MOSFET Triggered Current Boosting for Voltage Regulators

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Solution Overview

Problem

Existing voltage regulators, such as low dropout (LDO) regulators, face challenges in increasing current without adverse impacts on circuit operation, cost, or battery life, particularly due to the use of Schottky diodes which are costly and have high leakage currents.

Innovation Solution

The implementation of a voltage regulator output stage that forward biases a power device using a MOSFET trigger, reducing threshold voltage and increasing output current capability while minimizing leakage, thereby avoiding the drawbacks of Schottky diodes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If Schottky diode is used to forward bias the power device, then the output current capability is increased, but the leakage current increases significantly and cost increases

Engineering Contradiction:

Improveoutput current capabilityVSAvoidleakage current

Core Design Contradiction:

PowerVSLoss of energy

Solution Approach 1:

The patent changes the biasing parameter by applying a controlled forward bias voltage (VBias) to the body of the power MOSFET through a bias circuit. This forward bias reduces the threshold voltage of the power device, enabling higher output current capability without requiring a Schottky diode, thereby avoiding the high leakage current problem associated with Schottky diodes.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent extracts and eliminates the Schottky diode from the circuit by replacing it with a bias circuit that directly controls the body voltage of the power MOSFET. This removal of the Schottky diode eliminates the source of high leakage current while maintaining the current boosting function through alternative means.

Inventive Principle:

Principle #2Taking out (Extraction)

2Power

If Schottky diode is used to forward bias the power device, then the output current capability is increased, but the circuit cost increases

Engineering Contradiction:

Improveoutput current capabilityVSAvoidcircuit cost

Core Design Contradiction:

PowerVSEase of manufacture

Solution Approach 1:

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The bias circuit performs multiple functions: it forward biases the body of the power MOSFET to reduce threshold voltage, controls the output current capability, and eliminates the need for an external Schottky diode. This multi-functionality reduces component count and overall circuit cost.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Power

If forward biasing is applied to increase current capability, then the output current increases, but the threshold voltage reduction may cause unwanted conduction

Engineering Contradiction:

Improveoutput current capabilityVSAvoidunwanted conduction

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The patent employs a feedback mechanism where the bias circuit monitors the operating conditions and adjusts the forward bias voltage (VBias) accordingly. This feedback control ensures that the threshold voltage is reduced only when needed for increasing output current capability, while preventing unwanted conduction by maintaining appropriate bias levels under different operating conditions.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The bias voltage (VBias) is made dynamic rather than fixed, allowing it to adjust based on the operating requirements of the power device. This dynamic control enables the circuit to optimize the threshold voltage reduction for current boosting while preventing unwanted conduction by adapting the bias level to actual operating conditions.

Inventive Principle:

Principle #15Dynamics

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

This approach enhances circuit performance by increasing current without increasing costs or reducing battery life, making it a commercially viable solution for portable electronic devices.

Implementation Method 1

forward biases the body to source junction of power device 102. This forward biasing can advantageously reduce the threshold voltage of power device 102, thereby effectively increasing its gate drive as well as its output current capability

Methodology Applied

Scientific EffectForward biasing:

Data Source

PatentUS7541796B2MOSFET triggered current boosting technique for power devices

Publication Date: 2009.06.02 MICREL INC

AI summary

A voltage regulator output stage can include a power device whose body to source junction is forward biased using a MOSFET trigger. The forward biasing can advantageously reduce the threshold voltage of the power device, thereby effectively increasing its gate drive as well as its output current capability. Controlling the forward biasing using the MOSFET trigger provides minimal leakage, thereby ensuring that the output stage is commercially viable as well as performance enhanced.