Bidirectional DC-DC Converter Reference Design for 12-V/48-V Automotive Systems
Created: Apr 19, 2018
The TIDA-01168 reference design is a four-phase, bidirectional DC-DC converter development platform for 12-V/48-V automotive systems. The system uses two LM5170-Q1 current controllers and a TMS320F28027F microcontroller (MCU) for the power stage control. LM5170-Q1 subsystems use average current feedback for current control whereas the C2000™ microcontroller provides voltage feedback. Such a control scheme eliminates phase current balancing typical for multiphase converters. A system based on LM5170-Q1 allows a high level of integration, which reduces printed-circuit board (PCB) area, simplifies design, and speeds up development.
A bidirectional DC-DC converter applies in efficient electrical energy transfer and storage applications. A
typical system uses two batteries, battery and motor-generator, or a combination of both (see Figure 1).
Lithium-Ion (Li-Ion) or Lithium-Polymer (Li-Pol) technology provides the best performance. Alternatively,
lead-acid batteries (Pb) are used for high-capacity and low-cost energy storage.
For this reason, operating voltage on the power rails does not significantly change. The charge and discharge process of the cells affects slow voltage changes whereas the internal series resistance, Ri , causes short voltage transients. Consequently, the current control loop performance is more important than the voltage loop. The TIDA-01168 uses the LM5170-Q1, which is a bidirectional, switched-mode current controller. In this case, the DC-DC converter operates more as an ideal current source with variable direction. This configuration allows energy transfer between two voltage domains. The microcontroller-based voltage feedback only maintains output voltage within the acceptable operating range and eventually allows a custom charging profile for the battery pack.