Drive Circuit for Switch Miller Period Control
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Solution Overview
Problem
Mass-produced switches exhibit variations in switching characteristics due to individual differences, leading to increased loss during state transitions from on to off and vice versa, which existing technologies have not effectively addressed.
Innovation Solution
A drive circuit is designed with a buffer unit that supplies a reference voltage to the control terminal of a switch, adjusting the transfer rate of electrical charge during the Miller period to be higher than during the threshold voltage passage, thereby shortening the Miller period and suppressing surge voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional drive circuit drives mass-produced switches with fixed charge transfer rate, then the circuit structure remains simple, but switching loss increases due to variations in switching characteristics
Solution Approach 1:
The drive circuit dynamically adjusts the charge transfer rate during different periods of the switching process. During the Miller period, a first charge transfer rate is applied, while during the threshold voltage passage, a second charge transfer rate is applied. This dynamic adjustment optimizes switching performance and reduces switching loss while accounting for individual switch variations.
Solution Approach 2:
The drive circuit divides the switching process into distinct periodic phases: the Miller period and the threshold voltage passage period. Each phase receives a tailored charge transfer rate optimized for its specific requirements, enabling efficient switching while reducing overall switching loss.
2Loss of time
If the charge transfer rate is increased during the Miller period, then the Miller period is shortened reducing switching loss, but surge voltage increases
Solution Approach 1:
The drive circuit applies different charge transfer rates during different periods: a first charge transfer rate during the Miller period to shorten it and reduce loss, and a second charge transfer rate during the threshold voltage passage to control surge voltage. This periodic differentiation resolves the contradiction between reducing Miller period and suppressing surge voltage.
Solution Approach 2:
The drive circuit changes the charge transfer rate parameter based on the switching phase. By adjusting this parameter dynamically - higher during Miller period for speed, lower during threshold passage for voltage control - the circuit achieves both short Miller period and controlled surge voltage.
Data Source
AI summary
In a drive circuit, a reference voltage generator generates a reference voltage that monotonically increases in a direction to pass through the threshold voltage during a voltage at the control terminal being lower than the Miller voltage. A buffer unit supplies the reference voltage output from the reference voltage generator to the control terminal of the switch, and adjusts a first transfer rate of electrical charge to or from the control terminal of the switch during at least part of a Miller period to be higher than a second transfer rate of electrical charge to or from the control terminal of the switch during the voltage at the control terminal of the switch passing through the threshold voltage. The Miller period is a period during which the voltage at the control terminal of the switch is maintained at the Miller voltage.