Blending Radio and Power Management Technologies for Greatly … · 2018. 12. 5. · Earl McCune [email protected] Outline • State of the art in switch-based radio transmitters

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

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


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


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

4

5

6

7

8

9

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


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

= ⋅+


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


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

= =+


-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


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

9

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


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

1

2

3

4

-1

5

time, nsec

90.5 91.0 91.590.0 92.0

0

1

2

3

4

5

-1

6

time, nsec9


Technology Similarities

• SM RF Power

• Boost DC-DC

VERY important to carefully manage the switching duty cycle of the RF drive!


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


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


Power Management Topic

• CPU power recovery (MicroNap / MicroWake) • LED drivers: Special capabilities• Direct (bridgeless) downconverting AC-DC + PFC• Duty cycle frequency multiplier (digital)


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:


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


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


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


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


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


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 (


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%

20%

30%

40%

50%

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%


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


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


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


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


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)


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


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

Documents

Blending Radio and Power Management Technologies for Greatly … · 2018. 12. 5. · Earl McCune [email protected] Outline • State of the art in switch-based radio transmitters