Patent Application
20120011376
According to the Universal Serial Bus (USB) specification, host USB devices can power other (e.g., peripheral) devices. Host USB devices, such as personal computers and notebook computers, can provide up to but not more than 500 milli-amperes (mA) of electrical current to a peripheral device such as a portable storage device (e.g., a portable hard disk drive).
Contemporary portable storage devices (e.g., 2.5-inch portable hard disk drives) can consume up to 1000 mA of current during read or write operations, not including the amount of current consumed by the USB-to-SATA (Serial Advanced Technology Attachment) bridge integrated circuit. Clearly, the amount of current needed by a portable storage device can exceed the limit included in the USB specification.
To overcome this problem, some types of portable storage devices are equipped with a USB Y-cable that allows the drive to be plugged into two USB ports at the same time. A portable storage device can thus draw up to 500 mA of current from one USB port and up to another 500 mA of current from another USB port, thereby obtaining the amount of current needed for read and write operations. However, this type of solution may be problematic because the host device may not have two available USB ports. That is, the host device's USB ports may be needed for other purposes, and it may not be possible to devote two ports to a single device such as a portable storage device.
Other types of portable storage devices are instead equipped with a power adapter that allows them to be plugged into an external power supply (e.g., an electrical outlet). However, this type of solution is cumbersome and inconvenient, especially for a storage device that is supposed to be portable. In other words, a power adapter can be relatively bulky, and its use requires that the portable storage device be placed with reach of an electrical outlet (e.g., a wall outlet).
Embodiments according to the invention provide solutions to the problems described above. In one embodiment, a data bus is also used to supply power from a first power source to a sink device. A second power source can supplement the electrical current on the data bus if the voltage on the data bus decreases to less than a threshold value.
More specifically, in one embodiment, a power circuit for a portable storage device (e.g., a portable hard disk drive) includes a rechargeable battery and a USB cable that can be plugged into a USB port on a host device. While the storage device is operating, it can draw power (electrical current) both from the battery and from the host device via the USB cable. While the storage device is in standby mode or is turned off, the battery can be recharged by the host device via the USB cable. Combined, the battery and the host device provide the peak amount of electrical current (e.g., 1000 mA) needed by the storage device.
Thus, for example, a storage device can be operated using only a single USB port, and a separate power adapter is not needed.
These and other objects and advantages of the various embodiments of the present disclosure will be recognized by those of ordinary skill in the art after reading the following detailed description of the embodiments that are illustrated in the various drawing figures.
The accompanying drawings, which are incorporated in and form a part of this specification and in which like numerals depict like elements, illustrate embodiments of the present disclosure and, together with the description, serve to explain the principles of the disclosure.
Reference will now be made in detail to the various embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. While described in conjunction with these embodiments, it will be understood that they are not intended to limit the disclosure to these embodiments. On the contrary, the disclosure is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the disclosure as defined by the appended claims. Furthermore, in the following detailed description of the present disclosure, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it will be understood that the present disclosure may be practiced without these specific details. In other instances, well-known methods, procedures, components, and circuits have not been described in detail so as not to unnecessarily obscure aspects of the present disclosure.
In overview, with reference to
Continuing with reference to
In one embodiment, the second power source 112 can also provide up to 500 mA of electrical current to the sink device. In one embodiment, the second power source 112 is a battery. The battery can be a rechargeable battery. Accordingly, in such an embodiment, the circuit 100 can include a battery charger (not shown in
As noted above, the second power source 112 of
The battery 202 can be a lithium-ion rechargeable battery, in which case the battery charger 206 is a lithium-ion battery charger. In one embodiment, the battery 202 supplies 3.7 volts (V) and the boost converter 204 is a 3.7 V to 4.7 V boost converter. However, as will be seen, such values are simply a matter of design choice.
In operation, the circuit 200 works as follows. The USB port on the host device will provide 500 mA of current (I-usb). Of that amount, about 100 mA of current (I-bridge) will be consumed by the integrated circuit 210, leaving about 400 mA (I-usb-to-hdd) for delivery to the storage device 250. This amount of current, by itself, is insufficient to power the storage device 250.
As the 500 mA current limit from the USB port becomes a factor, the voltage Vusb will start to drop. When Vusb reaches a threshold value, the boost converter 204 will start to draw power from the battery 202 in order to provide a supplemental current (I-boost) that is needed to power up and operate the storage device 250. In other words, the amount of current (I-hdd) provided to the storage device is the sum of I-usb-to-hdd and I-boost. In one embodiment, the boost converter supplies an additional 500 mA of current. Thus, the current from the boost converter 204 supplements the current from the USB port and provides the extra current needed to spin up and operate the storage device 250.
In one embodiment, the threshold value is 4.7 V; as mentioned above, this value is a matter of design choice. In general, the threshold value corresponds to the characteristics of the boost converter 204, and vice versa.
The switches SW1 are switched on (closed) when the storage device 250 is turned on. The switches SW1 are otherwise switched off (opened) to prevent the battery 202 from draining.
Thus, as just described, the battery 202 is not used until the voltage Vusb drops to the threshold value (e.g., 4.7 V). The battery 202 can be recharged when it is not needed. More specifically, the battery 202 can be recharged each time the storage device 250 is in standby mode or is powered off.
In one embodiment, the storage device 250 is equipped with an automatic standby feature that places the drive in standby mode when the drive has been inactive for a specified period of time. In one embodiment, if the storage device 250 has not received a command from the host for a period of 30 seconds, then the drive automatically enters standby mode. In standby mode, the amount of current drawn by the storage device 250 is reduced to about 150 mA. The 30-second threshold is a matter of design choice.
The battery charger 206 uses current from the host device (specifically, current from the USB port) to recharge the battery 202. In one embodiment, the battery charger 206 is turned on in response to a signal from the storage device 250 that indicates the drive is in standby mode. In one such embodiment, the P11 pin of the storage device 250 is used to provide that signal. More specifically, when the storage device 250 is in standby mode, a logic-low signal from the P11 pin can be used to turn on the battery charger 206. In response to a command from the integrated circuit 210, the storage device 250 can be awakened and can enter active mode. Consequently, the P11 pin will send a logic-high signal that will turn off the battery charger 206.
The P11 pin is conventionally used to turn on a light-emitting diode to provide a visual indication that the storage device 250 is operating. Thus, the P11 pin provides an elegant means of turning on and off the battery charger 206.
To summarize, with reference to
When the storage device 250 is not operating (e.g., in standby mode), then the current from the USB port is instead used to recharge the battery 202. Recharging the battery 202 does not affect operation of the storage device 205 in standby mode, because the current demanded by the drive in standby mode is reduced and can be satisfied by just the current I-usb-to-hdd.
The battery 202 can also be charged when the storage device 250 is turned off.
Thus, embodiments according to the present invention provide sufficient power (specifically, electrical current) to a peripheral device using a single power/data cable by selectively supplementing the power (current) carried by the cable with power (current) from a second power source.
In block 404, in response to the sensed voltage falling to less than a threshold value, current is provided from a rechargeable second power source to the sink device to supplement current from the first power source.
In block 406, charging of the rechargeable second power source is initiated in response to the sink device transitioning from active mode to standby mode.
In summary, according to embodiments of the present invention, a peripheral device—for example, a portable storage device such as a portable hard disk drive—can be powered using only a single USB port, without using an extra USB Y-cable or a power adapter. More than 500 mA of current can be delivered to the peripheral device using a single USB port that is limited to providing only 500 mA of current.
Because only a single USB port is needed, other USB ports can be allocated to other uses. Because an adapter is not needed, the peripheral device is less cumbersome and easier to use.
The foregoing description, for purpose of explanation, has been described with reference to specific embodiments. However, the illustrative discussions above are not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations are possible in view of the above teachings. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as may be suited to the particular use contemplated.
Thus, although described for examples based on USB and portable storage devices such as portable hard disk drives, embodiments of the invention can be utilized with other types of standards and other types of devices.
Embodiments according to the invention are thus described. While the present disclosure has been described in particular embodiments, it should be appreciated that the invention should not be construed as limited by such embodiments, but rather construed according to the below claims.
