Power Factor Correcting Power Supply Transient Response
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Solution Overview
Problem
Conventional power factor correcting (PFC) power supplies experience poor load transient response due to their slow voltage control loop, which is necessary for maintaining good input waveform fidelity, leading to instability and increased ripple voltage, making them less suitable for applications requiring rapid current adjustments, such as audio amplifiers.
Innovation Solution
A power factor correcting power supply with a controlled current source and a control circuit that includes a current sensor, voltage sensor, and derived current calculator to determine the current at the output terminal exclusive of the bypass capacitor, allowing for immediate adjustment of the output current in response to load changes without affecting the voltage, thereby enhancing transient response and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a bypass capacitor is added to improve transient response, then the ability to provide current during transients is improved, but the control loop response speed deteriorates
Solution Approach 1:
The patent calculates the load current in advance by measuring the bypass capacitor current and subtracting it from the total current. This preliminary calculation allows the control loop to compensate for the capacitor's effect before it slows down the response, effectively preparing the system for transient conditions without waiting for the voltage drop to occur
Solution Approach 2:
The patent implements a feedback mechanism where the measured bypass capacitor current is fed back to the control circuit. This feedback allows the system to dynamically adjust the controlled current source output based on the actual capacitor behavior, maintaining stability while enabling fast transient response
2Reliability
If the voltage control loop is made slower to maintain input waveform fidelity, then power factor correction is improved, but load transient response deteriorates
Solution Approach 1:
The patent segments the current measurement into two components: total current from the current sensor and bypass capacitor current from the voltage sensor. By separating these measurements, the system can independently control the voltage loop for power factor correction while using the capacitor current measurement to enable fast transient response compensation
Solution Approach 2:
The patent uses the bypass capacitor as an intermediary element that serves dual purposes: it maintains slow voltage control for good power factor while its current measurement serves as a mediator signal that enables fast transient response through the control circuit's calculation and adjustment mechanisms
3Power
If a bypass capacitor is used to provide current during transients, then transient current capability is improved, but output voltage stability deteriorates
Solution Approach 1:
The control circuit uses feedback from the voltage sensor measuring bypass capacitor voltage to calculate the capacitor current. This feedback loop allows the system to monitor and compensate for voltage deviations caused by the capacitor, maintaining output voltage stability while utilizing the capacitor's transient current capability
Solution Approach 2:
The patent replaces the traditional mechanical/voltage-based voltage stabilization mechanism with an electronic calculation and control approach. Instead of relying solely on voltage feedback, the system substitutes a current calculation method that uses measured values and mathematical operations to determine and adjust the controlled current source output, achieving faster and more precise voltage stability
Data Source
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AI summary
A power factor correcting power supply. The power factor correcting power supply includes a controlled current source for providing electrical power of a regulated current and a regulated voltage to a first output terminal, a voltage comparison current controller, and a control circuit responsive to the current at the output terminal, the control circuit coacting with the voltage comparison current controller to cause the controlled current source to increase or decrease the current at the first output terminal.