Get the fast charging design of portable lithium battery pack

With the rapid development of portable products, the use of various batteries has increased greatly. Beineng International Co., Ltd. has introduced a portable Lithium Battery Pack charging management fast charging reference design. This reference design uses Microchip's MCP19118 as the control chip, Infineon's 5th generation OptiMOS for power conversion, fast and high current charge management for portable lithium battery packs, few peripheral components, high electrical conversion efficiency, low ripple current, protection function perfect.


The control chip MCP19118 is a digital enhanced power analog controller with synchronous driver. It integrates an analog PWM controller and an 8-bit MCU. It has the fast dynamic response of analog devices, as well as flexible charging curves and various functions. The 5th generation OptiMOS has a smaller Rdson, a smaller parasitic capacitance, and a smaller Trr of the parasitic diode. It is more suitable for high-frequency PWM power conversion circuits, which greatly contributes to the improvement of overall performance.


Block diagram:


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Schematic:

2.png


Physical map:


3.png


Features:

  •  High-current charge management for multi-cell series lithium batteries

  • In standby mode, the output voltage can be supplied, and the battery pack can determine whether the charger is suitable.

  •  Insert the battery, no inrush current will be generated, the charger will automatically detect the battery and automatically start charging.

  •  Can implement a variety of protection functions, such as input voltage undervoltage and overvoltage protection, output overcurrent protection, temperature protection, etc.


Electrical parameters:

  • Input voltage: 32Vdc

  •  Load: 6-string lithium battery pack

  •  Constant voltage charging voltage: 26.1V (6S, 4.35V per section)

  •  Constant current charging flow: 10A max

  •  Pre-charge voltage: 18V; pre-charge flow: 1A; stop charge flow: 0.5A

  •  Output current ripple: <200mA@IOUT = 10A

  •  Switching frequency: 300KHz

  •  Efficiency: >97% max


Target application:

  •  Battery fast charging


Part number:

  • MCP19118 *1

  • MCP6072 *1

  • MIC5233*1

  • BSC032N04LS *2

  • BSC030P03NS3 *1


Chip introduction


The MCP19118 features a digitally enhanced power analog controller with integrated synchronous drivers that integrates an analog PWM controller with an 8-bit MCU.


Analog PWM controller features:

  •  Input voltage range: 4.5~ 40V

  •  Switching frequency: 100 kHz~1.6 MHz

  • Static current: 5 mA

  •  High-end driver: +5V, 1A/2A sink current, 1A/2A sink current

  •  Low-end drive: +5V, 2A sink current, 4A sink current

  •  Peak current mode control

  •  Output differential sampling

  • Multi-output system: master/slave, frequency synchronization

  •  Parameter configurable

  •  Thermal shutdown

ï‚· 4.png

8-bit MCU features:

  •  Precision 8MHz internal oscillator

  •  4096 on-chip program memory

  •  256 bytes of RAM

  • 11 I/O pins and one input only pin

  •  External 8-channel 10-bit precision AD conversion

  •  2 8-bit timers and 1 16-bit timer

  • I2C communication interface

  •  Package: 24-pin 4 mm x 4 mm QFN


working condition


1, efficiency curve


5.png


2, inductor current waveform and drive waveform


Note: Power inductor current waveform and high and low end MOS tube drive waveform. Where: 1 yellow: high-end drive waveform; 4 green: low-end drive waveform; 3 purple: inductor current


1) The waveform at low current when starting, the low-side drive is turned off when the inductor current approaches zero.


6.png


2) Waveform at 4A. High-end drivers operate well at duty cycles >50% due to ramp compensation; low-side drivers turn off when the inductor current approaches zero. The picture on the right is an expanded view.



7.png


8.png


3) Waveform at 7A. When the duty cycle is >50%, the high-end driver works well due to the ramp compensation; the low-side driver is basically complementary to the high-end driver except the dead time. The picture on the right is an expanded view.


9.png

10.png


4) Waveform at 10A. When the duty cycle is >50%, the high-end driver works well due to the ramp compensation; the low-side driver is basically complementary to the high-end driver except the dead time. The picture on the right is an expanded view.


11.png


12.png


3, the output current waveform


Note: Output current waveform at 4A/7A/10A. Where: 1 yellow: high-end drive waveform; 4 green: low-end drive waveform; 3 purple: output current


1) Waveform at 4A

13.png


2) Waveform at 7A


14.png


3) Waveform at 10A


15.png

When the output current is 4A/7A/10A, the output ripple current is very small.


4, thermal imaging

Note: The output current is 10A, 30 minutes, no wind, room temperature, no other auxiliary heat dissipation.

Q1 (high-end MOS): 94.1 ° C; Q3 (low-end MOS): 88.8 ° C; Q2 (output switch MOS): 72.5 ° C; L1 (power inductor): 89.4 ° C; U2 (control chip): 88.5 ° C


16.png


in conclusion


Lithium-ion batteries have been widely used in more and more portable devices due to their unique performance advantages. It is foreseeable that the future design of lithium-ion battery chargers will be expanded with faster charging rates and more robust system protection. Multiple application areas.

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