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Revision: Aug 1. Document Number: For technical questions within your region: [email protected], [email protected] 1 UF - UF Rev. C3. U. F. 1 - U. F. 4. Fa st R e c tifie rs. UF - UF Fast Rectifiers. • Low forward voltage drop. Condition: New: A brand-new, unused, unopened and undamaged item in original retail packaging /(where packaging is applicable/). If the item comes direct.

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Uf4007 Diode Ebook

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In this Agreement, words importing a singular number only shall include the plural and vice versa, and section numbers and headings are for convenience of reference only and shall not affect the construction or interpretation hereof.

UF 1. Any provision of this Agreement which is held to be invalid or unenforceable by a court in any jurisdiction shall, as uf diode such jurisdiction, be severed from uff Agreement and ineffective to the extent of such diofe or unenforceability without invalidating the remaining portions hereof or affecting doide validity or enforceability of such provision in any other jurisdiction.

Nothing in this Agreement shall be construed as creating a joint uf diode, agency, partnership, trust or other similar association of any kind uf diode the parties hereto.

Any such audit shall not interfere with the ordinary business operations of Licensee and shall be uf diode at the expense of ON Semiconductor. RS Components Statement of conformity. Request for this document already exists and uf diode waiting for approval.

UF Active Pb-free 1. This Agreement may not be amended except in writing signed by an authorized representative of each of the parties hereto. The product does not contain any of the restricted substances in concentrations and applications banned by the Directive, and for components, the product is capable of being worked on at the higher temperatures required by lead—free soldering The restricted substances and uf diode allowed concentrations in the homogenous material are, by weight: Ultrafast Recovery Rectifiers 1A, Vishay Semiconductor Vishay ultrafast recovery rectifiers have very uf diode reverse recovery uf diode as low uf diode 15ns and voltage levels as high as V.

Price Each In a Pack of High surge current capability. Diffused Junction. Low Forward Voltage Drop. High Current Capability. High Surge Though some writers and datasheets refer to "1N series", a 1N is a watt Zener diode unrelated to the 1N Though some writers and datasheets refer to "1N series", a 1N is a watt Diode 1N Techshopbd ; Diode 1N Model : PCM TechshopBD, Bangladesh.

Diode 1N Description; Specification; Documents; Comments [1 ]. This is an The fuse F provides protection against circuit faults and effectively isolates the circuit from the AC supply source. Thermistor R limits the initial peak inrush current drawn by the circuit at start up. The function of the bridge rectifier is to convert the incoming AC voltage into DC voltage and the filter capacitor usually have the value of uf Volt to remove the ripples and this will provide a nice DC voltage source to the primary winding of switch mode power transformer.

The DC voltage that you get is measured across the two pins of the filter capacitor using a multimeter. In some power supply design, you could see that there are capacitors connected across each diode in the bridge rectifier as seen from figure 4. The function of the capacitors is to suppress the RFI signals generated by the rectifier diodes. This component capacitor sometimes could be found parallel with another resistor which is required to satisfy the main isolation requirements.

If the bridge rectifier is shorted, then the main fuse would surely blow. In some cases, it could also cause the power IC, power FET and corresponding components to blow as well.


If the filter capacitor value drops, open circuit or the ESR value had gone high, it may cause no power symptom, power blink or unstable voltage in the secondary side. After the VDC goes through the start up resistors, the voltage will drop to about 16 VDC start up voltage depends on the type of SMPS design and this voltage is use to kick on the oscillator in the power IC the first time. After the kick starts, even if the start up resistors have been removed, the supply will continue to operate because it now gets the supply from another source which is the secondary winding in the primary side as seen in figure 4.

This is called the Run DC circuit. As the large filter capacitor discharges the power IC requires additional voltage to maintain stable operation thus additional circuit, i. Run DC circuit is provided to the power IC from the secondary winding so that the circuit voltage source becomes stable.

It consists of a resistor R to prevent peak rectification of spikes, a diode D , to rectify the incoming signal from the transformer which is then smoothed by C to give a DC level. Figure 4. Sometimes it could also cause intermittent power problem. That means sometimes you can turn on the SMPS but after you have switched off the supply and turned it on again, it would not work. Wait for a while and try a few more times, the SMPS will then begin to start again.

This is what I called as intermittent no power problem. In other words, the output voltage can be varied by changing the frequency or duty cycle of the FET or bipolar transistor drive signal waveform as seen in figure 4.

Note: When the FET turns off, the leakage inductance of the transformer induces a voltage spike on the drain node. In order to protect the power FET Q against inductive spikes from the transformer primary and to reduce ringing, components R, C and D are placed in the circuit refer to figure 4.

These parts are less likely to fail than the other components in the power supply. Basically the operation is the same as in figure 4. In some cases, it might even blow the Main fuse.


With these three components in each of the output line, the outputs generated are clean DC and suitable for various circuits loads. The amount of 34 voltage generated in each output depends on the total turns in each of the secondary winding of switch mode transformer. The more turns it has, the higher output would be generated. Low ESR capacitor C provides filtering.

Inductor L and capacitor C form a second stage filter that significantly attenuates the switching ripple across C and ensure a low ripple output. Snubber networks comprising R and C damp high frequency ringing across diode D, which result from leakage inductance of the transformer windings and the secondary trace inductances.

The output voltages may drop and be unstable, causing problem to the respective circuit or the whole circuit.

Some call this sampling circuit as sensing circuit. Normally only one output voltage source is required to be sampled, because if the particular output voltage source is too low or too high, generally all of the other output voltages may vary too. The sampling circuit usually consists of only a few resistors and in some designs, a preset could be found.

Note: In some SMPS designs, the sample voltage was taken from the hot side primary side feedback winding to provide a signal to the power IC in order to control the power level delivered to the load as shown in figure 4. Tracing backward from this pin, it will lead you to the feedback winding at pin 7 of T TL is an adjustable precision shunt regulator IC and in some SMPS designs you could notice there are also few components around this circuit.

If this IC or corresponding components have problem, it will cause power shutdown, power blinking, low output power and even totally no power at all. The phototransistor acts as an output device while the LED acts as an input device. That means if the LED light intensity is great, the phototransistor will conduct even more and vice versa decreases and increases its resistance proportionally thus controlling the input to the oscillator in Power IC through feedback pin as seen from figure 4.

Note: The feedback circuit also provides isolation between the cold ground LED side and the hot ground phototransistor side of the power supply. In some designs, the error signal feedback is developed 39 from the hot side secondary winding of the power supply and requires no isolation as seen from figure 4. The primary sensing hot side feedback-figure 4. It is used especially for the low end market low power, low budget.

Secondary sensing the regulation circuit is more expensive but has a higher performance. It is used especially in the medium and high end market. The protection circuit is designed to protect the components by shutting down either part or all of the power supply in the event problem occurs.

There are four common types of protection circuits that can be used by SMPS designers for circuit protection against the following dangerous conditions. If the designers did not place this OVP circuit in the primary side, then they will definitely design at least one in the secondary side.

It senses the over voltage conditions and shut down the power supply if they occur. Once it is shut down, you need to remove the AC main and replug to get it turn on again. This is how the circuit works. The limitation of the start up circuit is that the voltage developed tends to fluctuate with the switching frequency of the power supply.

Due to this problem, the Run DC circuit was developed so that the voltage source to the Power IC becomes stable refer to page The Run DC circuit voltage source was derived from the secondary winding T in the primary side when the primary winding of the transformer was energized.

If the power supply has already shutdown, you will need to power Off the SMPS and turn it on again in order to restart the power supply.

If more than 27 volt across the zener diode, the zener diode will conduct to ground and this would cause the start up voltage to drop to zero volt and thus shutting down the power IC. If the excess voltage happens for a long period, the zener diode would go short circuit and may blow up the power section components. However, if the 43 excess voltage happens only for a split second, the power supply would shut down and as usual you need to turn off the SMPS and restart it.

The protection circuit of this circuit are R, zener diode 8. If the voltage produced exceeds 8. Due to now Q has very low resistance between collector and emitter fully turn on , this cause Q to fully turn on and cause the power FET to cease operation because the gate signal now is going to ground.

Remember, some designs can have more than one OVP circuit. This circuit usually samples the voltage drop across a resistor in series with the switching transistor FET or Bipolar Transistor if the transistor draws too much current.

If the current rises abnormally, the voltage will exceed a reference level and shut down the output waveform of the power IC thus no output power produced from the secondary side.

Note: The over current sensing resistor can increase in resistance value and cause a false shutdown. The value may be increased slightly and cause an intermittent shutdown condition.

NTE QUICKCross Download | NTE Electronics

The value is usually very small from 0. For your information the Blue ESR meter has the function to check very low ohms resistor value. The function is just the same as in figure 4. If the voltage reaches 0. R is the key component in this over current shutdown.

Replacement For SMD Diode

Excessive current is when 0. This short lowers the Q of the transformer secondary absorb all the power and the oscillator stops because of insufficient feedback voltage from T pin 6 via PC, into IC pin 6 to sustain oscillation.

Although the SCR resets when no more current flows through it, the oscillator cannot start again. The oscillator will restart when the AC plug is removed.

If the Power IC overheats exceeding certain temperature, usually to degree Celsius , this circuit inside power IC turns off the IC and latches to close or lock it. Note: This thermal shut down condition happens most probably due to three reasons: a The Power IC itself has overheating problem. For example, a faulty fan in the computer power supply could cause the power supply to shut itself off due to the hot air could not be sucked out. In order to fully understand how many protection circuits are used in SMPS or electronic equipment SMPS , one has to get the exact schematic diagram to analyze it or to get the service manual where all of the protection circuits could be explained in that manual.

The arrangement of electronic components to form the protection circuits could be different from one design to another and all of the four protection circuits mentioned are only guidelines for you to understand how these protection circuits works. For your information, the standby circuit is always active when the Television is plugged into an AC line source. The Main power supply starts to function and turns ON the television.

If missing 5 volts then check the standby power supply circuit. Remember that the standby circuit is also an SMPS. Troubleshooting and repairing the standby power supply is just the same when you are checking the Main power supply. If the standby power supply did not have any output or have lower output than normal, you can start to trace from the AC input till the secondary diodes at the output. Since standby power supply design do not have many components standby power supply is physically smaller and has lower power handling capabilities then the Main power supply , you can completely test all the electronic components with your meter in a very short time.

Remember that, the standby power supply have to function first before the Main power supply could work. If the standby power supply has correct output but the main power supply is 53 still not operating then you should make sure that the Microcontroller IC is generating output that can trigger the relay so that the AC supply could flow to the Main power supply. Assuming the Microcontroller is functioning then you should focus on the Main power supply section.

1n4007 vs uf4007 pdf

For your information, not all designs will use relay as many designs use Optoisolator IC to control the output power of the Main power supply. This means the moment the AC is plugged in, the standby power supply will output a 5 volt to Microcontroller IC and this IC will output a signal to Optoisolator IC to control the output power.

In other words, this type of power supply will have two Optoisolator IC, one is for regulation purposes refer to page feedback circuit while the other is for standby operation.

Please see figure 4. Power factor pf is defined as the ratio of the real power P to apparent power S , or the cosine for pure sine wave for both current and voltage that represents the phase angle between the current and voltage waveforms. The power factor can vary between 0 and 1, and can be either inductive lagging, pointing up or capacitive leading, pointing down.

Since this book is more on troubleshooting, I will only concentrate of its basic functions and will not touch on all the formula about power factor. What is Power Factor Correction PFC Power Factor Correction is the practice of raising the power factor in order to allow power distribution to operate at its maximum efficiency.

Unlike most other appliances, switched mode power supplies tend to be constant power devices, drawing more current as the line voltage reduces. Also, in common with many static rectifiers, maximum current draw occurs at the peaks of the waveform cycle. European regulatory standards are now beginning to require power factor correction and harmonic reduction. This mean that the Non-PFC power supplies are no longer recommended.

This kind of design has the following advantages; namely they are low in cost, easy to design, simple structure and only require a filter to correct. However, they have the following disadvantages; large dimension of filter, heavy and low efficiency resulted from thermal and voltage decrease while current passes through the filter.

This is because it uses a circuit to correct power factor. Active Power Factor Correction also diminishes total harmonics, automatically corrects for AC input voltage, and is capable of a full range of input voltage. Placing a current regulated boost converter stage between the bridge rectifier and the main input capacitor figure 2 can help correct the power factor.

The inductor L is now connected in series with the unregulated input. When the Mosfet transistor is turned on by the signal from the Power Factor Correction Control IC a charging current flows through the Mosfet and through the inductor.

When the Mosfet is off, the field in the inductor begins to collapse. This induces a voltage across the inductor.

It can be seen that the inductor acts like a pump, receiving energy when the switch is closed and transferring it to the capacitor when the switch is 58 opened.

The diode prevents main input capacitor C from being discharged when the switching Mosfet transistor is turned on again. The boost converter attempts to maintain a constant DC bus voltage on its output while drawing a current that is always in phase with and at the same frequency as the line voltage.

Another switch mode converter inside the power supply produces the desired output voltage from the DC bus. For more information you can find this IC specification from the Internet. You need to check the power IC data sheet to see if there is power factor correction circuit built into it or not. Understanding all of the circuits that I have explained above is very important for higher chances of success in SMPS repairing. Whenever if there is a problem with power supply you can at least know which section 60 gives problem and concentrate on that particular section.

Since I could not cover all kinds of power supplies in the market, I urge you if possible to get the schematic diagram of the equipment power supply that you are working on and compare and analyze it by referring to the 11 circuits that I have explained above. Once you have truly understood your type of equipment power supply, troubleshooting and repairing the power supply would be much easier. No matter what kind of designs a SMPS is, it must have the electronic components that are listed below in order to function.

I will also explain the possible causes that these electronic components can cause. Opening a circuit under a high current conditions can save electronic components from damaged and prevents overheating, which could cause fire.

The fuse can breakdown on its own due to the life span or from a mild surge. Normally in this condition, replacing with a new fuse will solve the problem.

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