power factor correction – why and how? drivers for power factor correction what is power factor...

Renesas Electronics America Inc.© 2012 Renesas Electronics America Inc. All rights reserved.

Power Factor Correction –Why and How?

© 2012 Renesas Electronics America Inc. All rights reserved.2

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32

-bit

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-bit


Enabling the Smart Society

IndustrialMotors

Smart Metering

Energy harvesting

Home Automation

Energy efficiency is key to a Smart Society

Power quality is key to efficient energy management


Agenda Market drivers for Power Factor Correction

What is Power Factor and why do we need to correct it?

Definition of Power Factor (PF)

What causes PF degradation

Impacts of bad PF on power distribution and billings

How do we correct bad Power Factor?

Basic PFC topologies

Renesas PFC Solutions

Analog and Digital Solutions

Implementation with Renesas MCU and Analog & Power devices

Summary


PFC Market Drivers


What Drives the PFC Market?

Some energy is delivered but not used due to bad PF

Consumers

Some consumers are charged for energy they don’t use

Power utilities

Need to cover consumers who are not charged for bad PF

Need to compensate by over-sizing:

– Distribution lines, Transformers, Energy production

Harmonics can disrupt other consumers

Government regulations


Real Power: P = 400 W (Watts)

Apparent Power: S = 120V x 5.1A = 612 VA (Volt Ampere)

Power Factor:

What is Power Factor?

~AA AP

AC Motor

WattmeterAmmeter

120V 60Hz

)()(

VASWPPF =

5.1 A 400W

PF = 400/612 = 0.653



Where did the power go?

AC currentAC voltage

φDisplacement

)()(

VASWPDPF = ϕcos=DPF

Range: 0 – 1

Q(VAR): Reactive Power

DPF = 1 when Q = 0

P (W)

Q (VAR)S (VA)

φ

S’

Inductive Load



Total Harmonic Distortion (THD) Non-linear loads distort original AC current

Total Power Factor Combination of Displacement Power Factor

(DPF) and Distortion Power Factor (THD)


φDisplacement

Distortion

1

39

3

2

I

ITHD

n∑=

I1: RMS value of AC current fundamentalIn: RMS value of AC current nth harmonic

211

THDDPFTPF

+=


What causes PF degradation?

Inductive loads store reactive power and cause current lag

Non-linear loads with switching elements distort the original AC current and introduce harmonics

Total Power Factor

Bad PF:

1<TPF

211

THDDPFTPF

+=


Question 1

What causes PF degradation?

A. Resistive loads

B. Inductive loads

C. Capacitive loads

D. Non-linear loads

E. B, C, D

F. None of the above


Why Power Factor < 1 is bad?

Reactive energy is not used to produce real power

Utilities need to compensate by over sizing: Distribution lines Transformers Energy production

Harmonic distortion can disrupt other consumers


Power Factor Correction


Power Factor Correction

PFC makes the load look like a resistor!

Need to control current to match the shape and phase of the

voltage


φDisplacement



Power Factor Correction Methodologies

Passive PFC Passive components to compensate for reactive energy loss

Active PFC Active components to drive solid state switches with PWM

signals in combination with passive reactive components such as inductors

+-


Passive PFC

Control harmonic current using filter

Expensive large high-current inductor

No automatic adjustment for wider AC input power

DC output varies with AC input voltage

Passive Power Factor Correction


Active PFC Input current is controlled to follow the shape and phase of

input AC voltage

Transistor Q is switched ON/OFF at a PWM rate

Most common configuration – Boost converter

Efficiency is affected by Q switching losses and diode recovery

Active Power Factor Correction

Q


Active PFC Topologies

Critical Conduction Mode (CRM)

Q switched on when inductor current reaches zero Inductor ripple current - High Low power applications No recovery loss through diode

Q

Rectified, unfilteredAC voltage

Average AC current

Inductor ripple current



Continuous Conduction Mode (CCM)

Q switched on before the inductor current reaches zero Inductor ripple current – Low High power applications Recovery loss through the diode


Average AC current

Inductor ripple current

Q


Implementation Example of Active CRM PFC

CMP+ (Zero current detection)

TMX00 (PFC output)

PFC-ON pulse width


PFC-off pulse width

Average AC current

CMP+

TMX

00

AN

I0

Interlock

Zero current detection

Internal Vref

T1

DC BUS

Critical Conduction Mode(CRM)

PFC Boost Converter

MCU

Timer A/D


Two channel interleaved

Single channel


D1

Q1~120V

AC

C PFC Cb

L1

D1

Q1~120V

AC

C PFC Cb

L1

D2

L2

Q2

Reduced current ripple

Q1

IL1

Q1

IL1

Q2

IL2

IL1+IL2


Effect of High-frequency Switching

Harmonics and inductor current ripple can disrupt other consumers Regulation standards apply – IEC61000-2-2

Higher ripple current will require better filters with multiple stages

Q

~120VAC

L

L

C C


Advantages of Interleaving

Reduced current ripple Size and number of input filters can be reduced

Size of inductors, capacitor, switching devices can be reduced

Overall efficiency is increased


Interleaved PFC Versus Single Channel

Single channel Inductor ripple current affects size of:

– Inductor, Bulk Capacitor and input EMI filter

High current through IGBT/MOSFET cause conduction losses

Two channel interleaved Two sets of smaller and less expensive components:

– Inductor, Diode, Capacitor and IGBT/MOSFET

180° out of phase switching

– Inductor ripple currents cancel out each other

– Further reduction in bulk capacitor size and EMI filter

Better efficiency due to reduced conduction losses

Multiple interleaving can further reduce the size of components


Interleaved PFC versus Single Channel

Item Single Channel 2-Ch InterleavedRipple current Large SmallInductor 1 large 2 small (less $)Transistor 1 large 2 small (less $)Diode 1 large (SiC?) 2 small (less $)Bulk capacitor Large SmallEMI filter Large SmallEfficiency Good Better

CCM topology for large power application (>300W)


Typical Application - Motor Control and PFC

MCU

90 – 264

VAC

Gate Driver

PWM

PWMCurrent, voltage, temperature,OC-detection

PWM

Fast Recovery Diode ( SiC)

L

C

PFC Control

IC

AC voltage,DC voltagecurrent

3 Phase Inverter stageD

T

3 Phase Motor

Speed,Position


Digital PFC for Motor Control Inverter

MCU

90 – 264

VAC

Gate Driver

PWM


PWM


L

C



T

3 Phase Motor

Speed,Position



Renesas offers a variety of analog and digital devices to support PFC

Analog: PFC Controller ICs Single channel and interleaved

CCM and CRM topologies

Internal MOSFET/IGBT driver

Digital: MCUs with integrated peripherals High performance CPU with FPU and 10ns flash access

Internal PGAs and Comparators

High-speed ADC with multiple S&H

Fast over-current protection by hardware

Fast interrupt response


Analog PFC Solutions


PFC Controllers– CCM (Continuous Conduction Mode)– CRM (Critical Conduction Mode)

PFC Boost Switch– Super Junction MOSFETs for high frequency (> 50 kHz), up to

2.5 kW– High Speed, Low Vceon, IGBTs for lower frequency (< 40 kHz)

and above 2.5 kW

PFC Boost Diode (SiC)

Support and Collateral Datasheet Evaluation Boards Technical Support

Renesas Offers Complete Analog PFC Solutions


Mode Part # Features Applications

CCM

Interleaved R2A20114R2A20104

Small current rippleAverage SW noiseMore complex circuit

ServerAir conditionerInduction heating

Single R2A20115 Large current rippleLarge SW noiseSimple circuit

Plasma TVPCOffice automation

CRM

Interleaved R2A20132R2A20118AR2A20117R2A20112

Small current rippleAverage SW noiseMore complex circuit

Air conditionerPlasma TVPCOffice automation

Single R2A20113 Large current rippleLarge SW noiseSimple circuit

LCD monitorAC adaptorLCD projector

Renesas Analog PFC Controller Solutions


Current transformers

CCM Interleaved PFC Controllers 2A20114/20104

Phase drop control input Internal / external clock can be used 20104 can use current transformer


CRM Interleaved PFC Controllers 2A20132

Phase drop control input OTC – prevents increase of switching frequency at light loads

— Increased efficiency at light loads Protection circuits: Brownout, ZCD pin opening


CCM Interleaved PFC Controllers

Protection featuresZCD open/shortOCP timer latchRAMP charge

currentBrownout

Soft start Gate drivability VFB 1.5%

R2A20118/117/112


Digital PFC Solutions


PFC Control Functions

PFC Controller

85 – 264VAC400V DC

Inductor ripple

currentGate PWM

OC/OV Detection

VREF

PFC Hardware

VACVDC

PF > 0.9


PFC Control Functions – Input/Output

Control function Input Output

Output voltage Feedback voltage Constant DC bus voltage

AC voltage range AC voltage Adjust to 85-264VAC

Inductor currentIGBT current

AC voltage

Inductor current amplitudeSynchronize with AC voltage phase

Hardware protectionOver-currentOver-voltage

Under-voltage

Disable IGBT gate signals


Digital PFC for Motor Control Inverter

Rx62T MCU

90 – 264

VAC

Gate Driver

PWM


PWM


L

C



T

3 Phase Motor

Speed,Position


Interleaved PFC Reference Design

PFCCH1

Rx62T MCU board

PFCCH2

Auxiliary power

DC/DC converter

SICDiodes

395V3.8Aoutput

85-264 VAC input


Complete PFC Solution from Renesas

RX62T/100pinR5F562TAADFP

IGBT:RJH60F4DPK

Diode:RJS6005TDPP-EJ(target)

IGBT:RJH60F4DPK


System Specification

1 MCU R5F562TAADFP (RX62T)(Flash: 256kB, RAM: 32kB, CLK: 100MHz, VCC: 5V )

2 Circuit system Continuous Conduction Mode / 2-phase interleaved3 Switching device IGBT (RJH60F4DPK: 600V/50A)4 Input voltage AC 85 to 264 V5 Output voltage DC 395 V6 Maximum output current 3.8 A7 Maximum output power 1.5 kW8 PWM frequency 35 kHz / 1 phase x 29 Efficiency > 96 %

10 Power factor > 0.96


PFC OUT390V

GateDriver

VAC

VoltageReference

INPUTAC85～264V

FB

GND

OUT1

+

×

-

CurrentController

VoltageController

PWMTimer1

OUT2 GateDriver

ADC12bit

OCPsetting

OVPSetting

ProtectionController

Multiplyer

CS1CS2

OSCController

CLK:100MHzCLK:50MHz

PWMTimer2

RX62T

ADC10bit

Deviation

DeviationDuty 1Duty 2

PFC Controller System Block Diagram

ProtectionSWHW


CS1 GD1

GD2

Controller Implementation

Control loops:Two-stage IIR filter

CC1

CC2

VC

CS2

VAC

VFB

CS1,2 - Current sensing Ch1,2VAC - AC Input voltageVFB - DC Output voltageCC1,2 - Current controller 1,2VC - Voltage controller


Program Flow

Conversion start by GPT

Conversion complete interrupt

Voltage reference calculation

Voltage IIR filter controller

Current IIR filter controller

GPT PWM duty update

ADC conversion interrupt

12-Bit ADC

ADC to voltage calculation

Voltage controller

Current controller

PWM update

Main

Main

Interrupt

10-Bit ADC

VAC CS FB


Signal name MCU Peripheral Pin Name I/O Resolution Functions

GD1 GPT0 GTIOC0A-A OUT 20ns PWM for IGBT1 gate

GD2 GPT1 GTIOC1A-A OUT 20ns PWM for IGBT1 gate

VFB 12-Bit ADC0 AN000 IN 12bit Output DC voltage sensing

CS2 12-Bit ADC0 AN001 IN 12bit IGBT1 current sensing

CS2 12-Bit ADC0 AN002 IN 12bit IGBT2 current sensing

VAC 10-Bit ADC AN2 IN 10bit Input AC voltage sensing

RX62T MCU Resources Used


CS1

CS2

IL1

GD2

FB

IL2

0.02Ω

0.02Ω

uPC844G2

uPC844G2

uPC844G2

RX62T Peripherals used for PFC

16-Bit CMT 4 channel

Multi purpose timer

Flash up to 256KB

Data Flash 8KB(30k times E/W)

RAM 16KB

RX CPU(100 MHz)

FPUMultiplier, Divider,

Multiply, Accumulate

Ch 3&43-ph PWM

Ch 1&22 Encoder Inputs

Ch 0Hall / BEMF Input

Ch 5Dead-time compensation

Ch 6&73-ph PWM

16-Bit MTU3

12bit ADC 4-ch

x 2

3 PGA3 Comp

x 2

10bit ADC 12-ch

16-bit PWM Timer GPT0




390VDC

~

CS1CS2

VFB

VAC

GPT

RX 62T

GD1

GD2


CS1

CS2

IL1

GD2

FB

IL2

0.02Ω

0.02Ω

uPC844G2

uPC844G2

uPC844G2

GD1

Timer count 1

Duty set 1

Average coil current 1

GD2

Timer count 2

Duty set 2

Average coil current 2

GD1 period

CS1 ADC sampling

Tn Tn+1 Tn+2

GD2 period

FB ADC sampling

Tn Tn+1 Tn+2

180deg phase shift

CS2 ADC sampling

IGBT current 2

Gate Drive, Synchronized ADC sampling

GD1

GD2

VFB

CS1

CS2


RX62T

POE0#

PWM-FB

MTIOC3BPFC-GD1

PFC-GD2

PWM-GD

MTIOC4A

MTIOC4B

3.33V

+5VPFC-OUT

2MΩ

18.56kΩ

5.1kΩ2kΩ

3.33V

PWM-OUT

20kΩ

PFC-FB

PWM-OUT

PFC-OUT

R5F562TAADFP

10k

OVP_PWM

OVP_PFC

* 1. Protection by external hardware* 2. Protection by internal hardware by POE function

* 1* 2

Overvoltage Protection by Hardware

- Example of PFC and DC/DC converter


AN000/AN101

AN001/AN101

AN002/AN102

ADC unit 0

Data Register 0

Data Register 1

Data Register 2

Data Register 3

S/H

Three S&H for sensing currents and voltage for interleaved PFC.

PGA (Programmable Gain Amp) with selectable gain

1 usec conversion time per channel at AVCC0=AVCC=4.0 to 5.5V.

AN003/AN103

Feedback Signal Measurement by 12-Bit ADC

PGA

PGA

PGA

S/H

S/H

Mul

tiple

xer

ADC

VFBPF_IN

VCSPF1_IN

VCSPF2_IN

VAC_IN


Implementation with General Purpose Timers

4-Channels, 16-Bit counters, 100 MHz count clock

Phase shifted operation – 180° for interleaved PFC

Triangular wave with center aligned PWM

ADC conversion start trigger by timer

GTIOC0A-A/B

POE3

CPU interrupt for POE

AD trigger

CPU InterruptGTCCRA0

GPT0.GTCNT

ONGTIOC0A-A ONOFFOFF

ON OFF ONONOFF

OFF

GPT1.GTCNT

1. GTPR0,1: PWM frequency（35kHz)2. GTCCRA0,1: PWM duty

GTIOC1A-A

GTCCRA1

GPT0GTIOC0B-A/B

GTIOC1A-A/BAD trigger

CPU InterruptGPT1

GTIOC1B-A/B

GTIOC2A-A/BAD trigger

CPU InterruptGPT2

GTIOC2B-A/B

GTIOC3AAD trigger

CPU InterruptGPT3

GTIOC3B

Out

put p

rote

ct


Example of PFC Control Trigger by GPT0

GTIOC0A output PFC gate drive

GTADTRAADC Trigger

ADC conversion start

ADC conversion end

PFC control start PFC control end

ADC conversion end interrupt

∆t

Register write Register write Register write Register write

aaaabbbbccccddddeeee

ffff

GPT0.GTCNTCounter value

bbbb ffff dddd

hhhhGTP0.GTPRPFC Cycle

hhhh

hhhhddddffffBuffer transfer at crest Buffer transfer at through Buffer transfer at crest

Time

GTP0.GTCCRCPFC Duty Cycle


CPU BW for Interleaved PFC: 32% @35KHz

GD1

PFC control timing 28us

9us (32%)Control loop processing:

4.5us 4.5us


Input AC voltage

Input AC current

Inductor current

Output voltage ripple

AC Current Waveforms @1.5KW – 100V AC input

1.5KW @ 100V AC Input


Each GPT channel can generate HR-PWM for two outputs independently Minimum resolution is 1/32 of normal resolution: 312.5psec @100MHz 390.0psec @80MHz

GTCNT

Comparator

GTCCRF

GTCCRB GTCCRA

Controller

GTDVU GTPR

GTCCRD

GTCCRE GTCCRC

GTPBR

Out

put

cont

rol

GTADTRAGTADTBRA

GTADTRB

Out

put p

rote

ct

ExternalTrigger.

PWM1

PWM2

POEx

AD trigger

CPU interrupts

CPU Interrupt

GTADTBRB

GTADTDBRA GTADTDBRB

GTPDBR

Inpu

t co

ntro

l

GTDBUGTDVDGTDBD

Com

para

tor

inpu

t

Hig

h re

solu

tion

rising falling

GTTCRA GTTCRA

GTDLYRA GTDLYFA

GTIOCA

GTTCRA

15 0Upper 16bit Lower 5bit

+GTDLYRA

+GTDLYFA

04

GTDLYFAGTDLYRA

Rx62G High Resolution PWM Timer


Question 2

What PFC method is used in the Renesas digital reference design?

A. Single-channel PFC in Critical Conduction Mode (CRM)

B. Single-channel PFC in Continuous Conduction Mode (CCM)

C. Dual-channel interleaved in Continuous Conduction Mode (CCM)

D. None of the above


Summary Market drivers for Power Factor Correction

What is Power Factor and why do we need to correct it?

Definition of Power Factor (PF)

What causes PF degradation

Impacts of bad PF on power distribution and billings

How do we correct bad Power Factor?

Basic PFC topologies


Analog and Digital Solutions

Implementation with Renesas MCU and Analog & Power devices


Questions?


Enabling the Smart Society

IndustrialMotors

Smart Metering

Energy harvesting

Home Automation

Energy efficiency is key to a Smart Society

Power quality is key to efficient energy management

power factor correction – why and how? drivers for power factor correction what is power factor...

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