Switching Power-Supply Gate Drive Circuit for Surge Voltage Control
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Solution Overview
Problem
In switching power-supply devices, the high discharging current during turn-on leads to increased surge voltage in rectifier diodes, necessitating the use of higher withstand voltage diodes, which in turn increases forward voltage loss and reduces power-supply efficiency.
Innovation Solution
A switching power-supply device with a transient state detection circuit that outputs a soft-drive instruction signal to delay the charging speed of the gate voltage of the switching element, limiting the discharging current and surge voltage, allowing for the use of lower withstand voltage rectifier diodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If higher withstand voltage rectifier diodes are used to handle surge voltage, then surge voltage is limited, but forward voltage increases and power-supply efficiency deteriorates
Solution Approach 1:
The patent applies preliminary action by detecting transient states before they cause harmful surge voltages and preemptively adjusting the gate resistance to limit the discharging current. The transient state detection circuit identifies conditions such as startup, overload, or voltage resonance beforehand, and the drive circuit proactively increases gate resistance during these periods, preventing excessive surge voltage from developing in the first place.
Solution Approach 2:
The patent implements dynamics by making the gate resistance variable rather than fixed. The drive circuit dynamically adjusts the gate resistance based on real-time operating conditions detected by the transient state detection circuit. During normal operation, low gate resistance enables fast switching; during transient states, high gate resistance limits surge voltage. This dynamic adaptation resolves the contradiction between handling surge voltage and maintaining efficiency.
2Object-affected harmful factors
If gate resistance upon turn-off is increased to extend turn-off fall time, then surge voltage is reduced, but switching speed decreases
Solution Approach 1:
The patent applies dynamics by implementing variable gate resistance that changes based on operating conditions. The drive circuit switches between low resistance (for fast switching during normal operation) and high resistance (for surge suppression during transient states). This dynamic adjustment resolves the contradiction between switching speed and surge voltage reduction.
Solution Approach 2:
The patent applies local quality by applying different gate resistance values to different operational contexts. Instead of using a uniformly high gate resistance that would slow all switching operations, the system uses high resistance only locally during transient states where surge voltage is problematic, while maintaining low resistance during normal operation for optimal switching speed.
3Loss of energy
If soft start and leading edge blanking are stopped to enable normal operation, then power-supply efficiency improves, but discharging current upon turn-on increases and surge voltage increases
Solution Approach 1:
The patent applies preliminary action by detecting transient states before they cause harmful surge voltages and preemptively adjusting the gate resistance to limit the discharging current. The transient state detection circuit identifies conditions such as startup, overload, or voltage resonance beforehand, and the drive circuit proactively increases gate resistance during these periods, preventing excessive surge voltage from developing.
Solution Approach 2:
The patent implements feedback through the transient state detection circuit that continuously monitors operating conditions and provides feedback to the drive circuit. Based on this feedback about transient states, the drive circuit automatically adjusts the gate resistance to appropriate levels, enabling the system to maintain efficiency during normal operation while automatically suppressing surge voltage when needed.
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 limits the discharging current and surge voltage, enabling the use of lower withstand voltage rectifier diodes, reducing costs and improving power-supply efficiency by minimizing forward voltage losses.
Implementation Method 1
a pulse voltage is induced in a secondary winding of the transformer by turning on and off a switching element connected to the primary winding of the transformer
Data Source
AI summary
A switching power-supply device, in which an input power is applied to a primary winding of a transformer, a pulse voltage is induced in a secondary winding of the transformer by turning on and off a switching element connected to the primary winding of the transformer and an output voltage rectified and smoothed by a secondary-side rectifying-and-smoothing circuit having a rectifier diode and a smoothing capacitor is outputted. The switching power-supply device includes: a transient state detection circuit, which detects a transient state and outputs a soft-drive instruction signal; and a drive circuit which turns on-and-off the switching element in a soft-drive operation, in which a charging speed of a gate voltage at a time of passing a gate threshold voltage is delayed as compared to a normal operation, in a case where the soft-drive instruction signal is inputted.