Dead Time Adjusting Circuit High Frequency Switching
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Solution Overview
Problem
Existing dead time adjusting circuits struggle to accurately set desired dead times at high switching frequencies, such as 20 MHz, due to the shortening of dead time, making it difficult to prevent simultaneous ON of output switches and resulting in through current.
Innovation Solution
A dead time adjusting circuit that monitors the switch voltage between output switches to detect first and second dead times, generating feedback-controlled signals to adjust the ON timing delays of the switches using a delay element with a stage number switching part and delay amount control, ensuring the dead times match a predetermined target value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the switching frequency is increased to improve productivity, then the switching speed increases, but the dead time becomes too short to be accurately controlled by conventional monitoring methods
Solution Approach 1:
The patent introduces a voltage signal as an intermediary to represent the dead time period. Instead of directly measuring the time interval between switch transitions, the circuit converts the dead time into a proportional voltage signal through capacitive integration of the switch node voltage, making the short time interval measurable and controllable even at high switching frequencies
Solution Approach 2:
The patent replaces direct time measurement with voltage-based representation. By integrating the voltage waveform during the dead time period, the circuit transforms a time measurement problem into a voltage measurement problem, which can be more accurately handled by conventional voltage comparators and control circuits at high frequencies
2Speed
If the dead time is shortened to accommodate high switching frequencies, then the switching speed improves, but the conventional monitoring method can no longer accurately detect the dead time
Solution Approach 1:
The patent uses voltage as an intermediary signal to represent the dead time duration. The switch node voltage is integrated over time during the dead period, creating a voltage signal whose magnitude is proportional to the dead time length, thereby converting an undetectably short time interval into a measurable voltage level
Solution Approach 2:
The patent changes the parameter being measured from time directly to voltage proportionally. By integrating the voltage waveform during the dead time interval, the circuit transforms the time parameter into a voltage parameter that can be accurately measured and compared even when the original time interval is too short for direct detection
Data Source
AI summary
In a dead time adjusting circuit, a switch voltage appearing at a connection node between a first output switch and a second output switch, which are connected in series between two different potentials, is monitored to detect a first dead time, which is from a time at which the second output switch is turned off to a time at which the first output switch is turned on, and a second dead time, which is from a time at which the first output switch is turned off to a time at which the second output switch is turned on, each of the first and second dead times being feedback-controlled to be identical to a predetermined target value.