Low Current Control for Power Connection Switches

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Solution Overview

Problem

Existing power supply control circuits, particularly e-fuse circuits, face inefficiencies due to the high current requirements of charge pumps needed to turn on power transistors, which result in significant power consumption and large integrated circuit area, especially when handling large currents and capacitive loads.

Innovation Solution

A controller circuit that includes a first current source and a second current source, where the second current source provides additional current when the voltage is below a threshold, allowing for efficient charging of parasitic capacitors and reducing the need for large charge pumps by sizing the current sources to handle specific capacitances, thereby controlling the rise rate of the gate voltage and minimizing power consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If a charge pump is used to provide gate voltage higher than input voltage, then the power transistor can be turned on, but power consumption increases and integrated circuit area increases

Engineering Contradiction:

Improvepower transistor switching capabilityVSAvoidcharge pump power consumption

Core Design Contradiction:

PowerVSLoss of energy

Solution Approach 1:

The gate voltage charging process is segmented into two phases: initial charging phase using the second current source to quickly charge parasitic capacitors, and steady-state phase using the first current source to maintain the voltage. This segmentation allows each current source to be optimized for its specific function, reducing overall power consumption.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The second current source provides excessive current during the initial charging phase to quickly overcome the threshold voltage and turn on the power transistor. Once the transistor is on, the first current source takes over with a lower, sustained current level, avoiding the continuous high current consumption that would occur with a traditional charge pump.

Inventive Principle:

Principle #16Partial or excessive action

2Power

If a charge pump is used to provide gate voltage, then the power transistor can be turned on, but integrated circuit area increases

Engineering Contradiction:

Improvepower transistor switching capabilityVSAvoidintegrated circuit area

Core Design Contradiction:

PowerVSArea of stationary object

Solution Approach 1:

The invention extracts the charge pump function entirely from the circuit and replaces it with simple current sources. The second current source handles the initial charging of parasitic capacitors, and the first current source maintains the gate voltage, eliminating the need for complex charge pump circuitry and its associated large capacitors and switches.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention changes the approach from voltage multiplication (charge pump) to current-controlled voltage charging. By using current sources with specific sizing relationships (second current source larger than first), the gate voltage is controlled through current integration over time, achieving the same effect with simpler, smaller circuit elements.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If current limit control is applied, then overcurrent protection is provided, but the power-up slope control is insufficient

Engineering Contradiction:

Improveovercurrent protectionVSAvoidpower-up slope control

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The first current source is configured to control the power-up slope by limiting the charging current of the gate during the initial phase. This preliminary current limitation prevents inrush current spikes before the power transistor fully turns on, complementing the overcurrent protection function and providing smooth power-up characteristics.

Inventive Principle:

Principle #10Preliminary action

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 reduces power consumption and integrated circuit area by optimizing current sourcing, preventing inrush current spikes and ensuring a smooth power-up slope, thus enhancing the efficiency and reliability of power supply control.

Implementation Method 1

a first current source having an output terminal coupled to a control terminal of a switch

Methodology Applied

Scientific EffectCapacitance charging: Capacitance

Implementation Method 2

a second current source having an output terminal coupled to the control terminal of the switch, the second current source providing current when a voltage on the control terminal is below a threshold

Methodology Applied

Scientific EffectVoltage threshold detection:

Data Source

PatentUS10135432B2Methods and apparatus for low current control for a power connection

Publication Date: 2018.11.20 TEXAS INSTRUMENTS INC

AI summary

Described examples include a controller having a first current source. The first current source has an output terminal coupled to a control terminal of a switch. A second current source has an output terminal coupled to the control terminal of the switch. The second current source provides current to the control terminal when the voltage on the control terminal is below a threshold. In accordance with another example, the switch is a field effect transistor. In another example, the first current source is driven by a charge pump. Methods are disclosed.