Theory Power Supply

What is a Power Supply?

A power supply is a standalone device within an electrical system that provides power. It can convert alternating current (AC) to direct current (DC) and vice versa, as well as step up or step down voltage.


Types of Power Supplies

Secondary-Side Regulated Power Supply (Transformer Power Supply)

There are various types of power supplies. The secondary-side regulated power supply, or transformer power supply, converts AC voltage to the desired output using a transformer and an iron core. One drawback is the relatively high power loss of several watts from the grid. However, these types of power supplies are outdated and rarely used in modern times.

Primary-Side Regulated Power Supply (Switching Power Supply)

The primary-side regulated power supply, or switching power supply, transfers energy at a high frequency. This allows the use of smaller transformers for lower power levels. It delivers regulated DC current and voltage and is short-circuit protected. However, switching power supplies generate interference due to their high frequency, necessitating the inclusion of measures for electromagnetic compatibility. Even with such measures, complete elimination of interference is challenging.

Capacitor Power Supply

A capacitor power supply uses the capacitive reactance of a capacitor to reduce the mains voltage. This is suitable for low currents.

DC/DC Converter

A DC/DC converter, also known as a linear or switching regulator, converts a DC voltage into a higher or lower DC voltage. When the DC/DC converter provides a lower voltage, it is called a step-down converter; conversely, it's called a step-up converter. An industrial DC/DC converter takes the available input DC voltage, and a transformer provides galvanic isolation. The voltage may be stepped up or down as needed and is subsequently smoothed.

DC/AC Converter (Inverter)

A DC/AC converter, or inverter, transforms DC voltage into higher or lower AC voltage. The basic principle involves regularly interrupting the available DC voltage using an electronically controlled switch. This leads to a distinction between self-commutated inverters or island inverters and externally-commutated or grid-commutated inverters.

Self-commutated inverters can independently switch their own phase and frequency, block or pass current. Additionally, they adjust the amplitude of the generated AC voltage to match the grid frequency. However, they suffer from high switching losses, complex circuit design, and a limited power range.

Externally-commutated inverters are designed to require a fixed AC voltage and frequency on the AC side. The power electronics switch only after reaching a defined voltage level. These inverters offer a wide power range, high efficiency, and a simple switching design


Standards

In high-voltage situations, safety standards are crucial. These safety standards can be categorized into three types:

Basic Safety

This involves reducing the risks arising from the power supply itself, such as fire, electric shock, burns, and general injuries, to an acceptable level.

Essential Performance

This means ensuring that the entire system functions correctly without any malfunctions in the power supply.

Functional Safety

Functional safety considers the entire system and focuses on the risk of errors and resulting damage. Typical risks include voltage interruptions, overvoltages, and undervoltages.