Power Converter Sense Pin Control for Synchronous Rectifier
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Solution Overview
Problem
Integrated circuit controllers for power converters face challenges in reducing cost while maintaining essential functionality, particularly in minimizing pin count for control and feedback signals, which is crucial for low-cost device designs.
Innovation Solution
Incorporating additional circuitry that allows the use of a single sense pin for both control and feedback signals, including the use of a sense resistor and an opto-coupler to provide an additional control/drive signal without adding a new pin, enabling synchronous rectifier control functionality in a lower cost device with restricted pin count.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a separate synchronous rectifier controller device is used, then synchronous rectifier control functionality is achieved, but device cost and pin count increase
Solution Approach 1:
The patent combines the synchronous rectifier control functionality with the existing converter controller device, merging two separate control functions into a single integrated controller. This eliminates the need for a separate synchronous rectifier controller device and reduces the overall pin count requirement.
Solution Approach 2:
The patent makes the sense pin multi-functional by using it for both current sensing and synchronous rectifier control signal output. The pin serves dual purposes: sensing converter circuitry parameters and providing control signals to the synchronous rectifier switch, thereby reducing the need for additional dedicated pins.
2Device complexity
If a sense pin is used for multiple functions, then pin count is reduced, but signal interference and control precision may deteriorate
Solution Approach 1:
The patent employs periodic time-division multiplexing where the sense pin alternates between sensing mode and control signal output mode. During specific time intervals, the pin senses converter parameters; during other intervals, it outputs control signals to the synchronous rectifier. This periodic switching prevents signal interference while maintaining measurement precision.
Solution Approach 2:
The patent dynamically configures the sense pin's function based on the operational phase of the converter. The controller device switches the pin's role between sensing and control output depending on real-time converter state, allowing adaptive optimization of both measurement accuracy and control functionality without signal interference.
Data Source
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Figure 3
Figure 4A
AI summary
A power converter controller device is formed as a packaged integrated circuit. The device includes means for generating a first control signal to control on time of a regulation switching transistor. A first package pin for connects the first control signal to the regulation switching transistor in the power converter circuitry. A sense resistor is placed in a current path in the power converter circuitry, the current path being conducting when the regulation switching transistor is on and non-conducting otherwise. A second package pin is connected to the sense resistor and coupled to circuitry integrated within the controller device to sense a voltage across the sense resistor when the regulation switching transistor is on. The device also includes means for generating a second control signal and means for coupling the second control signal to the second package pin when the regulation switching transistor is off. Thus the device has a sensing capability when the switching transistor is on and a control capability when it is off. The control capability is particularly suited to control of a synchronous rectifier within the power converter.