Block commutation to reduce inverter losses for BLDC drives

A motor control circuit, the circuit comprising:

• a high side (HS) switch and a low side (LS) switch,
• wherein the LS switch is connected in series with the HS switch,
• wherein the LS switch comprises a first body diode and wherein the first body diode comprises an anode and a cathode, and
• wherein the HS switch comprises a second body diode and wherein the second body diode comprises an anode and a cathode;
• a current sensing element, wherein the current sensing element senses a direction of current through the LS switch;
• a rotor sensing element, wherein the rotor sensing element senses a position of a rotor;
• and
• a processing circuit, wherein the processing circuit is configured to:
• control operation of the HS switch and the LS switch;
• receive rotor position information from the rotor sensing element;
• receive direction of current information from the current sensing element;
• determine, based on a position of the rotor, that a motor has reached an end of a commutation step;
• determine, based on the information from the current sensing element, that that current flows in a freewheeling direction through the LS switch, wherein the freewheeling direction is from the anode to the cathode of the first body diode;
• and
• turn on the LS switch in response to determining that a motor has reached an end of the commutation step and that that the current flows in the freewheeling direction through the LS switch.

A system comprising:

• an inverter circuit comprising:
• a high side (HS) switch and a low side (LS) switch,
• wherein the LS switch is connected in series with the HS switch,
• wherein the LS switch comprises a first body diode and wherein the first body diode comprises an anode and a cathode, and
• wherein the HS switch comprises a second body diode and wherein the second body diode comprises an anode and a cathode;
• and
• a current sensing element, wherein the current sensing element senses a direction of current through the LS switch;
• a gate driver circuit, wherein the gate driver circuit controls a first gate for the HS switch and a second gate for the LS switch;
• a rotor sensing element, wherein the rotor sensing element senses a position of a rotor;
• and
• a controller circuit, wherein the controller circuit is configured to:
• control operation of the gate driver circuit;
• receive rotor position information from the rotor sensing element;
• receive direction of current information from the current sensing element;
• determine, based on a position of the rotor, that a motor has reached an end of a commutation step;
• determine, based on the current sensing element, that that current flows in a freewheeling direction through the LS switch, wherein the freewheeling direction is from the anode to the cathode of the first body diode;
• and
• signal the gate driver circuit to turn on the LS switch in response to determining that a motor has reached an end of the commutation step and that that the current flows in the freewheeling direction through the LS switch.