Figure 4. Complete Cell Simulator Schematic
Q101 and T100 are the main flyback elements, with Q102 being the synchronous rectifier. For fast and isolated control of Q102, the gate is driven by T101 via current buffers Q103 and Q104. Feedback is scaled from an auxiliary winding in T100. A 10mΩ series resistor is included at the output so that current sense measurements are possible by taking Kelvin connections to a voltmeter (by use of signals I+ and I-). The total output impedance of the circuit is about 25mΩ and provides a solid ±6A capability. Static losses are about 1 Watt per cell section, so with an array of 24 cells, the likelihood of a 12V supply reversal is minimal and the power level scales well for use with an off-the-shelf 12V/300W supply like the TDK-Lambda SWS300-12.
Building a battery simulator is a practical solution to providing a high density and easily transported BMS development tool. A 24-cell simulator can be packaged in a 2RU rack-mountable chassis complete with a 12V bulk supply, and provide precisely adjustable voltages in the 1.9V to 4.2V range with ±6A capability.