Switch-Mode Power Supply Start-Up for Zero Net Output Current
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Solution Overview
Problem
Switch-mode power supplies face challenges in starting up without causing transient disruptions to pre-regulated loads, especially due to manufacturing tolerances and inefficiencies in existing voltage regulation methods, which require large overheads and complex compensation mechanisms.
Innovation Solution
A switch-mode power supply system utilizing an inductor and power switches to regulate output voltage through pulse width modulation (PWM) signals, where the start-up circuit combines output and supply voltage currents to emulate duty cycles for continuous conduction mode, allowing for zero net output current delivery and efficient voltage regulation without isolating the load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a switch-mode power supply starts up with conventional methods, then voltage regulation can be achieved, but transient disruptions occur to pre-regulated loads
Solution Approach 1:
The patent applies preliminary action by establishing the inductor current waveform before full power switch operation begins. The controller provides a first pulse timing signal that pre-establishes the current waveform characteristics, ensuring that when the power supply transitions to normal operation, no transient disruptions occur to the pre-regulated load. This preparatory current waveform establishment eliminates the harmful transient effects during start-up.
2Reliability
If LDO series regulators are used for voltage regulation, then good regulation with low noise is achieved, but efficiency drops rapidly as supply voltage increases relative to output voltage
Solution Approach 1:
The patent replaces the LDO series regulator mechanism with a switch-mode power supply architecture. Instead of using a continuously conducting series pass transistor that dissipates excess voltage as heat, the invention uses pulse-width modulation to switch power transistors on and off, transferring energy through an inductor. This substitution of the regulation mechanism eliminates the fundamental efficiency limitation of LDOs while maintaining voltage regulation functionality.
3Loss of energy
If switching regulators are used instead of LDOs, then efficiency improves, but complex compensation mechanisms and large overheads are required during start-up
Solution Approach 1:
The patent extracts and eliminates the complex compensation mechanisms typically required in switching regulators during start-up. By using external voltage levels to directly regulate internal control signals and by pre-establishing the inductor current waveform with a timing signal, the invention removes the need for elaborate compensation circuits. This extraction of unnecessary complexity maintains the high efficiency benefit while simplifying the start-up procedure.
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 approach improves performance by establishing a stable voltage supply without disrupting pre-regulated loads, reducing power dissipation, and eliminating the need for complex compensation mechanisms, thus enhancing efficiency and practicality.
Implementation Method 1
One or more energy storage elements, such as inductor(s) and/or capacitor(s), can be used to convert the switched current pulses into a steady load current
Data Source
AI summary
Apparatus and methods for switch-mode power supply start-up are provided herein. In certain embodiments, a switch-mode power supply includes an inductor and one or more power switches used to control a current through the inductor to provide voltage regulation. The switch-mode power supply uses external voltage levels to regulate one or more internal control signals (for example, for opening or closing the one or more power switches) to their zero output current switching state at the appropriate switch duty cycle. Furthermore, the switch-mode power supply can be implemented to provide a first pulse timing signal to establish the inductor current waveform for zero net output current delivery to a load.