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Everything you need to know about Qualcomm Quick Charge

Everything you need to know about Qualcomm Quick Charge

20 Nov 2020


When we use a power adapter that supports PD or QC fast charging protocol to charge digital devices, you may not realize how long the fast charging standard has gone through.



Understanding Fast Charging

The contradiction between computing performance and improvement and the stagnation of battery technology has long been the original demand of digital product users (especially smart phone users) for fast charging and wireless charging. The former can shorten the charging time, and the latter can use fragmented time for The phone replenishes the battery. Both fast charging and wireless charging can improve charging efficiency, but Qi has always been the leader in wireless charging standards, but it is difficult to have a unified fast charging standard.


What to know about Qualcomm Quick Charge?

Qualcomm QC is the first to form a third-party fast charging agreement, and therefore become the most influential one among all fast charging standards. Why? As one of the manufacturer, Qualcomm is the first one to notice the potential fast charging demand of smartphones. With the help of the first-mover advantage of Snapdragon SoC, it has launched and gradually improved the QC fast charging protocol since 2013, and become one of the players that cannot be ignored in the fast charging field today.


Quick Charge 1.0

After completing the acquisition of Summit Microelectronics in January 2012, Qualcomm launched the first version of the QC fast charging protocol-QC 1.0 in 2013.

Generally speaking, the USB-DCP protocol released by USB-IF (USB Implementers Forum, a non-profit USB standard-making organization) specifies that the input current of the Micro-USB interface is 1.5A, rather than the QC 1.0 fast charge standard introduced by Qualcomm 2A. At that time, the current transmission limit of the 5-pin Micro-USB commonly equipped with Android models is 2A, and the industry consensus is to reserve a certain margin to ensure charging safety, so the normal charging current of most models is 1.5A. The power is 7.5W (5V 1.5A). And QC 1.0 simply raises the charging current to 2A, which increases the charging efficiency of the smartphone by 1/3 on the basis of 7.5W.


With the increasing demand for fast charging of smart phones, QC 1.0 ushered in an upgrade in 2014.


Quick Charge 2.0

Micro-USB's 2A current transfer upper limit means that Qualcomm can no longer achieve higher power charging by increasing the current, so Qualcomm has no choice but providing charging power by increasing the input voltage .  Taking QC 2.0 as a case, which increases the input voltage of the mobile phone to 4 gears. In addition to the standard voltage of 5V, it also increases the fast charging voltage of 9V, 12V, and 20V. With 2A upper limit current of Micro-USB, its maximum charging power can reach 40W theoretically.


 


QC 2.0 has its exclusive charging adapter. To ensure the adapter supports 5V devices downwards, Qualcomm has introduced a handshake protocol in the QC 2.0 protocol.The handshake protocol of QC 2.0 communicates through the DP (D+, Digital Positive) and DM (D-, Digital Minus) two-pin data terminals of the Micro-USB / USB-A / USB-C interface, and the smartphone actively sends to the QC2.0 charger Apply for a high voltage input, and after confirmation, the maximum charging voltage of the adapter to the mobile phone can be increased to 20V.


QC2.0, which must use a special charger, has become a life-saving straw for the upstream and foundry industries. Since then, the fast-charging industry has started explosive growth.


The VOOC flash charge used by OPPO in Find 7 is actually a modification of the Micro-USB interface, increasing the Pin to 7 pins, and the additional two contact pins are used to transmit current. Therefore, Find 7 must have a dedicated VOOC flash charger and charging cable.


Although the charging power has soared from 10W of QC 1.0 to 40W, QC 2.0 is actually still very primitive.


Since the actual acceptable charging voltage of the lithium-ion battery inside the mobile phone is 4.35V (the charging voltage of the lithium-ion battery of a small number of mobile phones is 4.2V and 4.4V), in fact, whether the input voltage of the USB interface of the mobile phone is 5V or 20V, The mobile phone must be equipped with a step-down circuit to reduce the input voltage to 4.35V. However, the 4.35V step-down conversion of the 20V voltage inside the mobile phone will generate a lot of heat, causing the mobile phone to charge too high temperature, which is extremely prone to explosion risk.


Therefore, in 2015 Qualcomm released a more mature QC 3.0 agreement.


Quick Charge 3.0

In the QC 3.0 protocol, Qualcomm uses the INOV voltage management algorithm and mechanism (Intelligent Negotiation for Optimum Voltage, intelligent negotiation for optimal voltage), starting from 3.6V, combining real-time voltage, current, and battery temperature, INOV can maintain the Communication, adaptively increase and decrease voltage with 200mV amplitude modulation step, automatically realize the transmission of the best charging power.


On the basis of the existing QC 3.0, Qualcomm released QC 4.0 in November 2016, and only 7 months later, in June 2017, it quickly updated to QC 4+.


The first-released QC4.0 uses a more refined INOV mechanism, the amplitude modulation step is adjusted from QC3.0's 200mV to 20mV, and it supports Dual Charge technology, which increases the charging speed by 20% and the charging efficiency by 30%. The key point is that QC 4.0 began to support the USB-C interface and USB PD protocol.


Quick Charge 4.0

The QC 4+ protocol that the upgrade of QC 4.0 has undergone larger and substantial updates, including:


  • Dual Charge: Supports an additional power management chip, higher charging voltage conversion efficiency and faster charging speed
  • Intelligent heat balance: Optimize Dual Charge, automatically allocate current paths, and optimize power delivery
  • Advanced security function: monitor the temperature of the device adapter and port at the same time to prevent the line from overheating and short circuit, and avoid damaging the USB-C interface

At this point, QC has developed to its current mature stage. In the process of QC development, the PD agreement is also gradually improving.



As early as July 2012, USB-IF has released the USB PD (USB Power Delivery) 1.0 power supply specification based on the universal USB-A and USB-B interfaces at that time, describing the USB 3.0 and USB 2.0 interfaces up to The beautiful imagination of 100W power supply capability, but it was not until the emergence of the USB-C interface that this imagination began to become a reality.


In 2014, when Qualcomm QC 2.0 was released, USB-IF also released the PD 2.0 protocol and its carrier, the USB Type-C 1.0 interface standard. Compared with Micro-USB, the USB-C (USB Type-C) interface supports up to 20V 5A power transmission, which is naturally more suitable for fast charging. However, since the USB-C interface is not the mainstream interface of smart phones at this time, the third-party fast charging protocol led by Qualcomm QC protocol is still the mainstream of the market. Even when USB-IF released the PD 3.0 protocol optimized based on the PD 2.0 protocol in February 2017, the situation where various third-party fast charging protocols occupied the king's place did not significantly improve.


It was not until the USB-IF released the PPS (Programmable Power Supply) specification of the USB PD 3.0 protocol in May 2017 that it finally marked the final unification of the fast charging standard.


Conclusion

The PPS specification which support for the two fast charging methods of high voltage and low current and low voltage and high current has been added. At the same time, the INOV of QC 4+ has introduced a 20mV amplitude modulation step adaptive voltage adjustment mechanism. However, this is not all of PPS. The most influential point in the PPS specification is that USB-IF uses its own rule maker's identity to forcibly define that the USB interface does not allow voltage adjustment with protocols other than USB PD. At the same time, USB-IF Allow third-party fast charging protocols to continue to exist by a way of USB PD compatibility. This killer feature means that USB-IF only gives the third-party fast charge protocol two choices: death or being incorporated.


The charging stage of fast charging can be divided into constant current precharging (small current), constant current fast charging (large current), constant voltage charging (current from large to small until charging is completed), whether it is high voltage or low current (QC belongs to this category) ) Or low voltage and high current, it is necessary to adjust the input voltage of the power adapter through the USB-C interface. Therefore, the PPS specification announced the prohibition of third-party fast charging protocols that are not compatible with the PD protocol to adjust the USB voltage authority, which is undoubtedly the final message to Qualcomm.


However, USB-IF has not blocked the way for all third-party fast charging protocols. As long as the USB PDs "fiat currency" status is recognized and accepted, the third-party fast charging protocol can still imitate Apple's MFi in its own small kingdom to provide accessory manufacturers (Or users?) Charge licensing fees.


 
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