Method of controlling battery back-up for multiple power supplies

• US 6,181,029 B1
• Filed: 11/06/1998
• Issued: 01/30/2001
• Est. Priority Date: 11/06/1998
• Status: Expired due to Term

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Egan, Patrick K., Swenson, John V., Berglund, Neil C., Steele, Steven W.
• Primary Examiner(s): FLEMING, FRITZ M
• Application Number:
  US09/187,067
• Time in Patent Office: 816 Days
• Field of Search: 307/18, 307/23, 307/29, 307/43, 307/46, 307/48, 307/64-66, 307/72, 307/80, 307/85-87, 323/234, 323/282, 323/285, 363/74, 363/78, 363/84
• US Class Current: 307/66
• CPC Class Codes: H02J 9/062 for AC powered loads
• CPC Class Codes: H02M 1/007 Plural converter units in cascade push-pull DC/DC converters with pre-regulator H02M3/3374; DC-AC converters following a DC-DC stage including a high frequency transformer H02M7/4807; DC-AC converters following a DC-DC conversion stage generating periodically varying voltages H02M7/4826
• CPC Class Codes: H02M 1/008 Plural converter units for generating at two or more independent and non-parallel outputs, e.g. systems with plural point of load switching regulators
• CPC Class Codes: H02M 1/4225 using a non-isolated boost converter
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

A power system includes a battery back-up unit (BBU) having back-up battery circuitry which provides battery back-up support for a plurality of power supplies each having a respective power factor correction circuit front-end with a boost stage. The voltages output from the boost stages of the power supplies are monitored and compared with respective reference threshold voltages to derive a signal which is used to bring battery back-up power on-line when a monitored voltage falls below a threshold voltage, which may be indicative of a loss of AC mains input voltage. AC mains input voltage is also monitored to detect a restoration and disconnect the battery back-up power. In the event that battery back-up is brought on-line due to a faulty power supply rather than a loss of AC mains input voltage, the faulty power supply can be masked and reported for repair.

Claims

1. In a power system, having a battery back-up unit including battery back-up circuitry and at least one battery which can be selectively connected to an output of the battery back-up unit, the power system further having a plurality of power supplies, each power supply being connected to the output of the battery back-up unit, and each power supply having a front end section including a power factor correction circuit with a boost stage providing an output voltage, a method of controlling battery back-up comprising:

monitoring respective boost stage output voltages of the plurality of power supplies by comparing each of the boost stage output voltages of the plurality of power supplies with a respective reference threshold voltage; and

when the monitoring indicates a respective boost stage output voltage is lower than the respective reference threshold voltage, signaling the battery back-up circuit and providing battery power to the plurality of power supplies by connecting the battery back-up circuitry to the output of the battery back-up unit.

2. The method according to claim 1, further comprising:

signaling a fault of a respective power supply when the monitoring indicates a respective boost stage output voltage is lower than the respective reference threshold voltage after the battery back-up circuit has been brought on-line.

3. The method according to claim 1, further comprising:

sensing a line voltage input to the battery back-up unit; and

if the sensed line voltage input is at or above the line voltage threshold level, and the battery back-up circuitry is connected to the output of the battery back-up unit, then signaling the battery back-up circuit to disconnect the battery back-up circuitry from the output of the battery back-up unit.

4. In a power system, having a battery back-up unit including battery back-up circuitry and at least one battery which can be selectively connected to an output of the battery back-up unit, the power system further having a plurality of power supplies, each power supply being connected to the output of the battery back-up unit, each power supply having a front end section including a power factor correction circuit with a boost stage providing an output voltage, wherein the power system has an interface to a power control network, a method of controlling battery back-up comprising:

monitoring respective boost stage output voltages of the plurality of power supplies by comparing each of the boost stage output voltages of the plurality of power supplies with a respective reference threshold voltage;

when the monitoring indicates a respective boost stage output voltage is lower than the respective reference threshold voltage, signaling the battery back-up circuit and providing battery power to the plurality of power supplies by connecting the battery back-up circuitry to the output of the battery back-up unit;

sensing a line voltage input to the battery back-up unit;

if the sensed line voltage input is at or above the line voltage threshold level, and the battery back-up circuitry is connected to the output of the battery back-up unit, then signaling the battery back-up circuit to disconnect the battery back-up circuitry from the output of the battery back-up unit; and

communicating power supply information, including voltage level information, between the power control network and the power system.

5. The method according to claim 4, further comprising:

signaling to the power control network with the battery back-up unit of a fault of a respective power supply when the monitoring indicates a respective boost stage output voltage is lower than the respective reference threshold voltage after the battery back-up circuitry has been connected to the output of the battery back-up unit.

6. The method according to claim 4, wherein the method further comprises performing the following with the power control network:

detecting the plurality of power supplies and their operating conditions;

enabling the monitoring for power supplies that are detected to be operational; and

enabling the providing of battery power.

7. In a power system, having a battery back-up unit including battery back-up circuitry and at least one battery which can be selectively connected to an output of the battery back-up unit, the power system further having a plurality of power supplies, each power supply being connected to the output of the battery back-up unit, each power supply having a front end section including a power factor correction circuit with a boost stage providing an output voltage, a method of controlling battery back-up comprising:

monitoring respective boost stage output voltages of the plurality of power supplies by comparing each of the boost stage output voltages of the plurality of power supplies with a respective reference threshold voltage;

when the monitoring indicates a respective boost stage output voltage is lower than the respective reference threshold voltage, signaling the battery back-up circuit and providing battery power to the plurality of power supplies by connecting the battery back-up circuitry to the output of the battery back-up unit;

wherein the monitoring comprises providing the reference threshold voltage to a first input of a comparator, providing a boost stage output voltage representation to a second input of a comparator, and providing an output of the comparator to the battery back-up circuitry.

8. The method according to claim 7, wherein the connecting the battery back-up circuitry to the output of the battery back-up unit comprises receiving the output of the comparator, and controlling a battery back-up circuitry switch based on the comparator output.

9. The method according to claim 8, wherein the controlling the battery back-up circuitry switch further comprises sensing a line voltage input to the battery back-up unit, and controlling the battery back-up circuitry switch based on the sensed line voltage.

10. The method according to claim 9, wherein if the sensed line voltage input is at or above the line voltage threshold level, and the battery back-up circuitry is connected to the output of the battery back-up unit, then the controlling the battery back-up circuitry switch includes disconnecting the battery back-up circuitry from the output of the battery back-up unit.

11. An apparatus comprising:

a battery back-up unit having an output for providing a direct current (DC) output voltage; and

a plurality of power supplies each power supply connected to receive the DC output voltage from the battery back-up unit, each power supply having;

power factor correction circuitry (PFC) which produces a corrected output voltage; and

sensing circuitry which senses the corrected output voltage and provides a detect signal when the corrected output voltage falls below a threshold reference voltage;

wherein the battery back-up unit includes;

a battery string having at least one battery and a series connected switch; and

control circuitry for controlling the series connected switch based on the detect signals from the respective sensing circuitry in the plurality of power supplies, to connect the battery string to the output of the battery back-up unit when the corrected output voltage in a respective power supply falls below a threshold reference voltage.

12. An apparatus comprising:

a battery back-up unit having an output for providing a direct current (DC) output voltage; and

a plurality of power supplies each power supply connected to receive the DC output voltage from the battery back-up unit, each power supply having;

power factor correction circuitry (PFC) which produces a corrected output voltage; and

sensing circuitry which senses the corrected output voltage and provides a detect signal when the corrected output voltage falls below a threshold reference voltage;

wherein the battery back-up unit includes;

a battery string having at least one battery and a series connected switch; and

control circuitry for controlling the series connected switch based on the detect signals from the respective sensing circuitry in the plurality of power supplies, to connect the battery string to the output of the battery back-up unit when the corrected output voltage in a respective power supply falls below a threshold reference voltage; and

wherein the sensing circuitry comprises in each respective power supply;

a comparator having first and second inputs, a first input being provided with the threshold reference voltage, and having an output which provides the detect signal; and

a voltage divider connected to divide the corrected output voltage and provide the divided corrected output voltage to the second input of the comparator.

13. The apparatus according to claim 12, wherein the control circuitry comprises:

isolation circuitry which electrically isolates the detect signals from the respective power supplies; and

processing circuitry which receives the isolated detect signals from the isolation circuitry and produces a control signal which controls the series connected switch.

14. The apparatus according to claim 13, wherein the processing circuitry comprises:

a microcontroller; and

logic circuitry.

15. The apparatus according to claim 14, wherein the logic circuitry comprises:

a plurality of first two-input AND gates, each of which receives a respective first enable signal from the microcontroller at a first input and a respective isolated detect signal at a second input and which provide a respective output, there being a respective first AND gate for each respective power supply of the plurality of power supplies;

an OR functional block having a plurality of inputs which receive the outputs of the respective first AND gates, and provides an output;

a second two-input AND gate which receives a second enable signal from the microcontroller at a first input, receives the output of the OR functional block at a second input, and provides an output; and

a latch circuit having a set input which receives the output of the second two-input AND gate, a reset input which receives a reset signal from the microcontroller, and an output which is provided to the microcontroller and to the series connected switch.

16. The apparatus according to claim 15, wherein the microcontroller has an interface to an external control system through which power supply information and control signals are exchanged.

17. The apparatus according to claim 16, wherein the battery back-up unit further comprises:

alternating current (AC) rectifying circuitry which receives an AC line input and provides pulsed DC output at the output of the battery back-up unit; and

an input sensor which senses the AC line input and provides an AC detect signal to the microcontroller.

18. The apparatus according to claim 17, wherein the microcontroller controls the latchto disconnect the battery string from the output of the battery back-up unit when the AC detect signal indicates an adequate AC line input to the battery back-up unit.

19. The apparatus according to claim 18, wherein the microcontroller reports a fault condition to the external control system when the battery string is vonnected to the output of the battery back-up unit and a detect signal from a respective power supply still indicates that the corrected output voltage in the respective power supply is below a threshold reference voltage.

20. A method of controlling a power system having input lines and battery back-up circuitry for backing up a plurality of power supply loads when a power loss due to a loss of power on the input lines from an external power source, or a loss of power due to a failure of a component of the power system occurs, comprising:

detecting the plurality of power supply loads and power supply load operating conditions at powering-on of the power system;

enabling power loss detection for selected operational power supply loads of the plurality of power supply loads;

enabling battery back-up operation;

monitoring the power system for a power loss in the selected operational power supply loads of the plurality of power supply loads;

if a power loss is detected in the selected operational power supply loads of the plurality of power supply loads, connecting the battery back-up circuitry to the plurality of power supply loads, and continuing to monitor the power system for a power loss in the selected operational power supply loads of the plurality of power supply loads; and

if a power loss is detected in any one of the selected operational power supply loads of the plurality of power supply loads after connecting the battery back-up circuitry to the plurality of power supply loads, then monitoring the power system input lines for the presence of power and if power is present at the power system input lines, then;

disabling only the power supply load in which the power loss is detected, disconnecting only the power supply load in which the power loss is detected, producing a fault signal, and disconnecting the battery back-up circuitry.

21. The method according to claim 20, wherein the power system battery back-up circuitry includes a logic circuit which receives power loss detection signals from the plurality of power supply loads;

and wherein the disabling only the power supply load in which the power loss is detected comprises;

masking in the logic circuit the power loss detection signal from the power supply load in which the power loss is detected.