In high-power fast charging mobile power supply and car charging, it is necessary to use a step-down chip to meet the output needs of 8-24V input and 5-20V, of which the mobile power supply is usually 2 strings or 4 strings of batteries, and the car is charged with 12 to 24V input. Using a boost or buck circuit, it is difficult to meet the input of the full voltage range and the output of the full voltage range, at this time, a step-up and drop circuit is required to automatically control the boost or buck according to the input voltage and output voltage to meet the needs of the equipment.
Zhirong Technology, which is known for its highly integrated power supply SoC, has launched integrated PD and power chips with common fast charging protocols on fast charging mobile power supply and USB PD fast charging, which are very popular in the market and have a very high market share. Zhirong has recently launched a synchronous buck controller SW7203, which is a two-way buck-boost controller that supports charge and discharge management of 1 to 4 lithium batteries, integrated path management NVDC, and supports a maximum output power of 100W.
First, Zhirong SW7203 DEMO introduction
The figure shows the reference design of Zhirong SW7203 synchronous ramp-up and drop-up controller, which has built-in one input detection and two output detection, and the corresponding channel drive, which is designed for PD high-power fast charging, and the MCU with built-in protocol function can form a complete two-way high-power fast charging scheme.
There are no components on the back of the reference design, and the back is a reserved switch tube pad and SW7203 thermal dew copper.
Zhirong SW7203 adopts QFN4*4-32 package, which is small and space-saving. This is a single-inductance four-tube synchronous bidirectional buck-boost charge-discharge controller, support 1-4 lithium battery buck-boost charge and discharge, support 3-19.2V battery voltage range, support 100W charging and output, support 4-24V input voltage, support 3-22V output, input/output and battery terminal current can be set by I2C bus, support feedback and I2C bus to adjust the output voltage, and can switch PSM or PWM operating mode according to the load situation.
The built-in battery charge management supports NVDC power path management, supports dead battery start and battery-free working mode, and has built-in full battery charge cycle management. The chip integrates the NTC detection function inside, which can provide complete high and low temperature protection for the battery and ensure the safety of battery use.
Zhirong SW7203 supports chip overtemperature protection, NTC battery temperature protection, input/output overvoltage protection, battery overvoltage protection, cycle-by-cycle overcurrent protection, charging input undervoltage protection, battery discharge undervoltage protection, discharge output short circuit/overcurrent protection, bus overvoltage protection, charging timeout protection, etc., to ensure the safety of large-capacity battery packs to the greatest extent.
In addition, a high-side driver bootstrap diode is integrated inside the chip, making the peripheral components more streamlined. The chip integrates an internal 5V LDO output to power the microcontroller. The built-in driver output voltage is 5.5V to support logic level MOS and Gallium nitride switch tube applications. The output voltage current parameters can be configured by connecting the I2C bus to the microcontroller, supporting four inductance values of 1μH, 2.2μH, 3.3μH and 4.7μH, and can select 200K, 300K, 400K to 1MHz switching frequencies according to the MOS tube parameters.
The BUCK architecture SW7203 is suitable for fast charging chargers, car chargers, power tools, notebook computers, drones, sweeping robots, walkie-talkie batteries, etc. Flexible buck-boost architecture supports multi-string battery applications to meet the needs of different occasions. At the same time, the built-in perfect protection function can also ensure the safety of the battery to the greatest extent.
Second, Zhirong SW7203 DEMO efficiency test
1, 100W boost output efficiency
The charging head network first tested the battery boost output performance of Zhirong SW7203, using Onzada ASD906A to simulate four string battery packs, simulating the battery in low, half and full power states, Zhirong SW7203 DEMO board fixed 20V5A, 100W output, using Adex IT8511 electronic load for 100W discharge.
The first simulation is the test of low battery power, the input voltage at the end of the board is 12.01V, the input current is 8.688A, the measured output voltage of the board is 19.975V, the output current is 5.002A, and the conversion efficiency of the board is 95.76%.
Then the test of simulating the half-charge of the battery, the board-side input voltage is 14.81V, the input current is 6.953A, the board-side output voltage is 19.978V, the output current is 5.002A, and the board-side conversion efficiency is 97.04%.
When the analog battery is fully charged, the board-side input voltage is 16.41V, the input current is 6.239A, the board-side output voltage is 19.982V, the output current is 5.002A, and the board-side conversion efficiency is 97.62%.
Through the efficiency test, the 100W full-load boost efficiency of the reference design of The Zhirong SW7203 is maintained very well, and the efficiency is still above 95% when simulating the low voltage of the battery, which meets the efficiency requirements of high-power mobile power.
2, 100W buck input efficiency
The following is a 100W input buck test for the analog charging scenario, which uses the output of the analog adapter of the ASCENDA ASD920 high precision CNC power supply, with a fixed input of 20V5A and a 100W output. OnzaxTA ASD906A simulates a four-string battery pack that simulates batteries charging at low, half and full charge.
In the case of simulated battery low charge, the board-side input voltage is 19.796V, the input current is 4.74A, the board-side output voltage is 11.99V, the output current is 7.497A, and the board-side conversion efficiency is 95.80%.
In the case of simulating the half-charge of the battery, the board-side input voltage is 19.793V, the input current is 4.818A, the board-side output voltage is 14.8V, the output current is 6.248A, and the board-side conversion efficiency is 96.97%.
When the analog battery is fully charged, the board-side input voltage is 19.79V, the input current is 4.87A, the board-side output voltage is 16.4V, the output current is 5.727A, and the board-side conversion efficiency is 97.45%.
When the ZHSW7203 DEMO charges the battery with a buck input, even if the battery is in a low-charge state, the system efficiency of the board is still above 95%, and when the battery is fully charged, the efficiency is as high as 97.45%. High efficiency means low heat generation, which is also necessary for the development of 100W high-power mobile power supply or car charging.
3. Efficiency curve
First, let's take a look at the boost output efficiency curve of the Zhirong SW7203 DEMO with 2 string battery packs, 3 string battery packs, and 4 string battery packs:
When the Zhirong SW7203 is paired with two strings of lithium batteries, the efficiency of discharging the battery pack with a 9V voltage is the highest, especially when the output current is between 1-1.5A, and the peak efficiency is more than 97%. When using a 20V voltage output, the overall phase rate is relatively low due to the large voltage difference.
When used with a 3-string battery, the 12V output has the highest efficiency, with a peak value of nearly 98%, and the overall efficiency of the 5V output is slightly lower than other voltage levels.
When the battery voltage is 14.8V, that is, 4 strings of batteries, the overall efficiency of the 12V or 20V output is very high, the maximum efficiency of the 12V output is more than 97.5%, and the efficiency of the 20V output is also more than 97%.
Let's continue to look at the input efficiency curve of Zhirong SW7203:
When charging at 5V voltage, the efficiency of 2 strings of cells is the highest, followed by the efficiency of 3 strings of cells, and the lowest efficiency of 4 strings of cells.
When charged at 9V voltage, the peak efficiency of 2 strings of batteries is between 1-1.5A, the peak efficiency of 3 strings of cells is between 1.5-2.5A, and the peak efficiency of 4 strings of cells is between 2.5-3.5A.
When charging at 12V voltage, the efficiency advantages of 3 strings of cells and 4 strings of cells are obvious, and the peak efficiency is between 1.5-2.5A current, of which the maximum efficiency of 3 strings of cells exceeds 98%.
When charging at 20V voltage, the efficiency of 4 strings of batteries is dominant; when the charging current is between 1.5-5A, the system efficiency is above 97%, suitable for 100W high-power mobile power design.
Charging head net summary
Zhirong Technology has obtained a very high market share in the buck protocol chip and boost mobile power chip, and after the success, Zhirong has exerted its own innovative advantages and continued to launch the SW7203 two-way synchronous booster pressure charge and discharge controller for higher power applications, and marched towards a wide range of battery fast charging market.
At present, multi-string battery packs with high-power fast charging have become the development trend of terminal products, and safe and efficient fast charging has become the constant pursuit of the whole industry. Buck and buck pressure topology, combined with low pressure Gallium nitride switch tube is expected to obtain lower heat, smaller volume, further enhance product competitiveness and experience.