Claims
- 1. A loop powered process instrument comprising:
a control circuit measuring a process variable and developing a control signal representing the process variable; an output circuit for connection to a two-wire process loop for controlling current on the loop in accordance with the control signal; and a power supply circuit connected to the output circuit and the control circuit for receiving power from the two-wire process loop and supplying power to the control circuit, comprising cascaded charge pump circuits.
- 2. The loop powered process instrument of claim 1 wherein the charge pump circuits comprise divide-by-two charge pump circuits.
- 3. The loop powered process instrument of claim 1 wherein the charge pump circuits each have an efficiency of about 95%.
- 4. The loop powered process instrument of claim 1 wherein the power supply circuit comprises a current source connecting the cascaded charge pump circuits to the output circuit.
- 5. The loop powered process instrument of claim 1 wherein the power supply circuit comprises a regulator diode connecting an output of the cascaded charge pump circuits to the control circuit.
- 6. The loop powered process instrument of claim 1 wherein the power supply circuit has an input of about 13 volts and 3.5 mA and an output of about 3 volts and about 13 mA.
- 7. The loop powered process instrument of claim 1 wherein the power supply circuit has an overall efficiency of about 90%.
- 8. A loop powered process instrument comprising:
a control circuit measuring a process variable and developing a control signal representing the process variable; an output circuit for connection to a two-wire process loop for controlling current on the loop in accordance with the control signal; and a power supply circuit connected to the output circuit and the control circuit for receiving power from the two-wire process loop and supplying power to the control circuit, comprising a current source providing a select current to a plurality of cascaded switched capacitor voltage dividers.
- 9. The loop powered process instrument of claim 8 wherein the switched capacitor voltage dividers comprise divide-by-two charge pump circuits.
- 10. The loop powered process instrument of claim 8 wherein the switched capacitor voltage dividers each have an overall efficiency of at least 90%.
- 11. The loop powered process instrument of claim 8 wherein the switched capacitor voltage dividers each have an efficiency of about 95%.
- 12. The loop powered process instrument of claim 8 wherein the power supply circuit comprises a regulator diode connecting an output of the cascaded switched capacitor voltage dividers to the control circuit.
- 13. The loop powered process instrument of claim 8 wherein the power supply circuit has an input of about 13 volts and 3.5 mA and an output of about 3 volts and about 13 mA.
- 14. The loop powered process instrument of claim 8 wherein the power supply circuit has an overall efficiency of about 90%.
- 15. The loop powered process instrument of claim 8 wherein the switched capacitor voltage dividers comprise CMOS switched capacitor voltage converters each having a pump capacitance and an output capacitance.
- 16. In a loop powered process instrument including a control circuit measuring a process variable and developing a control signal representing the process variable and an output circuit for connection to a two-wire process loop for controlling current on the loop in accordance with the control signal, the improvement comprising:
a power supply circuit connected to the output circuit and the control circuit for receiving power from the two-wire process loop and supplying power to the control circuit, comprising a plurality of cascaded switched capacitor voltage dividers.
- 17. The loop powered process instrument of claim 16 wherein the improvement comprises two cascaded divide-by-two charge pump circuits each having an efficiency of about 95%.
- 18. The loop powered process instrument of claim 16 wherein the switched capacitor voltage dividers comprise CMOS switched capacitor voltage converters each having a pump capacitance and an output capacitance.
- 19. The loop powered process instrument of claim 16 wherein the power supply circuit has an input of about 13 volts and 3.5 mA and an output of about 3 volts and about 13 mA.
- 20. The loop powered process instrument of claim 16 wherein the power supply circuit comprises a current source connecting the cascaded switched capacitor voltage dividers to the output circuit and a regulator diode connecting an output of the cascaded switched capacitor voltage dividers to the control circuit.
CROSS-REFERENCE
[0001] This application claims priority of application No. 60/414,847 filed Sep. 30, 2002.
Provisional Applications (1)
|
Number |
Date |
Country |
|
60414847 |
Sep 2002 |
US |