A Wide Bandwidth Electronic Load

Abstract

Electronic load (E-load) is commonly used to test power supplies. In order to test computer power supplies, the E-load must possess an ideal controlled current source property which draws a desired load current even in the case of a very low terminal voltage of the source under test (SUT). It also needs to have superior dynamic performance to simulate high-slew-rate load transients. This paper proposes the design of a switching-converter-based E-load with very large operational bandwidth. The overall architecture of the E-load consists of a low-bandwidth converter, which functions under steady state, and a high-bandwidth auxiliary circuit that is only active during transient state. The converter circuit is realized using a novel switched-boost topology, and the auxiliary circuit is realized using a MOSFET operating at the edge of saturation and linear region. The proposed topology is capable of sinking a specific amount of load current even with a very low SUT terminal voltage. Simulation and experimental validations are provided to verify the proposed concepts. A prototype has been built to test the proposed architecture. The operational input voltage (SUT voltage) ranges of the prototype are between 0.5 and 6 V. The load current range is between 0.75 and 7 A. The results validate the excellent dynamic characteristics of the proposed architecture.