Synchronous Rectification Controller Abnormal Protection
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Solution Overview
Problem
Conventional power conversion apparatuses fail to effectively protect the secondary side from abnormal conditions, such as over-temperature, due to parasitic diodes turning on and increasing power consumption, which prevents the synchronous rectification transistor from being turned off, leading to rising temperatures and ineffective protection.
Innovation Solution
The power conversion apparatus includes a synchronous rectification circuit where the synchronous rectification controller keeps the synchronous rectification transistor in an on state when an abnormal condition is detected, activating a short-circuit protection mechanism by short-circuiting the transformer, thereby preventing further energy transfer and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the synchronous rectification transistor is turned off to prevent temperature rise in abnormal conditions, then the temperature control is improved, but the parasitic diode turns on and power consumption increases dramatically
Solution Approach 1:
Instead of turning off the synchronous rectification transistor to protect against overheating (conventional approach), the patent inverts the strategy by keeping the transistor on and using the primary side short-circuit protection mechanism to detect and respond to abnormal conditions. This inversion avoids the parasitic diode conduction issue while achieving temperature protection.
Solution Approach 2:
The patent introduces the primary side short-circuit protection mechanism as an intermediary to detect secondary side abnormal conditions. By monitoring reflected current or voltage on the primary side, the system can detect secondary side faults without directly controlling the synchronous rectification transistor state, thus avoiding parasitic diode activation while maintaining protection functionality.
2Use of energy by moving object
If the synchronous rectification transistor is kept on to avoid parasitic diode conduction, then power consumption is reduced, but the temperature protection effect is lost
Solution Approach 1:
The patent implements feedback by using the primary side short-circuit protection mechanism to monitor secondary side conditions. When abnormal conditions are detected (such as over-temperature), the system provides feedback through reflected current or voltage changes, triggering the primary side protection to shut down the power switch, thus achieving temperature protection while keeping the synchronous rectification transistor on.
Solution Approach 2:
The primary side short-circuit protection mechanism serves as an intermediary that indirectly protects the synchronous rectification transistor from overheating. By detecting abnormal conditions through reflected parameters and activating primary side shutdown, the system achieves temperature protection without directly turning off the synchronous rectification transistor, thereby avoiding parasitic diode conduction.
3Reliability
If conventional short-circuit protection is used on the primary side, then primary side protection is achieved, but secondary side abnormal conditions cannot be detected
Solution Approach 1:
The patent makes the primary side short-circuit protection mechanism universal by enabling it to detect both primary side short-circuit conditions and secondary side abnormal conditions. Through reflected current or voltage monitoring, the same protection circuit achieves dual functionality: protecting against primary side faults and detecting secondary side abnormalities such as over-temperature or component failures.
Solution Approach 2:
The reflected current or voltage acts as an intermediary that carries information about secondary side conditions to the primary side protection mechanism. This intermediary enables the primary side protection circuit to detect secondary side abnormalities without direct secondary side sensing, thus achieving comprehensive protection while maintaining circuit simplicity.
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 effectively performs abnormal protection on the synchronous rectification circuit by maintaining the transistor in an on state during abnormal conditions, reducing temperature rise and achieving protection without additional anomaly indication signals, thus enhancing the apparatus's reliability and reducing hardware costs.
Implementation Method 1
The transformer has a primary winding and a secondary winding, wherein the primary winding receives an input voltage, and the secondary winding provides an output voltage to an output terminal
Implementation Method 2
a synchronous rectification transistor which has lower on-resistance may be used to as a substitute for the rectifying diode
Implementation Method 3
since there is a parasitic diode between a drain terminal and a body terminal of the synchronous rectification transistor, in the condition that the secondary side is in an over-temperature condition and the synchronous rectification transistor is off, when the energy stored in a primary side of the power conversion apparatus is transferred to the secondary side, the parasitic diode in the synchronous rectification transistor would be turned on
Data Source
AI summary
A power conversion apparatus and a synchronous rectification (SR) circuit thereof are provided. The power conversion apparatus includes a transformer and the SR circuit. A primary winding of the transformer receives an input voltage. A secondary winding of the transformer provides an output voltage to an output terminal. The SR circuit includes a SR transistor and a SR controller. The SR transistor is coupled between the secondary winding and the output terminal and controlled by a control signal. The SR controller is coupled to the SR transistor to receive a first detecting signal, and generates the control signal according to the first detecting signal. When the SR controller detects that the SR circuit is abnormal, the SR controller generates the controller signal to keep the SR transistor at an on state so as to perform an abnormal protection on the SR circuit.