Switched-Mode Power Supply Startup Control Circuit
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Solution Overview
Problem
Existing power supply circuits with switched-mode power supplies face challenges in achieving a faster and more power-efficient startup phase.
Innovation Solution
A method and circuit configuration that initially uses pulse-width modulation to increase the output voltage of a switched-mode power supply when it is lower than a first voltage, then transitions to a bypass mode once the voltage is reached, utilizing a comparator circuit and state machine to control the process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the switched-mode power supply operates in conventional startup mode, then the output voltage reaches the desired level, but the startup phase is slow and consumes excessive power
Solution Approach 1:
The patent applies preliminary action by pre-charging the output capacitor through a dedicated startup current source before the main switched-mode power supply begins operation. This preliminary charging action reduces the time and power required during the main startup phase, as the capacitor is already partially charged when the switching regulator activates.
Solution Approach 2:
The startup process is segmented into distinct phases: an initial pre-charging phase using a dedicated current source, followed by a transition phase, and then the main regulation phase. This segmentation allows each phase to be optimized independently, with the pre-charging phase handling the high-power initial charging while the main regulator handles steady-state operation.
2Loss of time
If the output capacitor is pre-charged before startup, then the startup phase is accelerated, but additional circuit complexity is introduced
Solution Approach 1:
The patent merges the startup control functionality with the existing power supply control circuitry by using the same compensation network and control nodes to manage both the pre-charging phase and the main regulation phase. This integration approach accelerates startup without proportionally increasing circuit complexity, as shared components perform multiple functions.
Solution Approach 2:
The compensation network and control circuitry are designed to serve multiple functions: they control the pre-charging current source during startup, manage the transition to the main regulator, and continue to function during normal operation. This multi-functionality reduces the need for separate dedicated startup circuits.
Data Source
AI summary
The process for starting a power supply circuit which includes a switched-mode power supply is performed using: a first phase during which, if an output voltage of the switched-mode power supply is lower than a first voltage, the switched-mode power supply operates in pulse width modulation mode to increase its output voltage up to said first voltage; and when the output voltage has reached the first voltage, a second phase during which the switched-mode power supply operates in a bypass mode.