GaN FET-Based High CCM Totem-Pole Bridgeless PFC

Zhong Ye

Alvaro Aguilar Yitzhak Bolurian Brian Daugherty

Agenda

6-2

•  AC/DC efficiency standard and PFC efficiency requirement

•  Bridgeless PFC topologies and development trend

•  GaN ( Gallium Nitride) FET overview

•  Totem-pole CCM bridgeless PFC control -  UCD3138 control implementation -  Ideal diode emulation -  AC crossover detection and control

•  GaN device test in FET mode and diode mode

•  Totem-pole CCM bridgeless PFC test

•  Summary

Texas Instruments – 2014/15 Power Supply Design Seminar

AC/DC Efficiency Level Certifications

6-3 Texas Instruments – 2014/15 Power Supply Design Seminar

80 Plus Test Type

115 V Internal Non-Redundant

230 V Internal Redundant

Fraction of rated load

10% 20% 50% 100% 10% 20% 50% 100%

80 Plus 80% 80% 80% 80 Plus Bronze 82% 85% 82% 81% 85% 81% 80 Plus Silver 85% 88% 85% 85% 89% 85% 80 Plus Gold 87% 90% 87% 88% 92% 88% 80 Plus Platinum 90% 92% 89% 90% 94% 91% 80 Plus Titanium 90% 92% 94% 90% 90% 94% 96% 91%

Energy Star Specification

PFC Efficiency Budget

Texas Instruments – 2014/15 Power Supply Design Seminar 6-4

•  PFC design becomes more challenging at Platinum level efficiency and much harder at Titanium level efficiency

•  Well designed single-phase PFC and interleaved PFC achieve around 97.5% efficiency and are just able to meet Platinum efficiency requirement

•  Bridgeless seems to be the only way to reach Titanium efficiency level

80 Plus Test Type

Efficiency at 115 V Internal Non-Redundant

Efficiency at 230 95.5%V Internal Redundant

Fraction of rated load 10% 20% 50% 100% 10% 20% 50% 100%

80 Plus Platinum

PFC 95.8% 95.4% 93.7% 95.7% 97.4% 95.8%

DC/DC 94% 96.5% 95% 94% 96.5% 95%

80 Plus Titanium

PFC 95.5% 95.8% 96.4% 93.8% 95.8% 98% 98.5% 94.8%

DC/DC 94% 96% 97.5% 96% 94% 96% 97.5% 96%

6-5

Existing Bridgeless PFC Application Status Basic Bridgeless PFC + Good efficiency

+ Easy control

- High component count

- Low component utilization

- Low density

Totem-Pole Bridgeless PFC + Good efficiency

+ Fixed frequency

+ Easy control

- DCM only

- For power < 300 W

Texas Instruments – 2014/15 Power Supply Design Seminar

D1

Q1

D2

Q2

D5

D5

D3

D4

+

-

COC1

C2 C3 C4

L2

Lb1

Lb2

Lb

Q1

Q2

D1

D2

D3

D4

+

-

COC1

C2 C3 C4

L2

Line

Line/

Neutral

Earth

Line

Line/

Neutral

Earth

6-6

New PFC Development Trends

Texas Instruments – 2014/15 Power Supply Design Seminar

Transition-Mode Totem-Pole PFC •  ZVS operation •  Interleaved configuration for high power application (around max 300 W per phase) •  Variable frequency control •  Phase shedding and adding to optimize light load efficiency •  Suitable for MOSFET applications Continuous-Conduction-Mode Totem-Pole PFC •  Low component count •  Fixed switching frequency, zero reverse recovery switch should be used •  GaN is a good candidate for the application •  Possible to operate TM and ZVS at light loads

GaN Versus Silicon and SiC Eg: Wide band-gap energy EBR: Critical field break down voltage VS: Saturation velocity µ: Electron mobility

6-7 Texas Instruments – 2014/15 Power Supply Design Seminar

Properties GaN Si SiC EG(eV) 3.4 1.12 3.2 EBR(MV/cm) 3.3 0.3 3.5 VS(x 107cm/s) 2.5 1.0 2.0 µ(cm2Vs) 990-2000 1500 650

Theoretical on-resistance vs blocking voltage

101

100

10-1

10-2

10-3

10-4

101 102 103 104

RO

N �ȍ

PP

2)

Breakdown Voltage (V)

6L�/LPLW

6L&�/LPLW

*D1�/LPLWReference: EPC, Gallium Nitride (GaN) technology overview

rONα1

µ × EBR3

Key electrical properties of three semiconductor materials

100

10

1

0.1

0.01

7000

6000

5000

4000

3000

2000

1000

0

0 400 800 1200 1600 2000 2400

0 50 100 150 200

Ke

y F

igu

re

of

Me

rit

(R

ON

x Q

G�>ȍ

�Q&@

VDSS�>9@

6ZLWFKLQJ�)LJXUH�RI�0HULW�±�6L�YV��6L&�YV��*D1

}

}

1200 V GaN cascode

performance range

600/650 V GaN cascode

performance range

LV GaN FET

(Enhancement)

RF GaN FET

(Depletion)

Si FETs

GaN 66 V/µmGaN 66 V/µmSilicon transistors

6LOLFRQ *D1

6L&Cree

Infineon

ST

International Rectifier

Toshiba

6L&�&DVFRGHAOS/SemiSouth

EPC-CO

International Rectifier

Micro GaN

GaN Systems 2012 rON x QG�>ȍ x S&@R

ON

x &

OS

S�>P

ȍ x

S)@

Power Electronics Technology Feb. 2013

Figure of Merit Comparison

Figure of Merit depicts fundamental characteristics of switching devices – Rds_on, Qg, COSS and breakdown voltage

6-8 Texas Instruments – 2014/15 Power Supply Design Seminar

6-9

Cascode GaN FET Structure

Texas Instruments – 2014/15 Power Supply Design Seminar

Cascode GaN FET internal structure Example of a boost configuration

Advantages: •  Depletion-mode GaN: low cost and

better performance (compared to enhancement-mode GaN)

•  Same MOSFET driver used •  Low forward voltage drop in diode mode

Disadvantages: •  Same reverse recovery of the

cascode MOSFET body diode •  Potential MOSFET avalanche at high Vds slew rate •  Large gate charge (same as the MOSFET)

Normally-onHV GaNHEMT

Normally-offLV NMOS SS

G

D

SSS

G

D

G

S

SCN

+

–

+

–

VO

CO

Q1

Q2

L

iL

Vin

PWM

Dmode-GaN + Safety FET Structure

6-10 Texas Instruments – 2014/15 Power Supply Design Seminar

PWM

D

GND

VCC

S

Normally onHV GaN

StartupMOSFET

GateDriver

StartupLogic

Advantages: •  Zero reverse recovery •  Low gate charge •  No LV MOSFET switching loss •  Suitable for high switching frequency applications •  Integrated gate driver circuit to ease applications

Disadvantages: •  High forward voltage drop in

diode mode •  Complicated gate driver circuit (IC design)

+

–

VO

CO

Q1

Q2

Q3

Q4

PWM

GND

VCC D

S

PWM

GND

ZCD

VCC D

S

StartupLogic

StartupLogic

IsolatedPower

DigitalISO

HallSensor

AC1

AC2

Earth

Iac

12 V

Vg3

12 V12 V

Vg1

Vg2

Vg4

Driv

er

6-11

GaN-Based CCM Totem-Pole Bridgeless PFC Power Stage

Texas Instruments – 2014/15 Power Supply Design Seminar

Positive switching cycle §  Active switching stage

•  Q1 and Q2 are low frequency switches.

•  Q3 and Q4 are an active switch and a SyncFET.

Positive switching cycle – active switching stage  

6-12 Texas Instruments – 2014/15 Power Supply Design Seminar

GaN-Based CCM Totem-Pole Bridgeless PFC Power Stage

Positive switching cycle §  Active switching stage

+

–

VOCO

Q1

Q2

Q3

Q4

PWM

GND

VCC D

S

PWM

GND

VCC D

S

StartupLogic

StartupLogic

IsolatedPower

DigitalISO

HallSensor

AC1

AC2

Earth

Iac

12 V

Vg3

12 V12 V

Vg1

Vg2

Vg4

Driv

er

ZCD

+

–

VOCO

Q1

Q2

Q3

Q4

PWM

GND

VCC D

S

PWM

GND

ZCD

VCC D

S

StartupLogic

StartupLogic

IsolatedPower

DigitalISO

HallSensor

AC1

AC2

Earth

Iac

12 V

Vg3

12 V12 V

Vg1

Vg2

Vg4

Driv

er

6-13 Texas Instruments – 2014/15 Power Supply Design Seminar

Positive switching cycle – freewheel stage  

GaN-Based CCM Totem-Pole Bridgeless PFC Power Stage

Positive switching cycle §  Freewheeling stage

+

–

+

–

VO

CO

Q3

PWM1A

PWM1B

iL

Q4

PWM

GNDL

VCC

VCC

D

S

PWM

GND

D

S

Startup

Logic

Startup

Logic

100

80

60

40

20

0

-20

-40

-60

-80

-100

-3.0 -2.0 -1.0 0 1.0 2.0 3.0

VD

VGS

I D

0 V

-1 V

-1.5 V

-2 V

-2.5 V

-3.3 V

VDS of Q3

-iQ3iQ4 -iQ3iQ4

Vg of Q4

VDS of Q3

Vg of Q4 Vg of Q3

GaN FET Forward Voltage Drop and Ideal Diode Emulation Control

6-14 Texas Instruments – 2014/15 Power Supply Design Seminar

Output characteristics of a typical depletion mode GaN FET Ref: Transphorm datasheet

GaN FET operates at diode mode GaN FET operates at ideal diode mode

Adaptive Dead-Time Control for SyncFET to Turn On

6-15 Texas Instruments – 2014/15 Power Supply Design Seminar

Csub_d, Csd and Crss add to form Coss Current sampling point

td =2Coss × VO

IL_peak

Da Db Da Db Da DaDb

DbDa Da

ZCD

Hardware-Assisted IDE Control

6-16 Texas Instruments – 2014/15 Power Supply Design Seminar

•  Difficulty of volt-second control for ideal diode emulation

CCM Load increasing Stuck at CCM

Negative current detection and SyncFET soft off control is needed

•  Freewheel stage current sensing for zero current detection

Db is chopped off at ZCD point

DCM Load decreasing

UDC3138 Digital Controller

Q3 Q4Q2Q1

VO

Vref

Iref

AB

C

+

-+

-

IS

SyncFET

Programmable NCD Ref

Main FET

Comparator

Iac

AC1

AC2

Current Loop

Voltage Loop

Main FET and SyncFET

Selection

EADC + CLA + DPWM

GVKmABC

ZCD

1/Vrms2Vrms

Kf|x|ADC

ADC

Crossover

Detection

UCD3138 – Based Control Circuit

6-17 Texas Instruments – 2014/15 Power Supply Design Seminar

Test Results – GaN FET Performance in FET Mode

6-18 Texas Instruments – 2014/15 Power Supply Design Seminar

Test Conditions: •  Vin = 200 VDC, Iin = 2 ADC, VO = 400 V •  Q4: 600 V 150 mΩ depletion-mode GaN power transistor •  D3: Cree SiC diode C3D04060A •  Gate turn-off resistance = 2.2 Ω, turn-on resistance=15 Ω Test Results: •  Turn-on time = 9 nS •  Max turn-on dV/dt = 79 V/nS •  Coss is linearly charged up to VO at turn-off •  About 18 V ringing when freewheel diode conducts

+

–

VO

CO

Q3

Q4

SiC

D3

PWM

GND

VCCD

S

Startup

Logic

12 V

Vg4Vin

+

–

IL

6-19 Texas Instruments – 2014/15 Power Supply Design Seminar

Test Results – GaN FET Forward Voltage Drop in Diode Mode

Test Conditions: •  Current = 0.1 A – 3 A, dead-time = 100 nS Test Results: •  Forward voltage drop varies from 4.3 V to 7.3 V device-to-device when GaN is off

+

–

VO

CO

Q3

Q4

PWM

GND

VCCD

S

PWM

GND

VCCD

S

Startup

Logic

Startup

Logic

Isolated

Power

Digital

ISO

12 V

Vg3

12 V

Vg4

Vin

+

–

IL

GaN

Si: STTH8R06D

SiC

+

–

VO

CO

Q3

Q4

PWM

GND

VCC D

S

PWM

GND

VCC D

S

StartupLogic

StartupLogic

IsolatedPower

DigitalISO

12 V

Vg3

12 V

Vg4Vin

IL

+–

6-20 Texas Instruments – 2014/15 Power Supply Design Seminar

Test Results – GaN FET Reverse Recovery in Diode Mode

Test Conditions: •  Q3 uses GaN FET, C3D04060E and

STTH8R06D

•  di/dt is about 368 A/µS

Test Results and Conclusions: •  Both GaN FET and SiC diode just have ringing

current – no reverse current was observed

•  STTH8R06D has a significant reverse current

•  GaN FET has a larger ringing than SiC, but at lower frequency, as a result of larger output capacitance of the two GaN FETs

6-21 Texas Instruments – 2014/15 Power Supply Design Seminar

AC Current Crossover Control

115 Vac

230 Vac|Vac_L – Vac_N|

0

|Vac|

VT_H

VT_L

Vg_Q1 Vg_Q2

Vg_Q3 Vg_Q4

RectifierFETs

ActiveGaN FETs

Integrator Running Integrator RunningIntegrator Stall

Turn-on Delay

Soft Turning On

Negative Half Cycle Positive Half Cycle

6-22 Texas Instruments – 2014/15 Power Supply Design Seminar

Current Spike Root Causes and Solutions

Root Causes: •  Inaccurate a.c. voltage sensing •  Turning on rectifier FET too early

cause a.c. line short sircuit •  Current loop disturbed by current spike •  Rectifier FET hard switching •  Current loop compensation not

optimized

Solutions: •  Differential a.c. voltage sensing with low

phase offset •  Using different a.c. crossover voltage

thresholds for high line and low line •  Sufficient blanking time •  Disable PWM and stall integrator during

blanking time •  Rectifier FET soft switching on •  Inserting PWM turn-on delay time •  Optimize current loop compensation

6-23 Texas Instruments – 2014/15 Power Supply Design Seminar

AC Current Waveforms

115 Vac input at 450 W PF= 0.999 THD = 3.3%

230 Vac input at 750W PF= 0.995 THD = 4.0%

6-24 Texas Instruments – 2014/15 Power Supply Design Seminar

Totem-Pole Bridgeless PFC Efficiency

38 76 114

152

190

228

266

304

342

380

418

456

494

532

570

608

646

684

722

760

100.00%

98.00%

96.00%

94.00%

92.00%

90.00%

88.00%

86.00%

84.00%

82.00%

80.00%

98.5%

230 Vac 115 Vac

Partial ZVS at low line input and light loads

Po/W

6-25 Texas Instruments – 2014/15 Power Supply Design Seminar

750 W Totem-Pole Bridgeless PFC Prototype

6-26 Texas Instruments – 2014/15 Power Supply Design Seminar

Summary •  GaN FET exhibits superior switching characteristics •  Safety GaN FETs has zero reverse recovery

•  Suitable for high-frequency hard-switching applications

•  Relative high “body diode” forward drop •  Sophisticated ideal-diode-emulation is the key to the success of Safety

GaN FET applications

•  Enables Totem-Pole PFC CCM operation •  AC crossover current spike root causes were analyzed and solutions

provided

•  High efficiency potential

•  Possible TM ZVS control to optimize light loads efficiency

IMPORTANT NOTICE

Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and otherchanges to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latestissue. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current andcomplete. All semiconductor products (also referred to herein as “components”) are sold subject to TI’s terms and conditions of salesupplied at the time of order acknowledgment.TI warrants performance of its components to the specifications applicable at the time of sale, in accordance with the warranty in TI’s termsand conditions of sale of semiconductor products. Testing and other quality control techniques are used to the extent TI deems necessaryto support this warranty. Except where mandated by applicable law, testing of all parameters of each component is not necessarilyperformed.TI assumes no liability for applications assistance or the design of Buyers’ products. Buyers are responsible for their products andapplications using TI components. To minimize the risks associated with Buyers’ products and applications, Buyers should provideadequate design and operating safeguards.TI does not warrant or represent that any license, either express or implied, is granted under any patent right, copyright, mask work right, orother intellectual property right relating to any combination, machine, or process in which TI components or services are used. Informationpublished by TI regarding third-party products or services does not constitute a license to use such products or services or a warranty orendorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual property of thethird party, or a license from TI under the patents or other intellectual property of TI.Reproduction of significant portions of TI information in TI data books or data sheets is permissible only if reproduction is without alterationand is accompanied by all associated warranties, conditions, limitations, and notices. TI is not responsible or liable for such altereddocumentation. Information of third parties may be subject to additional restrictions.Resale of TI components or services with statements different from or beyond the parameters stated by TI for that component or servicevoids all express and any implied warranties for the associated TI component or service and is an unfair and deceptive business practice.TI is not responsible or liable for any such statements.Buyer acknowledges and agrees that it is solely responsible for compliance with all legal, regulatory and safety-related requirementsconcerning its products, and any use of TI components in its applications, notwithstanding any applications-related information or supportthat may be provided by TI. Buyer represents and agrees that it has all the necessary expertise to create and implement safeguards whichanticipate dangerous consequences of failures, monitor failures and their consequences, lessen the likelihood of failures that might causeharm and take appropriate remedial actions. Buyer will fully indemnify TI and its representatives against any damages arising out of the useof any TI components in safety-critical applications.In some cases, TI components may be promoted specifically to facilitate safety-related applications. With such components, TI’s goal is tohelp enable customers to design and create their own end-product solutions that meet applicable functional safety standards andrequirements. Nonetheless, such components are subject to these terms.No TI components are authorized for use in FDA Class III (or similar life-critical medical equipment) unless authorized officers of the partieshave executed a special agreement specifically governing such use.Only those TI components which TI has specifically designated as military grade or “enhanced plastic” are designed and intended for use inmilitary/aerospace applications or environments. Buyer acknowledges and agrees that any military or aerospace use of TI componentswhich have not been so designated is solely at the Buyer's risk, and that Buyer is solely responsible for compliance with all legal andregulatory requirements in connection with such use.TI has specifically designated certain components as meeting ISO/TS16949 requirements, mainly for automotive use. In any case of use ofnon-designated products, TI will not be responsible for any failure to meet ISO/TS16949.

Products ApplicationsAudio www.ti.com/audio Automotive and Transportation www.ti.com/automotiveAmplifiers amplifier.ti.com Communications and Telecom www.ti.com/communicationsData Converters dataconverter.ti.com Computers and Peripherals www.ti.com/computersDLP® Products www.dlp.com Consumer Electronics www.ti.com/consumer-appsDSP dsp.ti.com Energy and Lighting www.ti.com/energyClocks and Timers www.ti.com/clocks Industrial www.ti.com/industrialInterface interface.ti.com Medical www.ti.com/medicalLogic logic.ti.com Security www.ti.com/securityPower Mgmt power.ti.com Space, Avionics and Defense www.ti.com/space-avionics-defenseMicrocontrollers microcontroller.ti.com Video and Imaging www.ti.com/videoRFID www.ti-rfid.comOMAP Applications Processors www.ti.com/omap TI E2E Community e2e.ti.comWireless Connectivity www.ti.com/wirelessconnectivity

Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265Copyright © 2015, Texas Instruments Incorporated