søren poulsen, [email protected] Ørsted·dtu, automation technical university of denmark norpie...
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NORPIE 2004 1
Søren Poulsen, [email protected]
Ørsted·DTU, AutomationTechnical University of Denmark
Hysteresis Controller with constant switching frequency
Søren Poulsen
Ph.D. Student
Ørsted·DTU
Technical University of Denmark
Michael A. E. Andersen
Professor
Ørsted·DTU
Technical University of Denmark
NORPIE 2004 2
Søren Poulsen, [email protected]
Ørsted·DTU, AutomationTechnical University of Denmark
Standard hysteresis controllers
• Current or voltage mode
NORPIE 2004 3
Søren Poulsen, [email protected]
Ørsted·DTU, AutomationTechnical University of Denmark
Band pass current mode
• Current loop with bandpass function– Only control of output filter resonance
NORPIE 2004 4
Søren Poulsen, [email protected]
Ørsted·DTU, AutomationTechnical University of Denmark
Hysteresis controllers• Benefits
– Sawtooth shaped carrier• Linear modulation
– Modulator includes power stage• Error reduction
– Open loop bandwidth = fs
• Concerns– Switching frequency dependent on modulation
index: 2,0 1s sf M f M
NORPIE 2004 5
Søren Poulsen, [email protected]
Ørsted·DTU, AutomationTechnical University of Denmark
Constant switching frequency hysteresis modulators
• Variable FW gain– Hysteresis clamp– Variable gain amp
NORPIE 2004 6
Søren Poulsen, [email protected]
Ørsted·DTU, AutomationTechnical University of Denmark
Constant switching frequency hysteresis controller
• Hysteresis controller with additional comparator and integrator
NORPIE 2004 7
Søren Poulsen, [email protected]
Ørsted·DTU, AutomationTechnical University of Denmark
Carrier distortion
• Control output WILL have HF content– Adds to the carrier
– Adding control decreases performance of inner modulator loop
• Shaping inner/outer loops in a way so control output inherently adds to carrier constructively
NORPIE 2004 8
Søren Poulsen, [email protected]
Ørsted·DTU, AutomationTechnical University of Denmark
Shaping modulator and feedback
NORPIE 2004 9
Søren Poulsen, [email protected]
Ørsted·DTU, AutomationTechnical University of Denmark
Constant switching frequency prototype
• Very low cost implementation
• fs,0 150kHz• Closed loop bandwidth = 30kHz• Modulator loop propagation delay: 325ns
NORPIE 2004 10
Søren Poulsen, [email protected]
Ørsted·DTU, AutomationTechnical University of Denmark
Constant switching frequency prototype
• 2-layer PCB
• +/- 40V supply
NORPIE 2004 11
Søren Poulsen, [email protected]
Ørsted·DTU, AutomationTechnical University of Denmark
Prototype carriers
NORPIE 2004 12
Søren Poulsen, [email protected]
Ørsted·DTU, AutomationTechnical University of Denmark
Prototype switching frequency, M=0.8, 10Hz, 100Hz, 1kHz
NORPIE 2004 13
Søren Poulsen, [email protected]
Ørsted·DTU, AutomationTechnical University of Denmark
Prototype switching frequency, DC
NORPIE 2004 14
Søren Poulsen, [email protected]
Ørsted·DTU, AutomationTechnical University of Denmark
Conclusion• Almost constant switching frequency
for low frequency modulation• Very simple modulator design• Low cost implementation possible• Additional feedback without distorting
the carrier is possible• ”Perfect” first carrier signal despite
only passive modulator loop