Cascoded Power Switch Timing for DC-DC Cross-Conduction Protection

The power switch is divided into multiple cascoded transistors (typically three NMOS transistors in series) instead of using a single transistor. This segmentation distributes the voltage stress across multiple devices, protecting each transistor from damaging voltages while maintaining the overall switch functionality. The intermediate nodes between cascoded transistors are monitored to control switching timing.

Voltage monitor circuits are introduced as intermediary components that detect the voltage at intermediate nodes between cascoded transistors. These monitors act as mediators between the power switch and control logic, enabling precise control of switching timing to prevent cross conductance and manage inductive voltage drops without requiring complex external control circuits.

The voltage monitor circuits utilize the inherent intermediate nodes of the cascoded power switch structure itself to detect voltage conditions. Rather than requiring external sensors or additional complex monitoring infrastructure, the system uses its own internal nodes (between cascoded transistors) to self-monitor and self-regulate switching timing, preventing cross conductance through intrinsic feedback.

The cascoded transistor structure serves multiple functions simultaneously: it provides voltage protection through series connection, creates intermediate monitoring nodes for timing control, and enables precise switching regulation. This multi-functionality reduces the need for separate dedicated components, offsetting the increased device count with functional consolidation.

The gate voltages of cascoded transistors are switched in a predetermined sequence with carefully controlled timing. The first transistor's gate is activated initially, followed by subsequent transistors after their respective intermediate nodes reach predetermined voltage levels. This preliminary staged activation ensures that each transistor turns on smoothly with controlled slew rate, limiting inductive voltage drops while maintaining overall switching speed through optimized timing.

Voltage monitor circuits continuously detect the voltage at intermediate nodes between cascoded transistors and provide feedback control signals. When an intermediate node reaches a predetermined voltage level, the feedback triggers the next transistor's gate activation. This closed-loop feedback ensures controlled gate voltage slew rates that limit inductive voltage drops while minimizing transition delays through real-time adaptation.