Offline Power Converter Control Circuit Without Input Capacitor
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Solution Overview
Problem
Conventional offline power converters rely on bulk capacitors for filtering, which occupy significant space, reduce lifespan, and increase manufacturing costs; a control circuit that can regulate output without bulk capacitors is needed to address these issues.
Innovation Solution
A control circuit comprising a switching circuit, input-voltage detection circuit, and current-limit threshold that generates a switching signal and adjusts the maximum duty and current limit to regulate the power converter's output, eliminating the need for bulk capacitors by detecting input voltage and adjusting the switching signal and current limit accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a bulk capacitor is used to filter pulsating DC input voltage, then the input voltage becomes smoother with small ripple, but the power converter occupies significant space, has reduced lifespan, and increased manufacturing cost
Solution Approach 1:
The patent removes the bulk capacitor from the power converter circuit entirely. Instead of filtering the pulsating DC input voltage through a capacitor, the invention uses a control circuit that detects the pulsating input voltage and dynamically adjusts the switching duty cycle to maintain stable output voltage without requiring energy storage capacitors at the input stage.
Solution Approach 2:
The patent employs a dynamic control mechanism where the control circuit continuously monitors the pulsating DC input voltage and adjusts the switching duty cycle in real-time. This dynamic adjustment compensates for the voltage ripple that would traditionally require a bulk capacitor, allowing the system to maintain stable operation without static energy storage components.
2Reliability
If a bulk capacitor is used to store energy and provide minimum input voltage, then the power converter operates properly, but the manufacturing cost increases
Solution Approach 1:
The patent eliminates the bulk capacitor component from the circuit design, thereby removing the associated manufacturing costs of capacitor procurement, placement, and testing. The energy storage function traditionally performed by the capacitor is replaced by the dynamic switching control mechanism that regulates power flow directly from the rectified input.
Solution Approach 2:
The patent replaces the passive energy storage mechanism (capacitor) with an active control system that uses electronic switching and feedback control to achieve the same reliability outcome. This substitution transitions from a component-based solution to a control-based solution, reducing bill of materials cost while maintaining operational reliability.
3Stability of the object's composition
If a bulk capacitor is used to filter pulsating DC, then the input voltage is stabilized, but the output line ripple increases without the filtering operation
Solution Approach 1:
The control circuit performs preliminary detection of the pulsating DC input voltage characteristics before the voltage reaches the output stage. By detecting the input voltage variations in advance, the control circuit pre-adjusts the switching duty cycle to compensate for upcoming voltage dips or peaks, preventing output voltage ripple before it occurs.
Solution Approach 2:
The patent implements a feedback control mechanism where the output voltage is continuously monitored and compared against a reference. The error signal generated from this comparison feeds back to the control circuit, which adjusts the switching duty cycle to eliminate output voltage deviations. This closed-loop feedback compensates for input voltage pulsations without requiring input-stage filtering capacitors.
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 output line ripple, extends the power converter's lifespan, and decreases manufacturing costs by eliminating the need for bulk capacitors, while maintaining stable operation and reducing transformer saturation.
Implementation Method 1
The switching circuit generates a switching signal coupled to switch a transformer of the power converter for regulating an output of the power converter
Implementation Method 2
The input-voltage detection circuit detects a DC input voltage of the power converter via the transformer. The input voltage of the power converter is correlated to the DC input voltage of the power converter.
Data Source
AI summary
The present invention provides a control circuit for a power converter. The control circuit includes a switching circuit, an input-voltage detection circuit and a current-limit threshold. The switching circuit generates a switching signal coupled to switch a transformer of the power converter for regulating an output of the power converter in response to a feedback signal. The input-voltage detection circuit generates a control signal when an input voltage of the power converter is lower than a low-input threshold. The feedback signal is generated in response to the output of the power converter. A maximum duty of the switching signal is increased in response to the control signal. The current-limit threshold is for limiting a maximum value of a switching current flowing through the transformer. The current-limit threshold is increased in response to the control signal. An input of the power converter doesn't connect with electrolytic bulk capacitors.