Voltage Regulator Soft Start Parallel Transistors
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Solution Overview
Problem
Conventional low dropout (LDO) voltage regulators face challenges in preventing damage to power sources due to inrush currents when starting operation, as they consume additional current and lack effective mechanisms to restrict excessive current flow.
Innovation Solution
A voltage regulator design featuring a first power transistor and a second power transistor connected in parallel, with a control unit that sequentially turns on the transistors to manage inrush currents, ensuring the first transistor's aspect ratio limits initial current and the second transistor's higher aspect ratio allows for sufficient current supply after a predetermined period, preventing power source damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional LDO voltage regulator is used, then voltage regulation is achieved, but inrush current damages the power source
Solution Approach 1:
The power delivery function is segmented into two phases: initial power delivery through the first power transistor with limited current capacity, and subsequent full power delivery through the second power transistor. This segmentation allows the system to protect against inrush current while still meeting the full power requirements of the load.
Solution Approach 2:
The first power transistor is activated in advance with a limited aspect ratio to pre-charge output capacitors and prepare the system for full power operation. This preliminary action limits the inrush current to a safe level while still initiating the power delivery process.
2Object-affected harmful factors
If the first power transistor has a small aspect ratio to limit inrush current, then power source protection is achieved, but initial power delivery is insufficient
Solution Approach 1:
The power delivery function is segmented into two phases: initial power delivery through the first power transistor with limited current capacity, and subsequent full power delivery through the second power transistor. This segmentation allows the system to protect against inrush current while still meeting the full power requirements of the load.
Solution Approach 2:
The system merges the functions of two power transistors with different current capacities into a single power delivery path. The first transistor handles initial low-power operation, and the second transistor provides full power capability, together satisfying both protection and power delivery requirements.
3Object-generated harmful factors
If additional current consumption is used for soft starting, then inrush current control is achieved, but system efficiency decreases
Solution Approach 1:
The voltage regulator uses its own power output to control the gating signals for the power transistors, rather than requiring an external control power source. The soft starting control is achieved through internal current mirrors and gating circuits that draw minimal power from the regulated output.
Data Source
AI summary
A voltage regulator apparatus includes a first power transistor and a second power transistor connected in parallel to each other between a first power source and a second power source, and a control unit for turning on the first power transistor and the second power transistor. An aspect ratio of the first power transistor is smaller than an aspect ratio of the second power transistor. The control unit turns on the second power transistor in a predetermined period of time after the first power transistor is turned on.