Synchronous Rectifier Drive Circuit with Blanking Time Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Synchronous rectifiers in power converters can malfunction due to resonance phenomena when a soft load is applied, leading to inefficiencies and voltage drop losses, which degrade overall power circuit efficiency.
Innovation Solution
A circuit for driving a synchronous rectifier that includes a voltage level detecting unit, an on/off signal generating unit, a minimum time determining unit, and a blanking time determining unit to control the synchronous rectifier's operation, ensuring it remains off for a preset period after turning off and preventing immediate reactivation due to noise or resonance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a synchronous rectifier is used as the secondary rectifier, then power efficiency is improved, but the synchronous rectifier may malfunction due to resonance phenomenon when soft load is applied
Solution Approach 1:
The patent applies preliminary action by implementing a blanking time mechanism that proactively prevents the synchronous rectifier from being turned on during a predetermined period after it has been turned off. This preemptive timing control eliminates resonance-induced malfunctions before they can occur, while still allowing the synchronous rectifier to operate efficiently during valid conduction periods. The controller includes a blanking time generator that generates a blanking signal to inhibit turn-on signals during the blanking period, thus resolving the contradiction between maintaining high efficiency and preventing resonance malfunction.
2Reliability
If the synchronous rectifier is controlled to remain off for a preset period after shutdown, then resonance-induced malfunction is prevented, but response time to valid turn-on signals is increased
Solution Approach 1:
The blanking time mechanism is applied as a predetermined time period immediately following the turn-off event. By establishing this fixed duration in advance, the system knows exactly when the blanking period ends and can immediately respond to valid turn-on signals without unnecessary delay. The preliminary nature of this timing control ensures that the response time loss is minimized and predictable, while still providing sufficient protection against resonance phenomena.
Solution Approach 2:
The patent implements periodic action through the cyclic nature of the blanking time intervals that repeat with each switching cycle. The blanking signal is generated periodically after each turn-off event, creating a rhythmic pattern of protection intervals. This periodic application of the blanking mechanism ensures consistent prevention of resonance malfunctions while maintaining regular, predictable response times across all operating cycles.
Data Source
AI summary
A circuit for driving a synchronous rectifier may include a voltage level detecting unit detecting a voltage level of the synchronous rectifier; an on/off signal generating unit generating an on signal controlling the synchronous rectifier to be turned on when the voltage level detected by the voltage level detecting unit is decreased to a voltage level equal to or less than a preset reference voltage level, and generating an off signal controlling the synchronous rectifier to be turned off when the voltage level detected by the voltage level detecting unit is increased to a voltage level exceeding the reference voltage level; a minimum time determining unit controlling the synchronous rectifier to be turned on during a preset first period; and a blanking time determining unit controlling the synchronous rectifier so as not to be turned on during a preset second period after the synchronous rectifier has been turned off.