1 Digitally Controlled Converter Digitally Controlled Converter with Dynamic Change of Control Law with Dynamic Change of Control Law and Power Throughput and Power Throughput Carsten Nesgaard Michael A. E. Andersen Nils Nielsen Technical University of Denmark in collaboration with
18
Embed
Digitally Controlled Converter with Dynamic Change of Control Law and Power Throughput
Digitally Controlled Converter with Dynamic Change of Control Law and Power Throughput. Carsten Nesgaard Michael A. E. Andersen Nils Nielsen Technical University of Denmark in collaboration with. Outline. Power system specifications The microcontroller - PowerPoint PPT Presentation
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
1
Digitally Controlled Converter with Dynamic Digitally Controlled Converter with Dynamic Change of Control Law and Power ThroughputChange of Control Law and Power Throughput
Carsten Nesgaard Michael A. E. Andersen Nils Nielsen
Technical University of Denmark
in collaboration with
2
OutlineOutline
• Power system specifications
• The microcontroller
• Control algorithm and efficiency
• Analytical redundancy concept
• Reliability
• Experimental verification
• Further work
• Conclusion
3
Power system specificationsPower system specifications
• Simple buck topology with measurements of input voltage, input current, output voltage and output current
• Microcontroller for converter control and thermal monitoring
Power switch Filter
PIC16F877microcontroller
12V Input 5V Output
Temp
Duty-cycle
Input current
Input voltage
Output current
Output voltage
1A MAX
4
The microcontrollerThe microcontroller
8-bit RISC PIC16F877 microcontroller from Microchip
Core features: Uses:
8K 14-bit word flash memory 256 E2PROM data memory
10-bit PWM module8 channel 10-bit A/D converter
Single cycle operations20 MHz clock frequency
Algorithm and look-up table
Converter control
Execution speed
5
Control algorithm and efficiencyControl algorithm and efficiency
• Simple buck topology with measurements of :
• Thermal monitoring
• PWM control law for power throughput above 1.85 W
• PS control law for power throughput below 1.85 W
• Look-up table control when operated within specifications
Input voltage Input current Output voltage Output current
6
Control algorithm and efficiencyControl algorithm and efficiency
Software data flow diagram:
System init
Measure inputvoltage
ADC interrupt
If n=100measure
temperature
Timer interrupt
Convertercontrol in'real-time'
Checktemperatureand deduce
converter state
Shut-downconverter
Measure V OUT ,V IN , I OUT , I IN andcalculate power
Change incontrol law
Main
Interrupt routine
Request sample
Control law
Sample
Outside spec.
Within spec.
Within spec.
Within spec.
Outside spec.
Outside spec.
Converter OK
Converter failed
Interrupt routine responsible for correct converter control
Main loop responsible for temperature measurement, cal-culation of correct control law and type of calculation method (look-up or real-time)
• Graph theoretical approach is used for thorough system analysis
• Columns identify the lines interconnecting the individual blocks
• Line arrows indicate direction of power or data flow
Block level buck converter
18
ConclusionConclusion
A buck converter controlled by a low-cost PIC microcontroller has been presented. The system use analytical redundancy, change in control law and thermal monitoring for increased reliability.
Also, an introduction to the proposed techniques has been given supported by calculations concerning the pros and cons of the individual techniques.
Finally, a set of measurements has verified that the algorithm is indeed capable of performing the required tasks within the timing limitations of the microcontroller.