Several things. First, quick charge is used with devices like smart phones and tablet computers, while extreme fast charging (XFC) is used with electric vehicles (EVs). Quick charge (QC) is generally slower than extreme fast charge. QC has competitors like universal serial bus power delivery (USB-PD), IEC 62680-1-2:2022, and USB extended power range (EPR). Tesla superchargers are competitors for XFC. This FAQ will review and compare the development and capabilities of QC technologies for mobile devices and XFC for EVs.
QC was initially developed by Qualcomm and is currently up to version 5.0. Initially, Qualcomm QC was “the only game in town” for fast-charging mobile devices. As Qualcomm introduced the various versions of QC, there were parallel efforts by the USB implementers forum to develop QC technologies.
Qualcomm Quick Charge
While alternatives have been developed, Qualcomm QC remains the most popular fast-charging standard. It works with Qualcomm’s Snapdragon processors for mobile devices. But fast charging is not available on all smartphones with a Snapdragon chipset. QC 5.0’s (QC5) popularity is supported by the fact that it’s backward compatible with all previous QC solutions from Qualcomm and works with USB-PD and Apple iPhone 8 and above models (Figure 1).
Qualcomm QC5 can charge devices up to four times faster than the previous generation of QC. In addition, it has eight levels of voltage protection, three levels of current protection, three levels of thermal protection, and three levels of timer protection, including USB-input overvoltage protection at 25 V and external power controls beyond 30 V. Qualcomm Dual Charge is enabled by including a second power management in the device being charged. With the additional control, Dual Charge supports lower power while maintaining charging speeds and lowers power dissipation.
Charging a device via Dual Charge divides the power, allowing for lower power and thermal dissipation. QC5 also includes adaptive input voltage, intelligent negotiation (INOV4) technology, and Qualcomm’s smart identification of adapter capabilities technology. When using Dual Charge technology QC can charge devices up to 50% in five minutes using up to 100W of charging power. QC 5 can be up to 70 percent more efficient compared to previous versions.
USB ports are ubiquitous making the development of USB-PD an important event. Devices like smartphones and tablet computers use USB for data transfer as well as for battery charging. The USB-PD specification supports power flow in both directions and increased power levels up to 240 W.
More stringent power negotiation protocols are used to safely support the increased power levels. In the new extended power range (EPR) mode, negotiation of EPR operation only begins when both devices first agree on a standard power range (SPR) connection. Both devices must continue to communicate with each other during the negotiation. If the sink is muted, the source immediately switches off EPR and starts a new negotiation at 5 volts. Some of the features of USB-PD 3.1 include (Table 1):
- Three new fixed voltages including 28 V for power above 100 W, 36 V for power above 140 W, and 48 V for power above 180 W.
- An adjustable voltage mode that supports three ranges from 15 V up to 28 V, 36 V or 48 V, with 100 mV adjustment steps.
- EPR was developed to enable higher power levels without increasing the current draw, enabling the use of existing USB cables.
The IEC 62680-1-2:2022 specification defines all elements of a USB system including: Hosts, Devices, Hubs, Chargers and cable assemblies. It’s the sixth edition and replaces the fifth edition published in 2021. EPR including Adjustable Voltage Supply (AVS) has been added. IEC 62680-1-2:2022 is the formal USB-IF USB-PD Specification Revision 3.1, Version 1.1. This IEC specification describes the architecture, protocols, power supply operation, connectors, and cabling required for USB-PD at up to 100W.
Some implementation adjustments are required when using EPR. For example, different capacitors are required in the plugs to control any arcing that can occur and protect the contacts when the connector is disconnected under voltage. EPR cables have a different electric tag that identifies them as capable of handling up to 50 V. Without the correct tag, current is limited to a maximum of 3 A. when fast charging single cell devices like smartphones, the charger offloads the charging management from the device. Since Li-ion charging is not linear from 80 to 100 percent, the charger controls the dynamic power delivery as needed by the charging curve, simplifying the charging electronics in the device.
XFC and other EV charging schemes
Like QC5 and USB-PD 3.1, XFC supports faster charging using higher charging voltages. There are several EV charging classifications in Europe and North America based on charging levels and voltages, charging modes, wiring cases, and connector types.
IEC 61851-1 is used in Europe and defines four modes of EV charging:
- Mode 1 charging is low power and uses a simple cable plugged directly into an AC outlet.
- Mode 2 also plugs directly into an AC outlet and adds integrated protection to support safe charging up to about 15 kW with three-phase power.
- Mode 3 fast charging uses a dedicated charging station to deliver up to 120 kW AC. Under IEC 61851-1, Modes 1, 2, and 3 all rely on the EV’s onboard charger to control battery charging.
- Mode 4 is DC fast charging, and the EV’s onboard charger is bypassed with the power delivered directly to the battery pack. Mode 4 can deliver several hundred kilowatts of power to the battery pack and requires the use of a high-level communication protocol to ensure safe battery charging.
The SAE J1772 standard in North America defines three charging levels:
- Level 1 uses single-phase 120 V AC power and is limited to about 1.9 kW. It’s mostly intended for overnight or long-term charging.
- Level 2 uses three-phase 208 or 240 V AC power. It’s sometimes called “fast AC charging” and can deliver up to about 19 kW from a 240 Vac input. Levels 1 and 2 require the use of an onboard EV charger.
- Level 3 is called DC fast charging and uses an external DC charger to deliver 600 V DC or more directly to the EV battery pack, bypassing the internal battery charger. Current DC fast chargers can deliver up to 400 A for a total power of 240 kW. Advanced XFC chargers are being developed to deliver 1 kVdc at up to 500 A for a total power of 500 kW.
Level 3 and Mode 4 XFC charging technologies use DC to deliver higher power levels and are emerging technologies. Initially, these chargers delivered 400 V to match the voltage of the EV battery packs. For example, a basic Level 3 charger can deliver about 50 kW, and it takes about 80 minutes to charge a battery for a travel range of 400 km. Connectors and cabling are key limitations for deploying XFC technology for EVs. Existing connectors can handle a continuous current up to 200 A, limiting the charging power with a 400 V system to 80 kW and requiring a charge time of about 50 minutes to support a travel range of 400 km. A key for faster EV charging is higher voltage EV battery packs. EVs are already appearing with 800 V packs, and 1 kV packs are on the horizon. Another requirement is liquid-cooled connectors capable of handling currents up to 350 A. Liquid-cooled connectors are already available and can support a travel range of 400 km in about 11 minutes; close to the time needed to fill the tank with gasoline for vehicles using internal combustion engines (Figure 2).
QC and XFC are similar in that both rely on higher voltages to enable faster battery charging. QC is a well-established technology designed for use with portable electronics like smartphones, tablets, and notebook computers. XFC is a still emerging and developing technology for EVs and is expected to make EV charging comparable in terms of time with filling the fuel tank of an ICE-powered vehicle. QC is governed by the same standards from Qualcomm, USB-IF, and IEC on a global basis. XFC is governed by SAE standards in North America and IEC standards in Europe.
Car Charger Stations application examples, Semikron Danfoss
IEC 61851-1 Ed. 3.0 b:2017 Electric Vehicle Conductive Charging System – Part 1: General Requirements, International Electrotechnical Commission
IEC 62680-1-2:2022, International Electrotechnical Commission
Qualcomm Quick Charge 5, Qualcomm
SAE Electric Vehicle and Plug in Hybrid Electric Vehicle Conductive Charge Coupler J1772_201710, SAE
USB Charger (USB Power Delivery), USB-IF
USB Power Delivery Specification, USB-IF
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