Patent ID: 7960855

Claim:
A control circuit for an energy storage system comprising a high side power source and a low side power source, the control circuit comprising: (a) a variable gain circuit comprising: (i) an integrator to integrate a current of the high side power source to provide an integrated signal, (ii) a comparison circuit to obtain a comparison signal representative of a comparison of the integrated signal with a reference value of a state of charge of the high side power source, (iii) a gain adjustment circuit to use the comparison signal to provide a variable gain signal, wherein the gain adjustment circuit comprises a variable gain function circuit and a state of charge power limit function, wherein the variable gain function circuit receives the comparison signal from the comparison circuit and applies a variable gain function to the comparison signal to obtain the variable gain signal, and wherein the state of charge power limit function receives the variable gain signal from the variable gain function circuit and applies a limiting function to the variable gain signal; (b) a fixed gain circuit configured to provide a fixed gain signal based on the current of the high side power source; and (c) a power command creation circuit configured to combine the variable gain signal and the fixed gain signal to create a power command to control a power output of the low side power source.