Voltage sequencing circuit for powering-up sensitive electrical components

[0002] This application is a continuation of Application No. 09/729,239, filed Dec. 5, 2000, which issued as U.S. Pat. No. 6,333,650 on Dec. 25, 2001.

[0003] A. Field of the Invention

[0004] The present invention relates generally to power systems and, more particularly, to the initial application of power to electrical systems.

[0005] B. Description of Related Art

[0006] In certain electrical systems, such as computer and communication systems, different parts of the system may be designed to be powered from different power sources. For example, a computer system may include a first component designed to operate with a 1.5 volt source, a second component designed to operate with a 3.3 volt source, and a third component designed to operate with a 10 volt source. Typically, such electrical systems provide the power to each component through a series of regulators that convert power from a main power supply to a power level appropriate for each component. Because each regulator draws from the same main power supply, the different voltages (or currents) supplied to the components are not fully independent of one another. That is, power fluctuations caused by one of the components can affect the power supplied to the other components. This effect can be exacerbated by the fact that the components may be further tied to one another through electrical connections at the signal level.

[0007] Due to this lack of isolation between the components of the electrical system, when initially powering-up each component, it is desirable to sequentially power up each component and wait until the power to the component stabilizes before supplying power to the next component. In this manner, large, potentially damaging power spikes can be avoided. This can be particularly important when dealing with sensitive electronic equipment.

[0008] Conventional sequential power-up circuits were either manually operated by a user or automated through a simple on/off architecture that delayed power to each component using a resistor/capacitor structure. Such circuits can be inadequate for highly sensitive components in modern electrical systems.

[0009] Thus, there is a need in the art to improve power-up sequencing when supplying varying power levels to multiple components in an electrical system.

[0010] Systems and methods consistent with the present invention address this need by providing a reliable power-up sequencing circuit that monitors and sequentially enables power to components in an electrical system.

[0011] In accordance with an aspect of the present invention as embodied and broadly described herein, a voltage sequencing circuit is described that includes multiple elements. These elements include electrical power sources configured to supply power to electrical components having differing power requirements. Additionally, a power monitor connects to the outputs of the electrical power sources to detect failures in the electrical power sources. A decision logic component connects to the electrical power sources and to an output of the power monitor. The decision logic performs a power-up sequence by sequentially enabling the electrical power sources and verifying, based on outputs from the power monitor, that an enabled one of the electrical power sources is stable before enabling a next one of the electrical power sources.

[0012] A method consistent with another aspect of the present invention provides power-up services to an electrical system from multiple different power sources. The method includes: (a) enabling a first of the power sources to source power to the electrical system; (b) waiting a predetermined period for the power from the first of the power sources to settle; and (c) beginning to monitor an output of the first of the power sources for a failure in the sourced power. Additionally, (a), (b) and (c) are repeated for each additional power source, and all of the power sources are disabled when any of the monitored power sources fail.

[0013] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an embodiment of the invention and, together with the description, explain the invention. In the drawings,

[0014] FIG. 1 is a block diagram of a system, including a voltage sequencing circuit consistent with an aspect of the present invention;

[0015] FIG. 2 is a flow chart illustrating methods consistent with the present invention for powering-up an electrical system; and

[0016] FIG. 3 is a timing diagram illustrating the interaction of various signal lines shown in FIG. 1.

[0017] The following detailed description of the invention refers to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. Also, the following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims and equivalents.

[0018] As described herein, a voltage sequencer reliably powers-up electrical systems requiring multiple voltage levels. Control sequencing logic within the voltage sequencer monitors power sources at the output of a number of power regulators and determines when to enable each of the power regulators. The delay time between enabling power regulators can be individually set by the system designer.

[0019] FIG. 1 is a block diagram of an electrical system 101 connected to a voltage sequencer 103 that provides power to electrical system 101. Electrical system 101 includes exemplary electrical components, labeled as circuit 110, circuit 111, and circuit 112. As illustrated by communication paths 113, circuits 110-112 may communicate with or otherwise be electrically coupled to one another.

[0020] Electrical system 101 may be any type of electronic device that requires a sequential power-up from multiple power levels. A high performance network switch or router is one possible example of an implementation of electrical system 101. Voltage sequencer 103 provides power to circuits 110-112 in electrical system 101, and generally includes power regulators 120-122 and control sequence component 123. Power regulator 120 provides power to circuit 110, power regulator 121 provides power to circuit 111, and power regulator 122 provides power to circuit 112. Each of power regulators 120-122 may receive their input power from a main power supply source 130. As illustrated, power regulator 120 converts power from power source 130 into a 3 volt DC output, power regulator 121 converts power from power source 130 into a 5 volt DC output, and power regulator 122 converts power from power source 130 into a 10 volt DC output.

[0021] Control sequencing component 123 monitors and controls regulators 120-122. In particular, control sequencing logic 123 includes monitor circuits 127, which are each connected to the output of one of regulators 120-122 through monitor signal lines 128. Each of monitor circuits 127 continuously monitors its input signal line 128 and signals decision logic 129 when the power on its line fails. A power failure may be triggered by, for example, a complete loss of the power, a power spike that exceeds a preset threshold, or an abnormal power drop off.

[0022] Decision logic 129 of control sequencing component 123 decides, based on signals from monitor circuits 127, whether to activate enable signal lines 126. When one of enable signal lines 126 is activated, the corresponding power regulator is “enabled,” and will source power to electrical system 101. When the enable signal line 126 is not activated, the corresponding power regulator is disabled, and stops transmitting power to electrical system 101.

[0023] Voltage sequencer 103 may also include components that provide visual feedback to a user, such as light emitting diode (LED) 140. As shown, LED 140 is controlled by control sequencing component 123. Control sequencing component 123 may additionally provide electrical feedback to other system components, such as control component 135, as to the result of a power-up sequence. Control component 135 may also initiate a power-up sequence. Although shown external to electrical system 101, control component 135 may be a part of electrical system 101.

[0024] Although monitor circuits 127 are shown as multiple separate circuits in FIG. 1, one of ordinary skill in the art will recognize that monitor circuits 127 may be implemented as a single circuit.

[0025] FIG. 2 is a flow chart illustrating methods performed by voltage sequencer 103 in powering-up electrical system 101.

[0026] To begin a power-up sequence, decision logic 129 holds each of the enable signals 126 in their disabled state. Accordingly, at this point, no power is transmitted to electrical system 101 from voltage sequencer 103. After V_inis applied for the main power source 130, decision logic 129 waits a preset time period (e.g., one second) for V_into settle. (Act 201).

[0027] When V_inhas settled, decision logic 129 activates the enable signal line 126 corresponding to the first power regulator 120. (Act 202). In response, the power regulator begins to apply power to the circuits in electrical system 101 that are connected to the power regulator (i.e., circuit 110). Decision logic 129 waits a preset time period for the newly supplied power to settle and for the supplied circuit 110 to stabilize. (Act 203). This time period may be individually set for each power regulator by storing the time period for each power regulator in a memory in control sequencing component 123. In this manner, the designer can easily adjust settle times based on requirements of the particular power regulator and the circuits in the electrical system 101.

[0028] After the preset wait time, if the monitor circuit 127 corresponding to the enabled power regulator 120 indicates that the newly supplied power has settled, decision logic 129 enables the next power regulator in the sequence (e.g., power regulator 121). (Acts 204, 206, and 207). Additionally, the monitor circuit begins to constantly monitor the power regulator that was turned on. (Acts 205 and 211). If any of the monitor circuits 127 for the turned on power regulators detect an error, or if the power from a regulator has not settled after the designated time, control sequence component 123 initiates a failure operation by disabling the power regulators 120-122 via de-assertion of the enable signal lines 126. (Acts 204, 205, 208, and 211). Control sequence component 123 may then reinitiate a power-up sequence, beginning at Act 202. (Act 209).

[0029] When all the circuits in the electrical system 101 have been successfully powered-up, voltage sequencer 103 may display a visual indication of the successful power up, such as by activating a light emitting diode. (Act 210)

[0030] To increase the linearity of the power-up sequence and to decrease power fluctuations, V₁, through V_nin voltage sequencer 103 may be arranged so that either the powered-up voltages sequentially increase (as illustrated) or sequentially decrease.

[0031] FIG. 3 is a timing diagram illustrating the interaction of various signals shown in FIG. 1.

[0032] As illustrated, V_inis activated at time t1. After a preset time period, decision logic 129 activates the enable signal line corresponding to voltage V1 (labeled as V1_en at time t2), which causes the power regulator 120 to begin to source voltage V1. As shown in FIG. 3, voltage V1, when turned on, may be increased gradually in a ramp fashion to decrease the chance that circuit 110 will be adversely affected by the power surge. At time t3, decision logic 129 checks the result of the monitor circuit 127 (labeled as V1_fail). As shown, V1_fail is at a low logic level, indicating that V1 is stable.

[0033] Voltage sequencer 103 repeats a similar sequence for voltage V2. More specifically, at time t3, V2_en is asserted, which turns on voltage V2. At time t4, decision logic 129 checks the result of the monitor circuit 127 (labeled as V2_fail). Because V2_fail indicates that V2 is also stable, the process continues. When voltage sequencer 103 successfully gets to the last power regulator (labeled as voltage V9), it may activate the LED 140 by activating the “Led_ok” signal line, which produces a visual indication that electrical system 101 has successfully powered-up.

[0034] If the power-up sequence repeatedly fails, voltage sequencer 103 may, after a number of attempts, completely abort the power-up sequence. In this situation, voltage sequencer 103 may identify the failing power regulators to a user for problem-solving purposes.

[0035] The foregoing description of preferred embodiments of the present invention provides illustration and description, but is not intended to be exhaustive or to limit the invention to the precise form disclosed. Modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention.

[0036] Although described as being primarily implemented in hardware, the present invention may be embodied in hardware and/or in software (including firmware, resident software, micro-code, etc.). Furthermore, the present invention may take the form of a computer program product on a computer-usable or computer-readable storage medium having computer-usable or computer-readable program code embodied in the medium for use by or in connection with an instruction execution system.

[0037] The scope of the invention is defined by the claims and their equivalents.