High Side Driver Open Circuit Detector
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Solution Overview
Problem
High side drivers in automotive applications can unintentionally turn on inductive loads when they lose their ground connection, leading to uncontrollable operation due to open circuit conditions, posing a safety risk.
Innovation Solution
A high side driver circuit with an integrated open circuit detector powered by a bootstrap capacitor that detects the loss of ground connection and promptly turns off the high side switch to prevent unintended operation, ensuring safety by using a combination of PMOS transistors, current mirrors, and a diode to control the driver circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a high side driver circuit is used to control a load, then the load can be switched on and off, but the circuit may unintentionally turn on when ground connection is lost
Solution Approach 1:
The open circuit detector continuously monitors the ground connection status before the high side driver can unintentionally activate. By detecting ground loss in advance and generating a reset signal to the driver circuit, the system prevents unintended operation before it occurs, rather than reacting after the problem arises
Solution Approach 2:
The detector circuit provides continuous feedback about the ground connection status to the high side driver. When the ground connection is lost, the detector generates a feedback signal that resets the driver circuit, creating a closed-loop control system that maintains reliability by constantly monitoring and responding to ground connection changes
2Reliability
If an open circuit detector is added to the high side driver circuit, then safety is improved, but the circuit complexity increases
Solution Approach 1:
The detector circuit is designed to perform multiple functions: it monitors ground connection status, generates detection signals, and provides reset control to the high side driver. By making the detector multi-functional, the patent reduces the need for separate dedicated components for each function, thereby adding reliability without proportionally increasing circuit complexity
Solution Approach 2:
The open circuit detector and high side driver are integrated into a unified control system where the detector is directly coupled to the driver circuit. This merging allows the detection and control functions to work together seamlessly, reducing the need for additional isolation components and simplifying the overall circuit architecture while maintaining safety functionality
3Loss of time
If a bootstrap capacitor is used to power the detector, then detection time is sufficient, but the detector must wait for capacitor charge
Solution Approach 1:
The bootstrap capacitor is pre-charged during normal operation before an open circuit condition occurs. When ground connection is lost, the pre-charged capacitor immediately provides the necessary voltage to power the detector and generate the reset signal, eliminating detection delay that would occur if the capacitor needed to charge from scratch at the moment of failure
Solution Approach 2:
The bootstrap capacitor serves as an energy reservoir that is charged in advance to cushion against the potential open circuit condition. This pre-stored energy ensures the detector can operate immediately when needed, providing a time buffer that allows sufficient detection and response time without being constrained by real-time charging requirements
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 the high side switch from unintentionally turning on in case of an open circuit condition, thereby ensuring the safety and controlled operation of loads like electric motors by using a bootstrap capacitor to provide the necessary time for detection and response.
Implementation Method 1
the open circuit detector is supplied by a bootstrap capacitor which is coupled to the load
Data Source
AI summary
A circuit comprises a switch, a driver circuit, and an open circuit detector. The switch has a first current electrode coupled to a power supply terminal, a second current electrode coupled to supply a current to a load, and a control electrode. The driver circuit has an input for receiving a control signal, and an output coupled to the control electrode of the switch. The open circuit detector has a first terminal coupled to receive a voltage from a bootstrap capacitor, a second terminal coupled to the power supply terminal, and a control terminal coupled to the driver circuit. The open circuit detector detects an open circuit, and in response, provides a signal at the control terminal for causing the driver circuit to open the switch.