Reverse Current Preventing Circuit for Synchronous Converters
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Solution Overview
Problem
Conventional synchronous switching voltage converters face inefficiencies due to variations in output voltage, inductor characteristics, and temperature changes, leading to potential current reversal issues.
Innovation Solution
A reverse current preventing circuit is introduced, comprising a current detecting circuit, voltage detecting circuit, and delay time adjusting circuit, which generates a corrected prevention signal based on switch node voltage to accurately control the low-side switch's turn-off timing, preventing current reversal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed threshold current is used to determine when to turn OFF the low-side switch, then the circuit operation is simple, but current reversal occurs due to variations in output voltage, inductor characteristics, and temperature
Solution Approach 1:
The patent applies dynamics by making the delay time adjustable rather than fixed. The delay time adjusting circuit dynamically modifies the delay period based on detected switch node voltage characteristics, allowing the system to adapt to varying operating conditions such as different output voltages, inductor characteristics, and temperature conditions, thereby preventing current reversal without requiring complex circuit reconfiguration
Solution Approach 2:
The patent changes the parameter of delay time based on detected voltage conditions. The delay time adjusting circuit receives the original prevention signal and generates a corrected prevention signal with an adjusted delay period. This parameter change allows the low-side switch turn-off timing to be optimized for different operating conditions, resolving the contradiction between simple operation and reliable current reversal prevention
2Device complexity
If the delay time is fixed, then the control circuit is simple, but accurate current control cannot be achieved under varying operating conditions
Solution Approach 1:
The patent implements feedback by having the delay time adjusting circuit detect the switch node voltage and use this information to adjust the delay time. The voltage detecting circuit continuously monitors the switch node voltage, and this feedback information is used to dynamically modify the delay period, ensuring accurate current control adapts to varying operating conditions while maintaining relatively simple circuit architecture
Solution Approach 2:
The patent applies preliminary action by detecting voltage conditions before the current reversal occurs and adjusting the delay time in advance. The delay time adjusting circuit proactively modifies the delay period based on detected voltage characteristics, preparing the correct turn-off timing before the switching event occurs, thereby ensuring accurate current control without requiring complex real-time adjustments
Data Source
AI summary
A synchronous switching voltage converter has a first switch, a second switch, and an inductor, which are all coupled together to a switch node. A reverse current preventing circuit has a current detecting circuit, a voltage detecting circuit, a delay time adjusting circuit, and a blocking circuit. When an inductor current reduces to reach a predetermined threshold current, the current detecting circuit generates an original preventing signal. The voltage detecting circuit detects a switch voltage at the switch node. In response to the original preventing signal, the delay time adjusting circuit generates a corrected preventing signal after an adjustable delay time with respect to the original preventing signal. The adjustable delay time is adjusted on a basis of the switch voltage. In response to the corrected preventing signal, the blocking circuit turns OFF the second switch.