Open load diagnostics for loads that are PWM controlled

Patent metadata

Field	Value
Publication number	US-11489479-B2
Application number	US-201716634399-A
Country	US
Kind code	B2
Filing date	Aug 3, 2017
Priority date	Aug 3, 2017
Publication date	Nov 1, 2022
Grant date	Nov 1, 2022

Abstract

Methods and apparatuses for detecting an open load condition for a load. The load is coupled to a power source at a high side and to a ground at a low side through at least one switch, the load has a first end and a second end, a first voltage at the first end is kept constant. A switch is controlled by a PWM signal. After the switch is turned off by the PWM signal, the voltage associated with the second end of the load is measured. In one embodiment, a change of the second voltage during a predefined delay is compared with a predefined voltage threshold. In another embodiment, the time it takes for the change of the second voltage to reach a predefined voltage threshold is compared with a predefined time threshold.

First claim

What is claimed is:

1. An apparatus for detecting an open load condition for a load, wherein the load is coupled to a power source and to a ground through at least one switch, the load has a first end and a second end, a first voltage at the first end is kept constant, the apparatus is structured to:
output a pulse width modulation (PWM) signal to selectively turn on or off a first switch of the at least one switch;
use the PWM signal to turn off the first switch at a first time point;
determine a second voltage associated with the second end of the load after a predefined delay from the first time point;
determine whether a change of the second voltage during the predefined delay is less than a predefined threshold voltage; and
in response to determining that the change is less than the predefined threshold voltage, determine that the open load condition exists for the load,
wherein the load is coupled to the ground at the first end through the first switch and at the second end through a second switch, the load is coupled to the power source at the first end through a third switch and at the second end through a fourth switch, and the apparatus is structured to:
output a Freewheeling signal to selectively turn on or off the third switch at a second time point;
wherein the predefined delay from the first time point is between the first time point and the second time point.

2. The apparatus of claim 1 , wherein the load is an inductor type load, and wherein the second voltage changes towards the first voltage since the first switch is turned off at the first time point.

3. An apparatus for detecting an open load condition for a load, wherein the load is coupled to a power source and to a ground through at least one switch, the load has a first end and a second end, a first voltage at the first end is kept constant, the apparatus is structured to:
output a pulse width modulation (PWM) signal to selectively turn on or off a first switch of the at least one switch;
use the PWM signal to turn off the first switch at a first time point;
determine whether a change of a second voltage associated with the second end of the load since the first time point has reached a predefined threshold voltage;
in response to determining that the change has reached the predefined threshold voltage, determine a time period for the change to reach the predefined threshold voltage since the first time point;
determine whether the time period is greater than a predefined threshold time period; and
in response to determining that the time period is greater than the predefined threshold time period, determine that the open load condition exists for the load.

4. The apparatus of claim 3 , wherein the load is an inductor type load, and wherein the second voltage changes towards the first voltage since the first switch is turned off at the first time point.

5. The apparatus of claim 3 , wherein the load is coupled to the ground at the first end through the first switch and at the second end through a second switch, the load is coupled to the power source at the first end through a third switch and at the second end through a fourth switch, and the apparatus is structured to:
output a Freewheeling signal to selectively turn on or off the third switch at a second time point after the first time point.

6. The apparatus of claim 3 , wherein the load is coupled directly to the ground at the first end and coupled to the power source at the second end through the first switch, and a second switch is coupled between the second end and the ground.

7. The apparatus of claim 3 , wherein the load is coupled directly to the ground at the first end and coupled to the power source at the second end through the first switch.

8. The apparatus of claim 3 , wherein the load is coupled directly to the power source at the first end and coupled to the ground at the second end through the first switch.

9. The apparatus of claim 3 , wherein the load is coupled to the power source at the first end through the first switch and to the ground at the second end through a second switch.

10. A method for detecting an open load condition for a load, wherein the load is coupled to a power source and to a ground through at least one switch, the load has a first end and a second end, a first voltage at the first end is kept constant, the method comprising:
outputting a pulse width modulation (PWM) signal to selectively turn on or off a first switch of the at least one switch;
using the PWM signal to turn off the first switch at a first time point;
determining a second voltage associated with the second end of the load after a predefined delay from the first time point;
determining whether a change of the second voltage during the predefined delay is less than a predefined threshold voltage; and
in response to determining that the change is less than the predefined threshold voltage, determining that the open load condition exists for the load,
wherein the load is coupled to the ground at the first end through the first switch and at the second end through a second switch, the load is coupled to the power source at the first end through a third switch and at the second end through a fourth switch, and the method further comprises:
outputting a Freewheeling signal to selectively turn on or off the third switch at a second time point;
wherein the predefined delay from the first time point is between the first time point and the second time point.

11. The method of claim 10 , wherein the load is an inductor type load, and wherein the second voltage changes towards the first voltage since the first switch is turned off at the first time point.

12. A method for detecting an open load condition for a load, wherein the load is coupled to a power source and to a ground through at least one switch, the load has a first end and a second end, a first voltage at the first end is kept constant, the method comprising:
outputting a pulse width modulation (PWM) signal to selectively turn on or off a first switch of the at least one switch;
using the PWM signal to turn off the first switch at a first time point;
determining whether a change of a second voltage associated with the second end of the load since the first time point has reached a predefined threshold voltage;
in response to determining that the change has reached the predefined threshold voltage, determining a time period for the change to reach the predefined threshold voltage since the first time point;
determining whether the time period is greater than a predefined threshold time period; and
in response to determining that the time period is greater than the predefined threshold time period, determining that the open load condition exists for the load.

13. The method of claim 12 , wherein the load is an inductor type load, and wherein the second voltage changes towards the first voltage since the first switch is turned off at the first time point.

14. The method of claim 12 , wherein the load is coupled to the ground at the first end through the first switch and at the second end through a second switch, the load is coupled to the power source at the first end through a third switch and at the second end through a fourth switch, and the method further comprising:
output a Freewheeling signal to selectively turn on or off the third switch at a second time point after the first time point.

Assignees

• Cummins Inc

Inventors

• Bhat Subramanya
• Koli Santosh Shankar
• Belde Shashi Kanth
• Musa Abu

Classifications

• H02H7/0838

  with H-bridge circuit · CPC title

• H02P29/024 Primary

  Detecting a fault condition, e.g. short circuit, locked rotor, open circuit or loss of load · CPC title

• H02H3/12

  responsive to underload or no-load {(for motors H02H7/0827)} · CPC title