Cascode Power Stage Segmentation for Light-Load Loss Reduction

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Solution Overview

Problem

Existing power converter circuits, particularly those using cascode power stages, face inefficiencies due to high power dissipation and space consumption, especially under varying load conditions, which can lead to reliability issues and increased parasitic capacitance.

Innovation Solution

Implementing a control circuit to dynamically shed or disable segments of cascode power stages during light load conditions, minimizing switching losses and parasitic capacitance by connecting gate terminals to source terminals, thereby reducing maximum voltage and maintaining switches within their safe operating area.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If cascode power stages are used to handle full load conditions, then power transfer capability is improved, but power dissipation and space consumption increase

Engineering Contradiction:

Improvepower transfer capabilityVSAvoidpower dissipation

Core Design Contradiction:

PowerVSLoss of energy

Solution Approach 1:

The power converter circuit is divided into multiple power stage segments (first power stage with switches Q1-Q2, second power stage with switches Q3-Q4). These segments can be independently controlled and activated based on load conditions, allowing the system to use only the necessary number of segments for the current power level, thereby reducing power dissipation when full power is not required

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The control circuit dynamically adjusts the operation of power stage segments based on real-time load conditions. During light load conditions, segments are disabled by connecting gate terminals to source terminals. During full load conditions, all segments are activated to provide full power transfer capability, optimizing the balance between power capability and power dissipation

Inventive Principle:

Principle #15Dynamics

2Power

If all power stage segments are activated, then power transfer capability is improved, but device area increases

Engineering Contradiction:

Improvepower transfer capabilityVSAvoiddevice area

Core Design Contradiction:

PowerVSArea of stationary object

Solution Approach 1:

The power converter is segmented into modular power stages that can be independently activated. This segmentation allows the physical layout to be optimized such that not all segments need to be simultaneously active, reducing the effective device area required for a given power capability

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Each power stage segment is designed with identical circuit topology and control mechanisms, allowing any segment to serve multiple functions depending on activation. This universality enables the same physical components to handle different power levels by simply activating or deactivating segments, rather than requiring dedicated components for each power level

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Power

If switches operate at high voltage, then power transfer capability is improved, but switching losses increase

Engineering Contradiction:

Improvepower transfer capabilityVSAvoidswitching losses

Core Design Contradiction:

PowerVSLoss of energy

Solution Approach 1:

The total voltage stress is distributed across multiple series-connected switches within each cascode power stage. By segmenting the power stages and selectively activating them, the voltage per switch is reduced during light load conditions, thereby reducing switching losses while maintaining adequate power transfer capability

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The control circuit changes the operating parameters of the switches based on load conditions. During light load conditions, switches are turned off by connecting gates to sources, effectively changing their state from high-voltage switching to zero-voltage hold, which minimizes switching losses

Inventive Principle:

Principle #35Parameter changes

4Loss of energy

If power stage segments are disabled during light load, then power dissipation is reduced, but power transfer capability decreases

Engineering Contradiction:

Improvepower dissipationVSAvoidpower transfer capability

Core Design Contradiction:

Loss of energyVSPower

Solution Approach 1:

The system dynamically adapts its power transfer capability to match the instantaneous load requirements. During light load conditions, segments are disabled to reduce power dissipation. During full load conditions, all segments are activated to provide full power transfer capability, achieving optimal efficiency across varying operating conditions

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS12407251B2Systems and methods for improving efficiency in a power converter using cascode power stages

Publication Date: 2025.09.02 EMPOWER SEMICONDUCTOR INC

AI summary

A circuit. In one aspect, the circuit includes a first power stage including a first switch having a first gate terminal, a first drain terminal and a first source terminal, and a second switch having a second gate terminal, a second drain terminal and a second source terminal, the first source terminal coupled to the second drain terminal, and a second power stage including a third switch having a third gate terminal, a third drain terminal and a third source terminal, and a fourth switch having a fourth gate terminal, a fourth drain terminal and a fourth source terminal, the third source terminal coupled to the fourth drain terminal, where the second power stage is coupled in parallel to the first power stage such that the first drain terminal is couped to the third drain terminal and the second source terminal is connected to the fourth source terminal.