Safe Heating Circuit with PTC and NTC Temperature Control
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Solution Overview
Problem
Electric blankets pose safety risks due to inaccurate temperature control and aging elements leading to short circuits or open circuits, which can cause overheating and potential fires.
Innovation Solution
A safe heating circuit utilizing a Positive Temperature Coefficient (PTC) + Negative Temperature Coefficient (NTC) temperature control mode, incorporating a key element short-circuit or open-circuit detection protection circuit to precisely control heating temperature, detect faults, and switch off the power supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If temperature control of electric heating wire is inaccurate or key elements age leading to short circuit or open circuit, then local temperature becomes too high causing fire hazard, but adding detection and protection circuits increases device complexity
Solution Approach 1:
The heating circuit is segmented into multiple independent monitoring zones with separate detection circuits for temperature, short circuit, and open circuit conditions. Each segment can be independently monitored and controlled, allowing fault isolation without requiring complete system shutdown or complex centralized control.
Solution Approach 2:
The protection circuits perform preliminary detection of potential faults (short circuit, open circuit, overtemperature) before they can cause dangerous conditions. The system proactively identifies aging elements and incipient failures, enabling preventive action rather than reactive response to actual hazards.
2Measurement precision
If simple temperature control is used, then device complexity is low, but temperature control precision is insufficient leading to overheating risks
Solution Approach 1:
The system implements multi-point temperature feedback using thermocouples or RTD sensors distributed throughout the heating element. The control circuit continuously compares actual temperature readings against setpoint values and adjusts power delivery accordingly, maintaining precise temperature control while compensating for thermal gradients and external conditions.
Solution Approach 2:
The control system dynamically adjusts heating parameters (power level, cycling duty cycle, temperature setpoint) based on real-time sensor feedback and operational conditions. This allows adaptive temperature control that maintains precision across varying environmental conditions and heating stages without requiring overly complex circuitry.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables precise temperature control, timely detection of faults, and immediate power shutdown, thereby preventing overheating and fires, ensuring user safety and property protection.
Implementation Method 1
a PTC electric heating element, generating heat when being electrified
Implementation Method 2
a PTC electric heating element, generating heat when being electrified; Positive Temperature Coefficient (PTC) temperature control mode
Implementation Method 3
an NTC element, disposed between the PTC electric heating element and a sensing element; Negative Temperature Coefficient (NTC) temperature control mode
Data Source
AI summary
A safe heating circuit, comprising a PTC electric heating element; a first switching element, configured to switch on-off a power loop of the heating element; a first voltage acquisition circuit, configured to sample a first temperature voltage; an NTC element configured to receive a leakage current; a second voltage acquisition circuit, configured to sample a second temperature voltage; and a controller, configured to compare the first or second temperature voltage to a set temperature voltage and output the on-off signal, the second voltage acquisition circuit comprises a voltage divider circuit and a third current limiting circuit, and a second filter circuit; one signal input terminal is coupled to the second filter circuit to receive a sampling signal; and a current flow-in terminal of the third current limiting circuit is coupled to a power terminal, and a current flow-out terminal is coupled to the connection terminal.