Load voltage control for a field device

• US 6,781,256 B2
• Filed: 10/26/2001
• Issued: 08/24/2004
• Est. Priority Date: 10/27/2000
• Status: Active Grant

• Current Assignee: Schneider Electric Systems USA, Inc. (Schneider Electric SE)
• Original Assignee: Invensys Systems Incorporated (Invensys PLC)
• Inventors: Loechner, Michael
• Primary Examiner(s): TOATLEY, GREGORY J
• Application Number:
  US09/983,888
• Publication Number:
  US 20020101748A1
• Time in Patent Office: 1,033 Days
• Field of Search: 307/45, 307/46, 307/48, 307/126, 322/28, 363/21.06
• US Class Current: 307/46
• CPC Class Codes: H02J 7/345 using capacitors as storage or buffering devices
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load

Abstract

To enable a relatively constant output voltage at a DC/DC converter of a field device during a predictable time after shut-down of energy supplied to the DC/DC converter there is proposed a load voltage controller having a comparison unit adapted to compare the load voltage signal (Uo) with an externally supplied load voltage reference signal (Uref). When the load voltage (Uo) exceeds the load voltage reference signal (Uref) an energy buffer stores supplied energy for subsequent resupply to the load of the field device.

Claims

1. A load voltage controller for a field device, comprising:

a DC/DC converter adapted to receive a power supply voltage signal (Ui) on a power supply line of the field device for conversion into a load voltage signal (Uo) and subsequent supply to a load of the field device;

a comparison unit adapted to compare the load voltage signal (Uo) with an externally supplied load voltage reference signal (Uref); and

an energy buffer adapted to store supplied energy when an output signal of the comparison unit indicates that the load voltage signal (Uo) exceeds the load voltage reference signal (Uref).

2. The voltage controller of claim 1 wherein the energy buffer is further adapted to supply energy to the load of the field device when the output signal of the comparison unit indicates that the load voltage signal (Uo) is lower than the load voltage reference signal (Uref).

3. The load voltage controller of claim 1 further comprising a switching unit connected between the output of the DC/DC converter and the energy buffer, the switching unit processing the output signal of the comparison unit to:

establish a connection between the DC/DC converter and the energy buffer when the load voltage reference signal (Uref) exceeds the load voltage signal (Uo) for supply of energy from the energy buffer to the load of the field device;

disconnect the DC/DC converter and the energy buffer when the load voltage reference signal (Uref) equals the load voltage signal (Uo); and

establish a current path between the energy buffer and the power supply line of the field device when the load voltage reference signal (Uref) is lower than the load voltage signal (Uo) for supply of energy from the energy supply line to the energy buffer.

4. The load voltage controller of claim 2 further comprising a switching unit connected between the output of the DC/DC converter and the energy buffer, the switching unit processing the output signal of the comparison unit to:

establish a connection between the DC/DC converter and the energy buffer when the load voltage reference signal (Uref) exceeds the load voltage signal (Uo) for supply of energy from the energy buffer to the load of the field device;

disconnect the DC/DC converter and the energy buffer when the load voltage reference signal (Uref) equals the load voltage signal (Uo); and

establish a current path between the energy buffer and the power supply line of the field device when the load voltage reference signal (Uref) is lower than the load voltage signal (Uo) for supply of energy from the energy supply line to the energy buffer.

5. The load voltage controller of claim 1 further comprising a bypass unit coupled across the energy buffer for overvoltage protection and to sink overcurrent.

6. The load voltage controller of claim 2 further comprising a bypass unit coupled across the energy buffer for overvoltage protection and to sink overcurrent.

7. The load voltage controller of claim 3 further comprising a bypass unit coupled across the energt buffer for overvoltage protection and to sink overcurrent.

8. The load voltage controller of claim 3 wherein the comparison unit and the switching unit are realized in an integrated manner as a first operational amplifier having the power supply voltage signal (Ui) on the power supply line as positive supply and the load voltage signal (Uo) as negative supply and receiving the load voltage reference signal (Uref) and load voltage signal (Uo) as input signals, respectively.

9. The load voltage controller of claim 5 wherein the comparison unit and the switching unit are realized in an integrated manner as a first operational amplifier having the power supply voltage signal (Ui) on the power supply line as positive supply and the load voltage signal (Uo) as negative supply and receiving the load voltage reference signal (Uref) and load voltage signal (Uo) as input signals, respectively.

10. The load voltage controller of claim 3 wherein:

the DC/DC converter is a charge pump with at least two stages, the charge pump being adapted to provide at least one intermediate voltage signal with respect to each stage having a voltage level lying between the power supply voltage signal (Ui) and the load voltage signal (Uo), respectively; and

the comparison unit and the switching unit are realized in an integrated manner as a second operational amplifier having the power supply voltage signal (Ui) on the power supply line as positive supply and the at least one intermediate voltage signal of the charge pump as negative supply and receiving the load voltage reference signal (Uref) and the at least one intermediate voltage signal as input signals, respectively.

11. The load voltage controller of claim 5 wherein:

the DC/DC converter is charge pump with at least two stages, the charge pump being adapted to provide at least one intermediate voltage signal with respect to each stage having a voltage level lying between the power supply voltage signal (Ui) and the load voltage signal (Uo), respectively; and

the comparison unit and the switching unit are realized in an integrated manner as a second operational amplifier having the power supply voltage signal (Ui) on the power supply line as positive supply and the at least one intermediate voltage signal of the charge pump as negative supply and receiving the load voltage reference signal (Uref) and the at least one intermediate voltage signal as input signals, respectively.

12. The load voltage controller claim 3 wherein:

the comparison unit and the switching unit are realized in an integrated manner as a third operational amplifier;

the DC/DC converter is a charge pump with at least two stages, the charge pump being adapted to provide intermediate voltage signals with respect to each stage having a voltage level lying between the power supply voltage signal (Ui) and the load voltage signal (Uo), respectively;

a first multiplexer operable to select either the power supply voltage signal (Ui) on the power supply line or one of the intermediate voltage signals as positive supply of the third operational amplifier;

a second multiplexer operable to select either one of the intermediate voltage signals or the load voltage signal (Uo) as negative supply of the third operational amplifier; and

the third operational amplifier receives the load voltage reference signal (Uref) and the output signal of the second multiplexer as input signals, respectively;

wherein

the load voltage reference signal (Uref) of the third operational amplifier is switched in relation to the positive supply voltage of the third operational amplifier.

13. The load voltage controller claim 5 wherein:

the comparison unit and the switching unit are realized in an integrated manner as a third operational amplifier;

the DC/DC converter is a charge pump with at least two stages, the charge pump being adapted to provide intermediate voltage signals with respect to each stage having a voltage level lying between the power supply voltage signal (Ui) and the load voltage signal (Uo), respectively;

a first multiplexer operable to select either the power supply voltage signal (Ui) on the power supply line or one of the intermediate voltage signals as positive supply of the third operational amplifier;

a second multiplexer operable to select either one of the intermediate voltage signals or the load voltage signal (Uo) as negative supply of the third operational amplifier; and

the third operational amplifier receives the load voltage reference signal (Uref) and the output signal of the second multiplexer as input signals, respectively;

wherein

the load voltage reference signal (Uref) of the third operational amplifier is switched in relation to the positive supply voltage of the third operational amplifier.

14. The load voltage controller of claim 8 wherein the energy buffer comprises a capacitor connected between an output terminal of the first, second or third operational amplifier and ground.

15. The load voltage controller of claim 10 wherein the energy buffer comprises a capacitor connected between an output terminal of the first, second or third operational amplifier and ground.

16. The load voltage controller of claim 12 wherein the energy buffer comprises a capacitor connected between an output terminal of the first, second or third operational amplifier and ground.

17. The load voltage controller of claim 8 wherein the bypass unit comprises a current sink element such as a Zener diode or a fourth operational amplifier having a reference voltage being lower than the input voltage to the DC/DC converter.

18. The load voltage controller of claim 10 wherein the bypass unit comprises a current sink element such as a Zener diode or a fourth operational amplifier having a reference voltage being lower than the input voltage to the DC/DC converter.

19. The load voltage controller of claim 12 wherein the bypass unit comprises a current sink element such as a Zener diode or a fourth operational amplifier having a reference voltage being lower than the input voltage to the DC/DC converter.

20. The load voltage controller of claim 14 wherein the bypass unit comprises a current sink element such as a Zener diode or a fourth operational amplifier having a reference voltage being lower than the input voltage to the DC/DC converter.

29. The load voltage controller of claim 1 wherein the energy buffer is further adapted to supply energy to the load of the field device when the output signal of the comparison unit indicates that the load voltage signal (Uo) is lower than the load voltage reference signal (Uref) after shut down of the power supply voltage signal (Ui) to the DC/DC converter.

21. A load voltage control method for a field device comprising:

receiving a power supply voltage signal (Ui) on a power supply line of the field device for conversion into a load voltage signal (Uo) and subsequent supply of the load voltage signal (Uo) to a load of the field device;

comparing the load voltage signal (Uo) with an externally supplied load voltage reference signal (Uref); and

storing energy being supplied through the power supply line in an energy buffer when the load voltage signal (Uo) exceeds the load voltage reference signal (Uref).

22. The load voltage control method of claim 21 wherein stored energy is supplied from the energy buffer to the load of the field device when the load voltage signal (Uo) is lower than the load voltage reference signal (Uref).

23. The load voltage control method of claim 21 wherein the energy buffer is disconnected from the load of the field device when the load voltage reference signal (Uref) equals the load voltage signal (Uo).

24. The load voltage control method of claim 22 wherein the energy buffer is disconnected from the load of the field device when the load voltage reference signal (Uref) equals the load voltage signal (Uo).

30. The load voltage control method of claim 21 further comprising supplying energy from the energy buffer to the load of the field device when the load voltage signal (Uo) is lower than the load voltage reference signal (Uref) after shut down of the power supply voltage signal (Ui).

25. A load voltage control method for a field device including computer software running on a load voltage processor, the method comprising:

loading the computer software into a memory associated with the load voltage processor;

receiving a power supply voltage signal (Ui) on a power supply line of the field device for conversion into a load voltage signal (Uo) and subsequent supply of the load voltage signal (Uo) to a load of the field device;

comparing the load voltage signal (Uo) with an externally supplied load voltage reference signal (Uref); and

storing energy being supplied through the power supply line in an energy buffer when the load voltage signal (Uo) exceeds the load voltage reference signal (Uref).

26. The load voltage control method of claim 25 wherein stored energy is supplied from the energy buffer to the load of the field device when the load voltage signal (Uo) is lower than the load voltage reference signal (Uref).

27. The load voltage control method of claim 25 wherein the energy buffer is disconnected from the load of the field device when the load voltage reference signal (Uref) equals the load voltage signal (Uo).

28. The load voltage control method of claim 26 wherein the energy buffer is disconnected from the load of the field device when the load voltage reference signal (Uref) equals the load voltage signal (Uo).

31. The load voltage control method of claim 25 further comprising supplying energy from the energy buffer to the load of the field device when the load voltage signal (Uo) is lower than the load voltage reference signal (Uref) after shut down of the power supply voltage signal (Ui).