Wide-range precision supply circuit

Abstract

A precision supply circuit for conducting a current (pulse or continuous) having an accurately controlled current level through a load is described, over a wide current and voltage range. The supply circuit includes a selectable current sense resistor within a feedback loop that controls the current output to accommodate a wide current range provided to the load. The circuit may include a programmable output voltage applied to the load. The circuit can provide voltage information detected from a single sense node within the supply circuit to enable protection of the load and the power transistor conducting current through the load.

Description

Technical Field

[0001] (Cross - Reference to Related Applications) This application claims the benefit of priority under 35 U.S.C. § 119(e) to U.S. Patent Application No. 63 / 340,300, entitled "High dynamic Range LED Control Systems and Methods," filed on May 10, 2022, and U.S. Patent Application No. 63 / 343,058, entitled "High dynamic Range LED Control Systems and Methods," filed on May 17, 2022, the entire disclosures of which are incorporated herein by reference.

Background Art

[0002] Modern control systems can include a number of controlled and / or monitored devices (e.g., sensors, cameras, artificial lighting, counters, motors) and one or more controllers (e.g., microprocessors or microcontrollers). The controller can receive and process data from the monitored devices and issue commands to operate the controlled devices based at least in part on the received data. Such control systems are often implemented in dynamic environments (e.g., an automated factory assembly line that includes multiple inspection stations and utilizes machine vision technology) where the environmental conditions change frequently, causing changes in the signals provided by the monitored devices and changes in the responsiveness of the control signals output by the controller. Common components in these dynamic environments include controllable cameras and artificial lighting to facilitate effective imaging by the cameras. Conventional examples of such artificial lighting include, but are not limited to, LED - based lighting systems.

Summary of the Invention

[0003] This specification describes circuits, devices, and methods for accurately controlling current and program voltage (over a wide dynamic range) supplied to a load such as an LED lamp or other current-driven device. Such LED lamps can be used to illuminate targets for machine vision applications that are closely synchronized with automated equipment. Such targets can range in size from small objects, micron-sized objects, or sub-micron-sized objects as seen in a microscope system to large objects as seen in automotive vehicle assembly. In one example, an LED lamp can be used as a strobe light source to illuminate an object during image acquisition by one or more cameras within an automated control system. The acquired image can then be processed to obtain information for the automated control system. In some implementations, a circuit for accurately controlling the current and voltage supplied to one or more LED lamps can be included in a compact camera used to image an object illuminated by the one or more LED lamps.

[0004] The precision supply circuit can include a precision current controller and a programmable voltage that operates over a wide range of currents (at least one order of magnitude) and a wide range of voltages (at least one order of magnitude). The voltage can be programmed for a load (such as an LED lamp that may require any one of a wide range of supply voltages) to reduce or minimize waste (heat) and / or stress of energy for both the load and the current controller. The precision supply circuit can provide current and voltage at precise time intervals (referred to as pulses) to accurately control the amount (and charge) of current supplied to the load. The pulses can be accurately time-adjusted and have fast rise and fall times with reduced overshoot after on and off transitions. A protection function to prevent over-driving of the load and / or the current controller can also be implemented in the precision supply circuit.

[0005] One implementation relates to a supply circuit comprising a transistor arranged to conduct current through a load and a feedback circuit for applying a signal to the transistor to control the amplitude of the current conducted by the transistor. The feedback circuit receives a first feedback signal from a first sense node located in a first current path through which at least a first portion of the current flows when the current flows through the load, and receives a second feedback signal from a second sense node located in a second current path through which at least a second portion of the current flows when the current flows through the load and the impedance between the first sense node and the second sense node is bypassed by a second current path.

[0006] Some embodiments relate to a supply circuit comprising a first transistor arranged to conduct current through a load, a first resistor in a first circuit path through which at least a first portion of the current flows, a second resistor connected in series with the first resistor and through which at least a second portion of the current flows when connected to the load, a second transistor arranged to shunt current around the second resistor, and a feedback circuit. The feedback circuit is configured to receive a first feedback signal indicative of a first voltage dropped across the first resistor due to the first portion of the current when the second transistor shunts the current around the second resistor, and to receive a second feedback signal indicative of a second voltage dropped across the combination of the first resistor and the second resistor due to the second portion of the current when the second transistor does not shunt the current around the second resistor.

[0007] Some implementations relate to a method of inducing current through a load. The method includes receiving, at a control terminal of a transistor in a supply circuit, a signal for conducting current through the load to the transistor; having a feedback circuit in the supply circuit, coupled to the transistor, for controlling an amplitude of the current conducted by the transistor; receiving, in the feedback circuit, a first feedback signal from a first sense node located in a first current path through which at least a first portion of the current flows; receiving, in the feedback circuit, a second feedback signal from a second sense node located in a second current path through which at least a second portion of the current flows; and directing a second portion of the current around an impedance connected between the first sense node and the second sense node when the second feedback signal is received.

[0008] Some implementations relate to a camera including a housing, an imaging array for acquiring an image, the imaging array being mounted within the housing, and a supply circuit mounted within the housing for conducting a current pulse through a load that generates light to illuminate an object imaged by the imaging array during an image acquisition period of the imaging array. The image acquisition period includes a time interval during which one frame of image data is captured by the imaging array. The supply circuit can include a transistor arranged to conduct current through the load and a feedback circuit for applying a signal to the transistor to control an amplitude of the current conducted by the transistor. The feedback circuit can be configured to receive a first feedback signal from a first sense node located in a first current path through which at least a first portion of the current flows when the current flows through the load, and to receive a second feedback signal from a second sense node located in a second current path through which at least a second portion of the current flows when the current flows through the load and an impedance between the first sense node and the second sense node is bypassed by the second current path.

[0009] One implementation relates to a method of operating a camera. The method includes receiving, at a control terminal of a transistor in a supply circuit, a signal that conducts a current pulse through a load to the transistor; controlling, by a feedback circuit coupled to the transistor, an amplitude of the current pulse conducted by the transistor; receiving, within the feedback circuit, a first feedback signal from a first sense node located in a first current path through which at least a first portion of the current pulse flows; receiving, within the feedback circuit, a second feedback signal from a second sense node located within a second current path through which at least a second portion of the current pulse flows; directing, when receiving the second feedback signal, a second portion of the current pulse around an impedance connected between the first sense node and the second sense node; and acquiring, using an imaging array of the camera, a frame of image data of an object while the current pulse is being conducted through the load.

[0010] Of course, all combinations of the foregoing concepts and additional concepts discussed in more detail below (provided such concepts are not mutually inconsistent) are considered to be part of the subject matter of the invention disclosed herein. In particular, all combinations of the subject matter recited in the claims appearing at the end of this disclosure are intended to be part of the subject matter of the invention disclosed herein. Of course, terms explicitly employed herein that may also appear in any incorporated by reference disclosure should be given a meaning that most closely matches the particular concepts disclosed herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Those skilled in the art will understand that the drawings are mainly for illustrative purposes and are not intended to limit the scope of the subject matter of the present invention described herein. The drawings are not necessarily to scale, and in some instances, various aspects of the subject matter of the present invention disclosed herein may be shown exaggerated or enlarged in the drawings to facilitate understanding of different features. In the drawings, like reference characters generally refer to like features (e.g., functionally similar and / or structurally similar elements).

[0012]

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DETAILED DESCRIPTION OF THE INVENTION

[0013] The inventors recognized and understood that an effective way to control several loads (such as an LED-based lighting system used to facilitate imaging by a camera) is by driving a precisely controlled current through the load. In the case of an LED lamp, the light output is proportional to the current flowing through the semiconductor junction of the LED lamp. The number of photons generated is essentially proportional to the number of charge carriers crossing the bandgap, multiplied by the quantum efficiency (QE) of the LED lamp. Integrating the current provided to the LED lamp over the duration of a current pulse can result in the optical energy generated during the pulse. The optical energy is proportional to [Number] where T is the duration of the pulse and i c is the current supplied to the LED lamp.

[0014] An effective and safe way to supply a certain amount of light (e.g., a pulse of light) per event is to establish and maintain a constant current supplied to the LED lamp over an accurate period of time. When the current, and thus the light output, is controlled to be constant in either of the two cases, the variation in luminance between images can be ignored. In the first case, the duration of the illumination pulse T is longer than and covers the image acquisition period T i required by the camera to capture a frame of image data. In the second case, the image acquisition period T i is longer than T and there is no other illumination on the object over the light pulse. To facilitate imaging by the camera in either of these two cases, establishing a constant level of illumination during the light pulse avoids the mismatch between the timing of the light pulse and the exposure of the camera, thereby reducing the significant change in image luminance between images. Further, the power used by the system is reduced and the lamp life can be extended compared to the case where the lamp is continuously on and not strobed for each image acquisition.

[0015] A variety of LED-based lighting systems are available, some of which can be used for machine vision applications. These lighting systems can require a relatively wide range of different operating currents (e.g., currents ranging from about 100 milliamperes (mA) in some implementations to about 100 amperes (A) in other embodiments). The inventors have recognized and understood that there are several advantages in implementing an LED-based lighting system driver that can operate over a relatively wide current range while maintaining fast rise and fall times, but it is difficult to achieve accurate control of the current with a rapid response and to accommodate a wide range of reactive loads. In particular, undesirable levels of ringing and overshoot, as well as an increase in circuit complexity, can result when driving large currents to high-capacity loads through a wide range of (inductive) wiring and small currents through low-inductive wiring with a relatively low capacitance load using an adjustable gain within a feedback control circuit.

[0016] Conventionally, most lighting device vendors have avoided these problems by driving an LED lamp through a fixed resistor from a voltage source that is always on (generating a proportionally large amount of heat that must be wasted and dissipated), or by switching the power on and off by connecting the voltage source to the light source through a two-state switch (usually an FET that alternates between a saturated state or fully off). In both cases, the voltage of the power source and the value of the resistor must match each particular LED lamp. Another approach is to drive an FET or bipolar switch into saturation to turn the LED lamp on and off multiple times to achieve a target amount of light over a period of time. This approach has been applied to LED lighting for human viewing, but it is not suitable for most machine vision applications where a controlled amount of illumination must be applied at short time intervals when the target arrives at the correct position.

[0017] In view of the foregoing, the present invention generally relates to a system and method for accurately conducting a wide range of currents through loads that may have different current and voltage requirements. In one embodiment, a wide-range precision supply circuit can drive various different LED-based lighting systems over a relatively wide range of voltages and currents, and has accurate control over the current (pulse or continuous) provided to the LED-based lighting system (and hence, significantly accurate control over the brightness of the light provided by the LED-based lighting system).

[0018] In an exemplary implementation described in detail below, the inter-pulse brightness of the light provided by an LED-based lighting system controlled according to the system and method of the invention disclosed herein is particularly constant (e.g., about 1 / 1000 with respect to the amount of light generated between pulses). In one aspect, the current supplied to a reactive load (through an inductive cable to an LED lamp having a large capacitive load) may be overdamped, but still relatively fast, with rise and fall times of, for example, from about or exactly 1 microsecond (μs) to about or exactly 5 μs. An implementation example of the supply circuit of the system and method of the present invention can operate an LED-based lighting system that requires a voltage of about or exactly 5 volts (V) to about or exactly 100 V with a current of about or exactly 100 mA to about or exactly 100 A, although other voltage and current ranges are possible. The circuit topology described can be easily configured to drive high and low currents over a programmable voltage range.

[0019] In yet another aspect, the instantaneous power supplied to the current controller of the precision supply circuit implementing the systems and methods disclosed herein, and the thermal energy stored by the controller are monitored in real time, as well as the instantaneous power supplied to a load (e.g., an LED-based lighting system to which the supply circuit is connected) and the thermal energy accumulated, and the LED-based lighting system is maintained within an appropriate operating range specified by the user. The user can specify integration limits such that the total power and / or energy can be tracked over a specified integration interval. According to some implementations, the integration of the thermal energy stored in both the current controller and the load is performed repeatedly and continuously, evaluated for successive time intervals (e.g., every 1 microsecond), and can be compared to their respective operating limits. The integrated value of the energy consumed can provide information about the thermal load on the current controller and the load, which can be compared to user-specified thermal limits to maintain safe operation. In another aspect, the supply circuit reduces or interrupts current pulses and / or prevents future pulses until the thermal energy within the supply circuit and / or the LED-based lighting system is sufficiently dissipated to safely allow additional operation of the supply circuit and / or the lighting system.

[0020] 1. Wide Range Precision Supply Circuit FIG. 1 is a schematic circuit diagram of an example of a wide-range precision supply circuit 100 that can be used to supply an accurate amount of current (pulse or continuous) to a load 105 such as an LED lamp. In some implementations, a precise current pulse (e.g., an accurate time pulse having an accurate amount of current) can be supplied to the load 105 by the supply circuit 100. The precision supply circuit 100 can be roughly divided into three functional sections indicated by the dashed boxes. The first section includes a wide dynamic range, precision current controller 110 that controls the conduction of current through a load 105 such as an LED lamp. The second section includes a voltage monitor 140 that can monitor the instantaneous voltage across the load. The third section includes a programmable voltage source 170 (implemented as a buck converter in this example) for applying a voltage to the load at the output of the buck converter (sometimes called the "compliance voltage").

[0021] More specifically, the current controller 110 includes a first switch 112, an operational amplifier 120, a second switch 114, a shunt voltage reference 130, three transistors T2, T3, T4 (at least some of which may be field effect transistors or bipolar transistors), and other circuit elements connected as shown in FIG. 1. The current controller 110 utilizes feedback to the operational amplifier 120 (within the feedback circuit 125) to control the gate (or base) of the transistor T3 to conduct an accurate level of current (tens of milliamperes to 50 A in this circuit example) through the load 105 when connected to the precision supply circuit 100.

[0022] The feedback circuit 125 includes an operational amplifier 120, a transistor T2, and a second switch 114. The operational amplifier 120 outputs a signal applied to the control terminal (gate in this embodiment) of the transistor T3. Thus, the feedback circuit accurately controls the amplitude of the current conducted by the transistor T3. The voltage feedback signal can be obtained from one or both of the sense impedances (implemented as resistors R16, R18 in this embodiment) through which all of the current conducted through the majority (when transistor T3 has current leakage) or the load path passes. One or both of the sense resistors R16 and R18 can be implemented more generally as an impedance (e.g., as at least one resistor, or as a plurality of resistors connected in series and / or parallel), and can further include some inductance and / or capacitance. The sense resistors R16, R18 can be connected between the load 105 and a reference potential (grounded in the illustrated schematic, but can be a voltage in some implementations).

[0023] The sink current passing through load 105 can be initiated by applying a pulse-width modulation (PWM) signal (e.g., a high logic signal) to pin PWMI and then, optionally, applying a signal to the pin labeled FIRE in FIG. 1. The PWM signal passes through analog switch 112 and is applied to the non-inverting terminal of op-amp 120 (configured as a comparator). Op-amp 120 effectively compares the average voltage of the PWM pulse train (filtered by a low-pass RC filter after pin PWMI) with the voltage received from sense resistors R16, R18 and outputs a voltage that drives a voltage follower (implemented by transistor T2). The voltage follower drives the gate of transistor T3 into conduction. A logic high signal can be applied to pin FIRE, for example, to initiate the sink current for a short time interval (e.g., as short as 10 μs or less). Any pulse duration can be implemented in precision supply circuit 100, which can operate to continuously (e.g., in DC mode) sink current by leaving the logic high signal applied to pin FIRE. The amount of voltage applied to the gate (or base) of transistor T3 (and thus the amount of current flowing through transistor T3 when operating T3 within its linear range) can be controlled by adjusting the duty cycle of the PWM signal applied to PWMI.

[0024] The current controller 110 is arranged to pass current from the load 105 in the schematic diagram of FIG. 1, but in other implementations, the current controller may be arranged to supply current to the load. For example, the load can be placed between the transistor T3 and the reference potential (ground in this example), and the sense resistors R16, R18 can be moved to the drain side of the transistor T3 (e.g., connected in series between the supply voltage LED_CV and the drain of T3, or connected in series between T1 and T3 where the voltage across the resistor is differentially sensed). Other arrangements for sensing the current through the load using the sense resistors R16, R18 are possible as can be determined by one of ordinary skill in the art considering this specification. The choice of transistor T3 (e.g., n-channel and p-channel FETs, or npn-type and pnp-type BJTs) can depend on the polarity of the voltage supply used to supply voltage to the load and whether the current controller 110 is arranged to supply current to the load 105 or to sink current from the load 105.

[0025] In the first setting (programmable at pin ISEL), the transistor T4 is turned off and the second switch 114 is toggled to couple the inverting node of the op-amp 120 to the first sense node 126 (at the drain or collector of the transistor T3). In this configuration, at least a first portion of the current conducted through the load by the transistor T3 flows through both resistors R16 and R18 (along the first circuit path including the first sense node 126), and the sensed voltage is determined by the sum of the two resistance values (0.2 ohms in this example). In this configuration and circuit example, when the current flowing through the load swings from 10 mA to 5 A, the feedback voltage swings from 2 mV to 1 V, which is the same feedback voltage range for the high current setting.

[0026] In a second setting, transistor T4 can be turned on (conducted) so that resistor R16 is bypassed. At least a second portion of the current conducted through the load flows through T4 (along a second circuit path) instead of R16 and then through R18, which has a lower resistance value (0.02 ohms in this embodiment) than R16 (0.18 ohms). The second programmable setting can be made for high currents (e.g., currents exceeding 5 A). The same second setting can toggle second switch 114 to connect the inverting node of op-amp 120 between resistor R16 and resistor R18 in a second current path to a second sense node 124. By sensing the current flowing only through the lower resistance resistor R18, the feedback voltage is reduced to one-tenth compared to the current sensed at the first sense node 126 above R18, which senses the current flowing through both resistors R16 and R18. Thus, the range of the feedback voltage for large current variations can be reduced to keep op-amp 120 in the linear operating region. For this configuration and the exemplary circuit, current variations through a load of 100 mA to 50 A produce feedback voltage variations of 2 mV to 1 V.

[0027] In this way, op-amp 120 can be maintained in the linear operating range for a wide range of drive currents through transistor T3 without changing the gain of op-amp 120. This approach to controlling a wide range of currents also maintains the speed and slew rate of the op-amp such that the on and off times (measured as 90% on and 90% off in voltage) are about 5 microseconds or less for both the high current range and the low current range. By operating supply circuit 100 in the first setting with pin ISEL, when the controlled current is 5 A or more, the feedback voltage received at the inverting terminal of op-amp 120 is always 100 mV or more, resulting in a much faster slew rate of op-amp 120 and a load current through T3. Similarly, when operating in the second setting with pin ISEL, the same slew rate of op-amp 120 within feedback circuit 125 can be achieved for a current of 500 mA.

[0028] Of course, the approach for controlling a wide range of currents can be further extended. For example, another resistor can be added in series with resistors R16 and R18. Another bypass transistor (such as T4) can be added to shunt a third resistor. The second switch 114 can be replaced with a three-way switch, or another two-way switch can be added to the circuit. Another ISEL pin can be added to implement a third configuration where the inverting node of the op-amp 120 is connected to a third node where the detected voltage is the sum of all three resistors.

[0029] The precision supply circuit 100 can operate without T4, without a circuit path to bypass resistor R16, and without the second switch 114. In such an implementation, when sensing is performed at the second sensing node 124, power may be unnecessarily consumed by R16, and the accuracy of current control may decrease.

[0030] Another feature of the current controller 110 is that when the load 105 (e.g., an LED lamp) is off, the transistor T3 can be biased to provide a small quiescent current or standby current to the transistor T3. This allows the load 105 to be completely off (e.g., the current flowing through the load is negligibly small or no current is flowing) while keeping the transistor T3 in a standby state with the gate capacitance charged. Maintaining the transistor in a ready (slightly conducting) state shortens the time required to fully turn on the transistor T3 to conduct the current commanded through the load 105. The shunt voltage reference 130 is disposed within the current controller 110 (having the transistor T1 and resistors R7 and R9) to act as a current source 133 using the output from the programmable voltage source 170 (LED CV). This current source can supply a small current (less than 100 mA) to the transistor T3 when the current through the load 105 is interrupted, maintaining the transistor T3 in a ready state to be constrained in the on state.

[0031] Further, toggle the first switch 112 (via pin FIRE) to connect the non-inverting input of the operational amplifier 120 to the fixed reference voltage V ref provided by the voltage divider 108. The value of V ref can be selected to supply a sufficient bias voltage to the gate (or base) of the power transistor T3 such that the transistor T3 draws only a small quiescent or standby current (supplied from the programmable voltage source 170). This bias voltage and quiescent current keep the power transistor from turning completely off and in a ready state so that when the next firing command is received via pin FIRE, the power transistor can quickly slew to the on state.

[0032] For circuit implementation, the first switch 112 and the second switch 114 can be analog switches such as the single-pole double-throw analog switch SN74LVC1G3157DCKR available from Texas Instruments in Dallas, Texas. The operational amplifier 120 can be, for example, the precision operational amplifier OPA192 available from Texas Instruments in Dallas, Texas. The shunt voltage reference 130 can be, for example, the integrated circuit LM4041 available from Texas Instruments in Dallas, Texas. The power transistor T3 can be the PowerTrench® MOSFET FDT86102LZ available from onsemi in Phoenix, Arizona, but other types of transistors including bipolar transistors can be used. The transistor T4 can be, for example, other types of transistors including bipolar transistors, but can be the PSMN0R7-25 series of MOSFETs available from Nexperia in Nijmegen, the Netherlands. The transistor T1 can be, for example, the BC856 series of transistors available from Nexperia in Nijmegen, the Netherlands. During the idle state of the transistor T3, since the current supplied through the transistor T1 is small, the maximum rated current of the transistor T1 can be a fraction (e.g., 1 / 10 to 1 / 100 of the maximum rated current of the transistor T3).

[0033] The precision supply circuit 100 also includes a programmable voltage source 170. In the exemplary embodiment of FIG. 1, the programmable voltage source 170 comprises, in part, a buck converter based on a controller chip 175 (e.g., model LMR16006 available from Texas Instruments, Dallas, Texas) and an inductor L1. The buck converter reduces an input DC voltage (HVP provided to the input pin of the controller chip) to a lower voltage determined by the duty cycle of a PWM signal applied to pin PWM_V. The applied PWM signal controls the duty cycle of the current switching through the inductor of the buck converter and thus determines the output voltage from the programmable voltage source 170. Other types of programmable voltage sources can be used in other cases (e.g., programmable buck-boost converters, programmable flyback converters). The converter can be turned on and off with a signal applied to pin CV_EN. The exemplary programmable voltage source 170 is configured to output a compliance voltage of approximately or exactly 5 volts to approximately or exactly 50 volts, although other ranges of output voltages are possible. The programmable voltage source 170 also provides an adjustable current limit via pin ILM that controls the feedback voltage applied to the feedback input of the controller chip.

[0034] The voltage monitor 140 of the precision supply circuit 100 can monitor the voltage at the output of the load 105 (e.g., an LED lamp) at high frequency, and thus can essentially track momentary voltage drops across the load during circuit operation. An exemplary voltage monitor 140 uses a high-speed analog-to-digital converter (ADC) 145 (e.g., model AD7274 available from Analog Devices of Wilmington, Massachusetts) to sample a voltage indicative of the voltage at the output of the load (e.g., the voltage at the cathode of the LED lamp in the exemplary example). A voltage divider 150 can be used to scale the sampled voltage to a range detectable at the input to the ADC 145. The ADC can sample and transmit the detected voltage value at a rate of 1 per microsecond (via pin SDATA). The sampling data rate can be determined by a clock signal provided to the clock input of the ADC 145 (via pin SCLK), and the data transmission rate can be determined by a signal applied to the select input (via pin CSn). The momentary power supplied to and dissipated by the load can be repeatedly calculated (for a series of samples obtained by the ADC 145) using the product of the programmed compliance voltage and the programmed current multiplied by the difference between the voltage measured at the sense node 126 or sense node 124. If the current that the load can pass at the programmed voltage is less than the programmed current, the momentary power value calculated as described is at least an upper limit on the actual power dissipated within the load, which results in the worst-case result for a conservative estimate of the momentary power.

[0035] The ADC 145 directly monitors the voltage drop across the precision current controller 110 in order to monitor the voltage at the output (or low voltage side) of the load. The voltage drop obtained by multiplying the programmed current across the current sense resistor R18 (when T4 is conductive) and resistors R16 and R18 (when T4 is off) provides the power dissipated in the resistor. Or, if the load cannot pass the programmed current at the programmed voltage, the calculated power will be, at worst, the upper limit of the actual power dissipated in the resistor. The on-resistance of the power transistor T4 can be ignored when T4 is on. The voltage obtained by subtracting the voltage drop across the resistor from the measured voltage is the actual voltage across T3. By monitoring and calculating a single voltage at the load output, several useful pieces of information can be obtained: (1) the voltage drop and power across the load; (2) the voltage drop across the power transistors T3 and T4 and the current sense resistor; (3) the upper limit of the current flowing through the power transistors T3 and T4 and the current sense resistor; (4) the upper limit of the current flowing through the load; (5) the upper limit of the power supplied to the load; (6) the upper limit of the power supplied to the power transistors.

[0036] 2. Lighting and Image Acquisition System FIG. 2 shows the implementation of the precision supply circuit 100 in the LED lighting and image acquisition system 200. The system 200 includes a supply circuit 100 communicatively coupled to a controller 210 and arranged to strobe an LED lamp (load 105). The system further includes a camera 220 arranged to photograph an object 230 that may pass by the camera 220 on a conveyor 240. Such LED lighting and image acquisition systems 200 may be implemented in a manufacturing facility (e.g., for component inspection) or may be part of a more complex automatic control system.

[0037] The controller 210 can be implemented using at least one processor (such as a microcontroller, a field programmable gate array (FPGA), a programmable logic controller (PLC), an application specific integrated circuit (ASIC) microprocessor, a digital signal processor (DSP), or some combination thereof). The controller 210 can provide signals for controlling the supply circuit 100 (for example, program the voltage applied to the load (at the output pin LED_CV) and conduct or terminate the conduction of the current through the load (via transistor T3 in FIG. 1)). The controller 210 can also receive signals from the supply circuit 100 (for example, receive a serial data signal from an ADC 145 representing the almost instantaneous voltage measured at the output of the load). The controller 210 can also provide signals to the camera 220 (for example, to control the acquisition of an image) and receive image data from the camera 220. In some cases, the controller 210 can be implemented at least in part as described in U.S. Patent No. 9,459,607, entitled "Methods, Apparatus, and Systems for Monitoring and / or Controlling Dynamic Environments," issued on October 4, 2016, which is hereby incorporated by reference in its entirety. In some cases, an intermediate circuit can be used between the controller 210 and the supply circuit 100, such as the flexible input-output circuit described in U.S. Patent No. 11,182,326, entitled "Input / Output Apparatus and Methods for Monitoring and / or Controlling Dynamic Environments," issued on November 23, 2021, which is hereby incorporated by reference in its entirety. In some cases, the intermediate circuit can also be included within the camera 220.

[0038] The controller 210 may include a system clock and / or other circuitry used to synchronize operations through the illumination and image acquisition system 200. For example, the controller 210 may determine the start time and duration of the pulses applied to the pin FIRE of the current controller 110 (e.g., turning on the LED lamp for short or long time intervals) based on the clock cycle of the system clock or the exposure settings set in the circuitry of the camera. The controller 210 can adjust the image acquisition by the camera 220 with the emission of the LED lamp using conventional logic circuitry, trigger the image acquisition in response to the emission of the LED lamp, or emit the LED lamp in response to the start of the image acquisition. In some cases, the emission of the LED lamp and / or the image acquisition may be based on an event detected by the illumination and image acquisition system 200. An exemplary event may be the arrival of a part or object transported on a conveyor at a specific location.

[0039] The figure of FIG. 2 illustrates the supply circuit 100 separated from the camera 220, but the present invention is not so limited. In some implementations, the supply circuit 100 may be included on a printed circuit board (PCB) that can be mounted within the housing of the camera 220, and the camera may be very compact in size (e.g., measuring 50 mm × 50 mm × 50 mm or less). Such a compact camera 220 is illustrated in FIGS. 3A and 3B. The housing may include an imaging array, its associated operating and readout electronics, and two supply circuits 100 for driving two loads 105 (e.g., two LED lamps). For example, the camera 220 may house the supply circuit 100 and have two outputs (LED_CV1, LED_CATH1), (LED_CV2, LED_CATH2) that are spaced apart or synchronized to provide more uniform illumination of the object 230, or to provide different illumination views of the same object 230, and can drive two LED lamps (a second output and lamp not shown in FIG. 2).

[0040] Referring to the front perspective view of FIG. 3A, camera 220 may include a housing 221 to which an imaging array 222 is attached behind a lens mount 224 for a lens assembly 225 (depicted in FIG. 2). The housing can be made of metal, plastic, or a combination thereof. The imaging array 222 may be a CCD or CMOS 2D imaging array and can include any number of pixels (e.g., 10,000 to 4,000,000 or more). The imaging array 222 can be attached on a PCB fixed within the housing 221. The imaging array and electronics on the PCB can include, among other functions, circuitry to power transistors that operate pixel readout and reset, receive an external trigger signal, receive pixel data buffer and frame data for transmission, and transmit data. The lens mount can be a 25 mm threaded CS mount, although other types of lens mounts can be used.

[0041] The back of camera 220 shown in the rear perspective view of FIG. 3B can include one or more connectors for attaching wiring and / or cables (e.g., for power, programming, and communication with controller 210) to the camera. In the illustrated example, two first connectors (e.g., M8 female connectors) and one second connector (e.g., RJ45 connector) are attached to the rear side of camera 220, although other types of connectors can be used. Power over Ethernet (POE) can be provided through the second connector 228 and used to communicatively couple camera 220, precision supply circuit 100, and controller 210, as well as other devices, or some combination thereof. At least one second connector 227 can be connected via wiring to a remotely located load 105 (e.g., an LED lamp). The housing 221 can include a mounting mechanism (e.g., screw holes 229) for fixing the camera 220 to a fixed mount.

[0042] 3. Power Limitation When the supply circuit 100 of FIG. 1 is implemented in a control system as shown in FIG. 2, it enables circuit protection for the load and the power transistors T3, T4. As described in connection with FIG. 1, monitoring the voltage at the output of the load provides several useful information that can be used to protect the load and the power transistors from excessive power losses that can degrade these devices. As described above, the ADC 145 can continuously output the voltage value (CV_CATH) monitored almost instantaneously at the output of the load. These voltage values relate to (1) the voltage drop across the load, (2) the voltage drop across the power transistors T3, T4 and the current sensing resistors, (3) the current flowing through the power transistors T3, T4 and the current sensing resistors, (4) the current flowing through the load, (5) the power supplied to the load, and (6) the power supplied to the power transistors, providing almost instantaneous information about them.

[0043] One aspect of the current controller 110 is that the current I flowing through the sense resistors R16, R18 R is essentially programmed or set by the input applied to the pin PWMI. The operational amplifier 120 in the feedback circuit 125 forces the voltage at the inverting terminal of the operational amplifier 120 to be the same as the voltage at the non-inverting terminal, which is the average voltage of the PWM signal applied to the pin PWMI (in the exemplary circuit of FIG. 1). Since the voltage at the inverting terminal of the operational amplifier 120 is the voltage sensed and dropped across the sense resistors R16, R18, the average voltage of the PWM signal essentially programs the current I flowing through the sense resistors according to Ohm's law. R to program.

[0044] The almost instantaneous voltage drop V across the load L (item 1 above) can be determined from the following.

Equation

[0045] Then, the almost instantaneous power P L (item 6 above) can be approximated using EQ.1.

Equation

[0046] The almost instantaneous power P T supplied to the power transistor can be approximated as follows.

Equation

[0047] The almost instantaneous values of V -L , I R , P -L , and P T can be repeatedly calculated by the controller 210, for example, in real - time (e.g., every few microseconds), as the current is conducted through and ends in the load 105. The controller 210 can also calculate the energy accumulated per pulse E p applied, which is the product of the power and the pulse duration t p on a per - pulse basis.

Equation

Number

[0048] Power transistors T3, T4 (P T3、lim , P T4、lim , ET T3、lim , ET T4、lim ) and the power and / or energy limits of the load (P L、lim , E L、lim ) can be stored in a memory accessible by the controller 210. These limits can be defined to enable the cooling characteristics of the precision supply circuit 100, as well as the cooling characteristics of its power transistors T3, T4, and the load 105. Using these parameters, controller logic can be instantiated to inhibit the current pulse to the load when the power and / or energy limit is exceeded. For example, the controller can continuously compare the calculated power and / or energy supplied to each of the load and the power transistor with their corresponding power and / or energy limits, and inhibit the current output to the load 105 to prevent exceeding any power and / or energy limit.

[0049] In further detail, and according to one implementation, the 18×18 binary multiplier within the controller 210 can be used to multiply the products calculated in one or more of the EQs. Using EQ.2, EQ.3, EQ.4, and EQ.5, the power and energy levels supplied to the load 105 and the power transistors T3, T4 are determined. In some cases, the binary values received from the ADC 145 may be encoded in units of voltage × 256, and the binary-calculated current may be encoded in units of milliamperes. In such cases, the upper 28 bits of the result of the 18×18 binary multiplier represent the instantaneous power or energy dissipated by the power transistor or the lamp (milliwatts), depending on whether the multiplication is performed on the transistor or the lamp (milliwatts). If the maximum lamp supply voltage is less than 128 VDC, since the maximum possible value is less than 1024 watts, only bits [27..8] of the 18×18 multiplication product may be used.

[0050] Every microsecond the supply circuit 100 is activated, the almost instantaneous power (P L and / or P in milliwatts T ) is accumulated, and the resulting sum represents the accumulated energy in nanojoules (nJ). The real-time cumulative energy E L of the load 105 can be represented by the following equation.

Equation

[0051] Energy is also thermally dissipated from the load 105 and the power transistors T3, T4, so the stored energy in EQ.7 can be modified to account for the thermal dissipation of energy by each device. The thermal output dissipation rate of each device depends on several factors such as the thermal conductivity between the device and the surrounding environment and the temperature of that environment. The thermal output dissipation rate can be characterized as the thermal dissipation output rating P d for each device. The thermal dissipation output rating varies depending on how the device is physically implemented and what the expected maximum temperature of the environment is. The thermal dissipation output rating can be determined empirically for each device, obtained theoretically, or obtained from the device specifications for different device applications. In the case of one exemplary camera 220 and the contained precision supply circuit, the thermal dissipation output rating was found to be approximately 500 mW for the power transistors T3, T4. Since thermal cooling always occurs, the controller 210 subtracts the stored thermal dissipation energy from the stored energy supplied to the device at each calculation interval to determine the net energy level E n in the device at any given time. The calculation of the load is as follows.

Equation

[0052] To protect the device, the controller 210 can compare the stored energy limit of the device with the corresponding current value of the device's net energy (e.g., En L- compared to the E of load 105 L,lim ). If the net energy current value is equal to and / or exceeds the energy limit of the device, the controller can stop inducing current through the load until the net energy current value drops below the energy limit. Since the comparison can be made for each calculation cycle, the controller 210 can reduce or stop the conduction of current by transistor T3 before reaching the intended duration at the initial stage of the current pulse.

[0053] The heat dissipation output rating and energy limit can be set as conservative values so that the load temperature or transistor temperature does not rise to the point where the device's lifespan is significantly reduced. A control system incorporating the supply circuit and protection features described above makes it substantially impossible to damage the supply circuit 100 or the load by overdriving the circuit or the load. As an example, the power transistors T3, T4 are protected even when a wiring misconnection lamp cable directly connects the positive rail from the programmable voltage source 170 to the drain of the power transistor T4 and the circuit is fired to conduct current through the transistor.

[0054] 4. Examples of Circuit Performance The precision supply circuit 100 is configured according to the circuit of FIG. 1. The circuit is arranged to sink a 14 - ampere current passing through the LED lamp during a pulse duration of about 100 microseconds applied to the gate of transistor T3. The trace 401 of the current pulse from the lamp is shown in FIG. 4A. The trace was 410 obtained by measuring the voltage across a 0.45 - ohm resistor connected to the cathode of the lamp.

[0055] Trace 401 exhibits an overdamped behavior, showing almost no overshoot (less than 4%) throughout the entire plateau of the pulse and a very uniform current. The amplitude of the current along the plateau changes by less than 2% after a small overshoot so that the current remains constant (within 2% between peaks) for approximately 88% of the pulse duration. In some implementations, the current remains constant (within 5%, 2%, or 1%) for 85%, 90%, or even 95% or more of the pulse duration, depending on the level of the current switched through the load 105 and the components selected for the current controller 110.

[0056] Figure 4B plots two oscilloscope traces 401, 403 (overlay) of a 14 A current pulse acquired at two different times. The same parameters (e.g., programmable voltage, pulse duration, etc.) were set to operate the supply circuit 100. The overlap shows a very high accuracy and reproducibility of the two pulses, indicating the consistency of the current and the consistent optical control by the precision supply circuit 100. The reference trace 401 (blue) is overlaid on the later acquired trace 403 (white). The later acquired trace 403 is almost completely offset from the reference trace 401. Only the ambient noise picked up by the scope ground lead allows any of the later acquired traces 403 to be seen. The between-pulse uniformity of the current (and the optical exposure of the LED lamp driven by the current) can be at least 1 part in 1000, up to 1 part in 10,000, or up to 1 part in 100,000.

[0057] 5. Alternative Implementations There are other ways to implement the functionality of the precision supply circuit 100 of FIG. 1. FIG. 5 is a circuit schematic diagram of another example of a supply circuit 400 that continuously monitors the voltage on the low voltage side of the load (e.g., at the cathode of an LED lamp). The supply circuit 400 includes sections similar to those identified in the supply circuit 100 of FIG. 1, but implemented with different circuits for some of the sections. For example, the supply circuit 400 includes a current controller 410, a voltage monitor 440, and a programmable voltage source 470. The programmable voltage source 470 is similar to the programmable voltage source 170 of FIG. 1 and includes a buck converter.

[0058] The current controller 410 includes a single current sense resistor (e.g., an LED lamp that can be connected to the circuit via connector 478) that provides feedback to the operational amplifier 420 in order to accurately control the current level conducted through the load 105. The input to the operational amplifier 420 can be switched (using analog switch 412) between a first PWM input that directly passes through the digital isolator 402 to control the amount of current conducted to the power transistor T3 and a second programmable PWM source built into the current controller 410 for the standby mode of the transistor T3. The programmable PWM source includes two dual-triggerable monostable multivibrators 416 (e.g., model 74AHC123 available from Texas Instruments, Dallas, Texas), a 128-tap linear tapered digital potentiometer 418 (e.g., model MAX5128 available from Analog Devices), and an operational amplifier 422.

[0059] The voltage monitor 440 employs a voltage-to-frequency conversion circuit 442 having a timer 445 (e.g., model LMC555 available from Texas Instruments, Dallas, Texas) to convert the voltage from the bias circuit 430 to the frequency of the oscillation signal output from the timer 445. The output from the timer 445 can be returned to the controller 210 to determine the voltage at the output of the load.

[0060] More specifically, a frequency that is inversely proportional to the voltage LED_CATH in the output of the load is applied onto the feedback signal line 443 by circuit elements within the current controller 410. The voltage-frequency transfer function depends on the characteristics of these circuit elements and thus may depend on the intended use of the precision supply circuit 400. For example, a supply circuit 400 that operates over a wide voltage range may have component values that are quite different from those of a supply circuit 400 that operates over a much narrower voltage range.

[0061] In order for the controller 210 to appropriately determine the voltage for the implementation of any given supply circuit 400, parameters representing a particular supply circuit 400 for a given device are stored in non-volatile memory and can be acquired by the controller 210 upon power-up so that the voltage-frequency conversion can be correctly calculated.

[0062] For example, a linear approximation of the voltage in the form y = mx + b may be used to convert the feedback signal frequency to the voltage on the drain of the power transistor T3. However, depending on the characteristics of the devices in the circuit, the slope and offset of this linear approximation can vary.

[0063] In one exemplary implementation represented in FIG. 6, the voltage at the drain of the power transistor T3 has a non-linear dependence on the measured period (by the timer 445) of the oscillatory signal from the voltage-frequency conversion circuit. FIG. 6 shows a linear approximation to the curve, resulting in a slope of 0.4285 and an offset of -23.406.

[0064] In an exemplary controller 210 such as an FPGA, the period of each cycle of the oscillating voltage-frequency signal can be measured in units of 40 nanoseconds (ns). If the application requires a maximum lamp voltage of 48 VDC, the frequency range can be from 125 kHz to 500 kHz and the period can be in the range from 2 μs to 8 μs. Thus, the maximum period in 40 ns increments can be made 200, and therefore the period value can be represented as an 8-bit binary value in the signal from the timer 445 and in the controller logic.

[0065] Since the voltage calculation involves multiplying by a slope over a period, the controller can include a binary multiplier that can operate at a frequency of 200 MHz embedded in the silicon fabric. While a floating-point multiplier uses valuable logic resources and can operate at a much lower frequency, a binary multiplier is used to calculate the output load voltage V CA as V × 256 (not V), which makes sense.

Number

[0066] Therefore, in this exemplary case of FIG. 6, the slope value of the multiplication can be 256 × 0.4285, or 110, and the offset value can be 256 × -23.406, or -5992. The slope value can be stored in 1 byte of the controller's non-volatile memory, and the offset value can be stored in 1 word of the controller's non-volatile memory.

[0067] In the controller logic, the start of a new cycle of the oscillating voltage-frequency signal is determined by detecting the rising edge of the signal. The period is measured by incrementing a counter in timer 445 every 40 ns. When the start of a new cycle is detected, the counter value is latched into the period register and the counter is reset to zero. A 9×9 binary multiplier can be used to multiply the period register value by the slope value. Next, a 16-bit adder can be used to add the offset value, resulting in a binary value that is approximately 256 times the voltage at the drain of power transistor T3. In this way, the voltage determination can be performed using relatively few resources. For the voltage monitor 140 in FIG. 1, the voltage at the drain of power transistor T3 is essentially measured directly, converted to a binary value by ADC 145, significantly simplifying the voltage monitor circuit.

[0068] 6. Host Interface There are various parameters, data, flags, settings, etc. that can be established between the controller 210 so as to interface with the above-described precision supply circuit and the camera 220. Some examples of such interface information are described below. 6.1 Configuration

[0069] At least some of the parameters in Table 1 and / or other protection parameters can be stored in the non-volatile memory of the controller 210 (such as the protection parameter register shown in Table 2, although more or less information can be included in the register than is listed in the table). These parameters can be instantiated separately for each precision supply circuit within the system. In the camera, only the flag, CVmin, and Cvmax parameters can be instantiated separately, and the remaining parameters can be shared. [Table 1] [Table 2]

[0070] Bits 1..0 of the flags parameter indicate which protections are incorporated into the precision supply circuit channel. Bit 2 of the flag parameter indicates whether the LampCooling and LampThresh values received by the device are linearly encoded (in the ranges of 65.535 watts and 274.877 joules respectively), or exponentially encoded (in the ranges of 1048 watts and 4,397,777 joules respectively). Setting bit 3 indicates that the precision supply circuit supports an adjustable compliance rail, and setting bit 4 indicates whether the precision supply circuit information is included in the statistical packet (for cameras only). The remaining flag bits can be reserved. Table 3 provides examples of configuration flags, but the configuration flags may be more or less than those described in the table. [Table 3]

[0071] In an exemplary camera, the shared protection parameters (Vslope, Voffset, FET cooling, and FETthresh) start at byte offset 199 of the configuration page, the flag parameter (flag) can be stored at byte offset 206 of strobe controller 0, can be stored at byte offset 207 of strobe controller 1, and the Cvmin and Cvmax parameters can be stored at byte offsets 208 and 210 of strobe controllers 0 and 1 respectively. 6.2 Comparison

[0072] Certain device protection values can be set by controller 210 through the write function requirements to the precision supply circuit. The corresponding control parameters can be added to word offsets 10 - 12 of the write feature request payload as illustrated in Table 4, but may contain more or less information than that listed in the table.

Table 4

[0073] The LampCooling and LampThresh parameters can be linearly encoded or exponentially encoded depending on the configuration of the precision supply circuit. In a linear configuration, the LampCooling parameter can be represented in mW (in the range of 0 to 65.535 watts), and the LampThresh parameter can be represented in increments of 4.194303 mJ (in the range of 0 to 274.87371264 joules). In an exponential configuration, the upper 2 bits indicate power and can enable power values of ×1, ×4, ×16, and ×64. For example, a power value of ×64 indicates that the LampCooling parameter is represented in increments of 64 mW (in the range of 0 to 1048.512 watts), and the LampThresh parameter can be represented in increments of 268.435392 mJ (in the range of 0 to 4,397.778075648 joules).

[0074] Furthermore, by using bit 1 of the ISCmode register, an alarm event from the precision supply circuit can be sent to the load not only when the LampThresh or FETthresh energy threshold is exceeded, but also at the end of each current pulse. By using bit 2 of the ISCmode register, lamp protection can be enabled. By using bit 3 of the ISCmode register, the lamp can be activated for setup purposes. 6.3 Status

[0075] The protection parameters and status can be read by the host controller 210 using the read feature request. The write feature parameters are read from the same offset assigned in the write feature payload. The non-volatile configuration parameters can be read using the read feature request for non-volatile memory transfer. Additional data from the control circuit can be included in word offsets 13 to 20 of the read feature request payload as shown in Table 5, although more or less information may be included than that listed in the table.

Table 5

[0076] 6.4 Alarm When the precision supply circuit is stopped to exceed the energy threshold, a notification in the form of an event packet can be sent by the precision supply circuit to the controller 210. For the camera, the alarm event of the first precision supply circuit housed in the camera 220 can be sent using the event transmission port of index 2 (previously reserved), and the alarm event of the second precision supply circuit housed in the camera 220 can be sent using the event transmission port of index 3 (previously reserved). In some implementations, the alarm event can be sent using the event transmission port of index 14. The target MAC, event ID, etc. can be determined by the setting of the Tx descriptor of the assigned port. If the target MAC address is not assigned, the event packet is not sent.

[0077] The alarm event payload can be defined as shown in Table 6, but can include more or less information than that listed in the table.

Table 6

[0078] The almost instantaneous power calculated by the load 105 (e.g., LED lamp) and / or the power transistors T3, T4 can be expressed in units of 1 mW, but other units are also possible, and the unit t of the lamp and the transistor may be different. The calculated energy of the load transistor and / or the power transistor can be expressed in units of 64 nJ, but other units are also possible, and the units of the lamp and the transistor may be different.

[0079] 6.5 Statistics A camera having one or more internal precision supply circuits can be configured to include information regarding the operation of the circuits within a camera statistics packet. The statistics packet can be transmitted, for example, at the end of each image acquisition or after a sequence of image acquisitions. The statistics packet data can include at least some alarm event payload data, such as a pulse duration t p (the on-time of T3 for passing current through load 105). Examples of the statistics packet data are shown in Table 7, but more or less information than that listed in the table can be included in the packet.

Table 7

[0080] The precision supply circuits 100, 400, and the method of operating the precision supply circuits can be implemented in various ways, some of which are listed below.

[0081] (1) A supply circuit (100) comprising a transistor (T3) arranged to conduct current through a load (105) and a feedback circuit (125) for applying a signal to the transistor (T3) to control the amplitude of the current conducted by the transistor, wherein the feedback circuit receives a first feedback signal from a first sensing node (126) located in a first current path through which at least a first portion of the current flows when the current flows through the load, and receives a second feedback signal from a second sensing node (124) located in a second current path through which at least a second portion of the current flows when the current flows through the load, and is configured such that when an impedance (R16) between the first sensing node and the second sensing node is bypassed by the second current path, the impedance (R16) between the first sensing node and the second sensing node is bypassed by the second current path.

[0082] (2) The feedback circuit includes an operational amplifier (120) for receiving a first feedback signal and a second feedback signal, and a switch (114) for connecting the first sensing node or the second sensing node to the first input terminal of the operational amplifier, in the supply circuit of configuration (1).

[0083] (3) The switch is a first switch, and the supply circuit of configuration (2) further includes a second switch (112) for connecting the second input terminal of the operational amplifier to a first input (PWMI) configured to receive a pulse width modulation signal or a second input (108) arranged to provide a fixed voltage.

[0084] (4) The supply circuit of configuration (3) further includes a current source (133) coupled to a transistor, where the fixed voltage causes a standby current to flow from the current source through the transistor and little or no current flows through the load.

[0085] (5) The impedance is a first impedance, and the supply circuit of configuration (2) or (3) further includes a second impedance (R18) connected in series with the first impedance and located between the second sensing node and the reference potential.

[0086] (6) The supply circuit of configuration (5), where the second impedance is smaller than the first impedance.

[0087] (7) The feedback circuit in the supply circuit according to any one of configurations (1) to (6) that controls the amplitude of the current to be constant within 2% for at least 85% of the pulse during which the current is conducted through the load by the transistor.

[0088] (8) The transistor (T3) is a first transistor, and the supply circuit according to any one of configurations (1) to (7) further includes a second transistor (T4) configured to be formed within a second current path and bypass a second portion of the current within the second current path.

[0089] The supply circuit according to any one of configurations (1) to (8), further comprising a programmable voltage source (170) for applying a voltage to a load.

[0090] (10) The supply circuit according to configuration (9), wherein the programmable voltage source includes a buck converter.

[0091] (11) The supply circuit according to any one of configurations (1) to (10), further comprising a voltage monitor (140, 440) for detecting a voltage at the drain or collector of a transistor.

[0092] (12) The supply circuit according to configuration (11), wherein the voltage monitor includes an analog-to-digital converter (145) for sampling the voltage.

[0093] (13) The supply circuit according to configuration (11), wherein the voltage monitor includes a voltage-to-frequency circuit (442) and a timer (445) for detecting the voltage.

[0094] (14) The supply circuit according to configuration (11) in combination with a controller (210), wherein the controller repeatedly receives from the voltage monitor a signal indicating the voltage at the drain or collector during a measurement interval including at least one sampling interval of a sequence of sampling intervals, calculates the power supplied to the load during the measurement interval based at least in part on the received signal, and calculates the power supplied to the transistor based at least in part on the received signal.

[0095] (15) The combination according to configuration (14), further configured such that the controller accumulates a plurality of calculated powers supplied to the load to at least partially determine a current energy level of the load, compares the current energy level of the load with an energy limit of the load, and stops inducing current through the load by the transistor when the current energy level of the load exceeds the energy limit of the load.

[0096] (16) The combination of configuration (15) in which determining the current energy level of the load includes, by the controller, taking into account the heat output dissipation rate of the load.

[0097] (17) A supply circuit (100) comprising a first transistor (T3) arranged to conduct current through a load (105), a first resistor (R18) in a first circuit path through which at least a first portion of the current flows, a second resistor (R16) connected in series with the first resistor through which at least a second portion of the current flows when connected to the load, a second transistor (T4) arranged to shunt current around the second resistor, and a feedback circuit (125) for receiving a first feedback signal indicative of a first voltage dropped across the first resistor due to the first portion of the current when the second transistor shunts current around the second resistor, and for receiving a second feedback signal indicative of a second voltage dropped across the combination of the first resistor and the second resistor due to the second portion of the current when the second transistor does not shunt current around the second resistor.

[0098] (18) The supply circuit of configuration (17) wherein the feedback circuit comprises an operational amplifier (120) for receiving the first feedback signal from a first sensing node (124) at a terminal of the first resistor, a second feedback signal from a second sensing node at a terminal of the second resistor, and a switch (114) for coupling the first sensing node or the second sensing node to a first input terminal of the operational amplifier.

[0099] (19) The supply circuit of configuration (18) further comprising a second switch (112) wherein the switch is a first switch and the second input terminal of the operational amplifier is connected to a first input (PWMI) arranged to receive a pulse width modulation signal or a second input (108) arranged to provide a fixed voltage.

[0100] Further comprising a current source (133) coupled to the transistor, the supply circuit of configuration (19) in which a fixed voltage causes a standby current to flow from the current source to the transistor and the current flowing through the load is negligible or non-existent.

[0101] (21) The supply circuit of any one of configurations (17) to (20), wherein the second resistor is smaller than the first resistor.

[0102] (22) The supply circuit according to any one of configurations (17) to (21), wherein the feedback circuit controls the amplitude of the current to be constant within 2% for more than 85% of the pulse during which the current is conducted through the load by the transistor.

[0103] (23) The transistor (T3) is the first transistor, and the supply circuit further comprises a second transistor (T4) configured to be within a second current path and configured to bypass a second portion of the current within the second current path, according to any one of configurations (17) to (22).

[0104] (24) The supply circuit according to any one of configurations (17) to (23), further comprising a programmable voltage source (170) for applying a voltage to the load.

[0105] (25) The supply circuit according to any one of configurations (17) to (24), further comprising a voltage monitor (140, 440) for detecting the voltage at the drain or collector of the transistor.

[0106] (26) A supply circuit of any one of configurations (17) to (25) combined with a controller (210), wherein the controller repeatedly, for a sequence of sampling intervals, during a measurement interval including at least one sampling interval of a series of sampling intervals, receives a signal from a voltage monitor indicating a voltage at a drain or collector, calculates the power supplied to a load based on the measurement interval, calculates, at least in part, the power supplied to the transistor on the received signal, and is configured to calculate the power supplied to the transistor, at least in part, based on the received signal.

[0107] (27) The controller accumulates a plurality of calculated powers supplied to the load to at least partially determine a current energy level of the load, compares the current energy level of the load with an energy limit of the load, and is further configured to interrupt the induction of current through the load by the transistor if the current energy level of the load exceeds the energy limit of the load, in the combination of configuration (26).

[0108] (28) A method of conducting current through a load, the method comprising: receiving, at a control terminal of a transistor (T3) in a supply circuit, a signal for conducting current through the load to the transistor; controlling, by a feedback circuit (125) in the supply circuit and coupled to the transistor (T3), an amplitude of the current conducted by the transistor; receiving, in the feedback circuit, a first feedback signal from a first sensing node (126) located in a first current path through which at least a first portion of the current flows; receiving, in the feedback circuit, a second feedback signal from a second sensing node (124) located in a second current path through which at least a second portion of the current flows; and directing a second portion of the current around an impedance (R16) connected between the first sensing node and the second sensing node when the second feedback signal is received.

[0109] (29) The feedback circuit includes an operational amplifier (120) and a switch (114), and the method further includes receiving a first feedback signal or a second feedback signal at a first input terminal of the operational amplifier, coupling the switch and a first sensing node to the first input terminal to receive the first feedback signal, and coupling the switch and a second sensing node to the first input terminal to receive the second feedback signal, the method of configuration (28).

[0110] (30) The switch is a first switch, and the method further includes coupling a second switch (112) and a second input terminal of the operational amplifier to a first input (PWMI) of a supply circuit configured to receive a pulse width modulation signal, and coupling the second switch (112) and the second input terminal of the operational amplifier to a second input (108) arranged to provide a fixed voltage, the method of configuration (29).

[0111] (31) Further including supplying a standby current flowing through a transistor in response to coupling a second input terminal of the operational amplifier to a second input using a current source (133), such that very little or no current flows through the load, the method of configuration (30).

[0112] (32) Further including using the feedback circuit to control the amplitude of the current to be constant within 2% during at least 85% of the pulse in which the current is conducted through a load by a transistor, the method according to any one of configurations (28) to (31).

[0113] (33) Further including bypassing a second portion of the current in a second current path in a state where the transistor (T3) is a first transistor and the second transistor (T4) is configured in the second current path, the method according to any one of configurations (28) to (32).

[0114] (34) The method according to any one of configurations (28) to (33), further comprising detecting a voltage at the drain or collector of a transistor using a voltage monitor (140, 440).

[0115] (35) Using a controller communicatively coupled to a supply circuit, receiving a signal from a voltage monitor indicating a voltage at the drain or collector during a measurement interval including at least one sampling interval of a series of sampling intervals, calculating, using the controller, the power supplied to the load during the measurement interval-based period at least partially based on the received signal, and calculating, using the controller, the power supplied to the transistor base at least partially based on the received signal. The method according to any one of configurations (28) to (31) further includes the above steps.

[0116] (36) Accumulating, by a controller, a plurality of calculated powers supplied to a load to at least partially determine a current energy level of the load, comparing, by the controller, the current energy level of the load with an energy limit of the load, and issuing, by the controller, an instruction to the supply circuit to stop conduction of current through the load by a transistor when the current energy level of the load exceeds the energy limit of the load. The method according to configuration (35) further includes the above steps.

[0117] (37) The method according to configuration (36), further comprising considering a heat output dissipation rate of the load when determining the current energy level of the load by the controller.

[0118] (38) A housing (221), an imaging array (222) for acquiring an image, the imaging array being attached to the housing, the imaging array, and a supply circuit (100, 400) attached to the housing and conducting a current pulse that generates light to illuminate an object (230) imaged by the imaging array during an image acquisition period of the imaging array via a load (105), the image acquisition period including a time interval during which image data of one frame is captured by the imaging array, the supply circuit including a transistor (T3) arranged to conduct a current via the load (105), and a feedback circuit (125) for applying a signal to the transistor (T3) to control an amplitude of the current conducted by the transistor, the feedback circuit receiving a first feedback signal from a first sensing node (126) located in a first current path through which at least a first portion of the current flows when the current flows through the load, receiving a second feedback signal from a second sensing node (124) located in a second current path through which at least a second portion of the current flows when the current flows through the load, and being configured such that an impedance (R16) between the first sensing node and the second sensing node is bypassed by the second current path when the impedance (R16) between the first sensing node and the second sensing node is bypassed by the second current path, a camera (220).

[0119] (39) The camera of configuration (38) further comprising a mount (224) for receiving a lens assembly, a first connector (228) coupled to the housing and communicably coupled to a controller, and a second connector (227) coupled to the housing for connection to the load.

[0120] (40) The camera of configuration (39), wherein the first connector receives power over Ethernet.

[0121] (41) The camera of configuration (38) or (39), wherein the housing has a maximum edge dimension of 50 mm or less.

[0122] (42) The camera according to any one of configurations (38) to (41), wherein the feedback circuit includes an operational amplifier (120) for receiving a first feedback signal and a second feedback signal, and a switch (114) for connecting a first sensing node or a second sensing node to a first input terminal of the operational amplifier.

[0123] (43) The camera according to configuration (42), wherein the switch is a first switch, and the supply circuit further includes a second switch (112) for connecting a second input terminal of the operational amplifier to a first input (PWMI) configured to receive a pulse width modulation signal or a second input (108) arranged to provide a fixed voltage.

[0124] (44) The camera according to configuration (43), further comprising a current source (133) coupled to the transistor, wherein the fixed voltage causes a standby current to flow from the current source through the transistor such that the current flowing through the load is negligible or zero.

[0125] (45) The camera according to any one of configurations (38) to (44), wherein the impedance is a first impedance, and the supply circuit further includes a second impedance (R18) connected in series with the first impedance and located between the second sensing node and the reference potential.

[0126] (46) The camera according to configuration (45), wherein the second impedance is smaller than the first impedance.

[0127] (47) The camera according to any one of configurations (38) to (46), wherein the feedback circuit controls the amplitude of the current to be constant within 2% during at least 85% of the pulse in which the current is conducted through the load by the transistor.

[0128] (48) The transistor (T3) is a first transistor, and the supply circuit further includes a second transistor (T4) configured in a second current path and configured to bypass a second portion of the current in the second current path, the camera according to any one of configurations (38) to (47).

[0129] (49) The camera according to any one of configurations (38) to (48), further comprising a programmable voltage source (170) for applying a voltage to a load.

[0130] (50) The camera according to any one of configurations (38) to (49), further comprising a voltage monitor (140, 440) for detecting a voltage at a drain or collector of a transistor.

[0131] (51) In combination with a controller (210), the controller repeatedly, for a sequence of sampling intervals, during a measurement interval including at least one sampling interval of a series of sampling intervals, receives a signal from a voltage monitor indicating a voltage at a drain or collector, calculates the power supplied to a load based on the measurement interval, calculates, at least in part, the power supplied to the transistor on the received signal, and calculates, at least in part, the power supplied to the transistor, the camera of configuration (50).

[0132] (52) The controller is further configured to accumulate a plurality of calculated powers supplied to the load to at least partially determine a current energy level of the load, compare the current energy level of the load with an energy limit of the load, and stop inducing current through the load by the transistor when the current energy level of the load exceeds the energy limit of the load, the combination of configuration (51).

[0133] (53) A method of operating a camera, comprising: receiving, at a control terminal of a transistor (T3) of a supply circuit, a signal for conducting a current pulse through a load (105) to the transistor; controlling, by a feedback circuit (125) coupled to the transistor (T3), an amplitude of the current pulse conducted by the transistor; receiving, in the feedback circuit, a first feedback signal from a first sensing node (126) located in a first current path through which at least a first portion of the current pulse flows; receiving, in the feedback circuit, a second feedback signal from a second sensing node (124) located in a second current path through which at least a second portion of the current pulse flows; when receiving the second feedback signal, directing a second portion of the current pulse around an impedance (R16) connected between the first sensing node and the second sensing node; and acquiring, with an imaging array of the camera, a frame of image data of an object while the current pulse is being conducted through the load.

[0134] (54) Further comprising: biasing the transistor to a ready state after passing the current pulse through the load; and supplying a standby current from a current source (133) to the transistor while the transistor is in the ready state so that little or no current flows through the load while the transistor is in the ready state.

[0135] (55) The feedback circuit includes an operational amplifier (120) and a switch (114), and the method further comprises: receiving, at a first input terminal of the operational amplifier, the first feedback signal or the second feedback signal; coupling, with the switch, the first sensing node to the first input terminal to receive the first feedback signal; and coupling, with the switch, the second sensing node to the first input terminal to receive the second feedback signal.

[0136] (56) The switch is a first switch, and the method further includes coupling, with a second switch (112), a second input terminal of an operational amplifier to a first input (PWMI) of a supply circuit configured to receive a pulse-width modulation signal, and coupling, with the second switch (112), the second input terminal of the operational amplifier to a second input (108) arranged to provide a fixed voltage. The method of configuration (55).

[0137] (57) The method according to any one of configurations (53) to (56), further including using a feedback circuit to control the amplitude of the current pulse to be constant within 2% during at least 85% of the pulse during which the current pulse is conducted through a load by a transistor.

[0138] (58) The transistor (T3) is a first transistor, and the method according to any one of configurations (53) to (57) further includes using a second transistor (T4) configured in a second current path to bypass a second portion of the current pulse in the second current path.

[0139] (59) The method according to any one of claims (53) to (58), further including using a voltage monitor (140, 440) to detect the voltage at the drain or collector of the transistor.

[0140] (60) The method according to configuration (59) further includes receiving, with a controller communicably coupled to the supply circuit, a signal indicating the voltage at the drain or collector during a measurement interval including at least one sampling interval of a series of sampling intervals from the voltage monitor, calculating, with the controller, at least partially based on the received signal, the power supplied to the load during the measurement interval, and calculating, with the controller, at least partially based on the received signal, the power supplied to the transistor.

[0141] In order to at least partially determine the current energy level of the load, further including: accumulating, by a controller, a plurality of calculated powers supplied to the load; comparing, by the controller, the current energy level of the load with the energy limit of the load; and issuing, by the controller to a supply circuit, a command to stop conduction of a current pulse through the load by a transistor when the current energy level of the load exceeds the energy limit of the load, the method according to configuration (60).

[0142] Including further, when determining the current energy level of the load by the controller, considering the heat output dissipation rate of the load, the method of configuration (61). 7. Conclusion

[0143] Although various embodiments of the invention are described and illustrated herein, those skilled in the art will readily envision various other means and / or structures for performing the functions described herein and / or obtaining one or more of the results and / or advantages, and each of such variations and / or modifications is to be regarded as within the scope of the embodiments of the invention described herein. More generally, those skilled in the art will appreciate that all parameters, dimensions, materials, and configurations described herein are intended to be exemplary, and that actual parameters, dimensions, materials, and / or configurations will depend upon the particular application for which the teachings of the invention are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. Accordingly, the foregoing embodiments are presented by way of example only, and it is to be understood that within the scope of the appended claims and their equivalents, embodiments of the invention may be practiced otherwise than as specifically described. Embodiments of the inventions disclosed herein are directed to each individual function, system, article, material, kit, and / or method described herein. Further, any combination of two or more of such functions, systems, articles, materials, kits, and / or methods is included within the scope of the inventions disclosed herein so long as such functions, systems, articles, materials, kits, and / or methods are not mutually inconsistent.

[0144] Also, various inventive concepts may be embodied as one or more methods, of which an example has been provided. Acts performed as a part of the method may be ordered in any suitable order. Accordingly, in exemplary embodiments, even though acts are shown as sequential acts, embodiments may be constructed in which acts are performed in a different order than illustrated, including performing some acts simultaneously, which may include performing some acts simultaneously even though shown as sequential acts in the illustrative embodiments.

[0145] All definitions, as defined and used herein, are to be understood to control over dictionary definitions, definitions in incorporated documents by reference, and / or ordinary meanings of the defined terms.

[0146] In this specification and the claims, the indefinite articles "a" and "an" used in this specification should be understood to mean "at least one" unless the contrary meaning is clearly indicated.

[0147] As used in this specification and the claims, the phrase "and / or" should be understood to mean "one or both" of the elements so joined, i.e., elements that in some instances exist conjunctively and in other instances exist disjunctively. The plurality of elements listed with "and / or" should be construed in the same manner, i.e., "one or more" of the elements so joined. Other elements may optionally exist in addition to the elements specifically identified by the "and / or" clause, whether or not they are related to those specifically identified elements. Thus, by way of non-limiting example, a reference to "A and / or B" can refer in one embodiment to only A (optionally including elements other than B), in another embodiment to only B (optionally including elements other than A), and in yet another embodiment to both A and B (optionally including other elements), etc.

[0148] As used herein in the specification and claims, "or" should be understood to have the same meaning as "and / or" as defined above. For example, when separating items in a list, "or" or "and / or" is inclusive, i.e., it should be construed to include at least one of the number of elements or items in the list, but also includes two or more, and optionally, additional unlisted items. When used in the claims, only terms that clearly indicate the contrary, such as "only one of", "exactly one of", "consisting of", etc., refer to including exactly one element of the number of elements or the list. Generally, as used herein, "or" is construed only as indicating an exclusive alternative, such as "either one or the other but not both", or "only one of" or "exactly one of". When used in the claims, it shall have the ordinary meaning used in the field of patent law.

[0149] As used herein in the specification and claims, the phrase "at least one" in reference to a list of one or more elements means at least one element selected from any one or more of the elements in the list of elements, but does not necessarily include at least one of each and every element specifically recited in the list of elements and is not to be construed as excluding any combinations of elements in the list of elements. This definition also allows for elements to optionally exist outside of those specifically identified in the list of elements to which the phrase "at least one" refers, whether or not related to those specifically identified elements. Thus, by way of non-limiting example, "at least one of A and B" (or equivalently, "at least one of A or B", or equivalently, "at least one of A and / or B") can refer to, in one embodiment, optionally including two or more, and A and B not being present (and optionally including elements other than B), in another embodiment, optionally including two or more, and B and A not being present (and optionally including elements other than A), and in yet another embodiment, optionally including two or more for at least one of A, and optionally including two or more for at least one of B (and optionally including other elements), etc.

[0150] In the claims, as well as in the above specification, all transitional phrases such as "comprising," "carrying," "having," "containing," "involving," "holding," "consisting of," and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases "consisting of" and "consisting essentially of" are to be considered closed or semi-closed transitional phrases, as set forth in paragraph 2111.03 of the Manual of Patent Examining Procedure.

Claims

1. A supply circuit, A transistor arranged to conduct current through a load, A feedback circuit that applies a signal to the transistor and controls the amplitude of the current conducted by the transistor, wherein the feedback circuit is When the current flows through the load, a first feedback signal is received from a first sensing node located in a first current path through which at least a first portion of the current flows. A supply circuit configured to receive a second feedback signal from a second sensing node located in a second current path through which at least a second portion of the current flows, when the current flows through the load and the impedance between the first sensing node and the second sensing node is bypassed by the second current path.

2. The feedback circuit An operational amplifier for receiving the first feedback signal and the second feedback signal, The supply circuit according to claim 1, further comprising a switch for connecting the first sensing node or the second sensing node to the first input terminal of the operational amplifier.

3. The switch is the first switch, and the supply circuit is The supply circuit according to claim 2, further comprising: a second input terminal of the operational amplifier; a second switch connecting to a first input configured to receive a pulse-width modulated signal; or a second input arranged to provide a fixed voltage.

4. The supply circuit according to claim 3, comprising a current source coupled to the transistor, wherein the fixed voltage causes a standby current to flow from the current source through the transistor, and the current flowing through the load is negligible or not present at all.

5. The impedance is the first impedance, and the supply circuit is The supply circuit according to claim 2, comprising: a second impedance connected in series with the first impedance and located between the second sensing node and a reference potential.

6. The supply circuit according to claim 5, wherein the second impedance is smaller than the first impedance.

7. The supply circuit according to claim 1, wherein the feedback circuit controls the amplitude of the current to be constant within 2% for at least 85% of the pulses in which the current is conducted by the transistor through the load.

8. The transistor is the first transistor, and the supply circuit is The supply circuit according to claim 1, further comprising: a second transistor configured within the second current path and configured to bypass the second portion of the current within the second current path.

9. The supply circuit according to claim 1, further comprising a programmable voltage source for applying voltage to the load.

10. The supply circuit according to claim 9, wherein the programmable voltage source comprises a buck converter.

11. The supply circuit according to claim 1, further comprising a voltage monitor for detecting the voltage at the drain or collector of the transistor.

12. The supply circuit according to claim 11, wherein the voltage monitor comprises an analog-to-digital converter for sampling the voltage.

13. The supply circuit according to claim 11, wherein the voltage monitor comprises a voltage-frequency circuit and a timer for detecting the voltage.

14. When combined with the controller, the controller During a measurement interval that includes at least one sampling interval from the series of sampling intervals, a signal is received from the voltage monitor indicating the voltage at the drain or collector. Based at least partially on the received signal, the power supplied to the load during the measurement interval is calculated. The supply circuit according to claim 11, configured to calculate the power to be supplied to the transistor based at least partially on the received signal.

15. The aforementioned controller The calculation of the power supplied to the load is accumulated to determine at least partially the current energy level of the load, The current energy level of the load is compared with the energy limit of the load. The supply circuit according to claim 14, configured to stop the transistor from supplying current through the load when the current energy level of the load exceeds the energy limit of the load.

16. The combination according to claim 15, wherein determining the current energy level of the load includes the controller taking into account the thermal output dissipation rate of the load.

17. A supply circuit, A first transistor is positioned to conduct current through the load, A first resistor in a first circuit path through which at least a first portion of the current flows, A second resistor connected in series with the first resistor, through which at least a second portion of the current flows when connected to the load, A second transistor is arranged around the second resistor to shunt the current, A supply circuit comprising: a feedback circuit that receives a first feedback signal indicating a first voltage drop across the first resistor due to the first portion of the current when the second transistor shunts the current around the second resistor, and a second feedback signal indicating a second voltage drop across the combination of the first resistor and the second resistor due to the second portion of the current when the second transistor does not shunt the current around the second resistor.

18. The aforementioned feedback circuit An operational amplifier that receives the first feedback signal from the first sensing node at the terminals of the first resistor and the second feedback signal from the second sensing node at the terminals of the second resistor, The supply circuit according to claim 17, further comprising a switch for connecting the first sensing node or the second sensing node to the first input terminal of the operational amplifier.

19. The switch is the first switch, and the supply circuit is The supply circuit according to claim 18, further comprising: a second switch for connecting the second input terminal of the operational amplifier to a first input arranged to receive a pulse-width modulated signal, or a second input arranged to provide a fixed voltage.

20. The supply circuit according to claim 19, comprising a current source coupled to the transistor, wherein the fixed voltage causes a standby current to flow from the current source through the transistor, and the current flowing through the load is negligible or not present at all.

21. The supply circuit according to claim 17, wherein the second resistor is smaller than the first resistor.

22. The supply circuit according to claim 17, wherein the feedback circuit controls the amplitude of the current to be constant at 2% or less for 85% or more of the pulses in which the current is conducted through the load by the transistor.

23. The transistor is the first transistor, and the supply circuit is The supply circuit according to claim 17, further comprising: a second transistor configured within the second current path and configured to bypass the second portion of the current within the second current path.

24. The supply circuit according to claim 17, further comprising a programmable voltage source for applying voltage to the load.

25. The supply circuit according to claim 17, further comprising a voltage monitor for detecting the voltage at the drain or collector of the transistor.

26. In combination with the controller, the controller, during a measurement interval including at least one sampling interval among the series of sampling intervals, A signal is received from the voltage monitor indicating the voltage at the drain or collector. Based at least partially on the received signal, The supply circuit according to claim 25, configured to calculate the power supplied to the load during the measurement interval and to calculate the power supplied to the transistor based at least in part on the received signal.

27. The aforementioned controller The calculation of the power supplied to the load is accumulated to determine at least partially the current energy level of the load, The current energy level of the load is compared with the energy limit of the load. The supply circuit according to claim 26, wherein the transistor is configured to stop supplying current through the load if the current energy level of the load exceeds the energy limit of the load.

28. A method of inducing current through a load, The control terminal of the transistor in the supply circuit receives a signal that causes the transistor to conduct the current through a load, Within the supply circuit, a feedback circuit coupled to the transistor is used to control the amplitude of the current conducted by the transistor, Receiving a first feedback signal from a first sensing node located within the feedback circuit and within a first current path through which at least a first portion of the current flows, The feedback circuit receives a second feedback signal from a second sensing node located in a second current path through which at least a second portion of the current flows. A method comprising, upon receiving the second feedback signal, directing the second portion of the current around an impedance connected between the first sensing node and the second sensing node.

29. The feedback circuit includes an operational amplifier and a switch, and the method is The first input terminal of the operational amplifier receives the first feedback signal or the second feedback signal, The switch connects the first sensing node to the first input terminal to receive the first feedback signal, The method according to claim 28, further comprising coupling the second sensing node to the first input terminal of the switch to receive the second feedback signal.

30. The switch is the first switch, and the method is The second switch and the second input terminal of the operational amplifier are coupled to the first input of the supply circuit, which is configured to receive a pulse width modulated signal. The method according to claim 29, comprising: the second switch and coupling the second input terminal of the operational amplifier to a second input arranged to provide a fixed voltage.

31. Using a current source, The method according to claim 30, further comprising supplying a standby current that flows through the transistor in response to coupling the second input terminal of the operational amplifier to the second input, such that very little or no current flows through the load.

32. The method according to claim 28, further comprising using the feedback circuit to control the amplitude of the current to be constant to within 2% for 85% or more of the pulses in which the current is conducted through the load by the transistor.

33. The transistor is the first transistor, and the method is The method according to claim 28, further comprising bypassing the second portion of the current in the second current path using a second transistor configured in the second current path.

34. The method according to claim 28, further comprising detecting the voltage at the drain or collector of the transistor using a voltage monitor.

35. Using a controller responsively coupled to the supply circuit, during a measurement interval that includes at least one sampling interval of a series of sampling intervals, Receiving a signal from the voltage monitor indicating the voltage at the drain or collector, Using the controller, calculate the power supplied to the load during the measurement interval based at least partially on the received signal, The method according to claim 34, further comprising using the controller to calculate the power to be supplied to the transistor based at least in part on the received signal.

36. Using the controller, the multiple calculated powers supplied to the load are stored to determine, at least partially, the current energy level of the load. Using the controller, the current energy level of the load is compared with the energy limit of the load. The method of claim 35, further comprising: the controller issuing a command to the supply circuit to stop conducting the current through the load by the transistor when the current energy level of the load exceeds the energy limit for the load.

37. The method according to claim 36, further comprising considering the thermal output dissipation rate of the load when the controller determines the current energy level of the load.

38. It is a camera, Housing and An imaging array for acquiring images, wherein the imaging array is mounted within the housing, A supply circuit mounted in the housing for conducting current pulses through a light-generating load to illuminate an object captured by the imaging array during the image acquisition period of the imaging array, wherein the image acquisition period includes a time interval in which one frame of image data is captured by the imaging array, and the supply circuit A transistor arranged to conduct current through a load, A feedback circuit that applies a signal to the transistor and controls the amplitude of the current conducted by the transistor, wherein the feedback circuit is When the current flows through the load, a first feedback signal is received from a first sensing node located in a first current path through which at least a first portion of the current flows. A camera configured to receive a second feedback signal from a second sensing node located in a second current path through which at least a second portion of the current flows, when the current flows through the load and the impedance between the first sensing node and the second sensing node is bypassed by the second current path.

39. A mount for receiving the lens assembly, A first connector coupled to the housing and connected to the controller in a manner that enables communication, The camera according to claim 38, further comprising a second connector coupled to the housing and connected to the load.

40. The camera according to claim 39, wherein the first connector receives power over Ethernet.

41. The camera according to claim 38, wherein the housing has a maximum edge dimension of 50 mm or less.

42. The aforementioned feedback circuit An operational amplifier for receiving the first feedback signal and the second feedback signal, The camera according to claim 38, further comprising a switch for connecting the first sensing node or the second sensing node to the first input terminal of the operational amplifier.

43. The switch is the first switch, and the supply circuit is The camera according to claim 42, further comprising: a second input terminal of the operational amplifier, a second switch connecting to a first input configured to receive a pulse-width modulated signal, or a second input arranged to provide a fixed voltage.

44. The camera according to claim 43, further comprising a current source coupled to the transistor, wherein a standby current is caused to flow from the current source through the transistor by the fixed voltage, and little or no current flows through the load.

45. The impedance is the first impedance, and the supply circuit is The camera according to claim 38, further comprising: a second impedance connected in series with the first impedance and located between the second sensing node and a reference potential.

46. The camera according to claim 45, wherein the second impedance is smaller than the first impedance.

47. The camera according to claim 38, wherein the feedback circuit controls the amplitude of the current to be constant at 2% or less for 85% or more of the pulses in which the current is conducted through the load by the transistor.

48. The transistor is the first transistor, and the supply circuit is The camera according to claim 38, further comprising: a second transistor configured within the second current path and configured to bypass the second portion of the current within the second current path.

49. The camera according to claim 38, further comprising a programmable voltage source for applying voltage to the load.

50. The camera according to claim 38, further comprising a voltage monitor for detecting the voltage at the drain or collector of the transistor.

51. When combined with the controller, the controller During a measurement interval that includes at least one sampling interval from the series of sampling intervals, a signal is received from the voltage monitor indicating the voltage at the drain or collector. Based at least partially on the received signal, the power supplied to the load during the measurement interval is calculated. The camera according to claim 50, configured to calculate the power supplied to the transistor based at least in part on the received signal.

52. The aforementioned controller The multiple calculated powers supplied to the load are accumulated to determine, at least partially, the current energy level of the load. The current energy level of the load is compared with the energy limit of the load. The camera according to claim 51, further configured to stop the transistor from passing current through the load if the current energy level of the load exceeds the energy limit of the load.

53. A method for operating a camera, wherein the method is The control terminal of the transistor in the supply circuit receives a signal that conducts a current pulse through the load to the transistor, The amplitude of the current pulse conducted by the transistor is controlled using a feedback circuit coupled to the transistor, The feedback circuit receives a first feedback signal from a first sensing node located in a first current path through which at least a first portion of the current pulse flows. The feedback circuit receives a second feedback signal from a second sensing node located in a second current path through which at least a second portion of the current pulse flows. When receiving the second feedback signal, the second portion of the current pulse is directed around the impedance connected between the first sensing node and the second sensing node, A method further comprising acquiring a frame of image data of an object using the imaging array of the camera while the current pulse is being applied through the load.

54. After conducting the current pulse through the load, the transistor is energized in a ready state. The method according to claim 53, further comprising providing a standby current from a current source to the transistor while the transistor is in the ready state, such that, as a result, negligible or no current flows through the load while the transistor is in the ready state.

55. The feedback circuit includes an operational amplifier and a switch, and the method is The first input terminal of the operational amplifier receives the first feedback signal or the second feedback signal, The switch connects the first sensing node to the first input terminal to receive the first feedback signal, The method according to claim 53, further comprising coupling the switch and the second sensing node to the first input terminal to receive the second feedback signal.

56. The method according to claim 55, wherein the switch is a first switch, and the method further comprises a second switch and coupling a second input terminal of the operational amplifier to a first input of the supply circuit configured to receive a pulse-width modulated signal, and the second switch and coupling the second input terminal of the operational amplifier to a second input arranged to provide a fixed voltage.

57. The method according to claim 53, further comprising using the feedback circuit to control the amplitude of the current pulse to be constant to within 2% for 85% or more of the pulses through which the current pulse is conducted via the load of the transistor.

58. The transistor is the first transistor, and the method is The method according to claim 53, further comprising bypassing the second portion of the current pulse in the second current path using a second transistor configured in the second current path.

59. The method according to claim 53, further comprising detecting the voltage at the drain or collector of the transistor using a voltage monitor.

60. Using a controller communicatively coupled to the supply circuit, a signal from the voltage monitor indicating the voltage at the drain or collector is received during a measurement interval including at least one sampling interval of a series of sampling intervals. Using the controller, calculate the power supplied to the load during the measurement interval based at least partially on the received signal, The method according to claim 59, further comprising using the controller to calculate the power to be supplied to the transistor based at least in part on the received signal.

61. Using the controller, the multiple calculated powers supplied to the load are stored to determine, at least partially, the current energy level of the load. Using the controller, the current energy level of the load is compared with the energy limit of the load. The method according to claim 60, further comprising: the controller issuing a command to the supply circuit to stop conducting the current pulse through the load by the transistor when the current energy level of the load exceeds the energy limit for the load.

62. The method according to claim 61, further comprising considering the thermal output dissipation rate of the load when the controller determines the current energy level of the load.

Images