Control circuit and method for controlling a downshifter and downshifter system

Abstract

Control circuit for a buck converter configured to supply a set of light-emitting diodes (LEDs) (106), wherein the control circuit (110; 210; 510) is configured to: to control a switching element (112) in order to establish, for a current switching period during an on-state, a channel which electrically couples a source (102) with an inductive element (116) of the buck converter; in response to the activation of the switching element (112) to establish the channel, to generate a minimum current reading at the switching element (112) that corresponds to the measured current; as a reaction to the fact that the current at the switching element (112) exceeds a target peak current threshold of a set of control parameters for the buck converter: to control the switching element (112) in order to prevent the establishment of the channel that electrically couples the source to the inductive element (116) for the current switching period during an off state; to generate a peak current reading that corresponds to the measured current at the switching element (112); to calculate an average current using the minimum current reading and the peak current reading; and to change the set of control parameters for the buck converter using the average current; and in response to the fact that the switching element (112) fulfills an off-time of the set of control parameters for the current switching period during the off-state, the switching element (112) is controlled in order to establish the channel that electrically couples the source (102) to the inductive element (116) for a subsequent switching period during an on-state.

Description

[0001] This disclosure relates to electrical power converters, in particular buck converters.

[0002] DC / DC converters, including buck converters, can be used to drive loads with specific current and / or voltage requirements, such as strings of one or more light-emitting diodes (LEDs). The light intensity of an LED string is controlled by the current flowing through it. Generally, a closed-loop current generator can be used to maintain a constant current. For lighting applications with high current loads, switched-mode controllers can be used. In some applications, such as automotive lighting, a DC / DC buck converter topology can be employed.

[0003] US Patent 2013 / 0162165 A1 discloses an LED driver for powering an LED light. The LED driver comprises a switched power supply for powering the LED light and a control unit for controlling a switch in the switched power supply. The control unit includes an input terminal for receiving a setpoint representing a desired output characteristic of the LED light. The control unit is further configured to periodically determine an off and an on time of the switch, to estimate the average current based on at least one measurement of the current to the LED light, and to use the estimated average current as a feedback signal representing the average current for controlling the LED current.

[0004] German patent application DE 10 2015 223 723 A1 describes a switching regulator for controlling an LED string. The switching regulator comprises a control circuit designed to operate the regulator in a limiting mode by controlling a switch coupled to an inductor when the load formed by the LED string is so high that the resulting switch-off threshold exceeds a predetermined minimum value; and in a discontinuous mode with the minimum value of the switch-off threshold when the load formed by the LED string is so low that the switch-off threshold resulting in limiting mode would be below the predetermined minimum value. A signal representing the current is supplied to the control circuit in both limiting and discontinuous modes without being externally averaged.

[0005] The KR 100682394 B1 describes a current regulator for an LED lamp and an LED lighting device with this regulator.

[0006] This disclosure is generally directed to controlling an average current flowing through a set of light-emitting diodes (LEDs). For example, a control circuit for a buck converter can calculate an average current using a minimum current measurement and a peak current measurement. In this example, the control circuit can drive the buck converter to supply an average current to the set of LEDs without directly measuring current at the LEDs. In this way, the control circuit can omit a pin that would otherwise be used to measure current at the LEDs, which can reduce the cost of the resulting circuit.

[0007] One embodiment of the invention relates to a control circuit according to claim 1 for controlling a step-down plate.

[0008] Another embodiment of the invention relates to a method according to claim 14 for controlling a drop-down plate.

[0009] Another embodiment of the invention relates to a buck converter system according to claim 20.

[0010] Details of these and other examples are set forth in the accompanying drawings and the description below. Other features, items, and advantages are apparent from the description, the drawings, and the claims. Fig. Figure 1 is a block diagram illustrating an example system trained for power converter control using a calculated average current, according to one or more techniques of this disclosure. Fig. Figure 2 is a conceptual representation illustrating an example control circuit trained to modify an off-time according to one or more techniques of this revelation. Fig. Figure 3 is a graphical representation of the initial behavior of the example control circuit from Fig. 2 according to one or more techniques of this revelation. Fig. Figure 4 is a graphical representation of a second behavior of the example control circuit from Fig. 2 according to one or more techniques of this revelation. Fig. Figure 5 is a conceptual representation illustrating an example control circuit trained to change a target peak current threshold according to one or more techniques of this disclosure. Fig. Figure 6 is a flowchart consistent with techniques for controlling a buck converter using a calculated average current, according to this disclosure.

[0011] In some applications, light-emitting diode (LED) applications can utilize a set of LEDs that operate at a common voltage lower than a supply voltage. Such LED applications can be useful in automotive lighting or other environments. Automotive lighting, for example, can include illuminating instruments or controls, as well as automotive front lighting (e.g., high beam, low beam, directional lighting, object detection-based lighting, or other lighting techniques). For instance, an application might use a single high-brightness LED that operates at a voltage lower than a minimum supply voltage from a battery. In such applications, a direct current (DC)-DC buck converter can be used as the LED driver.For example, there might be no need to increase the voltage because the set of LEDs can operate with a supply voltage of less than 4 volts, while a battery supply can provide a voltage of more than 6 volts. In other examples, the supply voltage and / or the LED operating voltage may differ.

[0012] In some systems, a buck converter control circuit can employ a controlled off-time ("Toff") topology to control an average current output to the set of LEDs. In such systems, the control circuit can continuously measure the current across the LEDs using a sense resistor placed in series with the LEDs or between a diode and an inductor in the buck converter circuit. In these systems, the resistor can be located outside the chip (e.g., the integrated circuit (IC)) implementing the control circuit. Therefore, an Rsense pin is included on the IC and its associated printed circuit board (PCB), with at least one additional pad and metal trace for measuring the voltage drop across the Rsense pin.

[0013] Instead of relying on a sensing resistor located outside an IC that implements the control circuitry, a control circuit can use an internal current measurement (e.g., on the chip). This eliminates the need for the Rsense pin on the IC, and an associated PCB can omit the additional pad and metal trace, reducing PCB space and the cost of the IC, PCB, and resulting control circuitry.

[0014] Furthermore, instead of using continuously measured current values ​​across an external sensing resistor, the control circuit can be configured to use two or more current measurements to calculate the average load current across the set of LEDs. For example, the control circuit can generate a first current measurement during a turn-on phase when a minimum current across the buck converter inductor is reached (e.g., using an analog-to-digital converter (ADC), storing it in a capacitor, etc.). In this example, the control circuit can generate a second current measurement when a peak current across the buck converter inductor is reached. The control circuit can then calculate (e.g., extrapolate) the average current across the set of LEDs using these two or more measurements.

[0015] The control circuit can control the buck converter such that the average current across the set of LEDs corresponds to a setpoint for the average current across the set of LEDs (e.g., is equal to, proportional to, etc.). For example, the control circuit can dynamically change an off-time value used to determine when the buck converter's turn-on phase begins, thus minimizing any difference between the average current and the setpoint for the average current. In some examples, the control circuit can dynamically change a setpoint peak current threshold used to determine when the buck converter's turn-off phase begins, thus minimizing any difference between the average current and the setpoint for the average current.

[0016] A control circuit designed to use an internal current sensing signal can integrate more components on the chip (e.g., within a single IC), which can reduce costs compared to control circuits using an external sensing resistor. Furthermore, systems using an internal sensing signal can detect current between a high-side switching element (e.g., DMOS) and a diode, so that current is measured only during the on-phase of the high-side switching element. This can reduce power consumption compared to systems that measure current during both the on-phase and off-phase of the high-side switching element.

[0017] Fig. Figure 1 is a block diagram illustrating an example system 100 configured for power converter control using a calculated average current, according to one or more techniques of this disclosure. As in the example of Fig. As shown in Figure 1, the system 100 can include a power supply 102, a buck converter 104, a set of LEDs 106 (hereinafter "LEDs"), a control circuit 110, a switching element 112, and a current sensor 114. As shown, the buck converter 104 includes an inductive element 116 and a diode 118. In some examples, the diode 118 may instead include a switching element configured for active rectification. As shown in the buck converter circuit diagram, an output capacitor can be omitted to drive an LED in a current-driven mode.

[0018] The supply 102 may be configured to supply electrical power to one or more other components of the system 100. For example, the supply 102 may be configured to supply power to the LEDs 106. In some examples, the supply 102 includes a battery, which may be configured to store electrical energy. Examples of batteries may include, but are not limited to, nickel-cadmium, lead-acid, nickel-metal hydride, nickel-zinc, silver oxide, lithium-ion, lithium polymer, or any other type of rechargeable battery, or any combination thereof. In some examples, the supply 102 may include an output of a linear voltage regulator, a power converter, or a power inverter. For example, the supply 102 may include an output of a DC-DC power converter, an AC-DC power converter, and the like.In some examples, supply 102 can represent a connection to an electrical power supply network. In some examples, the input power signal supplied by supply 102 can be a DC input power signal. For example, in some examples, supply 102 can be configured to provide a DC input power signal in the range of ~5 V. DC up to ~40 V DC to supply. In some examples, supply 102 can output a voltage between 6 volts and 16 volts.

[0019] The LEDs 106 can refer to any suitable semiconductor light source. In some examples, the LEDs 106 include a pn junction configured to emit light when activated. In one exemplary application, the LEDs 106 are included in a head light assembly for automotive applications. For example, the LEDs 106 may be a matrix of LEDs used to illuminate a road ahead of a vehicle. The term "vehicle," as used herein, may refer to trucks, boats, golf carts, snowmobiles, sweepers, or any other vehicle that uses directional lighting. In some examples, the LEDs 106 may include one or two LEDs.

[0020] The current sensor 114 may contain an internal resistor that generates a voltage corresponding to the current flowing through that resistor. In some examples, the current sensor 114 may incorporate a Hall effect sensor, a clamp meter, or another type of current sensor.

[0021] The switching element 112 can be used to construct a channel that electrically couples the supply 102 to the inductive element 116. Examples of switching elements include, but are not limited to, a thyristor (silicon-controlled rectifier; SCR), a field-effect transistor (FET), and a bipolar junction transistor (BJT). Examples of FETs include, but are not limited to, a junction field-effect transistor (JFET), a metal-oxide-semiconductor FET (MOSFET), a dual-gate MOSFET, an insulated-gate bipolar transistor (IGBT), or any other type of FET or any combination thereof.Examples of MOSFETs may include, but are not limited to, a p-channel depletion-type MOSFET (PMOS), an enhancement-type PMOS, an n-channel depletion-type MOSFET (NMOS), an enhancement-type NMOS, a double-diffused MOSFET (DMOS), or any other type of MOSFET, or any combination thereof. Examples of BJTs may include, but are not limited to, PNP, NPN, or any other type of BJT, or any combination thereof. The switching elements may be high-side or low-side. Additionally, the switching elements may be voltage-controlled and / or current-controlled. Examples of current-controlled switching elements may include, but are not limited to, gallium nitride (GaN) MOSFETs, BJTs, or other current-controlled elements.

[0022] The control circuit 110 can be configured to control the switching element 112 such that the average current across the LEDs 106 corresponds to a setpoint of the average current (e.g., is equal to, proportional to, etc.). In some examples, the control circuit 110 can switch the switching element 112 so that the buck converter 104 outputs a voltage between 3 volts and 4 volts to the LEDs 106.

[0023] The control circuit 110 can include a microcontroller on a single integrated circuit containing a processor core, memory, inputs, and outputs. For example, the control circuit 110 can include one or more processors, including one or more microprocessors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or any other equivalent integrated or discrete logic circuit, as well as any combination of such components. The term "processor" or "processing circuit" can generally refer to any preceding logic circuit alone or in combination with other logic circuits, or any other equivalent circuit. The control circuit 110 can represent a combination of one or more analog components and one or more digital components.

[0024] In the example of Fig. In this example, the supply 102 has a positive node and a reference node (e.g., ground, a local ground rail, or another reference node). The current sensor 114 is arranged in an integrated circuit with the switching element 112, and the current sensor 114 is configured to output an indication of a current measured at the switching element 112. As shown, the switching element 102 has a control node coupled to the control circuit 110, a first node coupled to the positive supply 102, and a second node. In this example, the buck converter 104 has a diode 118 with an anode coupled to the reference node of the supply 102 and a cathode coupled to the second node of the switching element 112. As shown, the inductive element 116 has a first node coupled to the second node of the switching element 112 and a second node coupled to the LEDs 106.

[0025] According to one or more of the described techniques, the control circuit 110 can be configured to drive the switching element 112 to establish, for a current switching period during an on-state, a channel that electrically couples the supply 102 to the inductive element 116 of the buck converter 104. In response to the driving of the switching element 112 to establish the channel, the control circuit 110 can be configured to generate a minimum current reading corresponding to the current measured at the switching element 112.In response to the current at the switching element 112 exceeding a target peak current threshold of a set of control parameters for the buck converter 104, the control circuit 110 can be configured to control the switching element 112 to refrain from building up the channel that electrically couples the supply 102 to the inductive element 116 for the current switching period during an off state, to generate a peak current measurement corresponding to the measured current at the switching element 112, to calculate an average current using the minimum current measurement and the peak current measurement, and to change the set of control parameters for the buck converter 104 using the average current.In response to the fact that the switching element 112 fulfills an off-time of the set of control parameters for the current switching period during the off-state, the control circuit 110 can be configured to control the switching element 112 in order to establish, for a subsequent switching period during an on-state, the channel that electrically couples the supply 102 to the inductive element 116.

[0026] Fig. Figure 2 is a conceptual representation illustrating an example control circuit 210 according to one or more techniques of this disclosure, which is configured to modify an off-time. The control circuit 210 can be compared to the control circuit 110 of the disclosure in Fig. 1 of the system shown corresponds to 100. In the example of Fig. In Figure 2, the control circuit 210 comprises a current sensor 214, a register 219, a comparator 220, a clock generator 222, a set-reset (SR) latch 224, a register 226, an averaging calculator 228, an error module 230, and an adder 232. In the example of Fig. 2. The control circuit 210 modifies the off-time of a set of control parameters for a buck converter. Additionally or alternatively, the control circuit can modify other parameters of the set of control parameters for a buck converter, for example, but not limited to, a target peak current threshold value (see Fig. 5), change.

[0027] In the example of Fig. 2 the current sensor 214 is designed to provide an indication of the measured current at the switching element 112 of Fig. The comparator 220 is configured to output a reset signal when the indication of the measured current at the switching element 112 exceeds a target peak current threshold. The clock generator 222 is configured to output a set signal when the switching element 112 completes an off-time, and the clock generator is initialized in response to the reset signal. The clock generator 222 can determine that an off-time has been completed for the current switching period during the off-state if a count value of the clock generator 222, which is set to zero by the reset signal output by the comparator 220, exceeds the off-time.

[0028] The SR-Latch 224 is configured to reset itself in response to the reset signal and to set itself in response to the set signal. The SR-Latch 224 can output a gate-driving signal to control the switching element 112 to establish a channel when the SR-Latch 224 is set, and to control the switching element 112 to refrain from establishing a channel when the SR-Latch 224 is reset.

[0029] Register 219 is configured to store a peak current measurement in response to the measured current at switching element 112 exceeding a set peak current threshold. For example, register 219 can be configured to store the peak current measurement in response to the reset signal. Register 226 is configured to store the minimum current measurement in response to the set signal.

[0030] The average current calculator 228 is configured to receive the peak current measurement stored in register 219, to receive the minimum current measurement stored in register 226, and to output the average current. For example, the average current calculator 228 can be configured to calculate an average current using only the minimum and peak current measurements. For example, the average current calculator 228 can calculate the average current as the sum of the minimum and peak current measurements divided by two.

[0031] In some examples, the control circuit 210 can be configured to generate one or more additional current readings corresponding to the measured current at the switching element after the generation of the minimum current reading and before the generation of the peak current reading. In this example, the averaging calculator 228 can be configured to calculate the average current using the minimum current reading, the peak current reading, and the one or more additional current readings. In some examples, the averaging calculator 228 can generate an average current reading corresponding to the measured current at the switching element 112, equidistant from the generation of a minimum current reading and from the generation of a peak current reading.For example, the mean value calculator 228 can calculate the mean current as an average of the mean current measurement corresponding to the measured current at the switching element 112 and equidistant from generating a minimum current measurement and from generating a peak current measurement, and a result of dividing a sum of the minimum current measurement and the peak current measurement by two.

[0032] The fault module 230 can be configured to receive the mean value from the mean value calculator 228, receive the target peak current threshold, and output a fault signal. For example, the fault module 230 can calculate a difference between the mean current and a target mean current value. The adder 232 can be configured to receive the fault signal, receive a preceding off-time, and modify the off-time using the fault signal and the preceding off-time. That is, the adder 232 can modify the off-time using the difference between the mean current and the target mean current value. For example, the adder 232 can add a value corresponding to the difference between the mean current and the target mean current value (e.g., equal to, proportional to, etc.) to the Toff value, which will increase or decrease.

[0033] In an example operation, the comparator 220 compares the measured current with a reference, Iref, that is, the peak current value. As soon as the current reaches this value, the comparator 220 sets a reset input of the SR latch 224 to high. In response to the reset input being set, the clock generator 222 begins counting for a period equal to Toff. The clock generator 222 then generates a gate driver signal to switch the switching element 112 ON after the Toff period.

[0034] When switching element 112 is turned on, the current is at its minimum, and register 226 stores this minimum value. This storage can be performed by connecting the set signal to the enable signal of register 226. Similarly, when switching element 112 is turned off, the current is at its maximum, and register 219 stores this maximum value. This storage can be performed by connecting the reset signal to the enable signal of register 219.

[0035] Once the minimum current value is available, the average value calculator 228 can calculate the average as the sum of the reference value (the maximum value achieved by the current) and the stored minimum value, divided by two. The error module 230 can compare the calculated average with a target value (e.g., a setpoint for the average current) to obtain the difference between the calculated average and the target value. Subsequently, the adder 232 adds the resulting difference to the Toff value, which increases or decreases. Specifically, the Toff value can increase if the calculated average is higher than the target value, while Toff can decrease if the calculated average is not higher than the target value.In this example, the control circuit 210 can provide the next Toff value through the control loop itself, and with each subsequent cycle, the average current can approach the desired value more and more closely. Accordingly, the control circuit 210 can help control the peak and average current values ​​with greater accuracy than systems that use a constant Toff value. Additionally, the control circuit 210 can indirectly help control the accuracy of the current ripple, since the current ripple can depend on how close the average is to the peak references. For example, if the average current is very close to the peak references, a very small ripple can result.

[0036] Fig. Figure 3 is a graphical representation of the initial behavior of the example control circuit 210. Fig. 2 according to one or more techniques of this revelation. The abscissa axis (e.g., horizontal) of Fig. 3 represents time and the ordinate axis (e.g., vertical) of Fig. 3 represents an inductance current 302, a count value 304 and a gate driver signal 306.

[0037] In the example of Fig. At time 3, the switching element 112 is closed, and the control circuit 210 monitors the rise time of the inductance current 302, for example, by measuring the current. At time 310, the inductance current 302 reaches a reference, for example, a target peak current threshold. In this example, register 219 can store a maximum value 330 in response to the inductance current 302 reaching the reference. As a result of the inductance current 302 reaching the reference, the SR latch 224 generates a gate driver signal that causes the switching element 112 to close, and the inductance current 302 decreases. Meanwhile, the clock generator 222 is initialized and generates the count value 304 to begin counting from zero to a specific value, denoted Toff.

[0038] Accordingly, after a time interval equal to Toff, the SR-latch 224 generates a gate driver signal that causes the switching element 112 to close. At this point, the inductance current 302 stops decreasing and begins to increase. In this transition state, the inductance current 302 is at a minimum value of 332. In the example of Fig. Register 226 can store the minimum value 332 after a time interval equal to Toff. Using the maximum value 330 and the minimum value 332, the averaging calculator 228 can generate an error signal that can be used by the adder 232 to modify the off-time, thus controlling the peak and average current values ​​with greater accuracy than systems using a constant Toff value.

[0039] Fig. Figure 4 is a graphical representation of a second behavior of the example control circuit 210. Fig. 2 according to one or more techniques of this revelation. The abscissa axis (e.g., horizontal) of Fig. 4 represents time and the ordinate axis (e.g., vertical) of Fig. 4 represents an inductance current of 402.

[0040] In the example of Fig. 4. The control circuit 210 operates such that the Toff – the period in which the switch is OFF – is updated with each switching cycle based on the average current calculated by the loop. In the example of Fig. In step 4, the fault module 230 compares a calculated average 420 with the desired mean value Imean. In this way, the fault module 230 can derive a signed deviation that the adder 232 can add to a previous value of Toff. The Toff period can be increased or decreased to lengthen or shorten the ripple of the inductance current 402 until the calculated average coincides with the desired value. In this way, the control circuit 210 can reach a steady state.

[0041] Due to technical limitations, the inductance current 402 may not be measured precisely at a minimum current value. The measuring circuit (e.g., the current sensor 214) may exhibit a settling time after the closing of the switching element 112. If this settling time is relevant to the audio signal, the control circuit 210 can extrapolate the minimum current during post-processing. For example, in order to generate a minimum current reading corresponding to the measured current at the switching element 112, the control circuit 210 may be configured to generate the minimum current reading after the switching element 112 has been energized, in order to establish a channel for an initial switch blanking duration.In this example, to generate the peak current measurement corresponding to the measured current at the switching element 112, the control circuit 210 can be configured to generate the peak current measurement after the current at the switching element 112 exceeds the set peak current threshold for a second switch detent duration. In some examples, the control circuit 210 can use more than two measurements during the ON phase.

[0042] The control circuit 210 can be configured to generate a minimum current reading corresponding to the measured current at the switching element 112 in response to the activation of the switching element 112 to establish a channel (e.g., storing a digital value in a memory, storing an analog value in a capacitor, etc.). Examples of generating a minimum current reading in response to the activation of a switching element to establish a channel may include, but are not limited to, generating the minimum current reading (slightly) before, during, or (slightly) after the activation of the switching element to establish the channel.

[0043] Similarly, the control circuit 210 can be configured to generate a peak current measurement corresponding to the measured current at the switching element 112 in response to the current at the switching element 112 exceeding a set peak current threshold of a set of control parameters for the buck converter 104 (storing a digital value in a memory, storing an analog value in a capacitor, etc.). Examples of generating a peak current measurement in response to the current at a switching element exceeding a set peak current threshold may include, but are not limited to, generating the peak current measurement (slightly) before, during, or (slightly) after a current at the switching element exceeds the set peak current threshold.

[0044] The current sensor 214 can detect the common current at the switching element before or substantially simultaneously with the generation of a current measurement. For example, the current sensor 214 can continuously detect a current at the switching element 112, and the last detected measured current is generated as a minimum current measurement only in response to the activation of the switching element 112 to establish a channel. In another example, the current sensor 214 can continuously detect a current at the switching element 112, and the last detected current is generated as a peak current measurement only in response to the current at the switching element 112 exceeding a set peak current threshold.

[0045] Fig. Figure 5 is a conceptual representation illustrating an example control circuit 510 configured to change a target peak current threshold according to one or more techniques of this disclosure. The control circuit 510 can be compared to the control circuit 110 of the disclosure in Fig. 1 of the system shown corresponds to 100. In the example of Fig. The control circuit 510 includes a current sensor 514, a register 519, a comparator 520, a clock generator 522, an SR latch 524, a register 526, an average calculator 528, an error module 530, and an adder 532.

[0046] In the example of Fig. 5 the current sensor 514 is designed to provide an indication of the measured current at the switching element 112 of Fig. The comparator 520 is configured to output a reset signal when the indication of the measured current at the switching element 112 exceeds a target peak current threshold. The clock generator 522 is configured to output a set signal when the switching element 112 has completed its off-time, and the clock generator is initialized in response to the reset signal. The clock generator 522 can determine that an off-time has been completed for the current switching period during the off-state if a count value of the clock generator 522, which is set to zero by the reset signal output by the comparator 220, exceeds the off-time.

[0047] The SR-Latch 524 is configured to reset itself in response to the reset signal and to set itself in response to the set signal. The SR-Latch 524 can output a gate-driving signal to control switching element 112 to establish a channel when the SR-Latch 523 is set, and to control switching element 112 to refrain from establishing a channel when the SR-Latch 524 is reset.

[0048] Register 519 is configured to store a peak current measurement in response to the measured current at switching element 112 exceeding a set peak current threshold. Register 526 is configured to store the minimum current measurement in response to the set signal.

[0049] The average current calculator 528 is configured to receive the peak current measurement stored in register 519, store the minimum current measurement stored in register 526, and output the average current. For example, the average current calculator 528 can be configured to calculate an average current using only the minimum and peak current measurements.

[0050] In some examples, the control circuit 510 can be configured to generate one or more additional current readings, corresponding to the measured current at the switching element, after generating the minimum current reading and before generating the peak current reading. In this example, the averaging calculator 528 can be configured to calculate the average current using the minimum current reading, the peak current reading, and the one or more additional current readings. In some examples, the averaging calculator 528 can generate an average current reading corresponding to the measured current at the switching element 112, equidistant from generating a minimum current reading and from generating a peak current reading.

[0051] The fault module 530 can be configured to receive the mean value from the mean value calculator, receive a target peak current threshold, and output a fault signal. For example, the fault module 530 can calculate a difference between the mean current and a target mean current value. The adder 532 can be configured to receive the fault signal, receive a preceding target peak current threshold, and modify the target peak current threshold using the fault signal and the preceding target peak current threshold. That is, the adder 532 can modify the target peak current threshold using the difference between the mean current and the target mean current value. For example, the adder 532 can add to the target peak current threshold, which will increase or decrease, a value corresponding to the difference between the mean current and the target mean current value (e.g.,(is equal, is proportional, etc.) add to it.

[0052] Fig. Figure 6 is a flowchart consistent with techniques for controlling a buck converter using a calculated average current, according to this disclosure. For illustrative purposes only, the example operations described below are presented in the context of the Fig. 1-5 described. However, the techniques described below can be used in any permutation and any combination with the supply 102, the buck converter 104, the LEDs 106, the control circuit 110, the switching element 112 and the current sensor 114 of Fig. 1 can be used.

[0053] According to one or more techniques of this disclosure, the SR latch 224 turns on the switching element 112 (602). The register 226 generates a minimum current reading (604). The SR latch 224 turns off the switching element 112 in response to the measured current exceeding a maximum current threshold (606). For example, the comparator 220 determines that the measured current exceeds a maximum current threshold and outputs a reset signal to the SR latch 224.

[0054] Register 219 generates a peak current reading (608). For example, register 219 generates the peak current reading in response to the reset signal to SR latch 224. The averager 228 calculates an average current using a minimum current reading and a peak current reading (610). The fault module 230 calculates a difference between a target average current value and the actual average current and calculates the average current (612). Adder 232 modifies a set of control parameters that includes the maximum current threshold and an off-time (614). For example, adder 232 modifies the off-time. In some examples, adder 232 modifies the maximum current threshold. Clock 222 determines that the off-time has elapsed (616), and the process repeats to step 602 for a subsequent switching period.

Claims

[1] Control circuit for a buck converter configured to supply a set of light-emitting diodes (LEDs) (106), wherein the control circuit (110; 210; 510) is configured to: to control a switching element (112) in order to establish, for a current switching period during an on-state, a channel which electrically couples a source (102) with an inductive element (116) of the buck converter; in response to the activation of the switching element (112) to establish the channel, to generate a minimum current reading at the switching element (112) that corresponds to the measured current; as a reaction to the fact that the current at the switching element (112) exceeds a target peak current threshold of a set of control parameters for the buck converter: to control the switching element (112) in order to prevent the establishment of the channel that electrically couples the source to the inductive element (116) for the current switching period during an off state; to generate a peak current reading that corresponds to the measured current at the switching element (112); to calculate an average current using the minimum current reading and the peak current reading; and to change the set of control parameters for the buck converter using the average current; and in response to the fact that the switching element (112) fulfills an off-time of the set of control parameters for the current switching period during the off-state, the switching element (112) is controlled in order to establish the channel that electrically couples the source (102) to the inductive element (116) for a subsequent switching period during an on-state. [2] Control circuit according to claim 1, wherein the control circuit (110; 210; 510) is configured to change the set of control parameters: to calculate a difference between the average current and a target value for the average current; and to change the off-time using the difference between the average current and the target value of the average current. [3] Control circuit according to claim 1, wherein the control circuit (110; 210; 510) is configured to change the set of control parameters: to calculate a difference between the average current and a target value for the average current; and to change the target peak current threshold using the difference between the average current and the target average current. [4] Control circuit according to one of claims 1 to 3, wherein the control circuit (110; 210; 510) is configured to calculate the average current: to calculate an average current using only the minimum current measurement and the peak current measurement. [5] Control circuit according to one of claims 1 to 4, wherein the control circuit is configured to: to generate one or more additional current readings corresponding to the measured current at the switching element (112) after generating the minimum current reading and before generating the peak current reading, wherein the control circuit (110; 210; 510) is configured to calculate the average current using the minimum current measurement, the peak current measurement and one or more additional current measurements. [6] Control circuit according to claim 5, wherein the control circuit (110; 210; 510) is configured to generate one or more additional current measurements: to generate the mean current measurement, which corresponds to the measured current at the switching element (112), at an equal distance from the generation of the minimum current measurement and from the generation of the peak current measurement. [7] Control circuit according to any one of claims 1 to 6, wherein the control circuit comprises (210; 510): a current sensor (214; 514) designed to output an indication of the measured current at the switching element (112); a comparator (220; 520) which is configured to output a reset signal in response to the indication of the measured current at the switching element (112) exceeding the target peak current threshold; a clock generator (222; 522) configured to output a set signal in response to the switching element fulfilling the off-time, wherein the clock generator (222; 522) is initialized in response to the reset signal; and a set-reset (SR) latch (224; 524) configured to reset itself in response to the reset signal and to set itself in response to the set signal, wherein the SR latch (224; 524) outputs a gate-driving signal to drive the switching element (112) to establish the channel when the SR latch (224; 524) is set, and to drive the switching element (112) to refrain from establishing the channel when the SR latch (224; 524) is reset. [8] Control circuit according to claim 7, wherein the control circuit comprises (210; 510): a first register (219; 519) configured to store the peak current measurement value in response to the fact that the measured current at the switching element (112) is greater than the target peak current threshold; a second register (226; 526) designed to store the minimum current measurement in response to the set signal, an average value calculator (228; 528) which is designed to receive the peak current measurement stored in the first register (219; 519), to receive the minimum current measurement stored in the second register (226; 526) and to output the average current; a fault module (230; 530) which is designed to receive the mean value from the mean value calculator (228; 528), to receive the target peak current threshold value and to output a signal. [9] Control circuit according to claim 8, wherein the control circuit (210; 510) further comprises: an adder (232; 532) configured to receive the error signal, receive a preceding off-time; and modify the off-time using the error signal and the outgoing off-time. [10] Control circuit according to claim 8, wherein the control circuit further comprises: an adder (232; 532) configured to receive the fault signal, receive a preceding target peak current threshold, and modify the target peak current threshold using the fault signal and the preceding target peak current threshold. [11] Control circuit according to any one of claims 1 to 10, wherein the control circuit (210; 510), in order to generate the minimum current reading corresponding to the measured current at the switching element (112), is configured to generate the minimum current reading after the switching element (112) has been actuated in order to establish the channel for an initial switch blanking period; and wherein the control circuit (210; 510) is configured to generate the peak current measurement corresponding to the measured current at the switching element (112) after the current at the switching element (112) exceeds the target peak current threshold for a second switch blanking duration. [12] Control circuit according to any one of claims 1 to 11, where the source outputs a voltage between 6 volts and 16 volts; and wherein the buck converter outputs a voltage between 3 volts and 4 volts to the set of LEDs (106), wherein the set of LEDs comprises one or two LEDs. [13] Control circuit according to any one of claims 1 to 12, the supply has a positive node and a reference node; wherein a current sensor (114) which is arranged in an integrated circuit with the switching element (112) is configured to output an indication of the measured current at the switching element (112); wherein the switching element (112) has a control node coupled to the control circuit (110), a first node coupled to the positive node and a second node; wherein the buck converter comprises a diode (118) having an anode coupled to the reference node and a cathode coupled to the second node of the switching element (112); and wherein the inductive element (116) has a first node coupled to the second node of the switching element (112) and a second node coupled to the set of LEDs (106). [14] Method for controlling a buck converter configured to supply a set of light-emitting diodes (LEDs) (106), the method comprising: Controlling a switching element (112) by a control circuit (110; 210; 510) in order to establish, for a current switching period during an on-state, a channel which electrically couples a source (102) to an inductive element (116) of the buck converter; Generating a minimum current reading corresponding to the measured current at the switching element (112) by the control circuit (110; 210; 510) in response to the activation of the switching element (112) in order to establish the channel; as a reaction to the fact that the current at the switching element (112) exceeds a target peak current threshold of a set of control parameters for the buck converter: Controlling the switching element by the control circuit (110; 210; 510) in order to prevent the formation of the channel that electrically couples the source (102) to the inductive element (116) for the current switching period during an off state; Generating a peak current measurement value by the control circuit (110; 210; 510) that corresponds to the measured current at the switching element (112); Calculating an average current using the minimum current measurement and the peak current measurement by the control circuit (110; 210; 510); and Changing the set of control parameters for the buck converter by the control circuit (110; 210; 510) using the average current; and Controlling the switching element by the control circuit (110; 210; 510) in order to establish, for a subsequent switching period during an on-state, the channel that electrically couples the source (102) to the inductive element (116) in response to the fact that the switching element (112) fulfills an off-time of the set of control parameters for the current switching period during the off-state. [15] Method according to claim 14, wherein the changing of the set of control parameters comprises: Calculating the difference between the average current and a target value for the average current; and Changing the off-time using the difference between the average current and the target value of the average current. [16] Method according to claim 14, wherein the changing of the set of control parameters comprises: Calculating the difference between the average current and a target value for the average current; and Changing the target peak current threshold using the difference between the average current and the target average current. [17] Method according to claim 14, wherein the calculation of the average current comprises: Calculating an average current using only the minimum current measurement and the peak current measurement. [18] Method according to any one of claims 14 to 17, further comprising: Generating one or more additional current readings corresponding to the measured current at the switching element (112) by the control circuit (110; 210; 510) after generating the minimum current reading and before generating the peak current reading, where calculating the average current involves calculating the average current using the minimum current measurement, the peak current measurement and one or more additional current measurements. [19] Method according to claim 18, wherein generating one or more additional current measurements includes: Generating the average current reading, which corresponds to the measured current at the switching element, equidistant from generating the minimum current reading and generating the peak current reading. [20] Buck converter system which features: a battery (102); a set of light-emitting diodes (LEDs) (106); a buck converter comprising an inductive element (116); a control circuit (110; 210; 510) designed to: to control a switching element (112) in order to establish a channel for a current switching period during an on state which electrically couples the battery (102) with the inductive element (116); in response to the activation of the switching element (112) to establish the channel, to generate a minimum current reading at the switching element (112) that corresponds to the measured current; as a reaction to the fact that the current at the switching element (112) exceeds a target peak current threshold of a set of control parameters for the buck converter: to control the switching element (112) in order to prevent the formation of the channel that electrically couples the battery to the inductive element (116) for the current switching period during an off state; to generate a peak current reading that corresponds to the measured current at the switching element (112); to calculate an average current using the minimum current reading and the peak current reading; and to change the set of control parameters for the buck converter using the average current; and in response to the fact that the switching element (112) fulfills an off-time of the set of control parameters for the current switching period during the off-state, the switching element (112) is activated to establish the channel that electrically couples the battery to the inductive element (116) for a subsequent switching period during an on-state.

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