With the availability of new low-cost, high-performance microcontrollers (MCUs), the benefits of digital power control can be introduced to a wide range of embedded, industrial and control applications. Traditional analog systems are susceptible to factors such as drift, aging of components, variations caused by temperature and component tolerance degrading. Developers are also limited to classical control implementations. In addition, analog-based systems offer little flexibility to accommodate different environmental operating conditions or even simple changes in system requirements.
When designed using a digital approach, portions of the power system can be implemented in software, resulting in a level of flexibility that enables a single architecture to provide optimal performance across a range of applications and operating conditions. With software-based control algorithms, developers can:
- Ensure precise and predictable system behavior through configuration – both in the factory and at power up – to adjust for component tolerance issues
- Improve efficiency through the use of advanced algorithms (i.e., non-linear, multi-variable, etc.), which are not feasible to implement in analog-based systems
- Maintain performance over an extended system lifetime through dynamic recalibration
- Support multiple systems with a single controller
- Increase system reliability through self-diagnostics
- Enable intelligent management through a communications link
- Simplify system design by allowing developers to work with model tools and C rather than having to rework analog designs with every requirement change
- Reduce system cost by supporting other system functions on the same MCU
This article describes a digital power control implementation using LLC (line level control) resonant converters based on a flexible, 32-bit, low-cost, high-performance microcontroller. Key elements of digital power control will be explored; including duty cycle control, dead-band adjustment in real time, frequency control, and adaptive thresholds for maintain different safe operation regions.
Tuning of the voltage compensator using coefficients during an active load will show the flexibility of the implementation, and the use of programmable soft start/stop capabilities and slew rate control will demonstrate how to avoid inrush current and reduce audible noise. Finally,