PWM Controller Over-Temperature Protection Pin Reduction
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Solution Overview
Problem
Conventional PWM controllers for power converters require an additional pin for over-temperature protection, increasing the pin count and costs without compromising functionality.
Innovation Solution
A PWM controller design that integrates an over-temperature protection circuit using a thermal resistor and a signal generator to adjust the driving signal across the thermal resistor during the off-period of the switching signal, enabling over-temperature detection and protection without additional pins by utilizing a saw-tooth signal and comparison circuits to disable the power converter when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an independent pin is used for over-temperature protection in conventional controllers, then over-temperature protection function is achieved, but pin count increases and cost increases
Solution Approach 1:
The patent merges the over-temperature protection function with the existing driving signal output pin by utilizing the off-period of the switching signal to adjust the driving signal across the thermal resistor. This integration eliminates the need for an independent over-temperature protection pin, thereby reducing pin count while maintaining the protection function.
Solution Approach 2:
The driving signal output pin is designed to serve dual purposes: normal power converter operation during the on-period and over-temperature detection during the off-period. By making the pin multi-functional, the patent avoids increasing pin count while achieving over-temperature protection.
2Reliability
If an independent pin is used for over-temperature protection, then over-temperature protection function is achieved, but controller cost increases
Solution Approach 1:
The patent combines the over-temperature protection circuitry with existing controller components, specifically utilizing the driving signal generation circuitry and the thermal resistor. This merging approach eliminates the need for additional independent pins and associated external components, thereby reducing manufacturing cost.
Solution Approach 2:
The controller uses its own internal resources (driving signal circuitry and thermal resistor) to perform over-temperature protection without requiring additional external pins or components. This self-service approach reduces bill of materials cost and simplifies manufacturing.
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 effectively reduces the pin count while maintaining original protection functions, ensuring reliable over-temperature protection for power converters by adjusting the driving signal based on environmental temperature and disabling the power converter when over-temperature conditions are met.
Implementation Method 1
The thermal resistor is a negative temperature coefficient resistor. A level of the driving signal decreases as an environmental temperature of the power converter increases during the off-period of the switching signal.
Implementation Method 2
The comparator compares a threshold voltage with the driving signal during the off-period of the switching signal to generate an over-temperature signal.
Data Source
AI summary
The present invention provides a power converter. The power converter includes a transformer, a power switch and a controller. The transformer has a primary winding, a secondary winding and an auxiliary winding. The power switch is coupled to the primary winding of the transformer to regulate the power converter. The controller has an output terminal for generating a driving signal to switch the power switch in response to a switching signal. A thermal resistor is coupled to the output terminal of the controller. The driving signal is adjusted across the thermal resistor during an off-period of the switching signal.