Power Conversion Circuit With Adjusted Reference Voltage Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional power conversion circuits with ripple-based constant on-time control schemes face instability and inaccurate output voltage due to sub-harmonic oscillations caused by small equivalent series resistors in output capacitors.
Innovation Solution
A power conversion circuit is designed with a control circuit that includes a reference signal generation circuit to generate an adjusted reference voltage, a comparator to compare the output voltage with the adjusted reference voltage, and an on-time control circuit to control the main switch based on the comparison signal, thereby improving system stability and output voltage accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the equivalent series resistor ESR of the output capacitor is reduced to improve efficiency and reduce losses, then energy loss decreases, but sub-harmonic oscillation occurs causing system instability
Solution Approach 1:
The patent implements a feedback mechanism by comparing the output voltage with a reference voltage using a comparator. The comparator generates a control signal based on the voltage difference, which feeds back to adjust the switching duty cycle. This closed-loop feedback system compensates for the instability caused by low ESR values, maintaining system stability while allowing efficient operation with modern low-ESR capacitors.
Solution Approach 2:
The patent dynamically adjusts the reference voltage parameter based on the operating conditions. By changing the reference voltage level adaptively, the control system can maintain optimal performance across different load conditions and compensate for the reduced damping effect of low ESR capacitors, thereby preventing sub-harmonic oscillation while preserving energy efficiency.
2Reliability
If the equivalent series resistor ESR is reduced using multi-layer ceramic capacitors, then the output capacitor performance improves, but the ripple voltage becomes too small triggering sub-harmonic oscillation
Solution Approach 1:
The comparator-based feedback control continuously monitors the output voltage and adjusts the switching duty cycle in real-time. This active feedback mechanism replaces the passive stability provided by high ESR values, enabling the system to remain stable even with low-ESR MLCC capacitors that provide superior performance characteristics.
Solution Approach 2:
The patent introduces an intermediary control circuit between the voltage feedback and the switching control. This intermediary processing stage shapes the control signal to prevent sub-harmonic oscillation, allowing the system to benefit from low-ESR capacitors without sacrificing stability. The intermediary control logic acts as a mediator that reconciles the conflict between low ESR and system stability.
3Device complexity
If the negative feedback control mechanism triggers only when the valley value of output voltage reaches the reference voltage, then the control timing is simplified, but the output voltage accuracy deteriorates when ripple increases
Solution Approach 1:
The patent transitions from a static threshold-based trigger to a dynamic reference voltage adjustment mechanism. The reference voltage is adaptively modified based on the detected valley point timing and ripple characteristics. This dynamic adjustment allows the simplified valley-triggered control to maintain high output voltage accuracy even when ripple varies with load conditions, resolving the contradiction between control simplicity and precision.
Data Source
AI summary
A power conversion circuit is provided, which includes a control circuit. The control circuit includes a reference signal generation circuit, a comparator, an on-time control circuit and a driving circuit. The reference signal generation circuit is configured to compensate for a first reference voltage and generate an adjusted reference voltage. The reference signal generation circuit includes an operational amplifier circuit, a compensation capacitor and a compensation branch circuit. The operational amplifier circuit is configured to receive the first reference voltage and accordingly generate the adjusted reference voltage. The comparator is configured to output a comparison signal according to a signal related to the first output voltage and a signal related to the adjusted reference voltage. The on-time control circuit is configured to generate an on-time control signal according to the comparison signal. The driving circuit is configured to generate a driving control signal according to the on-time control signal.