This presentation “Today's Power Supply; More Than a Battery With a Knob" shows how the features and capabilities of a modern power supply can solve many power problems. Agilent Technologies offers a broad selection of both bench-friendly and system-ready DC power supplies from 2W to 6600W.

1. Today's Power Supplies;
More Than a Battery With a Knob
Today’s Power Supplies: More Than
a Battery With a Knob www.agilent.com/find/power Page 1

2. Agenda:
• Categories of Power Supplies
• How People Use Power Supplies
• Selecting the Right Power Supply
• Output Characteristics (Ripple, Noise, Speed, Accuracy)
• Control via Computer and/or Analog Inputs
• Output Measurement/Monitoring Capabilities
• Packaging (Size, Number of Outputs, Front/Rear Terminals)
• Special Capabilities (DUT protection, Output Disconnect/Reversal)
• Unique Features and Capabilities
• Sequencing of Multiple Outputs
• Power Arbitrary Waveforms with List Mode
• Noise and Shielding / Hints and Tips
• Tricks of the Trade
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3. Power Supply Categories
• Basic Supplies
• Manual or Programmable
• Used for setting bias, powering circuits, etc.
• Performance Supplies
• Faster, more accurate, higher power
• Typically used in system applications
• Modular Supplies
• Compact, flexible, mix-and-match
• Easily interconnected
• Specialty Supplies
• Battery Simulation
• Solar Array Simulation
• Open Frame Supplies
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4. What do People do with Power Supplies?
Task Meaning Power Supply Required
Basic DC Bias •Set the output to one voltage or current Basic Power Supply (PS)
to power the Device Under Test (DUT)
Burn-in •Lots of power or lots of channels Basic PS
Margin Testing Depends on
•Test DUT at a variety of points
in DUT operating range Basic PS required speed
•Speed can be important or or on required
if high throughput is required or Performance PS accuracy
if DUT is being tested at a lot of different points of V setting
Turn-on and •Multiple outputs must be sequenced Performance PS
Inrush Testing •Measure how much current is drawn
when DC bias is first applied
Characterization •Stimulate the DUT with a time varying voltage Performance PS
using Waveforms to test under dynamic test conditions
•Speed matters
Parametric •Characterize performance of transistors, Precision Source Measure Unit
Testing of Devices diodes, resistors and capacitors Device/Parameter Analyzer
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5. Power Supply Output Characteristics
• Ripple and Noise
• Ideal output is free from any voltage variations; In practice, never the case
• Ripple = periodic variations, usually line related
• Noise = random variations
• Typically specified as either Vrms or Vp-p
• Vp-p shows the maximum variation away from the DC set point
• Programming Accuracy
• Measure of how closely the output will be to the setpoint
• Specified as a percent of output plus an offset
• Can determine if the power supply has the precision required
• Many power supplies have built-in voltmeters and ammeters to measure output
• Output Response
• When the set point or the load changes, it takes time for the output to change
• Slew rate is a result of the power supplies regulation and output bandwidth
• Typically specified for a voltage change from 10% to 90% of its rated output
• Also specified for a load change of 50% to 100%
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6. DC Power Supply Topologies
Linear or series-pass • Applications
• Bench & laboratory
• Automated test
• Low power: < 500 W
• Advantages
• Low output ripple & noise
• Fast programming speed Note: Agilent's linear Power
• Fast transient recovery Supplies classically have fast
• Disadvantages programming speed which
• Low efficiency make them a good fit in test
• High weight/watt systems.
• Physically large
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7. DC Power Supply Topologies
Switched mode (SMPS) • Applications
• Subassembly test
• Burn-in
• Bench & laboratory
• Electromechanical test
• Advantages
• High power in small package
**Note: Agilent's newest
• High efficiency
Switching Power Supplies
• Disadvantages have noise, slew rate,
• Moderate to high** ripple &
noise programming speed and
• Moderate programming speed transient performance nearly
• Moderate transient recovery that of linear supplies
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8. Key Power Supply Specs: Comparing Noise
Hint
High Noise
Noise is very dependent on
Typical PC Power Supply output voltage,
(not an instrument) so a 5V output will have much
100 mVpp less noise than a 100 V output
Typical
Switching
Agilent
(SMPS) Supply
Switching
20 mVpp Supply
Typical 10 mVpp Agilent Low Noise
Linear Supply Switching Supply
1 mVpp
Agilent
Linear Supply
Low Noise
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9. Controlling the Power Supply
• Computer Interfaces
• Many DC power supplies have both manual and computer control
• Hardware interfaces can include GPIB, USB, and LAN
• Analog Voltage Control Signal
• Some power supplies provide an analog voltage control input
• The power supply acts as an amplifier, providing current up to its
rated maximum
• Use the Analog Control input to:
• Amplify the power of the input signal
• Track an analog voltage
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10. Output Measurements
• Many power supplies have a built-in voltmeter and ammeter
to read back its own output
• The measurements can be displayed on the front panel or
queried by a computer connected to the interface
• These measurements are particularly useful in computer
controlled systems
• Measurement (or read back) accuracy is specified as a percent
of full scale plus an offset
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11. Remote Sense
(150 mV drop)
Lead resistance can
contribute a significant
voltage drop between the
I =10 Amps
output of the supply and the
actual voltage presented at
the load
(150 mV drop)
5.3 V
The sense leads measure the
voltage present at the load
itself, and adjusts the output High Z
I =Zero
of the supply to compensate Input
for the voltage drops in the
leads
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12. Remote Sensing Best Practice:
Minimize Wiring Path Impedance
• Four steps to minimize path impedance:
• Use larger gauge, twisted pair wire.
• Reduce distance between power supply and DUT.
• Minimize the use of relays / connectors.
• Select relays / connectors to minimize contact resistance;
consider initial and end of life specs.
• Beware of transient response issues for dynamic loads
• Use an adequate bypass capacitor at the DUT
• Consider a supply tailored for remote sensing with pulsed loads
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13. Physical Characteristics
• Physical size / Form Factor
• Half rack width or full rack width, some vendors offer ¼ rack width
• Height ranges from 1U to 4U (1.75 in to 7.00 in).
• Half rack width is generally better for bench applications
• Full rack width works well in system racks
• Front or Rear Output Terminals
• System and high current power supplies have their outputs located on the
rear panel
• Bench and some low current power supplies have their outputs on the front
• Number of Outputs
• Multiple output power supplies can save space on the bench or in a rack
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14. DC Power Supply Capabilities
• Constant voltage (CV) mode VSet CV
• Output sensing
I
• Constant current (CC) mode
V
CC
ISet
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15. Output Characteristics
• Rectangular • Dual-range
Pmax
Vmax Pmax
Vmax
Pmax
Imax Imax
Vmax
• Autoranging Maximum
power range
Imax
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16. Special Capabilities
• Protecting the Device Under Test
• Over Voltage Protection (OVP)
• Over Current Protection (OVP)
• Discrete Fault Indicator (DFI) / Remote
Inhibit (RI)
• Protecting the Power Supply
• Over Temperature Protection (OTP)
• Output Disconnect Relay
• Output Polarity Reversal
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17. Output protection features
Inhibit (INH) / FAULT (FLT)
Daisy-Chain of Three Power Supplies for Emergency Shutdown
Power Supply A Power Supply B Power Supply C
+S +S +S
+ + +
Load Load Load
- - -
A -S B -S C -S
1 1 1
FLT FLT FLT
2 2 2
3 3 3
INH INH INH
4 4 4
• For multiple bias input subassemblies, if one bias supply senses a failure,
all should be shut down
• TTL Input/Output
• Fault definition defined by system controller at set-up
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18. Unique Feature: Down Programming
• Capacitors discharge slowly under
light loads
-Static voltage source: no
problem
-Varying voltage levels: slow tests
• Down programming
-Rapidly decrease the output
voltage
-Reducing discharge times by
hundreds of ms
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19. Unique Feature: Sequencing
• Precise synchronization of bias voltage turn on and off
• Improper turn-on or -off may cause damage to DUT
• Modular power supplies often have built-in sequencing
capabilities
• Example applications
• LCD testing
• PC motherboard
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20. Output Sequencing Using the Agilent N6700-series
OUTPUT ON V1
V2
Module 1
V3
Module 2
Delay
2
Module 3 V4
Delay
3
Module 4
Delay
4
• Can control output sequencing between modules with 1 ms resolution
• Can control slew rate from 1 ms to 10 seconds for 0 to max V transition
• Useful for powering up devices, PC boards, or subassemblies that require control of
multiple bias supplies during startup
• Can also set the output off sequence independently
• Extendable across mainframes for > 4 outputs
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21. Unique Feature: Arbitrary Waveforms/List Mode
• Advanced feature available in N6700 and 66000 only*
• LIST mode allows power supply to output a waveform like an Arbitrary
Waveform Generator (ARB)
• Slower than an ARB, but MUCH more power than an ARB
• For each point, you program a V, I, and step time
• LIST mode can change the output faster than a PC can send commands
• Example: LIST mode rapidly steps through test conditions
for fast throughput
V
t
* Also available in specialized products: AC Source, DC Loads
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22. Example of High Speed Margin Test
Automotive Engine Control Unit
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23. TIP #1: Eliminating Sources of Noise
• Start with a low noise power supply
• it’s easier to eliminate noise at the source than to filter it out later
• Use good connection practice to avoid pickup:
• eliminate loops; twist and shield connections from power supply to
DUT
• carefully route power lines from ac mains to supply
• think through grounding connections; prefer a single point ground
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24. TIP #2: More Power
• Connect Power
Supplies in series
for higher voltages
• Connect Power
Supplies in parallel
for higher currents
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25. TIP #3: Use the right productivity tools
• Some power supplies are specialized per specific application
• Some power supplies contain special features to make your
job easier
• Examples
• Battery drain software
• Solar array simulator I-V curves
• Built-in V vs. time, I vs. time views
• Data logging
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26. The N6705B DC Power Analyzer
Boosts the productivity of the R&D Engineer
Integrates multiple instrument functions into a single box
• 1 to 4 advanced power supplies
• Digital voltmeter and ammeter
• Arbitrary waveform generator
• Oscilloscope
• Datalogger
• All functions and measurements
are available from the front panel
Gain insights into your DUT's power consumption
— in minutes, not hours —
without writing a single line of code!
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27. Summary
• Categories of Power Supplies
• How People Use Power Supplies
• Selecting the Right Power Supply
• Output Characteristics (Ripple, Noise, Speed, Accuracy)
• Control via Computer and/or Analog Inputs
• Output Measurement/Monitoring Capabilities
• Packaging (Size, Number of Outputs, Front/Rear Terminals)
• Special Capabilities (DUT protection, Output Disconnect/Reversal)
• Unique Features
• Tricks of the Trade
For More Information on Agilent Power Supplies, see:
www.agilent.com/find/power
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