets the predetermined threshold voltage value V THRESH If condition 24 is fulfilled, the short-circuit detection circuit, circuit 10A, can be designed to output a short-circuit detection signal at the short-circuit detection output, which is the output of comparator 22, Vflag 28, in the example of Fig. 1A.

[0023] Other digital or analog circuits 26 can receive the short-circuit detection signal Vflag 28 from the output of circuit 10A and use Vflag to perform other functions. In some examples, the other functions may include sending a warning message or activating a warning indicator, such as an indicator light, to inform an operator that a short circuit may be present in one of the series LEDs.

[0024] Fig. Figure 1B is a conceptual timing graph representing the operation of a short-circuit detection circuit with an attached high-side driver circuit according to one or more techniques of this disclosure. The timing graph of Fig. 1B represents the operation of Fig. 1A in the example shows where LED 25 has a short circuit failure.

[0025] The time graphs of Fig. 1B includes a graph of Vout1, a combined graph of Vout2 and Vout3, a graph of Vselect 38, and a graph of Vflag 28. The LED 25 causes a short circuit in the period t0 to t1, which means that V LED25 Vout1 is approximately zero during the period t0 to t1. Vout1 is the series load voltage for the 32A series load, and in the example of... Fig. 1B all LED voltage drops have approximately the same value V LED Therefore, during the period t0 to t1, Vout1 will be approximately 3V. LED to approximately 2V LED The other series voltages, Vout2 and Vout3, remain approximately constant during the period t0 to t1.

[0026] The selection circuit, designed to receive a series load voltage Vout1 to Vout3 from each output element 34A to 34C of the one or more output elements, is the minimum selector 20. The minimum selector 20 can be configured to select the minimum series load voltage from the one or more output elements. At time t0, the minimum selector 20 selects Vout1 and outputs Vout1 as Vselect 38. Therefore, at approximately time t0, Vselect is also approximately 2 × V LED be, as in the example of Fig. 1B shown.

[0027] Vthresh 24 can be selected in the example to represent any fraction of V LED to be smaller than the expected series load for a fully functional series load. In the example of Fig. 1A and Fig. 1B is represented by Vthresh 24 as approximately: 3×VLED−0.5×VLED=(N−0.5)×VLED. In other examples, the fraction of V can be LED of ½ V LEDbe different, such as ¾, ¼ or any other fraction of V LED , which ensures that the short-circuit detection circuit detects a single short-circuited load in a series load, while avoiding a false detection indication.

[0028] In some examples, a series load might include LEDs with different voltage drops. Vthresh 24 can be set to a fraction of the minimum LED voltage drop. For example, a 32A series load might include three LEDs with voltage drops of 0.8V, 0.7V, and 0.6V, respectively. The expected series load could be the sum of V LEDi = 0.8 V + 0.7 V + 0.6 V = 2.1 V. Vthresh 24 can be set to a fraction of the 0.6 V drop minus the expected series load, such as 2.1 V - ½ × 0.6 V = 1.8 V. In this example, the short-circuit detection circuit will be designed to detect if any of the three LEDs fails due to a short circuit.

[0029] The 10A short-circuit detection circuit can be configured to compare the selected series load voltage Vselect 38 with the predetermined voltage threshold Vthresh 24, as described above. Responding to the selected series load voltage Vselect 38 meeting the predetermined threshold voltage Vthresh 24, the 10A short-circuit detection circuit can be configured to output a short-circuit detection signal Vflag 28 at the individual short-circuit detection circuit output. In the example of Fig. A high-side driver circuit, Vselect 38, satisfies the threshold Vthresh 24 if Vselect 38 is less than Vthresh 24 (Vselect < Vthresh). In some examples, the circuit may be designed for Vselect 38 to satisfy the threshold if Vselect 38 is less than or equal to Vthresh 24 (Vselect ≤ Vthresh).

[0030] At approximately time t0, Vselect 38 satisfies Vthresh 24, and comparator 22 can output the short-circuit detection signal Vflag 28. At approximately time t1, the short-circuit failure in LED 25 no longer exists, and Vout1 rises back to 3 x V LED Vselect 38 also increases to 3 x V LED and no longer meets the threshold Vthresh 24. In response to this, the comparator 22 can stop outputting the short-circuit detection signal Vflag 28 at time t1.

[0031] The circuits described in this publication offer several advantages over other types of short-circuit detection circuits. For example, they do not require additional, dedicated contact pins, as may be found in other short-circuit detection circuits that require a dedicated contact pin for each series or branch load of LEDs. In other words, no additional or dedicated contact pins are needed beyond those used to supply current to the LEDs.

[0032] In some examples, the output of comparator 22 need not be a dedicated contact pin. The output of comparator 22 can simply be a connection to the circuit or system responsible for managing the LED short circuit, such as the digital or analog circuits 26. Another advantage, as described below, is... Fig. 2A and Fig. As described in 2B, the circuits according to the techniques of this disclosure can be applied to both single- and multi-channel drivers. This provides the flexibility to use a multi-channel driver with some or all channels short-circuited together without losing the ability to detect the individual LED short circuit. For example, a customer may short-circuit some or all channels together to increase the current in a single string or series load of LEDs.

[0033] Another advantage is that the circuits, according to the techniques of this disclosure, do not require a dedicated digital communication bus. No digital information needs to be supplied by the external system, such as the number of LEDs in each series load of LEDs. Avoiding the need for a digital bus can reduce the cost and complexity of applications that can use the circuits of this disclosure.

[0034] Fig. 2A is a schematic diagram and block diagram illustrating an example of a low-side driver, a multi-channel circuit that drives multiple series loads of LEDs. The diagram in Fig. Circuit 40, shown in 2A, functions similarly to circuit 10. Fig. 1A, with the exception that current sources 14 to 18 are connected to the cathode side of the series loads 32A to 32C as low-side drivers. The reference figures in Fig. 1A and Fig. 2A, as well as the other figures in this revelation, indicate components that have the same function and performance.

[0035] Similar to circuit 10, which in relation to Fig. As described above, circuit 40 can include current sources 14 to 18 to supply or draw an output current (Iout1 to Iout3) from a series load (32A to 32C) coupled to each output element of one or more output elements (34A to 34C) of the circuit. Circuit 40, which includes both circuit 40A and current sources 14 to 18, can be considered a short-circuit detection circuit. In other examples, circuit 40A can be considered a short-circuit detection circuit and be separate from the current source circuits, but connected to the current source outputs 34A to 34C via terminals 36A to 36C.

[0036] Vbat 12 works the same as above in terms of Fig. As described in section 1A, Vbat 12 connects the anode side of each series load from 32A to 32C. Current source 14 is connected to series load 32A, which includes LED 25. Similarly, current source 16 is connected to series load 32B, and current source 18 is connected to series load 32C. Current sources 14 to 18 conduct the supplied current to ground in the example of... Fig. 2A of a low-side driver.

[0037] Circuit 40A can be considered a short-circuit detection circuit of circuit 40. Circuit 40A comprises a selection circuit, a maximum selector 30, a comparison circuit, a comparator 22, a threshold voltage, Vthresh 24, and an output Vflag 28. Circuit 40A can be coupled to any series load 32A to 32C via terminals 36A to 36C and receives the load voltages Vout1 to Vout3. Terminal 36A is connected to the cathode side of series load 32A and receives the load voltage Vout1, terminal 36B is connected to the cathode side of series load 36B and receives the load voltage Vout2, and terminal 36C is connected to the cathode side of series load 36C and receives the load voltage Vout3. Terminal 36B is in Fig. 2A is not marked to simplify the presentation.

[0038] As above for Fig. As described in 1A, the load voltages Vout1 to Vout3 depend on the series load instead of the output of the current sources 14 to 18. The selection circuit of the 40A circuit is a maximum selector 30. As with the minimum selector 20, the maximum selector 30 can be implemented using various techniques, including logic circuits, microprocessor circuits, and other types of circuits that may be constructed from discrete components, integrated circuits (ICs), or similar techniques. The maximum selector 30 receives a variety of input voltages and selects the voltage with the highest value. If each LED of the series loads 32A to 32C V LED That would mean every series load voltage would be approximately the same. In other words: Vout1=Vout2=Vout3=Vbat−N×VLED=Vbat−3×VLED and the output of the maximum selector 30, Vselect 38A, can be approximately Vbat - 3V LEDHowever, in the example where LED 25 fails due to a short circuit, the following applies: Vout1 = Vbat - 2V LED and the maximum selector 30 would select the highest voltage. Therefore: V SELECT = Vout1 = Vbat - 2V LED .

[0039] Circuit 40A includes a comparator circuit, comparator 22. In other examples, circuit 40A may include other types of comparators. Comparator 22 receives Vselect 38 at its non-inverting input and compares Vselect 38 to a predetermined threshold voltage Vbat 12 - V THRESH 24A. Responding to the fact that the selected series load voltage Vselect 38 exceeds the predetermined threshold voltage value Vbat 12 - V THRESH If the 24A requirement is met, the short-circuit detection circuit, the 40A circuit, can be designed to output a short-circuit detection signal at the short-circuit detection output, which is the output of comparator 22, Vflag 28, in the example of Fig. 1A to 4A.

[0040] Fig. Figure 2B is a conceptual timing graph representing the operation of a short-circuit detection circuit with an attached low-side driver circuit according to one or more techniques of this disclosure. The timing graph of Fig. 2B represents the operation of Fig. 2A in the example represents where LED 25 has a short circuit failure, similar to the one above. Fig. 1B.

[0041] The time graphs of Fig. 2B includes a graph of Vout1, a combined graph of Vout2 and Vout3, a graph of Vbat 12 - Vselect 38, and a graph of Vflag 28. LED 25 causes a short circuit in the period t0 to t1, which means that V LED25 Vout1 is approximately zero during the period t0 to t1. Vout1 is the series load voltage for the 32A series load, and in the examples of Fig. 1B to 4B all have approximately the same voltage drop V for the LEDs. LEDTherefore, during the period t0 to t1, Vout1 will change from approximately Vbat - 3V. LED to approximately Vbat - 2V LED increase. The other series voltages, Vout2 and Vout3, remain approximately constant during the period t0 to t1.

[0042] The selection circuit, designed to receive a series load voltage Vout1 to Vout3 from each output element 34A to 34C of the one or more output elements, is the maximum selector 30. The maximum selector 30 can be designed to select the maximum series load voltage from the one or more output elements. At time t0, the maximum selector 30 selects Vout1 and outputs Vout1 as Vselect 38. Therefore, at approximately t0, Vselect is also approximately Vbat - 2V. LED be.

[0043] Vthresh 24A in the example can be selected to represent any fraction of 2V. LED to be. In the example of Fig. 2A and Fig. 2B represents the input to the non-inverting input of comparator 22 as approximately: Vbat−Vthresh=Vbat−(3×VLED−0.5×VLED)=Vbat−2.5×VLED In other examples, the fractions of ½ V can be LED be different, such as ¾, ¼ or any other fraction of V LED , which ensures that the short-circuit detection circuit detects a single short-circuited load in a series load, while avoiding a false detection indication.

[0044] The 40A short-circuit detection circuit can be configured to compare the selected series load voltage Vselect 38 with a predetermined threshold voltage value, Vbat 12 - Vthresh 24A, as described above. Responding to the selected series load voltage Vselect 38 meeting the predetermined threshold voltage value Vbat 12 - Vthresh 24A, the short-circuit detection circuit can be configured to output a short-circuit detection signal Vflag 28 at the individual short-circuit detection circuit output. In the example of Fig. A low-side driver circuit with a current of 2A, Vselect 38, satisfies the threshold Vbat 12 - Vthresh 24A if Vselect 38 is greater than the threshold (Vselect > Vbat 12 - Vthresh 24A). In some examples, the circuit may be designed for Vselect 38 to satisfy the threshold if Vselect 38 is greater than or equal to the threshold Vbat 12 - Vthresh 24A.

[0045] At approximately time t0, Vselect 38 reaches the threshold Vbat 12 - Vthresh 24A, and comparator 22 can output the short-circuit detection signal Vflag 28. At approximately time t1, the short-circuit failure in LED 25 no longer exists, and Vout1 drops to Vbat - 3V. LED , which causes Vselect 38 to also apply to Vbat - 3V LED The value decreases. At time t1, Vselect 38 no longer meets the threshold Vbat 12 - Vthresh 24A. As a result, comparator 22 can stop outputting the short-circuit detection signal Vflag 28 at time t1.

[0046] Fig. Figure 3A is a schematic diagram and block diagram illustrating an example of a high-side multi-channel driver circuit that drives a single series load and can be used to detect a short-circuited load in a series of loads according to one or more techniques of this disclosure. The circuit 50 can include current sources 14 to 18 to supply an output current to each output element of the one or more output elements (34A to 34C) that are short-circuited together, in order to drive a series load 32A coupled to each output element. The circuit 50, which includes both the circuit 50A and the current sources 14 to 18, can be considered a short-circuit detection circuit.In other examples, the 50A circuit can be viewed as a short-circuit detection circuit and be separate from the current source circuits, but connected to the current source outputs 34A to 34C via the terminals 36A to 36C.

[0047] As with all of Fig. For currents 14 to 18, values ​​from 1A to 4A can be any current source, such as a current regulator capable of supplying current. Current sources 14 to 18 receive energy from Vbat 12, as shown in the examples of Fig. Currents from 1A to 4A are shown, but Vbat can represent any energy source, such as a regulated power supply, and is not limited to a battery. Each current source has an output element (34A to 34C). Current sources 14 to 18 are combined to produce an output current (Iout1 + Iout1 + Iout3 = 3 × I). OUTi) to supply to the anode side of the series load 32A, which is coupled to each output element 34A to 34C. The cathode side of the series load 32A is coupled to ground.

[0048] Fig. 3A and Fig. The 4A circuit described below can be viewed as a multi-channel circuit supplying a single channel or a single series load. The examples of Fig. 3a and Fig. 4A represents a three-channel driver powering a single series load. In other examples, more than three channels can power a single load. In other words, power sources 14 and 16 can be combined to power a single series load, while power source 18 can also power a dual series load. Other examples may feature any combination of channels and series loads.

[0049] Power sources 14 to 18 are connected to the 32A series load, which includes the 25A LED. The other LEDs in the 32A series load are not numbered for simplicity. The example of Fig. 3A represents the series load 32A as having three LEDs, but in other examples the series load can have any number of LEDs.

[0050] Circuit 50A can be considered a short-circuit detection circuit of circuit 50. Circuit 50A comprises a selection circuit, a minimum selector 20, a comparison circuit, a comparator 22, a threshold voltage, Vthresh 24, and an output Vflag 28. Circuit 50A can be coupled to the series load 32A via terminals 36A to 36C and receives the load voltages Vout1 to Vout3, which in the example of Fig. Terminals 3A represent a single voltage Vout. Terminals 36A to 36C are connected to the anode side of the series load 32A to detect any short-circuit failures in the high-side driver circuit 50.

[0051] The load voltage Vout1 depends on the series load instead of the output of current sources 14 to 18, as described above. All LED voltage drops in the 32A series load are approximately the same in the example of Fig. 3A, therefore the series load voltage Vout = N × V LED = 3 × V LED , where N is an integer representing the number of loads in the series load 32A.

[0052] The selection circuit of circuit 50A is a minimum selector 20, similar to the one used in Fig. Figure 1A is shown. The minimum selector 20 receives a multitude of input voltages and selects the voltage with the lowest value. In the example of circuit 50, there is only one series load voltage Vout, therefore: VSELECT = Vout. In other examples, such as the combination examples described above, the minimum selector 20 can function similarly to the function that, with respect to Fig. 1A is described. Circuit 50 represents one of the advantages of the short-circuit detection circuits according to the techniques of this disclosure. The same multi-channel short-circuit detection circuit can be used with multiple series loads or a single series load in any combination, as explained in more detail below.

[0053] The comparator 22 of circuit 50A receives Vselect 38 at its inverting input and compares it to a predetermined threshold voltage Vthresh24. Upon detecting that the selected series load voltage Vselect 38 meets the predetermined threshold voltage value Vthresh24, circuit 50A can be configured to output a short-circuit detection signal Vflag28 at the short-circuit detection output of comparator 22.

[0054] Other digital or analog circuits 26 can receive the short-circuit detection signal Vflag 28 from the output of circuit 50A and use Vflag to perform other functions. As described above, other functions can include sending a warning message or activating a warning indicator, such as an indicator light, which informs an operator that a short circuit may be present in one of the series LEDs.

[0055] Fig. Figure 3B is a conceptual timing graph representing the operation of a short-circuit detection circuit with an attached high-side multi-channel driver circuit driving a single LED series load, according to one or more techniques of this disclosure. The timing graph of Fig. 3B provides the operation of Fig. 3A in the example shows where LED 25 has a short circuit failure.

[0056] The time graphs of Fig. 3B includes a graph of Vout, a graph of Vselect 38, and a graph of Vflag 28. The LED 25 causes a short circuit in the period t0 to t1, which means that V LED25 During the period t0 to t1, the voltage is approximately zero. Vout is the series load voltage for the series load of 32A, and in the example of Fig. 3B all LED voltage drops have approximately the same value V LED Therefore, during the period t0 to t1, Vout will be approximately 3V. LED to approximately 2V LEDdecrease. Therefore, Vselect will also decrease to approximately 2V at time t0. LED reduce.

[0057] Vthresh 24 can be selected in the same way as above for Fig. 1B describes what is another advantage of the short-circuit detection circuits according to the techniques of this disclosure. The selection of Vthresh 24 depends on the knowledge of V LEDi The selection of Vthresh 24 depends on the number of LEDs in the one or multiple LED series loads. This simplifies the selection of Vthresh 24 compared to other examples of short-circuit detection circuits.

[0058] As in the examples above with the multi-channel driver circuit driving multiple series loads, the short-circuit detection circuit can be designed to compare the selected series load voltage Vselect 38 with a predetermined threshold voltage value, Vthresh 24. Responding to Vselect 38 meeting the predetermined threshold voltage value Vthresh 24, the short-circuit detection circuit can be designed to output a short-circuit detection signal Vflag 28 at the individual short-circuit detection circuit output. In the example of Fig. A high-side driver circuit with a single LED series load, Vselect 38, meets the threshold Vthresh 24 when Vselect 38 is less than Vthresh 24 (Vselect < Vthresh). In some examples, the circuit may be designed for 50A Vselect 38 to meet the threshold when Vselect 38 is less than or equal to Vthresh 24 (Vselect ≤ Vthresh).

[0059] At approximately time t0, Vselect 38 satisfies Vthresh 24, and the comparator 22 can output the short-circuit detection signal Vflag 28. At approximately time t1, the short-circuit failure in the LED 25 no longer exists, and Vout rises back to 3 × V LED Vselect 38 also increases to 3 × V LED and no longer meets the threshold Vthresh 24. In response to this, the comparator 22 can stop outputting the short-circuit detection signal Vflag 28 at time t1.

[0060] Fig. Figure 4A is a schematic diagram showing an example of a low-side driver, a multi-channel circuit, driving a single series load of LEDs. The diagram in Fig. Circuit 60, shown in 4A, functions similarly to circuit 40 from Fig. 2A. The reference numbers, which are the same as the other figures in this revelation, indicate components that have the same function and performance.

[0061] Circuit 60 can include current sources 14 to 18 to supply or draw an output current from each output element of one or more output elements (34A to 34C) that are short-circuited together, in order to drive a series load 32A coupled to each output element. Circuit 60, which includes both circuit 60A and current sources 14 to 18, can be considered a short-circuit detection circuit. In other examples, circuit 60A can be considered a short-circuit detection circuit and be separate from the current source circuits, but connected to the current source outputs 34A to 34C via terminals 36A to 36C.

[0062] Vbat 12 works the same as above in terms of Fig. 1A is described. Vbat 12 is connected to the anode side of the 32A series load. Current sources 14 to 18 are connected to the 32A series load, which includes the 25A LED. Current sources 14 to 18 discharge the supplied current to ground. The other LEDs in the 32A series load are not numbered to simplify the diagram. The example of Fig. 4A indicates the series load of 32A as having three LEDs, but in other examples the series load can include any number of LEDs.

[0063] Circuit 60A can be considered a short-circuit detection circuit of circuit 60. Circuit 60A comprises a selection circuit, a maximum selector 30, a comparison circuit, a comparator 22, a threshold voltage, Vthresh 24A, and an output Vflag 28. Circuit 60A can be coupled to the series load 32A via terminals 36A to 36C and receives the load voltages Vout1 to Vout3, which in the example of Fig. Terminals 4A represent a single voltage Vout. Terminals 36A to 36C are connected to the anode side of the series load 32A to detect short-circuit circuit failures in the low-side driver circuit 60.

[0064] As in Fig. 2B, the load voltage Vout depends on the series load instead of the output of current sources 14 to 18. All LED voltage drops in the 32A series load are approximately the same in the example of Fig. 4A, therefore the series load voltage Vout is Vout = Vbat - N × V LED = Vbat - 3V LED , where N is an integer representing the number of loads in the series load 32A.

[0065] The selection circuit of circuit 60A can include a maximum selector 30, similar to the one in Fig. 2A is shown. The maximum selector 30 receives several input voltages and selects the voltage with the highest value. In the example of circuit 60, there is only one series load voltage Vout, so that: V SELECT = Vout. In other examples, such as the combination examples described above, the maximum selector 30 can function similarly to the function that, with respect to Fig. 2A is described. Circuit 60 represents one of the advantages of the short-circuit detection circuits according to the techniques of this disclosure. The same multi-channel short-circuit detection circuit can be used with multiple series loads or a single series load in any combination, either with a high-side driver or with a low-side driver circuit.

[0066] The comparator circuit of circuit 60A, comparator 22, receives Vselect 38 into the non-inverting input and compares Vselect 38 with a predetermined threshold voltage Vbat 12 - V THRESH 24. Responding to the fact that the selected series load voltage, Vselect 38, exceeds the predetermined threshold voltage value Vbat 12 - V THRESH If condition 24 is met, the circuit can be designed to carry 60A and output a short-circuit detection signal Vflag 28 at the short-circuit detection output, at the output of comparator 22.

[0067] Other digital or analog circuits 26 can receive the short-circuit detection signal Vflag 28 from the output of circuit 60A and use Vflag to perform other functions. As described above, other functions can include sending a warning message or activating a warning indicator, such as an indicator light, which informs an operator that a short circuit may be present in one of the series LEDs.

[0068] Fig. Figure 4B is a conceptual timing graph illustrating the operation of a short-circuit detection circuit for an attached low-side multi-channel driver circuit supplying an LED series load, according to one or more techniques of this disclosure. The timing graph of Fig. 4B represents the operation of Fig. 4A in the example shows where the LED 25A has a short circuit failure.

[0069] The time graphs of Fig. 4B includes a graph of Vout, a graph of Vselect 38, and a graph of Vflag 28. The LED 25A causes a short circuit in the period t0 to t1, which means that V LED25 During the period t0 to t1, the voltage is approximately zero. Vout is the series load voltage for the series load of 32A, and in the example of Fig. 4B, and all LED voltage drops have approximately the same value, V LED Therefore, during the period t0 to t1, Vout will be approximately Vbat - 3V. LED to approximately Vbat - 2V LED reduce.

[0070] The selection circuit, designed to receive a series load voltage Vout1 to Vout3 from each output element 34A to 34C of the one or more output elements, is the maximum selector 30. The maximum selector 30 can be designed to select the maximum series load voltage from the one or more output elements. In the example of circuit 60, there is only one series load voltage Vout, so that: V SELECT = Vout. In other examples, such as the combination examples described above, the maximum selector 30 can function similarly to the function that, with respect to Fig. 2A is described. At time t0, the maximum selector outputs Vout 30 as Vselect 38. Therefore, at approximately time t0, Vselect is also approximately Vbat = 2V. LED be.

[0071] Vthresh 24 can be selected in the same way as above for Fig. Section 2B describes another advantage of short-circuit detection circuits according to the techniques of this disclosure. As in the examples above with the multi-channel driver circuit driving multiple series loads, the short-circuit detection circuit can be designed to compare the selected series load voltage Vselect 38 with the predetermined threshold voltage value, Vbat 12 - Vthresh 24A. Responding to the fact that Vselect 38 meets the predetermined threshold voltage value Vbat 12 - Vthresh 24A, the short-circuit detection circuit can be designed to output a short-circuit detection signal Vflag 28 at the individual short-circuit detection circuit output.

[0072] In the example of Fig. 4A, which is a low-side driver circuit, satisfies the threshold Vbat 12 - Vthresh 24A with Vselect 38 if Vselect 38 is greater than Vbat 12 - Vthresh 24A (Vselect > Vbat - Vthresh). In some examples, the circuit may be designed for Vselect 38 to satisfy the threshold if Vselect 38 is greater than or equal to Vthresh 24A (Vselect ≥ Vbat - Vthresh).

[0073] At approximately time t0, Vselect 38 meets the condition Vbat 12 - Vthresh 24, and comparator 22 can output the short-circuit detection signal Vflag 28. At approximately time t1, the short-circuit failure in LED 25 no longer exists, and Vout drops to Vbat - 3V. LED , which causes Vselect 38 to also be set to Vbat - 3V LED The value decreases. At time t1, Vselect 38 no longer meets the threshold Vbat 12 - Vthresh 24. As a result, the comparator 22 can stop outputting the short-circuit detection signal Vflag 28 at time t1.

[0074] Fig. Figure 5 is a conceptual and schematic block diagram of an example implementation of a short-circuit detection circuit according to one or more techniques of this disclosure. Circuit 70 can function similarly to circuits 10A and 50A and can be used with connected high-side three-channel driver circuits. This is only one example of an implementation of a short-circuit detection circuit according to the techniques of this disclosure. Other examples may have different components and component designs.

[0075] Similar to the circuits 10A and 50A described above, the short-circuit detection circuit 70 comprises a comparator 22 and a selection circuit, the minimum selector 20. Terminals OUT1 to OUT3 supply an input signal to the minimum selector 20. Terminals OUT1 to OUT3 can be correlated with terminals 36A to 36C, which are located in Fig. 1A to 4A are shown. Terminals OUT1 to OUT3 can be connected to three separate series loads, as shown. Fig. 1A and Fig. 2A is shown, with a single series load, as in Fig. 3A and Fig. 4A is shown, or with any combination of series loads. Other examples of circuit 70 may have more or fewer connections than those shown. Fig. 5 show three connections.

[0076] The output of the minimum selector 20 is connected to the inverting input of the comparator 22 via resistor 42. The inverting input of the comparator 22 is connected to ground via resistor 48. Resistor 42 and resistor 48 form a voltage divider for the inverting input of the comparator 22.

[0077] The non-inverting input of comparator 22 receives the threshold voltage setting, which correlates with Vthresh 24, as shown in Fig. Currents from 1A to 4A are shown. The current source 52 supplies a current Iref to the resistor Rref 54 through the reference voltage contact pin 56. A Zener diode 50 may be useful to provide protection in case of overvoltage. In some examples, the clamping voltage supplied by the Zener diode 50 can limit the maximum number of LEDs in a string of LEDs. An operator can select the value of the threshold voltage by choosing the value of the external resistor Rref 54. As described above, the threshold voltage can be selected as any fraction of V. LED to be, minus the expected series load for a fully functional series load. The fraction of V LED can ½ V LED , ⅓, ¼ or any other fraction of V LEDThis ensures that the short-circuit detection circuit detects a single short-circuited load in a series load while avoiding false detection indications. The external reference voltage contact pin 56 gives the operator the option to set the threshold voltage based on the application, with SLS in Fig. 5 refers to the single LED short-circuit (SLS) reference.

[0078] The output of comparator 22 can be connected to an error management circuit 32 in the example of Fig. 5. The fault management circuit 32 is connected to a control circuit 34. The fault management circuit 32 and the control circuit 34 can correlate with other digital or analog circuits 26, which are listed above. Fig. Currents from 1A to 4A are shown. Circuit example 70 has no external, additional, or dedicated contact pins to detect a short-circuit failure in a single LED of a string or chain of LEDs.

[0079] In operation, the circuit 70 can be configured to compare the selected series load voltage output from the minimum selector 20 with the predetermined threshold voltage value set by resistor Rref54, as described above. Responding to the selected series load voltage, as scaled by the voltage divider formed by resistors 42 and 48, satisfying the predetermined threshold voltage value Vthresh 24, the short-circuit detection circuit 70 can be configured to output a short-circuit detection signal similar to Vflag 28, as shown in Fig. 1A to 4A are shown. In the example of Fig. In module 5, which operates with a high-side driver circuit, the minimum selector 20 selects the minimum series load voltage. The selected voltage meets the threshold if it is less than, or less than or equal to, the predetermined threshold voltage, such as Vselect < Vthresh, as described above. Fig. 1A and Fig. 3A described. In some examples, as in Fig. For 1A to 4A, the scaling factor between the series load voltage and the input to the comparator circuit, e.g., comparator 22, is a scaling factor of 1. Other examples of Fig. 1A to 4A can also be a scaling circuit similar to the one in Fig. 5 shown.

[0080] The single short-circuit detection signal output from comparator 22 may be sufficient to indicate the status of a short-circuited LED or other load in a series load connected to terminals out1 to out3. As described above, this offers the advantage of eliminating the need for additional contact pins or complexity to detect a single short circuit among a multitude of LED series loads. Fault management circuit 32 and control circuit 34 can perform other functions in response to the short-circuit detection signal. These functions may include sending a warning message or activating a warning indicator, switching off the series load containing the short-circuited LED, activating a backup LED chain, or other similar functions.

[0081] Fig. Figure 6 is a flowchart illustrating an example of an operating mode of a circuit device that detects a short circuit in one load of a series of loads, according to one or more techniques of this disclosure. The steps of Fig. 6 are primarily with regard to Fig. 1A, Fig. 1B and Fig. The examples described in 3A may also apply to other examples.

[0082] As described above, circuits 10 and 50, which are in Fig. The circuit can be represented as 1A or 3A, and includes current sources 14 to 18 to supply an output current (Iout1 to Iout3) to each output element (32A to 32C) of one or more output elements (34A to 34C) of the circuit, to a series load (32A to 32C) coupled to each output element (90). Circuit 10 can be considered a short-circuit detection circuit and includes current sources 14 to 18. In other examples, the short-circuit detection circuit may only include circuit 10A, or 50A, which is separate from the current source circuits but may be connected to the current source outputs 34A to 34C via terminals 36A to 36C. In other words, in some examples, a short-circuit detection circuit may include sources, such as current sources, to supply the series loads. In other examples, a short-circuit detection circuit may not have sources to supply the series loads, as in the example of circuit 70, which is described in Fig. 5 is shown.

[0083] Each series load 32A to 32C can have N loads, such as N LEDs. The series loads 32A to 32C represent a series load with N = 3, but in other examples, N can be an integer greater than one. The short-circuit detection circuit can determine a respective series load voltage (Vout1 to Vout3) for each series load of the one or more series loads (32A to 32C) coupled to the one or more output elements (92). The series load voltage depends on the value of the voltage drops across each load of the N loads and on the number (N) of loads. In the example of Fig. In example 1, the series load 32B comprises three LEDs (N = 3), and each LED voltage drop can be 0.7 V. Therefore, the series load voltage for the respective series load 32B is 3 × 0.7 V = 2.1 V. In other examples, the respective series load may include one or more different types of LEDs with different voltage drops. The respective series load voltage will be the sum of the voltage drops for each LED or other type of load in the series load.

[0084] The short-circuit detection circuit can have a selector, such as the minimum selector 20 or the maximum selector 30. In the example of Fig. 1A, the minimum selector 20 can select the series load with the minimum series load voltage as the selected series load voltage among one or more series load voltages. In the example of Fig. Vout1 can be smaller than either Vout2 or Vout3 at 1A, because LED 25 can experience a short circuit failure, for example at time t0. Fig. 1B. In other words, between time t0 and time t1, Vout1 is the minimum series load voltage of the one or more load voltages. The minimum selector 20 selects Vout1 of the series load 32A as the selected series load voltage (Vselect 38) from the one or more series load voltages (94). In other examples, as above with respect to Fig. 2A and Fig. As described in section 4A, the maximum selector 30 can select the maximum load voltage as the selected series load voltage from one or more series load voltages.

[0085] Circuit 10A of circuit 10 can include a comparator 22 that can compare the selected series load voltage (Vselect 38) with a threshold voltage Vthresh 24. The comparator 22 can determine whether the selected output voltage (Vselect = Vout1) meets a predetermined threshold voltage value (Vthresh) (96). In the example of Fig. 1A Vselect 38 satisfies the predetermined threshold Vthresh 24 if Vselect 38 is less than Vthresh (Vselect < Vthresh), as in Fig. 1B is shown between times t0 and t1. In some examples, the comparator 22 may be configured to output the short-circuit detection signal Vflag (28) when Vselect 38 is less than or equal to Vthresh 24 (Vselect ≤ Vthresh). In other examples, such as in the example of Fig. 2A, Vselect 38 satisfies the predetermined threshold Vthresh if Vselect 38 is greater than Vthresh (Vselect > Vthresh).

[0086] Responding to the determination that the selected output voltage (Vselect = Vout1) meets the threshold voltage value (Vthresh), the comparator 22 of the short-circuit detection circuit can output a short-circuit detection signal Vflag 28, as described in Fig.1B shown time t0 (98). Other digital or analog circuits 26 can receive the short-circuit detection signal Vflag (28) and use Vflag to perform other functions. In some examples, the other functions may include sending a warning message or activating a warning indicator, such as an indicator light, to inform the operator that there is a short circuit in one of the LEDs of the series LEDs.

[0087] Example 1. A circuit comprising: a single short-circuit detection circuit, comprising: a single short-circuit detection output element; and a selection circuit configured to receive a series load voltage from each output element of the one or more output elements and to select a series load voltage from the one or more output elements, wherein the short-circuit detection circuit is configured to: compare the selected series load voltage with a predetermined threshold voltage value, and responding to the fact that the selected series load voltage satisfies the predetermined threshold voltage value, the short-circuit detection circuit is configured to output a short-circuit detection signal at the single short-circuit detection output element.

[0088] Example 2. The circuit according to Example 1, wherein the short-circuit detection circuit is designed to output the short-circuit detection signal during a start-up phase, and the short-circuit detection circuit is designed to output the short-circuit detection signal during an operating phase.

[0089] Example 3. The circuit according to any of Examples 1 to 2 or any combination thereof, further comprising one or more output elements, each output element being designed to supply an output current to a series load comprising N loads, where N is an integer greater than one.

[0090] Example 4. The circuit according to any combination of Examples 1 to 3, wherein the threshold voltage value is adjustable in response to operator input.

[0091] Example 5. The circuit according to any combination of Examples 1 to 4, wherein the selection circuit is a minimum selection circuit designed to determine a minimum voltage among one or more output voltages at the one or more output elements, and to select the minimum voltage as the selected output voltage.

[0092] Example 6. The circuit according to any combination of Examples 1 to 5, wherein the selection circuit is a maximum selection circuit designed to determine a maximum voltage among one or more output voltages at the one or more output elements, and to select the maximum voltage as the selected output voltage.

[0093] Example 7. The circuit according to any combination of Examples 1 to 6, wherein the short-circuit detection signal is designed to be interpreted by an external circuit as an indication that at least one of the N loads has a short-circuit fault.

[0094] Example 8. A system comprising: a plurality of light-emitting diode (LED) strings, wherein: each LED string in the plurality of LED strings has N LEDs in series, where N is an integer greater than one, and each LED of the N LEDs in an LED string has an expected forward voltage drop; a driver circuit comprising a plurality of output elements, wherein: each respective output element is coupled to a respective LED string; and the driver circuit is designed to supply a respective output current from each respective output element to each respective LED string; a selection circuit designed to select a series load voltage from a plurality of series load voltages, wherein each respective series load voltage of the plurality of series load voltages corresponds to a respective LED string of the plurality of LED strings;a comparison circuit designed to determine whether the selected series load voltage meets a predetermined threshold voltage value, and, in response to the determination that the selected series load voltage meets the predetermined threshold voltage value, to output a short-circuit detection signal.

[0095] Example 9. The system according to Example 8, wherein the threshold voltage value is set such that the comparator circuit outputs the short-circuit detection signal when a single short-circuit condition occurs under any of the N LEDs in any LED string of the plurality of LED strings.

[0096] Example 10. The system according to any combination of Examples 8 to 9, wherein: the selection circuit is a minimum selection circuit designed to determine a minimum series load voltage among the multitude of series load voltages, and to select the minimum series load voltage as the selected series load voltage; each output element of the driver circuit is designed to supply a respective output current to a respective LED string from the high side of each respective LED string.

[0097] Example 11. The system according to any combination of Examples 8 to 10, wherein: the selection circuit is a maximum selection circuit designed to determine a maximum series load voltage among the multitude of series load voltages, and to select the maximum series load voltage as the selected series load voltage; each output element of the driver circuit is designed to supply a respective output current to a respective LED string from the low side of each respective LED string.

[0098] Example 12. A method comprising: supplying, through a short-circuit detection circuit and to each output element of one or more output elements of the short-circuit detection circuit, an output current to each series load coupled to each output element, wherein: each series load comprises N loads, and N is an integer greater than one; determining, through the short-circuit detection circuit, a respective series load voltage for each series load of the one or more series loads coupled to the one or more output elements; selecting, through the short-circuit detection circuit, a selected series load voltage from the one or more series load voltages; determining, through the short-circuit detection circuit, whether the selected output voltage satisfies a predetermined threshold voltage value;and responding to the determination that the selected output voltage meets the threshold voltage value, output, through the short-circuit detection circuit, a short-circuit detection signal.;

[0099] Example 13. The method of Example 12, wherein: the short-circuit detection circuit is designed to supply the output current to each output element of the one or more output elements in a predetermined duty cycle, while the short-circuit detection circuit is in an operating mode, wherein the operating mode includes a start-up phase and an operating phase, and the short-circuit detection circuit is designed to determine whether the first output voltage satisfies a threshold voltage value at any phase of the operating mode.

[0100] Example 14. The method according to any combination of Examples 12 to 13, wherein selecting the selected series load voltage includes selecting a minimum voltage from the one or more series load voltages.

[0101] Example 15. The method according to any combination of Examples 12 to 14, wherein each output element of the short-circuit detection circuit is designed to drive each respective series load coupled to each respective output element from the high-side of each respective series load.

[0102] Example 16. The method according to any combination of Examples 12 to 15, wherein selecting the selected series load voltage includes selecting a maximum voltage from the one or more series load voltages.

[0103] Example 17. The method according to any combination of Examples 12 to 16, wherein each output element of the short-circuit detection circuit is designed to drive each respective series load coupled to each respective output element from the low-side of each respective series load.

[0104] Example 18. The method according to any combination of Examples 12 to 17, wherein each load of each series load of N loads is a light-emitting diode (LED), wherein each of the LEDs has an expected forward voltage drop, and wherein the threshold voltage value is selected such that the threshold voltage value is approximately half the expected forward voltage.

[0105] Example 19. The procedure according to any combination of Examples 12 to 18, further comprising setting the threshold voltage value in response to operator input.

[0106] Example 20. The method according to any combination of Examples 12 to 19, wherein the threshold voltage value is set such that the short-circuit detection circuit outputs the short-circuit detection signal when a single short-circuit condition occurs under any of the N loads in any of the series loads coupled to any of the output elements.

[0107] Various examples of revelation have been described. These and other examples fall within the scope of the following claims.

Claims

[1] Circuit, comprising: a short-circuit detection circuit, comprising: a single short-circuit detection output element; and a selection circuit designed to receive a series load voltage from each output element of the one or more output elements and to select a series load voltage from the one or more output elements, the short-circuit detection circuit is designed as follows: to compare the selected series load voltage with a predetermined threshold voltage value, and responding to the fact that the selected series load voltage meets the predetermined threshold voltage value, the short-circuit detection circuit is designed to output a short-circuit detection signal at the single short-circuit detection output element. [2] Circuit according to claim 1, wherein the short-circuit detection circuit is designed to output the short-circuit detection signal during a start-up phase, and the short-circuit detection circuit is designed to output the short-circuit detection signal during an operating phase. [3] Circuit according to claim 1 or 2, further comprising one or more output elements, each output element being configured to supply an output current to a series load comprising N loads, wherein N is an integer greater than one. [4] Circuit according to one of claims 1-3, wherein the threshold voltage value is adjustable in response to operator input. [5] Circuit according to one of claims 1-4, wherein the selection circuit is a minimum selection circuit designed to determine a minimum voltage from one or more output voltages at the one or more output elements and to select the minimum voltage as the selected output voltage. [6] Circuit according to one of claims 1-4, wherein the selection circuit is a maximum selection circuit designed to determine a maximum voltage from one or more output voltages at the one or more output elements, and to select the maximum voltage as the selected output voltage. [7] Circuit according to one of claims 1-6, wherein the short-circuit detection signal is designed to be interpreted by an external circuit as an indication that at least one of the N loads has a short-circuit fault. [8] System, comprehensive: a large number of light-emitting diode strings, wherein: Each LED string in the plurality of LED strings has N LEDs in series, where N is an integer greater than one, and Each of the N LEDs in a string has an expected forward voltage drop; a driver circuit comprising a multitude of output elements, wherein: Each output element is coupled to a respective string of LEDs; and The driver circuit is designed to supply a respective output current from each respective output element to each respective string of LEDs; a selection circuit designed to select a series load voltage from a plurality of series load voltages, wherein each respective series load voltage of the plurality of series load voltages corresponds to a respective LED string of the plurality of LED strings; a comparison circuit designed to: to determine whether the selected series load voltage meets a predetermined threshold voltage value, and Responding to the determination that the selected series load voltage meets the predetermined threshold voltage value, a short-circuit detection signal is output. [9] System according to claim 8, wherein the threshold voltage value is set such that the comparator circuit outputs the short-circuit detection signal when a single short-circuit condition occurs under any of the N light-emitting diodes in any light-emitting diode string of the plurality of light-emitting diode strings. [10] System according to claim 8 or 9, wherein: The selection circuit is a minimum selection circuit designed to determine a minimum series load voltage among the multitude of series load voltages, and to select the minimum series load voltage as the selected series load voltage. Each output element of the driver circuit is designed to supply a respective output current to a respective LED string from the high side of each respective LED string. [11] System according to claim 8, wherein: The selection circuit is a maximum selection circuit designed to determine a maximum series load voltage among the multitude of series load voltages, and to select the maximum series load voltage as the selected series load voltage. Each output element of the driver circuit is designed to supply a respective output current to a respective LED string from the low side of each respective LED string. [12] Procedures, including: Supply, through a short-circuit detection circuit and to each output element of one or more output elements of the short-circuit detection circuit, an output current to each series load coupled to each output element, wherein: Each series load comprises N loads, and N is an integer greater than one; Determine, by means of the short-circuit detection circuit, a respective series load voltage for a respective series load of the one or more series loads that are coupled to the one or more output elements; Selecting, by means of the short-circuit detection circuit, a selected series load voltage from one or more series load voltages; Determine, using the short-circuit detection circuit, whether the selected output voltage meets a predetermined threshold voltage value; and Responding to the determination that the selected output voltage meets the threshold voltage value, output, through the short-circuit detection circuit, a short-circuit detection signal. [13] Method according to claim 12, wherein: the short-circuit detection circuit is designed to supply the output current to each output element of the one or more output elements in a predetermined duty cycle, while the short-circuit detection circuit is in an operating mode, wherein the operating mode comprises a start-up phase and an operating phase, and The short-circuit detection circuit is designed to determine whether the first output voltage meets a threshold voltage value at any stage of the operating mode. [14] Method according to claim 12 or 13, wherein selecting the selected series load voltage comprises selecting a minimum voltage from the one or more series load voltages. [15] Method according to claim 14, wherein each output element of the short-circuit detection circuit is designed to drive each respective series load coupled to each respective output element from the high-side of each respective series load. [16] Method according to claim 12 or 13, wherein selecting the selected series load voltage comprises selecting a maximum voltage from the one or more series load voltages. [17] Method according to claim 16, wherein each output element of the short-circuit detection circuit is designed to drive each respective series load coupled to each respective output element from the low side of each respective series load. [18] Method according to any one of claims 12-17, wherein each load of each series load of N loads is a light-emitting diode (LED), wherein each of the LEDs has an expected forward voltage drop, and wherein the threshold voltage value is selected such that the threshold voltage value is approximately half the expected forward voltage. [19] Method according to one of claims 12-18, further comprising adjusting the threshold voltage value in response to operator input. [20] Method according to one of claims 12-19, wherein the threshold voltage value is set such that the short-circuit detection circuit outputs the short-circuit detection signal when a single short-circuit condition occurs under any of the N loads in any of the series loads coupled to any of the output elements.

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