Multi-Mode Timer Circuit for Seamless PWM PFM Transition

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Solution Overview

Problem

Existing power converters struggle to seamlessly transition between Pulse Width Modulation (PWM) and Pulse Frequency Modulation (PFM) modes, leading to frequency jitter and voltage ripple at the output, which affects the consistency of DC voltage delivery.

Innovation Solution

A multi-mode timer circuit is introduced to control the switching cycle, setting off times based on input and output voltages and load current, enabling seamless transitions between PWM and PFM modes by adjusting the off time calculations accordingly.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If separate circuitry is used for PWM and PFM modes, then mode transition reliability is improved, but device complexity increases

Engineering Contradiction:

Improvemode transition reliabilityVSAvoidcircuit complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent combines PWM and PFM control circuits into a single integrated controller that can seamlessly switch between modes. The controller includes a unified timing circuit that generates both PWM and PFM signals, eliminating the need for separate circuitry while maintaining reliable mode transitions through a shared control architecture.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The controller is designed with multi-functional capabilities to perform both PWM and PFM operations using the same hardware resources. The timing circuit and control logic are configured to operate in either mode depending on load conditions, reducing overall device complexity while ensuring reliable transitions through a universal control platform.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Productivity

If fast switching transitions are implemented, then productivity is improved, but frequency jitter increases

Engineering Contradiction:

Improveswitching transition speedVSAvoidfrequency jitter

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent implements dynamic switching transition mechanisms that adapt the switching speed based on operating conditions. The controller uses gradual mode transition techniques where the switching frequency is smoothly adjusted rather than abruptly changed, allowing fast overall transition while minimizing frequency jitter through controlled ramping of switching parameters.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The control circuit incorporates feedback mechanisms that monitor switching frequency and load conditions during mode transitions. This feedback is used to dynamically adjust the transition timing and magnitude, enabling fast switching responses while actively compensating for and reducing frequency jitter through real-time correction.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS11081957B2Power converter with multi-mode timing control

Publication Date: 2021.08.03 TEXAS INSTRUMENTS INC

AI summary

A converter circuit includes a power stage circuit configured to convert an input voltage to an output voltage provided at an output, and a control circuit configured to control the power stage circuit. The control circuit is configured to operate in one of a pulse frequency modulation (“PFM”) mode and a pulse width modulation (“PWM”) mode depending on a current supplied to the output. The control circuit includes a multi-mode timer circuit configured to provide a switching signal to set an off time for each switching cycle of the power stage circuit during the PFM mode and during the PWM mode.