Gate Driver Capacitance Randomization for EMI Noise Dispersion
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Solution Overview
Problem
Existing switching control circuits face limitations in efficiently dispersing EMI noise, particularly at high frequencies, and are restricted by the number of buffers used, which limits the performance of high-speed switching devices and reduces the ability to reduce circuit scale.
Innovation Solution
A switching control circuit that includes a gate driver, a variable capacitance element, and a capacitance changing circuit with an oscillator, pseudorandom-number generating circuit, and integrator to randomly change the capacitance of the variable capacitance element, effectively altering the switching speed and gradient of the gate signal to disperse EMI noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If pulse width control is performed on EMI noise timing (PTL 1), then EMI noise level is reduced, but peak noise occurs in particular frequency component
Solution Approach 1:
The patent applies dynamics by making the gate signal waveform flexible and changeable through variable capacitance elements. The capacitance values are dynamically adjusted based on timing information about switching transitions, allowing the gate signal characteristics to adapt and change over time. This dynamic adjustment disperses EMI noise across multiple frequency components rather than concentrating peaks at specific frequencies.
Solution Approach 2:
The patent changes physical parameters by varying capacitance values in the gate driver circuit. Different capacitance values are selected based on timing information to modify the gate signal waveform characteristics. This parameter change approach directly controls the spectral distribution of EMI noise, transforming concentrated frequency peaks into dispersed noise across broader frequency ranges.
2Object-affected harmful factors
If buffer circuits are used to change switching speed (PTL 2), then EMI noise influence on peripheral equipment is reduced, but frequency dispersion of EMI noise is restricted
Solution Approach 1:
Instead of fixed buffer circuits with predetermined switching speed patterns, the patent employs variable capacitance elements that can be dynamically controlled. The capacitance changing circuit adjusts capacitance values based on timing information about switching transitions, enabling flexible modification of gate signal waveforms. This dynamic control provides superior frequency dispersion capability compared to fixed buffer configurations.
Solution Approach 2:
The gate driver circuit itself performs the function of waveform modification through the variable capacitance elements, eliminating the need for separate buffer circuits. The timing information generation circuit works in conjunction with the capacitance changing circuit to automatically adjust capacitance values based on detected switching transitions, making the system self-regulating and adaptable without external intervention.
3Power
If current mirror circuit with operational amplifier is used to change slew rate (PTL 3), then driving ability is changed, but upper limit on operating frequency restricts high-speed characteristic
Solution Approach 1:
The patent extracts the waveform modification function from complex operational amplifier-based current mirror circuits and implements it through simpler variable capacitance elements controlled by timing information. This extraction removes the operating frequency limitations inherent in operational amplifier circuits while retaining the ability to modify gate signal waveforms and control EMI noise characteristics.
Solution Approach 2:
The patent substitutes the analog continuous control mechanism of operational amplifiers with a digital/timing-based control mechanism. The capacitance changing circuit responds to timing information about switching transitions, replacing the continuous analog adjustment of operational amplifiers with discrete, timing-synchronized capacitance changes. This substitution enables higher operating frequencies suitable for compound semiconductor FETs.
4Area of stationary object
If circuit scale is reduced (PTL 3), then number of change patterns of slew rate is restricted, but rising speed and falling speed of gate signal are similarly restricted
Solution Approach 1:
The patent merges the waveform modification function into the gate driver circuit itself by incorporating variable capacitance elements directly at the gate terminal. This integration eliminates the need for separate external buffer circuits or complex slew rate control circuits, reducing overall circuit scale while maintaining multiple change patterns of gate signal characteristics through timing-controlled capacitance adjustment.
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 solution efficiently disperses EMI noise across unique frequency regions, reducing peak noise levels and enhancing the performance of high-speed switching devices by randomly and steplessly varying switching speeds.
Implementation Method 1
a variable capacitance element (3) connected to the gate of the switching element (1), and a capacitance changing circuit (110) connected to the variable capacitance element (3) to randomly change a capacitance of the variable capacitance element (3)
Data Source
AI summary
A switching control circuit that controls on/off of a switching element is provided to efficiently disperse EMI noise due to high-speed switching, the switching control circuit includes a gate driver, a variable capacitance element connected to a gate of the switching element, and a capacitance changing circuit that randomly changes a capacitance of the variable capacitance element.