Pre-Driver Circuit With Voltage Sharing and Reverse Protection
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Solution Overview
Problem
Existing pre-drivers cannot handle voltages greater than 20 V when used as low-side drivers in vehicles, as they rely on field effect transistors with isolated N-type rings that are limited to such voltages, and fail to prevent current flow from ground to output pins during high-side operation.
Innovation Solution
Incorporating a third field effect transistor connected to ground and a reverse protection circuit, along with control circuits that manage the switching of these transistors based on driver configuration and voltage thresholds, allowing the pre-driver to distribute voltage bearing across multiple transistors and prevent reverse current flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a field effect transistor with isolated N-type ring is used, then the pre-driver can operate as a high-side driver with negative voltage capability, but the maximum voltage bearing capacity is limited to 20 V
Solution Approach 1:
The voltage bearing function is segmented between two field effect transistors (Mpd and Mshort). When used as a low-side driver, Mpd bears a first portion of the voltage while Mshort bears a second portion, allowing the pre-driver to handle voltages exceeding 20 V without requiring a single high-voltage transistor
2Temperature
If a field effect transistor with isolated N-type ring is used, then the pre-driver can bear negative voltage, but it cannot bear voltages greater than 20 V in low-side driver configuration
Solution Approach 1:
The voltage bearing capacity is segmented across multiple transistors. Mpd maintains its isolated N-type ring structure for negative voltage capability, while Mshort is added to share the high voltage burden, enabling both negative voltage operation and high voltage bearing capacity simultaneously
Solution Approach 2:
The pre-driver is designed to be universally applicable to both high-side and low-side driver configurations. The same circuit structure can operate with negative voltages in high-side mode and bear high voltages up to 100 V or more in low-side mode through the voltage sharing mechanism
3Strength
If the pre-driver is configured as a low-side driver with high voltage capability, then it can bear voltages greater than 20 V, but it lacks reverse protection against current flow from ground to output pins
Solution Approach 1:
A reverse protection circuit is introduced as an intermediary between the output pins and ground. This circuit actively prevents harmful reverse current flow while allowing normal operation, thereby improving reliability without compromising the high voltage bearing capability
Data Source
Figure 1A~1B
Figure 1C
Figure 2
AI summary
The present invention relates to a pre-driver, comprising: a first field effect transistor (Mpu), with a source thereof being connected to a power supply input pin (VPR) of the pre-driver; a second field effect transistor (Mpd), with a drain thereof being connected to a drain of the first field effect transistor and connected to a first output pin (Gate) of the pre-driver, and a source of the second field effect transistor being connected to a second output pin (Srce) of the pre-driver, wherein the first and second field effect transistors are controlled to switch on alternately; a third field effect transistor (Mshort), with a source thereof being connected to ground; a reverse protection circuit (Mreverse), for preventing current flow from the ground to the second output pin; and a first control circuit (20), for causing the third field effect transistor to be in an OFF state when a control signal (Cfg_LS) indicates that the pre-driver is used as a high-side driver or when the control signal indicates that the pre-driver is used as a low-side driver and a voltage of the first output pin is greater than a voltage threshold, and for causing the third field effect transistor to be in an ON state when the control signal indicates that the pre-driver is used as a low-side driver and a voltage of the first output pin is not greater than the voltage threshold. The pre-driver can bear a greater voltage.