SLUAB19 May   2025 LM25180-Q1 , LM5155-Q1 , SN6507-Q1 , UCC14240-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
    1. 1.1 Low-Voltage Isolated Bias Power Supply
    2. 1.2 High-Voltage Bias Power Supply
  5. 2Centralized Isolated Bias Power Supply Architecture
  6. 3Semi-Distributed Isolated Bias Power Supply Architecture
  7. 4Bias Power Supply Using DC-DC Converter Module
  8. 5Isolated Bias Power Supply Using Gate Driver to Drive the Transformer
  9. 6Redundancy in the Isolated Bias Power Supply Architecture
  10. 7Summary
  11. 8Terminology

1.1 Low-Voltage Isolated Bias Power Supply

Low-voltage bias power supply circuits usually have a 12V battery as a power source in HEVs and EVs. Although there are some systems with 48V as a low-voltage battery, this paper focuses on the 12V battery system. However, these architectures can be still relevant for 48V low-voltage battery designs. In that case, one option is to have a converter to lower the voltage to use the same devices or another option is to have devices supporting an input voltage range designed for a 48V battery.

Considering the state of charge (SOC) of the 12V low-voltage battery, the wider input voltage range needs to be supported by the isolated bias power supply (as an example: 8V–16V). In case of cold crank and load dump scenarios, the input voltage range requirement goes further down and up, respectively. There can be differences in this wide input voltage range of a 12V low-voltage battery depending on the OEM. Not all types of topologies and the associated devices can support this wide input voltage range. Therefore, in several designs a pre-regulator is needed between low-voltage battery and isolated bias power supply to regulate the input voltage for the isolated bias power supply device.

Table 1-1 Texas Instruments Low-Voltage Isolated Bias Supply Topologies and Associated Devices
Parameters Open-Loop LLC Push-Pull Primary-Side-Regulated Flyback Fully-Integrated Modules
(Full Bridge + Transformer)
VIN minimum and maximum 9V, 34V 3V, 36V (1) 4.5V, 65V(1) 4.5V, 26.4V(1)
POUT maximum Up to 9W Up to 7.5W (1) Up to 30W(1) Up to 2.5W(1)
VOUT regulation Unregulated Unregulated, VIN controlled Regulated Regulated
Switching Frequency 0.1–1.2MHz 0.1–2MHz 20–350kHz 11–15MHz
Isolation Depends on transformer used Up to 5kV, basic or reinforced
Supporting Devices UCC25800-Q1 SN6501-Q1
SN6505-Q1
SN6507-Q1		 LM518x-Q1
LM2518x-Q1
LM515x-Q1
LM34xxx-Q1		 UCC1413x-Q1
UCC1414x-Q1
UCC1424x-Q1
UCC1434x-Q1
UCC1524x-Q1
Advantages High efficiency
Low EMI
High CMTI		 Wide Vin range
High line regulation		 High efficiency
Wide Vin range
Highload and line regulation		 No external transformer
Robustness to vibration
Small size and low height
Challenges Requirement of Pre-regulator Low efficiency at low Iout (<50mA) Parasitic capacitance across isolation barrier of flyback transformer Low efficiency
Power limitation
(1) Depends on the variant of the device.