Dual-Path Start-Up Circuit for Low-Loss High-Voltage Biasing
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Solution Overview
Problem
Low-dropout regulators (LDOs) in power converter start-up circuits experience high power loss and heat dissipation due to their operation at high voltages, even with small output currents, which is inefficient and can lead to unacceptable power loss.
Innovation Solution
A dual path and mode start-up circuit that includes a high-voltage start-up circuit and an auxiliary start-up circuit, with a sensing circuit to switch between two modes of operation based on the voltage level at a capacitor, allowing the auxiliary circuit to handle quiescent current and reduce power loss by adjusting output voltage levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an LDO is configured to operate at high voltage to provide initial power and bias voltages, then the output voltage can be regulated even when supply voltage is close to output voltage, but power loss and heat dissipation become unacceptably high
Solution Approach 1:
The LDO's output voltage is made dynamically adjustable based on operating conditions. A control circuit monitors the supply voltage and auxiliary current, then adjusts the LDO's output voltage accordingly - using higher voltages when needed for startup and biasing, and reducing to zero or minimal voltages during normal operation to eliminate power loss.
Solution Approach 2:
The invention changes the operating parameters of the LDO based on system state. The output voltage parameter is varied from high levels during startup/biasing phases to zero or minimal levels during normal operation. This parameter change allows the system to maintain voltage regulation capability when needed while eliminating power loss during steady-state operation.
2Stability of the object's composition
If the LDO operates continuously to maintain voltage regulation, then output voltage stability is maintained, but quiescent current consumption remains high causing power loss
Solution Approach 1:
The LDO operates in periodic cycles rather than continuously. It activates during startup to provide initial power and bias voltages, then reduces to minimal or zero operation during normal power converter operation. This periodic action pattern allows voltage stability when needed while minimizing quiescent current consumption during steady-state.
Solution Approach 2:
The invention extracts the LDO's function to only when necessary - specifically for startup and biasing phases. During normal operation, the power converter's own auxiliary winding provides the necessary voltages, making the LDO's continuous operation unnecessary. This extraction of the LDO's functional requirement eliminates continuous quiescent current consumption.
3Power
If the LDO is designed to handle high voltage operation, then it can provide sufficient bias voltages for controllers and drivers, but device size increases due to higher voltage rating components
Solution Approach 1:
The LDO's voltage rating requirement is reduced dynamically. Instead of being designed for continuous high-voltage operation, it only needs to handle high voltages temporarily during startup and biasing phases. This allows the use of lower voltage-rated, smaller components while still meeting the high voltage capability requirement when needed.
Data Source
AI summary
A dual path and mode start-up circuit includes a high-voltage start-up circuit, an auxiliary start-up circuit, a capacitor, and a sensing circuit. The high-voltage start-up circuit has high-voltage input and output voltage nodes and is configurable to be operated in a first or second mode of operation. The auxiliary start-up circuit has auxiliary input and output voltage nodes. The auxiliary output voltage node, the high-voltage output voltage node, and the capacitor are in signal communication. The sensing circuit is configured to sense a voltage level at the capacitor and to configure the high-voltage start-up circuit to operate in the first mode of operation if the voltage level at the capacitor is less than a first threshold voltage level, and configure the high-voltage start-up circuit to operate in the second mode of operation if the voltage level at the capacitor is greater than a second threshold voltage level.