Step-up Power Supply Device with MOS Transistor Switch
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Solution Overview
Problem
Conventional step-up power supply devices with bipolar transistors experience high inrush currents and inefficiencies, especially at low input voltages, leading to battery performance deterioration and difficulty in achieving high switching frequencies.
Innovation Solution
A step-up power supply device utilizing a MOS transistor as the switch element, with a startup circuit and control circuit that generate pulse signals and compare currents to restrict peak currents, and a comparator to manage the transition between startup and control operations, ensuring efficient voltage boosting while suppressing inrush currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a bipolar transistor is used as the switch element in a step-up power supply device, then the device can operate at low input voltages, but high inrush currents occur and battery performance deteriorates
Solution Approach 1:
The patent changes the switch element from a bipolar transistor to a MOS transistor. This parameter change fundamentally alters the electrical characteristics, enabling low input voltage operation while suppressing inrush currents through the MOS transistor's inherent current control capabilities and lower on-resistance.
2Device complexity
If a bipolar transistor is used as the switch element, then the circuit can be simplified, but switching frequency is limited and power loss increases
Solution Approach 1:
The patent changes the switch element type from bipolar transistor to MOS transistor. This parameter change enables higher switching frequencies due to the MOS transistor's faster switching characteristics and lower parasitic inductance, while also reducing conduction losses through lower on-resistance.
3Power
If the output voltage is boosted to reference voltage from low input voltage, then the step-up converter can operate, but the drive signal duty ratio becomes excessively large
Solution Approach 1:
The patent changes the switch element to a MOS transistor, which provides better voltage control and lower on-resistance. This enables more efficient voltage boosting with optimized duty ratios, as the MOS transistor's characteristics allow for precise control of the switching waveform and reduced voltage drops during conduction.
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
The solution effectively restricts peak currents, stabilizes output voltage, and prevents battery performance degradation, enabling efficient operation across a wide range of input voltages while minimizing inrush currents.
Implementation Method 1
an inductor and switch element which are connected in series and a rectifier and smoother which rectify and smooth a voltage across the switch element, the step-up converter being designed such that an input voltage to the inductor is boosted by an on/off operation of the switch element
Data Source
AI summary
A step-up power supply device includes: a step-up converter; a startup circuit which controls the on/off operation of a switch element of the step-up converter when an output voltage of the device is smaller than a reference voltage; and a control circuit which operates in substitution for the startup circuit when the output voltage is higher than the reference voltage to control the on/off operation of the switch element such that the output voltage reaches a target value. The startup circuit includes an oscillation circuit for generating a pulse signal which has a predetermined on/off ratio, a current comparison circuit for comparing a current of the switch element with a predetermined restriction value, and a drive circuit for generating a drive signal based on which the switch element is turned on/off, the drive signal being generated from the pulse signal to turn on the switch element, and the drive signal being generated from the output of the current comparison circuit or the pulse signal to turn off the switch element.