Synchronous Rectification DC/DC Converter Bootstrap Charging Stop Circuit
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Solution Overview
Problem
In synchronous rectification DC/DC converters, power consumption is increased due to wasteful charging currents flowing into the bootstrap circuit during dead times when the high side and low side transistors are turned off simultaneously, as the voltage potential between them is lower than the source side of the synchronous rectification transistor, leading to inefficient operation.
Innovation Solution
Incorporating a charging stop circuit that includes a switch, such as a transistor, to cut off the charging current to the capacitor in the bootstrap circuit during dead times by disconnecting the high voltage potential from the capacitor, thereby preventing unnecessary charging and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bootstrap circuit is used to generate gate voltage for the high side MOS transistor, then the high side MOS transistor can be reliably turned on, but power consumption increases due to wasteful charging currents during dead times
Solution Approach 1:
The charging stop circuit detects the dead time period in advance and proactively stops the charging current to the bootstrap capacitor before the wasteful charging would occur. This preliminary action prevents the energy waste while ensuring the bootstrap capacitor is adequately charged during valid periods when the low side MOS transistor is on, thus maintaining reliable turn-on of the high side MOS transistor without the power consumption penalty during dead times.
2Reliability
If a dead time is provided to prevent through-current between high side and low side transistors, then switching safety is improved, but unnecessary charging current flows into the bootstrap circuit capacitor
Solution Approach 1:
The charging stop circuit uses feedback from the switching control signals to detect when both the high side and low side MOS transistors are off (dead time period). Based on this feedback, the charging stop circuit dynamically controls the charging current to the bootstrap capacitor, stopping it during dead times and enabling it during normal operation. This feedback mechanism maintains switching safety while eliminating the energy loss from unnecessary charging during dead times.
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
This solution effectively reduces power consumption by preventing charging currents from flowing into the capacitor during dead times, thereby decreasing overall power consumption in the DC/DC converter.
Implementation Method 1
a bootstrap circuit that includes a first capacitor charged with a current supplied from a high voltage potential terminal and is configured to raise a voltage potential of a control electrode of the first transistor
Data Source
AI summary
A synchronous rectification DC/DC converter includes a first transistor and a second transistor including respective main electrodes connected to a common connection point, the first transistor and the second transistor being NMOS transistors, a control circuit configured to control switching of the first transistor and the second transistor in a complementary manner, a bootstrap circuit that includes a first capacitor charged with a current supplied from a high voltage potential terminal and is configured to raise a voltage potential of a control electrode of the first transistor to turn on the first transistor, and a charging stop circuit configured to stop the first capacitor from being charged from the high voltage potential terminal in a time period in which the first transistor and the second transistor are turned off simultaneously.