DC/DC Converter Soft Start Control Preventing Capacitor Overcurrent
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Solution Overview
Problem
Conventional DC/DC converters face issues with overcurrents between capacitors, leading to potential damage and inefficiencies, particularly during soft start operations, which can result in unbalanced voltages and component deterioration.
Innovation Solution
A DC/DC converter design that includes a plurality of switching elements, a reactor, low-voltage and high-voltage capacitors, and a charge-discharge capacitor, with a control mechanism that performs soft start control by gradually varying the duty ratio of at least one switching element from 0% to 100%, ensuring that the switching element not performing soft start is turned off, thereby preventing overcurrents and safely unifying both-end voltages across capacitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the duty ratio of switching elements is rapidly increased during soft start, then voltage unification between capacitors is achieved faster, but overcurrent occurs between capacitors causing potential damage
Solution Approach 1:
The patent applies preliminary action by performing soft start control on only one switching element (S1 or S3) before fully activating both switching elements. This preliminary gradual duty ratio increase on a single element prevents overcurrent between capacitors, while the other switching element remains off during this initial phase. Once voltage unification is achieved safely, the second switching element is activated, achieving both component protection and voltage balance.
2Stability of the object's composition
If soft start control is applied to all switching elements simultaneously, then voltage unification is achieved, but overcurrent still occurs between capacitors
Solution Approach 1:
The patent applies segmentation by dividing the soft start process into distinct phases: first, soft start control is applied to only one switching element (S1 or S3) while the other remains off; second, after voltage unification is achieved, the second switching element is activated. This segmented approach prevents overcurrent between capacitors that would occur if all elements were activated simultaneously, while still achieving voltage balance.
3Productivity
If the duty ratio is increased without gradual control, then power conversion efficiency is improved, but switching elements and capacitors may be destroyed by overcurrent
Solution Approach 1:
The patent applies preliminary action by implementing soft start control on one switching element before fully activating the power conversion circuit. This preliminary gradual duty ratio increase prevents overcurrent damage to components, ensuring component durability. After this protective phase, both switching elements operate normally to achieve efficient power conversion, thus maintaining both reliability and productivity.
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 prevents overcurrents between capacitors, allowing for safe unification of voltages, reducing component size and overall device cost, and enhancing operational safety by avoiding potential damage to switching elements and capacitors.
Implementation Method 1
a connection point of the second switching element and the third switching element is connected to the first terminal via the reactor
Implementation Method 2
the charge-discharge capacitor is connected between the connection point of the first switching element and the second switching element and a connection point of the third switching element and the fourth switching element
Data Source
AI summary
A DC/DC converter in which a both-end voltage of each of capacitors can be safely uniformalized while an over current, which is passed through between the capacitors composing the DC/DC converter, is prevented. In a DC/DC converter which includes a plurality of switching elements, a reactor, a low-voltage side capacitor, a high-voltage side capacitor, a charge-discharge capacitor, and a controller which drives and controls the switching elements, the controller performs soft start control in which a duty ratio of at least one of the switching elements is gradually varied from 0% to 100%, and the switching element, in which the soft start control is not performed during the term of the soft start control, is turned off.