Closed-Loop DAC Artifact Generation

Abstract

To provide circuit supply systems that can selectively add an artifact signal onto to a regulated circuit supply output.SOLUTION: A circuit supply system is provided, comprising: a main digital to analog converter (DAC) circuit for producing a direct current (DC) output level at a system output; a feedback circuit path connected to the system output; a primary control circuit path connected to the feedback circuit path and configured to regulate the DC output level at the system output using the main DAC circuit and the feedback circuit path; and a secondary control circuit path connected to the feedback circuit path and configured to add a non-DC signal component to the DC output level and regulate the non-DC signal component using the feedback circuit path.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] (Priority Claim) This application claims priority to U.S. Provisional Application No. 63 / 376,467, filed September 21, 2022, which is incorporated herein by reference in its entirety.

[0002] The present invention relates generally, but not exclusively, to amplifier systems that provide a regulated circuit supply, and more particularly to circuit supply systems that can selectively add an artifact signal to the regulated circuit supply output. [Background technology]

[0003] Amplifier systems can be used to provide direct current (DC) outputs. These systems can be useful, for example, in automatic test equipment (ATE). In some ATE applications, it may be desirable to introduce artifacts, such as ripple and noise, into the DC output to test the performance, sensitivity, and reliability of a device under test (DUT) under these conditions. For example, electronic components used in electric vehicle (EV) applications tend to be exposed to high voltage and current ripple due to the high dynamic noise (or ripple) of switching power inverters. Injecting artifact signals into the circuit supply for the electronic components can test the robustness of the electronic components against high voltage and current ripple or noise and can be used to test the power supply rejection ratio (PSRR) of the electronic system under test. One approach to unidirectional ripple generation can be achieved using a transformer network. Figure 1 shows an example circuit for adding ripple to a power supply output. A ripple generator and coupling transformer are placed between the DC power supply and the DUT to couple a large AC signal into the circuit supply. A ripple generator may provide a sine wave at the output of the supply, and the ripple may be measured at the circuit nodes of the system under test. However, transformer networks such as the example of Figure 1 are fairly large and not very flexible in terms of the artifact signals they can generate. Summary of the Invention [Means for solving the problem]

[0004] The present invention provides a circuit supply system comprising: a main digital-to-analog converter (DAC) circuit for generating a direct current (DC) output level at a system output; a feedback circuit path connected to the system output; a primary control circuit path connected to the feedback circuit path and configured to adjust the DC output level at the system output using the main DAC circuit and the feedback circuit path; and a secondary control circuit path connected to the feedback circuit path and configured to add a non-DC signal component to the DC output level and adjust the non-DC signal component using the feedback circuit path.

[0005] The drawings, which are not necessarily drawn to scale, may include like numerals that describe like components in different drawings. Like numerals with different letter suffixes may represent different instances of like components. The drawings generally illustrate various embodiments described in this document by way of example, but not by way of limitation. [Brief explanation of the drawings]

[0006] [Figure 1] 1 is an example of a circuit for adding ripple to a power supply output. [Figure 2] FIG. 1 is a circuit diagram of a circuit supply system having a closed loop architecture. [Figure 3] FIG. 10 is a circuit diagram of another example of a circuit supply system. [Figure 4] FIG. 1 is a circuit diagram of another example of a circuit supply system including a direct digital synthesizer (DDS) and a numerically controlled oscillator (NCO). [Figure 5A] 1 shows a simulation of ripple signal generation using a circuit supply system. [Figure 5B] 1 shows a simulation of ripple signal generation using a circuit supply system. [Figure 5C] 1 shows a simulation of ripple signal generation using a circuit supply system. [Figure 5D] 1 shows a simulation of ripple signal generation using a circuit supply system. [Figure 6] FIG. 1 is a circuit diagram of another example of a circuit supply system including a digital down-converter (DDC). DETAILED DESCRIPTION OF THE INVENTION

[0007] 2 is a circuit diagram of an example circuit supply system 200 with a closed loop architecture that provides a regulated supply output that can add artificial circuit supply ripple and noise to the output using digital means, without the need for a significantly larger transformer network.

[0008] The system 200 includes a primary control circuit path and a secondary control circuit path. The primary control circuit path is shown as H in FIG. A (ω), and the secondary control circuit path is H B The primary control circuitry has a transfer function denoted as (ω). The primary control circuitry is responsible for maintaining a direct current (DC) output level at the output of the system 200. The DC output level may be a regulated DC output voltage or a regulated DC output current. The secondary control circuitry generates a non-DC signal that is added to the DC output level. The non-DC signal may be, for example, a ripple signal or a noise signal.

[0009] System 200 includes a feedback circuit path coupled from the output of the system to the inputs of both the primary and secondary control circuit paths. The feedback circuit path is represented in FIG. FBThe feedback circuit path includes an analog-to-digital converter (ADC) circuit 202 and an optional anti-aliasing filter (AAF) 204. The ADC circuit 202 generates a digital version of the output signal as a feedback signal. The primary and secondary control circuit paths use the feedback signal to adjust the DC output level and the non-DC output signal, respectively.

[0010] In the example of FIG. 2, the primary control circuitry includes a controller 206 and a digital-to-analog converter (DAC) circuit 208. The controller 206 may include logic circuitry for implementing the functionality described for the controller 206. The DAC circuit 208 is a main DAC circuit that generates a DC output level that can be used by the DUT as a circuit supply. The controller 206 adjusts the DAC code of the DAC circuit 208 to maintain a constant DC output level (e.g., adjusts the output voltage to a target output voltage (V OUT ≒V TARGET ) or to maintain the output current at the target output current (I OUT ≒I TARGET ) to maintain.

[0011] The secondary control circuitry includes a second controller 110 and a second DAC circuit 212. The controller 210 adjusts the DAC code of the DAC circuit 212 to introduce a non-DC artifact signal into the output of the system 100. The controllers 206, 210 may be included in the digital domain 214 of the system 100. The controllers 206, 210 may be implemented as a programmable gate array (PGA), an application-specific integrated circuit (ASIC), a processor, a microcontroller, a logic state machine, or a dedicated digital circuit. The controllers 206, 212 may execute adaptive and machine learning methods and algorithms. While the example of FIG. 2 utilizes two independent DAC channels, another approach involves the two control circuitry sharing a DAC circuit. Using two independent DAC channels can minimize crosstalk between the two control circuitry.

[0012] The DC output level from DAC 208 and the non-DC signal from DAC 212 are combined using summing circuit node 216. The primary and secondary control circuit paths each have a gain G A and G B The amplifiers 218 and 220 may be included to add a gain G F to the forward circuit path. The feedback circuit path provides a gain (or attenuation) G R The ADC 202 may include an amplifier 224 having a sense impedance R. The ADC 202 may measure the output voltage or the output current. A multiplexer (MUX) may be included to select whether the output current or the voltage is measured. The output current is measured by a sense impedance R. S (e.g., a resistor or other impedance circuit element). Another amplifier 226 can be used to measure the gain G M may be provided as a measurement of the output. In some examples, a transimpedance amplifier may be used to convert the current signal to a voltage signal.

[0013] The primary control circuit path with the feedback circuit path has a transfer function H A (ω)*H FB (ω), which functions to maintain a constant power supply output. The secondary control circuitry may operate in an open-loop mode or a closed-loop mode. In the open-loop mode, the second controller 110 ignores its input from the feedback circuitry and provides a predetermined (e.g., programmed) DAC code to the DAC circuit 212 to introduce a non-DC artifact signal (e.g., a ripple signal) into the system. The frequency of the non-DC artifact signal generated by the DAC circuit 212 is adjusted to the bandwidth (i.e., H) of the primary control loop so that the non-DC artifact signal does not significantly affect the stability of the primary control loop. A (ω)*H FB (bandwidth of ω) is assumed to be sufficiently larger than that of

[0014] In closed-loop mode, the secondary control circuit path with the feedback circuit path has a transfer function H B (ω)*H FB (ω), which functions to control the magnitude or power of the generated non-DC artifact signal. As with the open-loop approach, the primary and secondary closed loops are separated in frequency far enough apart that they do not significantly interact with each other in order to maintain stability and precise control by the two closed loops.

[0015] For example, if the bandwidth of the primary closed loop is substantially narrower than the bandwidth of the secondary closed loop, the ripple signal generated by the DAC circuit 212 will be proportional to the primary circuit path transfer function H A (ω) can be directly embedded in the output (voltage or current) without being filtered by ω. In other words, controller 206 adjusts DAC circuit 208 to achieve a steady-state (V OUT ≒V TARGET ), which is desirable for loop stability. Similarly, the controller 2010 strives to maintain a fixed ripple amplitude at a given frequency. An advantage of this system is that it allows the ripple frequency to be substantially higher than the bandwidth of the first-order closed loop, which can be beneficial in some applications.

[0016] In some examples, the relative bandwidth of the primary and secondary control circuitry may be adjusted within the controllers 206, 210. For example, if the primary and secondary control circuitry implement proportional-integral-derivative (PID) control, then the transfer function H A (ω) and H B (ω) is K P +K I s+K D s has the form integrator and differentiator coefficients (K I and K. D) may be adjusted to set the bandwidth. Alternatively, FIG. 2 shows that one or more filters may be implemented in the digital domain 214 of the output path of the ADC 202. A low-pass filter 228 may be implemented before the controller 206 so that all non-DC signal artifacts are ignored by the controller 206, thereby mitigating stability concerns. Similarly, a band-pass or high-pass filter 230 (e.g., a finite impulse response (FIR) filter) may be implemented before or within the controller 210 for the secondary circuit paths, depending on the number and frequency of waveforms generated. Starting the upper DAC channel with a low-pass filter 228 configures the upper DAC channel in FIG. 2 as a DC or low-frequency control circuit path. Starting the lower DAC channel with a band-pass or high-pass filter 230 configures the lower DAC channel as a higher-frequency circuit path.

[0017] 3 is a circuit diagram of another example of a circuit supply system 300. Instead of the two DAC example of FIG. 2, system 300 uses only the main DAC circuit 208 to provide a transfer function H A (ω)*H FB (ω) and the second-order closed loop H B (ω)*H FB (ω) or open-loop secondary control circuit path H B (ω) and implements a primary closed loop with (ω). The summing element 316 has been moved from the analog domain to the digital domain 314. The main DAC 208 receives the sum of the outputs of the first controller 206 and the second controller 210 and generates a DC output level and a non-DC signal. The primary control circuit path H A The lower frequency transfer function of (ω) and the higher frequency secondary control circuit path H B The bandwidth of (ω) may be set using digital filtering in each path as well as the corresponding controller 206, 210. In some examples, the circuit supply system includes one controller for both the primary and secondary control circuit paths. The controller controls the primary control circuit path H A (ω) transfer function and secondary control circuit path HB Implement both the (ω) transfer function and

[0018] Returning to FIG. 2 , the exemplary system shows one secondary circuit path or one secondary DAC channel and one feedback circuit path or one ADC channel. In some examples, system 200 includes additional parallel DAC and ADC channels with corresponding filtering and controllers. For example, additional DAC channels may be added to generate and control artifact waveforms at different frequencies. Two or more tones with offset frequencies may be generated to enable intermodulation distortion (IMD) measurements. One ADC channel is used to selectively measure the output voltage, output current, or different circuit output paths (paths A-D). In another embodiment, additional ADC feedback paths may be added to simultaneously measure the output voltage and output current. Alternatively, different ADCs may be used to monitor artifacts at different frequencies or with different range and resolution requirements.

[0019] 4 is a circuit diagram of another example of a circuit supply system 400. This example is a multi-DAC system that includes a primary control circuit path that includes a controller 206 and a main DAC circuit 208. The system 400 also includes one or more secondary control circuit paths, each of which includes a filter 430 (filter i , i=1, ...N), and a controller 410 (controller i ) and DAC412 (DAC i ) and DAC (DAC i ) is a direct digital synthesizer 432 (DDS i ) The number N of DDS blocks in the system may be configured according to the number of dedicated DACs and controllers.

[0020] The digital circuitry of the DDS 432 includes a numerically controlled oscillator (NCO) 434. The NCO 434 generates a non-DC signal (e.g., a ripple signal) having a periodic waveform (e.g., a sine waveform, a triangular waveform, a square waveform, a pulse waveform, etc.). When the non-DC signal is a ripple signal, the frequency of the ripple signal may be selectable by a user. A multiplier 436 multiplies the output of the NCO 434 by the digital value output from the second controller to generate a digital output signal for the DAC 432. i A digital ripple signal may be provided to the controller 412. i 410 can provide an output that controls the amplitude of the ripple waveform.

[0021] In some examples, the DDS 432 includes a peak or envelope detector 438. The peak or envelope detector function may be implemented in the digital domain 414 or may be a separate peak or envelope detector circuit. i 410, the controller can be operated at a significantly reduced (baseband) speed or bandwidth. i 410 will be able to operate.

[0022] 5A-5D illustrate a simulation of ripple signal generation using a circuit supply system. FIG. 5A is a simulated output voltage waveform of an exemplary embodiment of the circuit supply system 400 of FIG. 4. The primary control circuit path functions to maintain a constant 200V power supply output 505. The secondary control circuit path adds a 10 volt peak-to-peak (10Vp-p) ripple signal 510 and a 40Vp-p ripple signal 515 to the 200V output. FIG. 5B illustrates the envelope waveform output of the high-pass filter 430. FIG. 5C illustrates the DAC code updates for the main DAC 520 and the secondary DAC 525. The waveforms show that the primary closed-loop DACs are not disturbed. FIG. 5D illustrates a zoomed-in view of the DAC code update 525 around 0.09 seconds in FIG. 5C.

[0023] 6 is a circuit diagram of another example of a circuit supply system 600. The system 600 includes the controller 206, the main DAC circuit 208, and the direct digital synthesizer 432 (DDS i 4 in that it includes a primary control circuit path including one or more NCOs configured as a filter. The example of FIG. 6 mathematically provides ripple envelope tracking. System 600 includes NCO 434 and multiplier 436. The ripple waveform signal is filtered by a filter. i The signal is captured in digital form at the output of the 430. i The output of is digitally down-converted to baseband using a multiplication operation by multiplier 638. Multiplier 638 may be implemented in one or more of hardware, software, or firmware in the digital domain.

[0024] The output of the NCO434 is a digital ripple waveform signal (filtered i When multiplied (at the output of multiplier 638), the output of multiplier 640 contains a low frequency term near DC and another term at twice (2X) the ripple frequency. A low pass filter (LPF) 640 is included at the output of multiplier 638 to filter out the 2X ripple frequency term. Thus, only the low frequency components, which contain the amplitude envelope information of the ripple signal, are passed to the controller. i Passed to 410.

[0025] In some examples, the NCO 434 in FIGS. 4 and 6 can be replaced by a noise generator circuit. The generated noise can be random noise or pseudorandom (PRN). Random noise has a spectrally flat AC response, commonly referred to as a white spectral response, because it includes all spectral colors. In practice, random noise can be approximated using a PRN generated by a pseudorandom bit sequencer (PRBS). The generated random noise or PRN can have a flat spectral output response or can have different target spectral responses, including lower and higher frequency responses. The noise can also be generated to have an alternating current (AC) response within a specific target frequency band. In some examples, the noise can be flicker (1 / f) noise.

[0026] In some instances, ripple signal generation and noise signal generation are combined in a closed-loop system. The nested control loops may function sufficiently independently with careful frequency planning (spacing) and filtering. Alternatively, quadrature pseudo-noise (PN) sequences may be decoded in the time domain by a corresponding controller.

[0027] Similar to the ripple signal generator example, the average magnitude or power of the noise signal can be tracked using a secondary control circuitry to control the average or root-mean-square (RMS) value. The noise generated in the secondary control circuitry may be high-pass filtered. Delta-sigma modulation (DSM) may be used to push the noise power to sufficiently high frequencies so that the primary control circuitry is not significantly affected. In another embodiment, the applied noise or ripple signal may be dithered in the time domain by dithering the clock input of the corresponding DAC to reduce spectral tones at the output.

[0028] In another use case of a multi-DAC architecture, the effective resolution of a circuit-supply system may be improved by having the controller toggle one or more of the secondary control circuit path DACs between two or more levels according to a predetermined sequence so that the average value of the toggled signal is less than one least significant bit (LSB). For example, in a two-DAC system (e.g., system 200 of FIG. 2 ) in which both DACs have the same resolution (e.g., the same number of bits), DAC 212 may be allowed to toggle up or down one LSB with a given duty cycle. For a 50% duty cycle, the average value of the toggle may be ½ LSB. Quantization noise shaping techniques such as delta-sigma modulation (DSM), pulse density modulation (PDM), and pulse-width modulation (PWM) may also be applied. In such applications, the sampling rate of the DAC 212 may be significantly (e.g., 16 or 20 times) higher than the sampling rate of the DAC 208 so that the upconverted quantization noise can be filtered by the main loop controlled by the DAC 208. To reduce ripple at the output due to toggling the DAC 212, the sampling edges of the DAC 212 may be dithered relative to the DAC 208 in a random or stochastic manner to spread the ripple energy over a wider frequency range. The toggling may be configured to match the needs of a particular use case. Similarly, the resolution of the measurement ADC 202 may be improved by oversampling, noise shaping, averaging, and dithering techniques, which allow for an increase in the overall resolution of the closed-loop system.

[0029] A system and method for artifact generation (ripple and noise) and control implemented in a closed-loop DAC architecture is described. The artifact signal is generated using direct digital synthesis (DDS) or arbitrary waveform generation (AWG) techniques in a closed-loop approach. The artifact signal is added onto a steady-state DC operating voltage (or current) maintained by a controller in a primary DC operating loop. The artifact signal may be added directly to the output without significantly disturbing the stability of the primary DC operating loop. Additionally, the described technique provides precise closed-loop control of the magnitude or power of the artifact waveform. In a further example, the DAC used for artifact signal generation may be reused to improve the resolution of the steady-state DC operating voltage by controllably toggling between two or more levels according to a predetermined sequence such that the average value of the toggled signal is less than the LSB.

[0030] Additional Description and Examples Example 1 includes subject matter (such as a circuit supply system) comprising a main digital-to-analog converter (DAC) circuit for generating a direct current (DC) output level at a system output; a feedback circuit path connected to the system output; a primary control circuit path connected to the feedback circuit path and configured to adjust the DC output level at the system output using the main DAC circuit and the feedback circuit path; and a secondary control circuit path connected to the feedback circuit path and configured to add a non-DC signal component to the DC output level and adjust the non-DC signal component using the feedback circuit path.

[0031] In Example 2, the subject matter of Example 1 optionally includes: a primary control circuit path including a first controller and a main DAC circuit; a secondary control circuit path including a second controller and a second DAC circuit configured to generate a non-DC signal component; and a summing node operatively coupled to an output of the main DAC circuit and an output of the second DAC, the summing node configured to add the non-DC signal component to a DC output level.

[0032] In Example 3, the subject matter of Example 1 optionally includes a primary control circuit path including a first controller, a secondary control circuit path including a second controller, and a main DAC circuit configured to receive a sum of an output of the first controller and an output of the second controller and generate a DC output level and a non-DC signal component.

[0033] In Example 4, the subject matter of one or any combination of Examples 1-3 optionally includes a feedback circuit path including an analog-to-digital converter (ADC) circuit, a controller coupled to the ADC circuit of the feedback circuit, a primary control circuit path having a first transfer function, a secondary control circuit path including a second transfer function, and a controller configured to implement the first and second transfer functions.

[0034] In Example 5, the subject matter of one or any combination of Examples 1-4 optionally includes a primary control circuit path including a low pass filter circuit configured to provide a first frequency signal component of the system output to the primary control circuit path, and a secondary control circuit path including one of a high pass filter or a band pass filter configured to provide a second signal component of the system output to the secondary control circuit path, wherein the second signal component has a higher frequency than the first frequency signal component.

[0035] In Example 6, the subject matter of one or any combination of Examples 1 and 4-5 optionally includes: a primary control circuit path including a first controller and a main DAC circuit; a second controller for outputting a digital value; the second DAC circuit configured to generate an analog ripple signal as a non-DC signal; a secondary control circuit path including a numerically controlled oscillator (NCO); a multiplier configured to multiply the output of the NCO by the digital value of the second controller to provide the digital ripple signal to the second DAC circuit; and at least one of a peak detector or an envelope detector configured to monitor an amplitude of the analog ripple signal to the second controller.

[0036] In Example 7, the subject matter of one or any combination of Examples 1 and 4-5 optionally includes: a primary control circuit path including a first controller and a main DAC circuit; a second controller for outputting a digital value and a second DAC circuit configured to generate an analog ripple signal as a non-DC signal component; a secondary control circuit path including a numerically controlled oscillator (NCO), a first multiplier configured to multiply the output of the NCO by a signal received from the feedback circuit path to provide a product signal including amplitude envelope information to the second controller; and a second multiplier configured to multiply the output of the NCO by a digital value of the second controller to provide a digital ripple signal to the second DAC circuit.

[0037] In Example 8, the subject matter of one or any combination of Examples 1-7 optionally includes at least one controller connected to the feedback circuit path, another control circuit path, and a secondary control circuit path configured to generate a ripple signal and adjust the ripple signal using the first feedback circuit path, the other control circuit path configured to generate a noise signal, and the at least one controller configured to selectively add one or both of the ripple signal and the noise signal to the DC output level.

[0038] In Example 9, the subject matter of one or any combination of Examples 1-8 optionally includes a feedback circuit configured to feed back an output voltage signal at the system output to the primary control circuit path and the secondary control circuit path, and another feedback circuit path configured to feed back an output current signal at the system output to the primary control circuit path and the secondary control circuit path.

[0039] Example 10 includes subject matter (e.g., a method of operating a circuit supply system) or can include such subject matter, optionally in combination with one or any combination of Examples 1-9, including generating a direct current (DC) output level at a system output of the circuit supply system using a primary control circuit path and a main digital-to-analog converter (DAC) circuit; generating an output signal at the system output by adding a non-DC signal component to the DC output level using a secondary control circuit path; and adjusting the DC output level and adjusting the non-DC signal component using a feedback circuit path connected to the system output and to both the primary and secondary control circuit paths.

[0040] In Example 11, the subject matter of Example 10 optionally includes generating a DC output level using a primary control circuit path and a main DAC circuit included in the primary control circuit path, generating a ripple signal using a second DAC circuit included in the secondary control circuit path, and adding the ripple signal to the DC output level by summing outputs of the primary control circuit path and the secondary control circuit path.

[0041] In Example 12, the subject matter of one or both of Examples 10 and 11 optionally includes summing an output of a controller of the primary control circuit path and an output of a controller of the secondary control circuit path, and providing the sum of the controller outputs to an input of the main DAC circuit.

[0042] In Example 13, the subject matter of one or any combination of Examples 10-12 optionally includes: feeding back an output signal from a system output using a feedback circuit path, wherein the output signal includes a DC output level and a ripple signal as a non-DC signal component; converting the output signal into a digital electrical signal including a digital ripple signal and the DC output level; separating the digital ripple signal from the DC output level; and providing the separated digital ripple signal to a secondary control circuit path and the DC output level to a primary control circuit path.

[0043] In Example 14, the subject matter of one or any combination of Examples 10-13 optionally includes generating the ripple signal using a numerically controlled oscillator (NCO) included in the secondary control circuit path, and adjusting the ripple signal by adjusting the NCO according to an amplitude of the separated digital ripple signal.

[0044] In Example 15, the subject matter of Example 14 optionally includes multiplying the output of the NCO with the separated digital ripple signal to generate a product signal; and filtering the product signal to generate an envelope signal containing amplitude information of the separated digital ripple signal.

[0045] In Example 16, the subject matter of one or any combination of Examples 10-15 optionally includes multiplying an output of a controller of the secondary control circuitry with an output of a numerically controlled oscillator (NCO); and providing the multiplied output to a second DAC circuit included in the secondary control circuitry to generate a ripple signal as a non-DC signal component added to the DC output level.

[0046] In Example 17, the subject matter of one or any combination of Examples 10-17 optionally includes generating the output signal at the system output by adding a noise signal to the DC output level using a secondary control circuit path.

[0047] Example 18 may include subject matter (e.g., a supply circuit) or may include such means, optionally in combination with one or any combination of Examples 1-17 to include such subject matter, comprising a main digital-to-analog converter (DAC) circuit, a secondary circuit path including a second DAC circuit, a summing circuit node connected to an output of the primary circuit path and connected to the output of the secondary circuit path to generate an output signal at an output of the supply circuit, a feedback circuit path connected to the output of the supply circuit and the primary circuit path, and a control circuit. The feedback circuit includes an analog-to-digital conversion (ADC) circuit for generating a feedback signal. The control circuit is configured to set an input of the main DAC circuit to generate a direct current (DC) output level at an output of the supply circuit based on the feedback signal, and to toggle the second DAC circuit between two output levels corresponding to one least significant bit (LSB) of the main DAC circuit.

[0048] In Example 19, the subject matter of Example 18 optionally includes a low pass filter circuit including an input connected to the summing node; and a controller configured to sample the feedback signal at the sampling frequency and to toggle the second DAC circuit at a toggle frequency higher than the sampling frequency, where the toggle frequency is within a stop band of the low pass filter.

[0049] In Example 20, the subject matter of one or both of Examples 18 and 19 optionally includes a controller configured to sample the feedback signal using the sampling signal and to toggle the second DAC circuit using the toggling signal, and a controller configured to dither edges of the toggling signal relative to edges of the sampling signal.

[0050] These non-limiting examples may be combined in any permutation or combination. The above detailed description includes references to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are also referred to herein as "Examples." All publications, patents, and patent documents mentioned herein are incorporated by reference in their entirety, as though individually incorporated by reference. In the event of a conflict in usage between this document and a document incorporated by reference, the usage of the incorporated reference document shall be deemed to supplement the usage of this document, with the usage of this document taking precedence in the event of any conflict.

[0051] In this document, the terms "a" or "an" are used, as is common in patent documents, to include one or more than one, regardless of other instances or uses of "at least one" or "one or more." In this document, the term "or" is used to refer to a non-exclusive "or," such that "A or B" includes "A but not B," "B but not A," and "A and B," unless otherwise specified. In the appended claims, the terms "including" and "in which" are used as the plain-English equivalents of the respective terms "comprising" and "wherein." Also, in the following claims, the terms "including" and "comprising" are intended to be open-ended, i.e., systems, apparatus, articles, or processes that include elements in addition to those recited after such terms in a claim are still considered to be within the scope of that claim. Furthermore, in the following claims, the terms "first," "second," "third," etc. are used merely as designators and are not intended to impose numerical requirements on their objects. Method embodiments described herein may be at least partially machine or computer implemented. [Explanation of symbols]

[0052] 100 systems 110 Second Controller 200 Circuit Supply System 202 ADC circuit 204 Anti-Aliasing Filter (AAF) 206 First Controller 208 Digital-to-Analog Converter (DAC) Circuit 210 Second Controller 212 Second DAC circuit 214 Digital Domain 216 total circuit nodes 218 Amplifier 220 Amplifier 222 Amplifier 224 Amplifier 226 Amplifier 228 Low-pass filter 230 High Pass Filter 300 Circuit Supply System 314 Digital Domain 316 Additive Elements 400 Circuit Supply System 410 Controller i 412 DAC i 414 Digital Domain 430 High Pass Filter 432 Direct Digital Synthesizer 434 Numerically Controlled Oscillator (NCO) 436 Multiplier 438 Envelope Detector 505 power output 510 10Vp-p ripple signal 515 40Vp-p ripple signal 520 Main DAC 525 Second DAC 600 Circuit Supply System 638 Multiplier 640 Low Pass Filter (LPF) 2010 Controller

Claims

1. 1. A circuit supply system comprising: a main digital-to-analog converter (DAC) circuit for generating a direct current (DC) output level at a system output; a feedback circuit path connected to the system output; a primary control circuit path connected to the feedback circuit path and configured to adjust the DC output level at the system output using the main DAC circuit and the feedback circuit path, the primary control circuit path including a low pass filter circuit configured to provide a first frequency signal component of the system output to the primary control circuit path; a secondary control circuit path connected to the feedback circuit path and configured to add a non-DC signal component to the DC output level and adjust the non-DC signal component using the feedback circuit path, the secondary control circuit path including one of a high pass filter or a band pass filter configured to provide a second signal component at the system output having a higher frequency than the first frequency signal component.

2. the primary control circuit path includes a first controller and the main DAC circuit; the secondary control circuit path including a second controller and a second DAC circuit configured to generate the non-DC signal component; a summing node operatively coupled to the output of the main DAC circuit and the output of the second DAC circuit, the summing node configured to add the non-DC signal component to the DC output level.

3. the primary control circuitry includes a first controller; the secondary control circuitry includes a second controller; 2. The circuit supply system of claim 1, wherein a main DAC circuit is configured to receive the sum of the output of the first controller and the output of the second controller and generate the DC output level and the non-DC signal component.

4. the feedback circuit path includes an analog-to-digital converter (ADC) circuit; a controller connected to the ADC circuit in the feedback circuit path; the primary control circuit path having a first transfer function; the secondary control circuit path having a second transfer function; 2. The circuit supply system of claim 1, wherein the controller is configured to implement the first and second transfer functions.

5. the primary control circuit path includes a first controller and the main DAC circuit; the secondary control circuit path: a second controller for outputting a digital value; a second DAC circuit configured to generate an analog ripple signal as the non-DC signal; a numerically controlled oscillator (NCO); a multiplier configured to multiply the digital value of the second controller by the output of the NCO to provide a digital ripple signal to the second DAC circuit; and at least one of a peak detector or an envelope detector configured to monitor the amplitude of the analog ripple signal to the second controller.

6. the primary control circuit path includes a first controller and the main DAC circuit; the secondary control circuit path: a second controller for outputting a digital value; a second DAC circuit configured to generate an analog ripple signal as the non-DC signal component; a numerically controlled oscillator (NCO); a first multiplier configured to multiply the output of the NCO with a signal received from the feedback circuit path and provide a product signal containing amplitude envelope information to the second controller; a second multiplier configured to multiply the digital value of the second controller by the output of the NCO to provide a digital ripple signal to the second DAC circuit.

7. at least one controller connected to the feedback circuit path; and another control circuit path; the secondary control circuit path is configured to generate a ripple signal and adjust the ripple signal using the feedback circuit path; the other control circuitry is configured to generate a noise signal; 2. The circuit supply system of claim 1, wherein the at least one controller is configured to selectively add one or both of the ripple signal and the noise signal to the DC output level.

8. the feedback circuit path is configured to feed back an output voltage signal at the system output to the primary control circuit path and the secondary control circuit path; 10. The circuit supply system of claim 1, wherein another feedback circuit path is configured to feed back an output current signal at the system output to the primary control circuit path and the secondary control circuit path.

9. 1. A method of operating a circuit supply system, said method comprising: generating a direct current (DC) output level at the system output of the circuit supply system using a primary control circuit path including a low pass filter circuit configured to provide a first frequency signal component at the system output of the circuit supply system and a main digital-to-analog converter (DAC) circuit; generating an output signal at the system output by adding a non-DC signal component to the DC output level using a secondary control circuit path, the secondary control circuit path including one of a high pass filter or a band pass filter configured to provide a second signal component at the system output having a higher frequency than the first frequency signal component; and adjusting the DC output level and adjusting the non-DC signal components using a feedback circuit path connected to the system output and to both the primary and secondary control circuit paths.

10. generating the DC output level includes generating the DC output level using the primary control circuitry and the main DAC circuit included in the primary control circuitry; 10. The method of claim 9, wherein adding the non-DC signal component to the DC output level comprises generating a ripple signal using a second DAC circuit included in the secondary control circuitry, and adding the ripple signal to the DC output level by summing outputs of the primary control circuitry and the secondary control circuitry.

11. adding the non-DC signal component to the DC output level; summing the output of the controller of the primary control circuitry and the output of the controller of the secondary control circuitry; and providing the sum of the outputs of the controllers to an input of the main DAC circuit.

12. feeding back the output signal from the system output using the feedback circuit path, the output signal including a DC output level and a ripple signal as the non-DC signal components; converting the output signal into a digital electrical signal including a digital ripple signal and the DC output level; 10. The method of claim 9, comprising: separating the digital ripple signal from the DC output level; and providing the separated digital ripple signal to the secondary control circuit path and the DC output level to the primary control circuit path.

13. generating the ripple signal using a numerically controlled oscillator (NCO) included in the secondary control circuitry; 13. The method of claim 12, wherein adjusting the non-DC signal component comprises adjusting the ripple signal by adjusting the NCO according to an amplitude of the separated digital ripple signal.

14. multiplying the output of the NCO with the separated digital ripple signal to generate a product signal; and filtering the product signal to generate an envelope signal containing amplitude information of the separated digital ripple signal.

15. adding the non-DC signal component to the DC output level using a secondary control circuit path; multiplying an output of a numerically controlled oscillator (NCO) by an output of the controller of the secondary control circuitry; and providing the multiplied output to a second DAC circuit included in the secondary control circuit path to generate a ripple signal as the non-DC signal component added to the DC output level.

16. 10. The method of claim 9, wherein said generating said output signal comprises generating said output signal at said system output by adding a noise signal to said DC output level using said secondary control circuitry.

17. A supply circuit, a primary circuit path including a main digital-to-analog converter (DAC) circuit; a secondary circuit path including a second DAC circuit; a summing node connected to an output of the primary circuit path and an output of the secondary circuit path, the summing node generating an output signal at an output of the supply circuit; a feedback circuit path connected to the output of the supply circuit and to the primary circuit path, the feedback circuit path including an analog-to-digital converter (ADC) circuit for generating a feedback signal; a controller, wherein the controller: configured to set an input of the main DAC circuit to produce a direct current (DC) output level at the output of the supply circuit based on the feedback signal; A supply circuit configured to toggle the second DAC circuit between two output levels corresponding to one least significant bit (LSB) of the main DAC circuit.

18. a low pass filter circuit having an input connected to the summing node; the controller is configured to sample the feedback signal at a sampling frequency and to toggle the second DAC circuit at a toggle frequency higher than the sampling frequency; 18. The supply circuit of claim 17, wherein the toggle frequency is within a stop band of the low pass filter circuit.

19. The controller: configured to sample the feedback signal using a sampling signal and to toggle the second DAC circuit using a toggling signal; 18. A supply circuit as claimed in claim 17, configured to dither edges of the toggling signal relative to edges of the sampling signal.

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