Measurement of Converter Efficiency Using Labview 2012. 11. 13 oungil Kim Dept. of EECS/CSE Seoul ational University
Introduction Measurement of converter efficiency We can automate experimentation using labview Multi-instrument automated experiment system can increase the work efficiency In this seminar, I will talk about why do we measure converter efficiency why experiment automation is necessary experiment setup labview programming result 2
Motivation A DC-DC converter is a critical component in modern embedded system Most embedded systems require multiple supply voltages. Hybrid electrical energy storage system need many DC-DC converter Charger conversion efficiency Significantly affected by the state of the energy source and energy storage or load power consumption The environment and system state change over time, and maximizing the system-wide efficiency is not trivial Many of paper consider about the efficiency of the DC-DC converter ongseok Choi, aehyuck Chang and Taewhan Kim, "DC-DC Converter-Aware Power Management for Low-Power Embedded Systems," in IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems (TCAD), Vol. 26, o. 8, pp. 1367-1381, Aug., 2007. ounghyun Kim, aehyuck Chang, anzhi Wang and Massoud Pedram, "Maximum Power Transfer Tracking for a Photovoltaic-Supercapacitor Energy System," in Proceeding of IEEE/ACM International Symposium on Low Power Electronics and Design (ISLPED), pp. 307--312, Aug., 2010. anzhi Wang, ounghyun Kim, Qing Xie, aehyuck Chang and Massoud Pedram, "Charge Migration Efficiency Optimization in Hybrid Electrical Energy Storage (HEES) Systems," in Proceedings of IEEE/ACM International Symposium on Low Power Electronics and Design (ISLPED), pp. 103-108, Fukuoka, Japan, 2011. 3
Efficiency of Converter Sources of power loss in converter ESR(Equivalent Series Resistance) of each component Parasitic capacitances of MOSFET switch gate Control circuitry Efficiency of the buck-boost converter is largely determined by its input voltage, output voltage, and output current The conversion efficiency is defined as = P out P in = V out I out V in I in = V in I in P converter V in I in Input, output voltage and input, output current should be measured 4
DC-DC Converter using LTC3789, LTC4000 High efficiency, synchronous 4-switch buck-boost controller Single inductor architecture allows Vin above, below or equal to the regulated Vout Programmable input or output current Wide input voltage range : 4V to 38V 5
Why experiment automation is necessary Measurement with labview Automatically measure input, output voltage and input, output current Input voltage range : 6V ~ 36V (interval : 1V) Output voltage range : 5V ~ 37V Output current range : 0.5A ~ 3A (interval : 0.5A) Total 186 experiment 6
Labview Labview is a system design platform and development environment for a visual programming language from ational Instruments Excution is determined by the structure of a graphical block diagram Advantage Extensive support for accessing instrumentation hardware Drivers and abstraction layer for many different types of instruments Many libraries with large number of functions Save program development time 7
Labview Control system can be divided into four parts Application program : Program designed to perform a specific function (Labview) VISA : I/O API (I-VISA) Instrument Driver : Set of software routines that control a programmable instrument Communication protocol : System of digital message format and rules(gpib, Serial, USB) Application Program VISA Instrument Driver PXI GPIB, USB, Serial, Ethernet VXI 8
Labview Labview programs are called virtual instruments(vis) Each VI has two components block diagram : Instruction set for controls, indicators (Source code) front panel : input data or extract data from a running virtual instrument Panel Toolbar! Pull-down! menu! Pull-down! menu! Boolean! Control! Double! Indicator! Data! Acquisition! Function! Delay! Thermometer! Terminal! Temperature! Indicator! While Loop! Stop Loop! Terminal! Waveform Graph! 9
Labview Controls Palette (Front Panel Window) Functions Palette (Block Diagram Window) 10
VISA Virtual Instrument Software Architecture Widely used I/O API in the test and measurement for communicating with instrument from a PC VISA provide the programming interface between the hardware and development environments (GPIB, VSI, PXI, Serial, Ethernet, USB) I-LabVIEW instrument drivers are based on the Virtual instrument drivers are based on the VISA standard download : http://joule.ni.com/nidu/cds/view/p/id/2659/lang/ko I-VISA I-488.2 I-VXI System Standard Driver PXI GPIB VXI LA/USB/Serial/Parallel 11
GPIB General Purpose Interface Bus Short-range digital communications bus specification Specifically designed to connect computers, peripherals and laboratory instruments 12
Serial communication Serial communication is the process of sending data over communication channel Serial communication send one bit at a time For serial communication applications, many terminal application can be used (ex. Realterm, TeraTerm, ComPortMaster, and so on...) 13
Measurement&Automation Explore(MAX) Graphical user interface to configure devices State caching : maintain the value of each instrument attribute setting Create and configure a logical name Configure a driver session Check that the device is working properly 14
Experiment setting Input : Range of voltage and current that we want to measure Output : Measured data in text format Super capacitor have wide range of charging voltage Active electric load Discharge Charge Supercapacitor Power supply V in I in Charger V out I out DAQ 15
Program flowchart Initialize Set the initial values - Power supply - Uart setting - Active load - Converter dir Set the Values - Set the current limit of power supply - Set OCP Control Charger - ichg current -vtrack 40 Power supply on Active load off Voltage = initial_value Write to measurement file Read the voltage of super capacitor Cap_voltage < 36.5 Increase the voltage Voltage < limit Set the voltage limit of power supply Finish Control the charger - ichg 0 - vtrack 0 Active load on Current = initial_value Read the voltage of super capacitor Increase the current Current < limit Cap_voltage < 36.5 Active load off 16
Program flowchart Initialize Set the initial values - Power supply - Uart setting - Active load - Converter dir Power supply on Active load off Voltage = initial_value Increase the voltage Voltage < limit Set the voltage limit of power supply Finish Current = initial_value Increase the current Current < limit Active load off 17
Program flowchart Converter dir Prevent power supply from turning off because of rush current 18
Program flowchart Initialize Set the initial values - Power supply - Uart setting - Active load - Converter dir Power supply on Active load off Voltage = initial_value Increase the voltage Voltage < limit Set the voltage limit of power supply Finish Current = initial_value Increase the current Current < limit Active load off 19
Program flowchart set the voltage limit Initial voltage Initial current 20
Program flowchart Initialize Set the initial values - Power supply - Uart setting - Active load - Converter dir Power supply on Active load off Voltage = initial_value Increase the voltage Voltage < limit Set the voltage limit of power supply Finish Current = initial_value Increase the current Current < limit Active load off 21
Program flowchart if(voltage == limit) if(current < limit) 22
Program flowchart Set the Values - Set the current limit of power supply - Set OCP Control Charger - ichg current -vtrack 40 Write to measurement file Read the voltage of super capacitor Cap_voltage < 36.5 Control the charger - ichg 0 - vtrack 0 Active load on Read the voltage of super capacitor Cap_voltage < 36.5 23
Program flowchart Set current limit of power supply Set OCP uart : vtrack 40 24
Program flowchart Set the Values - Set the current limit of power supply - Set OCP Control Charger - ichg current -vtrack 40 Write to measurement file Read the voltage of super capacitor Cap_voltage < 36.5 Control the charger - ichg 0 - vtrack 0 Active load on Read the voltage of super capacitor Cap_voltage < 36.5 25
Program flowchart Write to measurement file Read the Voltage of super capacitor 26
Program flowchart Set the Values - Set the current limit of power supply - Set OCP Control Charger - ichg current -vtrack 40 Write to measurement file Read the voltage of super capacitor Cap_voltage < 36.5 Control the charger - ichg 0 - vtrack 0 Active load on Read the voltage of super capacitor Cap_voltage < 36.5 27
Program flowchart if(cap_voltage>=limit) 28
Program flowchart Set the Values - Set the current limit of power supply - Set OCP Control Charger - ichg current -vtrack 40 Write to measurement file Read the voltage of super capacitor Cap_voltage < 36.5 Control the charger - ichg 0 - vtrack 0 Active load on Read the voltage of super capacitor Cap_voltage < 36.5 29
Program flowchart case is changed from 0 to 1 30
Program flowchart Set the Values - Set the current limit of power supply - Set OCP Control Charger - ichg current -vtrack 40 Write to measurement file Read the voltage of super capacitor Cap_voltage < 36.5 Control the charger - ichg 0 - vtrack 0 Active load on Read the voltage of super capacitor Cap_voltage < 36.5 31
Program flowchart uart : vtrack 0 uart : ichg 0 32
Program flowchart finish 33
Program flowchart Initialize Set the initial values - Power supply - Uart setting - Active load - Converter dir Power supply on Active load off Voltage = initial_value Set the Values - Set the current limit of power supply - Set OCP Control Charger - ichg current -vtrack 40 Write to measurement file Read the voltage of super capacitor Cap_voltage < 36.5 Increase the voltage Voltage < limit Set the voltage limit of power supply Finish Control the charger - ichg 0 - vtrack 0 Active load on Current = initial_value Read the voltage of super capacitor Increase the current Current < limit Cap_voltage < 36.5 Active load off 34
Program flowchart Initialize Set the initial values - Power supply - Uart setting - Active load - Converter dir Power supply on Active load off Voltage = initial_value Set the Values - Set the current limit of power supply - Set OCP Control Charger - ichg current -vtrack 40 Write to measurement file Read the voltage of super capacitor Cap_voltage < 36.5 Increase the voltage Voltage < limit Set the voltage limit of power supply Finish Control the charger - ichg 0 - vtrack 0 Active load on Current = initial_value Read the voltage of super capacitor Increase the current Current < limit Cap_voltage < 36.5 Active load off 35
Program flowchart Initialize Set the initial values - Power supply - Uart setting - Active load - Converter dir Set the Values - Set the current limit of power supply - Set OCP Control Charger - ichg current -vtrack 40 Power supply on Active load off Voltage = initial_value Write to measurement file Read the voltage of super capacitor Cap_voltage < 36.5 Increase the voltage Voltage < limit while loop Set the voltage limit of power supply Finish Control the charger - ichg 0 - vtrack 0 Active load on Current = initial_value Read the voltage of super capacitor Increase the current Current < limit Cap_voltage < 36.5 Active load off 36
Labview Front panel 37
Labview We can acquire the data in text format 38
Result = f(v in,v out,i out ) 3D interpolation using MATLAB 3A 6V 0.5A 5V 36V 37V Vin Vout 39
Result 40
Result 41
Result 42
Conclusion Successfully measured the efficiency of the converter using labview We can automate the experiment process Laview does much to improve the efficiency of experiments There can be many other application 43