Fast Load Transient Regulation of Low-Voltage Converters with the Low-Voltage Transient Processor

Abstract

The transient response of DC-DC converters with large conversion ratios is limited by the asymmetry of the current slew rate through the magnetic elements; under appropriate control, such a converter may respond much faster to an increase in load current than a decrease, or vice versa. In this paper, a low-voltage, unloaded, bidirectional DC-DC converter with a very fast current slew rate, called the low-voltage transient processor (LVTP), is placed in shunt across the output of a conventional DC-DC converter (the ldquoprimary regulatorrdquo) to equalize the effective current slew rate (the combination of the LVTP and primary regulator) seen at the load, so that the transient response to a load increase is the same as the response to a load decrease. The LVTP operates at very low voltages, enabling the use of small magnetic components with low losses even at high-frequency operation, allowing the overall efficiency of the system to be high. To demonstrate the concept, a 3 MHz bidirectional buck LVTP prototype was implemented and placed at the output of a 12-1.2 V microprocessor voltage regulator (VR). The VR with LVTP matched the performance of VRD10.1 VR reference design with half (4.10 mF) of the output capacitance of the original design.