Power Converter Dead Time Control via Dynamic Compensation
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Solution Overview
Problem
In switching AC/DC power converters, sudden changes in the frequency of the control signal can cause the primary and secondary sides to be simultaneously turned on, leading to potential damage, and existing methods fail to prevent this simultaneous activation effectively.
Innovation Solution
A method for controlling the dead time of the secondary side by generating voltages based on previous and current turning-on times, using ramp voltages and target voltages to determine the turning-on times of the synchronization switch, ensuring the primary and secondary sides are not simultaneously activated, and compensating for load changes by turning on a compensation switch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the frequency of the control signal of the primary side power switch is suddenly changed, then the response speed and adaptability of the power converter is improved, but the risk of simultaneous turning on of primary and secondary sides increases, leading to potential damage
Solution Approach 1:
The patent applies preliminary action by calculating and storing the ideal second turning-on time of the synchronous rectifier switch before the actual frequency change occurs. When the primary side power switch frequency changes, the system uses the pre-calculated ideal turning-on time and applies a dead time compensation value to determine the actual turning-on time, preventing simultaneous turning on before it can occur. This proactive approach allows the system to adapt to frequency changes while maintaining safety.
Solution Approach 2:
The patent introduces a dead time compensation value as an intermediary parameter between the ideal turning-on time and the actual turning-on time. This compensation value acts as a buffer that adjusts the timing relationship between primary and secondary sides during frequency transitions. By adding this intermediary time offset, the system resolves the contradiction between rapid frequency adaptation and prevention of simultaneous switching, as the compensation value dynamically adjusts based on the frequency change magnitude.
2Device complexity
If a fixed dead time is applied to the secondary side, then the simplicity of control is maintained, but the effectiveness in preventing simultaneous turning on during frequency changes is insufficient
Solution Approach 1:
The patent transforms the static fixed dead time approach into a dynamic adaptive dead time compensation mechanism. The dead time compensation value is calculated based on the frequency change of the primary side power switch and the ideal turning-on time of the synchronous rectifier switch. This dynamic adjustment allows the system to maintain simple control architecture while significantly improving the reliability of preventing simultaneous turning on, as the compensation value automatically adapts to different operating conditions without requiring complex control circuits.
3Productivity
If the turning-on time of the secondary side is advanced to improve power transfer efficiency, then the conversion efficiency is improved, but the risk of simultaneous activation with the primary side increases
Solution Approach 1:
The patent changes the timing parameter of the secondary side synchronous rectifier switch by introducing a dead time compensation value that is calculated based on the frequency change of the primary side. Instead of using a fixed advance turning-on time that risks simultaneous activation, the system dynamically adjusts the turning-on time parameter by adding the compensation value to the ideal turning-on time. This parameter change allows the system to maintain high conversion efficiency while eliminating the harmful simultaneous activation risk, as the compensation value ensures proper timing separation.
Data Source
AI summary
A method for controlling a dead time of a secondary side of a power converter includes giving a previous first turning-on time and a current first turning-on time corresponding to a primary side of the power converter, generating a first voltage and a second voltage according to the previous first turning-on time and the current first turning-on time, respectively, generating a current first target voltage according to the first voltage, the second voltage, and an ideal voltage corresponding to a previous ideal second turning-on time of the secondary side, and determining a current second turning-on time of the secondary side according to the current first target voltage and a first ramp voltage corresponding to a current ideal second turning-on time of the secondary side. A difference between the current second turning-on time and the current ideal second turning-on time is a current dead time.