Power Factor Correction Device Offset Voltage Sensing Method
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Solution Overview
Problem
Existing power factor correction (PFC) devices face inaccuracies in current sensing due to aging and thermal effects affecting the offset voltage, leading to distortion and reduced sensing accuracy.
Innovation Solution
A current sensing method that determines a sense value of the offset voltage based on actual sampling results, using a minimum sampling voltage from multiple sampling voltages to calculate the current, which is updated periodically, thereby compensating for fluctuations and ensuring accurate current sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a constant voltage source is used to generate offset voltage, then the amplitude of sense voltage is boosted to avoid signal distortion, but aging and thermal effects cause the actual output voltage to deviate from nominal value, reducing current sensing accuracy
Solution Approach 1:
The patent implements a feedback mechanism where the actual offset voltage is continuously sampled and measured. The measured offset voltage value is fed back to the control system, which then uses this information to compensate for deviations from the nominal value. This closed-loop feedback approach ensures that aging and thermal effects do not permanently degrade sensing accuracy, as the system automatically adapts to the actual offset voltage conditions.
Solution Approach 2:
The patent dynamically adjusts the sensing calculation by changing the parameter used for offset compensation. Instead of using a fixed nominal offset voltage value, the system samples the actual offset voltage and uses this measured parameter in subsequent current calculations. This parameter change approach allows the system to maintain accuracy despite variations in offset voltage due to aging or temperature changes.
2Device complexity
If the negative power supply port of the operational amplifier is grounded, then the circuit structure is simplified, but the output signal amplitude becomes close to 0V causing large distortion
Solution Approach 1:
The patent introduces an offset voltage as an intermediary element between the operational amplifier and the sensing circuit. This offset voltage acts as a mediator that lifts the signal level from near 0V to a higher amplitude range, preventing signal distortion while maintaining the simplified grounded configuration. The offset voltage serves as a bridge that allows the operational amplifier to operate with a grounded negative supply while still producing usable signal levels.
3Productivity
If the offset voltage sense value is not updated periodically, then the circuit operation is simple, but errors accumulate due to aging and thermal effects
Solution Approach 1:
The patent implements periodic sampling of the offset voltage at predetermined intervals. This periodic action allows the system to maintain simplicity in normal operation while periodically updating the offset voltage sense value to compensate for aging and thermal effects. The periodic update mechanism balances operational efficiency with accuracy maintenance, as the system does not require continuous monitoring but rather regular refreshes of the offset voltage information.
Data Source
AI summary
A PFC device includes at least one main switch, a converter that converts a current to be sensed in the PFC device into a voltage to be sensed, the PFC device generating a switch control signal to control the at least one main switch based on the current to be sensed, and a voltage sensor that receives the voltage to be sensed and an offset voltage, and senses the voltage to be sensed using the offset voltage to output a sense voltage. A method includes sampling the sense voltage, determining a sense value of the offset voltage based on a sampling result, and calculating the current to be sensed based on a difference between the sense voltage and the sense value.