Hi there! As an electrical engineer, I often get asked about the various power supply units used to power modern electronic systems. So in this post, I will overview the common types of power supplies and what makes them suitable for certain applications.
What is a Power Supply Unit?
Let‘s first demystify what a power supply actually does. In essence, it converts electrical power from the available electric supply and transforms it into forms required by electronic devices or circuit loads. As you know, everyday gadgets like mobile phones, PCs, LED lights operate on DC voltages like 5V, 12V, 24V DC whereas household AC voltages range from 110-240V.
Power supplies act as the vital interface bridging this mismatch between the available electric supply and the power needs of electronic equipment. With the phenomenal growth in electronics over the years into every domain, reliable and efficient power supplies became indispensable.
But with such a diverse variety of loads like sensitive microprocessors, large motors, high-power medical/industrial RF devices etc. – there cannot be a one-size-fits-all power solution. And that led to the evolution of the many kinds of power supplies we have today.
So without further ado, let me walk you through the 11 commonly used types of power supplies:
1. DC Power Supply
The most familiar type is the ubiquitous DC or direct current power supply unit used in virtually every electronic gadget we use daily. Like charging adapters for phones, laptops; PC power supplies and so on.
Inside these is essentially an AC to DC converter – converting 110-240V AC from wall outlets down to the required low DC voltage levels +5V, +9V, +12V and so on. How do they work?
- The mains AC first passes through a transformer to lower the voltage
- Then gets rectified by diodes into interrupted DC pulses
- Capacitors and chokes then smooth out those pulses into nice, stable DC
- Feedback controllers maintain steady voltage against load changes
Benefits of using DC power?
- No ripple/noise – good for analog/digital loads
- High efficiency – small adapters can provide lots of power
- Compact PCB designs possible – large transformers not needed
With these advantages, its no wonder DC power pervades most of modern electronics we use regularly!
2. AC Power Supply
On the other hand, many heavy-industry loads still need rugged AC power – motors, heaters, welding equipment and so on.
AC or alternating current power supplies step up or step down voltages for these AC loads. They tap into the mains AC feed and use transformers and regulators to output desired high/low AC voltages.
Key traits of AC power supplies:
- Produce any required AC voltage needed by industrial loads
- Galvanic isolation for noise rejection and safety
- High load capacity – can drive motors, heaters etc.
- Phase control allows precision regulation
Typical applications include:
- General machine tools – mills, lathes needing high current
- Servo/induction motor drives in factories
- Very high force electromagnetic applications
- Places where DC not suitable for physical reasons
So in summary, AC supplies feed variable frequency drives, actuators, magnetics and other equipment incompatible with DC power.
3. Linear Power Supply
Now linear power supplies are the simplest and most affordable type of AC to DC converters. They are best suited for low power applications up to few hundred watts.
Inside them, the power flow follows a linear ‘straight‘ path using ordinary diodes, capacitors and voltage regulators – without any switching/transformation.
Advantages offered by linear supplies:
- Inexpensive and easy to build
- Low output ripple/noise compatibility
- High stability under line/load changes
- Low EMI due to absence of switching elements
Typical linear supply applications include:
- Battery chargers, LED drivers, audio amplifiers etc.
- Analog electronics needing clean DC power
- General lab power for electronics hobbyists
While the low cost and simple topology makes them popular, there are some downsides too – poor efficiency and heat issues. In fact most of the input energy gets wasted as heat only! Anyway, linear supplies work great for modest power needs if extreme efficiency is not required.
4. SMPS – Switch Mode Power Supply
For most digital electronics applications today, the switch mode power supply or SMPS reigns supreme when it comes to efficiency and versatility. Their smart switching conversion technique squeezes the most juice out of every watt!
An SMPS works on pretty much the same principle as a DC supply but uses some clever tricks:
- The input supply gets chopped at a high frequency by oscillating the DC input on/off rapidly using transistors/MOSFETs
- So a small high frequency transformer easily steps down the voltage
- Post which rectifiers reconstruct the desired DC output
- Output filters smooth everything out
Why does this switching help?
- Allows a very compact and light power supply unit
- Significantly higher conversion efficiency – as high as 95%
- Much better output regulation against input line/load changes
- Overall lower costs
With those remarkable merits, SMPS dominate higher power applications like PC power supplies, data centers, LED lighting etc. needing the best efficiency in minimum space.
5. Programmable Power Supplies
Now what if you need to repeatedly vary or sequence power supplied to a device under test? That is where programmable power supplies (PPS) come into the picture!
Unlike manual supplies, PPS allows you to dynamically control all parameters like voltage, current limits and observe load regulation through external programming.
- Modern PPS provides remote control over USB, Ethernet etc.
- Dedicated software helps program voltage sequences
- Graphing output characteristics across tests is possible
- Multiple modular units can be paralleled if required
Why is programmability useful?
- Automates tedious testing procedures efficiently
- Control power perfectly and repeat tests accurately
- Stress test devices by producing deliberate aberrations
- PC interface enables advanced analysis
With those pros, PPS are ubiquitous in fields like:
- Research labs developing electronics
- Production lines testing boards
- Power electronics testing
- Electrical vehicle development
- Space simulations etc.
So in a nutshell, what sets programmable power supplies apart is the total flexibility and control they lend in prototyping and testing power sensitive devices.
6. Uninterrupted Power Supplies (UPS)
Mission critical installations like hospitals and data centers cannot afford to ever lose power – even for a fraction of a second.
This is where uninterrupted or uninterruptible power supplies (UPS) prove to be literal lifesavers! They seamlessly bridge power failures by supplying battery backup power.
Here is how UPS systems work:
- Constantly charge batteries using normal input AC supply
- The moment outage happens, seamlessly switch over to batteries
- Once AC power resumes, smoothly transfer loads back to AC
Apart from just the backup, UPS also provide:
- Voltage regulation – correct under/over voltages
- Power conditioning against surges/spikes
- Load balancing for 3 phase input
- System health monitoring/diagnostics
With those vital safeguards, UPS systems protect vulnerable installations like:
- Server rooms holding crucial data
- Patient life support equipment in hospitals
- Air/railway traffic control systems
- Petrochemical process monitoring
Ultimately, a good UPS acts like protective armor – insulating sensitive critical systems from disastrous external power disturbances.
7. DC-DC Converters
While the previous power supply types dealt with conversion between AC and DC; many applications involve changing DC levels also – stepping 12V to 5V for instance.
DC-DC converters efficiently transform DC voltages to other needed DC values. They come packaged as small surface mount ICs or discrete switch mode power stages.
Common DC-DC converter types and traits:
- Buck converter – steps down higher voltages
- Boost converter – elevates lower voltages
- Buck-boost – can produce lower or higher voltages
- Extremely compact and light weight designs
- Very high conversion efficiency – upto 98%
What are some typical applications?
- Battery powered consumer gadgets
- Industrial IoT sensor nodes
- DC microgrids, EVs, solar systems etc.
- Point-of-load converters in computers
- Any product needing multiple DC voltages
So in essence, DC-DC converters allow stepping up/down DC rails powering various sub-systems as per need – while retaining high efficiency.
8. AC Adapters
Almost all portable consumer electronics rely on external AC adapters (or wall warts) for power. These adapters convert AC mains into required low voltage/current DC needed by gadgets like phones, tablets, routers etc.
Some merits offered by removable AC adapters:
- Allows lighter, cheaper product designs
- Interchangeability between many brands, provided connector type matches
- Improved safety – no exposed high voltages
- AC plug heads can adapt to global socket types
In light of those benefits, adapters find ubiquitious application powering:
- All portable electronics – phones, tablets, peripherals
- LED lamps, small household appliances
- Toy & hobby electronics, test equipment etc.
Rest assured pretty much any low voltage compact electronics device will be bundled with a suitable AC adapter!
9. RF Power Supply
We have been mostly discussing power supplies for information processing equipment so far. But many industrial applications like RF heating, particle accelerators require high power Radio Frequency AC supplies instead.
These specialized RF power supplies take normal AC input but efficiently generate high power Radio Frequencies in ranges like:
- High Frequency – 3-30 MHz
- Very High Frequency – 30-300 MHz
- Ultra High Frequency – 0.3-3 GHz
Using dedicated transformer tank circuits and vacuum capacitors, RF power supplies can deliver anywhere from 1kW to 1MW power levels!
Some common RF power supply applications are:
- RF heating in industrial processing
- Particle accelerators and plasma generation
- Broadcast radio transmitters
- Medical equipment like RF diathermy
- Radar and satellite communication links
So in nutshell, RF power supplies fill the need for producing high frequency AC power demanded by these RF devices.
10. High Voltage Power Supplies
At even more eye-popping extremes on the voltage scale are high voltage power supplies. Unlike conventional power supplies producing below 50V, these special supplies generate hazardous DC voltages going into thousands or even millions of volts!
They achieve such extra high voltages (EHV) using techniques like:
- Cascaded voltage multiplier stages
- Special high frequency step-up transformers
- Sophisticated control/protection mechanisms
Why this need for such intense voltages?
- Energize X-ray tubes and detectors
- Power particle accelerators like CERN
- Demonstrate arcing/corona discharge
- Electrostatic painting/air filtration
But with great power comes great responsibility! So these high voltage supplies utilize advanced safety mechanisms like:
- Enclosure interlocks, warning lights
- Multi-rated insulation, guard rings
- Current limiting resistors
- Remote monitoring
Trust me, casually touching these supplies live wires will barbeque you in microseconds! So don‘t try your DIY experiments here unless you really know your stuff.
11. Bipolar Power Supplies
The final power supply variety I want to talk about is bipolar power supplies. These can output both positive and negative voltages from the same unit to drive tricky floating loads.
Inside, multiple output amplifier channels with both polarities feed the power rails. That enables bipolars to:
- Source or sink current bi-directionally
- Charge condensers fully without DC biasing
- Perfectly simulate AC waveforms
- Actuate magnetic components needing push-pull drive
With those merits, bipolar power supplies find use in:
- Testing ADC/DAC devices
- Audio power amplifiers
- Solenoids, transformer, motor driving
- Mixed signal circuit prototyping
- Any floating application requiring positive and negative voltages
So I hope this guide gave you a solid overview explaining the gamut of power supplies used in modern electrical engineering – powering everything from tiny ICs to mighty motors!
Of course, I have only scratched the basics here while these topics can go very in-depth technically (which maybe we can reserve for future posts)! Anyway, please drop any other power supply types or applications I may have missed… Happy to discuss more!
