This application claims priority to Chinese Application No. 201110369595.4 filed on Nov. 21, 2011, which is incorporated herein by reference.
The present application relates to regulators, and more particularly but not limited to energy-efficient regulators and electronic devices including the same.
An integrated circuit (IC) may include a great number of components with different operating voltages. However, one chip usually has only one power supply providing a fixed voltage, e.g., about 3V, about 5V, etc. Therefore, regulators are necessary to transform the fixed voltage to the operating voltages.
A conventional regulator includes an operational amplifier and two resistors. Any voltage which is lower than the power supply voltage and higher than a reference voltage can be provided by the regulator. However, a power consumption of the amplifier is exorbitant in case the regulator is supported by a battery and the power efficiency requirement is very high.
Therefore, a new regulator is required.
In some embodiments of the invention, a regulator without an operational amplifier is provided for power efficiency. Specifically, the regulator comprises an output circuit and a feedback loop, the feedback loop monitors any change of an output voltage provided by the output circuit and provides a control voltage for the output circuit according to the changed output voltage. The change of the output voltage is thereby offset.
In an embodiment of the invention, a regulator comprises an output circuit configured to receive a feedback voltage and provide an output current based on the feedback voltage, wherein an output voltage of the regulator is based on, at least in part, the output current; a first MOSFET coupled to the output circuit and configured to receive the output voltage of the regulator; a second MOSFET coupled to the first MOSFET and configured to provide the feedback voltage based on, at least in part, the output voltage; a current sink coupled to the first MOSFET and the second MOSFET and configured to receive jointly a current from the first MOSFET and a current from the second MOSFET; a current source coupled to the second MOSFET and configured to provide the second MOSFET with the current in the second MOSFET, a connection of the current source and the second MOSFET is further coupled to the output circuit and configured to provide the feedback voltage based on, at least in part, the current in the second MOSFET.
In an embodiment, an electronic device comprises a regulator, comprising: an output circuit configured to receive a feedback voltage and provide an output current based on the feedback voltage, wherein an output voltage of the regulator is based on, at least in part, the output current; a first MOSFET coupled to the output circuit and configured to receive the output voltage of the regulator; a second MOSFET coupled to the first MOSFET and configured to provide the feedback voltage based on, at least in part, the output voltage; a current sink coupled to the first MOSFET and the second MOSFET and configured to receive jointly a current from the first MOSFET and a current from the second MOSFET; a current source coupled to the second MOSFET and configured to provide the second MOSFET with the current in the second MOSFET, a connection of the current source and the second MOSFET is further coupled to the output circuit and configured to provide the feedback voltage based on, at least in part, the current in the second MOSFET; a load coupled to the regulator and configured to receive the output voltage and the output current.
Non-limiting and non-exhaustive embodiments of the present invention are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified.
Various aspects and examples of the invention will now be described. The following description provides specific details for a thorough understanding and enabling description of these examples. Those skilled in the art will understand, however, that the invention may be practiced without many of these details. Additionally, some well-know structures or functions may not be shown or described in detail, so as to avoid unnecessarily obscuring the relevant description.
The terminology used in the description presented below is intended to be interpreted in its broadest reasonable manner, even though it is being used in conjunction with a detailed description of certain specific examples of the invention. Certain terms may even be emphasized below, however, any terminology intended to be interpreted in any restricted manner will be overtly and specifically defined as such in this Detailed Description section.
The power of the load 120 may sometimes change according to need. For example, a light-emitting diode needs more power to increase a luminance, a heating wire needs more power to heat an object to a higher temperature. More electricity from the regulator 200 is required when the power of the load 120 increases, the output voltage is hence “drawn down” momentarily. If the regulator 200 does not react in response to the power increment, the output voltage may keep decreasing and cannot drive the load 120 effectively. Similarly, less electricity from the regulator 200 is required when the power of the load 120 decreases, the output voltage is hence “pulled up” momentarily. In some embodiments, as will be described below, the regulator 200 is configured to offset the change of the output voltage caused by, for example but not limited to, the changing power of the load 120 so as to provide a static output voltage. An exemplary view of the relationship between the power of the load 120 and the output voltage provided by the regulator 200 is illustrated in
In some embodiments, the load 120 is required to operate most of the time, for example, a detection circuit in an on board unit (OBU) in an Electronic Toll Collection (ETC) system. The detection circuit is configured to detect if a wake up signal has been received and therefore has to operate most of the time. As the OBU is generally supported by a battery, it would be preferred if the regulator is power efficient.
In the regulator 200, an output circuit 220 receives a feedback voltage and provides an output voltage for the regulator 200. Referring to
MOSFET 222 is, in this embodiment, a P-type MOSFET. A source (first input end) of MOSFET 222 is coupled to the output circuit 221 and configured to receive the output voltage. A gate (second input end) of MOSFET 222 receives a first control voltage. A drain (output end) of MOSFET 222 is configured to provide a first voltage based on the output voltage and the first control voltage. As can be seen from
v
out
=v
firstctl
+v
GS222 (1)
where vout is the output voltage of the regulator 200, vfirstctl is the first control voltage, which is generally consistent, vGS222 is the voltage between the source and gate of MOSFET 222. As MOSFET 222 is set to a saturation zone, vGS222 is subject to equation (2):
where vGS222 is the voltage between the source and the gate of MOSFET 222 and may change with the output voltage, Vth is a threshold voltage of MOSFET 222, IDS is the current in MOSFET 222 when vGS is equal to 2×Vth. Note IDS, Vth are both consistent.
A source (first input end) of MOSFET 223 receives the first voltage, a gate (second input end) of MOSFET 223 receives a second control voltage which is generally consistent. In an embodiment, the first and second control voltages are the same. A drain (output end) of the MOSFET 223 is configured to provide the control voltage which is received by the output circuit 221.
A current sink 224, which is realized by a MOSFET 224 is coupled to the first and second MOSFETs 222 and 223. Specifically, the source of MOSFET 224 is grounded, a gate is configured to receive a gate voltage which sets MOSFET 224 to receive an expected current from MOSFETs 222 and 223, and a drain of MOSFET 224 is configured to receive a current from MOSFETs 222 and 223. As a current sink, MOSFET 224 requires a fixed current, therefore, in case one of the currents from MOSFETs 222 and 223 changes, the other current is forced to change adversely.
A current source 225 is realized by a MOSFET 225. A source of MOSFET 225 is coupled to a power supply (providing a first voltage, e.g., about 3V), a gate of MOSFET 225 is configured to receive an appropriate gate voltage such that the current source 225 is providing an expected current to MOSFET 223. A drain of MOSFET 225 is coupled to the drain of MOSFET 223 and the output circuit 221.
In the regulator 200, a current from the output circuit 221 is divided at its drain to a first part which flows into the source of MOSFET 222 and a second part which flows towards the load 120 (not shown in
In some embodiments, the output circuit 221 is configured to increase the output current if the feedback voltage decreases in response to a decrement of the output voltage.
In an embodiment, the power of the load 120 may change with time, e.g., as shown in
In an embodiment, at time t2, the power of the load 120 decreases suddenly (e.g., the power is changed automatically according to need or by a user), in response to the power decrement, the output voltage increases, as shown in
v
ref
=v
GS411
+v
GS412
+v
GS413 (3)
Examining
v
out
=v
GS222
+v
GS412
+v
GS413 (4)
In some embodiments, vGS222 and vGS411 are configured to be the same so as veut follows vref. In an embodiment, the bias current is equal to the current provided by the current source 225, in addition, the MOSFET 224 is configured to receive a double of the bias current. Therefore, i222 is equal to i411 and hence vGS222 is equal to vGS411.
As will be appreciated, though a term “first input end” refers to a source of each MOSFET in the context, it is not intended to limit the scope of the invention thereby. In some embodiments, “first input end” may be a gate of a MOSFET or even a drain thereof. Moreover, though each MOSFET is illustrated specifically as a N-type MOSFET or a P-type MOSFET in the figures, variations which replace at least one N-type MOSFET by at least one P-type MOSFET or replace at least one N-type MOSFET and change connections accordingly are still within the scope of the present application.
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
Number | Date | Country | Kind |
---|---|---|---|
201110369595.4 | Nov 2011 | CN | national |