GaN Start-Up Circuit for Low-Standby SMPS Power Supply
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing switched-mode power supply (SMPS) systems face challenges in managing power loss and start-up behavior, particularly in low-power portable devices, where switching losses and standby power consumption are concerns due to the reliance on AC line input for initial power supply.
Innovation Solution
A GaN-based start-up circuit using a normally-on GaN transistor with a load path coupled to a capacitor, where the capacitor is charged by the transistor during startup, providing initial power to the control and switching circuits before the SMPS is operational, and allowing for efficient start-up with minimal standby current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a high-ohmic resistor coupled to AC line input is used to charge an input capacitor for control circuit power supply during start-up, then the control circuit can be powered during start-up, but power continues to be drawn from AC line input when the SMPS is not operating or in standby mode, increasing standby power consumption
Solution Approach 1:
The patent changes the electrical parameters of the start-up circuit by using a normally-on GaN transistor instead of a high-ohmic resistor. The transistor's on-resistance is dynamically controlled through gate voltage application, allowing the circuit to transition from a high-consumption state during start-up to a near-zero consumption state during standby, thereby resolving the contradiction between start-up reliability and standby power consumption
Solution Approach 2:
The normally-on GaN transistor is configured to automatically turn off after charging the input capacitor during start-up, without requiring external control signals. The transistor's inherent characteristics and the circuit's feedback mechanism enable it to self-regulate and stop power draw once the capacitor is charged, eliminating continuous AC line dependency during standby mode
2Loss of energy
If traditional silicon-based transistors are used for switching, then the circuit is easier to manufacture with established processes, but switching losses are high due to higher parasitic capacitance and on-resistance
Solution Approach 1:
The patent changes the material parameters by substituting silicon-based transistors with GaN transistors. GaN material inherently provides lower parasitic capacitance and on-resistance, directly reducing switching losses. The use of normally-on GaN transistors further optimizes these parameters by enabling lower on-resistance operation while maintaining manufacturability through compatible fabrication processes
Solution Approach 2:
The patent employs GaN (gallium nitride) wide-bandgap material as a composite semiconductor solution that combines the benefits of low loss with manufacturability. The GaN-based normally-on transistor integrates material science advancement with practical manufacturing considerations, achieving reduced switching losses without completely abandoning established fabrication methodologies
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
Enables efficient start-up of SMPS systems with reduced standby power consumption and cost-effective implementation by using the same semiconductor process for both normally-on and normally-off GaN transistors, addressing switching losses and standby power issues.
Implementation Method 1
a capacitor (C) coupled to a power supply node (VDD) for providing a start-up voltage
Data Source
Figure 1A~1D
Figure 2~3
Figure 4A
AI summary
In accordance with an embodiment, a circuit includes a first gallium nitride (GaN) transistor comprising a drain coupled to a drain node, a source coupled to a source node, and a gate coupled to a gate node; and a second GaN transistor comprising a drain coupled to the drain node, a source coupled to a first power source node configured to be coupled to a first capacitor.