Stepwise Soft-Start Voltage Regulator for Bypass Current Surges
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Solution Overview
Problem
Voltage regulators in voltage bypass mode experience instantaneous large currents due to rapidly rising output voltage, which existing technologies fail to mitigate effectively.
Innovation Solution
A voltage regulator design incorporating an amplifier, a voltage setting circuit, and a voltage selector that reduces the selection voltage stepwise in multiple time intervals during startup, adjusting the driving voltage and output voltage stepwise to reduce instantaneous current changes, thereby achieving a soft-start operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the output voltage rises rapidly in voltage bypass mode, then the voltage regulator can quickly reach the operating power supply level, but instantaneous large current occurs
Solution Approach 1:
The voltage rise process is segmented into multiple stages through the voltage selector circuit. The selection voltage is divided into multiple levels (first level, second level, third level) that are applied sequentially during different time intervals. This segmentation allows the output voltage to increase in steps rather than rapidly all at once, thereby preventing instantaneous large current while still achieving relatively fast voltage bypass operation.
Solution Approach 2:
The voltage selector circuit performs preliminary action by pre-establishing multiple voltage levels before the actual voltage bypass operation. The circuit prepares the first level, second level, and third level selection voltages in advance, which are then sequentially applied to control the power transistor's gate voltage. This preliminary preparation ensures that when voltage bypass mode is activated, the voltage rises in a controlled stepwise manner rather than instantaneously, avoiding current surges.
2Object-generated harmful factors
If a high-performance soft-start mechanism is added to prevent instantaneous large current, then current surges are avoided, but device complexity increases
Solution Approach 1:
The voltage selector circuit serves multiple functions: it normally selects different voltage levels during regular operation and simultaneously acts as a soft-start mechanism during voltage bypass mode. The same circuit structure that provides voltage selection functionality also generates the stepped voltage levels needed for soft-start operation. This multi-functionality eliminates the need for a separate dedicated soft-start circuit, thereby reducing overall device complexity while still effectively preventing instantaneous large current.
Data Source
AI summary
The disclosure provides a voltage regulator with a soft-start effect. The voltage regulator includes an amplifier, a first voltage setting circuit, a voltage selector and a power transistor. The amplifier has two input terminals to receive respectively a reference voltage and a feedback voltage. The amplifier has a current source to provide a current to an output terminal. In a voltage bypass mode, the first voltage setting circuit increases a driving voltage on the output terminal according to the current based on a selection voltage. In the voltage bypass mode, the voltage selector sequentially reduces the selection voltage respectively in multiple time intervals in a startup time interval. The power transistor receives the driving voltage, and generates an output voltage according to the driving voltage based on an operating power supply.