Integrated Voltage Regulator and Current Limiter Switching
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Solution Overview
Problem
Current power supplies with integrated current limiters experience higher quiescent currents and losses with increasing load currents, and often require fast loop correction to manage output currents effectively.
Innovation Solution
A power supply that automatically switches between voltage regulation mode and over current protection mode using a voltage regulator and current limiter, with a comparator and switching circuit to dynamically apply control voltages to the pass transistor, eliminating the need for a copied current and reducing quiescent currents and losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a current limiter is configured to create a copy of the actual output current for comparison, then over current protection can be achieved, but quiescent currents and losses increase with increasing load currents
Solution Approach 1:
The patent creates a copy of the output current through transistor Q3 which mirrors the current flowing through the load. This copied current is then compared with a reference current to detect overcurrent conditions. The copying approach enables reliable overcurrent protection while minimizing additional power consumption compared to alternative sensing methods.
2Reliability
If a current limiter creates a copied current for comparison, then current limiting function is achieved, but the system requires fast loop correction to manage output currents effectively
Solution Approach 1:
The patent implements a feedback mechanism where the copied current from transistor Q3 is continuously compared with the reference current through operational amplifier A1. When the copied current exceeds the reference current, the feedback loop immediately adjusts the control signal to transistor Q2 to reduce the output current. This closed-loop feedback ensures fast correction of overcurrent conditions without requiring complex additional circuitry.
3Reliability
If voltage regulation and current limiting are implemented separately, then both functions can be achieved, but device complexity increases
Solution Approach 1:
The patent merges the voltage regulation and current limiting functions into a single integrated circuit architecture. The operational amplifier A1 serves dual purposes: it compares the feedback voltage from the output to regulate voltage, and simultaneously compares the copied current to limit current. The transistor Q3 current mirror shares its control voltage with the voltage regulation loop. This merging eliminates the need for separate control circuits, reducing overall device complexity while maintaining both protection functions.
Data Source
AI summary
Disclosed is a power supply that automatically switches between a voltage regulation mode and an over current protection mode, as needed. The power supply includes a voltage regulator that generates a first control voltage for applying to the control terminal of a pass transistor during a voltage regulation mode to maintain an output voltage at a desired voltage level. The power supply includes a current limiter that generates a second control voltage for applying to the control terminal of the pass transistor during an over current protection mode to prevent an output current from rising above a maximum output current limit. The power supply includes additional circuitry that detects when over current protection is required and automatically switches the control voltage applied to the control terminal from the first control voltage to the second control voltage or vice versa, as necessary. Also disclosed is an associated power supply method.