Switched Capacitor Voltage Converter Bootstrap Elimination

Solution Overview

Problem

Conventional switched capacitor voltage converters require multiple external bootstrap capacitors, which occupy additional substrate area, increase component costs, and necessitate more electrical terminals (pins), complicating the packaging and increasing dimensions and costs of semiconductor chips.

Innovation Solution

The proposed switched capacitor voltage converter eliminates the need for external bootstrap capacitors by using a configuration where driver capacitors are not directly connected to the switching devices, reducing the number of required terminals and capacitors, thereby minimizing substrate area usage and component costs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If external bootstrap capacitors are used in conventional switched capacitor voltage converters, then the switching devices can be properly driven, but the substrate area increases, component costs increase, and more electrical terminals are required

Engineering Contradiction:

Improveswitching device operationVSAvoidsubstrate area

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The patent merges the bootstrap capacitor function with the output capacitor by connecting the bootstrap capacitor to the output node, allowing the output capacitor to serve dual purposes: energy storage and bootstrap operation. This eliminates the need for separate external bootstrap capacitors and reduces the overall component count and substrate area.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The output capacitor is given multiple functions: it serves as both the energy storage element for the voltage conversion and the bootstrap capacitor for driving the switching devices. This multi-functionality approach eliminates dedicated bootstrap capacitors and reduces the number of external components required.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If external bootstrap capacitors are used in conventional switched capacitor voltage converters, then the switching devices can be properly driven, but the component costs and pin count increase

Engineering Contradiction:

Improveswitching device operationVSAvoidpin count

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges the bootstrap capacitor function with the output capacitor by connecting the bootstrap capacitor to the output node, allowing the output capacitor to serve dual purposes: energy storage and bootstrap operation. This eliminates the need for separate external bootstrap capacitors and reduces the overall component count and substrate area.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The output capacitor is given multiple functions: it serves as both the energy storage element for the voltage conversion and the bootstrap capacitor for driving the switching devices. This multi-functionality approach eliminates dedicated bootstrap capacitors and reduces the number of external components required.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Ease of operation

If driver capacitors are directly connected to switching devices with external bootstrap capacitors, then proper voltage levels are maintained, but substrate area and component count increase

Engineering Contradiction:

Improvevoltage level maintenanceVSAvoidsubstrate area

Core Design Contradiction:

Ease of operationVSArea of stationary object

Solution Approach 1:

The patent merges the bootstrap capacitor function with the output capacitor by connecting the bootstrap capacitor to the output node, allowing the output capacitor to serve dual purposes: energy storage and bootstrap operation. This eliminates the need for separate external bootstrap capacitors and reduces the overall component count and substrate area.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The output node and output capacitor provide the bootstrap function automatically as part of the normal voltage conversion operation. The system uses its own output energy to charge the bootstrap capacitor, eliminating the need for separate external bootstrap capacitors and making the system self-sufficient.

Inventive Principle:

Principle #25Self-service

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 configuration results in a more compact and cost-effective packaged IC device with reduced pin count and external capacitors, enhancing power efficiency and reducing the overall dimension and component costs of the voltage conversion circuit.

Implementation Method 1

A switched capacitor voltage converter may use a combination of one or more switching devices and one or more capacitors to convert an input voltage into a desired output voltage

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentEP3736963B1Switched capacitor voltage converter and method for operating a switched capacitor voltage converter

Publication Date: 2022.06.01 NXP BV

Figure 1
Figure 2
Figure 3A~3B

AI summary

Embodiments of switched capacitor voltage converters and methods for operating a switched capacitor voltage converter are disclosed. In an embodiment, a switched capacitor voltage converter includes serially connected switching devices, a voltage generator connected to the serially connected switching devices and configured to generate driver voltages in response to a first voltage at a first terminal that is connected to the serially connected switching devices, and voltage drivers configured to drive the serially connected switching devices based on the driver voltages.