Cascode Amplifier Turn-Off Using Feedback Bias to Cut Switching Loss
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Modern power supply designs experience significant power loss due to switching losses when transitioning between ON and OFF states, primarily caused by voltage changes while current is flowing, which current technologies have not adequately addressed.
Innovation Solution
An apparatus comprising a cascode amplifier with a common-gate transistor and a common-source transistor, coupled with a feedback circuit and a bias circuit, that senses the rising drain-voltage and adjusts the gate-voltage to maintain the common-gate transistor in an active state until a second gate-voltage is applied, allowing for faster switching to an OFF state, thereby reducing switching losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the common-source transistor is switched to OFF state, then the drain-voltage increases, but the switching loss increases due to voltage rising while current is flowing
Solution Approach 1:
The bias circuit produces a gate-voltage in advance that increases as the drain-voltage increases, preparing the common-gate transistor for faster switching to OFF state before the full voltage rise occurs, thereby reducing the time during which both voltage and current are present
Solution Approach 2:
The feedback circuit receives the drain-voltage and produces a feedback signal that is used by the bias circuit to adjust the gate-voltage dynamically, creating a closed-loop control system that optimizes the switching process and minimizes switching losses
2Reliability
If the gate-voltage is increased to maintain common-gate transistor in active state, then the transistor remains conductive longer, but the switching time increases
Solution Approach 1:
The gate-voltage is made dynamic rather than static, automatically adjusting its level based on the drain-voltage through the feedback circuit, allowing the transistor to remain stable during normal operation while enabling rapid switching when needed
Solution Approach 2:
The bias circuit changes the gate-voltage parameter dynamically in response to drain-voltage changes, optimizing the transistor's switching characteristics by adjusting the voltage level according to the operating conditions
Data Source
AI summary
An apparatus for turning off a cascode amplifier having a common-base transistor and a common-emitter transistor is disclosed that includes the cascode amplifier, a feedback circuit, and a bias circuit. The feedback circuit is configured to receive a collector-voltage from the collector of the common-emitter transistor when the common-emitter transistor is switched to a first OFF state and produce a first feedback signal. The collector-voltage is equal to a emitter voltage of the common-base transistor and the collector-voltage increases in response to switching the common-emitter transistor to the first OFF state. The bias circuit is configured to receive the first feedback signal and produce a bias-voltage. A first base-voltage is produced from the bias-voltage. The cascode amplifier is configured to receive the first base-voltage and a second base-voltage. The common-base transistor is configured to switch to a second OFF state in response to receiving the second base-voltage.