Decoupled Circuit Simulation for Self-Heating Analysis
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Solution Overview
Problem
Circuit simulation methods face challenges in accurately modeling self-heating effects, leading to increased computational complexity and convergence issues due to the need to calculate derivatives of outputs and intermediate variables with respect to temperature, which often results in incomplete models and longer simulation times.
Innovation Solution
A method that updates device temperatures only between time steps during transient simulation, avoiding the need to calculate derivatives with respect to temperature, by decoupling the time scale of temperature changes from electrical changes, and using iterative techniques to solve non-linear equations for electrical and temperature responses separately.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If circuit simulation includes modeling of self-heating by treating temperature as another freedom like node voltages, then the simulation can capture temperature effects on device behavior, but the computational complexity increases significantly due to the need to derive derivatives of all outputs and intermediate variables with respect to temperature
Solution Approach 1:
The simulation process is segmented into two distinct phases: an electrical simulation phase that determines electrical responses (voltages, currents) without temperature coupling, and a thermal simulation phase that uses those electrical responses to calculate power dissipation and update temperatures. This segmentation eliminates the need to compute temperature derivatives during electrical simulation, reducing computational complexity while maintaining temperature accuracy.
Solution Approach 2:
The temperature variable is extracted from the electrical simulation equations and handled separately in a dedicated thermal simulation phase. By removing temperature from the electrical system of equations, the patent eliminates the need to derive and compute temperature-related derivatives during electrical analysis, significantly reducing computational burden.
2Reliability
If circuit simulators support modeling of self-heating with complete derivatives, then the simulation can accurately model temperature effects, but convergence problems occur due to bugs and incomplete derivatives in the self-heating model
Solution Approach 1:
By separating electrical and thermal simulations into distinct phases, the patent eliminates the coupling that causes convergence problems. The electrical simulation converges using only electrical variables, and the thermal simulation converges using power dissipation from electrical results, avoiding the convergence issues that arise from incomplete temperature derivatives in coupled simulations.
3Measurement precision
If circuit simulation derives derivatives of all outputs and intermediate variables with respect to temperature, then the simulation can accurately model self-heating effects, but the simulation time increases compared to simulators that do not support self-heating
Solution Approach 1:
The patent segments the simulation into electrical and thermal phases, allowing the electrical simulation to proceed at full speed without temperature derivative calculations. The thermal simulation runs separately using power dissipation data, maintaining self-heating accuracy while preserving simulation speed.
Solution Approach 2:
The electrical responses (voltages, currents) are determined first in a preliminary electrical simulation phase before thermal effects are calculated. This preliminary action allows the thermal simulation to use fixed electrical parameters to compute power dissipation and temperature updates, avoiding the need for iterative temperature derivative calculations during electrical analysis.
Data Source
AI summary
A solution of a first set of equations of the time-varying electrical response of a circuit is determined between pairs of adjacent time points ti and ti+1 based on predicted electrical responses of the devices at time point ti+1 and as a function of the initial temperatures of the circuit devices at time point ti. A solution of a second set of equations of the time-varying temperature responses of devices of the circuit is determined (1) after each iteration of the first set of equations and as a function thereof or (2) at each time point ti+1 and as a function of the solution of the first set of equations at the time point to determine the corresponding temperature response of the circuit. The solutions of the first and second sets of equations at one or more of the points in time are displayed.