Linear Power Supply Reference Adjustment for Input Transients
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Solution Overview
Problem
Linear power supplies face challenges in providing stable input transient response characteristics, especially when supplied with low and varying input voltages, leading to potential output voltage fluctuations and load malfunctions across a wide load range.
Innovation Solution
A linear power supply design that includes an output transistor, a driver, a current detector, and a voltage adjuster to maintain a differential voltage between input and output voltages above a minimum offset voltage, ensuring the output transistor remains in a stable state and preventing overshoots by adjusting the reference or feedback voltage based on output current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the linear power supply uses a conventional fixed reference voltage configuration, then the circuit structure remains simple, but the input transient response characteristics deteriorate when supplied with low and varying input voltages
Solution Approach 1:
The reference voltage is changed from a fixed value to a dynamically adjustable value that varies with output current. The voltage adjuster modifies the reference voltage based on the magnitude of output current detected by the current detector, enabling the power supply to adapt to different operating conditions and maintain stable transient response characteristics across wide load ranges.
Solution Approach 2:
A feedback loop is established where the current detector monitors output current and provides this information to the voltage adjuster, which then adjusts the reference voltage accordingly. This feedback mechanism ensures that the differential voltage remains above the offset voltage threshold, preventing output transistor saturation and maintaining reliable transient response.
2Use of energy by moving object
If the linear power supply operates with low input voltages, then power consumption is reduced, but the input transient response characteristics worsen due to insufficient differential voltage margin
Solution Approach 1:
The reference voltage parameter is dynamically changed based on output current magnitude. When output current is high, the reference voltage is reduced to maintain adequate differential voltage margin even with low input voltages. This parameter adjustment allows the system to operate reliably at low input voltages while consuming less power.
3Reliability
If the linear power supply uses a fixed offset voltage, then the circuit design is simplified, but the differential voltage may fall below the offset voltage under varying load conditions, causing output voltage overshoots
Solution Approach 1:
The voltage adjuster proactively adjusts the reference voltage before the differential voltage can fall below the offset voltage threshold. By detecting output current in advance and preemptively modifying the reference voltage, the system prevents saturation conditions and output voltage overshoots before they occur.
Data Source
AI summary
A linear power source 1 comprises: an output transistor 10 that is connected between an input end of an input voltage VIN and an output end of an output voltage VOUT; a driver 30 for driving the output transistor 10 so that a feedback voltage VFB according to the output voltage VOUT matches a reference voltage VREF; a current detection unit 50 for detecting an output current IOUT flowing to the output transistor 10; and a voltage adjustment unit 40 for adjusting the reference voltage VREF or the feedback voltage VFB so that a differential voltage between a first voltage (for example, VIN itself) according to the input voltage VIN and a second voltage (for example, VOUT itself) according to the output voltage VOUT or the reference voltage VREF will not fall below an offset voltage Voffset according to the output current IOUT.