Characterization Of AC Mains Circuit Parameters

• US 20090179626A1
• Filed: 10/21/2008
• Published: 07/16/2009
• Est. Priority Date: 01/10/2008
• Status: Active Grant

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Inventors: Smith, David E., Wade, Kenneth B.
• Granted Patent: US 8,080,769 B2
• Time in Patent Office: Days
• US Class Current: 323/299
• CPC Class Codes: G03G 15/5004 Power supply control, e.g. power-saving mode, automatic power turn-off
• CPC Class Codes: H02M 1/0022 the disturbance parameters being input voltage fluctuations
• CPC Class Codes: H02M 5/293 using semiconductor devices only

Abstract

Methods, devices, and systems implementing AC mains circuit parameter characterization are provided. One example embodiment of an image forming device includes a variable electrical load, and a controller adapted to vary the electrical load based on a characterization of AC mains circuit parameters including source voltage and line impedance wherein line impedance is determined for a change in source voltage.

Claims

1. An image forming device, comprising

a variable electrical load;

a controller adapted to vary the electrical load based on a characterization of AC mains circuit parameters including source voltage and line impedance; and

wherein line impedance is determined for a change in source voltage.

2. The image forming device of claim 1, wherein the electrical load is controlled based on the characterization to prevent a maximum current draw from the AC mains circuit from causing predicted input voltage to fall below a preset limit.

3. The image forming device of claim 2, wherein the line impedance is determined from characterizing electrical signals measured at a minimal load configuration after determining the change in source voltage.

4. The image forming device of claim 3, wherein the maximum current draw is adjusted based on the line impedance determined after the change in source voltage.

5. The image forming device of claim 4, wherein source voltage is determined when voltage at the image forming device changes by a preset amount not caused by load changes internal to the image forming device.

6. A method of characterizing AC mains circuit parameters, comprising:

measuring root mean square (RMS) values of characterizing electrical signals to a pulse width modulated (PWM) load at a first load;

measuring RMS values of characterizing electrical signals to the PWM load at a second PWM load;

extrapolating the RMS values of characterizing electrical signals for the PWM load at the second PWM load, to values for a PWM load at third PWM load; and

determining AC mains circuit parameters using changes in RMS values of characterizing electrical signals between PWM loading at the first load and the third PWM load.

7. The method of claim 6, wherein:

RMS values of characterizing electrical signals to the PWM load at first PWM load are a weighted composite equal to X % of the RMS values to the PWM load at full load plus (100-X)% of the RMS values for the PWM load at first load;

extrapolating includes solving the weighted composite equality for the RMS values at full PWM load; and

wherein X is the percent modulation at the second PWM load.

8. The method of claim 7, wherein characterizing electrical signals include input current and voltage.

9. The method of claim 8, wherein AC mains circuit parameters determined includes source voltage and AC mains circuit impedance.

10. The method of claim 9, wherein the method includes:

monitoring the input voltage; and

repeating the measuring, extrapolating, and determining steps based on a change in the input voltage exceeds a threshold.

11. The method of claim 10, wherein the method includes adjusting the PWM load based on the AC mains circuit parameters.

12. The method of claim 11, wherein the method includes adjusting the PWM load based on drawing a maximum amount of power available from the AC mains circuit without reducing input voltage below a preset limit.

13. The method of claim 8, wherein X is as large as possible in the range between 0 and 100 without reducing input voltage below a preset limit during measuring.

14. The method of claim 7, wherein the measuring steps are arranged to occur during a period with no net load changes other than PWM load changes.

15. A device, comprising:

at least some pulse width modulation (PWM) electrical load;

a controller for characterizing AC mains circuit parameters and modulating the PWM electrical load based on the characterization; and

wherein the characterization includes;

measuring root mean square (RMS) electrical signal values to the device at 0% PWM loading and X % PWM loading, X being greater than 0;

determining RMS electrical signal values at 100% PWM loading from the measured RMS electrical signal values; and

solving for AC mains circuit parameters from the change in RMS electrical signal values from 0% to 100% PWM loading.

16. The device of claim 15, wherein RMS electrical signals values include input current and voltage.

17. The device of claim 16, wherein the PWM electrical load is modulated based on the characterization to prevent total power draw from the AC mains circuit from causing predicted input voltage to fall below a preset limit.

18. The device of claim 17, wherein the device includes a computing component, and the preset limit is above an input voltage which can provide a minimum operating voltage to the computing component.

19. The device of claim 16, wherein:

AC mains circuit parameters characterized includes source voltage and circuit impedance; and

characterization of AC mains circuit parameters occurs after power-up of the device, and after the input voltage changes by a set amount not caused by the device.

20. The device of claim 16, wherein:

AC mains circuit parameters characterized includes source voltage and circuit impedance;

an initial characterization of AC mains circuit parameters occurs after power-up of the device;

re-characterization of AC mains source voltage occurs on a periodic basis based on updated measurement of RMS electrical signal values to the device at X % PWM loading and a last measurement of RMS electrical signal values to the device at 0% PWM loading; and

re-characterization of AC mains circuit impedance, based on updated measurement of RMS electrical signal values to the device at 0% PWM loading, occurs after change in the re-characterized source voltage exceeds a certain magnitude.

21. The device of claim 20, wherein the PWM electrical load is a component of an image forming mechanism to form an image on media.

22. The device of claim 16, wherein measuring at X % PWM loading is arranged to exclude load changes of the device not attributable to the change in PWM loading from 0% PWM.

23. The device of claim 16, wherein measuring at X % PWM loading is arranged to occur when total device loading is equal to a total device loading at 0% PWM loading plus changes in the PWM electrical load.

24. The device of claim 23, wherein the PWM electrical load is selected from the group including:

a print media dryer;

a media marking mechanism; and

a vacuum hold-down system.

25. An image forming device, comprising

a variable electrical load;

a controller adapted to vary the electrical load based on at least two AC mains circuit characterizing electrical signals measurements; and

wherein the measurements are arranged to coincide with at least two different known load configurations, the different load configurations being held constant at least during the measurements.