Cascode Amplifier Turn-Off Sequencing to Reduce Switching Loss
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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 effectively mitigated.
Innovation Solution
The apparatus employs a cascode amplifier with a feedback circuit and bias circuit to manage the switching of transistors, using feedback signals to adjust gate voltages and reduce switching time, thereby minimizing power loss by keeping the common-gate transistor in the ON state until a second gate voltage is applied to quickly switch it off.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the switching device transitions from ON to OFF state, then the power supply achieves voltage switching, but switching loss increases due to voltage rising while current flows
Solution Approach 1:
The patent applies preliminary action by turning off the common-emitter transistor before the common-base transistor during the switching sequence. This preparatory step allows the output voltage to rise before the main current path is interrupted, thereby reducing the overlap between voltage rise and current flow that causes switching loss. The feedback circuit detects the voltage rise and triggers the common-base transistor turn-off after the common-emitter transistor has already been turned off, ensuring minimal simultaneous voltage-current overlap.
2Productivity
If the switching device transitions faster between states, then productivity improves, but switching loss increases due to higher current during transition
Solution Approach 1:
The patent maintains continuity of useful action by using the feedback circuit to continuously monitor the output voltage and automatically control the switching sequence. The feedback signal ensures that the common-base transistor turns off only after the voltage has risen sufficiently, maintaining optimal switching conditions without manual intervention or fixed timing. This continuous feedback control enables fast switching while minimizing loss by adapting the switching moment to the actual voltage state.
3Loss of energy
If the common-base transistor remains in ON state longer, then switching loss reduces, but the device complexity increases due to additional control circuits
Solution Approach 1:
The patent implements feedback by using the output voltage signal itself to control the turn-off timing of the common-base transistor. The feedback circuit monitors the voltage at the collector of the common-emitter transistor and uses this information to trigger the common-base transistor turn-off at the optimal moment. This self-regulating feedback mechanism reduces switching loss without requiring complex external control circuits, as the system uses its own operating parameters to control the switching sequence.
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 an 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.