Adaptive power control for two-stage AC/DC or DC/DC isolated power converters

A two-stage variable-link-voltage converter comprising:

• a Power-Factor Converter (PFC) having an Alternating Current (AC) input and an output driving a Direct Current (DC) link capacitor that generates a DC link voltage;
• a Dual Active Bridge (DAB) converter that receives the DC link voltage from the DC link capacitor and generates an output having a battery voltage and a battery current;
• a PFC controller that generates Pulse-Width-Modulation (PWM) control signals to transistors in the PFC;
• a DAB controller that generates primary control signals to primary transistors in a primary side of the DAB converter, and that generates secondary control signals to secondary transistors in a secondary side of the DAB converter, wherein the primary side and the secondary side are connected at a transformer;
• a divider that receives a reference power constant that represents a constant value of output power of the battery voltage and the battery current, the divider dividing the reference power constant by the battery voltage to generate a battery current reference that varies with the battery voltage;
• a multiplier that multiplies the battery current reference by a constant to generate a link reference that varies with the battery voltage;
• a first comparator that compares the DC link voltage to the link reference to generate a first modulation factor applied to the PFC controller;
• wherein the first modulation factor causes the PFC controller to modulate the PWM control signals to transistors in the PFC in response to changes in the DC link voltage and to changes in the battery voltage;
• a first limiter that limits the battery current reference to a maximum battery current limit;
• and
• a Constant-Power/Constant-Current (CP/CC) comparator that compares the battery current to the battery current reference to generate a CP/CC modulation factor;
• wherein the CP/CC modulation factor modulates a phase difference between the primary control signals and the secondary control signals generated by the DAB controller when the CP/CC modulation factor is applied to the DAB controller during a CP mode when power is held constant and during a CC mode when the battery current is held constant;
• whereby the PFC controller modulates the DC link voltage in response to the first modulation factor that is generated by dividing the reference power constant by the battery voltage from the DAB converter and multiplying by the constant and comparing to the DC link voltage.