Power Protection and Active Power Factor Correction

Learn about Active PFC power supplies and how to properly back up equipment with Active PFC to avoid unexpected shutdown and harmful component stress.

Legal NoticeWe make every effort to provide you with accurate, complete and current information. However, we offer no guarantee on information contained in this documentation. The contents of this document are provided “as is”. We reserve the right to make updates or changes of any information contained in this document without prior notice. Notably, products shown may be changed or discontinued at any time.

CyberPower Brief

Power protection and Active Power Factor Correction (PFC)

Adaptive Sinewave UPS systems Power protection that supports equipment with Active PFC power supplies

Introduction

In the last several years, the emphasis on green products in the engineering field has increased exponentially. Related issues cover not only how we can generate energy more effectively, but also how we can utilize it more efficiently to reduce waste.

As a result, manufacturers are focusing on how to transfer, utilize and retransform power more efficiently. This is es-pecially true for equipment utilizing power supplies where energy efficiency is already an important objective. Over the last few years, power supply unit (PSU) manufacturers have transitioned to focusing on efficiency issues by increasing Power Factor in addition to reliability, quality and capacity.

Power Factor (PF)

The efficiency of the power supply unit is commonly mea-sured by power factor (PF), which is the ratio of the real power and the apparent power (total power consumption), and is a dimensionless number between 0 and 1. The closer the power factor of the device is to 1, the more efficient it is. Manufacturers have begun to use Power Factor Correction (PFC) in order to increase the power factor and maximize the efficiency of power supplies.

Power Factor Correction (PFC)

Power Factor Correction (PFC) is a set of circuits that can dynamically adjust the input AC current and the DC voltage to synchronize them. This optimizes the power utility and brings the PF closer to 1. The power factor for most power supplies not utilizing PFC is typically 0.55 to 0.65. PFC is crucial for reducing wasted electrical power. It yields the fol-lowing benefits to the entire system:

1. Saving electrical power and reducing operational cost.

2. Increasing the effective capacity of the power supply system.

3. Providing a more stable supply of electric current.4. Higher efficiency also reduces heat generated.

Low PF represents lower efficiency of power management. This also implies more electrical power is needed due to higher power loss during the distribution process. If this is the case, that means the power supply system has to pro-vide more electrical power to cover the wasted energy.

Consequently, the entire system needs larger components, more powerful transformers and a more powerful distribution system for compensation. With PFC functionality, an elec-tronic device can utilize power more efficiently and reduce operational costs.

Power protection and Active Power Factor Correction (PFC) 1

Power Factor

Efficiency 0% 50% 100%

0 .5 1

Passive PFC and Active PFC in Power Supply Units

There are two distinct approaches of achieving power factor correction:

Passive PFC (PPFC) Power supplies with Passive PFC use passive components such as capacitors and inductors to reduce the harmonic current. The efficiency of the passive PFC is usually rated between 60—75%.

Active PFC (APFC)Power supplies with Active PFC uses a circuit with active components such as Boost Converter and Switch Converter along with the Control IC (Integrated Circuit) to reduce the harmonic current. This design is generally more sophisticat-ed and the efficiency of Active PFC can reach 95% or even higher.

Related Standards and Certificates

Widely recognized standards for power effi-ciency are the EPA’s current ENERGY STAR 5.0 program and 80Plus. 80Plus first issued their standards in 2004 and they were quickly ad-opted by engineers and manufacturers world-wide. In 2008, 80Plus was officially adopted as part of the US standard for ENERGY STAR 4.0. To meet the strict requirements of 80Plus, a switching power supply unit must be tested

at 20%, 50% and 100% of the rated load. The PSU must be able to retain more than 80% energy efficiency and with 0.9 true power factor or greater at all 3 levels of load to be certified.

On July 1, 2009, the EPA adopted the new standards for ENERGY STAR 5.0*. The new standards for certification require any computer using an internal power supply to have an 82% minimum efficiency at 20% of rated output, 85% minimum efficiency at 50% of the rated output, and 82% efficiency at 100% of the rated output with a power factor of 0.9 or greater at 100% of the rated load.

Compatibility between Active PFC and UPS Systems

Despite the benefits derived from the highly efficient Active PFC power supply, compatibility challenges exist between power supplies and certain UPS types. Now manufacturers (including: HP, Dell, Lenovo, Acer and more) are integrating Active PFC power supplies into products that range from high-end servers and workstations to mid-level CPUs and entry-level Desktop systems.

The following information details the primary UPS waveforms and topologies and their compatibility with Active PFC power supplies.

Two major types of UPS can be identified by the waveform of the output:

1. Pure sine wave UPS

Image 1: Pure sine wave waveform

Utility power is delivered to businesses and homes as alter-nating current (AC) with an alternating waveform signature. Alternating current has a continuously varying voltage that oscillates from positive to negative. Utility power is regulated to be a pure sine wave because generators naturally produce this waveform and it radiates the least amount of radio power.

UPS systems with Pure sine wave waveform deliver highly reliable sine wave battery output. Power produced by a Pure sine wave UPS assures that sensitive loads will receive optimal waveform output, with no interference. The output waveform of the pure sine wave UPS is shown in Image 1.


*Source: Dell Inc., www.dell.com/downloads/global/products/optix/EnergStar5.0_SpecSheet.pdf

Pure Sine wave produces continuous power output during the entire interval period, thus ensuring sensitive equipment with Active PFC power supplies work without interruption.

Until now, UPS systems with Pure sine wave output have been the best and most expensive choice for protecting servers, data centers equipment, high-end A/V electronics (TVs, audio recording devices) as well as, equipment utilizing Active PFC power supplies.

2. Simulated sine wave UPS

Image 2: Simulated sine wave waveform

A Simulated sine wave UPS (Pulse-width modulation/PWM, Stepped or Modified sine wave - see Image 2 above) is the most common waveform type and is widely deployed for all kinds of applications because of its lower component and manufacturing costs. Despite its popularity, compatibility problems may occur when using Simulated sine wave UPS systems with equipment that uses Active PFC power sup-plies.

These problems arise because Simulated sine wave output produces a zero-output state within certain time intervals that occur during the cycle of the phase change. The wave-form pattern results in a power “gap” during operation of the Active PFC equipment when switching from AC power output to simulated sine wave output (battery mode). This period of zero voltage may trigger a protection mode within a power supply using Active PFC that turns off the system.

As a consequence, electronics that incorporate Active Power Factor Correction (PFC) power supplies may unexpect-edly shut down or experience component stress (hissing or humming noise) when backed up by a Simulated sine wave UPS.*

Simulated sine wave UPS systems are recommended for low-end applications and for equipment that does not utilize Active PFC power supplies. This includes entry-level Desk-tops with non-Active PFC power supplies (models prior to 2008), basic peripherals and entry-level SOHO network devices, basic telecom equipment and low-end A/V elec-tronics.

Selecting a UPS Solution

The primary function of an UPS is to supply power to con-nected equipment when utility power fails or has poor qual-ity. Additionally, a UPS can provide the following benefits:

•Conditioning and filtering incoming power against dam-aging surges, spikes and sags

• Ensuring that equipment continues functioning in the event of a power loss

• Enabling equipment to shut down properly•Regulating the flow of electricity to equipment to prevent

crashes or freezing

For all applications, the UPS output waveform must be compatible with the protected device’s power supply (Active PFC).

UPS Types

There are three UPS topologies — standby, line-interactive, and double conversion. All three types have input circuitry, a battery and charger and a DC/AC inverter. Line interac-tive and double conversion UPS systems include additional features described below.

•Standby UPS (simulated sine wave/pulse-width modulation-PWM): Standby UPS allows equipment to run on utility power until a problem is detected. This is the most common type used for standard home computers and peripherals. Benefits include low cost, small size of footprint, and efficient operation. These systems generally provide noise filtration and surge suppression. Standby UPS systems are a strong value for small office and home equipment without Active PFC power supplies.


Zero output stateor power “gap”

*Source: Reza Bacchus, HP Master Technologist, ISS Platform Technology, BSEE

• Line-interactive UPS (simulated sinewave and pure sine wave output): The most common UPS topology for small business equipment, department servers and telecom equipment. This UPS type typically comes with Automatic Voltage Regulation (AVR) that regulates voltage by boosting or diminishing (bucking) input utility voltage as necessary before allowing it to pass through to the protected equipment. Line-interactive UPS systems are divided into these UPS sub-categories, (with the newest design—Adaptive Sinewave, included): Line-interactive, Simulated sine wave (or PWM): for basic applications using equipment that do not utilize Active PFC power supplies. Line-interactive, Pure sine wave: for mid-level ap-plications and equipment that have Active PFC power supplies.

•Double conversion online UPS (pure sine wave): This design confines protected equipment from utility power. This UPS cotinuously converts power from AC to DC, then DC to AC, delivering cleanest AC waveform to

connected equipment. Continuous power conversion and constant energy consumption makes Double conversion (online) UPS systems less energy efficient. This UPS type is reserved for protecting high availability and mission-critical equipment and data.

Adaptive Sinewave UPS Series with pure sine wave output for equipment with Active PFC power supplies

The best power protection for equipment with Active PFC power supplies is a UPS series that utilizes a pure sine wave waveform. Before making a determination, it is critical to assess the hardware sensitivity, specifications, load require-ments and applications of the electronic equipment and related services.

CyberPower’s new Adaptive Sinewave UPS technology pro-vides the most affordable battery backup solution for equip-ment and applications that do not require mission-critical power protection.


Guide to Selecting a UPS System

*Check with your manufacturer to determine if your system comes with an Active PFC power supply.

Topology

Standby Line Interactive Double conversion (online)

Wav

efo

rm

Simulated sine wave Basic Desktops with non-Active PFC power supplies (models prior to 2008)*, basic peripherals and entry-level SOHO network devices, basic telecom equipment and low-end A/V electronics. (Active PFC compliant–NO)

Basic Desktops with non-Active PFC power supplies (models prior to 2008)*, basic peripherals and entry-level SOHO network devices, basic telecom equipment and low-end A/V electronics. (Active PFC compliant–NO)

Pure sine wave (Entry-level solutions)

Entry-level Desktops w/Active PFC power supplies (models after 2009)*, mid-to-high end Desktops and Workstations*, entry- and mid-level servers, office-level Networking devices, Entry-level Telecom equipment and mid- to high-end A/V electronics. (Active PFC compliant - YES)

Pure sine wave (High availability and mission-critical solutions)

Mid-to-high level Desktops and Work-stations w/Active PFC power supplies*, entry- and mid-level servers, office-level Networking devices, Telecom applications–mid- to high-level and mid- to high-end A/V electronics. (Active PFC compliant - YES)

Mission-critical applications and equip-ment, equipment connected to generators, enterprise data center network equipment and servers, medical and scientific testing equipment, sensitive equipment that will not tolerate a transfer time of less than 2-4 ms. (Active PFC compliant - YES)

Price Low to Mid range Low to Mid range Mid to High range

Performance and functionality

Entry to Mid level Entry to High level Mid to High level

CyberPower Systems, Inc.Protect your critical equipment, data and files from dam-age or irrecoverable loss with CyberPower – the leader in UPS power protection innovation, excellence and value. CyberPower UPS products offer innovative, award-winning technology, crafted to provide unmatched functionality and reliability. Learn more at CPSww.com.

Adaptive Sinewave UPSAdaptive Sinewave UPS systems, from CyberPower, are the most cost effective pure sine wave battery backup solutions that solve the critical compatibility issues of non-Sinewave UPS products working with computing systems that utilize Active PFC power supplies (ENERGY STAR 5.0). Adaptive Sinewave UPS systems ensure equipment utilizing Active PFC power supplies does not unexpectedly shutdown or experience harmful stress when switching from AC power to UPS battery power.

Adaptive Sinewave tower modelsCP850PFCLCD (850VA/510W)CP1000PFCLCD (1000VA/600W)CP1350PFCLCD (1350VA/810W)CP1500PFCLCD (1500VA/900W)

Adaptive SInewave rackmount/Tower modelsOR1500PFCRT2U (1500VA/900W)OR2200PFCRT2U (2000VA/1320W)OR2200PFCRT2Ua (2200VA/1320W )

For more informationTo learn more about CyberPower Adaptive Sinewave UPS products, please contact your CyberPower sales representative or visit CPSww.com/ups


© CyberPower Systems, Inc., 2010CyberPower Systems4241 12th Ave EastShakopee, MN 55379

Produced in the U.S.A.November, 2010All Rights Reserved

Documents

Power Protection and Active Power Factor Correction