Startup Regulator Using JFET and Diodes for AC-DC Converter Voltage Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
AC-DC converters used in USB Type-C chargers face challenges in stabilizing power supply voltage during startup, risking burnout of auxiliary circuitry due to variations in JFET pinch-off voltage, which requires precise manufacturing or trimming, increasing complexity and cost.
Innovation Solution
Incorporating a startup regulator with a junction gate field-effect transistor (JFET) coupled to an auxiliary pin, enhanced with a first FET in series and depletion region diodes to regulate voltage, ensuring safe operation by maintaining the voltage within a predetermined range, and using a flyback converter for post-startup power supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a JFET is used to regulate power during startup, then the auxiliary circuitry can be powered, but voltage variations due to JFET pinch-off voltage variations can cause burnout
Solution Approach 1:
The patent introduces an intermediary circuit between the JFET and the auxiliary pin that includes a depletion region diode and a capacitor. This intermediary circuit stabilizes the voltage by filtering out variations caused by JFET pinch-off voltage changes, preventing burnout while maintaining reliable power supply to the auxiliary circuitry during startup.
2Manufacturing precision
If precise manufacturing or trimming is used to stabilize JFET pinch-off voltage, then voltage stability improves, but device complexity and cost increase
Solution Approach 1:
The patent employs a self-regulating circuit using the JFET's inherent characteristics combined with a depletion region diode and capacitor that automatically compensates for pinch-off voltage variations. This self-service approach eliminates the need for precise manufacturing or external trimming processes, maintaining voltage stability while simplifying the manufacturing process and reducing device complexity.
3Reliability
If a startup regulator is implemented, then safe operation during startup is ensured, but power consumption increases
Solution Approach 1:
The patent implements a startup regulator that operates periodically only during the startup phase. The depletion region diode and capacitor circuit is activated during startup to stabilize voltage, then becomes inactive once the auxiliary circuitry is operational and transitions to flyback converter power supply, thereby ensuring safe operation during startup while minimizing overall power consumption.
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
The solution stabilizes the power supply voltage during startup, reducing the risk of burnout and enhancing safe operation, while also reducing total power consumption after startup by switching to the flyback voltage, thus improving the efficiency and reliability of the AC-DC converter.
Implementation Method 1
depletion region diodes to regulate voltage, ensuring safe operation by maintaining the voltage within a predetermined range
Data Source
AI summary
A system includes a transformer having an auxiliary coil to provide a flyback voltage to a primary side of an alternating current to direct current (AC-DC) converter. A primary side controller includes an auxiliary pin coupled to the transformer and to an external capacitor, the auxiliary pin to receive the flyback voltage after startup. a junction gate field-effect transistor (JFET) coupled to a supply voltage. A first FET is coupled in series between the JFET and the auxiliary pin, the JFET to charge the external capacitor from the supply voltage during startup. One or more depletion region diodes are coupled to a gate of the first FET, the one or more depletion region diodes to bias a voltage of the gate of the first FET to a specific voltage.