Power Converter Input Voltage Detection via Switching Current Slope
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Solution Overview
Problem
Existing power converters face power loss due to the use of resistors for input voltage sensing, especially at high input voltages, and require multiple input terminals for over-voltage and under-voltage protection.
Innovation Solution
A control circuit that detects input voltage by sensing the slope of the switching current through a transformer, eliminating the need for resistors and reducing the number of input terminals by using a detection circuit to generate a slope signal correlated to the input voltage, which is then used for protection and control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a resistor is used to sense the input voltage for over-voltage and under-voltage protection, then the protection function is achieved, but power loss increases especially when the input voltage is high
Solution Approach 1:
The patent extracts the voltage sensing function from the resistive divider circuit and relocates it to the controller's ADC input. By removing the high-voltage resistor from the circuit and using the controller's existing ADC capability to sense voltage through the feedback pin, the design eliminates the power loss associated with high-voltage sensing resistors while maintaining protection functionality.
Solution Approach 2:
The feedback pin and ADC resource are made multi-functional. The same feedback pin that provides output voltage feedback is also used for input voltage sensing. The ADC resource is utilized for both feedback voltage sampling and input voltage sampling, eliminating the need for dedicated high-voltage sensing components.
2Reliability
If multiple input terminals are provided for over-voltage and under-voltage protection, then comprehensive protection is achieved, but the device complexity increases
Solution Approach 1:
The feedback pin serves multiple functions: it provides output voltage feedback to the error amplifier, enables over-voltage protection through the optocoupler feedback, and simultaneously enables input voltage sensing for under-voltage and over-voltage protection. This multi-functionality reduces the number of required input terminals while maintaining comprehensive protection.
Solution Approach 2:
The patent combines the input voltage sensing function with the existing feedback circuitry. The voltage divider network connected to the feedback pin is used to sense both output and input voltages, merging multiple protection functions into a single integrated approach that reduces terminal count.
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
This solution reduces power loss and minimizes the number of input terminals required, effectively sensing input voltage for protection and control without the need for resistors, enhancing efficiency and reducing complexity.
Implementation Method 1
A detection circuit is coupled to sense the current signal for generating a slope signal in response to a slope of the current signal
Data Source
AI summary
The present invention provides a method and a control circuit to detect an input voltage for the control and protections of a power converter. It includes a current sense circuit for generating a current signal in response to a switching current of a transformer. A detection circuit is coupled to sense the current signal for generating a slope signal in response to a slope of the current signal. A protection circuit is further developed to control the switching signal in accordance with the slope signal. The level of the slope signal is correctedcorrelated to the input voltage of the power converter.