OPTO-ISOLATION CIRCUIT

• US 20130240764A1
• Filed: 09/13/2010
• Published: 09/19/2013
• Est. Priority Date: 09/13/2010
• Status: Active Grant

• Current Assignee: Micro Motion Incorporated (Emerson Electric Company)
• Original Assignee: Micro Motion Incorporated (Emerson Electric Company)
• Inventors: Kravitz, Andrew S
• Granted Patent: US 9,068,888 B2
• Time in Patent Office: Days
• US Class Current: 250/551
• CPC Class Codes: G01J 1/44 Electric circuits for command of an exposure part G03B7/02
• CPC Class Codes: H01L 31/02019 for devices characterised by at least one potential jump barrier or surface barrier
• CPC Class Codes: H04B 10/802 for isolation, e.g. using optocouplers

Abstract

An opto-isolation circuit (300) is provided, including an optocoupler (303) configured to optically transfer a raw output signal, a conversion circuit (317) coupled to an optocoupler output and configured to convert the raw output signal into a predetermined converted signal, and a control circuit (306) coupled to the optocoupler output. The control circuit (306) is configured to generate an autonomous control signal from the raw output signal after the raw output signal passes through the optocoupler (303), wherein the autonomous control signal is generated only if the raw output signal exceeds a predetermined conversion threshold, and control the conversion circuit (317) and convert the raw output signal into the predetermined converted signal if the autonomous control signal is generated by the control circuit (306) and output the raw output signal to an output port if the autonomous control signal is not generated by the control circuit (306).

Claims

1. An opto-isolation circuit (300), comprising:

an optocoupler (303) configured to optically transfer a raw output signal;

a conversion circuit (317) coupled to an optocoupler output and configured to convert the raw output signal into a predetermined converted signal; and

a control circuit (306) coupled to the optocoupler output and configured to;

generate an autonomous control signal from the raw output signal after the raw output signal passes through the optocoupler (303), wherein the autonomous control signal is generated only if the raw output signal exceeds a predetermined conversion threshold; and

control the conversion circuit (317) and convert the raw output signal into the predetermined converted signal if the autonomous control signal is generated by the control circuit (306) and output the raw output signal to an output port if the autonomous control signal is not generated by the control circuit (306).

2. The opto-isolation circuit (300) of claim 1, with the predetermined conversion threshold comprising a predetermined energy threshold.

3. The opto-isolation circuit (300) of claim 1, with the predetermined conversion threshold comprising a predetermined frequency threshold.

4. The opto-isolation circuit (300) of claim 1, with the predetermined conversion threshold comprising a predetermined frequency threshold of about 2 kHz or greater.

5. The opto-isolation circuit (300) of claim 1, with the raw output signal comprising a square wave and with the frequency of the raw output signal conveying information.

6. The opto-isolation circuit (300) of claim 1, with the raw output signal comprising a square wave and with the frequency of the raw output signal conveying information, wherein the raw output signal is generated by a pickoff sensor.

7. The opto-isolation circuit (300) of claim 1, with the raw output signal comprising a frequency-modulated square wave signal and with the predetermined converted signal comprising a current-modulated signal.

8. The opto-isolation circuit (300) of claim 1, with the raw output signal comprising a sensor time period (STP) mode signal comprising a frequency-modulated square wave signal and with the predetermined converted signal comprising a milliamp output (MAO) mode signal comprising a current-modulated signal.

9. The opto-isolation circuit (300) of claim 1, further comprising a switch (311) coupled to the optocoupler output and switching between the output port and the conversion circuit (317), with the conversion circuit (317) being coupled to the switch (311) and the output port, wherein the switch (311) is controlled by the control circuit (306).

10. The opto-isolation circuit (300) of claim 1, with the control circuit (306) comprising:

a first amp U1 including a U1 input coupled to a first node N1 and a U1 output coupled to a second node N2, with the first amp U1 generating a predetermined positive output voltage when a U1 input voltage exceeds a predetermined U1 threshold;

a first capacitor C1 coupled to the first node N1 and passing the raw output signal to the first node N1;

a first resistor R1 coupled between the first node N1 and ground, with the first capacitor C1 and the first resistor R1 determining a pulse width of a square wave generated by the first amp U1;

a diode D1 connected between the second node N2 and a third node N3 and forward biased by the first amp U1;

a second resistor R2 coupled between the third node N3 and a fourth node N4;

a second amp U2 including a U2 input coupled to the fourth node N4 and a U2 output providing the autonomous control signal when a U2 input voltage exceeds a predetermined U2 threshold;

a second capacitor C2 connected between the fourth node N4 and the ground; and

a third resistor R3 coupled between the fourth node N4 and the ground;

wherein the first resistor R1, the first capacitor C1, the second resistor R2, the second capacitor C2, and the third resistor R3 are selected so that the second amp U2 triggers when the raw output signal exceeds the predetermined conversion threshold, creating the autonomous control signal.

11. A method of transferring a raw output signal through an optocoupler, the method comprising:

transferring the raw output signal through the optocoupler;

generating an autonomous control signal from the raw output signal after the raw output signal passes through the optocoupler, wherein the autonomous control signal is generated only if the raw output signal exceeds a predetermined conversion threshold; and

converting the raw output signal into a predetermined converted signal if the autonomous control signal is generated and outputting the raw output signal to an output port if the autonomous control signal is not generated.

12. The method of claim 11, with the predetermined conversion threshold comprising a predetermined energy threshold.

13. The method of claim 11, with the predetermined conversion threshold comprising a predetermined frequency threshold.

14. The method of claim 11, with the predetermined conversion threshold comprising a predetermined frequency threshold of about 2 kHz or greater.

15. The method of claim 11, with the raw output signal comprising a square wave and with the frequency of the raw output signal conveying information.

16. The method of claim 11, with the raw output signal comprising a square wave and with the frequency of the raw output signal conveying information, wherein the raw output signal is generated by a pickoff sensor.

17. The method of claim 11, with the raw output signal comprising a frequency-modulated square wave signal and with the predetermined converted signal comprising a current-modulated signal.

18. The method of claim 11, with the raw output signal comprising a sensor time period (STP) mode signal comprising a frequency-modulated square wave signal and with the predetermined converted signal comprising a milliamp output (MAO) mode signal comprising a current-modulated signal.

19. The method of claim 11, with the method further comprising switching between an output port and a conversion circuit, with the conversion circuit being coupled to a switch and the output port and with the conversion circuit generating the predetermined converted signal.