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EE467-567'10_lect6-F - EE 467/567 INTEGRATED POWER ELECTRONICS Dr Douglas C Hopkins Dept of Electrical Engineering University at Buffalo

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EE467/567 Integrated Power © 2010, D. C. Hopkins [email protected] EE 467/567 -- INTEGRATED POWER EE 467/567 -- INTEGRATED POWER ELECTRONICS ELECTRONICS Dr. Douglas C. Hopkins Dept. of Electrical Engineering University at Buffalo [email protected] EE467/567 Integrated Power © 2010, D. C. Hopkins [email protected] General Converter Efficiencies General Converter Efficiencies
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EE467/567 Integrated Power © 2010, D. C. Hopkins [email protected] A: The designer should make sure the dissipation is even so that no single device will limit the system. The total loss can be up to 6x50 W = 300 W. At 95% efficiency , P out /P in =0.95 and P in -P out < 300 W . Result: P out < 5700 W. Efficiency Examples Efficiency Examples Q: (Typical example) A converter is 95% efficient, and uses six power MOSFETs as switches. Each device can safely dissipate up to 50 W of power loss. What is the system ‘output power’ limit? CLASS DISCUSSION: A good design practice is to assume the devices will only share within a certain percentage of each other. The discrepancies come from individual device characteristics and dissimilar heating on the heat sink. Q: If a general 10% differential in R ds-on and switching loss can occur, what should be the maximum P out ? EE467/567 Integrated Power © 2010, D. C. Hopkins [email protected] Efficiency Examples Efficiency Examples Q: We want a power converter to provide up to 100 kW output for an electric vehicle application. The control power is 100 W. The total dissipation in the converter must not exceed 1000 W. What converter efficiency is required? A: Since the controls already dissipate 100 W the converter hardware must not dissipate more than 900 W. This means P in – P out < 900 W . Since P out = 100kW , the efficiency ! = P out /P in must be > 99.1% . Q: What if the efficiency is “only” 98%? A: At 100kW output, the dissipation will be 2040W plus the 100W control. The total is more than double the limit, and the system is likely to fail quickly. Or we could limit the output to 44kW, but this is less than half of what is needed! To attain high power levels, we need devices that are: Extremely efficient, can dissipate a lot of power (or both!). The devices are selected in part, by efficiency. Their packages and cooling are selected to permit high dissipation.
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EE467/567 Integrated Power © 2010, D. C. Hopkins [email protected] Homework Homework HW NOT SHOWN EE467/567 Integrated Power © 2010, D. C. Hopkins [email protected] Switching Converters Switching Converters The linear circuits so far cannot provide 100% efficiency. We need “Power Switching Circuits.” Two types: “Inductive Switching Circuits” “Capacitive Switching Circuits”
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EE467/567 Integrated Power © 2010, D. C. Hopkins [email protected] 2,2 1,2 1,1 2,1 2,2 1,2 1,1 2,1 Direct DC-DC Converters Direct DC-DC Converters Two possibilities of general dc-dc conversion: 2 x 2 matrix, voltage in, current out 2 x 2 matrix, current in, voltage out.
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This note was uploaded on 02/04/2011 for the course EE 587 taught by Professor Dr.mohammedsafiuddin during the Spring '11 term at SUNY Buffalo.

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EE467-567'10_lect6-F - EE 467/567 INTEGRATED POWER ELECTRONICS Dr Douglas C Hopkins Dept of Electrical Engineering University at Buffalo

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