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Your Position: Home - Telecommunications - How does a power supply work?

How does a power supply work?

The power supply is the heart of any electronic system or machine. In this BLOG article we will explain how a power supply works on a very basic level. You will also learn more about the difference of an AC/DC converter and a DC/DC converter.

How does an AC/DC converter work?

Most of today's electronic devices and systems require a stable DC voltage. But mains electricity is based on AC voltage. A power supply converts the supplied AC mains on the input to the required DC on the output side. This is why a power supply is also called a converter or transformer.

The DC voltage (e.g. 5Vdc, 12Vdc, 24Vdc, 48Vdc) is in many cases lower than the original AC voltage, which is typically between AC 100V and 240V. The AC voltage depends on the region you are. E.g. the standards in many regions are AC 100-120V (e.g. USA, Japan) or AC 200-240V (e.g. Europe, China) and 50 or 60Hz.

So the main task of an AC/DC converter is to transform the high and dangerous AC to the lower and safe DC required by the device, system or machine.

Step by step to DC voltage

If we look at the AC diagram we see a sine wave. This means that the voltage continuously changes its polarity. The frequency of this graph is described in Hertz (Hz). A frequency of 50Hz means that the voltage changes its polarity 50 times per second.

In the first step, the high AC voltage is converted into a lower AC voltage by a transformer  The transformer also ensures galvanic isolation and thus safety. The primary circuit (dangerous mains voltage, e.g. 230V) and the secondary circuit (safe voltage, e.g. 24V) are separated from each other.

Since most devices require a DC voltage on the input side, the AC voltage must be rectified in the next step. The result of this process is shown in the DC diagram . After the rectification process, we only see positive polarity. This is realized by a bridge rectifier.


How to get a stable DC at the output?

For a stable DC supply the process of rectification isn't enough. The heavy peaks in the DC curve need to be smoothened. This is done by the output capacitor in the power supply. The capacitor can store energy very fast, which it supplies between 2 peaks. This process fills the drops to a certain amount and smoothes the curve. The result is a stable DC voltage on the output which is supplied to the load. "Load" is the term for the device, system or machine which needs to be supplied with energy.

What is a DC/DC converter?

"DC/DC converter" is a broad generic term. It includes various types of components and devices, from a tiny on-board converter up to a standalone industrial device. The following explanations apply to the latter category, as PULS is specialized in this type of products. 

Step-up or step-down DC

There are several tasks where industrial DC/DC converters can be used. One is to convert an existing DC voltage into a lower or higher DC voltage - e.g. stepping up 12Vdc to 24Vdc or stepping down 48Vdc to 24Vdc.

Refresh DC voltage

DC/DC converters which provide the same voltage on the output side like on the input side are used to refresh the DC voltage. This can be necessary in applications with long cable runs. The voltage drop on power wires is often underestimated.

Remote locations and vehicles

Furthermore DC/DC converters are necessary when the energy source provides a DC voltage, like a battery or a solar panel, for example. Therefore DC/DC converters are often used in remote locations or on trains and other vehicles with its own electrical on-board system.

Regions with unstable mains quality

Many factories work with a DC 200-300V supply internally - especially in countries where the mains quality is very unstable (e.g. India, Malaysia, etc.). In the semiconductors industry, for example, entire factories are fed via DC. In the event of a power failure, large batteries take over, preventing an entire batch from having to be discarded. Therefore many industrial AC/DC converters can also be operated with a high DC voltage (e.g. DC 110-150V and even up to DC 300V) at the input. 







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