Half-Bridge Gate Control During Dead Time to Cut Switching Loss
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Solution Overview
Problem
Electrical circuits with half-bridges formed from transistors experience significant switching losses due to the switching of transistors, which contribute substantially to total power loss and generate waste heat, necessitating a method to reduce these losses.
Innovation Solution
The method involves using field effect transistors connected such that the control voltage of one transistor is set to an intermediate voltage between the forward and blocking voltage levels during the dead time state, improving the switching characteristics and reducing switching losses by allowing faster current transfer and increased steepness during switching processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If transistors are switched between blocking and conducting states using standard voltage levels, then the electrical circuit can be controlled effectively, but switching losses increase significantly
Solution Approach 1:
The control voltage is dynamically adjusted during dead time based on the switching state of the transistors. When the first transistor is conducting, the control voltage of the second transistor is raised from the standard negative blocking voltage to a higher intermediate voltage level during dead time, optimizing the switching characteristics and reducing switching losses without compromising switching speed
Solution Approach 2:
The patent changes the voltage parameter of the control signal during dead time. Specifically, the control voltage for the blocking transistor is adjusted to an intermediate level (higher than the standard negative blocking voltage but lower than the conducting voltage) depending on which transistor is currently conducting, thereby reducing switching losses while maintaining effective control
2Loss of energy
If standard blocking voltage is applied to transistors during dead time, then circuit control is simplified, but switching losses increase and waste heat generation increases
Solution Approach 1:
The control voltage parameter is changed during dead time to an intermediate level instead of using the standard negative blocking voltage. This voltage adjustment reduces the switching losses that generate waste heat, while the control circuit manages the complexity of implementing this dynamic voltage change
3Loss of energy
If control voltage is adjusted to intermediate levels during dead time, then switching losses are reduced, but control circuit complexity increases
Solution Approach 1:
The control circuit uses feedback from the switching state of the transistors to dynamically adjust the control voltage during dead time. The control unit receives information about which transistor is conducting and accordingly adjusts the control voltage of the other transistor to the appropriate intermediate level, managing the complexity through intelligent control logic
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
Method for operating an electrical circuit (1) comprising at least one half-bridge (2) formed from two transistors (3, 4), wherein the electrical circuit (1) switches between a first switching state in which the first transistor (3) of the half-bridge (2) is switched on by a first voltage value of a first control voltage and the second transistor (4) of the half-bridge (2) is switched off by a second voltage value of a second control voltage, and a second switching state in which the first transistor (3) is switched off by a second voltage value of the first control voltage and the second transistor (4) is switched on by a first voltage value of the second control voltage, wherein a dead-time state is assumed between the first switching state and the second switching state in which both transistors (3, 4) are switched off.wherein in the dead-time state the control voltage of at least one of the transistors (3, 4) is set to an intermediate voltage value which lies between the first voltage value and the second voltage value of the control voltage of the transistor (3, 4).