“The application of digital signal processing (DSP) control in power supplies and power supply systems has brought enormous benefits. From communication and control to enabling networked factories and efficient smart manufacturing, known as Industry 4.0, the Fourth Industrial Revolution or more broadly as the Internet of Things (IoT), through communication and control within end devices and/or Tailored to achieve flexibility and efficiency in stand-alone applications, power is provided during the end-device development phase to ensure efficient integration and optimized performance characteristics.
The application of digital signal processing (DSP) control in power supplies and power supply systems has brought enormous benefits. From communication and control to enabling networked factories and efficient smart manufacturing, known as Industry 4.0, the Fourth Industrial Revolution or more broadly as the Internet of Things (IoT), through communication and control within end devices and/or Tailored to achieve flexibility and efficiency in stand-alone applications, power is provided during the end-device development phase to ensure efficient integration and optimized performance characteristics.
Here we present the background, possibilities and benefits offered by true digital control when integrating power supplies and power systems into connected and independent applications and devices.
Digital control in power supplies and power systems is broadly divided into two implementations. A more common approach is to create a digital interface between a traditional analog control system and the outside world, providing signals and alarms and various levels of control over a communication bus.
Analog power supply with digital interface
Simple, low-cost microcontrollers have also implemented functions in power applications for many years, such as fan speed control, protection functions, and alarm detection.
More and more manufacturers are using digital signal processing (DSP) for power system control through microcontrollers, bringing more advanced functionality, greatly enhancing flexibility, and enabling user-programmable features and characteristics.
There is no doubt that DSPs cost more than off-the-shelf analog controllers, but the cost of microcontrollers capable of full DSP control has decreased over time, making this a An increasingly attractive and desirable solution as it offers significant benefits, especially as power ratings increase. The required mixed-domain architecture, combining power analog design principles with efficient code and control loop stability in the discrete-time or z-domain (rather than the frequency or s-domain), has been designed into products by major power manufacturers And the development team is fully proven and understood.
While developing, documenting, validating, and approving efficient, reliable firmware requires significant time and resources to ensure reliable power, once the initial investment has been made, the significant benefits of digital power can be realized and enabled across a wide range of products and platforms Reuse firmware with relatively minor changes.
The advantage of a digital control loop is its insensitivity to changes in environment, temperature, aging and component tolerances. They can be calibrated at the point of manufacture to further improve accuracy, and can monitor the performance of the power system in real time and adjust parameters for optimal performance tuning at the point of operation to improve efficiency and reduce power loss.
Digital Signal Processing (DSP) Features and Benefits
All-digital power supplies provide unmatched flexibility and adjustability to suit a wide range of applications without the hardware changes and adaptations required by traditional analog control systems.
The digital signal processor (DSP) control loop adjusts the converter’s operating mode as required, so that the output voltage and current can be adjusted in the range of 0-105-110%. They simplify the implementation of the constant current overload characteristic, which is complex and expensive in modern resonant switching topologies, without sacrificing efficiency. This requires multiple switching schemes and control algorithms in the same power conversion stage to achieve optimum performance at the desired operating point, an extremely complex task, if not impossible, in conventional systems with fixed hardware The same is true in analog control schemes for drive and compensation schemes. This wide-range control can be implemented as a continuously variable power supply to maximize system flexibility and efficiency, or utilized during the system development phase to optimize the supply characteristics of an application without requiring hardware updates.
The DSP also allows the user to determine in software startup ramp times, soft-start characteristics and slew rate, another characteristic that has led to hardware changes in traditional control systems.
Users can set alarm levels and fault conditions such as input overvoltage/undervoltage, output overvoltage/undervoltage, output undercurrent/overcurrent, temperature alarm and fault conditions through software to suit the application. The use of DSP also allows the user to specify the type of response and delay time that should be applied to individual warning or fault conditions. Options may vary for warning or fault conditions, such as continue operation for a short delay, then disable, continue operation indefinitely, disable and retry (including number of retries and retry interval before shutdown), and on OK or disable and disable and restore when locked, all functions are user-selectable.
The digital control system also allows the user to set the polarity of signals, alarms and controls to suit system needs. A good example is setting the remote on/off control to disable or enable by toggling a digital switch.
Information from the power system is readily available through the communication interface for reporting and status, such as model, version, serial number, operating hours, operating temperature and fault/event logs.
This level of flexibility and user control is possible because the latest microcontrollers for digital power applications include DSP functionality, allowing the digital control loop to execute within a fraction of a switching cycle, each switching cycle. In the simplified example below, the output voltage is sampled once per switching cycle. Typical ADC conversion times are a few hundred nanoseconds.
Simplified example of control loop and spare bandwidth
The time that the MCU does not spend executing the controller is free bandwidth that can be used to perform other tasks or functions. Low priority tasks run in a slow loop and are interrupted when high priority tasks occur, such as ADC interrupts to run control loop code.
By using an analog-to-digital converter (ADC) in the power supply, analog control of a digital power supply is usually also suitable for systems using traditional 0-5V or 0-10V control signals, and all alarms and controls are usually available via conventional connections as well as via communication bus.
Communication and control are increasingly important with the rise of connected, smart factory and IoT applications that benefit from real-time status information from power systems as well as adjustment and control inputs, allowing real-time adjustments to maximize the efficiency of the process Benefit from accurate voltage and/or current supply and the ability to adjust these to suit the environment and application.
In addition to the ability to adjust output voltage, current, and power delivery in real time to maximize system efficiency in sensitive processes or test applications, digital power products can report warnings, fault conditions, power delivery information, runtime, temperature data, and event logs.
From the commonly used I2C/PMBUS and RS232/RS485 serial buses to interface solutions supporting DeviceNet and Ethernet, there is a range of digital interfaces and solutions to choose from to suit a variety of environments, applications and requirements.
While not all end applications require communication with the outside world, the ability to communicate and adjust parameters of the power system within the end device can enhance functionality and operational characteristics, potentially by replacing the external hardware controls required by traditional fixed output power supplies to save costs. A digital signal processor-enabled power supply can support the dynamic requirements for output voltage, current, and power supply output typically associated with higher-cost laboratory power supplies, with tolerances allowed, and can be derived directly from a cost-effective power supply Perform complex testing, burn-in and handling procedures.
In end devices that do not require external or internal communications, there are still benefits to adapting the power supply to the application, simplifying integration, and eliminating the need for application-specific solutions that require modifications to standard or custom power supply solutions.
Output voltage, output current, power output, warnings, alarms, protections and controls can be adjusted, evaluated, modified and finalized during the development phase, creating a unique set of characteristics in firmware that is then produced by the power supplier in the final device Phase manufacturing point implementation. Iterations of these features can be implemented on the same standard products, saving considerable time and cost compared to the hardware changes required for traditional power products.
End applications using analog control for voltage or current regulation still benefit from the ability to redefine the warning and fault condition settings, responses and polarity settings for alarm and control signals without resorting to the time-involved R&D, EMC and safety approvals required Delays, risks, costs for specific applications or fully customized power solutions.
Manufacturers of digital power supplies often provide a graphical user interface (GUI) that enables users to define requirements for this purpose and to quickly assess the ability to connect applications. Below is a typical example.
Graphical User Interface (GUI) for XP HPT Series Digital Power Supplies
In conclusion, in many, often higher power (1kW+) applications of power supplies and power systems, there are many clear, achievable advantages to implementing DSP control, which benefit from flexibility as well as time and cost savings. For simple, low-power applications, which can be overly complex and costly, standard off-the-shelf analog controllers can be brought to market quickly while being inexpensive to acquire for commonly used topologies.