Power Loss Protection Circuit With Forced Step-Down Switching
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Solution Overview
Problem
Existing power loss protection circuits experience delays in switching between step-up and step-down modes, leading to voltage drops that can render the load inoperable during power loss, due to delays in feedback circuit responses.
Innovation Solution
A power loss protection controller circuit with a high-side forced-on circuit and a voltage maintenance circuit to immediately switch to step-down mode, maintaining bootstrap voltage and controlling transistor states to stabilize output voltage, and incorporating features like charge pump circuits and overcurrent protection to manage transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a conventional feedback circuit is used to control mode switching, then the circuit operation is simple, but the switching delay causes output voltage drops during power loss
Solution Approach 1:
The patent implements preliminary action by detecting input voltage abnormalities in advance and proactively switching from step-up mode to step-down mode before complete power loss occurs. The detection circuit monitors VIN and triggers mode switching when voltage drops below a threshold, eliminating the delay inherent in conventional feedback circuits that only respond after output voltage degradation occurs.
Solution Approach 2:
The patent introduces a detection circuit as an intermediary between the input voltage source and the bidirectional converter control. This detection circuit acts as a mediator that monitors input voltage conditions and generates switch control signals to trigger mode changes, separating the detection function from the conventional feedback control loop to achieve faster response.
2Reliability
If the switching delay is reduced to maintain output voltage, then the load remains operable during power loss, but the feedback circuit response time becomes the limiting factor
Solution Approach 1:
The patent implements dual feedback mechanisms: (1) A conventional output voltage feedback loop that maintains stable operation during normal conditions, and (2) An input voltage detection feedback that proactively triggers mode switching when VIN drops below a threshold. This dual feedback approach ensures both load operability during power loss and eliminates the limitation of single-loop feedback response time.
Solution Approach 2:
The detection circuit performs preliminary detection of input voltage degradation and triggers mode switching before the output voltage sags occur. This preliminary action ensures the load remains operable by establishing the step-down mode in advance, eliminating the time loss associated with conventional feedback response delays.
3Speed
If the bidirectional converter switches modes quickly, then voltage drops are minimized, but the bootstrap circuit voltage becomes insufficient during rapid transitions
Solution Approach 1:
The patent applies preliminary action by maintaining the bootstrap circuit voltage at a sufficiently high level before mode switching occurs. The detection circuit triggers the transition while ensuring the bootstrap capacitor has adequate charge, preventing voltage insufficiency during rapid transitions and enabling fast mode switching without compromising the energy available for transistor switching.
Solution Approach 2:
The patent utilizes parameter changes by adjusting the bootstrap circuit operating parameters to maintain adequate voltage headroom during mode transitions. The system dynamically manages the bootstrap voltage level to ensure it remains sufficient for rapid switching while optimizing the energy efficiency of the transition process.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Stabilizes output voltage quickly during power loss, reducing voltage drops and ensuring load stability by minimizing delays in switching modes.
Implementation Method 1
the bidirectional converter 36 steps up the input voltage VIN and charges the backup capacitor 34
Implementation Method 2
the bidirectional converter 36 steps down the capacitor voltage VSTR of the backup capacitor 34 to the voltage level of the power supply voltage VBUS
Implementation Method 3
a voltage maintenance circuit provided separately from the bootstrap circuit and configured to maintain a voltage of a bootstrap line of the bidirectional converter at a voltage higher than a switching voltage by a predetermined voltage value
Implementation Method 4
the voltage maintenance circuit includes a charge pump circuit
Data Source
AI summary
A power loss protection controller circuit for receiving an input voltage and supplying an output voltage to a load includes a bidirectional converter and a converter controller, wherein the bidirectional converter includes a bootstrap circuit, a high-side transistor, a low-side transistor, a high-side driver, a low-side driver, and a voltage maintenance circuit provided separately from the bootstrap circuit, and wherein the converter controller includes a feedback circuit, a logic circuit, and a high-side forced-on circuit.