Frequency Control Circuit for Switching Converter
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing frequency control methods for switching power supplies face challenges such as sub-harmonic oscillation in continuous conduction mode and increased chip costs due to the need for low-pass filters at low frequencies, especially when using fixed switching frequencies.
Innovation Solution
A frequency control circuit that regulates the off time or on time of a power transistor in a switching converter by switching between multiple operating states based on feedback signals, allowing the operating frequency to be maintained within a predetermined range without the need for slope compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If fixed switching frequency is used, then frequency control is simplified, but sub-harmonic oscillation occurs in continuous conduction mode and slope compensation is required
Solution Approach 1:
The patent implements dynamic frequency control by switching between multiple operating states (first, second, and third states) based on real-time conditions such as duty cycle ranges and current direction. The switching frequency dynamically adjusts between a first frequency and a second frequency, eliminating the need for fixed frequency operation while avoiding sub-harmonic oscillation without requiring slope compensation circuits.
Solution Approach 2:
The patent divides the operating range into multiple states with different frequency characteristics. By segmenting the control into distinct operating modes (first operating state, second operating state, third operating state), each optimized for specific duty cycle ranges, the system achieves stable operation across the full range without requiring complex slope compensation mechanisms.
2Speed
If low-pass filter is added to reduce frequency at low frequencies, then frequency control is improved, but chip cost increases
Solution Approach 1:
The patent uses dynamic frequency adjustment through state switching to control the switching frequency without requiring low-pass filters. By transitioning between operating states that have inherently different frequency characteristics, the system achieves frequency control at low operating points without adding expensive filter components to the chip.
Solution Approach 2:
The patent changes the switching frequency parameter dynamically by switching between different operating states. Instead of using fixed frequency operation with additional filtering components, the system modifies the frequency parameter itself through state transitions, eliminating the need for low-pass filters and reducing chip cost.
3Stability of the object's composition
If multiple operating states are implemented for frequency control, then frequency stability is improved, but device complexity increases
Solution Approach 1:
The patent implements dynamic state switching based on simple threshold comparisons of the duty cycle and current direction. The control circuit monitors basic parameters and automatically transitions between operating states, achieving frequency stability through dynamic adaptation rather than complex static control mechanisms.
Solution Approach 2:
The patent uses feedback from the duty cycle magnitude and current direction to automatically select the appropriate operating state. The control circuit continuously monitors these parameters and adjusts the switching frequency accordingly, maintaining stability through closed-loop control without requiring complex open-loop circuitry.
Data Source
AI summary
A frequency control circuit, applied in a switching converter, can be configured to: regulate an off time of a power transistor of the switching converter in one switching cycle according to an on time of the power transistor, or regulate the on time of the power transistor in one switching cycle according to the off time of the power transistor; and maintain an operating frequency of the switching converter to be within a predetermined range.