Multifunction DC to DC driver

In one example, a system includes a load module, a voltage module, and a controller. The load module is configured to selectively bypass each load unit of a plurality of load units to form a series string of load units. The voltage module is configured to output a voltage across the series string of load units that is based on a target voltage. The controller is configured to output an indication of the target voltage, estimate a time delay for switching one or more load units of the plurality of load units, and output, after outputting the indication of the target voltage for the time delay, a control signal to switch one or more load units of the plurality of load units such that the series string of load units has the target quantity of load units.

TECHNICAL FIELD

This disclosure relates a driver, such as a light emitting diode driver, that is configured to control a voltage supplied to a load, such as a string of light emitting diodes.

BACKGROUND

Drivers may control a voltage at a load. For instance, a light emitting diode (LED) driver may control a voltage supplied to a string of light emitting diodes. Some drivers may include a direct current (DC) to DC converter, such as a buck-boost, buck, boost, or another DC to DC converter. Such DC to DC converters may be required to change the voltage at the load based on a characteristic of the load. For instance, when operating front lighting of an automobile in a high beam mode, the string of light emitting diodes may require a higher voltage than when operating in a low beam mode.

SUMMARY

In general, this disclosure is directed to techniques for reducing a current overshoot and undershoot in a load when changing a quantity of load units. For example, in an exemplary automotive application, a light emitting diode (LED) driver may change a quantity of active light emitting diodes in a string of light emitting diodes from a first quantity for a first mode (e.g., high beam) to a second quantity for a second mode (e.g., low beam) such that a current overshoot and undershoot is minimized. More specifically, in some examples, the light emitting diode driver may delay when switching the string of light emitting diodes from the first quantity for the first mode to the second quantity for the second mode in order to reduce the current overshoot and undershoot. In some examples, the light emitting diode driver may actively drive a current into or from an energy storage element of a direct current (DC) to DC converter to reduce the current overshoot and undershoot. In any case, reducing current undershoot can reduce a deterioration of the performance of the system and reducing current overshoot can prevent damage to the load.

In an example, a system includes a load module, a voltage module, and a controller. The load module is configured to selectively bypass each load unit of a plurality of load units to form a series string of load units. The voltage module is configured to receive, at a control input of the voltage module, an indication of a target voltage and supply an output voltage across the series string of load units that is based on the target voltage. The controller is configured to determine a target quantity of load units used to form the series string of load units, the target quantity of load units being different from a current quantity of load units used to form the series string of load units, determine the target voltage based on the target quantity of load units, output, to the control input of the voltage module, the indication of the target voltage, estimate a time delay for switching one or more load units of the plurality of load units such that the series string of load units has the target quantity of load units, and output, after outputting the indication of the target voltage for the time delay and to the load module, a control signal to switch one or more load units of the plurality of load units such that the series string of load units has the target quantity of load units.

In another example, a method includes determining, by a processor, a target quantity of load units used to form the series string of load units, the target quantity of load units being different from a current quantity of load units used to form the series string of load units and determining, by the processor, a target voltage based on the target quantity of load units. The method further includes outputting, by the processor and to a voltage module configured to supply an output voltage across the string of load units that is based on the target voltage, an indication of the target voltage, estimating, by the processor, a time delay for switching one or more load units such that the series string of load units has the target quantity of load units, and outputting, by the processor and to the load module, after outputting the indication of the target voltage for the time delay, a control signal to switch one or more load units such that the series string of load units has the target quantity of load units.

In another example, a circuit includes a load module, a voltage module, and a feedforward module. The load module is configured to selectively bypass each load unit of a plurality of load units to form a series string of load units. The voltage module is configured to supply an output voltage across the series string of load units that is based on a voltage of a capacitor. The feedforward module is configured to receive an indication of a current quantity of load units used to form the series string of load units and receive an indication of a target quantity of load units used to form the series string of load units. The target quantity of load units is different from the current quantity of load units of the series string of load units. The feedforward module is further configured to detect the voltage of the capacitor, output a target voltage for the capacitor that is based on the current quantity, the target quantity, and the voltage of the capacitor, and modify, using the output, an energy level of the capacitor such that the voltage of the capacitor corresponds to the target voltage.

Details of these and other examples are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims.

DETAILED DESCRIPTION

Some systems may use a direct current (DC) to DC converter to control a voltage supplied to a load. A voltage output by the DC to DC converter may be controlled using a compensation capacitor. For example, as the voltage of the compensation capacitor increases, a duty cycle of the DC to DC converter may increase, thereby increasing a voltage supplied to the load and as the voltage of the compensation capacitor decreases, the duty cycle of the DC to DC converter may decrease, thereby decreasing the voltage supplied to the load. In some examples, a voltage of the compensation capacitor is not accounted for when changing the voltage at the load. For example, in an exemplary automotive application, a light emitting diode (LED) driver may switch a string of light emitting diodes from the high beam mode to a low beam mode and output, to the DC to DC converter, target voltage for the compensation capacitor. However, in the example, the DC to DC converter may supply a voltage at the string of light emitting diodes that causes a current at the string of light emitting diodes to overshoot and/or undershoot the desired current since the compensation capacitor may not immediately have a voltage equal to the target voltage for the compensation capacitor. More specifically, the compensation capacitor must increase or decrease an energy stored in an electric field of the compensation capacitor before having a voltage equal to the target voltage for the compensation capacitor, which causes the DC to DC converter to supply a current to the string of light emitting diodes that is different than the desired current.

In some examples, the driver may estimate a time delay for switching a load to account for charging and discharging the compensation capacitor of a DC to DC converter. For example, a driver may estimate the time delay for switching the load based on a difference of voltage between the target voltage for the compensation capacitor and a current voltage for the compensation capacitor. In this manner, the driver may switch in the load when the compensation capacitor has a voltage that is approximately equal to the target voltage for the compensation capacitor, rather than a voltage that is substantially different than the target voltage for the compensation capacitor. As such, the DC to DC converter may supply a voltage to the load that results in a current that is substantially similar to the desired current, thereby resulting in a reduction in current undershoot and/or overshoot compared to a DC to DC converter that initially supplies a voltage at the load that results in a current that is different than the desired current.

In some examples, the driver may directly modify the energy level of the compensation capacitor of a DC to DC converter such that the compensation capacitor has a voltage substantially equal to a target voltage for the compensation capacitor when the driver switches in the load. For example, the driver may include a feedforward module that actively charges and/or discharges the compensation capacitor such that the energy stored in an electric field of the compensation capacitor corresponds to a voltage that is substantially equal to the target voltage for the compensation capacitor. In this manner, the time delay for switching the load may be reduced to such that the driver may switch in the load approximately simultaneously to the driver modifying the energy level of the compensation capacitor and still ensure that the compensation capacitor has a voltage that is approximately equal to the target voltage for the compensation capacitor. Accordingly, a driver that modifies the energy level of the compensation capacitor of a DC to DC converter may result in a less current undershoot and/or overshoot of current supplied to a load compared to a driver that does not modify the energy level of the compensation capacitor.

FIG. 1is a block diagram illustrating an example system100configured to estimate a time delay for switching load units, in accordance with one or more techniques of this disclosure. As illustrated in the example ofFIG. 1, system100may include load module102, controller (e.g., driver)104, voltage module106, voltage rail116, and reference node118. In some examples, reference node118may be a ground, earth ground, ground plane, or another reference point of system100.

Load module102may include load units120A,120B,120C (collectively “load units120”), switching elements122B and122C (collectively “switching elements122”), and a multifunctional switching unit124. AlthoughFIG. 1illustrates load module102as including three load units120, load module102may include any suitable number of load units120. For example, load module102may include fewer load units120(e.g., only load unit120A, only load unit120B, only load units120A and120B) or more load units120(e.g., four, five, six, or more). Additionally, althoughFIG. 1illustrates load module102as including two switching elements122, load module102may include any suitable number of switching elements122. For example, load module102may include fewer switching elements122(e.g., only switching element122B, only switching element122C) or more switching elements122(e.g., four, five, six, or more). In some examples, load unit120A may have a corresponding switching element122A. Although, the exemplary load module102ofFIG. 1illustrates load module102as including multifunctional switching unit124, in some examples, multifunctional switching unit124may be omitted.

Load units120may be any device configured to receive a voltage output from voltage module106. In some examples, load units120may be light emitting diodes. As used herein, light emitting diodes may refer to any semiconductor light source. In some examples, load units120may be light emitting diodes that include a p-n junction configured to emit light when activated. In an exemplary application, load units120may be light emitting diodes included in a headlight assembly for automotive applications. For instance, load units120may be a matrix of light emitting diodes to light the road ahead of an automotive vehicle. In some examples, load units120may be associated with one or more operational modes. For example, load module102may be configured to operate a first combination of load units120(e.g., light emitting diodes) to operate in a low beam mode and to operate a second combination of load units120(e.g., light emitting diodes) to operate in a high beam mode. In some instances, a mode of load units120may be digitally controlled, for example, by load module102, for adaptive functionality. For instance, in the automotive examples, in response to system100detecting oncoming automobiles, system100may change load units120from operating in a high beam mode to a low beam mode and in response to system100detecting no oncoming automobiles, system100may change load units120from operating in the low beam mode to the high beam mode.

Switching elements122may include any device suitable to permit current to bypass a corresponding load unit of load units120. For example, switching element122B may be switched in such that current output from load unit120A flows through switching element122B instead of load unit120B. Examples of switching elements122may include, but are not limited to, silicon controlled rectifier (SCR), a Field Effect Transistor (FET), and bipolar junction transistor (BJT). Examples of FETs may include, but are not limited to, junction field-effect transistor (JFET), metal-oxide-semiconductor FET (MOSFET), dual-gate MOSFET, insulated-gate bipolar transistor (IGBT), any other type of FET, or any combination of the same. Examples of MOSFETS may include, but are not limited to, PMOS, NMOS, DMOS, or any other type of MOSFET, or any combination of the same. Examples of BJTs may include, but are not limited to, PNP, NPN, heterojunction, or any other type of BJT, or any combination of the same. It should be understood that switching elements122may be a high side switch or low side switch. Additionally, switching elements122may 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.

Multifunctional switching unit124may be configured to drive switching elements122. For example, multifunctional switching unit124may include one or more driver circuits configured to deactivate (e.g., switch out) and activate (e.g., switch in) each switching element of switching elements122. In some examples, multifunctional switching unit124may drive switching elements122according to a signal received from controller104. For example, in response to multifunctional switching unit124receiving an instruction to switch in switching elements122A and B and switch out switching elements122C, multifunctional switching unit124may drive a first signal (e.g., high voltage) to a control node (e.g., gate) of switching elements122A and122B to switch in switching elements122A and122B and may drive a second signal (e.g., low voltage) to a control node (e.g., gate) of switching element122C to switch out switching element122C. In some examples, multifunctional switching unit124may be configured to receive an instruction indicating an operational state (e.g., switched in, switched out) for each switching element of switching elements122. For instance, controller104may output, to multifunctional switching unit124, a first signal (e.g., high voltage) to indicate an instruction for a respective switch to switch in or a second signal (e.g., low voltage) to indicate an instruction for the respective switch to switch out. In some examples, multifunctional switching unit124may be configured to receive an instruction indicating an operational state (e.g., high beam mode, low beam mode, or another operational state) for switching elements122itself. For instance, controller104may output, to multifunctional switching unit124, a first signal (e.g., low voltage) to indicate an instruction for multifunctional switching unit124to operate switching elements122for a low beam mode (e.g., switching out switching element122A and switching in switching element122B-C) or a second signal (e.g., high voltage) to indicate an instruction for multifunctional switching unit124to operate switching elements122for a high beam mode (e.g., switching out switching elements122A-C).

Controller104may be configured to control load module102to switch in and switch out load units120. In some examples, controller104may control voltage module106to output a voltage and/or current to load module102. In some examples, controller104may include an analog circuit. In some examples, controller104may be a microcontroller on a single integrated circuit containing a processor core, memory, inputs, and outputs. For example, controller104may 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 circuitry, as well as any combinations of such components. The term “processor” or “processing circuitry” may generally refer to any of the foregoing logic circuitry, alone or in combination with other logic circuitry, or any other equivalent circuitry. In some examples, controller104may be a combination of one or more analog components and one or more digital components.

Voltage module106may be configured to output a voltage to load module102. As shown, voltage module106may include a power converter110, a modulator112, and a compensator114. In some examples, voltage module106may be or include a DC to DC power converter.

Power converter110may be configured to receive a first voltage and output a second voltage to load module102. In some examples, power converter110may regulate a voltage output to load module102. In some examples, power converter110may regulate a current output to load module102. Power converter110may include one or more switch-mode power converters including, but are not limited to, flyback, buck-boost, buck, auk, or the like. Power converter110may include one or more switching elements to switch in and out one or more energy storage components (e.g., inductor, capacitor, or another energy storage component).

Modulator112may be configured to control a voltage and/or current output by power converter110. In some examples, modulator112may output a switching signal to switch in or switch out one or more switching elements of power converter110. In some examples, modulator112may compare a received voltage with a reference signal. For instance, in response to determining that a received signal is greater than an instantaneous voltage of an offset triangle signal (e.g., sawtooth), modulator112may output a first signal (e.g., high signal) to cause power converter110to switch in the one or more energy storage elements and in response to determining that a received signal is less than or equal to an instantaneous voltage of the offset triangle signal, modulator112may output a second signal (e.g., low signal) to cause power converter110to switch out the one or more energy storage elements. In some examples, modulator112may compare a reference signal and a voltage of a compensation capacitor.

Compensator114may output a voltage to modulator112for controlling a voltage output by voltage module106. For example, compensator114may output, to modulator112, a voltage that is based on a comparison of an estimated current output from voltage module106and a reference voltage. More specifically, in some instances, compensator114may output, to modulator112, a voltage that is based on a difference of an estimated current output from voltage module106and a reference voltage received from controller104. In some examples, compensator114may include an operation amplifier to estimate the current output from voltage module106. In some examples, compensator114may include an operation amplifier to increase a voltage of a signal indicating the difference between the estimated current output from voltage module106and the reference voltage received from controller104. In some examples, compensator114may output a voltage to a compensation capacitor that is coupled to the input of modulator112.

In accordance with one or more techniques, controller104may determine a target quantity number of load units120used to form a series string of load units. For example, controller104may receive (e.g., from a user interaction with system100) an indication to change a mode of the system100from a high beam mode to a low beam mode. In another example, controller104may determine to change a mode of the system100from a high beam mode to a low beam mode in response to sensor data indicating an oncoming automobile. In any case, in response to determining a mode of system100, controller104may determine a quantity number of load units corresponding to the mode. For instance, controller104may determine that the target quantity number of load units120used to form the series string of load units is one when the low beam mode is associated with only load unit120A and controller104may determine that the target quantity number of load units120used to form the series string of load units is three when the high beam mode is associated with load units120A-C.

Controller104may determine a target voltage based on the target quantity of units. For example, each load unit of load units120may be associated with a predetermined voltage. For instance, in response to determining that the series string of load units has a quantity of one (e.g., low beam mode), controller104may determine that the target voltage is the predetermined voltage and in response to determining that the series string of load units has a quantity of three (e.g., high beam mode), controller104may determine that the target voltage is three times the predetermined voltage.

Controller104may output, to a control input of voltage module106, the indication of the target voltage. For example, controller104may output a voltage that corresponding with the target voltage. For example, as the target voltage increases, controller104may increase the voltage output, to the control input of voltage module106, and as the target voltage decreases, controller104may decrease the voltage output, to the control input of voltage module106.

Compensator114may receive the indication of the target voltage and output, to a compensation capacitor and to modulator112, a compensation voltage. For example, compensator114may output the compensation voltage based on a difference between a voltage corresponding to a current flowing from voltage module106to load module102and the indication of the target voltage. More specifically, compensator114may output the compensation voltage as the indication of the target voltage minus a voltage proportional to a current flowing from voltage module106to load module102that is amplified by a gain.

Modulator112may output a switching signal to cause power converter110to switch in one or more energy storage components according to a voltage of the compensation capacitor. For instance, modulator112may compare the compensation voltage with a reference signal (e.g., sawtooth signal) and output a first signal to cause power converter110to switch in the energy one or more energy storage components when the voltage of the compensation capacitor is greater than the reference signal. However, since the compensation capacitor has a rate of change of voltage that is limited by current flowing from the compensation capacitor (e.g., dv/Dt=i/C), a voltage of the compensation capacitor does not change instantly in response to the compensation voltage. As such, modulator112controls power converter110with a duty cycle that is different that a desired target duty cycle, thereby resulting in a current output from voltage module106that is different than a desired current.

Accordingly, in some techniques, rather than simultaneously switching one or more load units of load units120such that the series string of load units has the target quantity of load units and outputting the indication of the target voltage for the target quantity of load units, controller104refrains from switching the one or more load units of load units120until after an estimated time delay. For example, controller104may estimate a time delay for switching one or more load units of load units120such that the series string of load units has the target quantity of load units based on one or more of the target voltage, the voltage of the capacitor, and a capacitance of the capacitor. For instance, the time delay (e.g., Twait) for switching one or more load units of load units120may be calculated as Twait=Ccomp*dVcomp/iea, where Ccompis a capacitance of the compensation capacitor, dVcompis a difference between the target voltage and the compensation voltage of the compensation capacitor, and ieais a current output from compensator114into modulator112.

After controller104outputs the indication of the target voltage for the time delay and to a control input of voltage module106, controller104outputs, to load module102, a control signal to switch one or more load units of load units120such that the series string of load units has the target quantity of load units. For instance, in response to outputting, to compensator114of voltage module106, an indication of a target voltage that corresponds to the series string of load units having a quantity of three (e.g., high beam mode) for the time delay, controller104may output, to load module102, a control signal to switch in load units120A-C. In response to receiving the control signal to switch one or more load units of load units120such that the series string of load units has the target quantity of load units, load module102switches one or more load units of load units120such that the series string of load units has the target quantity of load units. For instance, in response to receiving, from controller104, the control signal to switch in load units120A-C, load module switches out switching elements122B and122C such that current output from voltage module106flows through load units120A-C.

In this manner, the target quantity of load units may not be switched in until the compensation capacitor has sufficient time to charge or discharge such that the compensation voltage is equal to the target voltage. As such, voltage module106may supply a current to load module102that is substantially similar to the desired current, thereby resulting in a reduction in current undershoot and/or overshoot compared with systems that do not account for a discharge or charge time of the compensation capacitor.

FIG. 2Ais a conceptual diagram illustrating an example first circuit200A of the system ofFIG. 1, in accordance with one or more techniques of this disclosure. As illustrated, circuit200A includes load module202, power converter210, modulator212A, compensator214, voltage rail216, reference node218, compensation capacitor230, and compensation resistive element232. Load module202may be an example of load module102ofFIG. 1. For example, as shown, load module202may include light emitting diode220A,220B,220C, and220D (collectively “LEDs220”) that may be examples of load units120. Power converter210, modulator212A, compensator214may be an example of voltage module106ofFIG. 1. For instance, power converter210may be an example of power converter110ofFIG. 1, modulator212A may be an example of modulator112ofFIG. 1, and compensator214may be an example of compensator114ofFIG. 1.

Compensator214may receive the indication of the target voltage and output, to compensation capacitor230, a compensation voltage. For example, compensator214may output the compensation voltage based on a difference between a voltage across resistive element242that corresponds to a current flowing from power converter210to load unit202and the indication of the target voltage (e.g., a VREFfrom controller104). More specifically, compensator214may output the compensation voltage to compensation capacitor230as the indication of the target voltage (e.g., VREFfrom controller104)) minus a voltage across resistive element242that is amplified by a gain. Compensator214may include one or more analog components, for instance, but not limited to, one or more operational amplifiers.

Modulator212A may output, to power converter210, a control signal for controlling a voltage and/or current output from power converter210. For example, modulator212A may compare the voltage of compensation capacitor230with a reference signal (e.g., sawtooth signal) and output, to power converter210, a switching signal indicating a duty cycle. More specifically, modulator212A may output the switching signal with a high signal when the voltage of compensation capacitor230is greater than the reference signal and output the switching signal with a low signal when the voltage of compensation capacitor230is not greater than the reference signal.

Power converter210may include a driver234, switching unit236, inductor238, capacitor240, and voltage source233. Voltage source233may be any suitable device configured to supply electrical power. For example, voltage source233may be an energy storage device (e.g., battery), an output of a rectifier, an output of a converter, or another device configured to supply electrical power. As shown, driver234may receive, from modulator212A, the switching signal, and selectively couple inductor238and a voltage source233according to the switching signal. For example, when the switching signal is low, driver234may cause switching unit236to couple inductor238to reference node218and when the switching signal is high, driver234may cause switching unit236to couple inductor238to voltage source233. In this manner, switching unit236is switched to move energy between a magnetic field of inductor238and an electric field of capacitor240such that a voltage output onto voltage rail216is regulated according to the duty cycle output by modulator212A, which is controlled according to the voltage of compensation capacitor230.

Accordingly, in some techniques, rather than simultaneously switching LEDs220of load module202, controller104may refrain from switching LEDs220until after the voltage at compensation capacitor230equals to the compensation voltage output by compensator214. In this manner, power converter210may supply a current to LEDs220that is substantially similar to the desired current, thereby resulting in a reduction in current undershoot and/or overshoot compared with circuits that do not account for a discharge or charge time of compensation capacitor230.

FIG. 2Bis a conceptual diagram illustrating an example second circuit200B of the system ofFIG. 1, in accordance with one or more techniques of this disclosure. As illustrated circuit200B includes load module202, power converter210, modulator212B, compensator214, voltage rail216, reference node218, compensation capacitor230, and compensation resistive element232. Power converter210, modulator212B, compensator214may be an example of voltage module106ofFIG. 1. For instance, power converter210may be an example of power converter110ofFIG. 1, modulator212B may be an example of modulator112ofFIG. 1, and compensator214may be an example of compensator114ofFIG. 1.

Similarly to modulator212A, modulator212B may output, to power converter210, a switching signal for controlling a voltage and/or current output from power converter210. However, modulator212B may further include a mean current loop, for instance, but not limited, to control a buck converter. More specifically, modulator212B may modify the voltage of compensation capacitor230with a signal that is based on a current flow of inductor238, and compare the modified voltage of compensation capacitor230, rather than only the voltage of compensation capacitor230, with the reference signal (e.g., sawtooth signal) and output, to power converter210, a switching signal indicating a duty cycle.

FIG. 3is a circuit diagram illustrating an example circuit300of system100ofFIG. 1, in accordance with one or more techniques of this disclosure. As illustrated circuit300includes load module302, controller304, voltage module306, resistive elements351and352, voltage rail316, reference rail318, compensation capacitor350, and output capacitor340. Load module302may be an example of load module102ofFIG. 1. For example, load module302may include load units320A-C (collectively “load units320”), which may be examples of load units120ofFIG. 1, switching elements322B and322C (collectively “switching elements322), which may be examples of switching elements122ofFIG. 1, and switching unit324, which may be an example of multifunctional switching unit124ofFIG. 1. Voltage module306may be an example of voltage module106ofFIG. 1and/or an example of voltage module206ofFIGS. 2A and 2B. For example, voltage module306may include any combination of power converter110, modulator112, and compensator114ofFIG. 1, power converter210, modulator212A, and compensator214ofFIG. 2A, and power converter210, modulator212B, and compensator214ofFIG. 2B.

Voltage module306may be configured to output a voltage to output capacitor340and load module302that is based on a voltage of compensation capacitor350and a feedback voltage corresponding to the voltage output to load module302. As shown, the feedback voltage received by voltage module306is a voltage of a voltage divider formed by resistive elements351and352. For example, voltage module306may buck or boost a voltage received an input (e.g., Vin) of voltage module306according to a duty cycle and output the resulting voltage at an output (e.g., Vout) of voltage module to output capacitor340and to load module302. In the example, voltage module306may determine the duty cycle according to a voltage of compensation capacitor350and the voltage of a voltage divider formed by resistive elements351and352.

Voltage module306may be configured to control a voltage of compensation capacitor350. For example, in response to receiving a voltage reference from controller304, voltage module306may charge and/or discharge compensation capacitor350according to the voltage reference received from controller304. In this manner, voltage module306may change the resulting voltage at an output (e.g., Vout) of voltage module to output capacitor340and load module302to a desired voltage.

Rather than simultaneously changing the voltage reference to accommodate a target quantity of load units320and switching one or more load units of load units320such that a series string of load units320has the target quantity, controller304refrains from switching one or more load units of load units320until after a time delay. For example, controller304may estimate the time delay based on any combination of the input voltage received at an input of (e.g., Vin) of voltage module306, an output voltage output, at an output (e.g., Vout) of voltage module306, an inductance of an inductor of voltage module306(e.g., inductor238of power converter210ofFIGS. 2A and 2B), a capacitance of compensation capacitor350, and a frequency used to switch one or more energy storage elements of voltage module306(e.g., inductor238and capacitor240of power converter210ofFIGS. 2A and 2B). For instance, controller304may calculate the time delay (e.g., Twait) as Twait=Ccomp*dVcomp/iea, where Ccompis a capacitance of compensation capacitor350, dVcompis a difference between a target voltage for the target number of load units320and the voltage of compensation capacitor350, and ieais a current output from compensation capacitor350into voltage module306.

After controller304outputs the indication of the target voltage for the time delay, controller304outputs, to load module302, a control signal to switch one or more load units of load units320such that the series string of load units has the target quantity of load units. In this manner, the target quantity of load units may not be switched in until compensation capacitor350has sufficient time to charge or discharge such that the compensation voltage is stable. As such, voltage module306may supply a current to load module302that is substantially similar to the desired current, thereby resulting in a reduction in current undershoot and/or overshoot compared with circuits that do not account for a discharge or charge time of compensation capacitor350.

FIG. 4is a diagram illustrating an example performance of system100ofFIG. 1, in accordance with one or more techniques of this disclosure. For purposes of illustration only,FIG. 4is described below within the context of circuit300ofFIG. 3. However, the techniques described below can be used in any permutation, and in any combination, with load module102, controller104, voltage module106, voltage rail116, and reference node118ofFIG. 1.

In the example ofFIG. 4, controller304initially, at state410, outputs a reference voltage to voltage module306to cause voltage module306to output a voltage for three of load units320(e.g., load units320A-C). As shown, in state410, controller304outputs, to load module302, switching signal408A that switches in three of load units320(e.g., load units320A-C). Accordingly, voltage module306outputs a voltage to load module302such that a feedback voltage (e.g., VFB)402received, by voltage module306, from the voltage of a voltage divider formed by resistive elements351and352, is at a high voltage level420.

At state412, controller304outputs a reference voltage to voltage module306to cause voltage module306to output a voltage for one of load units320(e.g., load unit320A, load unit320B, or load unit320C). However, rather than simultaneously changing both the voltage reference and switching the load units of load module302, during state412, controller304refrains from switching one or more load units of load units320until after a time delay406. Accordingly, in state412, controller304continues to output, to load module302, switching signal408A that switches in three of load units320(e.g., load units320A-C). As shown, voltage404of compensation capacitor350stabilizes to match a desired voltage for switching in one of load units320during state412and feedback voltage (e.g., VFB)402received, by voltage module306, transitions from the high voltage level420to a low voltage level422.

At state414, time delay406has elapsed, and controller304outputs, to load module302, switching signal408B that switches in one of load units320(e.g., load unit320A, load unit320B, or load unit320C). Since voltage404of compensation capacitor350has stabilized to match a desired voltage for switching in one of load units320during state412and feedback voltage (e.g., VFB)402received, by voltage module306, has transitioned from the high voltage level420to the low voltage level422, voltage module306outputs a voltage to load module302that has minimal overshoot and undershoot. For example, as shown, feedback voltage (e.g., VFB)402received, by voltage module306, has a low voltage level422with minimal overshoot and undershoot.

FIG. 5is a flow diagram consistent with techniques that may be performed by the system ofFIG. 1, in accordance with this disclosure. For purposes of illustration only,FIG. 5is described below within the context of system100ofFIG. 1and circuit300ofFIG. 3. However, the techniques described below can be used in any permutation, and in any combination, with load module102, controller104, voltage module106, voltage rail116, and reference node118ofFIG. 1.

In accordance with one or more techniques of this disclosure, controller104determines a target quantity of load units (502). For example, controller104detects an oncoming automobile and determines to reduce the target quantity of load units to correspond with a low beam mode of load module102. Controller104determines a target voltage based on the target quantity of load units (504). For example, controller104multiplies the target quantity of load units by a predetermined voltage associated with load units120. Controller104outputs an indication of the target voltage to a voltage module configured to supply an output voltage across a string of load units, the output voltage being based on the target voltage (506). For example, controller104outputs a voltage reference indicating the target voltage to compensator114of voltage module106.

Controller104receives an indication of a voltage and current of a capacitor of the voltage module, the voltage module being configured to control the output voltage based on the voltage of the capacitor (508). For example, controller104receives a voltage and current of compensation capacitor350. Controller104estimates a time delay for switching one or more load units in the series string of load units based on the voltage and current of the capacitor, a capacitance of the capacitor, and the target voltage (510). For example, controller estimates the time delay (e.g., Twait) as Twait=Ccomp*dVcomp/iea, where Comp is a capacitance of compensation capacitor350, dVcompis a difference between a target voltage for the target number of load units120and the voltage of compensation capacitor350, and ieais a current output from compensation capacitor350into voltage module306.

Controller104outputs, after outputting the target voltage for the time delay, a control signal to switch the target quantity of the load units to form the series string of load units having the target quantity (512). For example, controller104outputs, to load module102, a control signal to switch in load unit120A and to switch out load units120B and120C to correspond with the low beam mode of load module102.

FIG. 6is a conceptual block diagram illustrating an example system600configured to modify an energy level of a capacitor for switching load units, in accordance with one or more techniques of this disclosure. As illustrated system600includes load module602, controller604, voltage module606, feedforward module608, voltage rail616, ground rail618, and compensation capacitor650. Load module602may be an example of load module102ofFIG. 1. For example, load module602may include load units620A-C (collectively “load units620”), which may be examples of load units120ofFIG. 1, switching elements622B and622C (collectively “switching elements622), which may be examples of switching elements122ofFIG. 1, and switching unit624, which may be an example of multifunctional switching unit124ofFIG. 1. Voltage module606may be an example of voltage module106ofFIG. 1and/or an example of voltage module206ofFIGS. 2A and 2B. For example, voltage module606may include power converter610, which may be an example of power converter110ofFIG. 1, modulator612, which may be an example of modulator112ofFIG. 1, and compensator614, which may be an example of compensator114ofFIG. 1.

Rather than charging and discharging compensation capacitor650using voltage module606, feedforward module608may be configured to force compensation capacitor650to a desired voltage. For example, feedforward module608may output a voltage with a higher current higher to more quickly force compensation capacitor650to the target voltage when a current voltage of compensation capacitor650is less than the target voltage. Feedforward module608may include analog components. For example, feedforward module608may include one or more operational amplifiers.

In accordance with one or more techniques, feedforward module608may receive an indication of a current quantity of load units620used to form a series string of load units620and receive an indication of a target quantity of load units620used to form the series string of load units620. For example, feedforward module608may receive a signal indicating that the current quantity of load units620is three and that the target quantity of load units620is one.

Feedforward module608may detect a voltage of compensation capacitor650. For example, feedforward module608may sample a voltage at compensation capacitor650. Feedforward module608may output a target voltage for the capacitor that is based on the current quantity, the target quantity, and the voltage of the capacitor. For example, feedforward module608may output a voltage to compensation capacitor650that is proportional to the voltage of compensation capacitor650modified by a difference between the current quantity of load units620and the target quantity of load units620. More specifically, feedforward module608may output a voltage to compensation capacitor350that increases in magnitude as a difference in the current quantity of load units620and the target quantity of load units620increases and decreases in magnitude as a difference in the current quantity of load units620and the target quantity of load units620decreases. In examples where a current control loop is used (e.g.,FIG. 2B), an offset may be added to account for the mean current control. In this manner, feedforward module608may force the voltage of compensation capacitor650to the target voltage. As such, voltage module606may supply a current to load module602that is substantially similar to the desired current, thereby resulting in a reduction in current undershoot and/or overshoot compared with systems that do not account for a discharge or charge time of compensation capacitor650.

FIG. 7Ais a circuit diagram illustrating an example first circuit700A of system600ofFIG. 6, in accordance with one or more techniques of this disclosure. As illustrated circuit700includes feedforward module708A which may be an example of feedforward module608ofFIG. 6. For purposes of illustration only,FIG. 7Ais described below within the context of system600ofFIG. 6. However, the techniques described below can be used in any permutation, and in any combination, with includes load module602, controller604, voltage module606, feedforward module608, voltage rail616, ground rail618, and compensation capacitor650ofFIG. 6.

Feedforward module708includes capacitor730coupled to reference node718(e.g., ground), operational amplifier732, inverter (e.g., a logical inverter)734, switching elements736and738, first switching elements740A-F (collectively “first switching elements740”), resistive elements741A-F (collectively “resistive elements741”), and second switching elements742A-F (collectively “second switching elements742”). Examples of switching elements736,738,740, and742may include, but are not limited to, silicon controlled rectifier (SCR), a Field Effect Transistor (FET), and bipolar junction transistor (BJT). In some examples, resistive elements741may be sized to have identical resistance values. Additionally, although feedforward module708is configured to support a chain of up to six load units (e.g.,620), feedforward module708may be configured to support any suitable number of load units, for instance, by including additional first switching elements740, second switching elements742, and resistive elements741.

First switching elements740may be configured to selectively couple a second input of operation amplifier732to a resistive element of resistive elements741corresponding to the current quantity of load units. Additionally, second switching elements742may be configured to selectively couple an output of second switching elements742to a resistive element of resistive elements741corresponding to the target quantity of load units. For example, when switching from a high beam mode corresponding with three load units to a low beam mode corresponding with one load unit, first switching element740C couples the second input (e.g., negative) of operation amplifier732to resistive element741C and first switching elements740A-B and740D-F are switched out, which corresponds with three load units, and second switching element742A couples the output of second switching elements742to resistive element741A and second switching elements742B-F are switched out, which corresponds with one load unit.

In accordance with one or more techniques, feedforward module708A may receive (e.g., from controller604ofFIG. 6) a signal indicating a current quantity of load units (e.g.,620) that switches in one of first switching elements740and a signal indicating a target quantity of load units (e.g.,620) that switches in one of second switching elements742. For example, when switching from a high beam mode corresponding with three load units to a low beam mode corresponding with one load unit, feedforward module708A may receive (e.g., from controller604ofFIG. 6) a signal indicating a current quantity of load units (e.g.,620) that switches in first switching element740C and a signal indicating a target quantity of load units (e.g.,620) that switches in second switching element742A.

Feedforward module708A may detect a voltage of the compensation capacitor. For example, feedforward module708A may sample a voltage at the compensation capacitor by receiving, at a force enable input (e.g., “Force_en”), from controller604, a signal having a logical value (e.g., a low signal) that switches in switching element736and switches, via inverter734, out switching element738. In the example, operating switching element736in a closed state (e.g., switched in) permits compensation capacitor650to charge capacitor730to match a voltage of compensation capacitor650.

Feedforward module708A may output a target voltage to force the compensation capacitor (e.g.,650) to a target voltage level. For example, switching elements736and738charge and/or discharge capacitor730to a voltage that is substantially equal to a voltage of the compensation capacitor. In the example, switching elements740and742may electronically couple operation amplifier732such that a switching state of first switching elements740correspond to the current quantity of load units, and a switching state of second switching elements742correspond to the target quantity of load units. In this manner, feedforward module708A outputs the target voltage based on the current quantity, the target quantity, and the voltage of the compensation capacitor. For example, when switching from a high beam mode corresponding with three load units to a low beam mode corresponding with one load unit, feedforward module708A switch in only first switching element740C and only second switching element742A.

Feedforward module708A may modify, using the output, an energy level of the compensation capacitor such that the voltage of the capacitor corresponds to the target voltage. For example, feedforward module708A may receive, at the force enable input (e.g., “Force_en”), from controller604, a signal having a logical value (e.g., a high signal) that switches in switching element738and switches out switching element736. In the example, operating switching element738in a closed state forces the voltage of the compensation capacitor to match the target voltage output by feedforward module708A. In this manner, the voltage of the compensation capacitor may be forced by the feedforward module708A to the target voltage. As such, a voltage module (e.g.,606) may supply a current to a load module (e.g.,602) that is substantially similar to the desired current, thereby resulting in minimal current undershoot and/or overshoot compared with circuits that do not account for a discharge or charge time of the compensation capacitor.

FIG. 7Bis a circuit diagram illustrating an example second circuit of the system ofFIG. 6, in accordance with one or more techniques of this disclosure. As illustrated circuit700B includes feedforward module708B which may be an example of feedforward module608ofFIG. 6. For purposes of illustration only,FIG. 7Bis described below within the context of system600ofFIG. 6. However, the techniques described below can be used in any permutation, and in any combination, with includes load module602, controller604, voltage module606, feedforward module608, voltage rail616, ground rail618, and compensation capacitor650ofFIG. 6.

Similarly to feedforward module708A ofFIG. 7A, feedforward module708B may output a target voltage to force the compensation capacitor (e.g.,650) to a target voltage. However, feedforward module708B may further include operation amplifier760and capacitor762. As shown, operation amplifier760includes a first terminal (e.g., positive) coupled to capacitor762and to an output of a sampled mean current contribution and a second terminal (e.g. negative) coupled to an output of operation amplifier760. In this manner, feedforward module708B may modify the target voltage to account for the mean current contribution. More specifically, feedforward module708B may add, to the output, an offset voltage indicating the mean current contribution of a voltage module (e.g.,606).

FIG. 8is a flow diagram consistent with techniques that may be performed by example system600ofFIG. 6, in accordance with this disclosure. For purposes of illustration only,FIG. 8is described below within the context of system600ofFIG. 6, circuit700A ofFIG. 7A, and circuit700B ofFIG. 7B. However, the techniques described below can be used in any permutation, and in any combination, with load module602, controller604, voltage module606, voltage rail616, feedforward module608, ground rail618, and compensation capacitor650ofFIG. 6.

In accordance with one or more techniques of this disclosure, feedforward module608receives an indication of a current quantity of load units to form a series string of load units (802). For example, feedforward module608receives, from controller604, an indication that system600is transitioning from a high beam mode corresponding to a current quantity of three load units. Feedforward module608receives an indication of a target quantity of load units to form the series string of load units (804). For example, feedforward module608receives, from controller604, an indication that system600is transitioning to a low beam mode corresponding to a current quantity of one load unit. Feedforward module608detects a voltage of a capacitor (806). For example, controller604may output to a force enable input (e.g., “Force_en”) of feedforward module708A ofFIG. 7Aor feedforward module708B ofFIG. 7Ba signal having a logical value (e.g., a low signal) that switches in switching element736and switches out switching element738.

Feedforward module608outputs, a target voltage for the capacitor that is based on the current quantity, target quantity, and the voltage of the capacitor (808). For example, switching elements740and742ofFIGS. 7A and 7Bmay electronically couple operation amplifier732ofFIGS. 7A and 7Bsuch that a switching state of first switching elements740ofFIGS. 7A and 7Bcorrespond to the current quantity of three load units, and a switching state of second switching elements742ofFIGS. 7A and 7Bcorrespond to the target quantity of one load unit.

Feedforward module608modifies, using the output, an energy level of the capacitor such that the voltage of the capacitor corresponds to the target voltage (810). For example, controller604may output to a force enable input (e.g., “Force_en”) of feedforward module708A ofFIG. 7Aor feedforward module708B ofFIG. 7Ba signal having a logical value (e.g., a high signal) that switches in switching element738ofFIGS. 7A and 7Band switches out switching element736ofFIGS. 7A and 7B. In the example, operating switching element738ofFIGS. 7A and 7Bin a closed state forces the voltage of the compensation capacitor to match the target voltage.

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

A system comprising: a load module configured to selectively bypass each load unit of a plurality of load units to form a series string of load units; a voltage module configured to receive, at a control input of the voltage module, an indication of a target voltage and supply an output voltage across the series string of load units that is based on the target voltage; and a controller configured to: determine a target quantity of load units used to form the series string of load units, the target quantity of load units being different from a current quantity of load units used to form the series string of load units; determine the target voltage based on the target quantity of load units; output, to the control input of the voltage module, the indication of the target voltage; estimate a time delay for switching one or more load units of the plurality of load units such that the series string of load units has the target quantity of load units; and output, after outputting the indication of the target voltage for the time delay and to the load module, a control signal to switch one or more load units of the plurality of load units such that the series string of load units has the target quantity of load units.

The system of example 1, wherein the controller is further configured to: estimate the time delay for switching one or more load units of the plurality of load units such that the series string of load units has the target quantity of load units based on the target voltage.

The system of any combination of examples 1-2, further comprising: a capacitor, wherein the voltage module comprises: a compensator configured to supply energy to the capacitor based on the indication of the target voltage; and a modulator configured to control the output voltage across the series string of load units based on a voltage of the capacitor.

The system of any combination of examples 1-3, wherein the controller is further configured to: receive an indication of the voltage of the capacitor; and estimate the time delay for switching one or more load units of the plurality of load units in the series string of load units based further on the voltage of the capacitor and a capacitance of the capacitor.

The system of any combination of examples 1-4, wherein: the modulator is configured to control the output voltage across the series string of load units based on the voltage of the capacitor by outputting a switching signal indicating a duty cycle that is based on the voltage of the capacitor, and the voltage module further comprises: one or more energy storage elements; and a switching unit configured to selectively switch the one or more energy storage elements using the switching signal.

The system of any combination of examples 1-5, wherein: the plurality of load units is a plurality of light emitting diodes; the target quantity of load units is a target quantity of light emitting diodes; the series string of load units is a series string of light emitting diodes; and determining the target quantity of load units used to form the series string of load units comprises: in response to determining that a headlight mode of the system corresponds to a high beam mode, determining the target quantity of light emitting diodes according to a quantity of light emitting diodes associated with the high beam mode; and in response to determining that a headlight mode of the system corresponds to a low beam mode, determining the target quantity of light emitting diodes according to a quantity of light emitting diodes associated with the low beam mode.

A method comprising: determining, by a processor, a target quantity of load units used to form the series string of load units, the target quantity of load units being different from a current quantity of load units used to form the series string of load units; determining, by the processor, a target voltage based on the target quantity of load units; outputting, by the processor and to a voltage module configured to supply an output voltage across the string of load units that is based on the target voltage, an indication of the target voltage; estimating, by the processor, a time delay for switching one or more load units such that the series string of load units has the target quantity of load units; and outputting, by the processor and to the load module, after outputting the indication of the target voltage for the time delay, a control signal to switch one or more load units such that the series string of load units has the target quantity of load units.

The method of example 7, further comprising: estimating, by the processor, the time delay for switching one or more load units such that the series string of load units has the target quantity of load units based on the target voltage.

The method of any combination of examples 7-8, further comprising: receiving, by the processor, an indication of a voltage of a capacitor, the voltage module being configured to control the output voltage across the series string of load units based on the voltage of the capacitor, wherein the estimating of the time delay for switching one or more load units such that the series string of load units has the target quantity of load units is further based on the voltage of the capacitor.

The method of any combination of examples 7-9, wherein the estimating of the time delay for switching one or more load units such that the series string of load units has the target quantity of load units is further based on a capacitance of the capacitor.

The method of any combination of examples 7-10, further comprising: determining, by the processor, an indication of a current flowing from the capacitor, wherein the estimating of the time delay for switching one or more load units such that the series string of load units has the target quantity of load units is further based on the current flowing from the capacitor.

The method of any combination of examples 7-11, further comprising: determining, by the processor, a difference between the target voltage and the voltage of the capacitor, wherein the estimating of the time delay for switching one or more load units such that the series string of load units has the target quantity of load units is further based on the difference between the target voltage and the voltage of the capacitor.

The method of any combination of examples 7-12, further comprising: outputting, by the processor, after outputting the indication of the target voltage and before outputting the control signal to switch one or more load units such that the series string of load units has the target quantity of load units, a control signal to switch one or more load units such that the series string of load units has the current quantity of load units.

A circuit comprising: a load module configured to selectively bypass each load unit of a plurality of load units to form a series string of load units; a voltage module configured to supply an output voltage across the series string of load units that is based on a voltage of a capacitor; and a feedforward module configured to: receive an indication of a current quantity of load units used to form the series string of load units; receive an indication of a target quantity of load units used to form the series string of load units, the target quantity of load units being different from the current quantity of load units of the series string of load units; detect the voltage of the capacitor; output a target voltage for the capacitor that is based on the current quantity, the target quantity, and the voltage of the capacitor; and modify, using the output, an energy level of the capacitor such that the voltage of the capacitor corresponds to the target voltage.

The circuit of example 14, wherein the feedforward module comprises: a plurality of resistive elements coupled in series to form a series string of resistive elements; an operational amplifier including a first input, a second input, and an output, the output of the operational amplifier being coupled to the series string of resistive elements; a first set of switching elements configured to selectively couple the second input of the operation amplifier to a resistive element of the resistive elements corresponding to the current quantity of load units; and a second set of switching elements configured to selectively couple an output of the second set of switching elements to a resistive element of the resistive elements corresponding to the target quantity of load units.

The circuit of any combination of examples 14-15, wherein the feedforward module further comprises: a first switching element configured to selectively couple the first input of the operation amplifier to the capacitor.

The circuit of any combination of examples 14-16, wherein the feedforward module further comprises: a second switching element configured to selectively couple the output of the second set of switches to the capacitor.

The circuit of any combination of examples 14-17, wherein the feedforward module is further configured to: add, to the output, an offset voltage indicating a mean current of the voltage module.

The circuit of any combination of examples 14-18, wherein the voltage module comprises: a modulator configured to control the output voltage across the series string of load units based on the voltage of the capacitor by outputting a switching signal indicating a duty cycle that is based on the voltage of the capacitor; one or more energy storage elements; and a switching unit configured to selectively switch the one or more energy storage elements using the switching signal.

The circuit of any combination of examples 14-19, wherein the plurality of load units is a plurality of light emitting diodes, the current quantity of load units is a current quantity of light emitting diodes, the target quantity of load units is a target quantity of light emitting diodes, and the series string of load units is a series string of light emitting diodes, the circuit further comprising: a controller configured to: output, to the feedforward module, the current quantity of light emitting diodes; determine the target quantity of light emitting diodes based on a head light mode of the circuit; output, to the feedforward module, the target quantity of light emitting diodes; output, to the load module, a control signal to switch one or more light emitting diodes of the plurality of light emitting diodes such that the series string of light emitting diodes has the target quantity of light emitting diodes.

Various aspects have been described in this disclosure. These and other aspects are within the scope of the following claims.