| 摘要 |
A functional element is prevented from breakdown and deterioration because of mounting and demounting of the functional element immediately after cut-off of driving power from a constant-current power supply or during supply of the driving power. An electric circuit is configured to electrically connect a constant-current power supply 1 having a capacitance between an output terminal and a reference potential terminal and a detachable functional element 2 to each other. The electric circuit has an element breakdown prevention circuit 10 having a first circuit terminal connected to an output terminal of the constant-current power supply 1 through the functional element 2, and a second circuit terminal connected to the reference potential terminal of the constant-current power supply 1 through the functional element 2. The element breakdown prevention circuit 10 increases an impedance between the circuit terminals to a disconnected state impedance in response to a transition from a connected state, in which the functional element 2 is mounted, to a disconnected state, in which the functional element 2 is removed. The element breakdown prevention circuit 10 decreases the impedance between the circuit terminals to a connected-state impedance in response to a connection state transition.
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