Circuit and method for operating a MOSFET control circuit with a system operating voltage greater than a maximum supply voltage limit

A circuit for operating a MOSFET control circuit having a maximum supply voltage limit with a system operating voltage greater than the maximum supply voltage limit, the system operating voltage referenced to a first ground, the circuit comprising:

• a MOSFET control circuit having a power supply input for receiving the system operating voltage and for generating a signal having a maximum voltage level and a minimum voltage level;
• a ground floating circuit connected to the MOSFET control circuit for providing a second ground having a greater potential than the first ground for establishing a voltage difference between the MOSFET control circuit power supply input and the second ground, the voltage difference being less than the maximum supply voltage limit;
• and
• a first signal level shifting circuit for receiving the signal having the minimum voltage level reference to the second ground voltage and producing a MOSFET activation signal having a minimum voltage level referenced to the first ground voltage.

A method for operating a MOSFET control circuit, having a maximum supply voltage limit, with a system operating voltage greater than the maximum supply voltage limit, the system operating voltage referenced to a first ground, comprising the steps of:

• providing a MOSFET control circuit having a power supply input for receiving the system operating voltage and for generating a signal having a maximum voltage level and a minimum voltage level;
• establishing a voltage difference with a ground floating circuit including a second ground having a greater potential than the first ground between the MOSFET control circuit power supply input and the second ground, the voltage difference being less than the maximum supply voltage limit;
• and
• shifting one of the maximum voltage level and the minimum voltage level of the signal from a first reference voltage related to a second ground voltage to a second reference voltage related to the first ground voltage.