Bootstrap Charging for Negative-Bias Drive in Semiconductor Devices
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Solution Overview
Problem
In semiconductor devices with high-side drive circuits performing negative-bias drive, the lack of a connection between the low-voltage terminal and the connection point between high-side and low-side switching elements prevents the charging of a bootstrap capacitor, thereby inhibiting the supply of a drive voltage to the high-side drive circuit.
Innovation Solution
A semiconductor device configuration that includes a high-side and low-side switching element totem-pole connection, a high-side drive circuit with a floating power supply, a reference voltage circuit, and a charging switching element connected to the low-voltage terminal of the high-side drive circuit, allowing the bootstrap capacitor to be charged even during negative-bias drive by utilizing a charging switching element with a control terminal and a grounded second terminal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the low-voltage terminal of the high-side drive circuit is not connected to the connection point between high-side and low-side switching elements (to enable negative-bias drive), then the high-side drive circuit can supply negative voltage to the gate, but the bootstrap capacitor cannot be charged and drive voltage cannot be supplied
Solution Approach 1:
The patent divides the charging function into two separate paths: one path through the low-side switching element for normal operation, and another path through a dedicated charging switching element for negative-bias drive mode. This segmentation allows each path to be optimized for its specific function while resolving the contradiction between negative-bias capability and bootstrap charging reliability.
Solution Approach 2:
The patent introduces a charging switching element as an intermediary component that mediates between the low-voltage terminal and ground to enable bootstrap capacitor charging during negative-bias drive. This intermediary provides the necessary charging path without interfering with the negative-bias functionality, thus resolving the contradiction.
2Adaptability or versatility
If the low-voltage terminal is disconnected from the switching element connection point, then negative voltage supply to gate is enabled, but the potential at low-voltage terminal cannot be made equal to GND potential
Solution Approach 1:
The patent makes the charging switching element controllable and dynamic, allowing it to be turned on only when needed for negative-bias drive mode. This dynamic control enables the system to adapt its configuration based on operating mode, providing negative voltage capability when required while maintaining simple bootstrap charging operation during normal mode.
Solution Approach 2:
The patent changes the operational parameters of the charging switching element based on the drive mode. During negative-bias drive, the charging switching element is activated to provide the necessary charging path, while during normal operation it remains inactive. This parameter change allows the system to maintain both negative-bias capability and ease of bootstrap charging.
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
Enables the supply of a drive voltage to the high-side drive circuit via a bootstrap capacitor during negative-bias drive, improving reliability and circuit operation by ensuring the bootstrap capacitor is charged, even when the low-side switching element is turned on.
Implementation Method 1
a bootstrap capacitor C1 connected between a high-voltage terminal VB and a low-voltage terminal VE of the high-side drive circuit 1
Implementation Method 2
a charging switching element Q3 having a control terminal, a first terminal connected to the low-voltage terminal VE of the high-side drive circuit 1, and a second terminal grounded
Data Source
AI summary
A semiconductor device includes high-side and low-side switching elements totem-pole-connected between high-voltage-side and low-voltage-side potentials; a high-side drive circuit, having high-voltage and low-voltage terminals which are connected to a floating power supply, which supplies either a voltage at the high-voltage terminal or a voltage at the low-voltage terminal for driving the high-side switching element; and a low-side drive circuit driving the low-side switching element and a reference voltage circuit generating a reference voltage between the voltages at high-voltage and low-voltage terminals of the high-side drive circuit. The reference voltage circuit supplies the reference voltage to a connection point between the high-side and low-side switching elements. The semiconductor device includes a charging switching element having a control terminal, a first terminal connected to the low-voltage terminal of the high-side drive circuit, and a grounded second terminal.