How to Fix a Switch Mode Power Supply
- Knowledge of Components Make sure you familiarize yourself with the components that are available in the power supply. ...
- Protection Circuit I thought I should just mention that a switch mode power supply is well preserved by what is known as protection circuit. ...
- Shorted Components within the Primary Side
Full Answer
How to fix a switching power supply?
Switching power supply repair guide. Repairing the switching power supply can be processed in two steps: 1. In case of power off, users can carry out maintenance by visual check, smelling, asking and measuring. Visual check: Open shell of the power supply to check whether the power fuse has been blown. Check internal part of the power supply.
How to jumpstart power supply?
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How to repair SMPS power supply?
Which means that the mosfet might have stopped osculating causing a short circuit through itself, allowing the entire AC to go through the components within the input supply line. How to Repair the SMPS Circuit. The shown burnt SMPS can be repaired with the following simple steps. 1) Remove the mosfet from the PCB and check it with a multimeter
How to repair a PC power supply?
Method 3 Method 3 of 3: Replacing a Failed PC Power Supply Download Article
- Purchase a new power supply of the same type as the old one. ...
- Unpack the new power supply and make sure it physically fits correctly. ...
- Using proper ESD procedures, connect the devices in your PC to the new power supply. ...
- Verify that no cables or unused connectors are stuck in the CPU fan or touching other moving parts. ...
How do you troubleshoot a switch mode power supply?
0:0023:35How to repair switch mode power supply SMPS practical ... - YouTubeYouTubeStart of suggested clipEnd of suggested clipIf we see the one line it is here. And this line is going to this filter the Westar and the otherMoreIf we see the one line it is here. And this line is going to this filter the Westar and the other side is going through this inductor.
What usually fails in switching power supply?
Typically, only a small number of components fail in switching-regulator power supplies. The most common failure is the switching transistors themselves. The transistors short-circuit, causing massive amounts of current to be drawn across the transformer, blowing the input line fuse.
How do I test a switching power supply?
1:508:58How to Test Switch Mode Power Supplies with an OscilloscopeYouTubeStart of suggested clipEnd of suggested clipTurn on and turn off time transient response power supply rejection ratio and efficiency and theMoreTurn on and turn off time transient response power supply rejection ratio and efficiency and the Scylla scope is the most common tool for making power supply measurements.
Can power supply be repaired?
If, after troubleshooting your computer power supply, you determine that the power supply is bad, we recommend it be replaced. Because of the potential hazards associated with repairing a power supply, most computer repair shops and computer companies do not repair power supplies and instead replace them for new ones.
How do you diagnose a power supply problem?
Symptoms of a failing computer power supplyRandom computer crashes.Random blue screen crashes.Extra noise coming from the PC case.Recurring failure of PC components.PC won't start but your case fans spin.
What are the symptoms of power supply failure?
Signs of power supply failurePower-on Fails (system fails to start or lock ups)Spontaneous Rebooting.Intermittent lock ups during applications.Hard drive and fan fail to spin up simultaneously (+12 failure)Overheating of power supply due to fan failure.Small brownouts that cause the system to fail and restart.More items...•
How do I use a multimeter to test a switching power supply?
Plug the PSU into an outlet and flip the switch on the back. You should hear a fan. Test every pin on the 24-pin motherboard power connector as indicated in this article. Record voltage and confirm within accepted tolerances.
How do I know if my power supply or motherboard is bad?
Check the connection for each PSU cable running to the computer hardware component. Look inside the case for the motherboard light. Usually flashing lights on a motherboard indicate a faulty or misconnected power supply.
How can I test my power supply without a motherboard?
0:031:31How to test ATX PC power supply. How to turn on ATX ... - YouTubeYouTubeStart of suggested clipEnd of suggested clipWe need to short together green wire which is power on to any of ground black wire I'm gonna useMoreWe need to short together green wire which is power on to any of ground black wire I'm gonna use this paper clip which is enough for testing purposes anyways. We can make a switch between these.
What are the common problems in power supply?
The five common power supply problems include voltage and current issues at the input and output, reversed polarity, temperature issues, and missing external components.
How do I fix my power supply unit?
10:5415:07How To Repair a Computer Power Supply (or other ... - YouTubeYouTubeStart of suggested clipEnd of suggested clipIt's probably this chip Ward's in a short circuit according to the datasheet. The ground is pin 7MoreIt's probably this chip Ward's in a short circuit according to the datasheet. The ground is pin 7 and the power is pin 12. So let's try to measure the voltage drop of the chip from power to ground.
Can I repair SMPS?
The shown burnt SMPS can be repaired with the following simple steps. 3) After changing the mosfet make sure to change the burnt rectifier diode also, and ideally change all the 4 diodes in the bridge, to ensure no weakened diodes are present in the network.
What are the most common SMPS problems?
Overheating and/or Ventilation Failures: The most common reasons of an SMPS failure is overheating. Make sure that the ventilation is free from dust and clutter. Also, do not keep the CPU in an enclosed desk.
Why does SMPS fuse keep blowing?
The weak points in SMPS are usually the power devices and electrolytic capacitors. However, capacitors usually fail by drying out, and don't fail short, so a fuse blowing is most likely a bad power device that failed in some way.
Can SMPS be repaired?
The shown burnt SMPS can be repaired with the following simple steps. 3) After changing the mosfet make sure to change the burnt rectifier diode also, and ideally change all the 4 diodes in the bridge, to ensure no weakened diodes are present in the network.
When the system is started by switching on the power supply it is called?
Answer: power booting. Explanation: webew7 and 4 more users found this answer helpful.
How does a switcher work?
The entire point of the switcher is that it rectifies the AC power line to DC, then chops the DC with a variable-duty-cycle oscillator at very high frequency so that a tiny step down transformer can be used . Transformers at high frequencies don’t need large cores or many windings for a lot of power, so they can be made tiny and at little cost. The oscillator duty cycle can be adjusted with feedback so that the regulation can be done without losing any power in the process. Thus, you can get good regulation and good efficiency at the same time.
How does AC power work?
AC power comes off the line , and is rectified through the bridge rectifier, DBRIDGE. The output charges up a big filter capacitor on the primary side CIN, which provides a filtered (but hardly ripple-free) DC voltage to the primary of the transformer, NP, as well as voltage to start the pulse width modulation (PWM) chip through resistor RSTART.
Why is the PWM capacitor so small?
Because the PWM oscillator is so fast, the transformer and the filter capacitor on the secondary side can be very small. Although that 2200 F cap may seem large, if the oscillator is running at 60 kHz, it’s a thousand times as effective as the same value off the 60 Hz line.
What happens when a PWM oscillator is running?
When the PWM oscillator is running, it sends constant pulses from the output pin. This turns on the big switching FET, QSW, which pulses the current going through the transformer. As this happens, current is induced in the transformer secondary, rectified and filtered by DOUT and COUT, and current flows from the output.
Why are transistors shutting down?
If you see a lot of small discrete transistors all over the place, a good guess is that they are involved with automatic shutdown systems, to shut down in case of high or low voltages or currents at one or more place . Troubleshooting these circuits without a manual can be a real nightmare since it can be difficult to figure out at what voltages individual parts trigger.
Why use topology converter?
Other topology converters exist and are popular when line isolation isn’t needed, but when you look at what is going on between the AC input and the DC rails on a piece of electronic equipment today, this is the basic topology used because it gives good efficiency and line isolation.
Can you have multiple switches in a box?
Not every supply is a single switching supply in a box. Sometimes you will encounter systems with multiple switchers in the same box providing multiple output voltages, each regulated. It’s more common to find multiple voltages off one transformer with a single output voltage used for the control loop but some applications require good regulation with highly varying loads.
What is the primary side of a 12V SMPS adapter?
Referring to the images above, the primary side of the unit appears to be the popular 1 amp 12V SMPS adaptor using a mosfet based switching design, and includes an opamp based auto cut off charger section at its secondary section of the board
How many amps can a bridge rectifier handle?
The diodes in the bridge rectifier appears to be the normal 1N4007 diodes which are capable of handling not more than 1 amp current, therefore if this 1 amp value exceeds the diodes can get ripped through and damaged.
Why does my AC diode burn?
The diode might have burnt due to a high current passage which in turn might have happened due to a stalled mofet inductor operation. Which means that the mosfet might have stopped osculating causing a short circuit through itself, allowing the entire AC to go through the components within the input supply line.
What is bridge rectifier?
A bridge rectifier can be normally seen at the beginning of any SMPS circuit and is introduced primarily for rectifying the mains AC to a full wave DC, which is further filtered using a filter capacitor and applied to the mosfet/inductor stage for the intended flyback primary side switching operation.
Which element is the safest and most undamaged part in a given faulty SMPS circuit?
So basically you can be rest assured that the transformer is the one element which might be the safest and the undamaged part in a given faulty SMPS circuit.
Which components need a recheck?
10) The components which needing a recheck will be fundamentally the ones which are prone to high voltage and current damage, such as small BJTs, diodes and low value resistors.
Can a capacitor be left unchecked?
Similarly, capacitors which may be rated above 200V can be left unchecked unless one of these look somewhat damaged externally.
What is power supply repair?
The power supply repair is one of the most challenging tasks for an electronic repairer and once you have mastered the circuit and the repair technique, to troubleshoot other type of circuits such as the colour, vertical, audio, high voltage and so forth would be much easier. If you are aware of how power supply or switch mode power supplies work, then you are ready to repair any kind of power supply problems in any type of equipment which include the smaller power supplies used in the
How does a switch mode power supply work?
The working principle of switch mode power supply is different from the linear type. First the AC voltage enters the RF filter circuit where its function is to prevent the Power Supply unit from causing interference on the main wiring and to a full wave rectifier (bridge rectifier) which converts the AC to produce an uneven DC output and then filter by a large filter capacitor (usually 220 Micro Farad and up to 450 volts). The clean DC voltage will then be given to start up resistors and to the input of switch mode power transformer. Once the voltage passed through the high ohms resistor (start up resistors) the voltage would drop to a value where it then goes to the VCC supply pin of Pulse width modulation (PWM) IC. The Run DC circuitthat consists of a resistor and a diode will maintain the power IC stable operation.
What components are used in power supplies?
If you have seen all the photos, you will notice that almost all of the power supplies (although the power supplies use different electronic equipment) use common electronic components like Fuse, Bridge Rectifier, Filter Capacitor, Power IC, Power FET, Switch mode transformer, Optoisolator IC, Secondary output diodes, Secondary filter capacitors and etc. Due to this configuration, if you carefully study how power supply works (with the help of block and schematic diagrams) and know how to test electronic componentsin the power section, I don’t see any reason why you can’t successfully repair any power supply.
Why would lightning strike a SMPS?
1) Because of more electronic components used in the power supply circuit and when failure occurs , it could take out many parts in the SMPS for example; lightning strikes on the SMPS.
What happens when a PWM IC receives voltage?
Once the PWM IC received the voltage, it will produce a signal to drive the transistor (normally FET) and produces a change in the magnetic field in the transformer primary winding. The changing magnetic field induces voltage in the secondary windings.
What is the power supply function of a laptop?
Basically, all of the power supply functions are almost the same which is to produce output voltages for various secondary circuits.
Do SMPS circuits operate the same?
Although there are some differences between the designs of SMPS, they basically still operate base on the same principle. Please turn to the next chapter to read the full SMPS circuits operation in details.
