Depletion Transistor Power Switch Eliminates High Voltage Starting Resistors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Switching power supplies experience high power losses due to the use of high voltage starting resistors in the no-load state, which increases costs and inefficiency.
Innovation Solution
A power supply circuit utilizing a depletion transistor as the main power switch, where the power switch is turned on during start-up to charge a capacitor, and the switching control circuit manages the power switch and a series-connected switch to maintain the charge voltage at a predetermined level, eliminating the need for high voltage starting resistors and auxiliary windings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high voltage starting resistors are used to supply power for control unit during start-up, then the control unit can be powered up, but power losses increase significantly in no-load state
Solution Approach 1:
The patent extracts and removes the high voltage starting resistor from the circuit by using a depletion transistor instead. The depletion transistor is configured to automatically turn off after start-up, eliminating the continuous power loss associated with resistive starting circuits in no-load conditions.
Solution Approach 2:
The patent changes the electrical parameters of the power switch by using a depletion transistor with negative gate threshold voltage characteristics. This allows the transistor to conduct during start-up without requiring continuous gate drive voltage, and can be turned off by applying a negative voltage or reducing gate voltage, thereby eliminating continuous power dissipation.
2Reliability
If auxiliary windings are used to supply power for control unit after actuation, then continuous power supply is achieved, but device complexity and cost increase
Solution Approach 1:
The patent makes the main power switch (depletion transistor) serve multiple functions: it acts as the primary power switch for the power conversion circuit and simultaneously serves as the power supply switch for the control unit. This eliminates the need for separate auxiliary windings dedicated solely to control unit power supply.
Solution Approach 2:
The patent merges the function of the auxiliary power supply with the main power switch. The depletion transistor's drain current, which is essential for power conversion, is also utilized to charge the charge capacitor that powers the control unit, combining two separate power supply functions into one component.
3Reliability
If high voltage starting resistors are used, then start-up power is provided, but overall product cost increases
Solution Approach 1:
The patent removes the high voltage starting resistor component from the bill of materials by replacing it with a depletion transistor that can be integrated into the existing power switch configuration, reducing component count and manufacturing cost.
Solution Approach 2:
The depletion transistor is designed to be used temporarily during start-up and then turned off, serving as a disposable-like component for the start-up function without requiring the continuous presence of expensive high voltage resistors throughout operation.
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 power losses and overall product costs by eliminating the need for high voltage starting resistors and auxiliary components, while ensuring the control unit operates efficiently during start-up and normal operation.
Implementation Method 1
a power switch configured to receive a DC input voltage... when the switching power supply is in a start-up phase, the power switch is turned on, the DC input voltage charges the charge capacitor through the power switch
Data Source
AI summary
A power supply circuit for a switching power supply including a power switch configured to receive a DC input voltage, can include: a switching control circuit configured to receive a charge voltage signal of a charge capacitor, a reference voltage signal, and a PWM control signal, and to generate a switching control signal; a control unit having a supply voltage from the charge capacitor, where the charge capacitor includes a first terminal coupled to the switching control circuit, and a second terminal coupled to ground; and where when the switching power supply is in a start-up phase, the power switch is turned on, the first switch is turned off, and the DC input voltage charge the charges capacitor through the power switch, and the control unit begins operating when the charge voltage signal reaches a level of starting voltage of the control unit.