High-Side Gate Drive Voltage Compensation in Bootstrap Circuits
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Solution Overview
Problem
The existing voltage generation circuits for high-side switching elements in power semiconductor modules suffer from voltage deviations due to voltage drops in bootstrap circuits, leading to inferior characteristics compared to low-side switching elements.
Innovation Solution
A voltage generation circuit that includes a bootstrap circuit and a step-down circuit, where the step-down circuit generates a compensated power supply voltage by adding a compensation voltage to the control power supply voltage for the low-side drive circuit, ensuring an appropriate voltage range for the high-side drive circuit, thereby improving the characteristics of the high-side switching element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bootstrap circuit with a diode and limiting resistor is used to generate control power supply voltage for the high-side drive circuit, then the circuit is protected from overcurrent, but voltage drops occur causing the control power supply voltage to deviate from the appropriate voltage range
Solution Approach 1:
The step-down circuit performs preliminary voltage adjustment before the voltage reaches the bootstrap circuit. By pre-stepping down the power supply voltage and adding compensation voltage, the circuit anticipates and corrects for the voltage drops that will occur in the bootstrap diode and limiting resistor, ensuring the final control power supply voltage is accurate.
Solution Approach 2:
The invention changes the voltage parameter by introducing a variable compensation voltage that dynamically adjusts to compensate for the voltage drops in the bootstrap circuit. The step-down circuit modifies the power supply voltage parameter to account for the forward voltage of the diode and the voltage drop across the limiting resistor.
2Ease of operation
If the control power supply voltage for the high-side drive circuit is generated from the control power supply voltage for the low-side drive circuit, then the high-side switching element can be controlled, but the characteristics of the high-side switching element become worse than those of the low-side switching element
Solution Approach 1:
The step-down circuit acts as an intermediary between the power supply and the bootstrap circuit. It processes the power supply voltage by stepping it down and adding compensation voltage before it reaches the bootstrap circuit, thereby mediating the voltage levels to ensure both high-side and low-side switching elements operate with appropriate and equal characteristics.
3Device complexity
If a bootstrap circuit is used to generate control power supply voltage for the high-side drive circuit, then the circuit configuration is simplified, but voltage drops due to the diode and limiting resistor cause the voltage to deviate from the appropriate range
Solution Approach 1:
The invention merges the step-down circuit functionality with the bootstrap circuit by integrating the voltage compensation mechanism into the existing bootstrap structure. The step-down circuit and bootstrap circuit work together as a unified system, combining their functions to achieve both voltage reduction and overcurrent protection while maintaining accurate control power supply voltage.
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 stabilizes the drive characteristics of the high-side switching element by maintaining the control power supply voltage within an appropriate range, immune to transient responses, and reduces the size and cost of semiconductor chips.
Implementation Method 1
The step-down circuit outputs a compensated power supply voltage to the bootstrap circuit. The compensated power supply voltage is generated by stepping down a power supply voltage which is applied to the high potential side of the high-side switching element.
Implementation Method 2
The bootstrap circuit is provided with a bootstrap diode and a limiting resistor to protect the circuit from overcurrent. When the control power supply voltage for the high-side drive circuit is generated, a voltage drop corresponding to the forward voltage of the bootstrap diode occurs.
Data Source
AI summary
Provided is a voltage generation circuit for improving the characteristics of a high-side switching element by applying an appropriate control power supply voltage to the high-side drive circuit. The voltage generation circuit includes a bootstrap circuit and a step-down circuit. The bootstrap circuit includes a diode and a current limiting resistor. The step-down circuit is connected to a high potential side of the high-side switching element and an input side of the bootstrap circuit. The step-down circuit outputs a compensated power supply voltage generated by stepping down a power supply voltage applied to the high potential side of the high-side switching element to the bootstrap circuit. The step-down circuit generates the compensated power supply voltage obtained by adding a compensation voltage corresponding to a voltage drop due to the diode and the current limiting resistor to a control power supply voltage for a low-side drive circuit.