This disclosure describes a control circuit to manage the energy flow for an integrated motor generator (IMG), such as an integrated starter generator (ISG) system. The circuit regulates the output voltage of the IMG when the IMG operates in generator mode. The circuit includes an additional switch for each phase connected in anti-series with the half-bridge circuit for the phase, e.g., the drain of the additional switch connects to the drain of the high-side switch. When the ISG is in generator mode, the additional switches are controlled, e.g., to charge the battery at a constant voltage and current throughout the speed range of the ISG (i.e. high rpm and low rpm). In generator mode, the high-side switches may be turned off, which configures the high-side switches to act as a diode and block battery discharge for low rpm operation when the phase voltages are lower.