1. Field of Invention
The present invention relates to a voltage regulator and a control circuit and a control method of a voltage regulator; particularly, it relates to such voltage regulator and control circuit and control method capable of adjusting the output voltage to reduce the power consumption while maintaining a stable supply of output current.
2. Description of Related Art
The development of the technology of USB On-the-Go (USB OTG) makes consumers more easily connect different types of portable devices together. USB OTG enables the device equipped with such technology to act as a host and provide power to other portable electronic devices connected to it while operating itself. The OTG host usually operates and provides power by one single lithium battery with voltage ranging from 3V to 4.2V.
Please refer to FIG. 1, which shows a schematic diagram of a conventional voltage regulator 100. When the OTG host supplies power to other portable devices, the voltage regulator 100 included in the OTG host converts an input voltage Vin supplied from a battery 10 to an output voltage Vout. For example, a lower input voltage Vin (e.g., 3V) is converted to a higher output voltage Vout (e.g., 5V) so that the output voltage Vout of 5V is supplied to a load 19. The load 19 can be, for example but not limited to, a rechargeable battery of another portable electronic device. As shown in FIG. 1, the voltage regulator 100 comprises a power stage 11, a control circuit 12 and a voltage detection circuit 13. The voltage detection circuit 13 can be, for example but not limited to, a voltage divider circuit which generates a feedback signal related to the output voltage. The power stage 11 controls at least one power switch (not shown) included therein in response to an operation signal to convert the input voltage Vin at the input terminal IN to the output voltage Vout at the output terminal OUT.
In this prior art, the output voltage Vout is a constant and is invariable. However, the load 19 may only require a stable supply of current but does not require the supply of a high voltage, so the supply of a high voltage may lead to unnecessary power consumption. For example, the load 19 may only require a stable current of 0.5 A, and an output voltage Vout of 4.3V is sufficient to provide such current and maintain the normal operation of the load 19. Thus, when the voltage regulator 100 provides an output voltage Vout of 5V to the load 19, there will be unnecessary power consumption of 0.35 watt ((5V−4.3V)×0.5 A=0.35 watt). Therefore, it is desired to reduce the unnecessary power consumption in the prior art.
In view of the above, to overcome the drawbacks in the prior art, the present invention proposes a voltage regulator and a control circuit and a control method of a voltage regulator, which is capable of adjusting the level of the output voltage depending on the load's practical needs to avoid unnecessary power consumption, and is capable of adjusting the output voltage in response to the status of the output current to optimize the operation of the voltage regulator.