Fault protection system for a respiratory conduit heater element

• US 6,598,604 B1
• Filed: 12/15/1999
• Issued: 07/29/2003
• Est. Priority Date: 12/23/1998
• Status: Expired due to Term

• Current Assignee: Fisher & Paykel Healthcare Limited
• Original Assignee: Fisher & Paykel Limited (Haier Group Company)
• Inventors: Seakins, Paul John
• Primary Examiner(s): Lo, Weilun
• Assistant Examiner(s): MITCHELL, TEENA KAY
• Application Number:
  US09/464,495
• Time in Patent Office: 1,322 Days
• Field of Search: 128/201.13, 128/202-2-2, 128/200.13, 128/204.17, 128/204.18, 128/204.21, 128/203.12, 128/203.17, 128/203.26, 128/203.27, 219/481, 219/501, 219/509, 219/517, 219/492, 219/212, 219/262, 219/268, 219/269, 392/488, 392/489, 361/93.1, 361/93.4, 361/94, 361/100, 372/311
• US Class Current: 128/203.17
• CPC Class Codes: A61M 16/1075 by influencing the temperature A61M16/1045 takes precedence
• CPC Class Codes: A61M 16/1095 in the connecting tubes
• CPC Class Codes: H02H 1/0015 Using arc detectors
• CPC Class Codes: H02H 3/07 and with permanent disconnection after a predetermined number of reconnection cycles
• CPC Class Codes: H02H 3/44 responsive to the rate of change of electrical quantities
• CPC Class Codes: H02H 5/10 responsive to mechanical injury, e.g. rupture of line, breakage of earth connection
• CPC Class Codes: H03K 2217/0027 Measuring means of, e.g. currents through or voltages across the switch

Abstract

A fault protection circuit for a respiratory conduit heater element in a respirator humidification system is disclosed. The circuit includes a spark detector as well as overcurrent detector. Several variations are included for the spark detector including a two winding transformer, a center tapped two winding transformer), and a high pass filtered inductor. A semiconductor switching configuration is also disclosed. Once the protection circuit detects a change in current over a certain level, or the average level raises above a threshold, then the current in the heater element is interrupted for a preset period.

Claims

1. A fault protection system adapted for use with a heater element comprising:

detecting means which include means to detect a rapid change in current in said heater element,

current interruptor means adapted to be in series with said heater element, and

timing means configured to activate said current interruptor means to interrupt the current in the heater element when said rapid change in current exceeds a first predetermined threshold.

2. A fault protection system adapted for use with a heater element, as claimed in claim 1 wherein said current interruptor means comprises:

two same channel MOSFETS each including a source, a gate and a drain, and with the source and gate of each said MOSFET respectively connected together, and adapted to receive a common switching voltage between each gate and source.

3. A fault protection system adapted for use with a heater element, as claimed in any one of claims 1 to 2 wherein said timing means is configured to activate said current interruptor means to interrupt the current in the heater element for a predetermined period.

5. A fault protection system adapted for use with a heater element as claimed in claim 2, wherein said detecting means comprises:

a transformer including a primary and secondary winding, said primary winding adapted to be connected in series with the heater element and a power source,

a full wave rectifier including rectifier input means and rectifier output means, said rectifier input means connected across said secondary winding of said transformer,

a low pass filter including low pass filter input means and low pass filter output means, said low pass filter output means providing a low pass filter output, said low pass filter input means connected to said rectifier output means, and

a comparator including comparator input means and comparator output means, said comparator input means connected to said low pass filter output means, wherein said low pass filter output reaches said first predetermined threshold, said current interruptor means is activated to interrupt the current in said heater element.

7. A fault protection system adapted for use with a heater element as claimed in claim 2, wherein said detecting means comprises:

an inductor having first and second ends where said first end of said inductor being adapted to be connected with one end of said heater element and said second end of said inductor adapted to be connected to a power source,

a first high pass filter including first filter input means and first filter output means, said first filter input means connected to said first end of said inductor,

a second high pass filter including second filter input means and second filter output means, said second filter input means connected to said second end of said inductor,

a full wave rectifier including rectifier input means and rectifier output means, said rectifier input means connected to said first filter output means and said second filter output means respectively,

a low pass filter including low pass filter input means and low pass filter output means, said low pass filter output means providing a low pass filter output, said low pass filter input means connected to said rectifier output means, and

a comparator including comparator input means and comparator output means, said comparator input means connected to said low pass filter output means, wherein said low pass filter output reaches said first predetermined threshold, said current interruptor means is activated to interrupt the current in said heater element.

4. A fault protection system adapted for use with a heater element comprising:

detecting means which includes a peak current detector for detecting peak current in said heater element and means to detect a rapid change in current in said heater element,

current interruptor means adapted to be in series with said heater element, and

timing means configured to activate said current interruptor means to interrupt the current in said heater element when said rapid change in current exceeds a first predetermined threshold and configured to activate said current interruptor means to interrupt the current in said heater element when said peak current exceeds a second predetermined threshold.

6. A fault protection system adapted for use with a heater element as claimed in claim 4, wherein said detecting means comprises:

a transformer including a primary winding with at least two end and a center tap and secondary winding, each end of said primary winding adapted to be connected with a first circuit of said heater element and a second circuit of said heater element respectively and said center tap of said primary winding adapted to be connected to a power source,

a full wave rectifier including rectifier input means and rectifier output means, said rectifier input means connected across said secondary winding of said transformer,

a low pass filter including low pass filter input means and low pass filter output means, said low pass filter output means providing a low pass filter output, said low pass filter input means connected to said rectifier output means, and

a comparator including comparator input means and comparator output means, said comparator input means connected to said filter output means, wherein said low pass filter output reaches said first predetermined threshold, said current interruptor means is activated to interrupt the current in said heater element.

8. A fault protection system adapted for use with a heater element comprising:

detecting means which includes a peak current detector for detecting peak current in said heater element,

current interruptor means adapted to be in series with said heater element, and

timing means configured to activate said current interruptor means to interrupt said current in the heater element when said peak current exceeds a predetermined threshold.

9. In a respiratory humidification system wherein a conduit supplies humidified gases to a patient from a humidifier, said conduit or said gases being heated by a respiratory conduit heater element, the improvement comprising that said system includes a fault protection system for said heater element comprising:

detecting means which include means to detect a rapid change of current in said heater element,

current interruptor means in series with said heater element, and

timing means configured to activate said current interruptor means to interrupt the current in said heater element when said rapid change in current exceeds a first predetermined threshold.

10. In a respiratory humidification system as claimed in claim 9 the improvements further comprising that said current interruptor means comprises:

two same channel MOSFETS each including a source, a gate and a drain with the source and gate of each said MOSFET respectively connected together, and adapted to receive a common switching voltage between each gate and source.

11. In a respiratory humidification system as claimed in any one of claims 9 to 10, the improvements further comprising said timing means is configured to activate said current interruptor means to interrupt the current in said heater element for a predetermined period.

12. In a respiratory humidification system wherein a conduit humidified gases to a patient from a humidifier, said conduit or said gases being heated by a respiratory conduit heater element, the improvements comprising that said system includes a fault protection system for said heater element comprising:

detecting means which includes a peak current detector for detecting a peak current in said heater element and means to detect a rapid change in current in said heater element,

current interruptor means adapted to be in series with said heater element, and

timing means configured to activate said current interruptor means to interrupt the current in said heater element when said rapid change in current exceeds a first predetermined threshold and configured to activate said current interruptor means to interrupt the current in said heater element when said peak current exceeds a second predetermined threshold.

13. In a respiratory humidification system as claimed in claim 12, the improvements further comprising that said detecting means comprises:

a transformer including a primary and secondary winding, said primary winding adapted to be connected in series with said heater element and a power source,

a full wave rectifier including rectifier input means and rectifier output means, said rectifier input means connected across said secondary winding of said transformer,

a low pass filter including low pass filter input means and low pass filter output means, said low pass filter output means providing a low pass filter output, said low pass filter input means connected to said rectifier output means, and

a comparator including comparator input means and comparator output means, said comparator input means connected to said low pass filter output means, wherein said low pass filter output reaches said first predetermined threshold, said current interruptor means is activated to interrupt the current in said heater element.

14. In a respiratory humidification system as claimed in claim 12, the improvements further comprising that said heater element including a first circuit and a second circuit and said detecting means comprises:

a transformer including a primary winding with at least two ends and a center tap and secondary winding, said primary winding having ends, each end of said primary winding adapted to be connected with a first circuit of said heater element and a second circuit of said heater element respectively and said center tap of said primary winding adapted to be connected to a power source,

a full wave rectifier including rectifier input means and rectifier output means, said rectifier input means connected across said secondary winding of said transformer,

a low pass filter including low pass filter input means and low pass filter output means, said low pass filter output means providing a low pass filter output, said low pass filter input means connected to said rectifier output means, and

a comparator including comparator input means and comparator output means, said comparator input means connected to said low pass filter output means, wherein the low pass filter output reaches said first predetermined threshold, said current interruptor means is activated to interrupt the current in said heater element.

15. In a respiratory humidification system as claimed in claim 12, the improvements further comprising that said detecting means comprises:

an inductor having first and second ends where said first end of said inductor being adapted to be connected with one end of said heater element and said second end of said inductor adapted to be connected to a power source,

a first high pass filter including first filter input means and first filter output means, said first filter input means connected to said, first end of said inductor,

a second high pass filter including second filter input means and second filter output means, said second filter input means connected to said second end of said inductor,

a full wave rectifier including rectifier input means and rectifier output means, said rectifier input means connected to said first filter output means and said second filter output means respectively,

a low pass filter including low pass filter input means and low pass filter output means, said low pass filter output means providing a low pass filter output, said low pass filter input means connected to said rectifier output means, and

a comparator including comparator input means and comparator output means, said comparator input means connected to said low pass filter output means, wherein said low pass filter output reaches said first predetermined threshold, said current interruptor means is activated to interrupt the current in said heater element.

16. In a respiratory humidification system wherein a conduit delivers humidified gases to a patient from a humidifier, said conduit being heated by a respiratory conduit heater element, the improvement comprising that said system includes a fault protection system for said heater element comprising:

detecting means which includes a peak current detector for detecting peak current in said heater element,

current interruptor means in series with said heater element, and

timing means configured to activate said current interruptor means to interrupt the current in said heater element when said peak current exceeds a predetermined threshold.