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The "killer feature" behind high-power fast charging-charge pump IC

Release on : Nov 29, 2021

The "killer feature" behind high-power fast charging-charge pump IC
Charge pump IC
With the development of electronic equipment toward intelligence and multi-function, the power consumption of equipment has increased significantly, and the market's demand for fast charging has become stronger. The current fast charging products on the market mainly increase the charging power and shorten the charging time by increasing the charging current/voltage.

The basis of high-power charging is that the battery itself can accept high-power charging. With the continuous development of input power to 60W, 90W, 100W and other high-power directions, the input voltage, which was originally only 5V, has also begun to increase toward 10V and 20V. When the battery input voltage is increased to not match the battery charging voltage , It is necessary to step down the input voltage. If you want to ensure that the charging power is not affected, you need to add charge pump technology before the battery charging input terminal to meet the requirements of high-power charging. Take the 20V/6A 120W input power supply as an example. By connecting two sets of charge pump circuits in parallel at the front of the battery, the input voltage can be reduced by 50% and the input current can be increased by 100%, realizing 10V/12A voltage and current conversion. The addition not only reduces the charging voltage of the battery, but also ensures the high-power energy input. At present, charge pump technology is used in products of domestic first-line brands such as Huawei, Xiaomi, and Honor. Among them, in addition to international major manufacturers such as TI, ADI, and NPX for charge pump chips, domestic Nanxin and Volta chips in this area have also been mass-produced, and several solutions have been introduced, with the highest battery charging efficiency reaching 99.2. %.

Southchip Semiconductor

In 2019, Nanxin released the first domestic 40W high-voltage charge pump charging IC SC8551, which officially entered the high-power consumer electronic fast charging market. With the advantage of the domestic first launch, it quickly established a foothold in the domestic fast charging market.

Nanxin's current product line covers charge pump ICs, PD protocol buck-boost PMICs, AMOLED control ICs, and wireless charging ICs. The development of multi-threading has increased the penetration rate of its own products in the market. Nowadays, Apple-led mobile phone manufacturers have responded to the call for environmental protection and cancelled the mobile phone chargers that came with it. The market demand for chargers has risen sharply. As the domestic fast-charging leader, Nanxin may receive huge dividends from it.

In September of this year, Nanxin once again released the charge pump charging IC SC8571 that integrates multiple charging protocols. In the case of single-chip applications, it can meet the charging requirements of up to 120W.

SC8571 adopts Nanxin's second-generation charge pump technology, which is an ultra-high voltage 4:2 charge pump IC, featuring high efficiency, multi-mode, and fast charging. It is mainly used in the solution of dual series battery cells. In the application of 120W and below power, only one SC8571 is required. In 120W to 160W applications, two SC8571 parallel solutions can be used. With three parallel connection, the charging power of up to 200W can be achieved.


4: 2 charging efficiency curve in charge pump mode. Source: Southchip Semiconductor

The figure above shows the charging efficiency curve of the SC8571 IC in the 4:2 charge pump mode with a working voltage of 10V as a function of current (the horizontal represents the current value and the vertical represents the efficiency). From the above figure, it can be seen intuitively that the highest operating current of the chip is 12A, and the highest output power is 120W. At 3A, the charging efficiency reaches a peak value of 98.65%. Under the condition of an operating current of 8A, the charging efficiency can still be Keep it above 98%.


2:2 Charging efficiency curve in direct charge mode. Source: Southchip Semiconductor

The above figure shows the charging efficiency change curve of SC8571 IC in 2:2 direct charging mode. When the output current is 1A to 6A close to 7A, the charging efficiency can be stably maintained above 99%. In the 1A state, the charging efficiency reaches a peak of about 99.7%.

The 4:2 charge pump mode of SC8571 and two batteries connected in series are one of the high-power fast charging solutions with the largest charging power and the highest charging efficiency.

Vodafone Semiconductor

Volta Semiconductor released the first domestic charge pump chip NU2205 for dual-cell 4:2 fast charging in July this year. The maximum charging power of the charge pump chip has been increased to 120W, breaking the traditional single-cell charging power of less than one hundred watts. At the same time, Vodafone Semiconductor is continuously increasing the charging power to meet the needs of more application scenarios.

For charging, high efficiency is very important. For this reason, Vodafone Semiconductor optimizes the internal and integrated FETs of the NU2205 chip to increase the operating frequency and achieve high efficiency. In addition, the charging mode can be adjusted according to the charging state and temperature of the battery to reduce switching losses, reduce the heat generation of the system, and ensure the safety of the charging process.

Source: Vodafone Semiconductor

NU2205 has two working modes: 4:2 charge pump and ordinary direct charge. The above picture shows the efficiency change curve of NU2205 with current changes in 4:2 working mode. Through the efficiency curve, it can be seen that the charging efficiency reaches 98.2% in this mode, and the charging current can be 10A higher. In this mode, the charge pump reduces the output voltage to half of the input voltage, and guarantees the constant charging power by increasing the current. In this mode, not only the transmission current of the charging cable is reduced, but also the problem that the charging cable is prone to heat when encountering high currents is alleviated. In the normal direct charge 2:2 mode, the highest charging efficiency of NU2205 can reach 99.2%.

According to Volta Semiconductor, the NU2205 can increase the charging power by paralleling charge pump chips, and the charging power of three chips in parallel can be increased to more than 200W.