Flyback Power Supply Dynamic Response via Secondary-Side Rectifier Control
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Solution Overview
Problem
Conventional flyback switching power supplies experience poor dynamic response performance due to low sampling frequency under light-load or no-load conditions, leading to delayed detection of output voltage changes and subsequent drops in output voltage when loading conditions change.
Innovation Solution
A flyback switching power supply with a control circuit that includes a primary-side controller and a secondary-side controller, where the rectifier is turned on for a transient period when the output voltage drops below a threshold, generating a negative current or voltage change detectable by the primary-side controller, which then controls the main power switch to turn on, improving dynamic response by preventing direct connection between the primary and secondary sides.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the primary-side controller samples the output voltage directly by the auxiliary winding under light-load or no-load condition, then the switching frequency drops to reduce standby loss, but the sampling frequency becomes very low causing poor dynamic response performance
Solution Approach 1:
The secondary-side controller performs preliminary detection of output voltage changes and proactively sends turn-on signals to the rectifier before the primary-side controller can detect the voltage drop, enabling the primary side to prepare for upcoming load changes and respond faster when they occur
Solution Approach 2:
A feedback mechanism is established where the secondary-side controller continuously monitors output voltage and communicates status to the primary-side controller through rectifier control signals, creating a closed-loop system that enables faster joint response to load changes
2Ease of operation
If the primary-side controller detects output voltage changes after the switch turns off and turns on, then the control can be implemented, but it requires a long time to detect changes and improve switching frequency under sudden load changes
Solution Approach 1:
The secondary-side controller performs preliminary detection of output voltage changes and sends turn-on signals to the rectifier before the primary-side controller needs to detect the voltage drop, enabling the primary side to prepare for upcoming load changes
Solution Approach 2:
The rectifier control signal serves as an intermediary that transmits information about output voltage status from the secondary side to the primary side, eliminating the need for the primary-side controller to directly sample and detect voltage changes
3Reliability
If the rectifier is controlled to turn on for a transient period when output voltage drops below threshold, then the dynamic response is improved, but there is a risk of direct connection between primary and secondary sides
Solution Approach 1:
The patent replaces direct electrical connection control with magnetic coupling through the transformer, where the primary-side controller uses electromagnetic induction to control the main power switch based on detected signals, eliminating direct electrical contact between primary and secondary sides
Solution Approach 2:
The transformer acts as an intermediary that transfers energy and control signals between primary and secondary sides through magnetic coupling, preventing direct electrical connection while enabling coordinated control to maintain output voltage stability
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
This solution enhances the dynamic response to sudden changes in loading conditions by quickly determining output voltage drops and adjusting the main power switch, efficiently avoiding direct connections and maintaining stable output voltage.
Implementation Method 1
the transformer comprises a primary winding and a secondary winding, the main power switch is connected with the primary winding
Implementation Method 2
the rectifier is connected with the secondary winding
Data Source
AI summary
A flyback switching power supply, comprising a main power switch, a transformer and a rectifier is described. The transformer comprises a primary winding and a secondary winding, the main power switch is connected with the primary winding, the rectifier is connected with the secondary winding. When the output voltage of the flyback switching power supply is lower than a first threshold value, the rectifier is controlled to be turned on for a transient period; by detecting the negative current flowing through the main power switch, performing integral operation on the voltage across the auxiliary winding, and sampling the peak voltage of the drain-to-source voltage of the main power switch for several times, whether the rectifier is turned on can be determined if the output voltage at the secondary side is lower than the threshold voltage, and the main power switch is controlled to be turned on accordingly.