Voltage Reference Circuit Fast Enable Disable LDO
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Solution Overview
Problem
Conventional voltage reference circuits, such as low drop-out (LDO) voltage regulators, face challenges in rapidly switching between enabled and disabled states due to large capacitive loads, leading to slow response times and inefficient power management, particularly in portable devices where immediate power down is required.
Innovation Solution
The integration of a low drop-out (LDO) regulator with a fast turn-on and fast turn-off circuit, utilizing a reference current source, current mirror, and control signals to quickly provide and discharge output current, along with a third control signal for modulating output current to prevent overshoot, enables rapid voltage stabilization and efficient power management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a large load capacitor is used to ensure loop stabilization, then voltage stability is improved, but the disabling response time deteriorates
Solution Approach 1:
The patent divides the current path into two separate paths: a first current path through the load capacitor for normal operation, and a second current path through a dedicated discharge transistor for rapid disabling. This segmentation allows the large capacitor to maintain voltage stability during normal operation while the separate discharge path enables fast disabling by providing a dedicated low-impedance path to ground that bypasses the capacitor's natural discharge time constant.
2Stability of the object's composition
If a large load capacitor is used to ensure loop stabilization, then voltage stability is improved, but power consumption during disable increases
Solution Approach 1:
The patent segments the current discharge function by introducing a dedicated discharge transistor in parallel with the load capacitor. This allows the capacitor to remain charged for stability during normal operation, while the discharge transistor provides a controlled path to rapidly dump the capacitor's energy to ground when disabling is required, minimizing unnecessary power consumption during the disable transition.
3Device complexity
If conventional LDO regulator is used, then circuit simplicity is maintained, but switching speed between enabled and disabled states deteriorates
Solution Approach 1:
The patent prepares the discharge path in advance by keeping the discharge transistor's gate connected to the operational amplifier's output, which can immediately drive the transistor into conduction when disabling is required. This preliminary arrangement of the discharge path, without requiring additional complex control logic, enables the circuit to switch rapidly from enabled to disabled state while maintaining relative circuit simplicity.
Data Source
AI summary
A circuit for providing an output voltage substantially equal to a reference voltage includes: a low drop-out (LDO) regulator coupled to the reference voltage for producing the output voltage at an output terminal; a reference current source having a first end and a second end for providing a predetermined reference current; a first transistor having a first terminal coupled to a first supply voltage, a second terminal, and a control terminal coupled to the second terminal of the first transistor; a first switch for selectively coupling the second terminal of the first transistor to the first end of the reference current source according to a first control signal; and a second transistor having a first terminal coupled to the first supply voltage, a control terminal coupled to the control terminal of the first transistor, and a second terminal coupled to the output terminal.