Voltage Clamping Circuit with Current Source for Stable High-Speed Operation

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Solution Overview

Problem

Voltage clamping circuits using MOSFETs face issues with floating output nodes, leading to elevated voltage on the output side due to leaked current, which prevents stable voltage clamping operations, especially in high-speed switching power source devices.

Innovation Solution

A voltage clamping circuit design that includes a MOSFET with a current source between a source/drain route and ground potential, connected to an input terminal, and a capacitor in parallel to manage parasitic capacitance, ensuring stable voltage clamping by preventing output voltage elevation and allowing low power consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a MOSFET is used for voltage clamping without a current source, then the circuit structure is simple, but the output node becomes floating and leaked current causes voltage elevation preventing stable clamping operation

Engineering Contradiction:

Improvecircuit structureVSAvoidvoltage clamping stability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

A current source is introduced as an intermediary component connected between the output node and ground. This current source acts as a mediator that provides a defined current path, preventing the output node from floating and stabilizing the voltage clamping operation by compensating for leaked current without adding complex circuit structures

Inventive Principle:

Principle #24Intermediary (Mediator)

2Device complexity

If the output node is left floating to maintain simple circuit structure, then device complexity is reduced, but leaked current elevates output voltage preventing proper clamping

Engineering Contradiction:

Improvecircuit structureVSAvoidleaked current effect

Core Design Contradiction:

Device complexityVSObject-generated harmful factors

Solution Approach 1:

The leaked current that previously caused harmful voltage elevation is converted into a beneficial effect by introducing a current source that deliberately supplies a controlled current to the output node. This transforms the problematic leaked current into a useful component of the clamping mechanism, where the current source's output current compensates for and controls the effect of leakage currents

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Device complexity

If voltage clamping is performed without considering parasitic capacitance, then the circuit operation is simple, but high-speed operation cannot be achieved due to capacitance effects

Engineering Contradiction:

Improvecircuit operationVSAvoidswitching speed

Core Design Contradiction:

Device complexityVSSpeed

Solution Approach 1:

The electrical parameters of the output node are modified by introducing a current source that can rapidly adjust its output current in response to voltage changes. This dynamic parameter adjustment compensates for parasitic capacitance effects during switching transitions, enabling high-speed operation while maintaining simple circuit structure

Inventive Principle:

Principle #35Parameter changes

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

Enables stable high-speed voltage clamping with low power consumption by controlling the current flow and using a MOSFET with a current source and capacitor to prevent output voltage elevation, ensuring efficient operation in switching power source devices.

Implementation Method 1

using a MOSFET which provides a current source between another source/drain route and a ground potential of the circuit

Methodology Applied

Scientific EffectMOSFET field effect:

Implementation Method 2

a capacitor in parallel to manage parasitic capacitance

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentUS7663354B2Voltage clamp circuit, a switching power supply device, a semiconductor integrated circuit device, and a voltage level conversion circuit

Publication Date: 2010.02.16 RENESAS ELECTRONICS CORP

AI summary

The present invention provides a voltage clamping circuit which is operated in a stable manner with the simple constitution and a switching power source device which enables a high-speed operation. In a switching power source device, one of source/drain routes is connected to an input terminal to which an input voltage is supplied, a predetermined voltage to be restricted is supplied to a gate, and using a MOSFET which provides a current source between another source/drain route and a ground potential of the circuit, a clamp output voltage which corresponds to the input voltage is obtained from another source/drain route. The switching power source device further includes a first switching element which controls a current which is made to flow in an inductor such that the output voltage assumes a predetermined voltage and a second switching element which clamps an reverse electromotive voltage generated in the inductor when the first switching element is turned off to a predetermined potential. In such a switching power source device, the voltage clamping circuit is used in a feedback route for setting a dead time.