Bootstrap UVLO Detection for Fast High-Side Switch Shutdown
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing buck converters require additional circuitry and high-voltage devices to detect bootstrap under-voltage lockout (UVLO) events, leading to delays and inefficiencies.
Innovation Solution
A UVLO detection scheme that utilizes a BOOT UVLO circuit with a detection element to compare BOOT voltage with a switch node voltage, outputting an UVLO signal to control the high-side switch directly, eliminating the need for extra level shifters or high-voltage devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional level shifters or high-voltage devices are used to detect BOOT UVLO events, then detection capability is improved, but device complexity and response time are worsened
Solution Approach 1:
The patent combines the UVLO detection function with the existing gate driver circuit by using the same node voltages (BOOT and SW) that are already present in the circuit. The detection element compares these existing voltages directly without requiring separate detection circuits, level shifters, or additional high-voltage devices. This merging approach achieves reliable UVLO detection while minimizing additional circuitry.
Solution Approach 2:
The circuit uses its own internal voltages (BOOT and SW nodes) for self-diagnosis of UVLO conditions. The detection element is integrated into the existing gate driver structure, allowing the circuit to monitor its own operational state without external assistance or additional sensing components. This self-service mechanism improves reliability while avoiding the complexity of external detection systems.
2Reliability
If additional level shifters or high-voltage devices are used to detect BOOT UVLO events, then detection capability is improved, but response time is worsened
Solution Approach 1:
The detection element continuously monitors the BOOT and SW node voltages in real-time, maintaining readiness to detect UVLO conditions at any moment. By using the existing voltage nodes that are already present during normal operation, the system eliminates the need for additional signal conditioning or level shifting before detection can occur. This preliminary monitoring approach ensures immediate detection and response to UVLO events.
3Measurement precision
If additional circuitry is used for UVLO detection, then detection accuracy is improved, but chip area is worsened
Solution Approach 1:
The detection element serves multiple functions: it compares BOOT and SW voltages to detect UVLO conditions, and does so using the existing voltage nodes already present in the gate driver circuit. This multi-functional approach achieves accurate UVLO detection without dedicating separate circuitry solely for detection, thereby minimizing chip area while maintaining detection precision.
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
Faster response times and area savings by directly detecting UVLO events without additional circuitry, ensuring efficient operation of the buck converter.
Implementation Method 1
a BOOT UVLO detection element configured to compare a BOOT voltage with a switch node (SW) voltage to determine an occurrence of a BOOT UVLO event
Implementation Method 2
The bootstrap capacitor provides a floating voltage supply to the high-side MOSFET driver to switch the input voltage to the load
Implementation Method 3
This charging is usually accomplished through a diode connected between the input voltage and the bootstrap capacitor
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A buck converter including a high-side switch, a low-side switch and a bootstrap (BOOT), under-voltage lockout (UVLO) circuit. The BOOT UVLO circuit includes a BOOT UVLO detection element configured to compare a BOOT voltage with a switch node (SW) voltage to determine an occurrence of a BOOT UVLO event. The BOOT UVLO detection element is configured to output an UVLO signal (UVLO_Z), in case of the BOOT UVLO event. The BOOT UVLO circuit further includes a logic gate configured to receive the UVLO_Z and a high-side ON, (HSON) signal, the HSON signal is for controlling a switching of the high-side switch. The logic gate is configured to negate the HSON signal when receiving the UVLO_Z while the HSON signal is ON, to thereby immediately switch OFF the high-side switch when the HSON signal is ON.