PWM Frequency Control for Switch Power Dissipation
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Solution Overview
Problem
Existing PWM control techniques for switches do not effectively manage power dissipation during switch transitions, particularly in electric motor applications, leading to inefficiencies and potential overheating issues.
Innovation Solution
A method and apparatus that adjust the frequency of pulse-width-modulated signals to switches based on sensed parameters such as temperature, speed, or current, comparing these parameters to threshold values to optimize power efficiency and prevent overheating by altering the PWM frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If PWM frequency is increased to improve power control precision, then power dissipation during switch transitions increases
Solution Approach 1:
The patent applies dynamics by making the PWM frequency adjustable rather than fixed. The controller dynamically changes the PWM frequency based on operating conditions, allowing optimization between control precision and power dissipation. When high precision is needed, higher frequencies are used; when power efficiency is prioritized, lower frequencies are selected.
Solution Approach 2:
The patent changes the PWM frequency parameter adaptively based on operating conditions. By varying this key parameter, the system can optimize performance across different operating points, resolving the contradiction between maintaining high control precision and minimizing power dissipation during switch transitions.
2Speed
If PWM frequency is increased to improve response speed, then switch temperature increases
Solution Approach 1:
The system dynamically adjusts PWM frequency based on thermal conditions. When switch temperature rises, the frequency is reduced to allow cooling, preventing thermal runaway. When temperature is acceptable, higher frequencies can be used for faster response, thus resolving the contradiction between response speed and temperature control.
Solution Approach 2:
The patent incorporates feedback mechanisms that monitor switch temperature and adjust PWM frequency accordingly. This closed-loop control ensures that response speed requirements are met when thermal conditions permit, while preventing overheating by reducing frequency when temperature thresholds are approached.
3Loss of energy
If PWM frequency is decreased to reduce power dissipation, then control precision deteriorates
Solution Approach 1:
Rather than using a fixed low frequency, the system dynamically selects PWM frequency based on current operating requirements. This allows the system to achieve low power dissipation during steady-state operation with relaxed precision requirements, while maintaining high control precision when needed by increasing frequency temporarily.
4Temperature
If PWM frequency is decreased to reduce switch temperature, then response speed deteriorates
Solution Approach 1:
The system uses dynamic frequency adjustment to balance temperature and response speed. During transient conditions requiring fast response, higher frequencies are applied temporarily. During steady-state operation, lower frequencies reduce temperature while maintaining acceptable response characteristics.
Data Source
AI summary
An improved apparatus for controlling and providing a pulse-width-modulated signal to a switch operatively arranged between two terminals of a power supply for controlling an output power. A controller provides a pulse-width-modulated gate signal at a frequency to the switch. The controller is arranged to adjust the frequency as a function of a sensed parameter such that the power dissipated in the switch during switch transitions may be adjusted.