Inductor Discharge IC with Temperature Protection
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Solution Overview
Problem
High-side switches in electromagnetic relays face thermal damage due to high power dissipation during fast demagnetization of inductive loads, as they lack the ability to control coil current effectively, leading to permanent damage above a certain energy level.
Innovation Solution
An integrated circuit with a high-side switch, Zener diode, and temperature-sensing circuit that selectively engages additional transistors to switch between fast and slow demagnetization modes based on temperature, reducing power dissipation and preventing thermal overload.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If fast demagnetization is implemented using a high-side switch with Zener diode clamping, then the coil current transitions to zero quickly preserving the electromagnetic relay, but the IC generates high thermal power that causes rapid heating and eventual permanent damage
Solution Approach 1:
The patent implements dynamic switching between two demagnetization modes (fast and slow) based on real-time temperature monitoring. The system transitions from a static demagnetization approach to a dynamic one where the demagnetization rate adjusts according to thermal conditions, allowing fast demagnetization when cool and slow demagnetization when hot, thus resolving the contradiction between speed and temperature.
Solution Approach 2:
The patent introduces a temperature sensing circuit that continuously monitors IC temperature and feeds this information back to the control logic. This feedback mechanism enables the system to detect when the IC approaches dangerous temperature thresholds and automatically adjust the demagnetization rate accordingly, preventing thermal damage while maintaining fast demagnetization capability when safe.
2Duration of action of moving object
If the high-side switch relies solely on power dissipation capability to maintain temperature, then the coil current can continue flowing without interruption, but the IC eventually fails and is permanently damaged above certain energy levels
Solution Approach 1:
The patent implements periodic alternation between fast and slow demagnetization phases. During fast demagnetization, the IC dissipates high power briefly; then during slow demagnetization, the IC cools down. This periodic cycling allows the coil current to continue flowing through the system while the IC recovers thermally between high-power episodes, maintaining both current continuity and device reliability.
Solution Approach 2:
The temperature sensing and control circuitry provides beforehand cushioning by detecting approaching thermal limits before damage occurs. The system proactively switches to slow demagnetization mode when temperature thresholds are approached, preventing catastrophic failure before it happens and ensuring the IC remains within safe operating parameters throughout the demagnetization process.
3Temperature
If additional transistors are engaged to switch between fast and slow demagnetization modes, then power dissipation is reduced and thermal overload is prevented, but the device complexity increases
Solution Approach 1:
The patent designs the additional transistors and temperature sensing circuitry to serve multiple functions: the sensing circuit monitors temperature, the control logic determines demagnetization mode, and the additional transistors execute the switching between fast and slow modes. This multi-functionality reduces the need for separate dedicated components for each function, thereby limiting the increase in overall device complexity while achieving effective temperature control.
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 allows for safe demagnetization of inductive loads without damage, enabling the use of smaller IC packages and maintaining performance by reducing thermal stress through controlled power dissipation, extending the lifespan of the high-side switch.
Implementation Method 1
A temperature sensing circuit is configured to sense a temperature of the switch and to generate a sensed temperature
Implementation Method 2
A comparing circuit includes inputs that receive a reference temperature and the sensed temperature and an output connected to the control terminals of the first and second transistors
Implementation Method 3
During an 'ON' phase, the high-side switch delivers current to the coil. The coil generates magnetic force to keep contacts of the electromagnetic relay closed
Implementation Method 4
Fast demagnetization may be accomplished by making the switch behave as a high-voltage Zener diode, which clamps a voltage of the coil at about VZener=50V below VDD
Implementation Method 5
During fast demagnetization, an integrated circuit (IC) will generate thermal power (P=VZener*Iinductor) that can become very high when large relays are used
Data Source
AI summary
An integrated circuit for demagnetizing an inductive load includes a first switch to control current supplied by a voltage supply to the inductive load. A Zener diode includes an anode connected to a control terminal of the first switch and a cathode connected to the voltage supply. A second switch includes a control terminal and first and second terminals. A temperature sensing circuit is configured to sense a temperature of the first switch and to generate a sensed temperature. A comparing circuit includes inputs that receive a reference temperature and the sensed temperature and an output connected to the control terminal of the second switch.