Gate Driver Bootstrap Undervoltage Detection With Current Mirror
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Solution Overview
Problem
Existing gate driver circuits for N-type high-side transistors face challenges in reliably turning on the transistor due to insufficient potential difference across the bootstrap and switching lines, leading to inefficiencies and high current consumption.
Innovation Solution
A gate driver circuit with an under voltage detection circuit using a current mirror and MOS transistors for accurate threshold detection, coupled with resistors and a comparator to manage potential differences and reduce current consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bootstrap circuit is used to drive the high-side transistor, then the transistor can be turned on, but the potential difference between the bootstrap line and output line becomes insufficient, leading to unreliable transistor operation
Solution Approach 1:
The circuit performs preliminary voltage level adjustment by boosting the bootstrap line voltage before the transistor switching operation. The voltage boosting circuit pre-charges the bootstrap capacitor to a higher voltage level, ensuring that when the high-side transistor needs to turn on, sufficient gate-source voltage is already available, eliminating the need for excessive current during the switching event.
Solution Approach 2:
The invention changes the voltage parameter of the bootstrap line by introducing a voltage boosting circuit that increases the bootstrap voltage beyond the standard supply voltage. This parameter change ensures that the potential difference between the bootstrap line and output line remains sufficient even when the output line voltage rises, maintaining reliable transistor operation without increasing current consumption.
2Reliability
If the potential difference between bootstrap line and output line is increased to ensure reliable transistor turn-on, then transistor operation becomes reliable, but current consumption increases
Solution Approach 1:
The voltage boosting circuit serves multiple functions: it boosts the bootstrap voltage to ensure reliable high-side transistor turn-on, it provides stable voltage reference for the gate driver, and it reduces the burden on the bootstrap capacitor. By making this circuit multi-functional, the patent avoids adding separate circuits for each function, thereby limiting the increase in overall circuit complexity while achieving reliable transistor operation.
3Device complexity
If conventional bootstrap circuit design is used, then circuit simplicity is maintained, but accurate detection of under voltage states becomes difficult
Solution Approach 1:
The patent introduces an intermediary voltage detection circuit that monitors the actual voltage level at the bootstrap line and compares it against threshold values. This intermediary detection mechanism provides accurate under-voltage detection without requiring complex external monitoring equipment, maintaining circuit simplicity while achieving precise voltage state detection through the dedicated comparison circuitry.
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 enables reliable transistor operation with reduced current consumption, enhancing efficiency and accuracy in detecting under voltage states.
Implementation Method 1
a bootstrap line BST to be connected to the high-side transistor MH via a bootstrap capacitor CBST
Implementation Method 2
the under voltage detection circuit includes a current mirror circuit CM1 connected to the bootstrap line BST
Implementation Method 3
a comparator 262 comparing a voltage drop across the second resistor R2 with a threshold voltage
Data Source
AI summary
An under voltage detection circuit compares a potential difference between a bootstrap line and an output line with a threshold voltage. A voltage line generates a voltage lower by a predetermined voltage than the bootstrap line. A current mirror circuit is connected to the bootstrap line. A first resistor and a MOS diode are connected in series between an input node of the current mirror circuit and the output line. A second resistor is connected between an output node of the current mirror circuit and the voltage line. A comparator compares a voltage drop across the second resistor with a threshold voltage.