Patent Application
20140347026
Voltage regulator circuits are often used in electronic devices to generate a stable output voltage from a relatively inconsistent power source. For instance, voltage provided by a power source may fluctuate due to environmental noise or various characteristics of the power supply. A voltage regulator adjusts power provided at an output to maintain a more consistent output voltage relative to the power source.
Various example embodiments are directed to voltage regulator circuits and their implementation.
In one embodiment, an integrated circuit (IC) having a voltage regulator circuit is provided. The voltage regulator circuit includes a pass circuit including a field effect transistor (FET) having a gate coupled to the output of a comparison circuit. The comparison circuit is configured to provide a signal to the pass circuit that is based on a comparison of a first input coupled to a reference voltage and a second input. The voltage regulator includes a feedback path configured and arranged to provide feedback from an output of the pass circuit to a second input of the comparison circuit. The voltage regulator also includes a current adjustment circuit configured and arranged to adjust current consumed by the comparison circuit based on a current passed by the pass circuit.
In another embodiment, an IC having a voltage regulator circuit is provided that includes a pass circuit having a FET gate coupled to the output of a comparison circuit. The comparison circuit is configured to provide a signal to the pass circuit that is based on a comparison of a first input coupled to a reference voltage and a second input. The voltage regulator includes a feedback path configured and arranged to provide feedback from an output of the pass circuit to a second input of the comparison circuit. The feedback path includes a first capacitor coupled to provide feedback from the output of the pass circuit to the second input of the comparison circuit and includes a second capacitor coupled to provide feedback from the output of the comparison circuit to the second input of the comparison circuit.
The above discussion/summary is not intended to describe each embodiment or every implementation of the present disclosure. The figures and detailed description that follow also exemplify various embodiments.
Various example embodiments may be more completely understood in consideration of the following detailed description in connection with the accompanying drawings, in which:
While various embodiments discussed herein are amenable to modifications and alternative forms, aspects thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the scope of the disclosure including aspects defined in the claims. In addition, the term “example” as used throughout this application is only by way of illustration, and not limitation.
One or more example embodiments are directed to a regulator circuit. In one example embodiment, a voltage regulator circuit is provided that includes a pass circuit controlled by a comparison circuit. The comparison circuit is configured to provide a signal to the pass circuit that is based on a comparison of a first input coupled to a reference voltage and a second input. The voltage regulator circuit includes a feedback path configured and arranged to provide feedback from an output of the pass circuit to a second input of the comparison circuit. The voltage regulator circuit also includes a current adjustment circuit configured to adjust current consumed by the comparison circuit based on a current passed by the pass circuit.
In some embodiments, the feedback circuit is configured to provide feedback from an output of the voltage regulator circuit, and from an output of the comparison circuit, to the second input of the comparison circuit. In one implementation, the feedback circuit includes a first capacitor connected to provide a feedback path from the output of the voltage regulator circuit to the second input of the comparison circuit. The feedback circuit also includes a second capacitor providing a feedback path from the output of the comparison circuit to the input of the comparison circuit. In some embodiments, the feedback path further includes a resistor divider network configured to provide feedback from the output of the pass circuit to the second input of the comparison circuit. In some embodiments, a voltage regulator circuit includes a feedback circuit having first and second capacitors as described above with the current adjustment circuit omitted.
In some embodiments, a voltage regulator circuit may include a number of optional components in various combinations. For example, in some embodiments, the voltage regulator circuit includes a circuit configured to prevent over-current through the pass circuit that may damage the voltage regulator circuit. For instance, in some embodiments, the voltage regulator circuit includes a circuit configured to monitor current through the pass circuit and an over-current control circuit configured to cause an adjustment circuit drain voltage of the output of the transconductance (GM) amplifier in response to the monitored current exceeding an upper threshold current. Reducing the voltage at the output of the transconductance amplifier reduces the voltage of error signal and causes the pass circuit to reduce the amount of current passed.
In some embodiments, the voltage regulator circuit includes an over-temperature control circuit configured to prevent the voltage regulator circuit from operating in temperature ranges that may damage circuitry of the voltage regulator circuit. For instance, in one example implementation, the over-temperature control circuit is configured to adjust the error signal to disable the pass gate. In another example implementation, the over-temperature control circuit is configured to cause a switch (not shown) to disconnect the voltage regulator circuit from the power supply. Other implementations may be used as well.
In some embodiments, the voltage regulator circuit includes an output regulator circuit, which provides a current sink that improves performance of the voltage regulator circuit. In some embodiments, the voltage regulator circuit includes a reference voltage generator circuit that is configured to provide the reference voltage to an input of the comparison circuit.
In some embodiments, the voltage regulator circuit includes a charge pump configured to generate a higher voltage from a lower supply voltage and provide the higher voltage to power the comparison circuit. For instance, the charge pump may be configured to provide the higher voltage in response to the lower supply voltage falling below a lower threshold.
A skilled artisan will recognize that the comparison circuit and pass circuit, as discussed in connection with various embodiments, may be implemented using a variety of gate driven amplifier circuits. For example, the pass circuit may be implemented using one or more FET based transistors. Such a transistor may include, for example, a MOSFET coupled in a pull-up configuration with a voltage source and driven by the reference voltage. In some other embodiments, the pass circuit may be implemented using a CMOS driver circuit, an operational amplifier, or other circuit with similar functionality. As another example, in some embodiments, the comparison circuit includes a GM amplifier and a buffer circuit connected in series. For ease of description and illustration, the following examples describe pass circuits as being implemented using a pull-up FET and the comparison circuit as including a GM amplifier and a buffer circuit. However, it is to be understood that other circuits can be used, in connection with these and other embodiments, to effect functions similar to those functions characterized in accordance with the pass circuits described in the following. One skilled in the art will recognize that other circuit arrangements may be used to perform the functions of the various circuits described herein.
Turning now to the figures,
In some embodiments, the comparison circuit 102 includes a transconductance amplifier 104 configured to provide the error signal based on a comparison of the feedback and the reference voltage. In some embodiments, the comparison circuit 102 further includes a buffer circuit 106 configured to receive and provide the error signal to the pass circuit while isolating the high output resistance of the transconductance amplifier 104 from high load capacitance of the pass circuit 110. In some implementations, the buffer circuit 106 is configured to provide a GM boost to the error signal output from the transconductance amplifier 104.
A current adjustment circuit (120, 122) is configured to adjust the amount of current consumed by the comparison circuit based on the amount of current passed by the pass circuit. In some embodiments, the current adjustment circuit includes an adjustable current source 120 and a current sense circuit 122. The adjustable current source is configured and arranged to adjust a tail current of the comparison circuit based on a control signal from the current sense circuit that is indicative of the amount of current passed by the pass circuit. The current adjustment circuit may adjust the amount of current consumed differently in different embodiments. For instance, in one implementation the current adjustment circuit is configured to adjust power consumed by the comparison circuit by limiting current provided from the voltage supply to the comparison circuit.
In some embodiments, the voltage regulator circuit includes a charge pump 108 configured to power the comparison circuit 102. The charge pump is configured to generate a higher voltage from a lower supply voltage. When the supply voltage (Vin) falls below a lower threshold charge pump 108 is connected to provide a higher voltage to power the comparison circuit 102. In this manner, the comparison circuit may operate at an even lower input voltage level (Vin) before dropping out.
The feedback circuit 130 is configured to provide feedback from an output (Vout) of the voltage regulator circuit, and from an output of the comparison circuit, to an input of the comparison circuit. As shown in
In this example, the feedback circuit includes a first capacitor C1 connected to provide a feedback path from the output (Vout) of the voltage regulator circuit to the second input of the comparison circuit. The feedback circuit also includes a second capacitor C2 providing a feedback path from the output of the comparison circuit 102 to the input of the comparison circuit. This capacitor arrangement assists to provide superior stability in comparison to typical voltage regulator circuits. This arrangement allows smaller capacitors to be used, which can be integrated in an IC, to be used for frequency compensation, thereby reducing manufacturing cost. As one illustrative example, a voltage regulator circuit operating to regulate an input voltage ranging from 4-28V, to produce a regulated output voltage (e.g., 1-2V), C1 and C2 may be on the order of 1 pF (C1 may be slightly bigger than C2 in some applications). The total resistance of the voltage divider network (R1+R2) may be, e.g., approximately 5 MOhms. As discussed with reference to
In some embodiments, the voltage regulator circuit may include a number of optional components (shown with dotted lines). For example, in some embodiments, the voltage regulator circuit includes an over-current protection circuit (e.g., 240, 242, 244) configured to prevent over current through the pass circuit that may damage the voltage regulator circuit. For instance, in the voltage regulator circuit shown in
In some embodiments, the voltage regulator circuit includes an over-temperature control circuit 250 configured to prevent the voltage regulator circuit from operating in temperature ranges that may damage circuits of the voltage regulator circuit. For instance, in one example implementation, the over-temperature control circuit 250 is configured to adjust the error signal to disable the pass gate in response to the temperature exceeding a threshold temperature. In another example implementation, the over-temperature control circuit 250 is configured to cause a switch (not shown) to disconnect the voltage regulator circuit from the power supply. Other implementations may be used as well.
In some embodiments, the voltage regulator circuit includes an output regulator 260. The output regulator 260 provides a current sink that improves performance of the voltage regulator circuit. In the situation where load current abruptly decreases (e.g., to zero amps), current drawn by the output regulator helps to maintain a more consistent voltage.
In some embodiments, the voltage regulator circuit includes a reference voltage generator circuit 252 that is configured to provide the reference voltage to the first input (+) of the comparison circuit 102. Alternatively, in some embodiments, the reference voltage provided to the first input (+) of the comparison circuit 102 may be generated by a circuit that is not included in the same package as the voltage regulator circuit.
Further, in some embodiments, the voltage regulator circuit in
Various aspects of the present disclosure may be applied to implement a number of types of voltage regulator circuit including, e.g., linear regulators, low drop-out (LDO) regulators, and switching regulators. Linear regulators include one or more components (e.g., FETs) that are operated in saturation region to maintain a regulated output voltage, while an unregulated voltage supply remains above a dropout voltage. One particular type of linear regulator, known as a LDO regulator is characterized by an ability to operate until the unregulated voltage supply reaches a low drop-out voltage that is close to the regulated output voltage. Switching regulators, rapidly connect and disconnect a power supply to an output as required to maintain a relatively constant output voltage. It is understood that aspects of the present disclosure may be applied to other types of voltage regulators as well.
Various blocks, modules or other circuits may be implemented to carry out one or more of the operations and activities described herein and/or shown in the figures. In these contexts, a “block” (also sometimes “logic circuitry” or “module”) is a circuit that carries out one or more of these or related operations/activities (e.g., comparison of signals, generation of signals, buffering, or amplification). For example, in certain of the above-discussed embodiments, one or more modules are discrete logic circuits or programmable logic circuits configured and arranged for implementing these operations/activities, as in the circuit modules shown in
Based upon the above discussion and illustrations, those skilled in the art will readily recognize that various modifications and changes may be made to the various embodiments without strictly following the exemplary embodiments and applications illustrated and described herein. For example, various aspects discussed herein may be combined in various combinations to form different embodiments. Such modifications do not depart from the true spirit and scope of various aspects of the present disclosure, including aspects set forth in the claims.
