Switch Driving Circuit Protection Against Negative Voltage Latch-Up
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Solution Overview
Problem
Conventional switch driving circuits suffer from malfunctions and element damage due to negative voltage fluctuations, leading to latch-up of power switches and overcharging of bootstrap capacitors, caused by parasitic diodes and inductors in the circuit.
Innovation Solution
A switch driving circuit with a protection unit that generates a sense voltage proportional to the absolute value of the second voltage, compares it with a reference voltage, and controls the switching operation of the power switch to prevent overcharging by stopping the switching operation when the sense voltage exceeds the reference voltage, thereby preventing latch-up and element damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the power switch is turned off and freewheeling current flows through the diode and inductor, then the current recycles properly, but the source voltage drops below ground voltage causing the parasitic diode to turn on and the bootstrap capacitor to overcharge
Solution Approach 1:
The patent applies preliminary anti-action by introducing a protection unit that proactively detects negative voltage conditions before they cause harmful effects. The protection unit monitors the source voltage and preemptively responds by controlling the power switch to prevent the parasitic diode from turning on, thereby preventing bootstrap capacitor overcharge and circuit malfunction
Solution Approach 2:
The patent implements feedback by using a protection unit that continuously monitors the source voltage and uses this information to control the power switch operation. When the source voltage drops below ground voltage, the feedback mechanism triggers the protection unit to adjust the switching operation, preventing the harmful chain reaction of parasitic diode conduction and capacitor overcharge
2Reliability
If the parasitic diode turns on due to negative voltage, then the bootstrap capacitor charges excessively, but this causes element damage and latch-up of the power switch
Solution Approach 1:
The protection unit applies preliminary anti-action by detecting negative voltage conditions before they lead to parasitic diode conduction and bootstrap capacitor overcharge. By preemptively controlling the power switch based on voltage monitoring, the system prevents the harmful sequence of events that would otherwise cause element damage and latch-up
Solution Approach 2:
The patent implements preliminary action by establishing a protection mechanism that is ready to act before damage occurs. The protection unit continuously monitors voltage conditions and is positioned to intervene early in the failure sequence, controlling the power switch before the parasitic diode can turn on and before the bootstrap capacitor can overcharge to damaging levels
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 prevents overcharging and element damage by ensuring the power switch is turned off when the sense voltage becomes negative, thereby maintaining the stability of the switch driving circuit and preventing latch-up.
Implementation Method 1
a protection unit that generates a sense voltage corresponding to the second voltage
Implementation Method 2
compares a predetermined reference voltage with the sense voltage
Implementation Method 3
a bootstrap capacitor having a first end connected to an output terminal of the power switch and a second end to which the power voltage is supplied
Implementation Method 4
a voltage drop occurs at both ends of the parasitic inductor Lp due to the freewheeling current. The voltage drop that occurs at both ends of the parasitic inductor Lp is a value obtained by multiplying inductance of the parasitic inductor Lp by (di/dt)
Implementation Method 5
the bootstrap voltage Vb becomes lower than the ground voltage so that the parasitic diode Dp of the switch driving circuit 10 is turned on
Data Source
AI summary
The present invention relates to a switch driving circuit and a driving method thereof. The switch driving circuit according to the present invention is supplied with a first voltage and a second voltage, is driven by a voltage difference between the first and second voltages, controls a switching operation of a power switch according to a switch driving control signal, generates a sense voltage corresponding to the second voltage, compares a predetermined reference voltage with the sense voltage, and stops the switching operation of the power switch according to the comparison result.