Gate Slew Rate Control in Insulated DC/DC Switching Circuits
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Solution Overview
Problem
Existing switching devices and converters face challenges in balancing power conversion efficiency and reducing radiation noise due to the trade-off relationship between slew rates during the switching of transistors, particularly in insulated DC/DC and AC/DC converters.
Innovation Solution
The DC/DC converter incorporates an externally connected adjustment resistor to the primary-side control device with a built-in switching transistor, allowing for adjustable slew rates by controlling the charging and discharging currents to the gate of the transistor, thereby optimizing power conversion efficiency and radiation noise characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the slew rate during switching is increased to improve power conversion efficiency, then efficiency is improved, but radiation noise increases
Solution Approach 1:
The patent applies dynamics by making the slew rate adjustable rather than fixed. The control device can dynamically change the slew rate of the switching transistor based on operating conditions, allowing optimization of efficiency when high power conversion is needed and reduction of noise when low emission is prioritized. This is achieved through controllable charging and discharging paths of the gate capacitor with different resistance values.
Solution Approach 2:
The patent changes the electrical parameter (slew rate) of the switching transistor by controlling the gate voltage transition speed. By adjusting the resistance values in the charging and discharging paths of the gate capacitor, the slew rate can be modified to achieve different balances between efficiency and noise, directly addressing the technical contradiction through parameter optimization.
2Device complexity
If a fixed slew rate is used in the switching transistor, then the device structure is simple, but both efficiency and noise performance cannot be optimized simultaneously
Solution Approach 1:
The control device achieves multi-functionality by incorporating both charging and discharging paths with adjustable resistance values, allowing it to perform multiple functions: optimizing efficiency through high slew rate charging, reducing noise through low slew rate discharging, and adapting to different operating conditions. This universal control approach eliminates the need for separate control circuits for different scenarios.
3Loss of energy
If expensive or large capacitors are used to adjust slew rates, then efficiency and noise can be optimized, but cost and device size increase
Solution Approach 1:
Instead of changing the physical size or capacitance value of the capacitor, the patent changes the electrical parameter (resistance) of the charging and discharging paths. By using variable resistors or switches to control the effective resistance, the slew rate is adjusted without requiring larger or more expensive capacitors, thus avoiding increases in component size and cost while still achieving optimization of efficiency and noise.
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 enables flexible adjustment of slew rates to balance efficiency and noise reduction, improving overall performance in insulated converters by minimizing losses and radiation noise without requiring expensive or large capacitors.
Implementation Method 1
a switching transistor M1 provided between the first terminal and the second terminal... by turning the switching transistor on or off by controlling a gate voltage VG of the switching transistor
Implementation Method 2
which is configured to turn the switching transistor on by supplying a charging current to a gate of the switching transistor
Implementation Method 3
to turn the switching transistor off by discharging charges stored in the gate of the switching transistor
Implementation Method 4
the driver discharges the stored charges via an external resistor RADJ provided outside the switching device
Data Source
AI summary
A switching device includes a switching transistor provided between a first terminal connected to an inductive load and a second terminal, and turns the switching transistor on and off. A driver turns the switching transistor on by supplying a charging current to a gate of the switching transistor, and turns the switching transistor off by discharging charges stored in the gate of the switching transistor. The driver discharges the stored charges via an external resistor provided outside the switching device and between a resistor connection terminal and a ground.