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December 13, 2023
The DC to AC converter is a small, but essential, piece of technology that will likely continue to proliferate in its use and popularity, so let’s dive into exactly what it is, how it works, and its place in the future of sustainable infrastructure.
First of all, a DC to AC converter is an electronic circuit with transistors that converts direct current (DC) power, into alternating current (AC) power. It’s also called an inverter. The technological opposite of an inverter is a rectifier, which converts AC power to DC power. Currently, rectifiers are used more often than inverters. In fact, we wouldn’t be able to operate LED lighting, charge our phones, power our laptops, or watch Netflix (among other things) without rectifiers. To understand why that is, we need to talk about electricity. Specifically, the two types of electricity: AC power and DC power.
Direct Current (DC) power and Alternating Current (AC) power are the two types of electricity. AC power is the most widely used, as it’s typically what’s generated, transmitted, and distributed throughout power grids. DC power, on the other hand, powers about 70% of our devices, including all digital devices and equipment. One of the reasons why digital devices, like phones, laptops, cameras, and smart appliances, require DC power is because they feature transistors. Transistors are the backbone of integrated circuits and require DC power to operate. Thus, if AC power is distributed throughout buildings, these DC devices need to convert the AC power they get, into the DC power they need.
The next question you might be asking yourself is: if DC power is so widely necessary, then why do power grids distribute AC power?
Although the full answer is more complex, you could simply say that power grids are outdated. The longer answer to that question is that AC power was established as the standard electricity type back in the late 19th century (over 100 years ago). The War of the Currents (represented in the hit movie “The Current Wars” with Benedict Cumberbatch) was a historical event where advocates for AC power, Tesla and George Westinghouse, found themselves pitted against Thomas Edison, an advocate for DC power. If you want to know more about the War of the Currents, we’ve written an entire blog post about it called “Why AC Power REALLY Won The Current Wars”. The result of the War of the Currents was ultimately that AC power won because the infrastructure for it was less expensive and complex. You see, AC power is compatible with transformers, and DC power is not. Transformers are an essential part of power grids because they allow voltages to be stepped up or down, enabling higher voltages to be sent along further distances, and lower voltages to be safely distributed throughout communities and buildings. Not to mention, transformers provide electrical isolation, which gives them an added safety benefit. Thus, AC has become the prominent type of electricity that powers our homes and buildings. This also means that rectifiers are increasingly utilized to convert AC into DC power for our digital devices, and other DC powered devices (such as LEDs or variable speed motors).
1. Voltages can easily be stepped up or down
Because the electrical current of AC power oscillates, it has a frequency (usually of either 50Hz or 60Hz depending on each country’s standards). Although there’s a lot of physics to it, all you have to know is that this frequency is what allows AC power to work with transformers, and so can pretty easily have its voltages stepped up or down. This is what allows the infrastructure for AC power grids to be cheaper than the infrastructure for DC power grids.
2. Voltages can be easily isolated
Transformers not only step voltages up or down, but also isolate them for safety. Electrical isolation provides a means to separate two circuits, while still enabling power transfer from one circuit to the other. By disabling direct electrical connections, electrical isolation creates a barrier that helps protect against shock, fire, and equipment damage due to lightning strikes, short circuits, and more.
3. AC power is safer to switch off
If you’ve ever switched a light on or off, or plugged something in, you may have seen or heard a very small electrical shock. That shock is technically called an electrical arc, and it happens when you opened or closed the AC power circuit right when it was at the highest or lowest point of its frequency cycle, meaning at its highest possible voltage. Luckily, with AC power, that cycle occurs 50 to 60 times a second. So, before you know it, voltage levels lower to zero, ensuring you’re not in contact with high voltages for very long. Because DC power doesn’t have a frequency, it remains at this high voltage and is thus less safe to shut off or turn on (using a mechanical switch) because DC electrical arc will last longer and generate more heat (melting the switch components).
4. The infrastructure for AC power is already established
Most of our power grids and cables are set up to distribute AC power throughout the world, and it would be expensive to tear this infrastructure down and rebuild it. Not to mention, such a large construction project would be very harmful to the environment.
5. Many devices are compatible with AC power
Although I’ve mentioned that more devices require DC power in this modern era, there are still many devices that require AC power, especially if they are older. For example, dryers, large kitchen appliances, and hot tubs.
6. More electrical generators for AC power
Most forms of electrical generation, including coal, natural gas, hydroelectric, and nuclear power plants, inherently generate alternating current (AC) power. This is in contrast to solar power, which is a notable exception as it primarily produces direct current (DC) power.
1. When comparing AC and DC power at the same voltage, AC power suffers from all three major types of line losses (resistive, capacitive, and inductive)
Although having a frequency results in many benefits for AC power, it also results in this disadvantage. Ultimately, the predominant cause of most line losses is the frequency of the oscillating current in AC power that leads to consequential energy loss in the form of heat.
See this quote from the article we wrote about line losses:
“This is essentially where the misconception that DC power is less efficient came from: because people associate DC power with lower voltages, they might assume DC power is just less efficient. However, if we were to compare AC and DC distribution at the same voltage level (high or low), AC power would suffer from all three types of line losses, while DC power would only suffer from certain types of resistive power losses, making AC power ultimately less efficient at all voltage levels.”
2. AC power is less safe to touch than DC power
But I thought you said it was MORE safe? It's true that AC power is less prone to arc faults than DC power but, when it comes in contact with your skin, AC power can pass through into your nerves with less resistance. Because it can pass through your skin more easily than DC power, AC power is more likely to cause heart fibrillation. This subject can be controversial, but this table shows that a larger magnitude of DC is required to cause the same dangerous effect as compared to AC.
3. A lot of cumulative energy is wasted when DC devices need to convert AC into DC power
Many rectifiers integrated into the drivers of DC powered devices (like LED fixtures) are very inefficient, wasting about 20% of the energy consumed by the device. Although this might not seem like a lot, this energy waste adds up significantly over hundreds, thousands, or millions of devices. This energy waste will only accumulate if something isn’t done, as the proportion of DC to AC devices grows every year.
1. Suffers from less energy wasted during power distribution and transmission
Because DC power doesn’t have a frequency, it suffers from less line losses than AC power when compared at the same voltage. I covered this more extensively above.
2. Many DC devices are intrinsically more efficient than AC devices
As the world prioritizes greener technology, many devices are becoming more efficient. For example, a DC water pump could be two times more efficient than an AC model with the same wattage. Additionally, LED lights are our most efficient source of lighting, and they also require DC power.
3. DC power is required for modern, digital devices
Without DC power, or the rectifiers that make it possible to convert AC to DC power, we would not be able to use our modern devices, such as smartphones or laptops.
4. Safer to touch (less likely to cause heart fibrillation)
As covered above, DC power is safer to touch when compared to AC power at the same wattage. This is because AC power is more likely to cause significant harm, such as heart fibrillation, when compared to DC power at the same wattage. With that said, you should avoid coming in contact with any electrical circuits unless you know what you’re doing. Later in this article, I'll cover a new technology called Fault Managed Power (FMP) that makes DC power completely safe to touch.
5. Easier to store (for solar power batteries etc.)
Batteries store energy in the form of chemical potential. That chemical potential can only be released as DC power. The implications of energy storage are endless, from enabling electrical generators for remote cottages, to clean backup generators for a hospital.
6. Plays a major role in renewable energy generation
Part of the reason DC power supports the push for renewable energy generation is because it's easier to store. Furthermore, solar panels produce DC power and, although there’s a long way to go for energy storage technology, much DC power can be stored in batteries to prolong the usage of the energy generated by solar panels. This means that, if there’s cloud cover for a while (for example) power can still be distributed to the home or building from the backup battery.
1. It’s not simple or cheap to transmit or distribute DC power throughout power grids
As we covered earlier, DC power doesn’t have a frequency, which means that it doesn’t work with transformers. Although there are power grids that transmit DC power, they are only implemented when power to be transmitted is planned to pass the “break-even” distance. To explain further, because DC power suffers less from line losses, at a certain point it is worth it to splurge for the additional equipment required to transmit DC power (because those costs will be made up for in efficiency savings).
2. More dangerous to switch off (more prone to arc faults)
See the “Pros” of AC for a further explanation on this.
Another “Con” that I could’ve added to the DC power list (up until a little over a year ago) is that it’s difficult to distribute higher voltages of DC power throughout buildings. The reason this was a challenge (until recently) is because DC power isn’t compatible with transformers, and so can’t be isolated as easily as AC power (even though it could be converted with buck and boost converters to higher and lower voltages). Without electrical isolation, it’s next to impossible to safely distribute high voltages of electricity.
So, what changed? An intelligent safety feature was standardized in the 2023 version of the National Electrical Code (NEC) called “fault managed power”. Fault-managed power systems (FMPS) constantly monitor cables for defined faults, and power is shut off if any occur (such as human touch). You can read about this further in our article dedicated to fault-managed power systems. Although these systems are now recognized by the NEC, there are still only a few companies with these power systems on the market, including our company, Cence Power.
As you can see, there are many advantages to DC power and, according to a 2018 study, experts broadly agree that adopting direct current (DC) power systems in commercial and residential buildings would result in safer, more energy efficient buildings. As we’ve covered, there are many reasons why power grids still mostly generate and distribute AC power but, with technological developments in the electrical industry, it looks like the War of the Currents either has, or soon will be, reignited.
Next, let’s move back to electrical inverters. With this background in the advantages and disadvantages of AC and DC power, you might have a better understanding of why and when DC to AC conversions are necessary. One specific application for DC to AC converters is microgrids with uninterruptible power supplies (UPS). Most microgrids utilize solar panels, which generate DC power. However, because microgrids must distribute power to homes with AC electrical systems, an inverter must be used to convert DC to AC power. This is just one of many examples.
But how does an inverter work? In order to convert DC to AC power, the inverter can use one of many techniques, like an H-Bridge for example, which transforms the one-way flow of DC power into the alternating flow of AC. Transistors play a pivotal role in this conversion, as they continuously alter the flow of DC current, achieving the desired AC output by switching at a specific frequency (Ex. 50Hz or 60Hz).
Inverters come in two types: Modified Sine-Wave (MSW) and Pure Sine-Wave (PSW), and converting DC to AC power is generally a two-step process:
In the current landscape, rectifiers, or AC to DC converters, play a predominant role because most of our infrastructure is set up for AC power generation, transmission and distribution. Our existing systems are rooted in AC power, as it won the War of the Currents over 100 years ago. As outlined in the “Pros" and “Cons” section of this article, AC power offers advantages such as easily adjustable voltages, and easy electrical isolation. However, as we envision a future where DC power becomes more prevalent, the reliance on inverters is poised to grow significantly. This will be driven by the rise of renewable energy sources like solar panels, the increasing efficiency of DC-powered devices, and the proliferation of devices that require DC power to operate,
If our infrastructure were to eventually catch up with the demand for DC power, we would be living in a DC-centric world, and inverters would actually replace rectifiers as the most commonly used conversion device. They would, in fact, be indispensable when it comes to operating any AC powered electrical relics. When you think about it, our world as it stands today could not effectively operate without rectifiers, as we have become dependent on our DC powered devices, such as smartphones and communication technologies. However, we would probably not be as reliant on inverters as we currently are on rectifiers, because less and less devices require AC power, and so we are becoming less reliant on these AC powered devices. With this in mind, if you consider the possibility of a shift from AC to DC infrastructure, there would probably be a reduction in the number of overall conversions needed, which would ultimately reduce wasted energy that can currently be attributed to inefficient AC to DC conversions. As I mentioned before, many of these conversions waste about 20% of the consumed energy of a load. Thus, eliminating the need for rectifiers with a DC-centric infrastructure, as well as proliferating the world with DC powered devices, would significantly reduce energy waste and, subsequently, carbon emissions from electrical usage in buildings. This paradigm shift not only highlights the need for technological advancements and investments in inverter technology but also opens new avenues for efficiency and sustainability in our evolving energy landscape.
We improve the value of commercial and multifamily buildings with an intelligent DC power distribution system that's pain-free to install. It combines the benefits of low-voltage wiring practices with voltage capabilities of up to 450 Volts DC.
