In this architecture, a single-stage bias power supply is used with a bias power supply device directly connected to the low-voltage battery. This connection supports a wide input voltage range and works in a closed-loop operation. This type of architecture can be realized using a single device or multiple devices depending on the power rating. A multiwinding transformer is used to give isolated outputs to the different gate drivers. The low-side gate drivers sharing the same ground can be supplied isolated bias power using the same transformer output winding. As shown in Figure 3-2, a 6-winding transformer can be used to supply isolated power in the AC side. If the transformer design is too complicated with 6-windings, using multiple transformers is also possible with two or three windings in the secondary side to reduce the complexity of the transformer design.

Figure 3-2 Centralized Bias Power Supply Architecture in a Single-Stage OBC With Common-Drain Configuration

The following topologies and associated devices can be used as the preferred choice for the centralized bias power supply architecture:

• Flyback controller: LM5155-Q1, LM5156-Q1, LM515x-Q1, LM3481-Q1
• Flyback converter: LM5180-Q1, LM2518x-Q1
• Push-pull converter: SN6507-Q1

The different topologies for the isolated bias power supply come with certain advantages and trade-offs. A flyback device can help achieve advantages like high efficiency, high load regulation, and high line regulation accuracy for a wide voltage input range. The tightly-coupled flyback transformer design has low leakage inductance, but the trade-off in this design is having a comparatively higher parasitic capacitance across the isolation barrier of the transformer. Appropriate measures in the EMI filter design are sometimes necessary to suppress the EMI and CMTI due to the parasitic capacitance of the transformer. The push-pull device provides good efficiency, high CMTI, lower EMI, and so forth. An extra inductor is needed in the output side to do the duty cycle control for a wide input voltage range operation in push-pull topology.