blending radio and power management technologies for greatly … · 2018. 12. 5. · earl mccune...
TRANSCRIPT
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Blending Radio and Power Management Technologies for Greatly Improved Performance
-or-Why is an RF guy doing Power Management?!
Earl McCune, Ph.D., F-IEEEThursday, Aug. 23, 2018
Texas InstrumentsBuilding E Conference Center
2900 Semiconductor Blvd.Santa Clara, CA 95051
6:30pm - 7:00pm: Dinner and Networking7:00pm - 8:00pm: Talk and Q & A
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Earl McCune [email protected]
Outline
• State of the art in switch-based radio transmitters• Common physics with switching power converters
• Zero-Power Idle (ZPI) supply• Very-high Dimming Ratio (VHDR) efficient driver• Bridge rectifier elimination• Power factor correction
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Earl McCune [email protected]
Linear PA Efficiency Ceilings
• Entire output signal – peak to peak – must fit within the linear PA load line
• PA is scaled for signal peakpower
• Signal average power sets communication range
• Low average power increases PA heat– A direct consequence of
Ohm’s Law
3
0
0.005
0.01
0.015
0.02
0.025
0.03
0 0.5 1 1.5 2 2.5 3 3.5
I C(A
)
VCE (V)GaAs HBT
Envelope PDF
Signal envelope
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Earl McCune [email protected]
Linear PA Efficiency: Business Impact
• Signal design progression forces linear PA efficiency to decrease• Costs therefore rise
– Higher input power is required (larger power supply)– Thermal management of the corresponding PA heat
• Preferred radio efficiency range by industry: between 40 to 70 %• 5G must be profitable to build and operate – or it will fail
5G-NR
2G
LTE3G2.5G
0
1
2
3
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10
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Pow
er /
Out
put p
ower
(Nor
mal
ized)
Circuit Energy Efficiency
Input Power
Power Dissipation
Power supply size
TX powerHeatsink
size
5G-NR
2G
LTE
3G2.5GCOST
4
Efficiency vs. PAPR Cost vs. Efficiency
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Earl McCune [email protected]
Physically Available Options
Actual transmitter objective: modulation accuracy at-power• Traditional approach: Linear Theory
– Modulate at small signal levels– Increase signal power with linear amplifiers– Maintains modulation accuracy,
• as long as all amplifiers remain linear (mathematical sense)
• Alternative approach: Sampling Theory– Sample the envelope with phase-modulated carrier
5
VDD
Large VIN
RL
PSAT
VDD
Large VIN
RL
PSAT
RON
out D LV I R= ⋅
SUPPLYout L
L ON
VV RR R
= ⋅+
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Earl McCune [email protected]
Implementation Differences
Linear Operation• Output range is bounded
by the knee voltage• Signal always stays on the
load line
Switching Operation• Output range is bounded
by the ON resistance• Circuitry operates at the
endpoints of the load line• Efficiency increases
6
0 0.5 1 1.5 2 2.5 3 3.50
0.2
0.4
0.6
0.8
1
VDS (V)
Dra
in C
urre
nt (A
)
0
0.005
0.01
0.015
0.02
0.025
0.03
0 0.5 1 1.5 2 2.5 3 3.5
I C(A
)
VCE (V)
ON state
OFF state
VDD
Large VIN
RL
PSAT
VDD
Large VIN
RL
PSAT
RON
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Earl McCune [email protected]
Sampling Transmitter Operation
• Phase modulated carrier samples the signal envelope
• Dynamic Power Supply (DPS) sets the instantaneous envelope value
• Switch-mode mixer modulator (SM3) does the sampling at-power
• Switching forces use of polar signal processing
7
( )( )( ) cosA t t tω φ+
)(tA
SM3
DPS
VSUPPLY
Envelope
Phase Modulated RF
( )( )cos t tω φ+
0 0.5 1 1.5 2 2.5 3 3.50
0.2
0.4
0.6
0.8
1
VDS (V)
Dra
in C
urre
nt (A
)
Dynamic Power Supply
out SUPPLYLOAD
L L ON
V VIR R R
= =+
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Earl McCune [email protected]
-55 -45-35 -25
-15 -55 15
-70-60-50-40-30-20-100102030
0.01.0
2.03.0
4.05.0
Input RF Power (dBm)
PA O
utpu
t Pow
er (
dBm
)
PA Supply Voltage (V)
P-mode
Booth Surface
Operating Modes: L-mode, C-mode, and P-mode
• All power transistors are 3-port circuits• 3 operating modes appear when both supply voltage (dynamic power supply
(DPS)) and input RF power are varied– L-mode: conventional linear “PA” operation– C-mode: fully compressed operation– P-mode: low voltage “gain-collapse” region
VDPS , IDPS
DPS
VSUPPLY
Control
VS , IS
PAPOUTPIN
PDC = VPA * IPA
PD
New Interface
PD
}
RF Power Transistor To heatsink
to heatsink
8
Eridan operates in C-P mode
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Earl McCune [email protected]
Measured Efficiency vs. Signal PAPR
• Use of switching circuitry greatly improves measured efficiency
• Modulation accuracy is maintained
• Modulation generality is not compromised
• Reported efficiency is fully linearized
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0%
10%
20%
30%
40%
50%
60%
70%
0 2 4 6 8 10 12 14
Stac
k Ef
ficie
ncy
Signal PAPR (dB)
5G NR
LTE DL
LTE UL
3G
QAMs
EDGE
GSM-CE
16384 QAM LTE Downlink 5G-NR
-51dB ACLR
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Earl McCune [email protected]
Backup: Switching PA Efficiency Bounds
• Maximum efficiency depends on RL/RON• Transistors need to have fT > 50fo to operate well as a switching PA• Efficiency drops rapidly when fT < 10fo
– Dissipation during transitions becomes much more significant
10
100
101
102
103
0
20
40
60
80
100
fT / fo
Ach
ieva
ble
Effi
cien
cy (%
)
RL/RON=10
RL/RON=30RL/RON=100
90.5 91.0 91.590.0 92.0
0
1
2
3
4
-1
5
time, nsec
90.5 91.0 91.590.0 92.0
0
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-1
5
time, nsec
90.5 91.0 91.590.0 92.0
0
1
2
3
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5
-1
6
time, nsec9
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Earl McCune [email protected]
Technology Similarities
• SM RF Power
• Boost DC-DC
VERY important to carefully manage the switching duty cycle of the RF drive!
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Earl McCune [email protected]
Switching Supplies
• Switching supplies are not voltage sources
• Energy is stored in both L and C
• Matching inductor current to load current requires a feedback controller– Loop dynamics constraint appears– Mis-match errors are all handled by the storage capacitor C
12
212C OUT
E C V= ⋅2
21 12 2
OUTL L
LD
VE L I LR
= ⋅ = ⋅
RLD
SMPS control
Inductor currentLoad current
CL
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Earl McCune [email protected]
Switching Supply: Output Agility
If the switching time gets very short, changing energy in the digital supply requires kilowatts of transient power
Supply agility is therefore much slower than logic operating speeds
( )2 22 1212L C O OLDLE E E C V V
R
∆ = ∆ + ∆ = + −
( )2 12 ,O O OLD
L C V avg V VR
= + ∆ ⋅
Fast switching voltage (within TSTEP):
( )2 12
,O O OSTEP LD STEP
V avg V VE L CT R T
∆ ⋅ ∆= +
Goes to infinity as the step time goes to zero (PROBLEM)
Greater the higher the output voltage is (PROBLEM)
Change from VO1 → VO2
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Earl McCune [email protected]
Power Management Topic
• CPU power recovery (MicroNap / MicroWake) • LED drivers: Special capabilities• Direct (bridgeless) downconverting AC-DC + PFC• Duty cycle frequency multiplier (digital)
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Earl McCune [email protected]
Solution: Hold the Energy for Later
• Connect the load (or not) on command
• Example: 40 us OFF intervals– Load current is 17A for this measurement– 10 ns edge transition time on the device
power supply• Spacing between and width of these OFF
intervals is completely arbitrary
ONOFF ONOFF OFF
Dynamic Power Supply Voltage waveform
50 microseconds per division
DC input
L
C
Synchronous rectifier
Capacitor storage switch
Inductor storage switch
DC output
Keep C large for good regulation
Why we care:
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Earl McCune [email protected]
Configurations
• Storing inductor current and electric charge within a DC-DC converter
• Linear regulators can also take advantage of this output filter (storage) switching
Normal Operation
Hold energy while OFF
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Earl McCune [email protected]
Power Proportional Computing
• Input power is saved whenever the output is not powered– Input current falls as the output
duty cycle is reduced, maintaining DC-DC conversion efficiency
– ON time for this test is 200 microseconds
• This regulator has an observed input bias current of 12 mA
• Linear tracking is very good with duty cycle
Server regionPersonal, Embedded region
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Earl McCune [email protected]
ACPI States
• Nearly immediate transition between power states: no “friction”
• Controlled by job scheduler• Optimum when applied to each core
individually• Spacing between and width of these OFF
intervals is completely arbitrary
ACPI: C0
10 nanoseconds per transition
ACPI: C2 / C3
ACPI: C0
Scheduler
Responses
messages Assignments
Server cluster
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Earl McCune [email protected]
Low Processing-Demand Case
• Energy is maintained within the power supply while the output is OFF• Turn-on edge here remains at 10 ns even after 2 milliseconds of OFF time
– Output (20 us) pulse remains the same even when the OFF time exceeds 1 second (0.002% duty cycle)
• No loss of processing throughput performance
Switch and Capacitor technology combine to set available ZPI hold time
ONOFF ONOFFONOFFON
Wide time view Zoom-in view
OFFControl Command
Controlled Power Supply
1 A
DC input
L
C
Inductor storage switch
DC output
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Earl McCune [email protected]
Proving the ZPI Concept
• Modified existing DC-DC converter evaluation board– Additional control to the regulator– Switches to manage internal energy storage
• Applies more easily to linear regulators
• Nanosecond stop and start of amperes to the load is achieved– No overshoot on any transient
• Brings RF transmitter technology to power supplies for Computing
• US patents issued
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Earl McCune [email protected]
Power Management Topic
• CPU power recovery (MicroNap / MicroWake) • LED drivers: Special capabilities• Direct (bridgeless) downconverting AC-DC + PFC• Duty cycle frequency multiplier (digital)
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Earl McCune [email protected]
LED Dimming Method OptionsOptions for dimming already in production include• Shunt-switch pulsewidth modulation SS-PWM• Pulsewidth modulation PWM• Linear Current Regulation IREG• Series Resistor (sense) RSNSAnd now a new method is added• Variable-resistance Var_R
DC-DC converter
Error amplifier Digital
dimming control
Dimming command
DC-DC feedback
adjust
VREF (
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Earl McCune [email protected]
Comparison of Dimming Dynamic Range
• Direct voltage or current control has limited dynamic range• Resistor dynamic range covers more than 10,000,000 : 1
– Hold voltage constant, vary resistance, and current must track [via Ohm’s Law]
– LED dark current limits the actual useful range
0%
10%
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60%
70%
80%
90%
100%
0 0.2 0.4 0.6 0.8 1
Dim
min
g Co
ntro
l Effi
cien
cy
Brightness (normalized)
Var-R
R_SNS
PWM
I_reg
SS_PWM
Control Efficiency
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0.00001 0.0001 0.001 0.01 0.1 1
Dim
min
g Co
ntro
l Effi
cien
cy
Brightness (normalized)
Var-R
R_SNS
PWM
I_reg
SS_PWM
Dimming Dynamic Range
1/30,000
>98%
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Earl McCune [email protected]
Control Efficiency and Flicker Performance
• LED current is tightly regulated in all cases, across 30,000 : 1 range
• Actual dimming control efficiency is largely above 99%– And improves at higher brightness
0 10 20 30 40 50 6098.0%
98.5%
99.0%
99.5%
100.0%
Dimmer Control Setting
Dim
min
g Co
ntro
l Effi
cien
cy
HB white demonstrator
B&Y demonstrator
HB red demonstrator
ILED = constant
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Earl McCune [email protected]
Power Management Topic
• CPU power recovery (MicroNap / MicroWake) • LED drivers: Special capabilities• Direct (bridgeless) downconverting AC-DC + PFC• Duty cycle frequency multiplier (digital)
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Earl McCune [email protected]
New AC-DC Solution
Direct PFC
“Direct PFC” is a much simpler approach• Diode bridge is eliminated• Power factor correction (PFC)
happens using buck converter action
• Low output voltage greatly simplifies any following DC-DC conversion
• Operate at high frequency (1-10 MHz) for small size
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Earl McCune [email protected]
Bridgeless AC-DC: Step 1
• The electric utility is not a differential signal• Combine two DCDC designs
– Unipolar DCDC: +V in to +V out– Inverting DCDC: -V in to +V out
• Operate these separate configurations on opposite signs of the input AC power
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Earl McCune [email protected]
Bridgeless AC-DC: Step 2
• Combine these structures to use the same inductor• Operate these switches at HF - VHF to greatly shrink the inductor size• 4 FET switches perform rectification, PFC, and voltage downconversion
– Diode bridge is eliminated– High voltage is eliminated
• Line load is resistive even in the presence of phase-cut dimming• EMI filtering is greatly reduced
D = duty cycle of DCDC
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Earl McCune [email protected]
Power Factor Correction
• Switching duty cycle sets the voltage transfer ratio
• Switching frequency varies the effective input impedance
0.0
0.1
1.0
10.0
100.0
1,000.0
10,000.0
10000 100000 1000000 10000000 100000000
Switching Frequency (Hz)
Effective Resistance (ohms)Input Current (A)Input Power (W)
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Earl McCune [email protected]
Summary
• We all share the same physics!• RF power switch technology does apply to power management• Recent progress
– ZPI supply, switching 10’s of amperes in 10 nanoseconds or less• No dynamic controller settling transient• Prefers large output capacitance, excellent regulation
– >30,000:1 no-flicker dimming• 98%+ control efficiency• Adaptive to LED color
– No-bridge switching rectifier for AC-DC applications• Lower loss, easier EMI filtering• Adapting frequency provides PFC
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Earl McCune [email protected]
Abstract
Switching amperes of current in fractions of a nanosecond is regular practice in modern switch-based radio transmitter design. Switching power supplies presently achieve efficiencies that radio transmitter designers cannot even imagine. Mixing these technology bases leads to some interesting new potential product features, including nanosecond speed DC-DC output transitions without overshoot for 10’s of amperes, LED drivers with no flicker, dimming control exceeding 30,000:1 and 98% control efficiency, and elimination of bridge rectifier losses for AC-DC converters to name a few. This talk explores this combined technological territory.This talk will cover the following topics:• State of the art in switch-based radio transmitters• Common physics among switch-based radios and switching power
converters• Preliminary theory and results from measurements on combined
technology experiments• http://ewh.ieee.org/r6/scv/pels/
http://ewh.ieee.org/r6/scv/pels/
Blending Radio and Power Management Technologies for Greatly Improved Performance�-or-�Why is an RF guy doing Power Management?!OutlineLinear PA Efficiency CeilingsLinear PA Efficiency: Business ImpactPhysically Available OptionsImplementation DifferencesSampling Transmitter OperationOperating Modes: L-mode, C-mode, and P-modeMeasured Efficiency vs. Signal PAPRBackup: Switching PA Efficiency BoundsTechnology SimilaritiesSwitching SuppliesSwitching Supply: Output AgilityPower Management TopicSolution: Hold the Energy for LaterConfigurationsPower Proportional ComputingACPI StatesLow Processing-Demand CaseProving the ZPI ConceptPower Management TopicLED Dimming Method OptionsComparison of Dimming Dynamic RangeControl Efficiency and Flicker PerformancePower Management TopicNew AC-DC SolutionBridgeless AC-DC: Step 1Bridgeless AC-DC: Step 2Power Factor CorrectionSummaryAbstract