Testing Belkin's "Zero Standby Power" USB Charger: Measurements, a Cable Surprise, and a Teardown
イチケン / ICHIKEN
Ichiken reviews a Belkin 67W USB charger whose packaging advertises "zero standby power" as an energy-saving feature. (The video description lists it as the Belkin CubicCharger 67W.) The video asks three questions. How much lower is its standby power than other chargers? Does that low standby power come with any trade-offs? And what inside the charger makes it possible? The speaker measures standby draw, efficiency, and heat, then takes the unit apart. They conclude that the idea is worthwhile, but they also find a caveat that, in their words, undermines the product's core concept.
How Standby Power Was Measured
Ichiken wanted to see the charger's true performance, so they powered it from an AC source that produces a low-distortion sine wave, set to 100V, with a power meter between the source and the charger. With only the charger plugged in and nothing connected to it, the meter showed a current of about 0.3 mA and an active power reading of roughly 3–4 mW.
The meter also shows reactive power. The speaker set it aside because reactive power does not affect electricity bills for ordinary households. The standby reading kept fluctuating instead of settling, so they took a time average. For the Belkin charger, the averaged standby power came to about 3.3 mW.
Comparison With Other Chargers
Ichiken then measured chargers they already owned from Anker, CIO, UGREEN, Apple, and other well-known brands. The Belkin unit was by far the lowest at 3.38 mW. Apple's 40W charger came second at 18.2 mW, and a CIO charger was third at 38.8 mW. The speaker observed that typical chargers seem to draw around 40–50 mW. They said they could not tell whether this reflects each manufacturer's design choices or holds for USB chargers in general. They also noted a pattern: chargers with higher rated output seemed to have higher standby power.
What It Means for the Electricity Bill
To translate these numbers into cost, Ichiken used Tokyo Electric Power Company rates as a reference and rounded the unit price to 40 yen per kWh. Left plugged in all year, the Belkin charger costs about 1.2 yen in standby power, the Apple charger 6.4 yen, and the CIO charger 13.6 yen. The difference between chargers is between a few yen and a few tens of yen per year. The speaker admitted that, honestly, this is a difference they could easily shrug off.
Why Conversion Efficiency May Matter More
The speaker argued that a charger's power conversion efficiency while it is actually charging likely matters more than its standby power. Conversion efficiency is how much of the AC power drawn from the outlet ends up as usable DC power for USB charging. Higher efficiency means the charger wastes less power as loss during conversion, so total consumption falls.
To show the scale, they ran two simple scenarios. In both, the charger delivers 30W for 30 minutes per day, 365 days a year, which the speaker likened to charging a phone to about 80%.
- At 90% efficiency: the charger itself loses 3.33W, which cannot go toward charging. Over a year, that adds up to 0.61 kWh.
- At 91% efficiency: the loss drops to 2.97W, or 0.54 kWh per year.
The speaker plotted these annual charging losses on the same graph as the standby power estimates. Raising efficiency by one percentage point saves only 0.07 kWh a year under these conditions, which they described as not a big impact. They added that improving a charger in this class beyond about 90% is actually quite hard. A 1-point efficiency gain requires cutting the power loss by nearly 10%.
They stressed that this estimate assumes only 30 minutes of charging per day. In use cases that constantly supply tens of watts, standby power becomes almost negligible, and charging losses and conversion efficiency start to dominate.
Belkin's Measured Efficiency
Ichiken measured the Belkin charger's efficiency across its outputs. The peak was 91.4% at 20V output. Chargers in this class often land in the 91–92% range, so the speaker rated the result as fair to good. Their conclusion: the low standby power does not come at the cost of efficiency.
Heat and Thermal Throttling
A thermal camera showed a maximum temperature of about 65°C, which the speaker called a standard temperature rise for a recent USB charger.
They also tested for thermal throttling, where a charger deliberately lowers its available output to keep from overheating. In the test setup, the charger continuously delivered the maximum power it could output. At the start it supplied 67W while its surface temperature rose. About 20 minutes in, with the surface at 58°C, throttling kicked in and output dropped to 50W. The speaker described this as a protective action that keeps the surface temperature and the internal circuitry from getting too hot. The temperature kept climbing after that and leveled off at 68°C about two hours into the test.
The Cable Problem: eMarker Chips Break Zero-Standby Mode
While editing the video, Ichiken realized they had missed an important assumption. All the standby measurements were taken with no USB cable attached. In real use, many people leave the cable plugged into the charger after they finish charging. So they re-measured with a cable attached.
With a cable connected to the Belkin charger, standby power jumped about tenfold to around 30 mW. It did not come back down even after sitting for about an hour. The speaker remarked that they felt they had seen something they weren't supposed to see.
The cable they had used contained an eMarker chip. When they connected a cable without an eMarker, standby power did not increase. Their findings:
- With an eMarker cable, the charger does not enter zero-standby mode.
- With a non-eMarker cable, it does enter zero-standby mode.
In a formal comparison with an eMarker cable attached, the Belkin charger went from 3.3 mW to 32.4 mW, which puts it at roughly the same level as other chargers. The speaker suspects the attached cable activates the internal circuitry and knocks the charger out of zero-standby mode. For the other chargers, standby power barely changed with or without a cable. The speaker guessed that their internal circuits may already be running even with no cable attached.
Ichiken therefore recommends that anyone who wants the zero-standby benefit either use a cable without an eMarker or unplug the cable after each use.
Weighing the Pros and Cons
The main advantage is that standby power is nearly zero. At about 3 mW, the charger costs only around one yen a year in electricity even if it stays plugged in year-round.
The main disadvantage is that, depending on the cable, the charger's standby power ends up no better than any other charger's. The speaker considers this a rather fatal flaw that subverts the product's concept at a fundamental level. Beyond that, they had not found other problems in their own use. However, they noted that some Amazon reviewers report that, depending on their device setup, the charger entered zero-standby mode on its own and stopped outputting power.
The speaker also took a broader view. Standby power per charger is small, but summed across everyone's chargers it becomes enormous. If a zero-standby mode like this were mandated, each unit's effect would be small, but the overall effect could be very large. On that basis they said they could highly commend the idea and the attempt to reduce standby power.
Teardown: Thermal Materials and Build Quality
With the outer shell removed, Ichiken found a blue, soft, silicone-like material. They believe it is a thermally conductive filler that bonds components together thermally. It was not applied on all sides, only in certain areas.
A graphite sheet, presumably for heat spreading, was attached to the back of the USB ports. However, the sheet did not actually adhere to the components, and parts of it left large gaps. The speaker was unsure it contributes much to heat transfer, and said it was unclear whether this was intentional or a manufacturing defect.
The internals consist of four circuit boards.
Circuit Design and Components: Heavily Renesas
The circuit is a conventional flyback converter power supply. Many of the semiconductors come from the Japanese company Renesas, and the speaker noted that the circuit matches a configuration shown on a Renesas web page almost exactly. The major components:
- Power transistor: a Transphorm part (Transphorm was acquired by Renesas in 2024). Internally, it cascodes a normally-off low-voltage silicon MOSFET with a normally-on GaN HEMT, so the pair behaves as a normally-off transistor. The speaker called the structure slightly interesting.
- Flyback controller: the Renesas iW9870, which the speaker's research traced to Dialog Semiconductor (acquired by Renesas in 2021).
- Secondary-side synchronous rectification controller: the iW610, also Renesas.
- Buck-boost controller: an Intersil part (Intersil was acquired by Renesas in 2018). The charger has two USB-C outputs, and this part handles cases where the two ports need to output different voltages.
- USB PD controllers: two iW780 chips. They are Renesas parts, but judging by the model numbers they originally came from Dialog Semiconductor.
How the Zero-Standby Mode Works
According to Ichiken's analysis, the low standby power comes from the flyback controller IC and the PD controller IC working together when no USB cable is connected. The PD controller detects that no cable is attached. The flyback controller then puts the whole circuit into a low-power state in which it almost comes to a standstill, which brings standby power down dramatically. For this to work, the ICs themselves must also be designed for very low power consumption in standby.
As for why connecting a cable raises standby power, the datasheet offers a clue. It states that when this flyback controller and PD controller are combined, standby power will be under 5 mW with no USB cable connected. In other words, the chip combination's low-power spec is defined for the no-cable condition, so connecting a cable can take the charger out of zero-standby mode. The speaker declared the mystery solved.
Conclusion
Measured with nothing attached, the Belkin charger drew about 3 mW, essentially zero. Simply connecting a USB cable with a built-in eMarker, however, raised it to roughly the level of a typical USB charger. Ichiken still called the effort to cut standby power eco-friendly and a very interesting initiative, and said they hope more USB chargers like it will appear.
Hello. Today, I've got an interesting USB charger that claims zero standby power. I will disassemble and review it. This product is a 67W USB charger from Belkin's BoostCharge Pro series. It looks like an ordinary USB charger. Looking at the package, it says, "Zero standby power saves energy." With the recent increase in electricity rates, I'm sure many of you will find zero standby power very appealing.
Compared to other chargers, how much is standby power reduced? Are there advantages and disadvantages to reducing standby power? I'll investigate. In addition, I'll disassemble this USB charger and check its internal structure. But first, here is today's sponsor.
New product design is not progressing as expected. We want to set up a production system, but we don't have time. Are you facing challenges such as these? Today, I came to Kyushu Ten, a company that can solve such problems. Its core business is the design, development, and manufacturing of wireless, communications, and in-vehicle equipment. We'll see how it can help solve your problems.
First, we came to the design and development room. From specification studies and wireless circuit design for wireless communication equipment to electronic circuit design, printed circuit board design, embedded software development, and mechanical design, complete development is possible. During development, this equipment is used for evaluation. As you would expect from a company with wireless communication technology at its core, the facilities are quite substantial.
Next, we came to the production line. They have the latest production lines in a clean room. Manufacturing can be carried out under high quality control. This is just the component mounting line. Next to it is an even larger assembly area. By the way, this factory is located in Nagasaki Prefecture, where earthquakes are rare. Another feature is that this reduces the risk of production line stoppages due to natural disasters. For companies looking for a contractor to handle everything from design to manufacturing, let Kyushu Ten handle the whole thing as a high-quality, one-stop shop.
Now, let's see how much standby power it consumes. This time, we experimented with this setup. To see the charger's original performance as accurately as possible, we use an AC power supply that can produce a sine wave with low distortion. We connect a power meter and USB charger to it and measure power consumption—in this case, standby power.
Now let's actually do it. Power on. It's at 100V now. Connect a USB charger here. This is what the power meter shows. The current is very low: only about 0.3mA is flowing. Let's adjust the current range. Let's do it this way.
Active power is shown at the top. This is the power consumed by the USB charger, meaning standby power. It is about 3 to 4mW. Below that, reactive power is shown. Since reactive power has nothing to do with electricity rates for the average household, I don't particularly care about it this time. Below that is the current. This indicates how many amperes are flowing from the outlet to the charger. The current is very low, about 0.3mA.
Just plugging in the charger gives a power value that fluctuates and doesn't settle, so we decided to take a time average of the power. The standby power of the Belkin charger, the star of the show, is about 3.3mW.
This time, I'll also compare standby power with other chargers. We'll look at chargers I own from well-known brands such as Anker, CIO, UGREEN, and Apple.
I've finished measuring standby power. These are the results. All the chargers measured this time are lined up, and Belkin's standby power is by far the lowest in the group, at 3.38mW. The runner-up is Apple's 40W charger at 18.2mW. Next is the CIO charger at 38.8mW. A typical charger seems to consume about 40–50mW. I don't know whether this reflects manufacturers' design choices or is something we can say about USB chargers in general, but the higher the charger's rated power, the higher its standby power appears to be.
Now let's look at how much this low standby power affects electricity costs. Here's a graph of annual electricity costs due to standby power. For the unit price of electricity, I'll refer to Tokyo Electric Power Company's rates and use a round figure of 40 yen per kWh. Belkin costs 1.2 yen per year, the runner-up Apple costs 6.4 yen, and third-place CIO costs 13.6 yen. You can see a difference of a few yen to a few tens of yen. From my point of view, the difference with or without standby power is honestly small enough to accept.
I thought there might be a difference, and I've been thinking about it. More than a USB charger's standby power, I think its power conversion efficiency during use might have a greater effect. What is a USB charger's power conversion efficiency? As this diagram shows, it indicates how efficiently AC power from an outlet can be converted into DC power used for USB charging. The higher the charger's power conversion efficiency, the lower the power loss generated by the charger itself during conversion, and the lower the total power required.
How much does charger efficiency actually matter? Let's try two simple calculations, with conversion efficiencies of 90% and 91%. First, suppose we use a USB charger with a conversion efficiency of 90% to charge at 30W for 30 minutes a day, 365 days a year. For 30W for 30 minutes, imagine charging a phone to about 80%. At 90% conversion efficiency, the USB charger generates 3.33W of power loss. This 3.33W cannot be used for charging; it is wasted. Calculating this gives an annual energy loss during charging of 0.61kWh.
Suppose the power conversion efficiency increases from 90% to 91%. Under the same conditions, the power loss generated by the USB charger is 2.97W. The annual energy loss during charging is 0.54kWh.
You can see how much impact these numbers have by comparing them with this graph. This graph estimates annual standby energy consumption. The annual energy loss during charging that we calculated earlier and the annual standby energy consumption shown on this graph are actually roughly comparable. Based on the previous calculation, increasing efficiency from 90% to 91%, an increase of one percentage point, reduces energy loss by 0.07kWh. You can see that the impact of increased efficiency is not that large.
For a USB charger in this class, raising efficiency another percentage point from the 90% level is actually quite difficult. In terms of efficiency, it's only one percentage point, but in terms of power loss, it requires a reduction of nearly 10%. Incidentally, this estimate assumed charging at 30W for 30 minutes per day. In applications that constantly supply tens of watts, the impact of standby power is almost negligible. Power loss during charging and the charger's power conversion efficiency start to matter more.
By the way, we also measured the Belkin charger's efficiency. The vertical axis shows the charger's power conversion efficiency. The higher this number, the better it performs as a charger. Maximum efficiency was 91.4% at 20V output. Chargers in this class often have efficiencies in the 91–92% range, so Belkin's results are fair to good. There is no disadvantage in efficiency from lowering standby power, so you can rest assured about that.
We also measured the charger's temperature using thermography. The maximum temperature is about 65°C, a standard temperature rise for a recent USB charger. We also measured whether thermal throttling occurs. Thermal throttling intentionally lowers the available output power to prevent the USB charger from becoming too hot. With this setup, we continuously draw the power available from the USB charger.
Here are the experimental results. The horizontal axis is the time elapsed since the start of the experiment. The left vertical axis is the USB charger's surface temperature, and the right vertical axis is its output power. Immediately after the experiment starts, it outputs 67W. At the same time, the charger's surface temperature rises. Thermal throttling occurred 20 minutes after the start of the experiment. The surface temperature at this point was 58°C, and output power dropped to 50W. This prevents the surface temperature from becoming too high and protects the circuitry inside the USB charger. The temperature continued to rise afterward, reaching equilibrium at 68°C about two hours after the experiment began. That completes this experiment.
While editing the video, I realized I had missed an important assumption: standby power should also be measured with the USB cable plugged in. Think about actual use. Do you unplug the USB cable after charging is complete? I'm sure many people leave it plugged in. Therefore, I'll measure standby power again with the USB cable connected.
Right now, there is no USB cable plugged into the Belkin charger. We're looking at its standby power, which, as I mentioned earlier, is about 3mW. Now I'll try plugging in a USB cable. The number has increased. Standby power is about ten times higher than with no cable plugged in, at about 30mW. I left it like this for about an hour, but standby power didn't drop. It stayed around this level. I feel like I've seen something I wasn't supposed to see.
Incidentally, this USB cable contains an eMarker chip. Some cables don't contain an eMarker chip. Here's what happens when you connect one of those. This doesn't increase standby power. I see. To sum up, using a USB cable with an eMarker chip prevents it from entering zero standby power mode. Using a USB cable without an eMarker allows it to enter zero standby power mode. Therefore, depending on the cable used, standby power may increase to the same level as other chargers.
I also measured other USB chargers with an eMarker-equipped cable. Here are the results. Belkin's standby power was originally 3.3mW, but plugging in the USB cable increased it about tenfold, to 32.4mW. Perhaps plugging in the cable activates the internal circuitry and takes it out of zero standby power mode. For other chargers that already consumed some standby power, having a cable connected made virtually no difference. This may be because their internal circuitry operates even without a cable. Therefore, if you want to enjoy this charger's zero standby power benefit, I recommend using a cable without an eMarker, like this one, or unplugging the USB cable each time you're done using it.
Next are the advantages and disadvantages of this charger's zero standby power mode. The first advantage is that standby power is reduced to almost zero. At a very small 3mW, it costs only about one yen in electricity even when plugged in all year. The downside is that, depending on the cable you use, it consumes as much standby power as other chargers. I think this is a rather fatal disadvantage. It undermines the product's very concept at a fairly fundamental level.
As for other disadvantages, I haven't found anything in particular during my use. In Amazon reviews, some users report that, depending on the device configuration, it enters zero standby power mode on its own and stops outputting power.
As we've seen so far, standby power per charger isn't a big deal. But when everyone uses chargers, their combined standby power becomes enormous. For example, if a zero standby power mode like this were mandated, the effect of each individual charger would be small, but the overall effect could be very large. I can highly commend the concept of reducing standby power and the attempt made with this charger.
From here, we'll disassemble the charger and see how it reduces standby power. I quickly removed the exterior, and this is what it looks like. This blue object is made of a soft, silicone-like material. I think it's a thermally conductive material intended to thermally couple the components. It isn't simply filled on all sides; this is how the filling looks.
Looking behind the USB ports, there are graphite sheets attached, presumably for heat conduction. However, these graphite sheets aren't in close contact with the components. If you look here, there's a large gap. I'm not sure they're contributing much to heat transfer. It's unclear whether this was intentional or an unintended manufacturing problem.
I took out just the contents. There are four circuit boards: one, two, three, and four. We'll break it down further. With the circuit further disassembled, the circuit configuration is a typical flyback converter power supply. Looking closely at the components, you can see that many semiconductors from the Japanese company Renesas are used. The circuit configuration is almost exactly as shown on this Renesas web page. Let's look at the main semiconductor components.
First, here is the MOSFET. It's a power semiconductor from Transphorm, which Renesas acquired in 2024. This MOSFET has a slightly interesting structure. Internally, a normally-off, low-voltage Si MOSFET and a normally-on GaN HEMT are connected in a cascode configuration, allowing it to be used as a normally-off transistor.
Next to it is Renesas's iW9870 flyback converter controller. I looked it up, and it appears to be a product from Dialog Semiconductor, which Renesas acquired in 2021. On another board is the iW610 secondary-side synchronous rectification controller. This is also made by Renesas.
This component is an Intersil buck-boost controller, from the company acquired by Renesas in 2018. This charger has two USB-C outputs, and this component comes into play when they output different voltages. Finally, here are the iW780 USB PD controllers. There are two of them. These are also made by Renesas. Judging by the product model numbers, they appear to have originally been made by Dialog Semiconductor.
I analyzed why this USB charger's standby power is lower than other chargers. The reason is that this flyback controller IC and the paired PD controller IC optimize the charger's operation when no USB cable is connected, reducing standby power consumption. When no cable is plugged in, the PD controller detects that, and the flyback controller allows the entire circuit to operate in a low-power state. The circuit almost comes to a standstill, so power consumption—in this case, standby power—becomes very low. Of course, if these ICs consume a lot of power in standby mode, that would defeat the purpose, so the ICs themselves must also be designed for low power consumption.
Now that we understand the mechanism for lowering standby power, let's also look at the issue of standby power increasing when a USB cable is plugged in. Looking closely at the datasheet, it says that combining this flyback controller with the PD controller gives standby power below 5mW with no USB cable connected. In other words, even with this IC combination, connecting a USB cable may take it out of zero standby power mode. Mystery solved.
So, that was Belkin's zero standby power USB charger.
I've done a teardown review. The actual measurement of standby power was 3 mW, almost zero on this one.
I also found out that just connecting a USB cable with a built-in eMarker increases standby power to about the same as a typical USB charger.
The concept of reducing standby power is eco-friendly, and it's a very interesting initiative. I hope there will be more USB chargers like this one in the future.
You can find links to the USB charger used today and other recommended USB chargers in the description. If you are interested, please check them out!
If you found this video helpful, please give us a high rating and subscribe to our channel! If you have any concerns, please leave a comment as well! Thank you for watching the video until the end.
Article published · Updated