Electrical isolation device

1. An analog isolation device comprising a primary part having an input adapted to receive an input signal and a secondary part separated from the primary part by an electrical isolation barrier and having an output for delivering an output signal reproducing the input signal;

the primary part and the secondary part including a high-frequency channel having a low cut-off frequency and configured to receive the input signal in the primary part and to produce a high-frequency component in the secondary part from the input signal, and a low-frequency channel having a high cut-off frequency and configured to receive the input signal in the primary part and to produce a low-frequency component in the secondary part from the input signal, in order to form the output signal from the high-frequency and low-frequency components;

the device being characterized by a control circuit configured to receive, in the primary part, a setpoint signal representative of the input signal and a so-called image signal representative of the output signal, and to apply in the high-frequency and/or low-frequency channel a correction signal as a function of the difference between the image signal and the setpoint signal in order to cause that difference to tend towards zero.

2. A device according to claim 1 , characterized in that the correction signal is applied only to the low-frequency channel.

3. A device according to claim 1 , characterized in that the correction signal is applied only to the high-frequency channel.

4. A device according to claim 1 , characterized in that the primary part comprises a summing element adapted to produce the image signal by summing a first signal representative of said low-frequency component and a second signal representative of said high-frequency component.

5. A device according to claim 4 , characterized in that the first signal and the second signal are in the form of currents.

6. A device according to claim 4 , characterized in that the first signal and the second signal are in the form of voltages.

7. A device according to claim 4 , characterized in that the low-frequency channel comprises an electro-optical coupler forming part of the electrical isolation barrier and having an electro-optical emitter, a first opto-electrical receiver situated in the secondary part and coupled to the emitter to produce a current enabling of said low-frequency component to be generated, and a second opto-electrical receiver situated in the primary part and coupled to the emitter to produce a current enabling said first signal representative of said low-frequency component to be generated.

8. A device according to claim 7 , characterized in that the low-frequency channel comprises, in the primary part, a linearization circuit for linearization of the opto-coupler connected to the electro-optical emitter.

9. A device according to claim 8 , characterized in that the correction signal is applied to the linearization circuit.

10. A device according to claim 4 , characterized in that the high-frequency channel includes a transformer forming part of the electrical isolation barrier and having a primary situated in the primary part and a secondary situated in the secondary part to obtain said high-frequency component from a voltage taken from the secondary of the transformer and to obtain said second signal representative of said high-frequency component from a voltage taken from the primary of the transformer.

11. A device according to claim 10 , characterized in that the correction signal is in the form of a voltage applied to the primary of the transformer.

12. A device according to claim 1 , characterized in that the control circuit has a high cut-off frequency at least 100 times greater than the low cut-off frequency of the high-frequency channel.

13. An electrical measuring instrument provided with an analog isolation device according to claim 1 .