| 摘要 |
A fault disconnection electronics circuit (FDE) particularly suited to intrinsically safe applications where the supply or source voltage of the circuit to be protected is not fixed, and limiting the maximum power provided to the load is desirable. A typical example may be in a fieldbus application. An electric circuit has a power source 1, 4, a load and an FDE protection circuit, where the FDE circuit comprises a current sense resistor 5, a control device 3, a series element 6 and a voltage reference circuit 8. The reference circuit provides a reference voltage that is inversely proportional to the power source voltage, and the current sense resistor develops a voltage representing the current in the electric circuit. The control device controls the series element using the reference voltage and the voltage developed by the current sense resistor such that the current trip level varies inversely with the source voltage, and a substantially constant maximum power limit is delivered into the load. The transfer function of the voltage reference circuit may linear or non-linear and may be adjusted by a thermal device or microprocessor. |
