DC-DC Converter Auxiliary Apparatus for Transient Response
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Solution Overview
Problem
Conventional DC-DC converters experience excessive under-drop in output voltage due to delayed return of the driving loop after a sharp decrease in load current, leading to instability and unexpected voltage drops during the recovery process.
Innovation Solution
An auxiliary apparatus that controls the gate voltage of a pull-up transistor based on the voltage difference between the output voltage of an error amplifier and a reference voltage, using a current mirror, amplification unit, and control voltage clamping unit to improve transient response characteristics by preventing excessive under-drop and ensuring rapid loop recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the driving loop is stopped due to sharp decrease in load current, then power consumption is reduced, but output voltage experiences excessive under-drop when load current increases again
Solution Approach 1:
The auxiliary control apparatus performs preliminary action by proactively controlling the pull-up transistor gate voltage before the error amplifier output can naturally recover. When the driving loop is stopped and then restarted, the auxiliary circuit detects the voltage difference between the error amplifier output and reference voltage, and immediately adjusts the pull-up transistor gate voltage to clamp the loop control voltage, preventing excessive under-drop before it occurs.
Solution Approach 2:
The auxiliary control apparatus acts as an intermediary between the error amplifier and the pull-up transistor. It introduces a new control path that mediates the relationship between the error amplifier output voltage and the pull-up transistor gate voltage, using the voltage difference detection to control the gate voltage and thereby clamp the loop control voltage, ensuring stable output voltage during transient recovery.
2Productivity
If the error amplifier output voltage is allowed to converge to ground, then the driving loop can be fully stopped, but delay time occurs before the loop can operate normally again
Solution Approach 1:
The auxiliary control apparatus performs preliminary action by preparing the pull-up transistor gate voltage in advance based on the detected voltage difference. When the driving loop is stopped and the error amplifier output converges to ground, the auxiliary circuit has already positioned the gate voltage to enable immediate clamping action, eliminating the delay time required for the loop to recover and operate normally again.
Solution Approach 2:
The auxiliary control apparatus implements feedback by continuously detecting the voltage difference between the error amplifier output voltage and reference voltage, and using this feedback signal to adjust the pull-up transistor gate voltage. This feedback mechanism ensures that the loop control voltage is clamped to the reference voltage level, enabling rapid loop recovery without delay time.
3Device complexity
If conventional control method is used, then device complexity is low, but transient response characteristic between loop stop and return is poor
Solution Approach 1:
The auxiliary control apparatus applies segmentation by separating the control function into two independent parts: the original error amplifier and the auxiliary control circuit. The auxiliary circuit specifically handles the transient response control by detecting voltage difference and controlling the pull-up transistor gate voltage, while the error amplifier continues its normal voltage amplification function. This segmentation allows the transient response to be improved without significantly increasing overall device complexity.
Data Source
AI summary
Disclosed is an auxiliary apparatus for controlling a current mode of a DC-DC converter. The auxiliary apparatus includes a current mirror coupled to a source voltage and configured to duplicate and supply a reference current supplied from a constant current source, an amplification unit configured to perform negative feedback on a loop control voltage, generated from a DC-DC converter current mode driving unit, and a reference voltage, generated based on the reference current supplied from the current mirror, and a control voltage clamping unit configured to limit a reduction in the loop control voltage based on a gate control voltage output based on a result of the comparison and amplification of the amplification unit.