Boost DC/DC Converter for SPAD Biasing

Solution Overview

Problem

Existing light sensors with single-photon avalanche diodes (SPADs) face challenges in efficiently generating and delivering the required bias potential to place diodes in Geiger mode, leading to inefficiencies and disadvantages in their operation.

Innovation Solution

A light sensor design incorporating a boost DC/DC converter with an inductive element, switches, and a control circuit outside the integrated circuit chip, which delivers a bias potential greater than 15 V to the SPAD pixels, allowing them to operate in Geiger mode, while minimizing bulk and maximizing conversion efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If the bias potential is generated and delivered using known solutions, then the SPADs can be biased above breakdown voltage, but the conversion efficiency is low and power consumption is high

Engineering Contradiction:

Improveconversion efficiencyVSAvoidpower consumption

Core Design Contradiction:

Loss of energyVSUse of energy by moving object

Solution Approach 1:

The inductive element and switch are extracted from the integrated circuit chip and placed outside the chip. This extraction allows the use of larger, more efficient inductive components that can achieve higher conversion efficiency while reducing power consumption, without being constrained by the limited space and manufacturing processes of integrated circuit fabrication.

Inventive Principle:

Principle #2Taking out (Extraction)

2Loss of energy

If the inductive element and switch are integrated inside the chip, then the device is compact, but the conversion efficiency decreases and power consumption increases

Engineering Contradiction:

Improveconversion efficiencyVSAvoiddevice bulk

Core Design Contradiction:

Loss of energyVSVolume of moving object

Solution Approach 1:

The inductive element and switch are extracted from the integrated circuit chip and placed outside the chip. This extraction allows the use of larger, more efficient inductive components that can achieve higher conversion efficiency while reducing power consumption, without being constrained by the limited space and manufacturing processes of integrated circuit fabrication.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

A connection structure (such as a wire bond or PCB trace) acts as an intermediary to connect the integrated circuit chip to the external inductive element and switch. This intermediary enables the separation of the high-frequency switching function (kept on-chip) from the energy storage function (moved off-chip), resolving the contradiction between compactness and efficiency.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Loss of energy

If all converter components are placed outside the chip, then conversion efficiency is maximized, but the device complexity increases

Engineering Contradiction:

Improveconversion efficiencyVSAvoidconverter structure

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The inductive element and switch are extracted from the integrated circuit chip and placed outside the chip. This extraction allows the use of larger, more efficient inductive components that can achieve higher conversion efficiency while reducing power consumption, without being constrained by the limited space and manufacturing processes of integrated circuit fabrication.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The integrated circuit chip is designed to provide multiple functions: it contains the control circuitry for the boost converter, the pixel array with SPADs, and the interface to the external converter components. This multi-functionality reduces the need for separate dedicated converter modules, thereby reducing overall device complexity while maintaining high conversion efficiency.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 solution effectively addresses the inefficiencies of known light sensors by providing a robust and efficient method to bias SPADs, enhancing the operation of time-of-flight sensors and reducing power consumption, thus improving the performance and autonomy of devices using these sensors.

Implementation Method 1

an inductive element coupling a node configured to receive a first power supply potential to an intermediate node

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

a first switch coupling the intermediate node to a reference potential; a second switch coupling the intermediate node to an output node of the converter

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Data Source

PatentUS20230221420A1Light sensor

Publication Date: 2023.07.13 STMICROELECTRONICS (ALPS) SAS

AI summary

A light sensor includes an integrated circuit chip and a boost DC/DC converter. The integrated circuit chip supports an array of pixels, each pixel including a SPAD. The boost DC/DC converter delivers to the SPADs a bias potential capable of placing the SPADs in Geiger mode. The boost DC/DC converter includes an inductive element, a first switch, a second switch, and a circuit for controlling on/off switching of the first switch. The inductive element and the first and second switches are arranged outside of the integrated circuit chip while the control circuit forms part of the integrated circuit chip.