Power Conversion Circuit Mode Transition Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional constant on-time power conversion circuits face issues with unstable output voltage when switching between continuous conduction mode (CCM) and discontinuous conduction mode (DCM), leading to insufficient energy supply and loss of PWM function in DCM.
Innovation Solution
A power conversion circuit with an error amplifying circuit that operates in two modes, controlled by comparison signals and an enabling signal, to maintain stable output voltage by adjusting the PWM signal frequency and enabling power pumping in DCM.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the power conversion circuit is switched from DCM to CCM, then the zero-current mechanism is turned off and inductor current forms negative current, but the output signal COMP remains at low-level causing slow PWM frequency and insufficient energy supply
Solution Approach 1:
The control circuit proactively detects the mode transition state and提前 adjusts the output signal COMP to high-level before the PWM frequency can become too slow, preventing insufficient energy supply and maintaining output voltage stability during the transition from DCM to CCM
Solution Approach 2:
The control circuit continuously monitors the operation mode and inductor current state, using this feedback to dynamically adjust the output signal COMP level, ensuring the PWM frequency and energy supply remain adequate during mode transitions
2Reliability
If the output signal COMP is limited to a fixed value during DCM period, then output voltage decrease is avoided, but the circuit loses PWM function and cannot provide power pumping or respond to transients
Solution Approach 1:
The output signal COMP is dynamically adjusted based on the detected operation mode: during DCM it is set to high-level to maintain voltage stability, while during CCM it returns to normal operation to enable PWM function and transient response, achieving both stability and adaptability at different times
Solution Approach 2:
The control circuit changes the parameter level of output signal COMP according to operation mode: high-level during DCM to prevent voltage decrease, and normal level during CCM to restore PWM functionality, thus resolving the contradiction between stability and adaptability
Data Source
AI summary
A power conversion circuit includes an error amplifying circuit, a first comparison circuit, a second comparison circuit and a control circuit. The error amplifying circuit provides an output signal. The first comparison circuit, coupled to the error amplifying circuit, receives the output signal and a ramp signal to generate a first comparison signal. The second comparison circuit receives an output voltage and a first reference voltage and provides a second comparison signal. The control circuit, coupled to the error amplifying circuit, the first comparison circuit and the second comparison circuit, provides a control signal to control the error amplifying circuit according to the first comparison signal, the second comparison signal and an enabling signal. In a first operation mode of error amplifying circuit, the output signal is an error amplifying signal. In a second operation mode of error amplifying circuit, the output signal is a second reference voltage.