Switchable Capacitor LDO for Standby Loop Stability
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Solution Overview
Problem
Conventional low dropout regulators (LDOs) face issues with loop stability in standby states, which affect their overall performance.
Innovation Solution
The proposed LDO design includes a control unit connected to a second capacitor, which controls its electrode plate to be connected or disconnected from the power transistor's terminal, ensuring the primary pole is separated from the secondary pole, thereby enhancing loop stability in standby states. This design incorporates a control unit with main and auxiliary switching transistors and current sources to manage capacitor connections and disconnections, limiting voltage fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the second capacitor is always connected to the power transistor in conventional LDO designs, then the LDO can maintain proper biasing and operation, but the loop stability deteriorates in standby states due to pole interaction
Solution Approach 1:
The patent applies the dynamics principle by making the connection between the second capacitor and the power transistor switchable rather than fixed. The control unit dynamically connects or disconnects the second capacitor from the power transistor based on the operational state (standby vs. active), thereby optimizing loop stability in standby states while maintaining proper biasing during active operation. This dynamic reconfiguration resolves the contradiction between maintaining continuous operation and achieving standby stability.
2Reliability
If a control unit with multiple switching transistors is added to manage capacitor connections, then loop stability in standby states is improved, but the device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the control function into multiple switching transistors (first switching transistor and second switching transistor) that independently control different capacitor connections. This segmentation allows precise control over when the second capacitor is connected or disconnected from the power transistor, enabling stable standby operation while managing complexity through modular control elements.
Solution Approach 2:
The control unit acts as an intermediary between the power transistor and the second capacitor, mediating their connection based on operational requirements. The switching transistors serve as intermediary elements that enable or disable the connection path, allowing the system to achieve stable standby performance without requiring direct permanent connection between the power transistor and the capacitor.
Data Source
AI summary
Provided are a low dropout regulator and an electronic device. The low dropout regulator comprises a control unit electrically connected to a second capacitor, the control unit being used for controlling the connection or disconnection between a first electrode plate of the second capacitor and a second end of a power tube. Therefore, when the low dropout regulator is in a standby state, the control unit controls the disconnection between the first electrode plate of the second capacitor and the second end of the power tube, such that the second end of the power tube has a relatively small connection capacitance, so as to ensure the separation of a dominant pole point at a control end of the power tube from a secondary pole point at the second end of the power tube, and thus, the low dropout regulator has a high loop stability when same is in the standby state, thereby improving the performance of the low dropout regulator.