DC-DC Converter Dead Time Control via Voltage Transition Measurement
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Solution Overview
Problem
In DC-DC converters, setting an appropriate dead time is crucial to minimize switching loss and maximize efficiency, as improper timing can lead to increased heat generation, noise, and potential damage to switching elements, while changes in resonance current and load conditions continuously alter the voltage transition time of the switching node.
Innovation Solution
A DC-DC converter system that includes a control circuit to measure the voltage transition time of the switching node and adjust the dead time accordingly, ensuring that the high-side and low-side switching elements are turned on at optimal times, even with changes in operation conditions, thereby performing soft switching and maintaining high efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the switching frequency is increased to make the device smaller, then the device size is reduced, but the switching loss increases and heat generation increases
Solution Approach 1:
The patent applies dynamics by making the dead time variable rather than fixed. The control circuit dynamically adjusts the dead time based on the voltage transition time of the switching node, which changes with resonance current magnitude. This allows the system to adapt to varying operating conditions and maintain optimal switching performance across different frequencies and loads.
Solution Approach 2:
The patent changes the parameter of dead time duration based on operating conditions. By measuring the voltage transition time and adjusting the dead time accordingly, the system optimizes the switching characteristics. This parameter adjustment enables soft switching operation even when switching frequency changes, thereby reducing switching loss while maintaining high-frequency operation for compact size.
2Loss of energy
If the dead time is extended to ensure soft switching, then switching loss is reduced, but the switching element turn-on timing is delayed and efficiency decreases
Solution Approach 1:
The dead time is made dynamic rather than fixed. The control circuit continuously measures the voltage transition time of the switching node and adjusts the dead time duration accordingly. This ensures the dead time is precisely matched to the actual voltage transition requirements, avoiding both excessive delay and insufficient transition time.
Solution Approach 2:
The patent implements feedback by measuring the voltage transition time of the switching node and using this information to adjust the dead time. The control circuit monitors the actual voltage transition and modifies the dead time setting to optimize switching performance, thereby minimizing both switching loss and unnecessary delay.
3Speed
If the dead time is shortened to improve timing response, then switching speed increases, but soft switching cannot be maintained and switching loss increases
Solution Approach 1:
The dead time is dynamically adjusted based on the measured voltage transition time. When voltage transition is fast, the dead time is shortened to improve switching speed. When voltage transition is slow, the dead time is extended to maintain soft switching. This dynamic adjustment optimizes both switching speed and switching loss under different operating conditions.
Solution Approach 2:
The patent changes the dead time parameter according to the voltage transition characteristics. By measuring the actual voltage transition time and adjusting the dead time accordingly, the system maintains optimal switching performance across varying resonance current magnitudes and operating conditions, balancing speed and efficiency.
4Speed
If the switching element is turned on early to improve timing, then switching speed increases, but through current flows and large switching loss occurs
Solution Approach 1:
The control circuit uses feedback from the voltage transition time measurement to determine the optimal turn-on timing. By measuring how long the voltage transition takes and adjusting the dead time accordingly, the system ensures the switching element is turned on at the precise moment voltage transition completes, avoiding premature turn-on that would cause through current and switching loss.
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
The system effectively reduces switching loss and increases conversion efficiency by dynamically adjusting dead times based on real-time voltage transition times, ensuring stable operation across varying conditions.
Implementation Method 1
a resonance state of a resonant circuit including a capacitor connected in series to leakage inductance on a primary side of an isolated-type transformer is controlled by modulating the switching frequency
Implementation Method 2
a resonance state of a resonant circuit including a capacitor connected in series to leakage inductance on a primary side of an isolated-type transformer
Data Source
AI summary
A DC-DC converter includes a first switch connected between an input node and a switching node, a second switch connected between a reference node and the switching node, a capacitor having a first terminal connected to one of the input node and the reference node, a transformer including a primary coil connected between the switching node and a second terminal of the capacitor, and a secondary coil, a rectification smoothing circuit that rectifies and smooths a voltage of the secondary coil, and a drive circuit. The drive circuit alternately turns on the first and second switches, such that a dead time during which both the first and second switches are turned off has a length corresponding to a time period during which a voltage of the switching node is transitioning from a low state to a high state or the high state to the low state.