Load Drive Circuit Protection Against Flyback Current
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Solution Overview
Problem
In load drive circuits, a flyback current can flow from a common splice load to a freewheeling diode when the ground bolt is detached, potentially damaging the freewheeling diode and protection switch.
Innovation Solution
A load drive circuit design that includes a freewheeling diode and a protection switch connected in series, with a control circuit that detects potential differences and switches off the protection switch to prevent current flow when a rise in potential difference is detected, and a connection circuit that connects control terminals to output a signal for the protection switch, thereby blocking the flyback current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a freewheeling diode is connected to the semiconductor switch to protect against induction energy, then the semiconductor switch is protected, but a flyback current can flow from common splice load to the freewheeling diode when ground is detached, causing damage
Solution Approach 1:
A protection switch is introduced as an intermediary component between the freewheeling diode and the semiconductor switch. This protection switch acts as a mediator that can block flyback current from the common splice load while allowing legitimate freewheeling current to pass through, thereby protecting the freewheeling diode without compromising the original protection function
Solution Approach 2:
The control circuit detects potential differences before flyback current can damage the freewheeling diode and proactively switches off the protection switch to prevent the harmful current flow. By taking preliminary action to block the flyback current path before damage occurs, the system protects the freewheeling diode while maintaining normal operation during legitimate freewheeling events
2Object-affected harmful factors
If a protection switch is added in series with the freewheeling diode to block flyback current, then flyback current is blocked, but the circuit complexity increases
Solution Approach 1:
The protection switch is integrated into the existing freewheeling circuit topology and shares the same physical path as the freewheeling diode. The same protection switch mechanism serves both to block flyback current and to enable legitimate freewheeling current flow, achieving multiple protective functions with a single added component rather than requiring separate circuits for each function
3Ease of operation
If the protection switch is kept on to allow normal operation, then current flow is permitted, but flyback current can damage the freewheeling diode when ground is detached
Solution Approach 1:
The control circuit continuously monitors the potential difference between the ground terminal and reference potential, and based on this feedback information, dynamically controls the protection switch state. When the potential difference exceeds a threshold indicating ground detachment, the control circuit switches off the protection switch to block flyback current. When the potential difference is within normal range, the protection switch remains on to allow legitimate current flow, thus adapting the circuit behavior to actual operating conditions
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
Prevents flyback current from reaching the freewheeling diode and protection switch, preventing damage and ensuring the semiconductor switch operates within safe voltage limits, even when ground terminals are detached.
Implementation Method 1
a freewheeling diode connected to the semiconductor switch
Implementation Method 2
a protection switch that is connected to the freewheeling diode in series, and when the power source is connected in a reverse manner, switches off and blocks flow of a current
Implementation Method 3
when a rise in a potential difference between the first terminal and the second terminal is detected, the connection circuit connects the second control terminal and the first terminal by switching on the connection switch
Data Source
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AI summary
Provide is a load drive circuit. The load drive circuit includes: a power source terminal for connecting a power source; a load terminal for connecting a load to which a voltage is to be supplied from the power source connected to the power source terminal; a semiconductor switch connected between the power source terminal and the load terminal; a control circuit that includes an output terminal that outputs a control signal for opening/closing the semiconductor switch; a freewheeling circuit that includes: a freewheeling diode connected to the semiconductor switch, and a protection switch that switches off and blocks flow of a current from the power source to the semiconductor switch via the freewheeling diode when the power source is connected in a reverse manner; a first terminal for connecting the control circuit to a first fixed potential; a second terminal for connecting an anode of the freewheeling diode to a second fixed potential via the protection switch; and a connection circuit that includes a connection switch installed in a conductive path that connects the output terminal and the first terminal, and when a rise in a potential difference between the first terminal and the second terminal is detected, the connection circuit connects the output terminal and the first terminal by switching on the connection switch.