The Importance Of Current Sense Resistor In Switch Mode Power Supply


Current sense resistor is usually located in the switch mode powersupply section. Newer version of monitor-the b+ (boost) circuitalso have this current sense resistor. If you repair electronicequipment especially the switch mode power supplies, the currentsensing resistor is connected to the source pin of power FET (fieldeffect transistor) and the other end to HOT GROUND. The value of current sense resistor is in the range of 0.1 ohm to about 1 ohm.The values are depends on the design of each power supply.

In monitor power supply where pulse width modulation (pwm) ic UC3842are used. Pin 3 of this power ic is called I-sense which meanscurrent sense and this pin is connected to source pin of POWER FET.The purpose of this current sense circuit is for overcurrent protection.This circuit usually samples the voltage drop across a resistor in serieswith the switching fet transistor. If the current rises abnormally due tosome short circuit in the secondary side such as a shorted secondary diodeor horizontal output transistor (HOT), the voltage will exceed a referencelevel and shutdown the pulse generator which is the PWM ic. This circuitprovides protection to components in the event a problem occurs.In some cases where overload happen-the power section will blow and most of the time the components changed are fuse, power fet, pwm ic,zener diode and current sense resistor.

Do you know that a small change in this current sense resistor valuehave a great impact on the secondary output? A little change in valuesay from 0.22 ohm to 0.44 ohm can caused your ouput voltage to dropinto half! I have seen a lot of repairer can't detect this type ofproblem (low output voltage) due to that they used analog or digitalmeter that don't have the low ohms range. You can't differentiate if the low ohms resistor has its value changed by using normal meters.I personally use the Dick Smith ESR Meter which have the capabilitiesto check resistor value down to 0.01 ohm! If you don't have this special meter you may just direct replace the current sense resistorto see if the generated secondary output will back to normal voltage.

Another tip is that if the current sense resistor in the monitorB+ circuit have changed value it will caused the output in theboost circuit to become low and you will have a small width displayand of course the high voltage will become low as well. Instead of24Kv it becomes 15-18Kv.

Jestine Yong is a electronic repairer and a writer. For more information on electronic repair please visit his website athttp://www.noahtec.com/electronic-repair-articles.htm





Latest News:



Site: Yahoo! News Search Results for news
JCDecaux in talks for News Outdoor Group in Russia (AP via Yahoo! News)
French outdoor advertising firm JCDecaux SA said Thursday it is negotiating to buy Russian rival News Outdoor Group from global media company News Corp. JCDecaux and News Corp. in talks to combine outdoor ad groups (International Herald Tribune)
The News Corp. chief executive, Rupert Murdoch, has recently expressed nervousness about investments in Russia, where News Outdoor generated the bulk of its revenue last year. News Corp tightens grip on Premiere with new CEO (Reuters via Yahoo! News)
Rupert Murdoch tightened his grip on German pay-TV broadcaster Premiere by appointing News Corp executive Mark Williams as CEO in a move to get the company back on track. SEC Looks Into UAL Stock Scare; Implications For Online News? (paidContent.org via Yahoo! Finance)
A ton of digits have been devoted to this in other spots but the SEC's decision to investigate takes it to another level. The backstory: a six-year-old news story about UAL declaring bankruptcy made it into the Tribune-owned Sun-Sentinel's current news flow, was picked up by a Google News bot and, via a reporter for a newsletter, made it onto Bloomberg News. News Corp says Mark Williams interim Premiere CEO (Reuters via Yahoo! News)
News Corp. executive Mark Williams has taken over as chief executive of German pay-TV broadcaster Premiere in an interim capacity, News Corp. said after the move led to renewed takeover speculation. News Corp. says Mark Williams interim Premiere CEO (Reuters via Yahoo! News)
Mark Williams, a News Corp. executive named late on Wednesday as chief executive of German pay-TV broadcaster Premiere, has taken over in an interim capacity, a News Corp. spokeswoman said on Thursday. JCDecaux in talks to buy News Corp. billboard unit (AP via Yahoo! Finance)
In a deal that would create the world's largest outdoor advertising company, French conglomerate JCDecaux SA said Thursday that it is in talks to buy Russian rival News Outdoor Group from global media company News Corp. Weekly world news quiz (BBC News)
At the end of another week, test your knowledge with our world news quiz. UPI NewsTrack Entertainment News (UPI)
Kanye arrested in paparazzi scuffle ... Report: Critic smacked Ebert with binder ... Cafe Tacvba nominated for 6 Latin Grammys ... Groban to perform TV songs at Emmys ... News from United Press International. United shares climb after news debacle (UPI)
CHICAGO, Sept. 11 (UPI) -- A computer program assigning dates to news stories was partly to blame for a sell-off of United Airlines stock Monday, a Google spokesman said.

Site: news - Google News
Palm Shares Soar As New Smartphone Wins Wall Street Praise - CNNMoney.com

CBS News

Palm Shares Soar As New Smartphone Wins Wall Street Praise
CNNMoney.com - 4 hours ago
The stock price has nearly doubled over the last two days since the company announced its new Pre smartphone and WebOS operating system at the Consumer ...
Palm's new smart phone steals the show MarketWatch
The pre's got Mojo: a developer speaks about Palm's new SDK Ars Technica
Palm's new Pre smartphone gets lots of good buzz USA Today
Kansas City Star - CNET News
all 723 news articles
Live-blog: Obama news conference on Intel choices - USA Today

FOXNews

Live-blog: Obama news conference on Intel choices
USA Today - 5 hours ago
The news conference is now set to get started at 10:45 am ET (though Obama has been known to begin things early). Hit the "refresh" button, ...
Video: Analyst Weighs in on Obama's CIA Pick AssociatedPress
News Analysis A Difficult Road Awaits Panetta at the CIA New York Times
Obama appointments...Illinois debate...Truce call ignored ... Reiten Television KXMB Bismarck
USA Today
all 3,325 news articles
Obama: New layoffs show need for urgent action - The Associated Press

BBC News

Obama: New layoffs show need for urgent action
The Associated Press - 4 hours ago
If it works better than something I've proposed, I'll welcome it," Obama told a news conference. He spoke shortly after the Labor Department reported job ...
Video: Obama: New Layoffs Show Need for Urgent Action AssociatedPress
Breaking News: Barack Obama is the next President of the United ... Christian Science Monitor
US Senate Democratic Leaders Outline New Agenda Voice of America
WDEF News 12 - The Black Chronicle
all 5,752 news articles
More news from your region - MSNBC

ABC News

More news from your region
MSNBC - 3 hours ago
By EricShangraw They're officially calling for the Governor's head in Springfield today.Driven by anger and politics, the Illinois House voted to impeach ...
Video: Raw Video: Burris Arrives at Blagojevich Hearing AssociatedPress
Governor impeached...Stocks lower...No ceasefire | KXNet.com North ... KXMC
AP Top News at 11:21 pm EST The Associated Press
WGIL Radio News - KDWN
all 15,892 news articles
Health Buzz: Flu Drug Failure and Other Health News - U.S. News & World Report

U.S. News & World Report

Health Buzz: Flu Drug Failure and Other Health News
U.S. News & World Report, DC - 4 hours ago
U.S. News tells you how to keep your family safe from bird flu. Oprah Winfrey's very public battles with her weight continued this week, ...
Bad news for UGA fans: Florida is just getting started - Atlanta Journal Constitution

Seattle Post Intelligencer

Bad news for UGA fans: Florida is just getting started
Atlanta Journal Constitution,  USA - 4 hours ago
For fans of the Georgia Bulldogs, I have some bad news and some WORSE news today. The bad news? Florida, your hated rival, just won its second national ...
If it's settled on the field, USC wins; Pac-10 news, notes & links The Oregonian - OregonLive.com
BCS Title Game: The News Media Predicts New York Times
News and Notes from Halftime of the BCS Title Game ABC Action News
The Morning News - The Oregonian - OregonLive.com
all 6,367 news articles
FDA Mismanagement, Gaza?s Ambulance Runs and New Support for a ... - New York Times

OverTheLimit.info

FDA Mismanagement, Gaza?s Ambulance Runs and New Support for a ...
New York Times, United States - 3 hours ago
A Long Island man who donated a kidney to his wife says he wants it back now that they?re getting divorced, The Daily News reports. ...
Business news in brief Philadelphia Inquirer
all 181 news articles
New Classmate PC all about ?ecosystem? - ZDNet

New Classmate PC all about ?ecosystem?
ZDNet - 1 hour ago
We?ve known for a while that Intel was working a touch-enabled reference design for their new Classmate PCs. It wasn?t until I had an opportunity this week ...
Commodore Announces Launch of New Computer Products Series at CES 2009 - CNNMoney.com

Commodore Announces Launch of New Computer Products Series at CES 2009
CNNMoney.com - 2 hours ago
CommodoreŽ (PINKSHEETS: CDRL) today announced the launch of an exciting new series of computer products at the Consumer Electronics Show 2009 in Las Vegas, ...
Foreign Ministry: China supports new UN resolution on Gaza - Xinhua

WELT ONLINE

Foreign Ministry: China supports new UN resolution on Gaza
Xinhua, China - 11 hours ago
China called for effective implementation by all parties concerned of the new resolution and an immediate ceasefire in Gaza, Qin noted. ...
Video: UN supports Gaza ceasefire plan RussiaToday
AP Top News at 7:12 am EST The Associated Press
New UN Gaza resolution proposed Aljazeera.net
International Herald Tribune - Jane's
all 37,535 news articles

MORE RESOURCES:
Site: Yahoo! News Search Results for hardware
IBM offers hardware-based encryption for x servers (SearchSecurity.com)

IBM is calling its VAULT hardware-based encryption tool the first of its kind and says the price point should appeal to small and midmarket companies. Everything you want to know about the Zune 3.0 release and new hardware (ZDNet)

I posted the news about the new Zune 3.0 software the other day, but if you want to learn all the details of the new Zune hardware, accessories, and Zune 3.0 update coming to you next week then check out Jason Dunn's detailed 6-page writeup on his recent visit to... Uganda: Hardware Guru Now Dares Music (AllAfrica.com)

Phiona Natoolo a.k.a Phinato, 29, is one of the biggest businesswomen in Uganda's hardware business, owning several shops at Nakasero and Kansanga [Phinato Hardware]. 9/11/2008 Daily Hardware Reviews -- ATI Radeon HD 4670 Edition (AnandTech)

DailyTech's roundup of hardware reviews from around the web for Thursday... Hardware store owner shot, abducted in QC (GMA News)

MANNILA, Philippines - Unidentified armed men shot and abducted a 45-year-old hardware store owner in Quezon City Wednesday night, a radio report said early Thursday. US video game sales rise 9 percent in August (AP via Yahoo! News)

U.S. sales of video game hardware and software rose 9 percent in August to $994.8 million, boosted by the popularity of the newly released "Madden NFL 09." Snazzy Microsoft mice happy hardware tale (Seattle Times)

It's hard to compete with Steve Jobs announcing new iPods, but in a roomful of 100 journalists at Microsoft's computer-hardware launch event Wednesday in Seattle, I saw only a few tracking Jobs while Microsoft entertainment and devices boss Robbie Bach delivered his news Microsoft hardware rumors (IT World)

There has been some buzz lately about Microsoft getting into the PC hardware business. There have been no announcements, although the Microsoft muckety-mucks have raised the possibility as part of a theoretical discussion. GotVoice Announces Voicemail Server Support for Service Providers, Voicemail Hardware Vendors and IVR Companies (Marketwire via Yahoo! Finance)

GotVoice, Inc., the voice messaging company, today announced voicemail server support for service providers, voicemail hardware vendors and IVR companies. The company is publicizing its ability to retrieve voicemail from carriers and PBX installations without the need for upgrades or changes to existing systems for seamless voicemail-to-text and digital audio file integration. US video game sales rise 9 percent in August (San Francisco Chronicle)

U.S. sales of video game hardware and software rose 9 percent in August to $994.8 million, boosted by the popularity of the newly released "Madden NFL 09." Americans bought $384.6 million in video game hardware, up 3 percent from a year ago, lead by sales of... Site: hardware - Google News
New Classmate PC all about ?ecosystem? - ZDNet

New Classmate PC all about ?ecosystem?
ZDNet - 1 hour ago
Obviously, the hardware is a key component. Both the convertible Classmate and the 2nd-generation ?clamshell? Classmate (the more traditional laptop style ...
Intuitive Convertible Design for the Intel-Powered Classmate PC ... WELT ONLINE
Intel launches convertible 'kid-friendly' netbook Reg Hardware
all 14 news articles
MWSF 2009: Apple Launches iLife '09 Hardware Up-to-Date Program - O'Grady's Power Page

Macworld

MWSF 2009: Apple Launches iLife '09 Hardware Up-to-Date Program
O'Grady's Power Page, PA - 49 minutes ago
During the events of Macworld Expo this week, Apple introduced its iLife '09 Hardware Up-To-Date program, which allows users who purchased a new Mac after ...
iLife Up to Date: when $3000 isn't enough Ars Technica
iPhoto ?09: What you need to know Macworld
News from the Mac world New Zealand Herald
Computerworld - CNN International
all 187 news articles
CES Interview: Samsung?s Jong Woo Park on Interactive TVs - New York Times

Canada.com

CES Interview: Samsung?s Jong Woo Park on Interactive TVs
New York Times, United States - 6 hours ago
?In the next five years, we are not only going to provide hardware, but content through our devices, in an easy more convenient way,? he said. ...
Samsung Rolls up New LCD TVs, Plans to Increase Sales by 10 Percent eFluxMedia
Have TV makers achieved synergy with the Internet? San Diego Union Tribune
Samsung, Yahoo, Intel Put TV Widget Pieces in Place PC Magazine
Motley Fool - Christian Science Monitor
all 692 news articles
The Hardware Behind WebOS: Palm Pre - Digitaltrends.com

CBS News

The Hardware Behind WebOS: Palm Pre
Digitaltrends.com, OR - 23 hours ago
Palm has released a smoking new piece of hardware to accompany its long-awaited OS, and it brings many of the features hardcore smartphone users have been ...
Can Pre really help Palm survive? MarketWatch
Palm WebOS is all about the Mojo ZDNet Blogs
Palm Pre Impressions, Part One TreoCentral
BetaNews - Ars Technica
all 723 news articles
Microsoft's Bach: we'd do Zune differently - CNET News

The Money Times

Microsoft's Bach: we'd do Zune differently
CNET News, CA - 19 hours ago
So why did Microsoft make a foray into hardware, which alienated its device-maker partners (remember PlaysForSure?), and probably cost the company tens or ...
BARRON'S BLOG: A Running Blog Of Microsoft CEO's CES Speech CNNMoney.com
Microsoft's Bach talks about Zune's future Seattle Post Intelligencer
Microsoft's Search Strategy: Mo' Money Less Problems istockAnalyst.com (press release)
WindowsForDevices - TechNewsWorld
all 382 news articles
Hardware Device Secures Internet for Small Business, Home Users - San Diego Business Journal

Hardware Device Secures Internet for Small Business, Home Users
San Diego Business Journal, CA - 4 hours ago
It is also much less expensive than other hardware solutions, such as rack mounts, used by larger businesses. ?Small companies have no use for a ...
Bits and Pieces Hardware store history from 1853 - Wooster Daily Record

Bits and Pieces Hardware store history from 1853
Wooster Daily Record, OH - 11 hours ago
In response to Louis Meyor's recent query about Harding Hardware, Wooster historian Harry McClarran sent me a newspaper article he wrote several years ago ...
Saving money with used network hardware: Tricky but doable - Search Networking

Saving money with used network hardware: Tricky but doable
Search Networking - Jan 8, 2009
By Shamus McGillicuddy, News Editor Buying used networking hardware is a great way to hold down costs in these tough economic times, ...
Hardware & Lumber announces 80 redundancies - Jamaica Observer

Jamaica Gleaner

Hardware & Lumber announces 80 redundancies
Jamaica Observer, Jamaica - 14 hours ago
Leading local hardware retailer Hardware & Lumber is yet another Jamaican company forced to cut its workforce in light of the global financial crisis which ...
H&L cuts 80 jobs in restructuring Jamaica Gleaner
all 2 news articles
The Macworld Lab at Expo - Macworld

The Macworld Lab at Expo
Macworld, CA - 23 hours ago
There?sa lot of new hardware from third-parties at the show that are deserving of attention. In this special From the Lab edition of the Macworld Podcast, ...
Home | Site Map | Resource Links