Switching Regulator Inrush Current Suppression
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Solution Overview
Problem
Existing switching regulators experience a large inrush current during power start-up, which can damage components like the power transistor and current detection resistor, and conventional soft start circuits are ineffective in suppressing this issue without occupying a large area.
Innovation Solution
A switching regulator with a pulse width modulation (PWM) signal generator, an over current detection circuit, and a signal adjustment circuit that adjusts the PWM or clock signal based on an over current signal to control the ON time of the power transistor, preventing excessive current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the power transistor operates under maximum duty during start-up to achieve fast voltage conversion, then the voltage conversion speed is improved, but a large inrush current occurs that can damage components
Solution Approach 1:
The control circuit performs preliminary action by detecting the start-up state and automatically adjusting the duty cycle before the inrush current can damage components. The circuit prepares the power transistor with a limited duty cycle during start-up, then transitions to normal operation once the output voltage reaches the target level.
Solution Approach 2:
The control circuit uses feedback by continuously monitoring the output voltage and comparing it with the target voltage. Based on this feedback, the control circuit adjusts the duty cycle of the power transistor - maintaining maximum duty when voltage is adequate, but reducing duty during start-up when output voltage is low to prevent inrush current.
2Object-affected harmful factors
If a conventional soft start circuit is added to increase start-up duration, then the inrush current is reduced, but the circuit area increases and the solution remains ineffective
Solution Approach 1:
The control circuit performs multiple functions: it serves as both the main voltage conversion controller and the inrush current suppressor. By integrating the start-up protection function into the existing control circuit logic, the patent eliminates the need for separate soft start circuits, thereby reducing circuit area while maintaining effective inrush current suppression.
Solution Approach 2:
The control circuit provides self-service by automatically detecting its own operating state and adjusting its control parameters accordingly. The circuit monitors output voltage levels and autonomously modifies the duty cycle without external intervention, making the system self-protecting against inrush current while minimizing additional hardware.
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 solution effectively reduces inrush current, preventing component damage and eliminating the need for a large-area circuit, thereby ensuring safe and efficient power start-up.
Implementation Method 1
A flyback regulator is an isolation type regulator using a transformer to covert an input voltage to an output voltage. The energy is stored and transformed through charging and discharging of the windings of the transformer.
Implementation Method 2
The secondary side circuit transmit signals to the primary side circuit through an opto-coupler 12, for sending the feedback signal COMP to the control circuit 15.
Data Source
AI summary
The present invention discloses a switching regulator, including: a power stage including at least one power transistor which switches according to a switch control signal to convert an input voltage to an output voltage; a pulse width modulation (PWM) signal generator generating a PWM signal according to the output voltage; an over current detection circuit comparing a current sensing signal with a reference signal to generate an over current signal indicating whether an over current is occurring; and a signal adjustment circuit adjusting the PWM signal or a clock signal to generate the switch control signal for controlling an ON time of the power transistor of the power stage.