1.1 描述
当今的许多电气设备（例如工业医疗设备、机器人吸尘器、无人机和高功率扬声器）都需要多个电池供电。其中一些设备需要能够实时调整充电电流，以微调设备在不同操作模式下的性能。例如，许多电池制造商要求在不同温度下达到特定的充电电流水平，以保证电池安全。虽然 MP2759 具有 JEITA 来调节充电电流，但微控制器 （MCU） 可以增强用户配置。
此参考设计展示了一种利用来自 MCU 的 PWM 信号实时调整充电电流的方法。此设计基于 MP2759，MP1 是一款高度集成的开关充电器，专为采用 6 节至 <> 节串联锂离子或锂聚合物电池组的应用而设计。
1.2 Features
- Up to 36V Operation Input Voltage
- Up to 3A Charge Current
- 1-Cell to 6-Cell Series with 3.6V, 4.0V, 4.1V, 4.15V, 4.2V, 4.35V, or 4.4V Battery Regulation Voltage for Each Cell
- Input Current Limit Regulation
- Input Minimum Voltage Regulation
- Supports OR Selection Power Path Management
- 0.5% Battery Regulation Voltage Accuracy
- Charge Operation Indicator
- Input Status Indicator
- Battery Over-Voltage Protection (OVP)
- Charging Safety Timer
- Battery Thermal Monitoring and Protection with JEITA Profile
1.3 Applications
- Industrial Medical Equipment
- Power Tools
- Robots and Portable Vacuum Cleaners
- Wireless Speakers
2 Reference Design
2.1 Block Diagram
Figure 1 shows a highly integrated switching charger used for applications with 1-cell to 6-cell series Li-ion or Li-polymer battery packs. This solution offers a 40W output capability, a maximum 36V input voltage, and a charging current that can be adjusted in real time with an external PWM signal.
Figure 1: Block Diagram
2.2 Related Solutions
This reference design is based on the following MPS solutions:
| MPS Integrated Circuit |
Description |
|---|
| MP2759 |
36V switching charger with power path management for 1-cell to 6-cell batteries |
Table 1: System Specifications
2.3 System Specifications
| Parameter |
Specification |
|---|
| Input voltage range |
4V to 36V |
| Output voltage |
Up to 26.4V |
| Maximum output current |
3A |
| Switching frequency |
700kHz or 450kHz (under nominal conditions) |
| Efficiency |
>92% |
Table 2: System Specifications
3 Design
3.1 Design Process
Figure 2 shows the application circuit that can charge multiple batteries. This circuit provides the ability to adjust the charging current in real time with power path management. This circuit’s power stage uses one inductor (L 1 ) and 3 capacitors (C IN , C PMID , and C BATT ). With the addition of external components, the complete charging function with power path management can be realized.
Figure 2: Application Circuit
The MP2759 provides a feature that allows the charging current to be regulated. This is accomplished by connecting a resistor (R ISET ) between the ISET pin and AGND. The voltage on the ISET pin is fixed at about 1.2V. The relationship between RISET and charging current can be calculated with Equation (1) :
ICHG=96(kΩ**)RISET(kΩ**)����=96(�Ω)�����(�Ω)Figure 3 shows the equivalent RISET circuit. It is possible to change the equivalent RISET by modifying the duty cycle of the PWM signal from an MCU. This means that the charging current can be adjusted in real time.
Figure 3: Equivalent RISET Circuit
3.4 PCB Layout
The PCB layout in Figure 5, Figure 6, Figure 7, and Figure 8 refers to the standard MP2759 evaluation board.
Figure 5: Top Layer
Figure 7: Middle Layer 2
Figure 6: Middle Layer 1
Figure 8: Bottom Layer
4 Test Results
4.1 Efficiency
L = 10µH/35mΩ, fSW = 700kHz, RSNS = 20mΩ, and TA = 25°C.
Constant voltage mode
Figure 10: Efficiency vs. Charge Current
4.3 Thermal Measurements
L = 10µH/35mΩ, RSNS = 20mΩ, fSW = 700kHz, TA = 25°C, and burns in 20 minutes. Board information: 63.5mmx63.5mm, 4-layer, 1oz/layer.
VIN = 36V, VBATT = 24V, ICC = 2A,
TRISE = 67.3°C to 25°C = 42.3°C
Figure 27: Thermal Image
VIN = 16V, VBATT = 12V, ICC = 3A,
TRISE = 70.8°C to 25°C = 45.8°C
Figure 28: Thermal Image
0
/6 
工商网监
湘ICP备2023018690号
1358
Figure 5: Top Layer
Figure 7: Middle Layer 2
Figure 6: Middle Layer 1
Figure 8: Bottom Layer
Figure 27: Thermal Image
Figure 28: Thermal Image
淘帖
15
