High voltage sampling scheme independent of capacitor voltage coefficient for a delta sigma modulator

Abstract

The rapidly growing market of electric vehicles has motivated the research for safe and effective monitoring of large battery packs. This paper presents a unique sampling scheme for a delta sigma modulator that is independent of common mode voltage. The rejection of common mode voltage is important in the application of electric vehicles and other large battery packs in order to accurately measure every cell on the stack with varying common mode voltages. A switched capacitor implementation is the proposed solution, and simulations in Cadence provide the results. The simulations of the circuit supported the claim that it is independent of common mode voltage. The tradeoffs include degradation over temperature and signal level. The new topology also introduces the possibility of a less complex input bias cancellation circuit that can be researched in the future.