Flyback Power Supply Control Unit for Transient Response and Ringing Suppression
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Solution Overview
Problem
Isolation type flyback switching power supply devices face issues with transient response speed, peak primary side current variation, switching frequency fluctuation, insufficient output voltage increase during overcurrent protection, inaccurate feedback signal accuracy, and ringing suppression without using a Snubber circuit.
Innovation Solution
A power supply control unit that includes an on trigger signal generating unit, timers for measuring minimum OFF time and ON time, a minimum OFF time setting unit, an on timing determining unit, and an overcurrent protection unit, which dynamically adjusts the OFF time and feedback signal output timing to enhance transient response, reduce peak current, and suppress ringing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the OFF time is set to the minimum OFF time to enable faster switching, then the switching speed is improved, but the transient response speed is decreased and the peak value of the primary side current increases
Solution Approach 1:
The patent dynamically adjusts the OFF time based on the actual discharge status of excitation energy in the transformer. The control unit extends the OFF time beyond the minimum OFF time when excitation energy is not sufficiently discharged, and uses the minimum OFF time when excitation energy is sufficiently discharged. This dynamic adjustment resolves the contradiction by adapting the switching timing to real-time energy conditions, achieving both fast switching and fast transient response.
2Productivity
If the OFF time is set to the minimum OFF time to increase switching frequency, then the switching frequency is improved, but the fluctuation of switching frequency is increased
Solution Approach 1:
The control unit monitors the discharge status of excitation energy in the transformer and uses this feedback information to adjust the OFF time. When excitation energy is not sufficiently discharged, the OFF time is extended to ensure complete discharge before the next switching cycle. This feedback mechanism stabilizes the switching frequency by preventing premature switching that would cause frequency fluctuations, while still maintaining high switching frequency operation.
3Speed
If the switching element is turned off for minimum OFF time to enable faster protection response, then the protection response speed is improved, but the output voltage increase becomes slow
Solution Approach 1:
During overcurrent protection, the control unit dynamically extends the OFF time beyond the minimum OFF time to ensure complete discharge of excitation energy in the transformer. This dynamic extension allows the output voltage to increase more quickly by fully releasing stored energy, while still maintaining fast protection response capability. The resolution lies in adapting the OFF time duration to the specific protection scenario.
4Productivity
If the OFF time is extended to improve transient response, then the transient response speed is improved, but the switching frequency fluctuation is increased
Solution Approach 1:
The control unit dynamically adjusts the OFF time based on the actual discharge status of excitation energy. The OFF time is extended only when and only to the extent necessary to fully discharge excitation energy, rather than using a fixed extended OFF time. This dynamic approach achieves fast transient response by ensuring complete energy discharge while minimizing unnecessary OFF time extensions that would cause switching frequency fluctuations.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution achieves faster transient response, reduces peak primary side current variation, stabilizes switching frequency, accelerates output voltage increase during overcurrent protection, improves feedback signal accuracy, and effectively suppresses ringing without a Snubber circuit, thereby enhancing the overall performance of the power supply device.
Implementation Method 1
When the switching element is turned on, excitation energy is stored in the transformer. When the switching element is turned off, the excitation energy is discharged through a diode and a smoothing capacitor disposed on the secondary side of the transformer.
Data Source
AI summary
The power supply control unit includes an on trigger signal generating unit arranged to generate an on trigger signal for turning on the switching element on the basis of a feedback signal of flyback voltage, a first timer arranged to measure a predetermined minimum OFF time, a second timer arranged to measure time based on an ON time, a minimum OFF time setting unit arranged to compare the predetermined minimum OFF time measured by the first timer with the time measured by the second timer so as to set a longer time as a minimum OFF time, and an on timing determining unit arranged to determine timing for turning on the switching element on the basis of the set minimum OFF time and the on trigger signal.