Switching Regulator Control Circuit for Noise Suppression and Duty Cycle Regulation
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Solution Overview
Problem
Switching regulators face limitations in voltage regulation due to noise signals generated during the turning on and off of switches, which can lead to malfunction and control failures, and the use of minimum off time circuits restricts the duty cycle, limiting the regulation range, especially at high output voltages.
Innovation Solution
A control circuit for switching regulators that includes an ON signal generator, an OFF signal generator, an on time regulator, and a logic circuit to regulate the on time of the switch based on the off time, allowing for constant on time when off time is greater than or equal to a reference time, and adjusting on time when off time is less than the reference time to maintain duty cycle regulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If minimum off time circuits are used to suppress noise signals, then noise suppression is improved, but duty cycle range is restricted
Solution Approach 1:
The patent implements dynamic adjustment of the off-time period based on operating conditions. The off-time is extended only when noise signals are detected or when operating at high duty cycles, rather than maintaining a fixed minimum off-time. This dynamic approach allows the circuit to suppress noise when needed while maintaining full duty cycle range when noise is not present, resolving the contradiction between noise suppression and duty cycle versatility.
Solution Approach 2:
The patent changes the off-time parameter dynamically based on operating conditions such as noise detection or duty cycle level. By adjusting the off-time period from a fixed value to a variable parameter that adapts to operating conditions, the system achieves noise suppression only when necessary, thereby preserving the full duty cycle range for normal operation and resolving the contradiction between reliability and adaptability.
2Reliability
If constant on time control is used, then switching frequency stability is improved, but voltage regulation capability is reduced
Solution Approach 1:
The patent transitions from constant on-time control to dynamic on-time control where the on-time period adjusts based on voltage regulation requirements. The control circuit monitors output voltage and dynamically modifies the on-time to maintain proper voltage regulation across the full duty cycle range, while the off-time is dynamically adjusted to maintain stable switching frequency, thus resolving the contradiction between frequency stability and voltage regulation capability.
Solution Approach 2:
The patent employs periodic measurement and adjustment of the on-time period based on voltage feedback. By continuously monitoring output voltage and periodically adjusting the on-time parameter in response to voltage deviations, the system maintains both stable switching frequency and effective voltage regulation across the complete duty cycle range, overcoming the limitations of constant on-time control.
Data Source
AI summary
A control circuit for a switching regulator can include: an ON signal generator that generates an ON signal; an OFF signal generator that generates a first control signal according to an input voltage and an output voltage of the switching regulator; an on time regulator that generates an adjustment signal according to a switching signal and the first control signal; and a logic circuit configured to generate an off signal according to the first control signal, and to generate the switching signal according to the ON signal and the OFF signal, where the on time of the first switch is regulated according to the off time of the first switch when the off time of the first switch is less than the reference time, in order to regulate a duty cycle of the switching signal.