Backup power for reducing host current transients
A data storage device (DSD) includes a power supply from a host and a charge storage element. A current transient is detected on the power supply from the host and it is determined whether the current transient exceeds a current threshold. When the current transient exceeds the current threshold, power is drawn from the charge storage element to reduce power drawn from the host.
1. A data storage device (DSD) including a power supply from a host, the DSD comprising:
a charge storage element for supplying power for the DSD;
current sense circuitry for detecting a current transient on the power supply from the host; and
a current regulating circuit configured to:
determine whether the current transient exceeds a current threshold that corresponds to a current limit of the power supply from the host;
when the current transient exceeds the current threshold, cause the DSD to draw power from the charge storage element; and
stop power drawn from the charge storage element.
2. The DSD of claim 1 , wherein the current regulating circuit is further configured to stop power drawn from the charge storage element after at least one of:
a predetermined period of time,
when a voltage level of the charge storage element reaches or falls below a threshold voltage, and
when a current transient of power drawn by the DSD no longer exceeds the current threshold.
3. The DSD of claim 2 , wherein the threshold voltage corresponds to a voltage used to provide the DSD with power after an unexpected loss in power supplied from the host.
4. The DSD of claim 2 , wherein the threshold voltage is 0 volts.
5. The DSD of claim 1 , wherein the current regulating circuit is further configured to determine whether the charge storage element is available to supply power.
6. The DSD of claim 5 , wherein the current regulating circuit is further configured to determine whether the charge storage element is available to supply power by:
comparing a voltage level of the charge storage element to a threshold voltage; and
determining that the charge storage element is not available when the voltage level is at or below the threshold voltage.
7. The DSD of claim 1 , further comprising a solid state memory.
8. The DSD of claim 1 , further comprising a hard disk drive.
9. The DSD of claim 1 , further comprising a hybrid drive.
10. A method for reducing current transients for a power supply from a host to a data storage device (DSD) including a charge storage element, the method comprising:
detecting a current transient on the power supply from the host to the DSD;
determining whether the current transient exceeds a current threshold that corresponds to a current limit of the power supply from the host;
when the current transient exceeds the current threshold, drawing power from the charge storage element to reduce power drawn from the host; and
stopping power drawn from the charge storage element.
11. The method of claim 10 , wherein stopping power drawn from the charge storage element occurs after at least one of:
a predetermined period of time,
when a voltage level of the charge storage element falls below a threshold voltage, and
when a current transient of power drawn by the DSD no longer exceeds the current threshold.
12. The method of claim 11 , wherein the threshold voltage corresponds to a voltage used to provide the DSD with power after an unexpected loss in power supplied from the host.
13. The method of claim 10 , further comprising determining whether the charge storage element is available to supply power.
14. The method of claim 13 , wherein determining whether the charge storage element is available to supply power includes:
comparing a count of current transients that exceed the current threshold in a time period to a predetermined limit; and
determining that the charge storage element is not available when the count of current transients for the time period exceeds the predetermined limit.
15. The method of claim 13 , wherein determining whether the charge storage element is available to supply power includes:
comparing a voltage level of the charge storage element to a threshold voltage; and
determining that the charge storage element is not available when the voltage level is below the threshold voltage.
16. The method of claim 13 , further comprising reducing a performance of the DSD when it is determined that the charge storage element is not available to supply power.
17. The method of claim 10 , further comprising setting the current threshold based on a rate of change of the current transient.
18. A data storage device (DSD) including a power supply from a host, the DSD comprising:
a charge storage element for supplying power for the DSD;
current sense circuitry for detecting a current transient on the power supply from the host; and
a current regulating circuit configured to:
determine whether the current transient exceeds a current threshold;
when the current transient exceeds the current threshold, determine whether the charge storage element is available to supply power by:
comparing a count of current transients which exceed a current threshold in a time period to a predetermined limit; and
determining that the charge storage element is not available when the count of current transients for the time period exceeds the predetermined limit;
when the current transient exceeds the current threshold and the charge storage element is available to supply power, cause the DSD to draw power from the charge storage element; and
stop power drawn from the charge storage element.
19. A data storage device (DSD) including a power supply from a host, the DSD comprising:
a charge storage element for supplying power for the DSD;
current sense circuitry for detecting a current transient on the power supply from the host; and
a current regulating circuit configured to:
determine whether the current transient exceeds a current threshold;
detennine whether the charge storage element is available to supply power;
when the current transient exceeds the current threshold and the charge storage element is available to supply power, cause the DSD to draw power from the charge storage element;
stop power drawn from the charge storage element; and
when the current transient exceeds the current threshold but the charge storage element is not available to supply power, reduce a performance of the DSD.
20. A data storage device (DSD) including a power supply from a host, the DSD comprising:
a charge storage element for supplying power for the DSD;
current sense circuitry for detecting a current transient on the power supply from the host; and
a current regulating circuit configured to:
determine whether the current transient exceeds a current threshold set based on a rate of change of the current transient;
when the current transient exceeds the current threshold, cause the DSD to draw power from the charge storage element; and
stop power drawn from the charge storage element.