Switching Converter Valley Detection With a Multiplexed Sense Pin
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Solution Overview
Problem
High-frequency switching power supplies face increased complexity and cost due to the need for additional circuits and pins to detect the valley value of the drain-source voltage, which complicates the control of the main power switch and results in higher switching losses.
Innovation Solution
A control circuit for switching converters that directly detects the drain-source voltage at the switch node, differentiates it to generate a first voltage, and compares it against a threshold to turn on the main power switch at the valley value, reducing the need for additional pins and optimizing circuitry by using a multiplexed pin for voltage generation and valley detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If additional circuits and pins are used to detect the valley value of drain-source voltage, then the switching power supply can achieve zero-voltage turn-on, but the device complexity and cost increase
Solution Approach 1:
The patent makes the auxiliary winding serve multiple functions: it is used both for normal voltage detection and for valley point detection. By configuring the auxiliary winding to detect both the voltage across the main power switch during normal operation and the valley point voltage during resonant operation, the patent eliminates the need for separate detection circuits and pins, thereby reducing device complexity while maintaining zero-voltage turn-on capability
Solution Approach 2:
The patent enables the existing auxiliary winding to automatically perform dual detection functions without requiring additional external components or circuits. The control circuit processes signals from the auxiliary winding to determine both normal operating voltage and valley point conditions, allowing the system to self-manage multiple detection tasks using a single existing resource
2Measurement precision
If additional pins are added for voltage generation and valley detection, then the detection accuracy improves, but the number of pins required increases
Solution Approach 1:
The patent configures the auxiliary winding to provide multiple detection functions through a single pin connection. The same auxiliary winding that normally detects switch node voltage is also used to detect the valley point voltage across the main power switch, eliminating the need for separate pins for voltage generation and valley detection while maintaining accurate measurement capability
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 approach reduces switching losses by enabling zero-voltage turn-on of the main power switch, simplifies the circuit design, and minimizes the number of pins required, thereby lowering the overall complexity and cost of the switching converter.
Implementation Method 1
a voltage generation circuit connected to the drain of the main power switch to receive a drain-source voltage of the main power switch and to differentiate the drain-source voltage to generate a first voltage
Data Source
AI summary
A control circuit for a switching converter having a main power switch, the control circuit including: a voltage generation circuit configured to be connected with a common connection terminal of the main power switch and an inductor to receive a drain-source voltage of the main power switch, and to generate a first voltage according to the drain-source voltage; a valley detection circuit configured to generate a valley detection signal according to the first voltage when the drain-source voltage resonates to a valley; and where the control circuit is configured to turn on the main power switch according to the valley detection signal.