Bootstrap Refresh Control Circuit for Power Converter
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Power converters face challenges in timely refreshing of the bootstrap voltage, leading to operational issues such as failure to drive high side switches properly, especially under light load or no load conditions, resulting in large spikes in output voltage.
Innovation Solution
A bootstrap refresh control circuit that compares the bootstrap voltage with a threshold signal to generate a refresh signal, regulating the on and off switching of high side and low side switches to ensure timely charging of the bootstrap capacitor, thereby maintaining a stable bootstrap voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the power converter operates in light load or no load condition to improve power efficiency, then the on time of the low side switch becomes too short to charge the bootstrap capacitor, but the bootstrap voltage cannot be refreshed timely leading to operational failures
Solution Approach 1:
The patent implements a feedback mechanism where the control circuit continuously monitors the bootstrap voltage level and adjusts the switching duty cycle accordingly. When the bootstrap voltage drops below a threshold (indicating insufficient charging), the control circuit automatically increases the low side switch on-time to replenish the bootstrap capacitor, ensuring reliable operation while maintaining light load efficiency.
Solution Approach 2:
The patent employs dynamic adjustment of the switching duty cycle based on real-time bootstrap voltage conditions. The control circuit dynamically modifies the on-time of the low side switch during light load operation, extending it only when needed for bootstrap refresh, thus maintaining optimal power efficiency while ensuring timely voltage refresh when required.
2Reliability
If the on time of the low side switch is extended to charge the bootstrap capacitor, then the bootstrap voltage can be refreshed, but large spikes occur in the output voltage
Solution Approach 1:
The patent applies partial action by extending the low side switch on-time only for the minimum duration necessary to refresh the bootstrap voltage, rather than continuously. The control circuit monitors bootstrap voltage and activates extended on-time only when the voltage drops below the threshold, avoiding unnecessary extensions that would cause output voltage spikes while ensuring sufficient refresh occurs.
Solution Approach 2:
The patent implements periodic monitoring and adjustment of the bootstrap voltage with hysteresis control. The control circuit periodically checks the bootstrap voltage level and applies corrective action (extending on-time) only when the voltage falls below the lower threshold, then stops extension when the voltage recovers above the upper threshold, creating a stable periodic control pattern that prevents continuous spikes.
3Power
If a bootstrap circuit is used to generate voltage higher than input voltage, then the high side switch can be fully turned on, but the bootstrap capacitor cannot be charged unless the low side switch is on
Solution Approach 1:
The patent applies preliminary action by proactively monitoring the bootstrap voltage level before it drops to critical levels. The control circuit detects when the bootstrap voltage is insufficient and preemptively extends the low side switch on-time to charge the bootstrap capacitor, preventing operational failures before they occur rather than reacting after the voltage drops too low.
Solution Approach 2:
The patent implements self-service through an automatic feedback loop where the control circuit independently monitors bootstrap voltage and self-adjusts the switching duty cycle without external intervention. The system automatically extends or reduces the low side switch on-time based on real-time bootstrap voltage conditions, making the bootstrap refresh process autonomous and eliminating the need for manual adjustment.
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
Ensures the bootstrap voltage is refreshed in a timely manner, preventing operational failures and minimizing large spikes in output voltage, thus maintaining efficient power conversion.
Implementation Method 1
a bootstrap capacitor CB connected in series between a bootstrap supply terminal VB and the switching voltage output node SW, wherein a cathode of the diode DB is connected to the bootstrap supply terminal VB, an anode of the diode DB is connected to a first terminal of the bootstrap capacitor CB, and a second terminal of the bootstrap capacitor CB is connected to the node SW
Implementation Method 2
The bootstrap circuit 52 is illustrated to comprise a diode DB and a bootstrap capacitor CB connected in series between a bootstrap supply terminal VB and the switching voltage output node SW
Implementation Method 3
The first comparison module 104 is configured to compare the bootstrap voltage with a first threshold signal to provide a bootstrap refresh signal
Data Source
AI summary
A power converter having a bootstrap refresh control circuit and a method for controlling the power converter. The bootstrap refresh control circuit is configured to monitor a bootstrap voltage across a bootstrap capacitor and to provide an enhanced high side driving signal to a high side switch of the power converter. The bootstrap refresh control circuit is further configured to controlling the charging of the bootstrap capacitor through regulating the on and off switching of the high side switch and a low side switch based on the bootstrap voltage. The bootstrap refresh control circuit can refresh the bootstrap voltage in time to support driving the high side switch normally, without causing large spikes in an output voltage of the power converter and without influencing the power conversion efficiency of the power converter.