Helper Transistor Regulator Architecture for Fast Load Transients
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Solution Overview
Problem
Voltage regulators face instability and require large load capacitors to manage fast changes in load conditions, which occupy valuable space in electronic devices and can be costly.
Innovation Solution
An auxiliary-current circuit with a helper transistor is introduced to provide additional charge current during output voltage drops, reducing the need for a large load capacitor by maintaining stability with a smaller capacitor and minimizing space usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a large load capacitor is used to manage fast changes in load conditions, then voltage regulation stability is improved, but board or chip space is increased
Solution Approach 1:
The patent divides the current supply function into two segments: the output transistor provides steady-state current, while the auxiliary-current circuit with helper transistor provides fast transient current during load disturbances. This segmentation allows the system to achieve fast response without requiring a large load capacitor, thus reducing board or chip space while maintaining voltage regulation stability.
Solution Approach 2:
The auxiliary-current circuit is pre-configured with the helper transistor in parallel with the output transistor, ready to immediately supply additional current when load disturbances occur. This preliminary arrangement enables the system to respond instantly to voltage drops without waiting for the error amplifier to detect and correct the disturbance, thereby maintaining stability with a smaller capacitor.
2Reliability
If a large load capacitor is used to accommodate current demand changes, then voltage drops during peak current demands are reduced, but space usage is increased
Solution Approach 1:
The patent merges the output transistor with the auxiliary-current circuit containing the helper transistor in a parallel configuration. This combination creates a unified current supply system where both transistors work together to meet peak current demands, effectively reducing voltage drops without requiring a large load capacitor, thus conserving space.
Solution Approach 2:
The auxiliary-current circuit dynamically activates the helper transistor during load disturbances when voltage drops occur. The helper transistor's gate or base is controlled to turn on only when needed, providing additional current during peak demands and then turning off when stable operation is restored. This dynamic behavior reduces voltage drops effectively while using minimal space compared to a statically large capacitor.
3Area of stationary object
If the load capacitor is reduced to save space, then board or chip space is decreased, but instability during load disturbances occurs
Solution Approach 1:
The auxiliary-current circuit acts as an intermediary between the output transistor and the load. When load disturbances cause voltage drops, the helper transistor in the auxiliary-current circuit mediates by providing additional current to support the output voltage, preventing instability that would otherwise occur with a reduced load capacitor.
Solution Approach 2:
The auxiliary-current circuit is pre-configured with the helper transistor ready to immediately supply additional current when load disturbances occur. This preliminary arrangement enables the system to respond instantly to voltage drops without waiting for the error amplifier to detect and correct the disturbance, thereby maintaining stability with a smaller capacitor.
Data Source
AI summary
Apparatus and methods for assisting a voltage regulator. In an example, a voltage regulator can include an error amplifier configured to compare a reference voltage with a representation of an output voltage of the voltage regulator, an output transistor coupled to a supply voltage and configured to receive an output of the error amplifier and to provide the output voltage, and an auxiliary-current circuit including a helper transistor having a terminal coupled to the output voltage, the helper transistor configured to turn on when the output voltage drops due to current demand from the load and to provide charge current to the load in addition to current provided by the output transistor.