System and method for switch status detection

Patent metadata

Field	Value
Publication number	US-9835687-B2
Application number	US-201414573407-A
Country	US
Kind code	B2
Filing date	Dec 17, 2014
Priority date	Dec 17, 2014
Publication date	Dec 5, 2017
Grant date	Dec 5, 2017

Abstract

Systems, methods, and circuits for determining one or more switch statuses are disclosed herein. In one example embodiment, such a system includes a first port configured to be coupled to a switch, a capacitor, a comparator having first and second input ports and an output port, a current source coupled to the first input port, and a control component. The first input port is coupled to the first port and a threshold voltage if applied to the second input port. The control component is configured so that, in at least one circumstance, it causes the current source to cease driving the current in response to receiving an indication from the output port indicating that an additional voltage applied to the first input port has changed from being less than the threshold voltage to being greater than that voltage, the indication being indicative of the switch status.

First claim

What is claimed is:

1. A system for determining a status of a switch having first and second terminals, the system comprising:
a first port configured to be coupled to the first terminal of the switch;
a capacitor coupled between the first port and ground;
a comparator device having first and second input ports and an output port, wherein the first input port is coupled at least indirectly to the first port and wherein a threshold voltage is applied to the second input port;
a current source coupled to the first input port; and
a control component coupled to the output port and the current source,
wherein the control component is configured to control the current source so that the current source intermittently drives current,
wherein the control component is configured so that, in at least a first operational circumstance in which the switch is open, the control component causes the current source to cease driving the current in response to receiving a first indication from the output port indicating that an additional voltage applied to the first input port has changed from being less than the threshold voltage to being greater than the threshold voltage, the first indication being indicative of the status of the switch,
wherein the control component is further configured so that, in at least a second operational circumstance in which the switch is closed, the control component causes the current source to continue driving the current for a full extent of a predetermined time period in response to receiving a second indication from the output port indicating throughout the predetermined time period that the additional voltage applied to the first input port remains less than the threshold voltage, and
wherein the control component is further configured so that, in at least a third operational circumstance in which the switch is open, the control component does not cause the current source to drive any of the current in response to receiving a third indication from the output port indicating that the additional voltage applied to the first input port is greater than the threshold voltage.

2. The system of claim 1 , further comprising a resistor that couples the first input port with the first port.

3. The system of claim 2 , further comprising a diode linking the current source to a power source, and wherein the comparator device includes an operational amplifier.

4. The system of claim 1 , wherein the control component includes one or more of a logic circuit and a microprocessor.

5. The system of claim 4 , wherein the threshold voltage is applied at least indirectly by way of a voltage source, and wherein the system includes the switch and the switch is a single pole, single throw (SPST) switch.

6. The system of claim 5 , further including a ground terminal to which the second terminal is directly coupled such that the switch is coupled directly between the first port and ground, and at least one leakage resistance associated with the capacitor.

7. The system of claim 4 , wherein the current source includes one or more of a resistor and a current mirror.

8. The system of claim 1 wherein, in at least one or more circumstances, a holding current less than the current is driven by the current source to avoid leak down of the capacitor.

9. The system of claim 8 , wherein the control component is configured to cause the current source to generate the current in one or more manners that are operational-circumstance dependent or time-varying.

10. The system of claim 9 , wherein the threshold voltage that is applied can vary depending upon one or more operational or selection criteria.

11. A circuit configured for interacting with a capacitor and a switch in a manner allowing for determining a status of the switch, the capacitor and switch being coupled together by way of a first node, the circuit comprising:
a comparator device having first and second input ports and an output port, wherein the first input port is configured to be coupled at least indirectly to the first node, and wherein the second input port is configured to receive a threshold voltage;
a current source coupled to the first input port; and
a control component coupled to the output port and the current source,
wherein the control component is configured to control the current source so that the current source intermittently drives current toward the first node,
wherein the control component is configured so that, in at least a first operational circumstance in which the switch is open, the control component causes the current source to cease driving the current toward the first node in response to receiving a first indication from the output port indicating that an additional voltage applied to the first input port has changed from being less than the threshold voltage to being greater than the threshold voltage, the first indication being indicative of the status of the switch, and
wherein the control component is further configured so that the control component (i), in at least a second operational circumstance in which the switch is open, refrains from causing the current source to drive any of the current in response to receiving a second indication from the output port indicating that the additional voltage applied to the first input port is greater than the threshold voltage, and (ii), in at least a third operational circumstance in which the switch is closed, causes the current source to continue driving the current for a full extent of a predetermined time period in response to receiving a third indication from the output port indicating throughout the predetermined time period that the additional voltage applied to the first input port is less than the threshold voltage.

12. The circuit of claim 11 , further comprising a diode linking the current source to a power source, and wherein the comparator device includes an operational amplifier.

13. The circuit of claim 11 , wherein the control component includes one or more of a logic circuit and a microprocessor.

14. The circuit of claim 11 , wherein the current source includes one or more of a resistor and a current mirror.

15. The system of claim 11 , wherein the first input port is coupled to the first node by way of a resistor.

Assignees

• Edwards William E
• Andresen Anthony F
• Nxp Usa Inc

Inventors

• Edwards William E
• Andresen Anthony F

Classifications

• H01H71/04

  Means for indicating condition of the switching device {(by means of an auxiliary contact H01H71/46)} · CPC title

• G01R31/3277 Primary

  of low voltage devices, e.g. domestic or industrial devices, such as motor protections, relays, rotation switches · CPC title