Power Converter Peak Current Mode Control Duty Cycle
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Solution Overview
Problem
Conventional power converters using constant on-time control mode are limited by minimum-off time signals, preventing the achievement of a maximum duty cycle of 100% due to restrictions on the duty cycle of the power converter, particularly in high-frequency applications requiring high input voltage regulation.
Innovation Solution
A control circuit and logic circuit configuration that generates a constant off-time signal based on a ramp signal and error signal, allowing the power converter to switch between valley current and peak current control modes, thereby increasing the duty cycle by varying the control signal according to the on-time periods of the constant off-time and constant on-time signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If constant on-time control mode is used with minimum-off time signal, then power converter operation is stabilized, but duty cycle is limited and maximum 100% cannot be achieved
Solution Approach 1:
The patent implements dynamic switching between two control modes: constant on-time control mode (for normal operation stability) and constant off-time control mode (for achieving 100% duty cycle). The controller dynamically selects the appropriate mode based on operating conditions, allowing the system to transition from static to dynamic control strategy to resolve the contradiction between stability and duty cycle expansion.
Solution Approach 2:
The patent changes the control parameter from fixed on-time duration to variable off-time duration. By introducing constant off-time control mode where the off-time is held constant rather than the on-time, the system can achieve 100% duty cycle when needed while maintaining stability through parameter adaptation based on operating conditions.
2Reliability
If high input voltage is used in high frequency applications, then output voltage regulation is maintained, but duty cycle limitation prevents achieving maximum performance
Solution Approach 1:
The patent enables dynamic adaptation of control strategy based on input voltage and load conditions. When high input voltage is present in high-frequency applications, the controller can switch to constant off-time mode to achieve 100% duty cycle, thereby maintaining output voltage regulation while eliminating the duty cycle limitation that would otherwise prevent maximum performance.
Data Source
AI summary
Methods and apparatuses for regulating a power converter are described. A device comprising a control circuit and a logic circuit can be integrated in a controller coupled to the power converter. The control circuit can generate a constant off-time signal based on a ramp signal and an error signal. The logic circuit can generate a control signal based on the constant off-time signal and a constant on-time signal. The logic circuit can output the control signal to the power converter. In response to an on-time period of the constant off-time signal being less than an on-time period of the constant on-time signal, the control signal can vary according to the constant on-time signal. In response to the on-time period of the constant off-time signal being greater than the on-time period of the constant on-time signal, the control signal can vary according to the constant off-time signal.