Download Switched-mode power supply charger

Switched-mode power supply charger
Final presentation
Aarne Liski
Jere Kinnunen
Original problem description
• The project is about designing an approximately 325VDC charger, that
can output approximately 10A. Power is taken from a 230 VAC 16 A
plug. The efficiency should be over 90% and the size of the charger
should be minimized by using switching frequency as high as possible.
The charger is designed for liquid cooling. The SMPS could be
implemented for example with MOSFET-components. Literature:
Pressman, Billings, Morey; Switching Power Supply Design
Our solution
• A SMPS that is implemented with H-bridge topology driving the primary of
a HF-transformer with center tapped secondary circuit. The H-bridge
control signals are modulated with Phase shift modulation and a ZeroVoltage Switching is realized for transistor turn ons to minimize switching
losses.
• Uses Infineon SPP20N60CFD CoolFET-MOSFETs for the H-bridge and Texas
Instruments UCC27714 High/Low-side drivers to drive the MOSFETS
• Phase shift modulation and ZVS adaptability produced with a Linear
Technologies LTC3722-1 PSM IC
The schematic
Simulation
• The simulation circuit uses different MOSFET’s and drivers due to lack
of models.
• This should still give a good idea on the actual functionality of the
circuit
Simulation example
Transformer voltage 1
Transformer voltage 2
Output
Currentvoltage
through a
single MOSFET
Simulation example (ZVS)
Voltage over the transistor
Transistor drain current
Gate signal
Thermal modelling
Thermal simulation results
Junction temperature (V=T)
Case temperature (V=T)
Thermal simulation results
Junction temperature (V=T)
Case temperature (V=T)
Loss power switching (A=P)
Loss power conducting (A=P)
Main issues with the design
• The DC-bus voltage has to be kept at a certain level for succesful
realization of the output reference
• The line supply can input power into the circuit only when the line
voltage is above the voltage of the output of the input rectifier
Main issues with the design
DC-bus voltage
Rectified AC voltage
Current drawn from
the line supply
Main issues with the design
• Storing energy into a DC-capacitor bank is not the main issue since
electrolytic capacitors are relatively cheap
• Still a DC-capacitor bank of this size would be the second most expensive
component of this design after the high frequency transformer
• The main issue is that the fuses are sized for the I^2t value of the
input current so to use a 230VAC 16A supply to produce 3.25kW
output we would need a very good power factor
Proposed modifications to current design
• There were two solutions proposed in order to lengthen the time
during which energy can be drawn from the line input and to increase
the power factor
• 1. Increase the transformer ratio to allow for lower DC-bus voltage
• 2 Use a passive choke to aid storing energy and correct the power factor
Problem with solution 1.
• Because of the increased turns ratio the secondary side rectifier
diodes need to withstand huge voltages when the input is highest
(close to 325VDC)
• 1.2kV is a practical limit with stock-made components that are
feasibly priced considering this application
• The max input current was still over 45 amps when this limit was reached
Problem with solution 1.
Secondary rectifier diode
voltage stress
DC-voltage
Input current from the line
Problem with solution 2. (choke)
• Passive chokes are very bulky and expensive
• Choke of this size would also introduce considerable losses
• Chokes of this size are not made to stock
• The goal was to design a SMPS that is affordable, lightweight and
small and this solution is none of these
Alternative designs for a functional SMPS
Alternative 1: A solution to meet the original design specification
• Active Power Factor Correction
Alternative 2: A solution for the desired application, but does not meet
the initial specification
• 3-phase AC input (560VDC) with choke
Alternative 1: Active Power Factor Correction
• The idea is to use an active input side to allow current being drawn
from the input lines for the whole line input period
Alternative 1: Active Power Factor Correction
• Pros:
•
•
•
•
Superior power factor achievable
Excellent harmonic performance
Compact and lightweight
Probably cheapest manufacturing costs
• Cons:
• More components
• Increased complexity
• New source of EMI
Alternative 2: Three phase supply with choke
• Pros:
• Effective frequency six times higher than 1-phase
• Capacitor bank size can be reduced
• Choke can be smaller
• Simple and robust
• Cons:
• More expensive components
• 3-phase input rectifier
• Input side components require higher voltage rating
Three phase supply with 3mH choke
DC-voltage
Current of U-phase
U phase voltage
W-phase voltage
V-phase voltage
Bill of Materials costs for different alternatives
• Passive input without choke
• ~142€
• Passive input with choke
• Reference price couldn’t be found due to abnormally sized choke
• Power Factor Correction
• ~160+€
• Extra design effort considerable
• 3-phase AC input (560VDC)
• ~211€
Future work
• If a single phase input is pursued
• More study and design effort into Active Power Factor Correction
• If the single phase input is not a necessity
• A 3-phase SMPS can be realized with moderate amount of work
Risks that realized
• One group member dropped off the course
• A major amount of time spent fighting with the simulation models
• In general, time was used on quite a lot of paths that did not actually work
towards our final design
Plan vs. reality
Questions?