Integrated Power Switch with Current-Sampling and High-Voltage Startup
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Solution Overview
Problem
Existing switching mode power supplies face challenges in achieving high power conversion efficiency and reducing production costs, particularly in integrating high-voltage startup functions and current-sampling capabilities effectively.
Innovation Solution
The integration of two enhancement-mode MOSFETs and a depletion-mode JFET on a monocrystal chip for a power supply with a flyback topology, where one MOSFET acts as a main power switch, another as a current-sampling switch, and the JFET as a high-voltage startup switch, allowing for improved efficiency and reduced manufacturing costs by forming the pulse-width-modulation controller on a lower-voltage process chip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a current-sense resistor is used to sense current through the power switch, then current sensing function is achieved, but power conversion efficiency deteriorates due to power consumption in the resistor
Solution Approach 1:
The patent replaces the resistive sensing mechanism with a MOSFET-based current sampling switch. Instead of using Ohm's law through a resistor, the invention uses the MOSFET's on-resistance in a controlled manner to sense current, eliminating the continuous power dissipation associated with traditional current-sense resistors while maintaining accurate current measurement capability.
Solution Approach 2:
The invention changes the operating parameters by using a MOSFET with very low on-resistance compared to a dedicated current-sense resistor. This parameter change allows the sampling switch to have negligible power consumption while still providing sufficient signal for current sensing, thereby improving overall power conversion efficiency.
2Adaptability or versatility
If high-voltage startup apparatus is integrated with the pulse-width-modulation controller, then high-voltage startup function is achieved, but manufacturing cost deteriorates due to high-voltage process requirements
Solution Approach 1:
The patent merges the high-voltage startup switch (JFET) with the PWM controller in a single integrated circuit. This integration allows the high-voltage startup function to be achieved without requiring separate high-voltage components, and the entire chip can be manufactured using lower-voltage processes, significantly reducing manufacturing costs while maintaining the high-voltage startup capability.
Solution Approach 2:
The integrated circuit achieves multi-functionality by incorporating both the high-voltage startup switch and the PWM controller in one device. This universal design allows a single chip to perform both high-voltage startup and standard PWM control functions, eliminating the need for separate high-voltage process manufacturing and reducing overall system cost.
Data Source
AI summary
A semiconductor apparatus includes first, second and third transistors integrated in a monocrystal chip. Both the first and second transistors are vertical devices, each having a source node, a gate node and a drain node. The source node of the first transistor electrically connects to a primary source pin, the source node of the second transistor to a sample pin, and the gate nodes of the first and the second transistors to a control-gate pin. The third transistor is a vertical JFET with a source node, a control node and a drain node. The source node of the third transistor electrically connects to a charge pin, and the control node of the third transistor to a charge-control pin. All of the drain nodes of the first, second and third transistors are electrically connected to a high-voltage pin.