We explain what a power supply is, the functions this device fulfills, and the types of power supplies.
What is Power Supply?
The power or power supply (PSU in English) is the device that is responsible for transforming the alternating current of the commercial power line that is received in homes (220 volts in Argentina) into the direct or direct current; which is the one used by electronic devices such as televisions and computers, supplying the different voltages required by the components, usually including protection against eventual inconveniences in the electrical supply, such as overvoltage.
Power supplies can be linear or switching:
Linear fonts. They follow the transformer scheme (voltage reducer), rectifier (alternating voltage conversion to full wave), filter (full wave conversion to direct current), and regulation (output voltage maintenance in the face of load variations).
Commutative sources. These, instead, convert electrical energy through high-frequency switching on power transistors. Linear sources are typically inefficiently regulated compared to switching sources of similar power. The latter are the most used when a compact and low-cost design is required.
Power supply features
The essential functions of the source are four:
- Transformation. There it is possible to reduce the input voltage to the source (220 v or 125 v), which are those supplied by the electrical network. A coil transformer participates there. The output of this process will generate 5 to 12 volts.
- Rectification. It is intended to ensure that voltage oscillations do not occur over time. It is attempted with this phase to pass from alternating current to direct current through a component called a rectifier or Graetz bridge. This allows the voltage not to drop below 0 volts and always stay above this figure.
- Filtered out. In this phase, the signal is flattened to the maximum; this is achieved with one or more capacitors, which retain the current and let it pass slowly, thus completing the desired effect.
- Stabilization. When the continuous and almost entirely flat signal is already available, it only remains to stabilize it completely.
Types of power supplies
The power supplies that power the PCs are located inside the case and are usually of the AT or ATX type. AT power supplies were used until the Pentium MMX when ATMs came into use.
AT power supplies have connectors to the motherboard (this differentiates them from ATX), and, in addition, the power supply is activated through a switch with a voltage of 220 v, which is a risk when handling the PC. Technologically they are pretty rudimentary and are hardly used anymore. Likewise, there was the problem of having two connectors that had to be connected to the motherboard; confusion and short circuits were frequent.
In ATX power supplies, the power supply circuit is more modern and is always active; that is, the power supply is always supplied with a low voltage to keep it on standby. An additional advantage of ATX power supplies is that they do not have an on/off switch but work with a button connected to the motherboard, which makes connections/disconnections easier. Depending on their power and the type of case, they are classified as AT tabletop power supplies (150-200 W), mid-tower (200-300), tower (230-250 W), slim (75-100 W), ATX tabletop ( 200-250W).