System for realizing digital-to-analog conversion by using superposition pulse width modulation
By using superimposed pulse width modulation technology and low-cost components, high-precision digital-to-analog conversion was achieved, solving the balance between cost and accuracy, and improving the quality of analog signals and the utilization rate of controller interfaces.
Patent Information
- Application Number
- CN202423087239.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-13
- Publication Date
- 2025-12-02
- Estimated Expiration
- 2034-12-13
AI Technical Summary
Existing digital-to-analog converters (DACs) struggle to balance improving accuracy with control costs. High-bit-count DACs are expensive, while low-bit-count DACs lack sufficient accuracy and have limited communication interface resources, leading to design difficulties.
By employing superimposed pulse width modulation technology, the accuracy of the analog output signal is improved through the superposition of multiple PWM waveforms and frequency multiplication. Digital-to-analog conversion is achieved using low-cost components such as Schmitt inverters, adder amplifiers, and filter capacitors.
High-precision digital-to-analog conversion was achieved at low cost, saving controller communication interface resources and improving the accuracy and quality of analog output signals.
Smart Images
Figure CN223625856U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to a digital-to-analog conversion technology, and more particularly to a system for realizing digital-to-analog conversion using superimposed pulse width modulation. Background Technology
[0002] The world today is a digital world, where the transmission, calculation, and storage of information are all achieved digitally. Digital signals have advantages such as strong anti-interference capabilities, ease of calculation and processing, and ease of storage. However, when it comes to high-speed and high-precision control and measurement, digital signals still have some drawbacks. The main drawbacks of digital signals include quantization errors, processing complexity, and slower response speed. Quantization error is one of the most significant drawbacks of digital signals. During the sampling process, due to the discreteness of digital signals, errors are introduced, which may lead to signal distortion, especially at low resolutions where the impact of such errors is more severe. Moreover, digital signal processing is relatively complex, typically requiring digital signal processors (DSPs). Therefore, compared to analog signals, digital signal processing requires more computing resources and programming work, increasing system complexity and cost for some simple applications. In addition, digital signal processing and conversion require a certain amount of time. In applications with high real-time requirements, digital signals may not respond in time, thus affecting system performance. In contrast, analog signals still have many advantages in these aspects and can be widely used in control, measurement, and signal synthesis fields where high precision and response speed are required. Due to the respective advantages of digital and analog signals, we need to convert digital signals into analog signals for processing in many applications. Therefore, the demand for digital-to-analog converters in circuit design is increasing day by day.
[0003] However, with the increasing demand for analog-to-digital converters (ADCs) in circuits, higher requirements are also being placed on the accuracy of ADCs. To enable ADCs to be used in applications requiring a certain level of accuracy, the common practice is to increase the number of data bits in the ADC, thereby indirectly improving the output accuracy. However, two problems arise in practical design. First, the number of bits in an ADC cannot be increased indefinitely. Second, even if the number of bits could be increased infinitely, adding each data bit would incur a significant cost, which is unacceptable in product design. Therefore, researching a high-precision ADC method that can keep costs within a certain range has become an urgent need in product design.
[0004] In practical designs, using high-bit, low-error digital-to-analog converter chips for digital-to-analog conversion requires additional components, resulting in relatively high costs. In consumer products where cost control is relatively strict, this method, while offering superior performance, is often unacceptable due to cost issues. On the other hand, using relatively inexpensive, low-error digital-to-analog converters cannot meet the accuracy requirements of the design, leaving designers in a dilemma.
[0005] Existing technology 1: A technical solution using a digital-to-analog converter chip for digital-to-analog conversion.
[0006] This technical solution is one of the most common, which uses a digital-to-analog converter integrated circuit chip and adds a follower or other type of amplifier at the back end to convert the digital signal into an analog voltage signal. Its technical solution is as follows:
[0007] First, the control chip transmits digital signals to the digital-to-analog converter integrated circuit chip through a parallel or serial communication interface;
[0008] Subsequently, the digital-to-analog converter integrated circuit chip uses resistor networks, analog switches, and operational amplifiers to convert the digital signal into an analog voltage or current signal that is proportional to the reference source voltage.
[0009] Then, the analog signal output from the digital-to-analog converter integrated circuit chip is processed by impedance matching, voltage conversion and filtering through a follower or amplifier at the back end before being output, thereby realizing the conversion of digital signal to analog signal.
[0010] Disadvantages of using digital-to-analog converter chips for digital-to-analog conversion:
[0011] 1) Using a digital-to-analog converter (DAC) chip for digital-to-analog conversion can meet high-precision requirements, but increasing the conversion accuracy requires increasing the number of data bits in the DAC chip, which significantly increases the cost. Achieving low cost often means that the required conversion accuracy cannot be met, making it impossible to achieve a balance between accuracy and cost.
[0012] 2) Data transmission between the digital-to-analog converter (DAC) and the controller is accomplished through parallel or staggered communication interfaces. However, communication interfaces are often limited in microcontrollers, especially low-cost controllers, and are considered scarce resources. Implementing multi-channel DAC requires more interface resources, which increases design costs.
[0013] In view of the above, this utility model is hereby proposed. Utility Model Content
[0014] The purpose of this invention is to provide a system for digital-to-analog conversion using superimposed pulse width modulation, so as to solve the above-mentioned technical problems existing in the prior art.
[0015] The objective of this utility model is achieved through the following technical solution:
[0016] This utility model discloses a system for digital-to-analog conversion using superimposed pulse width modulation, including a controller, which acts as a multi-channel PWM generator and is correspondingly connected to a multi-channel digital-to-analog conversion circuit.
[0017] Each digital-to-analog converter circuit includes a Schmitt inverter, an adder amplifier, a filter smoothing circuit, and an output follower connected in sequence, wherein the output follower is provided with an analog output port.
[0018] Compared with the prior art, the system for digital-to-analog conversion using superimposed pulse width modulation provided by this utility model, on the basis of realizing digital-to-analog conversion using PWM pulse width modulation technology, achieves frequency multiplication of PWM by superimposing multiple waveforms, thereby further improving the accuracy of analog output signal. Attached Figure Description
[0019] Figure 1 This is a system structure block diagram for digital-to-analog conversion using superimposed pulse width modulation, provided for an embodiment of this utility model.
[0020] Figure 2 This is a schematic diagram illustrating the principle of an embodiment of the present utility model.
[0021] Figure 3 This is a schematic diagram illustrating the principle of effectively controlling the waveform phase of several PWM outputs according to an embodiment of this utility model. Detailed Implementation
[0022] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments, which do not constitute a limitation on the present utility model. Based on the embodiments of the present utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present utility model.
[0023] First, the following explanations are provided for the terms that may be used in this article:
[0024] The term "and / or" means that either or both can be achieved simultaneously. For example, X and / or Y means that it includes both "X" or "Y" as well as the three cases of "X and Y".
[0025] The terms “including,” “comprising,” “containing,” “having,” or other similar semantic descriptions should be interpreted as non-exclusive inclusion. For example, “including a technical feature element (such as raw material, component, ingredient, carrier, dosage form, material, size, part, component, mechanism, device, step, process, method, reaction conditions, processing conditions, parameter, algorithm, signal, data, product or article of manufacture, etc.)” should be interpreted as including not only the expressly listed technical feature element, but also other technical feature elements that are not expressly listed and are well-known in the art.
[0026] The term "composed of" excludes any technical features not expressly listed. When used in a claim, it closes the claim to exclude all technical features other than those expressly listed, except for associated conventional impurities. If the term appears only in a clause of a claim, it limits the claim to the elements expressly listed in that clause; elements recited in other clauses are not excluded from the overall claim.
[0027] The contents not described in detail in the embodiments of this utility model are existing technologies known to those skilled in the art. Where specific conditions are not specified in the embodiments of this utility model, they shall be performed according to conventional conditions in the art or conditions recommended by the manufacturer. Reagents or instruments used in the embodiments of this utility model whose manufacturers are not specified are all conventional products that can be purchased commercially.
[0028] This utility model discloses a system for digital-to-analog conversion using superimposed pulse width modulation, including a controller, which acts as a multi-channel PWM generator and is correspondingly connected to a multi-channel digital-to-analog conversion circuit.
[0029] Each digital-to-analog converter circuit includes a Schmitt inverter, an adder amplifier, a filter smoothing circuit, and an output follower connected in sequence, wherein the output follower is provided with an analog output port.
[0030] The adder amplifier serves as a waveform superposition circuit for multiple timing output PWM waveforms.
[0031] The SN74LVC14 was used as a Schmitt inverter; the TL074 was used as a follower and adder amplifier; and ceramic capacitors were used as smoothing and filtering capacitors.
[0032] In summary, the system for digital-to-analog conversion using superimposed pulse width modulation (PWM) according to this invention is a method for converting digital signals to analog signals based on PWM technology and RC filters. Building upon PWM technology for digital-to-analog conversion, the system further improves the accuracy of the analog output signal by multiplying multiple waveforms to achieve PWM frequency multiplication. Therefore, this technology can solve the accuracy requirements in low-cost applications and is worthy of widespread adoption in product design.
[0033] This invention achieves high-precision, low-cost digital-to-analog conversion; further improves accuracy compared to a single PWM output scheme; and saves and frees up the controller communication interface in the system design.
[0034] To more clearly demonstrate the technical solution and effects provided by this utility model, the following detailed description of the embodiments of this utility model is provided with reference to specific examples.
[0035] Example 1
[0036] like Figure 1 The diagram shown is a technical block diagram of this technical solution.
[0037] This technical solution uses a controller as a PWM generator to generate PWM waveforms of different frequencies. In practical applications, the output PWM wave does not need to change its frequency in real time; a fixed output frequency only needs to be selected according to the accuracy requirements. Furthermore, the controller allows for easy modification of the PWM wave's duty cycle, thereby achieving output voltage adjustment.
[0038] Besides the controller, the main functional components involved in this technical solution include a Schmitt inverter, an adder amplifier, a filter smoothing circuit, and an output follower. The Schmitt inverter steepens the edges of the PWM wave output by the controller, ensuring the consistency and stability of the PWM wave duty cycle, thereby improving the accuracy of the digital-to-analog conversion. The filter smoothing circuit smooths the PWM square wave into a continuous analog output waveform by configuring appropriate RC parameters. The follower further filters the smoothed analog output signal, eliminating the influence of high-frequency signals on the output, while reducing the output impedance and improving the driving capability of the analog output signal. Its schematic diagram is shown below. Figure 2 As shown.
[0039] Example 2
[0040] Besides the aforementioned PWM voltage regulation scheme, another unique optimization in this technical solution is to improve the waveform quality and accuracy of the analog output by increasing the PWM output frequency. As is well known, the higher the PWM output frequency, the lower the ripple of the analog output waveform after PWM modulation and smoothing, and the higher its accuracy. Analog signals after digital-to-analog conversion are often used as reference sources, voltage references, output references, and other applications requiring high accuracy and low ripple. To meet the needs of such applications, the analog-to-digital converter must produce a high-quality output signal; therefore, increasing the output frequency of the PWM wave is the simplest and most effective solution. In practical applications, a common problem arises: since the number of bits in the counter is fixed, increasing the PWM output frequency inevitably sacrifices the adjustment resolution of the PWM duty cycle, thus affecting the overall output resolution of the digital-to-analog converter. Conversely, maintaining the output resolution of the digital-to-analog converter will affect the output frequency. If a method can be found to multiply the frequency while maintaining the output resolution, thereby effectively improving the output waveform quality of the digital-to-analog converter, the waveform quality of the PWM-modulated digital-to-analog converter output can be further improved.
[0041] like Figure 1 As shown, we propose using an adder circuit to superimpose the PWM waveforms output from multiple timers. By effectively controlling the phase of the PWM output waveforms, frequency multiplication of the output waveform can be achieved. The schematic diagram is shown below. Figure 3 .
[0042] In practical applications, using the SN74LVC14 as a Schmitt trigger inverter can make the edges of the PWM waveform steeper and neater, eliminating waveform edge distortion caused by parasitic parameters on the wires, and thus eliminating duty cycle errors caused by inconsistent rising and falling edges; using the TL074 as a follower and adder amplifier has the characteristics of high precision, and can improve the driving capability of the signal output, adapting to the driving of different back-end circuits; using ceramic capacitors as smoothing and filtering capacitors eliminates the impact of high-frequency noise on accuracy, while improving output quality.
[0043] The beneficial effects of this utility model are:
[0044] 1) A digital-to-analog converter built using a PWM generator in the controller and low-cost components such as Schmitt inverters, operational amplifiers, resistors, and capacitors can achieve a lower cost compared to an integrated analog-to-digital converter chip while maintaining the same accuracy and resolution.
[0045] 2) Based on the traditional PWM voltage regulation scheme, the output accuracy and waveform quality are improved by adjusting the PWM output waveform frequency and duty cycle in conjunction.
[0046] 3) By using the method of superimposing multiple PWM output waveforms, the output frequency can be doubled without affecting the digital-to-analog conversion resolution through output waveform phase control, thereby further improving the output accuracy and waveform quality.
[0047] In practical applications, a PWM generation circuit can be used to replace the controller in this solution to achieve PWM output. Alternatively, an inverter or Schmitt trigger can be used to replace the Schmitt inverter in this solution. Both can achieve digital-to-analog conversion in PWM mode in practical applications, but their fundamental principles are basically the same as those in this solution.
[0048] Key technical features of this utility model:
[0049] High-precision and high-quality analog-to-digital conversion output is achieved by using frequency and duty cycle linkage control.
[0050] By employing multi-channel PWM output waveform superposition and output waveform phase control, the accuracy of digital-to-analog conversion is improved without sacrificing the resolution.
[0051] The above description is merely a preferred embodiment of this utility model, but the scope of protection of this utility model is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this utility model should be included within the scope of protection of this utility model. Therefore, the scope of protection of this utility model should be determined by the scope of the claims. The information disclosed in the background section is intended only to enhance the understanding of the overall background technology of this utility model and should not be construed as an admission or implication in any way that such information constitutes prior art known to those skilled in the art.
Claims
1. A system for digital-to-analog conversion using superimposed pulse width modulation, characterized in that, Includes a controller, which acts as a multi-channel PWM generator and is correspondingly connected to multiple digital-to-analog conversion circuits; Each digital-to-analog converter circuit includes a Schmitt inverter, an adder amplifier, a filter smoothing circuit, and an output follower connected in sequence, wherein the output follower is provided with an analog output port.
2. The system for digital-to-analog conversion using superimposed pulse width modulation according to claim 1, characterized in that, The adder amplifier serves as a waveform superposition circuit for multiple timing output PWM waveforms.
3. The system for digital-to-analog conversion using superimposed pulse width modulation according to claim 2, characterized in that, The SN74LVC14 was used as a Schmitt inverter; the TL074 was used as a follower and adder amplifier; and ceramic capacitors were used as smoothing and filtering capacitors.