Switching Power Supply Startup Control for Inrush Current Suppression
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Solution Overview
Problem
Switching power supply devices face challenges in suppressing inrush current during startup due to the lack of effective control methods that are simple and efficient, particularly in compact applications like vehicles, where mechanical relays increase size and complex phase angle calculations complicate control, leading to accuracy issues.
Innovation Solution
A switching power supply device configuration using thyristors and a control circuit that selectively turns on thyristors during periods of low input voltage amplitude, maintaining the switching element off during startup to gradually charge capacitors and suppress inrush current, thereby simplifying control and reducing device size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If mechanical relays are used to suppress inrush current, then inrush current can be suppressed, but device size increases
Solution Approach 1:
The patent replaces mechanical relays with solid-state thyristors (SCR1 and SCR2) to suppress inrush current. The thyristors are controlled by voltage amplitude detection circuits that trigger them during low-voltage periods, eliminating the need for mechanical components while maintaining inrush current suppression functionality and reducing device size.
2Object-affected harmful factors
If complex phase angle calculations are used for thyristor control, then inrush current can be suppressed, but control complexity increases and accuracy deteriorates
Solution Approach 1:
The patent changes the control parameter from phase angle calculations to voltage amplitude detection. The control circuit detects the absolute amplitude of the input voltage and compares it with a threshold value to determine when to trigger the thyristors. This parameter transformation simplifies the control logic, improves accuracy, and eliminates complex computational requirements while effectively suppressing inrush current.
3Productivity
If thyristors are turned on continuously, then power transfer is efficient, but inrush current cannot be suppressed during startup
Solution Approach 1:
The patent implements periodic control of thyristors based on voltage amplitude detection. During startup, the thyristors are triggered only during periods when the absolute amplitude of the input voltage is below a predetermined threshold, specifically during the latter half of each AC cycle. This periodic, conditional triggering suppresses inrush current during capacitor charging while maintaining efficient power transfer during normal operation.
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 proposed solution effectively suppresses inrush current during startup by simplifying control logic, reducing the need for complex phase angle calculations, and minimizing device size, enhancing operational accuracy and efficiency.
Implementation Method 1
an induction element L1 connected between the first node N1 and a third node N3
Implementation Method 2
a capacitive element C1 connected between a first output node Nout1 and a second output node Nout2
Data Source
AI summary
In a switching power supply device, a control circuit controls a first thyristor, a second thyristor, and a switching element according to an input voltage. The control circuit maintains the first thyristor in an on state while maintaining the second thyristor and the switching element in an off state in a first period in which the absolute amplitude value is equal to or less than a first threshold value within the latter half of a first half-cycle of the input voltage at startup, and maintains the second thyristor in an on state while maintaining the first thyristor and the switching element in an off state in a second period in which the absolute amplitude value is equal to or less than a second threshold value within the latter half of a second half-cycle of the input voltage at startup. The second half-cycle is the half-cycle following the first half-cycle.