Circuit arrangement for controlling the temperature of a heating element
US5847367A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 11, 1997 |
| Grant date | Dec 8, 1998 |
| Priority date | — |
| Expiry date | Jun 11, 2017 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG05D23/2401
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
The temperature of a heating element (3), which heating element has a temperature dependent resistance, is measured by comparing the current through it with a user adjustable reference value. The AC voltage across a current sensing resistor (7) in series with the heating element (3) is compared in a comparator (9) with a reference AC voltage generated at a tap (6) of a voltage divider (8). The phase of the logic output signal of the comparator (9) indicates a first state in which the heating element (3) is too hot or is not conducting, or a second state in which the heating element (3) is too cold and conducting. A second comparator (16) detects whether or not the heating element (3) is conducting. A logic gate (18) and a latch (17) switch on the current through the heating element (3) in response to timed pulses from a timing circuit (15) and switch off the current through the heating element (3) when the heating element (3) is conducting and too hot.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.