Load Drive Circuit With Pre-Drive Short-Circuit Diagnosis
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Solution Overview
Problem
Conventional load drive devices face issues with short-circuit failures, leading to excessive current flow and potential circuit breakdown due to the inability to limit current effectively during normal control operations, necessitating the use of absolute maximum rated drivers and resulting in inefficient and costly solutions.
Innovation Solution
A load drive device incorporating a drive switch, a switch drive circuit, and a constant current source that supplies current without passing through the drive switch, with control mechanisms to prevent the drive switch from turning on when a voltage threshold is reached, thereby diagnosing short-circuits and preventing excessive current flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If normal load drive control is performed without preliminary diagnosis, then the load can operate normally, but excessive current flows when short-circuit failure occurs causing circuit breakdown
Solution Approach 1:
The patent applies preliminary action by performing load short-circuit diagnosis before load drive control. The control unit executes a diagnosis routine that supplies a first current through the load and measures the voltage to detect short-circuit failures. Only after confirming normal operation does the system proceed to normal load drive control, preventing excessive current flow and circuit damage while maintaining operational reliability.
2Reliability
If absolute maximum rated driver is selected to withstand large current, then circuit safety is improved, but component cost and device complexity increase
Solution Approach 1:
The patent eliminates the need for absolute maximum rated drivers by implementing preliminary short-circuit diagnosis. The control unit measures voltage across the load during a diagnostic current supply phase, calculates resistance, and determines whether the load is short-circuited before normal operation. This allows the use of normally-rated drivers without requiring oversized components for fault tolerance.
Solution Approach 2:
The patent introduces an intermediary diagnostic process between power supply and normal operation. The control unit acts as an intermediary that mediates between the power supply unit and the load by first performing resistance measurement through controlled current supply and voltage measurement, then deciding whether to permit normal operation based on the diagnostic results.
3Measurement precision
If diagnosis is performed by supplying current that does not cause fuel injection, then short-circuit detection is achieved, but current still flows to short-circuited load causing heat generation
Solution Approach 1:
The patent applies parameter changes by controlling the magnitude and duration of the diagnostic current. The control unit supplies a first current specifically designed for resistance measurement that is sufficient to generate measurable voltage but limited to minimize energy loss. The system measures voltage during this controlled parameter state, calculates resistance, and quickly transitions to normal operation or shutdown, minimizing heat generation in short-circuited loads.
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
This configuration allows for the diagnosis of short-circuits before load drive control, preventing large current flows during normal operations and reducing the need for high-rated drivers, thus enhancing safety and reducing component costs.
Implementation Method 1
a constant current source that supplies a current to the load without passing through the drive switch
Implementation Method 2
when a voltage between both ends of the load becomes equal to or less than a determination value
Data Source
AI summary
A large current flowing when energization by normal load drive control is performed at the time of a load short-circuit is prevented. A load drive device 100 includes drive switches 61 and 62 that turn on or off the current supplied from a power source to a load 70, a switch drive circuit 20 that transmits a drive signal to the drive switches 61 and 62 based on a control command from an arithmetic device 10, and a constant current source 40 that supplies the current to the load 70 without passing through the drive switches 61 and 62. Then, the switch drive circuit 20 performs control so as not to turn on either the drive switches 61 or 62 when the voltage between both ends of the load 70 becomes equal to or less than the determination value in a state where the drive switches 61 and 62 are turned off and in a state where the current is supplied from the constant current source 40 to the load 70.