Textronix Power Supply Measurement Guide
-
Upload
tennis5luv -
Category
Documents
-
view
217 -
download
0
Transcript of Textronix Power Supply Measurement Guide
-
8/8/2019 Textronix Power Supply Measurement Guide
1/36
Power Supply Measurement andAnalysisWith Tektronix Oscilloscopes
February 2009
-
8/8/2019 Textronix Power Supply Measurement Guide
2/36
February 2009 Power Supply Measurement and Analysis2
Agenda
Todays Power Supplies
Switching Device Measurements
Magnetic Component Measurements
Power Line Measurements
Choosing the Right Solution
-
8/8/2019 Textronix Power Supply Measurement Guide
3/36
February 2009 Power Supply Measurement and Analysis3
Todays Power Supplies
Convert power from one form to another
Found in a wide range of applications
Many different kinds and sizes
Must be efficient
Face complex, dynamic operating environment
-
8/8/2019 Textronix Power Supply Measurement Guide
4/36
February 2009 Power Supply Measurement and Analysis4
The Basic Switch-Mode Power Supply
Active Components (Switch) Switching Loss
Safe Operating Area
Passive Components (Transformer)
Magnetic Power Loss
B-H Characteristics
VIN VOUT
Input Filter Switch Rectifier & FilterTransformer
PWM
Control Circuit
Feedback
LineVoltage
Power Line Harmonics
Power Quality
DC to DCConverter
DC to DCConverter
DC to DCConverter(s)
AC to DC Converter
Optional
-
8/8/2019 Textronix Power Supply Measurement Guide
5/36
February 2009 Power Supply Measurement and Analysis5
Agenda
Todays Power Supplies
Switching Device Measurements
Magnetic Component Measurements
Power Line Measurements
Choosing the Right Solution
-
8/8/2019 Textronix Power Supply Measurement Guide
6/36
February 2009 Power Supply Measurement and Analysis6
Active Component Measurements:Switching Devices
Transistor switch circuits dissipate themost energy during transitions
Common measurements:
Turn Off Loss
Turn On Loss
Power Loss
Slew Rate
Dynamic On Resistance
Safe Operating Area
SwitchI
OFF OFF OFFON ON
V
I
OFF ON ONOFF OFF
V
I
OFF ON ONOFF OFF
V
Ideal Switch
Real Switch
-
8/8/2019 Textronix Power Supply Measurement Guide
7/36
February 2009 Power Supply Measurement and Analysis7
Switching Loss Basics
Energy loss during the transition can beestimated by:
Where:
Eon is the energy loss in the switch
during the transition.
is the instantaneous voltage
across the switch.
is the instantaneous current
through the switch.
t1 is when the transition is complete.
t0 is when the transition begins.
The equation for Eoff is similar
)(tva
1
)()(
t
t
aaon
o
dttitvE
)(tva
)(tia
OFF ON
a(t)
ia(t)
t1t0
-
8/8/2019 Textronix Power Supply Measurement Guide
8/36
February 2009 Power Supply Measurement and Analysis8
Switching Loss Measurements
Tektronix MSO/DPO4000 Oscilloscope with DPO4PWR
As simple as measuring voltage across and current through the switch device.
Power analysis software will calculate Turn-On, Turn-Off and Conduction Losses.
Caution: timing between voltage and current waveforms must be precise.
-
8/8/2019 Textronix Power Supply Measurement Guide
9/36
February 2009 Power Supply Measurement and Analysis9
Safe Operating Area Measurements
Characterizes the operating regionof the device
Instantaneous Power is calculatedby:
Pn= VnIn
Where:
Pn is the instantaneous power.
Vn is the voltage. In is the current.
nis the sample point.
Test variables may include differentloads, operating temperatures, highand low line input voltages, andmore.
Tektronix MSO/DPO4000 Oscilloscope withDPO4PWR
-
8/8/2019 Textronix Power Supply Measurement Guide
10/36
February 2009 Power Supply Measurement and Analysis10
Active Component Measurements:Choosing the Right Measurement Solution
Signal SourceSimulate gate drive signalAdjustable duty cycle, edgetransition times, and frequency
Many need 12V to 15V output
OscilloscopeEnough bandwidth and rise time tohandle switching signal frequencycomponents
Fast sample rate to capture transitionsDeep record length for long acquisitions
ProbesAC/DC current probesDifferential probes to make
floating measurements
-
8/8/2019 Textronix Power Supply Measurement Guide
11/36
February 2009 Power Supply Measurement and Analysis11
Oscilloscope Performance Considerations
Rise Time Switching signal rise time may be quite fast
For accurate measurements, measurement system (oscilloscope + probe)rise time should be 5X faster
Meas. Sys. =Rise Time
5MeasuredRise Time
Meas. Sys.Rise Time
SignalRise Time
= +
2 2
Actual Measured
Signal Rise Time
-
8/8/2019 Textronix Power Supply Measurement Guide
12/36
February 2009 Power Supply Measurement and Analysis12
Oscilloscope Performance Considerations
Sample Rate Faster sample rate provides
greater resolution and detail of thewaveform
Record Length
Determines how much time iscaptured for given sample rate
An example:
A half-cycle of 60 Hz is over 8 ms
With sample rate of 1 GS/s, need 8Mpoint record length
Time =Record Length
Sample Rate
-
8/8/2019 Textronix Power Supply Measurement Guide
13/36
February 2009 Power Supply Measurement and Analysis13
Measurement Challenge: Skew Between Probes
To make a power measurement, must measure voltage across andcurrent through the switching device
Requires two separate probes: voltage and current
Each probe has its own characteristic propagation delay
Difference between two delays is skew
-
8/8/2019 Textronix Power Supply Measurement Guide
14/36
February 2009 Power Supply Measurement and Analysis14
An Example of Skew
9.4 ns skew4.958 W
5.239 W
de- skewed
5.6%Error
-
8/8/2019 Textronix Power Supply Measurement Guide
15/36
February 2009 Power Supply Measurement and Analysis15
Solution:Eliminating Skew Between Voltage and Current Probes
Tektronix DPO3000 Oscilloscope
with TekVPI probes and deskew kit
Deskew7.40 ns
-
8/8/2019 Textronix Power Supply Measurement Guide
16/36
February 2009 Power Supply Measurement and Analysis16
Measurement Challenge: Probe Offset
Differential and current probes may have a slight DC offset
Need to remove before taking measurements for highest accuracy
With 1 V DC offset,Conduction Loss = 86.13 mW.
With DC offset removed,Conduction Loss = 72.75 mW.
15.5%Error
-
8/8/2019 Textronix Power Supply Measurement Guide
17/36
February 2009 Power Supply Measurement and Analysis17
Solution: Eliminate Probe Offset
Short theprobeinputs
together
Push theAutoZero
button on theProbe Setup
Menu
-
8/8/2019 Textronix Power Supply Measurement Guide
18/36
February 2009 Power Supply Measurement and Analysis18
Solution: Degauss The Current Probe
Removes residual magnetic flux from probes magnetic components
Set the probearmature tothe Closed
position.
Push the
DegaussAutoZerobutton on theprobe Comp.
box.
-
8/8/2019 Textronix Power Supply Measurement Guide
19/36
February 2009 Power Supply Measurement and Analysis19
Agenda
Todays Power Supplies
Switching Device Measurements
Magnetic Component Measurements
Power Line Measurements
Choosing the Right Solution
-
8/8/2019 Textronix Power Supply Measurement Guide
20/36
February 2009 Power Supply Measurement and Analysis20
Passive Component Measurements:Magnetics
Focus on the inductors and transformer
Common measurements:
Magnetic Power Loss
Magnetic Properties
Input and Output Filters Transformer
-
8/8/2019 Textronix Power Supply Measurement Guide
21/36
February 2009 Power Supply Measurement and Analysis21
Magnetic Power Loss Basics
Magnetic Power Loss = Core Loss + Copper Loss
Core Loss Includes hysteresis loss and eddy current loss
Copper Loss
Due to resistance of the copper winding wire
-
8/8/2019 Textronix Power Supply Measurement Guide
22/36
February 2009 Power Supply Measurement and Analysis22
Magnetic Power Loss Measurements
Important to know different powerloss components to identify rootcause
Measure Total Magnetic Loss
Derive Core Loss from vendorsdata sheet
Solve for Copper Loss
Multiple-winding inductor:
Tektronix DPO7000 Oscilloscope with DPOPWR
321 LLL PowerLossPowerLossPowerLossLossTotalPower
-
8/8/2019 Textronix Power Supply Measurement Guide
23/36
February 2009 Power Supply Measurement and Analysis23
Hysteresis Curve Basics
Shows relationship between Band H
Characterizes the operating region of themagnetic component within the SMPS
Magnetic Field Strength:
Where:
Hk(t) is the magnetic field strength
Ik(t) is the magnetizing current N is the number of turns
l is the magnetic length
Flux Density:
Where:
S is the surface Area
l
NtItH
kk )()(
dttVkk )( )()( SNtBk
k
and
-
8/8/2019 Textronix Power Supply Measurement Guide
24/36
February 2009 Power Supply Measurement and Analysis24
Hysteresis Curve and Magnetic PropertiesMeasurements
Power measurement software greatly simplifies these measurementsMeasure voltage and magnetizing current
Input number of turns, magnetic length, and cross-sectional area
Software calculates magnetic properties like
Maximum Magnetic Flux Density, Remanence Flux Density
Permeability, Coercive Force
Also measure multi-winding magnetic elements
B-H plot for single winding inductor B-H plot for transformer
-
8/8/2019 Textronix Power Supply Measurement Guide
25/36
February 2009 Power Supply Measurement and Analysis25
Agenda
Todays Power Supplies
Switching Device Measurements
Magnetic Component Measurements
Power Line Measurements
Choosing the Right Solution
-
8/8/2019 Textronix Power Supply Measurement Guide
26/36
February 2009 Power Supply Measurement and Analysis26
Power Line Measurements
Line
Filter
Voltage Test Points
VAC
IAC
Current Test Point
(Non-intrusive AC/DC probe)
PFC
control
PWM
control
Characterize the interaction of the supply and its service environment
Must measure voltage and current directly on the input power line
Requires high-voltage probe, usually differential
-
8/8/2019 Textronix Power Supply Measurement Guide
27/36
February 2009 Power Supply Measurement and Analysis27
Power Quality Measurement Basics
In reality, input voltage and current waveforms are not identical
Real-world electrical power lines never supply ideal sine waves
A SMPS is a non-linear load to the source
SMPS creates harmonics on input current waveform which must notviolate standards like EN61000-3-2
Power Quality measurements include:
True Power
Reactive Power
Apparent Power
Power Factor
Crest Factor
Current Harmonics Measurements
THD
-
8/8/2019 Textronix Power Supply Measurement Guide
28/36
February 2009 Power Supply Measurement and Analysis28
Power Quality Measurements
Tektronix MSO/DPO4000 Oscilloscopewith DPO4PWR
Apparent Power = Irms * Vrms
Power Factor = True Power
Apparent Power
Crest Factor = Vpeak
Vrms
ReactivePowerTrue Power
Appa
rentPowe
r
Imaginary
Axis
Real Axis
-
8/8/2019 Textronix Power Supply Measurement Guide
29/36
February 2009 Power Supply Measurement and Analysis29
Harmonics and Pre-Compliance Measurements
Must capture up to 40th harmonic
Compare harmonics and THD toindustry standards like EN61000-3-2
Tektronix TDS5000B Oscilloscope with TDSPWR3
-
8/8/2019 Textronix Power Supply Measurement Guide
30/36
February 2009 Power Supply Measurement and Analysis30
Agenda
Todays Power Supplies
Switching Device Measurements
Magnetic Component Measurements
Power Line Measurements
Choosing the Right Solution
-
8/8/2019 Textronix Power Supply Measurement Guide
31/36
February 2009 Power Supply Measurement and Analysis31
Summary: Choosing the Right Solution
Determine your measurement requirements
What are the characteristics of your switching signal?
Do you need to analyze magnetic components?
Is Power Quality, and pre-compliance testing to standards like EN61000-3-2, important?
Carefully choose the right oscilloscope for your signal and needs Oscilloscope rise time, sample rate, record length Automated measurements and level of analysis required
Dont forget the probes!
AC/DC current probe High-voltage differential probe
Mid-voltage differential probe
Consider deskew options forbest measurement accuracy
T k i P M S l i
-
8/8/2019 Textronix Power Supply Measurement Guide
32/36
February 2009 Power Supply Measurement and Analysis32
Tektronix Power Measurement Solutions www.tektronix.com/power
NEW
MSO/DPO4000 d DPO3000 S i
-
8/8/2019 Textronix Power Supply Measurement Guide
33/36
February 2009 Power Supply Measurement and Analysis33
MSO/DPO4000 and DPO3000 Series:Power Supply Debug
Automated power measurements:
Power quality
Harmonics
Switching loss measurements
Safe Operating Area (SOA) Slew rate
Ripple
Modulation
Fast deskew of probes
Modulation
Safe Operating Area Switching Loss Power Quality
Harmonics
TDS5000B d DPO7000 S i
-
8/8/2019 Textronix Power Supply Measurement Guide
34/36
February 2009 Power Supply Measurement and Analysis34
TDS5000B and DPO7000 Series:In-depth Characterization of Power Supplies
Automated power measurements:
Switching loss, slew rate and SOA
Power quality and harmonics
Modulation and ripple
Magnetic components (core loss and BH curves) Spectral Analysis and Hi-Power Finder
Quickly generate customized reports
Automatically deskew probes
Hi-Power Finder
Magnetics
SpectralAnalysis
Power Quality
TPS2000 S i
-
8/8/2019 Textronix Power Supply Measurement Guide
35/36
February 2009 Power Supply Measurement and Analysis35
TPS2000 Series:Portable Power Troubleshooting
Isolated channels for floating or groundedmeasurements
Portable design with up to 8 hours of
continuous battery life
Integrated power measurements available:
Display watts, VA and VAR
Harmonics analysis
Switching loss analysis
Three-Phase Power Switching Loss Harmonics
P M t I f ti
-
8/8/2019 Textronix Power Supply Measurement Guide
36/36
Febr ar 2009 Po er S ppl Meas rement and Anal sis36
Power Measurement Informationwww.tektronix.com/power
Primer & application notes
Power measurement poster
Manuals