Method and apparatus for determining time-varying limitations of a power source

• US 9,075,086 B2
• Filed: 05/24/2013
• Issued: 07/07/2015
• Est. Priority Date: 05/24/2013
• Status: Active Grant

• Current Assignee: Semtech Corporation
• Original Assignee: Sierra Wireless Incorporated
• Inventors: Seveau, Christophe, Au-Yeung, Lik King
• Primary Examiner(s): Nguyen, Hai L
• Application Number:
  US13/901,838
• Publication Number:
  US 20140347100A1
• Time in Patent Office: 774 Days
• Field of Search: 327/50, 327/63, 327/64
• US Class Current: 1/1
• CPC Class Codes: B60R 16/03 for supply of electrical power to vehicle subsystems or for circuit arrangements for charging batteries H02J7/00
• CPC Class Codes: G01R 19/0038 Circuits for comparing several input signals and for indicating the result of this comparison, e.g. equal, different, greater, smaller (comparing pulses or pulse trains according to amplitude)
• CPC Class Codes: G06F 1/26 Power supply means, e.g. regulation thereof for memories G11C
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/92 Energy efficient charging or discharging systems for batteries, ultracapacitors, supercapacitors or double-layer capacitors specially adapted for vehicles

Abstract

A low-power method and apparatus is provided for adapting to time-varying limitations of a power source, such as a vehicle power source which is in a more-limited state when the engine is off. The supply voltage is monitored for changes using an unclocked, low-power first stage having an analog section, a voltage comparator. Upon detecting voltage changes reflective of a potential power source state change, the first stage generates an interrupt. In response, a second stage transitions from a low-power standby mode to a higher-power active mode. The second stage may include a microprocessor and is configured to confirm or disconfirm the state change. Upon confirmation, further operations are triggered. Upon disconfirmation, the second stage returns to standby mode. The first stage may include an operational amplifier whose two inputs are indicative of the supply voltage, one input having a different response rate to voltage variations than the other.

Claims

1. An apparatus for use in adapting to time-varying limitations of a power source, the apparatus comprising a first stage circuit including:

a.) an input terminal for operative coupling to a supply voltage provided by the power source;

b.) an analog electronics section configured to concurrently generate a first intermediate signal indicative of the supply voltage and a second intermediate signal indicative of the supply voltage, wherein the first intermediate signal responds at a first rate to variation in the supply voltage and the second intermediate signal responds at a second rate to variation in the supply voltage, the second rate different from the first rate;

c.) a comparator section configured to compare the first intermediate signal and the second intermediate signal and to output a change detect signal upon detecting at least a predetermined difference between the first intermediate signal and the second intermediate signal, said difference indicative of a possible change in limitations of the power source;

d.) an output configured to provide an output signal indicative of the change detect signal; and

e.) a second stage circuit configured to operate in an active mode and a standby mode, the second stage circuit configured, in response to the output signal, to;

switch from the standby mode to the active mode;

monitor the supply voltage while in the active mode;

confirm or disconfirm the possible change in limitations of the power source while in the active mode;

trigger further electronic operations upon confirming the possible change in limitations; and

return to the lower-power standby mode upon disconfirming the possible change in limitations.

2. The apparatus according to claim 1, wherein the first stage comprises one or more inputs for adjusting responsivity of the first stage, and wherein the second stage further comprises a supervisory module configured to:

monitor for false detection events corresponding to disconfirming the possible change in limitations; and

to adjust said one or more inputs for adjusting responsivity of the first stage in response to said monitored false detection events.

3. The apparatus according to claim 1, further comprising a filtering section operatively coupled to the input terminal and configured to provide a filtered signal indicative of the supply voltage to the analog electronics section, the first intermediate signal indicative of the supply voltage and the second intermediate signal indicative of the supply voltage generated based on the filtered signal indicative of the supply voltage.

4. The apparatus according to claim 1, wherein the comparator section comprises a first sub-section in parallel with a second sub-section, the first sub-section responsive to a reduction in the supply voltage, the second sub-section responsive to an increase in the supply voltage.

5. The apparatus according to claim 1, wherein the first stage circuit draws less than about 240 microamps on average.

6. An apparatus for use in adapting to time-varying limitations of a power source, the apparatus comprising:

a.) an at least partially analog first stage circuit configured to monitor a supply voltage of the power source and to generate an interrupt signal in response to a predetermined amount of change in the monitored supply voltage, said change indicative of a possible change in limitations of the power source;

b.) a second stage circuit operable in a lower-power standby mode and a higher-power active mode, the second stage circuit configured, in response to the interrupt signal, to;

switch from the standby mode to the active mode;

monitor the supply voltage while in the active mode;

confirm or disconfirm the possible change in limitations of the power source while in the active mode;

trigger further electronic operations upon confirming the possible change in limitations; and

return to the lower-power standby mode upon disconfirming the possible change in limitations.

7. The apparatus according to claim 6, wherein the second stage circuit comprises a microprocessor used in monitoring the supply voltage and confirming or disconfirming the possible change in limitations, and wherein the microprocessor is used in performing said further electronic operations.

8. The apparatus according to claim 7, wherein said further electronic operations comprise one or more of:

location monitoring, location reporting, wireless communication, data collection, data logging, and user interface operations.

9. A method for facilitating adapting to time-varying limitations of a power source, the method comprising:

a.) receiving a supply voltage provided by the power source;

b.) concurrently generating a first intermediate signal indicative of the supply voltage and a second intermediate signal indicative of the supply voltage using an analog electronics section, wherein the first intermediate signal responds at a first rate to variation in the supply voltage and the second intermediate signal responds at a second rate to variation in the supply voltage, the second rate different from the first rate;

c.) using a comparator electronics section, comparing the first intermediate signal and the second intermediate signal and providing a change detect signal upon detecting at least a predetermined difference between the first intermediate signal and the second intermediate signal, said difference indicative of a possible change in limitations of the power source;

d.) providing an output signal indicative of the change detect signal; and

e.) in response to receipt of the output signal;

switching a second stage circuit from a standby mode to an active mode;

monitoring the supply voltage using the second stage circuit while in the active mode;

confirming or disconfirming the possible change in limitations of the power source using the second stage circuit while in the active mode;

triggering further electronic operations upon confirming the possible change in limitations; and

returning to the lower-power standby mode upon disconfirming the possible change in limitations.

10. The method according to claim 9, further comprising monitoring for false detection events corresponding to disconfirming the possible change in limitations;

and adjust one or both of the analog electronics section and the comparator electronics section in response to said monitored false detection events.

11. The method according to claim 9, further comprising providing a filtered signal indicative of the supply voltage to the analog electronics section, the first intermediate signal indicative of the supply voltage and the second intermediate signal indicative of the supply voltage generated based on the filtered signal indicative of the supply voltage.

12. A method for facilitating adapting to time-varying limitations of a power source, the method comprising:

a.) monitoring a supply voltage of the power source and generating an interrupt signal in response to a predetermined amount of change in the monitored supply voltage, said change indicative of a possible change in limitations of the power source, wherein said monitoring and generating is performed using circuitry configured as at least partially analog;

b.) in response to generation of the interrupt signal;

switching a second stage circuit from a standby mode to an active mode;

monitoring the supply voltage using the second stage circuit while in the active mode;

confirming or disconfirming the possible change in limitations of the power source using the second stage circuit while in the active mode;

triggering further electronic operations upon confirming the possible change in limitations; and

returning the second stage circuit to the lower-power standby mode upon disconfirming the possible change in limitations.

13. The method according to claim 12, wherein the second stage circuit comprises a microprocessor used in monitoring the supply voltage and confirming or disconfirming the possible change in limitations, and wherein the microprocessor is used in performing said further electronic operations.

14. The method according to claim 13, wherein said further electronic operations comprise one or more of:

location monitoring, location reporting, wireless communication, data collection, data logging, and user interface operations.