Buck-Boost Converter Bootstrap Voltage Refresh Circuit
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Solution Overview
Problem
Buck-boost power converters face challenges in maintaining sufficient bootstrap voltages during light load or no-load conditions, leading to decreased driving capability of power switches due to insufficient charging of bootstrap capacitors.
Innovation Solution
A driving circuit and method that includes current control circuits to generate charging current signals for the bootstrap capacitors based on input or output voltage signals when the bootstrap voltages fall below a refresh threshold, ensuring continuous operation by refreshing the capacitors in buck, boost, or buck-boost modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the buck-boost power converter operates under light load or no-load condition, then power consumption is reduced, but the charges on the bootstrap capacitors become insufficient leading to decreased driving capability of power switches
Solution Approach 1:
The patent applies preliminary action by detecting the bootstrap voltage before it becomes insufficient and proactively refreshing the bootstrap capacitors through current control circuits. This prevents the voltage from dropping to levels that would compromise power switch driving capability, ensuring reliable operation even during light load or no-load conditions where power consumption is reduced.
2Reliability
If the bootstrap capacitors are continuously charged to maintain sufficient voltage, then the driving capability of power switches is improved, but power consumption increases
Solution Approach 1:
The patent implements periodic action by using current control circuits to refresh the bootstrap capacitors only when needed, based on detected voltage levels. Rather than continuous charging, the system periodically intervenes to restore bootstrap voltages to sufficient levels, then allows normal operation to continue until the next refresh is required. This reduces unnecessary power consumption while maintaining reliable power switch driving capability.
3Reliability
If the bootstrap voltage is refreshed frequently, then the driving capability of power switches is maintained, but the complexity of the control circuit increases
Solution Approach 1:
The patent applies feedback by implementing voltage detection circuits that continuously monitor the bootstrap capacitor voltages and provide feedback signals to current control circuits. When the detected voltage falls below a threshold, the feedback triggers a refresh operation. This automated feedback mechanism maintains reliable power switch driving capability without requiring complex external control, as the system self-regulates based on actual voltage conditions.
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 solution effectively maintains adequate bootstrap voltages, ensuring reliable switching of power switches across varying operational modes, thereby improving the efficiency and stability of buck-boost power converters.
Implementation Method 1
a first bootstrap capacitor CB1 coupled between the input port IN and the first switching node SW1 is configured to generate a first bootstrap voltage VBST1 referenced with the voltage at the first switching node SW1
Implementation Method 2
the first current control circuit is configured to generate a first charging current signal and a second charging current signal to respectively charge the first bootstrap capacitor and the second bootstrap capacitor
Data Source
AI summary
A driving circuit and method for buck-boost converter with bootstrap voltage refresh. The driving circuit includes a first bootstrap capacitor provided a first bootstrap voltage to drive the corresponding switch, and a second bootstrap capacitor provided a second bootstrap voltage to drive the corresponding switch. When converter operates in buck mode and the first or second bootstrap voltage is smaller than a threshold, the driving circuit generates current signals to respectively charge the first and second bootstrap capacitors based on an input voltage, and the first and second bootstrap voltages. When converter operates in boost mode and the first or second bootstrap voltage is smaller than the threshold, the driving circuit generates current signals to respectively charge the first and second bootstrap capacitors based on an output voltage, and the first and second bootstrap voltages.