Self-oscillating resonant push-pull converter with a synchronous rectifier for phase-modulated bidirectional communication

A communication system for bidirectional galvanically isolated communication, comprising:

• a DC/DC converter circuit, including:
• a push-pull driver to which a reference clock with a fixed frequency can be applied on an input side;
• a transformer having a primary coil and a secondary coil, wherein the push-pull driver is connected, on an output side, to the primary coil;
• a synchronous rectifier connected, on an AC side, to the secondary coil;
• a resonant circuit including a capacitance and one inductance, the resonant circuit being designed such that a part of the resonant circuit is on a primary side of the transformer and another part of the resonant circuit is on a secondary side of the transformer;
• a decoupling inductance connected on a secondary side of the transformer and downstream of the synchronous rectifier and which is not part of the resonant circuit;
• and
• an output capacitance connected in series with the decoupling inductance and via which an output voltage is provided,
• wherein the DC/DC converter circuit has a first galvanic isolation by virtue of the transformer and provides the output voltage for power supply on the secondary side of the transformer;
• a transmitting transfer channel having a first modulator unit connected for data transfer to a first demodulator unit via a second galvanic isolation;
• and
• a receiving transfer channel having a second demodulator unit connected to a second modulator unit via a third galvanic isolation,
• wherein, for the modulation units and demodulation units, the DC/DC converter circuit also provides, on the primary side and the secondary side, the reference clock required for modulation and demodulation.

An automation field device for use in an explosive atmosphere, including in an Ex-ia and/or Ex-d area, comprising:

• a communication system for bidirectional galvanically isolated communication, including:
• a DC/DC converter circuit, including:
• a push-pull driver to which a reference clock with a fixed frequency can be applied on an input side;
• a transformer having a primary coil and a secondary coil, wherein the push-pull driver is connected, on an output side, to the primary coil;
• a synchronous rectifier connected, on an AC side, to the secondary coil;
• a resonant circuit including a capacitance and one inductance, the resonant circuit being designed such that a part of the resonant circuit is on a primary side of the transformer and another part of the resonant circuit is on a secondary side of the transformer;
• a decoupling inductance connected on a secondary side of the transformer and downstream of the synchronous rectifier and which is not part of the resonant circuit;
• and
• an output capacitance connected in series with the decoupling inductance and via which an output voltage is provided,
• wherein the DC/DC converter circuit has a first galvanic isolation by virtue of the transformer and provides the output voltage for power supply on the secondary side of the transformer;
• a transmitting transfer channel having a first modulator unit connected for data transfer to a first demodulator unit via a second galvanic isolation;
• and
• a receiving transfer channel having a second demodulator unit connected to a second modulator unit via a third galvanic isolation,
• wherein, for the modulation units and demodulation units, the DC/DC converter circuit also provides, on the primary side and the secondary side, the reference clock required for modulation and demodulation;
• and
• main electronics and sensor electronics,
• wherein the sensor electronics are galvanically isolated from the main electronics, and
• wherein the main electronics are connected, for data transfer, to the sensor electronics via the communication system.