3 TI Design

The high-voltage bus uses a flyback converter to convert from the high-voltage bus to 24V as a low-voltage bus. The PMP23580 achieves bidirectional 3.0-4.2VDC to 18-36VDC, with an peak efficiency that can reach 82.3% while charging and 86.2% while discharging. The power supply rail is designed in two paths, with one non-isolated supplying power to the MCU and the other isolated supplying power to the driver circuit for the transistors. The driver circuit uses a combination of PNP and NPN forms to provide drive to the back-to-back MOSFETs in front. At the same time, the circuit can achieve balancing between modules. When discharging or charging one cell in a module, the user must select a corresponding cell in another module for charging or discharging to make sure that the bus voltage remains balanced. The 24V bus can be reused with other bus systems, and TI recommends that the reference for bus voltage control be slightly higher than the actual 24V to verify energy retrieval from other batteries during balancing, preventing energy extraction from the flyback.

Figure 3-1 Discrete ACB System Block Diagram