Friday, June 26, 2009
Understanding SMPS (Switch Mode Power Supply)
This is a good reference manual on SMPS that I found online.I love reading every day and find it to be very important for a repair technician to help fully understand all the circuits we work on and improve your trouble shooting skills.When you fully understand how circuits work trouble shooting failures becomes easy.This manual will help you to understand how SMPS works.Please click here or click on the photo below to download and read this reference manual.Have a great day and remember to keep reeding about electronics every day, even if it's reading something you have read before just to keep things fresh in your mind.
Thursday, June 25, 2009
Types of inverters for CCFLs
Flat-panel liquid LCDs are the display of choice in a wide range of portable products from notebook
computers, tablet PCs, and PDAs to digital cameras and portable instrumentation. Compact coldcathode
fluorescent lamps (CCFLs) provide the necessary light source in these applications, enabling a
readable display in both dim and bright ambient light.
Inverters that supply the power to turn on (strike) and run CCFLs control one of the major power
drains in any battery-powered device. These are technically challenging circuits. First, inverters must
accept a wide range of dc input voltages, typically from 3 to 14 V, and provide ac outputs of 500 to
800 V to run the lamps. Then, to ignite CCFL lamps, these circuits must provide momentary strike
voltages that typically are twice that of their run voltages. Many applications also require efficient
dimming capabilities to allow lamp output to match ambient light conditions and thus prolong both
lamp and battery life.
Typical of the consumer electronics market, inverters for portable products also face on-going
demands for ever-increasing efficiency to reduce heat and prolong battery life, while simultaneously
meeting size reduction and ever-lower cost models.
For many years, display makers employed a Buck/Royer inverter topology to strike and power CCFLs.
This analog power topology is essentially a combination of a step-down Buck voltage regulator and a
self-resonant Royer oscillator with an integral step-up transformer.To read more, and to learn about other types of inverter circuits besides the "buck royer" click the photo below.
computers, tablet PCs, and PDAs to digital cameras and portable instrumentation. Compact coldcathode
fluorescent lamps (CCFLs) provide the necessary light source in these applications, enabling a
readable display in both dim and bright ambient light.
Inverters that supply the power to turn on (strike) and run CCFLs control one of the major power
drains in any battery-powered device. These are technically challenging circuits. First, inverters must
accept a wide range of dc input voltages, typically from 3 to 14 V, and provide ac outputs of 500 to
800 V to run the lamps. Then, to ignite CCFL lamps, these circuits must provide momentary strike
voltages that typically are twice that of their run voltages. Many applications also require efficient
dimming capabilities to allow lamp output to match ambient light conditions and thus prolong both
lamp and battery life.
Typical of the consumer electronics market, inverters for portable products also face on-going
demands for ever-increasing efficiency to reduce heat and prolong battery life, while simultaneously
meeting size reduction and ever-lower cost models.
For many years, display makers employed a Buck/Royer inverter topology to strike and power CCFLs.
This analog power topology is essentially a combination of a step-down Buck voltage regulator and a
self-resonant Royer oscillator with an integral step-up transformer.To read more, and to learn about other types of inverter circuits besides the "buck royer" click the photo below.
Tuesday, June 16, 2009
Capacitive Reactance
Capacitive Reactance.Learn how capacitors effect AC circuits. Click the photo or click here.
Monday, June 15, 2009
Sunday, June 14, 2009
SMPS common failures
Most Common SMPS Problems,The following probably account for 95% or more of the common SMPS ailments:
Reproduction of this document in whole or in part is permitted if both of the following conditions are satisfied:
This notice is included in its entirety at the beginning.
There is no charge except to cover the costs of copying.
Supply dead, fuse blown - shorted switchmode power transistor and other semiconductors, open fusable resistors, other bad parts. Note: actual cause of failure may be power surge/brownout/lightning strikes, random failure, or primary side electrolytic capacitor(s) with greatly reduced capacity or entirely open - test them before powering up the repaired unit.
Supply dead, fuse not blown - bad startup circuit (open startup resistors), open fusable resistors (due to shorted semiconductors), bad controller components.
One or more outputs out of tolerance or with excessive ripple at the line frequency (50/60 Hz) or twice the line frequency (100/120 Hz) - dried up main filter capacitor(s) on rectified AC input.
One or more outputs out of tolerance or with excessive ripple at the switching frequency (10s of kHz typical) - dried up or leaky filter capacitors on affected outputs.
Audible whine with low voltage on one or more outputs - shorted semiconductors, faulty regulator circuitry resulting in overvoltage crowbar kicking in, faulty overvoltage sensing circuit or SCR, faulty controller.
Periodic power cycling, tweet-tweet, flub-flub, blinking power light - shorted semiconductors, faulty over voltage or over current sensing components, bad controller.
In all cases, bad solder connections are a possibility as well since there are usually large components in these supplies and soldering to their pins may not always be perfect. An excessive load can also result in most of these symptoms or may be the original cause of the failure. And don't overlook the trivial: a line voltage select switch in the wrong position or between positions (possibly by accident when moving the supply, particularly with PCs), or damaged.
Reproduction of this document in whole or in part is permitted if both of the following conditions are satisfied:
This notice is included in its entirety at the beginning.
There is no charge except to cover the costs of copying.
Supply dead, fuse blown - shorted switchmode power transistor and other semiconductors, open fusable resistors, other bad parts. Note: actual cause of failure may be power surge/brownout/lightning strikes, random failure, or primary side electrolytic capacitor(s) with greatly reduced capacity or entirely open - test them before powering up the repaired unit.
Supply dead, fuse not blown - bad startup circuit (open startup resistors), open fusable resistors (due to shorted semiconductors), bad controller components.
One or more outputs out of tolerance or with excessive ripple at the line frequency (50/60 Hz) or twice the line frequency (100/120 Hz) - dried up main filter capacitor(s) on rectified AC input.
One or more outputs out of tolerance or with excessive ripple at the switching frequency (10s of kHz typical) - dried up or leaky filter capacitors on affected outputs.
Audible whine with low voltage on one or more outputs - shorted semiconductors, faulty regulator circuitry resulting in overvoltage crowbar kicking in, faulty overvoltage sensing circuit or SCR, faulty controller.
Periodic power cycling, tweet-tweet, flub-flub, blinking power light - shorted semiconductors, faulty over voltage or over current sensing components, bad controller.
In all cases, bad solder connections are a possibility as well since there are usually large components in these supplies and soldering to their pins may not always be perfect. An excessive load can also result in most of these symptoms or may be the original cause of the failure. And don't overlook the trivial: a line voltage select switch in the wrong position or between positions (possibly by accident when moving the supply, particularly with PCs), or damaged.
More information at preherservices.com
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