Resettable safety circuit for PTC electric blankets and the like
US5770836A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Nov 8, 1996 |
| Grant date | Jun 23, 1998 |
| Priority date | — |
| Expiry date | Nov 8, 2016 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH05B2203/035
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A safety-assuring control device for an electric blanket which includes a PTC heater includes an integrated circuit microcontroller unit having first and second safety circuit inputs and an output connected to a control input of an electrically controlled heater switch. A neon tube is connected between the primary safety link return conductor of the heater and the first safety circuit input, to indicate whether there is a first type of fault in the PTC heater. A connection between the second safety circuit input and the secondary safety link return conductor of the PTC heater is provided which indicates whether there is a second type of fault in the heater. The microcontroller unit includes a preliminary fault detection circuit for supplying a limited power test signal in a test mode to the heater for a predetermined period of time prior to a full power operation of the heater. The microcontroller unit also includes a circuit for controlling operation of the microcontroller unit to terminate supply of current to the heater if at least one fault is detected by the microcontroller at least one of the first and second safety circuit inputs during the predetermined period of time, and …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.