How to power step up step down transformer

The common application of Power Transformer is simply the power supply and you can find them in any electrical appliances and electronic devices. In daily household products you can simply get power transformers from the following items;

1. Computer power supplies and Laptop charger adapter
2. USB charger plug
3. Bug Zappers / Fly Swatter / Mosquito racket
4. Air-conditioner power supply
5. Refrigerator power supply
6. Printers power supply
7. TV power supply
8. Satellite decoder power supply
9. Audio devices power supply
10. Microwave ovens
11. Modem transformers
11. Monitor power supply
12. Game console power supply (Nintendo, Playstation, XBOX, etc)
13. Any charger plugs.
14. iphone charger
15. android smartphone chargers

What is the function / used of power transformer?

The fundamental function of transformers in the power supply unit is simply to step down or step up the voltage depending on the power usage by the electrical and electronic appliances. For example, a transformer in the 5 Volt USB charger is to step down the voltage from 220 volt AC power in the household to 5 Volt use to charge mobile phones. On the other hands transformers in Air conditioner, Refrigerator, Television, and other high powered devices to step up power from 220 Volt AC to higher voltage like 400 Volt to few thousands volt because they need more power.

Sometimes transformers also can be used to divide voltage across different circuit in a motherboard - that's why it has multiple pins of power output where a different set of pins deliver different voltages. This is very useful in an electronic circuit that requires multiple sets of the current source at different voltage rage to power multiple circuitry.

The use of transformers in the power supply unit of all electronic and electrical appliances are necessary. Not only it is safer to any other circuit design but also capable to deliver different voltages in step up or step down.

Where to find power transformer?

If you are looking for small transformers to salvage just get from any power supply part of the circuit you will find one. Some others have many power supplies ranging from big to smaller sizes - there are used to divide voltages across different sections of the circuit as some circuit require higher voltage and other smaller voltages. For example, mini transformers can be found in iPhone or android charger adapter and it is used to step down the house power source from 110 volt or 220 volts to 5 volts which is used by the phone to charge.

The image below showing a mini transformer to step down 220 Volt AC power from the main household power to 5 volts to charge cell phones and other devices.

Transformers winding type variations:

Apart from being in different sizes transformers winding also comes in many variations depending on the applications. The simplest and most common form of the transformer winding is the Step Up and Step Down where there is only a primary and secondary coil. Other variations of transformers winding are as follow.

1. Center Tap Primary and Center Tap Secondary
2. Single Primary and Dual Secondary
3. Dual Primary and Center Tap Primary
4. Dual Primary with a center tap and single secondary
5. Center tap primary and dual secondary
6. Center tap primary and single secondary
7. Center tap primary and dual secondary with a center tap
8. Flyback transformer

Each of these variations has its own functionality and application to provide the needed power to its intended circuit. A simple one is a step-up transformer is used to supply higher voltage and thus it is called the step up. On the other hands step down transformer is used to supply lower voltage but higher current (amp) to the circuit.

Advanced application of transformers can be used as RF mixers, noise reduction in audio amplifier circuits, etc.

How to power up the transformer?

The transformers can only be powered up by AC (Alternating current). The reason being is because AC generates a magnetic field from the input side of the winding coil to the output side. You can open up a and investigate the transformer is not connected by wire directly but instead is wound one or more winding on the input and output side. So the only way to transfer the power from the input winding to the output is to use magnetic force generated by the AC.

Can direct current (DC) batteries powered up a transformer? This is a question that most electronic beginners would ask. The answer is yes but it cannot be powered directly without the help of a circuit. In order to do that we can use a transistor to generate AC like current to power up the transformer. A simple circuit below demonstrates how a simple circuit using a resistor and transistor to power up a step up transformer to convert DC (battery) power to AC power.



As mentioned previously the fundamental function of the transformer in the power supply application is either to step up or step down the voltage depending on the intended applications. Below is a diagram of a step-up transformer winding where the input is from the left coil and output is on the right coil. You might want to ask is it possible to power it up the other way around and make it work as a step-down transformer? The answer is simply YES.

In the early days, before I knew anything about Transformers, it was so difficult to find specific step-up transformers and step-down transformers. Not knowing that either step up or step down transformers actually is almost the same thing and can be used interchangeably. I know this after some experiments of how it really works.

How to test low voltage and a high voltage side of the transformer?

Now we know that step up and step down transformers can be used interchangeably - this concludes that we can power up the transformer on either side of the winding. However, there is no telling which one of the winding coil sides will generate the lower and higher voltage output by just looking at the physical transformer unit itself.

If you simply use the transformer without knowing the output voltage it could ruin your circuit to burnt or having not enough voltage power. Therefore we can use an LCR multimeter to measure the inductance of the winding coil. LCR means (L = Inductance, C=Capacitance, R=Resistance) - so LCR multimeter simply means a multimeter to measure Inductance, Capacitance, and Resistance.

Below is a video demonstrating how to measure the low voltage and high voltage of the transformer using Inductance measure of the multimeter.



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