Adiabatic Charge Pump Shutdown via Inductor Current Discharge
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Solution Overview
Problem
Adiabatic step-down power converters face challenges in safely shutting down while maintaining a non-zero output load current, particularly regarding the path of inductor current discharge and oscillation at node Vx, which can exceed safe voltage ratings of transistors.
Innovation Solution
The implementation of a switch across the inductor, controlled by a controller circuit, to manage the discharge of inductor current efficiently, along with the use of active ESD elements and specific shutdown control sequences to prevent oscillation and ensure safe discharge, and the use of existing switches to act as an active discharge switch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the charge pump is shut down while output load current is non-zero, then the shutdown process is initiated, but the inductor current discharge path becomes problematic causing oscillation at node Vx that exceeds safe voltage ratings
Solution Approach 1:
The patent applies preliminary action by controlling the charge pump to enter a discharge mode before complete shutdown, where the charge pump actively discharges the inductor current through a controlled path. This preliminary discharge phase prevents dangerous voltage oscillations at node Vx during the subsequent shutdown by ensuring the inductor current is already reduced to a safe level before the charge pump fully disables.
2Reliability
If additional switches are added to provide a controlled discharge path for inductor current, then the shutdown safety is improved, but the component count and die area increase
Solution Approach 1:
The patent applies universality by designing the charge pump switches to perform multiple functions: during normal operation they pump charge to generate the output voltage, and during shutdown they provide the controlled discharge path for the inductor current. This multi-functionality eliminates the need for separate dedicated discharge switches, reducing component count while maintaining safe controlled discharge capability.
Solution Approach 2:
The charge pump circuit serves itself during shutdown by using its own internal switches and circuitry to provide the discharge path. The existing charge pump structure is repurposed to handle the inductor current discharge without requiring external or additional dedicated discharge components, making the system self-sufficient for shutdown protection.
3Ease of manufacture
If the inductor current is allowed to discharge freely during shutdown, then the shutdown is simpler, but oscillation at node Vx exceeds safe voltage ratings of transistors
Solution Approach 1:
The patent applies feedback by implementing control logic that monitors the shutdown state and automatically activates the discharge mode when shutdown is detected. The controller responds to the shutdown condition by reconfiguring the charge pump switches to provide the controlled discharge path, ensuring that the inductor current is managed safely without requiring complex external protection circuits.
Data Source
AI summary
A power converter including a multi-level topology is presented. The power converter includes a charge pump, a controller, an output load and an inductor. According to one aspect, the charge pump includes a multi-level topology. According to another aspect, the power converter includes a switch which is connected across the inductor. According to another aspect, the multi-level topology includes a plurality of series-connected switches that are controlled to close or open via the controller. The switches are arranged in a high-side or low-side switchable path of the multi-level topology. During operation in a first state, only one switch of the high-side is closed, during operation in a second state, at least one of the switches in the low-side is open, and during a transition from the first to the second state, all of the switches in the low-side are open.