Closed Loop Load Transient Tester for Voltage Regulators
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Solution Overview
Problem
Existing load transient test devices for voltage regulators lack control over the rise and fall edges of load transients, initial load current, and amplitude of load current, and are not adaptable to different output voltages, limiting their effectiveness in evaluating voltage regulator performance.
Innovation Solution
A test device that uses a MOSFET or BJT transistor to modulate current with a control signal, coupled with a current sense resistor and operational amplifier to generate a feedback voltage, allowing for precise control of load current profiles, including amplitude, rise and fall edges, and steady-state current, and is adaptable to various load current ranges through interchangeable components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If an open loop test device with a fixed current limiting resistor is used, then the device structure is simple, but the amplitude of load current cannot be controlled and the device cannot be adapted to different output voltages
Solution Approach 1:
The patent replaces the fixed current limiting resistor with a transistor (Q1) whose resistance can be dynamically controlled through a control voltage (VC). This allows the load current amplitude to be adjusted by changing VC, enabling adaptation to different output voltages and load conditions without modifying the hardware structure.
Solution Approach 2:
The patent changes the resistance parameter of the current limiting element from a fixed value to a variable value controlled by voltage VC. This parameter change enables flexible control of load current amplitude and allows the test device to adapt to different output voltages by adjusting VC accordingly.
2Ease of operation
If an open loop test device is used, then the device is simple to operate, but control over rise and fall edges of load transients is not possible
Solution Approach 1:
The patent introduces a feedback loop where the voltage across the current sense resistor (Rsense) is fed back through an operational amplifier (u1) to generate control voltage VC. This feedback mechanism automatically adjusts the transistor gate voltage to control the rate of change of load current, enabling precise control over rise and fall edges while maintaining ease of operation through automatic control.
Solution Approach 2:
The patent introduces an operational amplifier (u1) as an intermediary between the current sensing element and the transistor gate. This intermediary processes the feedback signal and generates the appropriate control voltage to regulate the load current transient edges, adding control capability without significantly complicating the overall system operation.
3Device complexity
If an open loop test device is used, then the device has fewer components, but control over initial load current and steady state current offset is not possible
Solution Approach 1:
The feedback loop continuously monitors the load current through Rsense and adjusts VC to maintain the desired current profile. This enables control over initial load current by setting the initial state of the feedback loop and control over steady state current offset by adjusting the reference voltage or bias conditions in the feedback circuit.
Solution Approach 2:
The transistor-based current control circuit serves multiple functions: it controls load current amplitude, regulates rise and fall edges, and adjusts steady state current offset. This multi-functionality is achieved through the feedback mechanism that can respond to different operating conditions and control requirements with a single integrated circuit approach.
4Reliability
If a fixed current limiting resistor is used, then the device is reliable, but the current sink capability is limited at low output voltages
Solution Approach 1:
The patent replaces the fixed resistor with a dynamically controllable transistor whose resistance can be adjusted based on the output voltage level. At low output voltages, the transistor can be biased to provide low resistance for high current sink capability, while maintaining stable operation through feedback control, thus preserving reliability while enhancing power handling.
Solution Approach 2:
The resistance parameter of the current limiting element is changed from fixed to variable, allowing optimization of the resistance value based on operating conditions. At low output voltages, the circuit can maintain appropriate current limiting through feedback control while enabling higher current capability compared to a fixed resistor designed for higher voltage operation.
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
Enables high current sink capabilities even at low output voltages, with fast slew rates and controlled load transients, effectively testing voltage regulators under various load conditions, ensuring stable output voltages during transient events.
Implementation Method 1
a transistor configured to modulate the current through the load connector subject to a control signal. The transistor may be a metal oxide semiconductor field effect transistor (MOSFET), e.g. an n-type MOSFET. The control signal may comprise a gate voltage which is applied to a gate of the transistor. The gate voltage may be used to control a drain-source resistance of the transistor, thereby controlling the drain-source current through the transistor.
Implementation Method 2
an operational amplifier configured to generate the control signal based on the feedback voltage and based on a target voltage. The operational amplifier may be configured to generate the control signal such that an absolute difference between the feedback voltage and the target voltage is reduced (e.g. minimized).
Implementation Method 3
a current sense resistor arranged in series with the transistor and configured to provide a feedback voltage which is substantially proportional to the load current.
Data Source
AI summary
The present document relates to voltage regulators (101). In particular, the present document relates to the testing of voltage regulators subject to load transients. A test device (110) configured to generate a load current to be drawn at an output of a voltage regulator (101) is described. The test device (110) comprises a load connector (116) for coupling the test device (110) to the output of the voltage regulator (101); a transistor (113) configured to modulate the current through the load connector (116) subject to a control signal (123); wherein the current through the load connector (116) corresponds to the load current; a current sense resistor (112) arranged in series with the transistor (113) and configured to provide a feedback voltage (121) which is substantially proportional to the load current; and an operational amplifier (111) configured to generate the control signal (123) based on the feedback voltage (121) and based on a target voltage (122).