D.C. motor bridge coil driver

A method of operating an H-shaped bridge coil driver for a motor coil, for switched bi-lateral coil current flow, and for capturing and reusing switch over lagging coil energy, comprising the steps of:

• establishing a potential equal to the power supply voltage level at a first node of said coil and ground potential at a second other node of said coil during a first time period;
• switching current flow states and establishing a negative potential relative to ground at the first node of said coil, and a positive potential relative to the power supply at the second node of said coil, during a short second time period occurring after said switching;
• establishing a ground potential at the first node of said coil and the power supply potential at the second node of said coil in a third time period occurring after said second short time period;
• further switching current flow states and establishing a positive potential relative to the power supply at the first node of said coil, and a negative potential relative to ground at the second node of said coil, during a short fourth time period occurring after said further switching;
• and
• re-establishing power supply potential at the first node of said coil and ground potential at the second node at the second node of said coil during a fifth time period occurring after said fourth short time period.

An H-shaped bridge circuit for bi-laterally driving a field coil in an electronically commutated brushless D.C. motor, under the control of signals from the motor controller, said H-shaped coil driver bridge circuit being connectable to a power supply, to ground, and to a first and a second coil nodes, and having side legs with series leg segments each containing a switch, the coil being connectable as the cross leg of the H shape between the side leg mid-points, comprising:

• a first diagonal cross coordinated operation switch pair formed from the leg segment switches and thereby being connectable to both said coil node connections, to said power supply connection, and to said ground connection, for providing a first current flow path from said power supply connection through said coil nodes connection to said ground connection in a first direction;
• a second diagonal cross coordinated operation switch pair formed from other of the leg segment switches and thereby being connectable to both said coil node connections, to said power supply connection, and to said ground connection, for providing a second current flow path from said power supply connection through said coil nodes connection to said ground connection in a second direction;
• wherein said first switch pair and second switch pair are each connectable to said control signals thereby being controlled to have said switch pairs conducting alternately, wherein said first direction current flow causes current to flow through said connectable coil in a first direction and said second direction current flow causes current to flow through said connectable coil in a second opposite direction, thereby providing bilaterally changing coil current states;
• alternate circuit means for permitting lagging excess energy in said connectable coil to flow after a change of coil current state thereby providing a transition current flow through said coil continuing in the previous direction, said alternate circuit means including a voltage storage element which charges as said transition current flows to a voltage level in excess of the power supply;
• and current flow path means for discharging the excess voltage stored in said storage means back to the power supply;
• and
• wherein power is not drawn from said power supply while said storage means is discharging back into the power supply.

An H-shaped bridge coil driver, for bilaterally applying excitation power from a power supply connection to a motor field coil connection and then to a ground connection, thereby causing current to flow therethrough alternating in direction, said coil driver being operable for a brushless electronically commutated D.C. motor, under the operation of control signals, comprising:

• a first and second coil node connections;
• a first series connected first and second diodes connected at one end of said series to a ground connection and at their intermediate point to said first coil node;
• a second series connected third and fourth diodes connected at one end of said series to said ground connection and at their intermediate point to said second coil node;
• a capacitor connected to each of said first and second series connected diode pairs free ends on one side thereof and to said ground connection on the other side thereof;
• a first resistor connected to said diode connection side of said capacitor;
• a fifth diode connected between said resistor free end and said power supply connection;
• a first power stage transistor switch connected to conduct between said first coil node and said first resistor to fifth diode connection point;
• a second power stage transistor switch connected to conduct between said second coil node and said first resistor to fifth diode connection point;
• a third power stage transistor switch connected to conduct between said first coil node and a second resistor, said second resistor being connected on its free end to said ground connection;
• a fourth power stage transistor switch connected to conduct between said second coil node and said second resistor;
• a fifth trigger switch transistor connected to conduct between the gate node of said third transistor and said ground connection;
• a sixth trigger switch transistor connected to conduct between the gate node of said fourth transistor and said ground connection;
• wherein said fifth and sixth transistors are connectable to be gated by alternated positive and negative voltage input control signals rendering said fifth and sixth transistors in alternating opposite states;
• a seventh triggering transistor connected to conduct between said power supply connection and the gate node of said first transistor;
• an eighth triggering transistor connected to conduct between said power supply connection and the gate node of said second transistor;
• and
• wherein the gate node of said seventh transistor is connected to the gate node of said fourth transistor, and wherein the gate node of said eighth transistor is connected to the gate node of said third transistor.