Energy recovery from a spindle motor using a sequence of a braking phase, an active step-up phase and an active braking phase in response to external power supply failure
The half-bridges driving a multiphase motor are controlled to perform a sequence of operations to support charging a hold capacitor. First, in a brake configuration, the half-bridge transistors are controlled such that either high-side transistors or low-side transistors of the half-bridges are turned on. Second, in an active step-up configuration, the half-bridge transistors are controlled such that the high-side transistor of a first half-bridge and the low-side transistor of a second half-bridge are both turned on and the low-side transistor of the first half-bridge and the high-side transistor of the second half-bridge are both turned off. Third, in an active brake configuration, the half-bridge transistors are controlled such that the low-side transistor of the first half-bridge and the high-side transistor of the second half-bridge are both turned on and the high-side transistor of the first half-bridge and the low-side transistor of the second half-bridge stage are both turned off.
1. A method for charging a hold capacitor coupled between power supply nodes of output transistor half-bridge stages driving a multiphase motor, comprising:
responding to a failure of an external power supply by performing the following sequence of operations:
a) switching MOS transistors of the output transistor half-bridge stages to implement a brake configuration wherein either high-side MOS transistors or low-side MOS transistors of the output transistor half-bridge stages are turned on;
b) then switching MOS transistors of the output transistor half-bridge stages to implement an active step-up configuration wherein the high-side MOS transistor of a first output transistor half-bridge stage and the low-side MOS transistor of a second output transistor half-bridge stage are both turned on and wherein the low-side MOS transistor of the first output transistor half-bridge stage and the high-side MOS transistor of the second output transistor half-bridge stage are both turned off; and
c) then switching MOS transistors of the output transistor half-bridge stages to implement an active brake configuration wherein the low-side MOS transistor of the first output transistor half-bridge stage and the high-side MOS transistor of the second output transistor half-bridge stage are both turned on and wherein the high-side MOS transistor of the first output transistor half-bridge stage and the low-side MOS transistor of the second output transistor half-bridge stage are both turned off.
2. The method of claim 1 , further comprising the step of repeating steps a)-c).
3. The method of claim 1 , further comprising, after step a) and before step b), switching MOS transistors of the output transistor half-bridge stages to implement a tristate configuration wherein the high-side MOS transistors of the first and second output transistor half-bridge stages and the low-side transistors of the first and second output transistor half-bridge stages are all turned off.
4. The method of claim 3 , further comprising:
sensing a voltage at terminals of the multiphase motor during the tristate configuration;
determining a rotor position based on the sensed voltage; and
selecting the high-side MOS transistor of the first output transistor half-bridge stage and the low-side transistor of the second output transistor half-bridge stage be both turned on based on the determined rotor position.
5. The method of claim 1 , wherein switching MOS transistors of the output transistor half-bridge stages to implement the active step-up configuration causes the multiphase motor to generate a charging current in response to motor rotation following failure of the external power supply, the method further comprising applying the charging current to the hold capacitor to generate a voltage stored by the hold capacitor.
6. The method of claim 5 , further comprising using the voltage stored by the hold capacitor to power operation of a further motor different than said multiphase motor.
7. The method of claim 6 , wherein the multiphase motor is a spindle motor of a disk drive and wherein the further motor is a voice coil motor of said disk drive.
8. The method of claim 1 , further comprising before step b):
sensing a voltage at terminals of the multiphase motor;
determining a rotor position based on the sensed voltage; and
selecting the high-side MOS transistor of the first output transistor half-bridge stage and the low-side transistor of the second output transistor half-bridge stage be both turned on based on the determined rotor position.
9. A circuit for driving a multiphase motor, comprising:
a power supply node configured to receive an external power supply for powering the multiphase motor;
a common reference node;
a plurality of half bridges coupled between said power supply node and said common reference node, each half bridge comprising a high-side MOS transistor, a low-side MOS transistor and an output node coupled to a respective winding terminal of the multiphase motor; and
a control circuit configured to:
sense a failure of the external power supply and perform the following sequence of operations:
a) switch MOS transistors of the half bridges to implement a brake configuration wherein either high-side MOS transistors or low-side MOS transistors of the half bridges are turned on;
b) then switch MOS transistors of the half bridges to implement an active step-up configuration wherein the high-side MOS transistor of a first half bridge and the low-side MOS transistor of a second half bridge are both turned on and wherein the low-side MOS transistor of the first half bridge and the high-side MOS transistor of the second half bridge are both turned off; and
c) then switch MOS transistors of the half bridges to implement an active brake configuration wherein the low-side MOS transistor of the first half bridge and the high-side transistor of the second half bridge are both turned on and wherein the high-side MOS transistor of the first half-bridge and the low-side transistor of the second half bridge are both turned off.
10. The circuit of claim 9 , further comprising a hold capacitor coupled between said power supply node and said common reference node, and wherein the active step-up configuration generates a current for charging the hold capacitor to generate a voltage stored by the hold capacitor.
11. The circuit of claim 10 , further comprising a further motor different than said multiphase motor that is powered from the power supply node and the voltage stored by the hold capacitor.
12. The circuit of claim 11 , wherein the multiphase motor is a spindle motor of a disk drive and wherein the further motor is a voice coil motor of said disk drive.
13. The circuit of claim 9 , wherein the brake configuration causes the multiphase motor to generate a first current in a phase winding of the multiphase motor in response to motor rotation following failure of the external power supply, and wherein the active brake configuration causes the multiphase motor to generate a second current in the phase winding of the multiphase motor in response to motor rotation following failure of the external power supply having a slope which is greater than a slope of the first current.
14. The circuit of claim 9 , wherein the control circuit is further configured to cause steps a)-c) to be repeated.
15. The circuit of claim 9 , wherein the control circuit is further configured to perform an operation, after a) and before b), to switch MOS transistors of the half-bridges to implement a tristate configuration wherein the high-side MOS transistors of the first and second half-bridges and the low-side transistors of the first and second half-bridges are all turned off.
16. A method for charging a hold capacitor coupled between power supply nodes of output transistor half-bridge stages driving a multiphase motor, comprising:
responding to a failure of an external power supply by performing the following sequence of operations:
a) switching MOS transistors of the output transistor half-bridge stages to implement a brake configuration wherein either high-side MOS transistors or low-side MOS transistors of the output transistor half-bridge stages are turned on;
b) detecting a direction of current flow through the multiphase motor;
c) based on the detected direction of current flow, selecting the high-side MOS transistor of one of the output transistor half-bridge stages and the low-side MOS transistor of another of the output transistor half-bridge stages to be both turned on to charge the hold capacitor in an active step-up phase of operation; and
d) based on that same detected direction of current flow, selecting the high-side MOS transistor of the another one of the output transistor half-bridge stages and the low-side MOS transistor of said one of the output transistor half-bridge stages to be both turned on to jump start current flow in an active brake phase of operation prior to a subsequent implementation of the brake configuration.
17. The method of claim 16 , wherein step c) further comprises selecting the low-side MOS transistor of the one of the output transistor half-bridge stages and the high-side MOS transistor of the another of the output transistor half-bridge stages to be both turned off during the active step-up phase of operation.
18. The method of claim 16 , wherein step d) further comprises selecting the low-side MOS transistor of the another one of the output transistor half-bridge stages and the high-side MOS transistor of said one of the output transistor half-bridge stages to be both turned off during the active brake phase of operation.
19. The method of claim 16 , further comprising the step of repeating steps a)-d).
20. The method of claim 16 , further comprising, before step c), step d) switching MOS transistors of the output transistor half-bridge stages to implement a tristate configuration wherein the high-side MOS transistors of the output transistor half-bridge stages and the low-side transistors of the output transistor half-bridge stages are all turned off.
21. The method of claim 20 , wherein step b) is performed during step d).
22. The method of claim 16 , further comprising using the charge stored by the hold capacitor to power operation of a further motor different than said multiphase motor.
23. The method of claim 22 , wherein the multiphase motor is a spindle motor of a disk drive and wherein the further motor is a voice coil motor of said disk drive.
24. A circuit for driving a multiphase motor, comprising:
a power supply node configured to receive an external power supply for powering the multiphase motor;
a common reference node;
a hold capacitor coupled between said power supply node and said common reference node;
a plurality of half bridges coupled between said power supply node and said common reference node, each half bridge comprising a high-side MOS transistor, a low-side MOS transistor and an output node coupled to a respective winding terminal of the multiphase motor; and
a control circuit configured to:
sense a failure of the external power supply and perform the following sequence of operations:
a) switch MOS transistors of the output transistor half-bridge stages to implement a brake configuration wherein either high-side MOS transistors or low-side MOS transistors of the output transistor half-bridge stages are turned on;
b) detect a direction of current flow through the multiphase motor;
c) based on the detected direction of current flow, select the high-side MOS transistor of one of the output transistor half-bridge stages and the low-side MOS transistor of another of the output transistor half-bridge stages to be both turned on to charge the hold capacitor in an active step-up phase of operation; and
d) based on that same detected direction of current flow, select the high-side MOS transistor of the another one of the output transistor half-bridge stages and the low-side MOS transistor of said one of the output transistor half-bridge stages to be both turned on to jump start current flow in an active brake phase of operation prior to a subsequent implementation of the brake configuration.
25. The circuit of claim 24 , further comprising a further motor powered from the power supply node and the charge stored by the hold capacitor.
26. The circuit of claim 25 , wherein the multiphase motor is a spindle motor of a disk drive and wherein the further motor is a voice coil motor of said disk drive.
27. The circuit of claim 24 , wherein a first current in a phase winding of the multiphase motor is generated in the brake configuration, and wherein a second current in the phase winding of the multiphase motor in generated in the active brake configuration, said second current having a slope which is greater than a slope of the first current.
28. The circuit of claim 24 , wherein the control circuit is further configured to cause steps a)-c) to be repeated.
29. The circuit of claim 24 , wherein the control circuit is further configured to perform an operation, before c), to switch all MOS transistors of the output transistor half-bridge stages off to implement a tristate configuration.