Overvoltage / Undervoltage Detection Circuit

Abstract

This application is titled "Overvoltage / Undervoltage Detection Circuit". An overvoltage / undervoltage protection circuit (500) includes a voltage input terminal (520), a digital-to-analog converter (502), a comparator (504), and a control circuit (506). The comparator (504) includes a first input (504A) coupled to the output (502A) of the digital-to-analog converter (502) and a second input (504B) coupled to the voltage input terminal (520). The control circuit (506) includes an output (506A) coupled to the input (502B) of the digital-to-analog converter (502) and an input (506B) coupled to the output (504C) of the comparator (504). The control circuit (506) is configured to set the digital-to-analog converter (502) to generate an overvoltage fault threshold (510) in response to the output of the comparator (504) indicating that the voltage of the signal at the voltage input terminal (520) exceeds the threshold currently generated by the digital-to-analog converter (502).

Description

Background Art

[0001] An electronic device is designed to operate within a supply voltage range between a specified maximum voltage and a minimum voltage. When the supply voltage exceeds the specified maximum voltage, an overvoltage event occurs. Similarly, when the supply voltage drops below the specified minimum voltage, an undervoltage event occurs. An undervoltage event may cause the electronic device to malfunction. An overvoltage event may damage the electronic device. Summary of the Invention

[0002] An overvoltage / undervoltage protection circuit uses a state machine to control the generation of thresholds for overvoltage / undervoltage detection. The state machine determines the priority order of overvoltage / undervoltage fault detection to provide increased threshold settling and comparison time. In one example, an overvoltage / undervoltage protection circuit includes a voltage input terminal, a digital-to-analog converter, a comparator, and a control circuit. The comparator includes a first input coupled to the output of the digital-to-analog converter and a second input coupled to the voltage input terminal. The control circuit includes an output coupled to the input of the digital-to-analog converter and an input coupled to the output of the comparator. The control circuit is configured to set the digital-to-analog converter to generate an overvoltage fault threshold in response to the output of the comparator indicating that the voltage of the signal at the voltage input terminal exceeds the threshold currently generated by the digital-to-analog converter.

[0003] In another example, a control circuit includes a state machine circuit. The state machine circuit is configured to transition from an overvoltage warning detection state to an overvoltage fault detection state in response to receiving a signal indicating that the input voltage exceeds an overvoltage warning threshold. The state machine is also configured to transition from an undervoltage warning detection state to an overvoltage fault detection state in response to the signal indicating that the input voltage exceeds an undervoltage warning threshold. The state machine is further configured to transition from an undervoltage fault detection state to an overvoltage fault detection state in response to the signal indicating that the input voltage exceeds an undervoltage fault threshold.

[0004] In an additional example, a method includes comparing an input voltage with a threshold voltage generated by a digital-to-analog converter. The digital-to-analog converter is set to generate an overvoltage fault threshold in response to the input voltage exceeding the threshold voltage and the threshold voltage being an overvoltage warning threshold. The digital-to-analog converter is set to generate an overvoltage fault threshold in response to the input voltage exceeding the threshold voltage and the threshold voltage being an undervoltage warning threshold. The digital-to-analog converter is set to generate an overvoltage fault threshold in response to the input voltage exceeding the threshold voltage and the threshold voltage being an undervoltage fault threshold. The overvoltage fault threshold is greater than the overvoltage warning threshold. The overvoltage warning threshold is greater than the undervoltage warning threshold. The undervoltage warning threshold is greater than the undervoltage fault threshold.

[0005] In a further example, a computer system includes a processor, a power supply, and an overvoltage / undervoltage protection circuit. The power supply is coupled to the processor. The overvoltage / undervoltage protection circuit is coupled to the processor and the power supply. The overvoltage / undervoltage protection circuit includes a digital-to-analog converter, a comparator, and a control circuit. The comparator includes a first input coupled to the output of the digital-to-analog converter and a second input coupled to the output of the power supply. The control circuit includes an output coupled to the input of the digital-to-analog converter and an input coupled to the output of the comparator. The control circuit is configured to set the digital-to-analog converter to generate an overvoltage fault threshold in response to the input voltage at the second input of the comparator exceeding an overvoltage warning threshold at the first input of the comparator. The control circuit is also configured to set the digital-to-analog converter to generate an overvoltage fault threshold in response to the input voltage at the second input of the comparator exceeding an undervoltage warning threshold at the first input of the comparator. The control circuit is further configured to set the digital-to-analog converter to generate an overvoltage fault threshold in response to the input voltage at the second input of the comparator exceeding an undervoltage fault threshold at the first input of the comparator. The overvoltage fault threshold is greater than the overvoltage warning threshold. The overvoltage warning threshold is greater than the undervoltage warning threshold. The undervoltage warning threshold is greater than the undervoltage fault threshold. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] To describe the various examples in detail, reference will now be made to the accompanying drawings, in which:

[0007] Figure 1 A schematic diagram showing an overvoltage / undervoltage protection circuit using a series resistor and a single comparator;

[0008] Figure 2 A schematic diagram showing an overvoltage / undervoltage protection circuit using a series resistor and multiple comparators;

[0009] Figure 3 A schematic diagram showing an overvoltage / undervoltage protection circuit using a state machine to control a digital-to-analog converter;

[0010] Figure 4 A state diagram showing the operation of an overvoltage / undervoltage protection circuit for Figure 3 ;

[0011] Figure 5 A schematic diagram showing an overvoltage / undervoltage protection circuit using a state machine that determines the priority order of overvoltage fault detection to control a digital-to-analog converter;

[0012] Figure 6 A state diagram showing the operation of an overvoltage / undervoltage protection circuit for Figure 5 ;

[0013] Figure 7 A diagram showing the operation of an overvoltage / undervoltage protection circuit for Figure 5 ;

[0014] Figure 8 A flowchart showing a method of overvoltage / undervoltage protection for determining the priority order of overvoltage fault detection; and

[0015] Figure 9 A block diagram showing a computer system including overvoltage / undervoltage protection according to the present specification. DETAILED DESCRIPTION

[0016] In this specification, the terms "coupled" or "coupling" may encompass a connection, communication, or signal path that achieves a functional relationship consistent with the description of the present disclosure. For example, if device A generates a signal to control device B to perform an action, then in a first example, device A is coupled to device B, or in a second example, if an intermediate component C substantially does not change the functional relationship between device A and device B, device A is coupled to device B through the intermediate component C such that device A controls device B through a control signal generated by device A. Additionally, in this specification, the expression "based on" means "at least partially based on". Thus, if X is based on Y, then X may be a function of Y and any number of other factors.

[0017] Since overvoltage events and undervoltage events can affect the operation of an electronic system, it is desirable to quickly detect such events. Undervoltage may cause system failures, and overvoltage events may damage the system. To reduce the likelihood of damage, the detection of overvoltage events can be prioritized over the detection of undervoltage events. Figure 1 A schematic diagram showing an overvoltage / undervoltage protection circuit 100. The overvoltage / undervoltage protection circuit 100 includes a resistor 102, a switch 104, and a comparator 106. The resistor 102 is connected in series to form a multi-tap voltage divider. The switch 104 is coupled to the taps of the voltage divider, and these taps are selected as the threshold voltages for overvoltage or undervoltage detection. For example, the first tap is selected to provide an overvoltage fault threshold, the second tap is selected to provide an overvoltage warning threshold, the third tap is selected to provide an undervoltage warning threshold, and the fourth tap is selected to provide an undervoltage fault threshold. The control circuit 108 closes a selected one of the switches 104 to route the threshold voltage to the comparator 106, and the comparator 106 compares the input voltage (VIN) with the selected threshold.

[0018] Although the overvoltage / undervoltage protection circuit 100 can provide basic overvoltage / undervoltage detection, there are many problems with the overvoltage / undervoltage protection circuit 100. For example, as the detection range or resolution increases, the complexity of the overvoltage / undervoltage protection circuit 100 increases as resistors 102 and switches 104 are added to provide that range or resolution. The fault detection speed is a function of the delay of comparator 106. A comparator designed to meet the timing requirements of higher-priority events can result in underdesign and resource waste for lower-priority events with less stringent detection and / or accuracy requirements. The overvoltage / undervoltage protection circuit 100 cannot be automatically calibrated to compensate for offsets and other errors. Drift due to aging cannot be corrected, and the resolution of any correction is limited by the step size of the voltage divider formed by resistor 102.

[0019] Because the output impedance of the voltage divider formed by resistor 102 is high, in order to increase the detection speed, some embodiments apply dedicated comparators to detect each overvoltage / undervoltage range. Figure 2 A schematic diagram showing an overvoltage / undervoltage protection circuit 200 including dedicated comparators for each overvoltage / undervoltage range. The overvoltage / undervoltage protection circuit 200 includes resistors 202, switches 204, 206, 208, and 210, comparators 212, 214, 216, and 218, and a control circuit 220. The resistors 202 are connected in series to form a multi-tap voltage divider. The switch 204 and the comparator 212 are coupled to the resistor 202 to detect overvoltage faults. The switch 206 and the comparator 214 are coupled to the resistor 202 to detect overvoltage warnings. The switch 208 and the comparator 216 are coupled to the resistor 202 to detect undervoltage warnings. The switch 210 and the comparator 218 are coupled to the resistor 202 to detect undervoltage faults. The control circuit 220 closes one of the switches 204 to set the threshold for overvoltage faults, closes one of the switches 206 to set the threshold for overvoltage warnings, closes one of the switches 208 to set the threshold for undervoltage warnings, and closes one of the switches 210 to set the threshold for undervoltage faults.

[0020] Although including dedicated comparators and switches allows the overvoltage / undervoltage protection circuit 200 to provide a higher detection speed relative to the overvoltage / undervoltage protection circuit 100, the comparators and associated switches are added to the overvoltage / undervoltage protection circuit 200 for each additional event range to be detected. The number of switches required to select a threshold for each event is a function of the detection range. As the range increases, the number of switches also increases. Like the overvoltage / undervoltage protection circuit 100, the overvoltage / undervoltage protection circuit 200 cannot be automatically calibrated.

[0021] Figure 3A schematic diagram showing an overvoltage / undervoltage protection circuit 300 that uses a digital-to-analog converter to set an event threshold. The overvoltage / undervoltage protection circuit 300 includes a digital-to-analog converter 302, a comparator 304, and a control circuit 306. The digital-to-analog converter 302 is coupled to the comparator 304 and provides a threshold voltage 310 to the comparator 304 for comparison with an input voltage 316 (VIN). The digital-to-analog converter 302 may include an R-2R resistor ladder. The control circuit 306 is coupled to the digital-to-analog converter 302 and provides a threshold 312 to the digital-to-analog converter 302. The digital-to-analog converter 302 converts the threshold 312 into the threshold voltage 310.

[0022] The control circuit 306 includes a state machine 308. The state machine 308 sets the threshold 312 provided to the digital-to-analog converter 302. Figure 4 A state diagram 400 showing the operation of the state machine 308 is presented. The state machine 308 sequentially transitions to each detection state and assigns the same priority to each detection state. In state 402 (OVF), the threshold 312 sets the digital-to-analog converter 302 to generate the threshold voltage 310 as an overvoltage fault detection threshold, and the overvoltage / undervoltage protection circuit 300 checks for overvoltage fault events. The state machine 308 transitions from state 402 to state 404. In state 404 (OVW), the threshold 312 sets the digital-to-analog converter 302 to generate the threshold voltage 310 as an overvoltage warning detection threshold, and the overvoltage / undervoltage protection circuit 300 checks for overvoltage warning events. The state machine 308 transitions from state 404 to state 406. In state 406 (UVW), the threshold 312 sets the digital-to-analog converter 302 to generate the threshold voltage 310 as an undervoltage warning detection threshold, and the overvoltage / undervoltage protection circuit 300 checks for undervoltage warning events. The state machine 308 transitions from state 406 to state 408. In state 408 (UVF), the threshold 312 sets the digital-to-analog converter 302 to generate the threshold voltage 310 as an undervoltage fault detection threshold, and the overvoltage / undervoltage protection circuit 300 checks for undervoltage fault events. The state machine 308 transitions from state 408 back to state 402 to check for overvoltage fault events.

[0023] The overvoltage / undervoltage protection circuit 300 advantageously uses a single digital-to-analog converter 302 and comparator 304 to detect all overvoltage / undervoltage events, and the digital-to-analog converter 302 allows for a wide range of threshold voltages to be selected for each event, which allows the overvoltage / undervoltage protection circuit 300 to be used in various applications and can reduce power consumption and circuit area.

[0024] The maximum detection time for each event may vary depending on the potential impact of the event. For example, overvoltage / undervoltage protection circuit 300 may need to detect an overvoltage fault event within 200 nanoseconds (ns) of onset, an overvoltage warning event within 400 ns of onset, and an undervoltage warning or undervoltage fault within 800 ns of onset. Thus, the operating speed of state machine 308 is determined by the maximum detection time for the overvoltage fault event. To meet the 200-ns detection time, state machine 308 changes state every 50 ns. That is, the time from onset to completion for each state of state machine 308 does not exceed 50 ns. Thus, digital-to-analog converter 302 and comparator 304 are configured to settle within 50 ns, and implementations of digital-to-analog converter 302 and comparator 304 that provide such performance may require a large amount of circuit area and consume a large amount of power.

[0025] Figure 5 Schematic diagram showing overvoltage / undervoltage protection circuit 500 using a state machine that determines the priority order of overvoltage fault detection. Overvoltage / undervoltage protection circuit 500 includes digital-to-analog converter 502, comparator 504, and control circuit 506. Digital-to-analog converter 502 is coupled to comparator 504 and provides threshold voltage 510 to comparator 504 for comparison with input voltage 516. The result 522 of the comparison is provided to control circuit 506. Control circuit 506 applies the result 522 to select state transitions as described below. Digital-to-analog converter 502 may include an R-2R resistor ladder. Control circuit 506 is coupled to digital-to-analog converter 502 and provides threshold 512 to digital-to-analog converter 502. Digital-to-analog converter 502 converts threshold 512 into threshold voltage 510. Input 504A of comparator 504 is coupled to output 502A of digital-to-analog converter 502. Output 504C of comparator 504 is coupled to input 506B of control circuit 506. Output 506A of control circuit 506 is coupled to input 502B of digital-to-analog converter 502.

[0026] Control circuit 506 includes state machine circuit 508. State machine circuit 508 sets threshold 512 provided to digital-to-analog converter 502. Figure 6A state diagram 600 showing the operation of the state machine circuit 508 is shown. The state diagram 600 shows that the state machine circuit 508 prioritizes overvoltage fault detection over overvoltage warning events, undervoltage warning events, or undervoltage fault events. In the state diagram 600, at each state 602-608, if the voltage at input 504B of comparator 504 exceeds the threshold voltage 510 at input 504A of comparator 504 (as indicated by result 522), the state diagram 600 transitions to state 602. Thus, if VIN exceeds the applied threshold voltage 510 in any state, the control circuit 506 returns to state 602 to check for an overvoltage fault event. By determining the priority order of overvoltage fault detection, the control circuit 506 is able to meet the maximum overvoltage fault event detection specification of 200 ns while increasing the time spent in each state to 100 ns, thereby allowing relaxation of the design requirements (e.g., propagation / stabilization time requirements) of the digital-to-analog converter 502 and comparator 504.

[0027] In state 602 (Overvoltage Fault Detection State (OVF)), the threshold 512 sets the digital-to-analog converter 502 to generate a threshold voltage 510 as the overvoltage fault threshold, and the overvoltage / undervoltage protection circuit 500 checks for an overvoltage fault event. If the input voltage 516 exceeds the threshold voltage 510, the state machine circuit 508 remains in state 602. If the input voltage 516 is less than the threshold voltage 510, the state machine circuit 508 transitions from state 602 to state 604. In state 604 (Overvoltage Warning Detection State (OVW)), the control circuit 506 sets the digital-to-analog converter 502 to generate a threshold voltage 510 as the overvoltage warning threshold (overvoltage fault threshold > overvoltage warning threshold), and the overvoltage / undervoltage protection circuit 500 checks for an overvoltage warning event. If the input voltage 516 exceeds the threshold voltage 510, the state machine circuit 508 transitions from state 604 to state 602. If the input voltage 516 is less than the threshold voltage 510, the state machine circuit 508 transitions from state 604 to state 606. In state 606 (Undervoltage Warning Detection State (UVW)), the control circuit 506 sets the digital-to-analog converter 502 to generate a threshold voltage 510 as the undervoltage warning threshold (overvoltage warning threshold > undervoltage warning threshold), and the overvoltage / undervoltage protection circuit 500 checks for an undervoltage warning event. If the input voltage 516 exceeds the threshold voltage 510, the state machine circuit 508 transitions from state 606 to state 602. If the input voltage 516 is less than the threshold voltage 510, the state machine circuit 508 transitions from state 606 to state 608. In state 608 (Undervoltage Fault Detection State (UVF)), the control circuit 506 sets the digital-to-analog converter 502 to generate a threshold voltage 510 as the undervoltage fault threshold (undervoltage warning threshold > undervoltage fault threshold), and the overvoltage / undervoltage protection circuit 500 checks for an undervoltage fault event. If the input voltage 516 exceeds the threshold voltage 510, the state machine circuit 508 transitions from state 608 to state 602. If the input voltage 516 is less than the threshold voltage 510, the state machine circuit 508 remains in state 608.

[0028] Some embodiments of the overvoltage / undervoltage protection circuit 500 may allow for the selective masking of states 602 - 608 to further reduce the detection time. For example, the overvoltage / undervoltage protection circuit 500 may be configured to skip or bypass one or more of states 602 - 608 to reduce the overall detection time across all unmasked states.

[0029] The overvoltage / undervoltage protection circuit 500 may further include a multiplexer 514 coupled to the comparator 504. The multiplexer 514 selects the input signal VIN or the trimmed reference voltage 518 to provide to the comparator 504. The multiplexer 514 includes a selection input terminal 514D that is coupled to the calibration output terminal 506C of the control circuit 506. The multiplexer 514 includes an output 514A coupled to the input 504B of the comparator 504, an input 514B coupled to the voltage input terminal 520, and an input 514C coupled to the reference voltage source. During power-up initialization or at a user-selected calibration time, the control circuit 506 activates the calibration signal 524 and applies the trimmed reference voltage 518 to calibrate the offset and gain errors caused by aging, process variations, or other factors. For example, the offset is determined by identifying the input to the digital-to-analog converter 502 that produces an output closest to the known trimmed reference voltage 518, where the difference between the voltage nominally produced by the input value of the digital-to-analog converter 502 and the trimmed reference voltage 518 is the offset. The control circuit 506 compensates for the offset measured in the overvoltage / undervoltage detection. This calibration allows for the relaxation of the specifications of the comparator 504.

[0030] Compared with the overvoltage / undervoltage protection circuit 100, the overvoltage / undervoltage protection circuit 200, and the overvoltage / undervoltage protection circuit 300, the overvoltage / undervoltage protection circuit 500 provides many advantages. The overvoltage / undervoltage protection circuit 500 allows any value that the digital-to-analog converter 502 can produce to be used as the threshold for detecting any overvoltage / undervoltage event, which expands the number of applications in which the overvoltage / undervoltage protection circuit 500 can be used and allows for a reduction in circuit complexity and power consumption. For example, the overvoltage / undervoltage protection circuit 500 provides the resolution and range for overvoltage / undervoltage detection that would require four comparators and hundreds of switches in the overvoltage / undervoltage protection circuit 200. The calibration capability provided by the overvoltage / undervoltage protection circuit 500 can improve the accuracy of overvoltage / undervoltage detection while allowing the use of a less complex comparator.

[0031] Figure 7 Illustrates the operation of the overvoltage / undervoltage protection circuit 500. During period 710, the input voltage 516 is greater than the undervoltage warning threshold 704 and less than the overvoltage warning threshold 706. Since the input voltage 516 is greater than the undervoltage warning threshold 704, the state machine circuit 508 transitions from state 602 to state 604, transitions to state 606, and then back to state 602.

[0032] During period 712, the input voltage 516 is greater than the overvoltage warning threshold 706 and less than the overvoltage fault threshold 708. Since the input voltage 516 is greater than the overvoltage warning threshold 706, the state machine circuit 508 transitions from state 602 to state 604 and then back to state 602.

[0033] During time period 714, the input voltage 516 is greater than the overvoltage fault threshold 708. Since the input voltage 516 is greater than the overvoltage fault threshold 708, the state machine circuit 508 remains in state 602.

[0034] During time period 716, the input voltage 516 is greater than the undervoltage fault threshold 702 and less than the undervoltage warning threshold 704. Since the input voltage 516 is greater than the undervoltage fault threshold 702, the state machine circuit 508 transitions from state 602 to state 604, transitions to state 606, transitions to state 608, and transitions back to state 602.

[0035] During time period 718, the input voltage 516 is less than the undervoltage fault threshold 702. Since the input voltage 516 is less than the undervoltage fault threshold 702, the state machine circuit 508 transitions from state 602 to state 604, transitions to state 606, transitions to state 608 and remains in state 608.

[0036] Figure 8 A flowchart of a method 800 for overvoltage / undervoltage protection that determines the priority order of overvoltage fault detection is shown. Although described sequentially for convenience, at least some of the actions shown may be performed in a different order and / or in parallel. Additionally, some embodiments may perform only certain of the actions shown. The operations of method 800 may be performed by an embodiment of the overvoltage / undervoltage protection circuit 500.

[0037] In module 802, the control circuit 506 sets the digital-to-analog converter 502 to generate a threshold voltage 510 for detecting an overvoltage fault.

[0038] In module 804, the comparator 504 compares the threshold voltage 510 with the input voltage 516. If the input voltage 516 is greater than the threshold voltage 510, the control circuit 506 issues a signal for an overvoltage fault in module 806, and method 800 continues to operate in module 802.

[0039] If the input voltage 516 is not greater than the threshold voltage 510 in module 804, the control circuit 506 sets the digital-to-analog converter 502 to generate a threshold voltage 510 for detecting an overvoltage warning in module 808.

[0040] In module 810, the comparator 504 compares the threshold voltage 510 with the input voltage 516. If the input voltage 516 is greater than the threshold voltage 510, the control circuit 506 issues a signal for an overvoltage warning in module 812, and method 800 continues to operate in module 802.

[0041] If the input voltage 516 is not greater than the threshold voltage 510 in module 810, the control circuit 506 sets the digital-to-analog converter 502 in module 814 to generate the threshold voltage 510 for detecting an undervoltage warning.

[0042] In module 816, the comparator 504 compares the threshold voltage 510 with the input voltage 516. If the input voltage 516 is greater than the threshold voltage 510, the method 800 continues operating in module 802.

[0043] If the input voltage 516 is not greater than the threshold voltage 510 in module 816, the control circuit 506 issues a signal for an undervoltage warning in module 818.

[0044] In module 820, the control circuit 506 sets the digital-to-analog converter 502 to generate the threshold voltage 510 for detecting an undervoltage fault.

[0045] In module 822, the comparator 504 compares the threshold voltage 510 with the input voltage 516. If the input voltage 516 is greater than the threshold voltage 510, the method 800 continues operating in module 802.

[0046] If the input voltage 516 is not greater than the threshold voltage 510 in module 816, the control circuit 506 issues a signal for an undervoltage fault in module 824, and the method 800 continues in module 820.

[0047] Because the method 800 implemented by the overvoltage / undervoltage protection circuit 500 uses a single digital-to-analog converter 502 and comparator 504 to detect all overvoltage / undervoltage events, and the digital-to-analog converter 502 allows a wide range of threshold voltages to be selected for each event, the overvoltage / undervoltage protection circuit 500 can be used in various applications with different ranges and resolutions. Relative to circuits such as the overvoltage / undervoltage protection circuit 200, the use of a single digital-to-analog converter and comparator reduces power consumption and circuit area. The calibration of the trimmed reference provided by the overvoltage / undervoltage protection circuit 500 allows design specifications to be relaxed and detection accuracy to be improved. The prioritization of overvoltage faults as implemented in the method 800 allows the state timing of the overvoltage / undervoltage protection circuit 500 to be relaxed, which reduces power consumption and simplifies circuit design.

[0048] Figure 9A block diagram of a computer system 900 including overvoltage / undervoltage protection in accordance with the present specification is shown. The computer system 900 may be embodied in a server motherboard or other computer implementation. The computer system 900 includes a processor 902, a power supply 904, and an overvoltage / undervoltage protection circuit 906. The overvoltage / undervoltage protection circuit 906 is an implementation of the overvoltage / undervoltage protection circuit 500. The processor 902 is a general-purpose microprocessor, an image processor, a digital signal processor, or other electronic device that executes instructions to implement functions. The power supply 904 generates a voltage to power the processor 902. The power supply 904 may be a multi-phase buck converter or other switching power supply circuit configured to power the processor 902. In some implementations of the computer system 900, the power supply 904 may generate multiple voltages.

[0049] As described herein, the overvoltage / undervoltage protection circuit 906 compares the voltage generated by the power supply 904 with one or more thresholds to detect overvoltage / undervoltage events. To protect the processor 902, when an overvoltage / undervoltage event is detected, the overvoltage / undervoltage protection circuit 906 may signal the power supply 904 to adjust the voltage provided to the processor 902, and / or may signal the processor 902 to inform the processor 902 of the event. In some implementations of the computer system 900, the overvoltage / undervoltage protection circuit 906 may be incorporated into the power supply 904. For example, the overvoltage / undervoltage protection circuit 906 may be incorporated into the power supply controller of the power supply 904.

[0050] Because the overvoltage / undervoltage protection circuit 906 provides reduced power consumption and circuit area relative to other overvoltage / undervoltage protection circuit implementations, the overall circuit area and cost of the computer system 900 may be reduced relative to other implementations. Additionally, because the overvoltage / undervoltage protection circuit 906 includes calibration for a trimmed reference, the accuracy of overvoltage / undervoltage event detection is improved relative to other implementations, which in turn better protects the processor 902 from damage or malfunction caused by overvoltage / undervoltage events.

[0051] Within the scope of the claims, modifications in the described embodiments are possible, and other embodiments are possible.

Claims

1. An overvoltage / undervoltage protection circuit, comprising: A digital-to-analog converter; A comparator, comprising: A first input coupled to the output of the digital-to-analog converter; and A second input configured to receive an input voltage; and A control circuit, comprising: An output coupled to the input of the digital-to-analog converter; and An input coupled to the output of the comparator; Wherein the control circuit is configured to set the digital-to-analog converter to output an overvoltage fault threshold in response to the output of the comparator indicating that the input voltage exceeds any one of at least three different thresholds, one of the at least three different thresholds being currently output by the digital-to-analog converter, wherein: The thresholds include an overvoltage warning threshold, an undervoltage warning threshold, and an undervoltage fault threshold; The overvoltage fault threshold is greater than the overvoltage warning threshold; The overvoltage warning threshold is greater than the undervoltage warning threshold; and The undervoltage warning threshold is greater than the undervoltage fault threshold.

2. The overvoltage / undervoltage protection circuit according to claim 1, wherein the control circuit is configured to set the digital-to-analog converter to output an overvoltage warning threshold in response to the input voltage being less than the overvoltage fault threshold.

3. The overvoltage / undervoltage protection circuit according to claim 1, wherein the control circuit is configured to set the digital-to-analog converter to output an undervoltage warning threshold in response to the input voltage being less than the overvoltage warning threshold.

4. The overvoltage / undervoltage protection circuit according to claim 1, wherein the control circuit is configured to set the digital-to-analog converter to output an undervoltage fault threshold in response to the input voltage being less than the undervoltage warning threshold.

5. The overvoltage / undervoltage protection circuit according to claim 1, further comprising a multiplexer, the multiplexer comprising: A first input coupled to the voltage input terminal of the overvoltage / undervoltage protection circuit; A second input coupled to a reference voltage source; And An output coupled to the second input of the comparator.

6. A control circuit, comprising: A state machine circuit configured to: Transition from an overvoltage warning detection state to an overvoltage fault detection state in response to receiving a signal indicating that the input voltage exceeds the overvoltage warning threshold; Transition from an undervoltage warning detection state to the overvoltage fault detection state in response to the signal indicating that the input voltage exceeds the undervoltage warning threshold; And Transition from an undervoltage fault detection state to the overvoltage fault detection state in response to the signal indicating that the input voltage exceeds the undervoltage fault threshold; Wherein the overvoltage warning threshold represents a higher voltage than the undervoltage warning threshold, and the undervoltage warning threshold represents a higher voltage than the undervoltage fault threshold.

7. The control circuit according to claim 6, wherein: The overvoltage fault threshold is greater than the overvoltage warning threshold; The overvoltage warning threshold is greater than the undervoltage warning threshold; and The undervoltage warning threshold is greater than the undervoltage fault threshold.

8. The control circuit according to claim 6, wherein the state machine circuit is configured to transition from an overvoltage fault detection state to the overvoltage warning detection state in response to the signal indicating that the input voltage is less than the overvoltage warning threshold.

9. The control circuit according to claim 6, wherein the state machine circuit is configured to transition from the overvoltage warning detection state to the undervoltage warning detection state in response to the signal indicating that the input voltage is less than the overvoltage warning threshold.

10. The control circuit according to claim 6, wherein the state machine circuit is configured to transition from the undervoltage warning detection state to the undervoltage fault detection state in response to the signal indicating that the input voltage is less than the undervoltage warning threshold.

11. The control circuit according to claim 6, wherein the state machine circuit is configured to remain in the undervoltage fault detection state in response to the signal indicating that the input voltage is less than the undervoltage fault threshold.

12. The control circuit according to claim 6, wherein the state machine circuit is configured to remain in the overvoltage fault detection state in response to the signal indicating that the input voltage exceeds the overvoltage fault threshold.

13. A method, comprising: comparing an input voltage with a threshold voltage generated by a digital-to-analog converter; setting the digital-to-analog converter to generate an overvoltage fault threshold in response to the input voltage exceeding the threshold voltage and the threshold voltage being the overvoltage warning threshold; setting the digital-to-analog converter to generate the overvoltage fault threshold in response to the input voltage exceeding the threshold voltage and the threshold voltage being the undervoltage warning threshold; and setting the digital-to-analog converter to generate the overvoltage fault threshold in response to the input voltage exceeding the threshold voltage and the threshold voltage being the undervoltage fault threshold; wherein: the overvoltage fault threshold is greater than the overvoltage warning threshold; the overvoltage warning threshold is greater than the undervoltage warning threshold; and the undervoltage warning threshold is greater than the undervoltage fault threshold.

14. The method according to claim 13, further comprising: Setting the digital-to-analog converter to generate the overvoltage warning threshold in response to the input voltage being less than the overvoltage fault threshold.

15. The method according to claim 13, further comprising: Setting the digital-to-analog converter to generate the undervoltage warning threshold in response to the input voltage being less than the overvoltage warning threshold.

16. The method according to claim 13, further comprising: Setting the digital-to-analog converter to generate the undervoltage fault threshold in response to the input voltage being less than the undervoltage warning threshold.

17. A system, comprising: a processor; a power supply coupled to the processor; and an overvoltage / undervoltage protection circuit coupled to the processor and the power supply, and the overvoltage / undervoltage protection circuit includes: a digital-to-analog converter; a comparator, comprising: a first input coupled to the output of the digital-to-analog converter; and a second input coupled to the output of the power supply; and a control circuit, comprising: an output coupled to the input of the digital-to-analog converter; and an input coupled to the output of the comparator; wherein the control circuit is configured to: set the digital-to-analog converter to provide an overvoltage fault threshold in response to the input voltage at the second input of the comparator exceeding the overvoltage warning threshold at the first input of the comparator; set the digital-to-analog converter to provide the overvoltage fault threshold in response to the input voltage at the second input of the comparator exceeding the undervoltage warning threshold at the first input of the comparator; and In response to the input voltage at the second input of the comparator exceeding the undervoltage fault threshold at the first input of the comparator, set the digital-to-analog converter to provide the overvoltage fault threshold; wherein: the overvoltage fault threshold is greater than the overvoltage warning threshold; the overvoltage warning threshold is greater than the undervoltage warning threshold; and the undervoltage warning threshold is greater than the undervoltage fault threshold.

18. The system according to claim 17, wherein the control circuit is configured to set the digital-to-analog converter to provide the overvoltage warning threshold in response to the input voltage being less than the overvoltage fault threshold.

19. The system according to claim 17, wherein the control circuit is configured to set the digital-to-analog converter to provide the undervoltage warning threshold in response to the input voltage being less than the overvoltage warning threshold.

20. The system according to claim 17, wherein the control circuit is configured to set the digital-to-analog converter to provide the undervoltage fault threshold in response to the input voltage being less than the undervoltage warning threshold.

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