DC-DC Converter Mode Transition Circuit for Stable PWM-PFM Switching
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Solution Overview
Problem
Transitions between pulse-width modulation (PWM) and pulse-frequency modulation (PFM) modes in DC-DC converters can introduce voltage transients, leading to incorrect regulation of the output voltage due to enabling or disabling the transconductance amplifier, causing current consumption issues and inefficiencies.
Innovation Solution
A multi-mode transition circuit that includes a transconductance amplifier, comparator, and switches connected to RC networks and a multiplexer, with an operation mode selector that enables or disables the transconductance amplifier and controls the switches in a specific sequence to manage transitions between PWM and PFM modes, minimizing voltage transients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the transconductance amplifier is enabled or disabled during mode transition, then current consumption is optimized, but voltage transients are introduced causing incorrect voltage regulation
Solution Approach 1:
The circuit prepares the reference voltage by connecting it to the RC network before disabling the transconductance amplifier during mode transition. This preliminary action ensures the reference voltage is already established and stable, preventing voltage transients when the amplifier is disabled, thus maintaining voltage regulation accuracy while optimizing current consumption
Solution Approach 2:
The RC network acts as an intermediary between the reference voltage and the transconductance amplifier. It filters and smooths the reference voltage signal, preventing direct coupling of voltage transients to the amplifier during mode transitions, thereby maintaining stable voltage regulation while allowing the amplifier to be disabled for current optimization
2Use of energy by moving object
If the transconductance amplifier is disabled in PFM mode, then current consumption is reduced, but voltage transients occur during mode transition
Solution Approach 1:
The reference voltage is connected to the RC network in advance before the transconductance amplifier is disabled during PFM mode transition. This ensures the reference voltage is already prepared and stable, eliminating voltage transients that would otherwise occur when the amplifier is disabled, thus reducing current consumption without generating harmful voltage transients
Solution Approach 2:
The RC network converts the potentially harmful voltage transients into a stable reference voltage by filtering and smoothing the signal during mode transition. This transforms the harmful effect of amplifier disabling into a beneficial stable reference, allowing current consumption to be reduced while eliminating the harmful voltage transients
Data Source
AI summary
Embodiments of a multi-mode transition circuit for a DC-DC converter and a DC-DC converter are disclosed. In an embodiment, a multi-mode transition circuit for a DC-DC converter includes a transconductance amplifier operably connected to a first resistor-capacitor (RC) network and switches, a comparator operably connected to a second RC network, where the first and second RC networks are operably connected to a reference voltage, a multiplexer operably connected to the transconductance amplifier and the comparator, and an operation mode selector configured to enable or disable the transconductance amplifier and turn on or off the switches in a sequence when transitioning between a pulse-frequency modulation (PFM) mode and a pulse-width modulation (PWM) mode.