Signal transmission circuit and driving device for switching element

A signal transmission circuit, comprising:

• a transformer;
• a primary side circuit that:
• generates a pulse signal, for flowing a current in a primary side coil of the transformer in one direction when an input signal changing at a binary level indicates a first level, in a cycle shorter than a change cycle of the input signal;
• and
• generates another pulse signal, for flowing a current in the primary side coil in another direction opposite to the one direction during a period in which the input signal indicates a second level, in another cycle shorter than the change cycle of the input signal;
• and
• a secondary side circuit that:
• distinguishes the first level and the second level according to a voltage having a different polarity which is generated in a secondary side coil of the transformer;
• and
• reproduces the input signal, wherein:
• the primary side circuit includes:
• an oscillation circuit that outputs a clock signal having a cycle shorter than the change cycle of the input signal;
• an inverted signal output circuit that outputs an inverted signal in which the level of the input signal is inverted;
• a logic circuit that performs a gate control to output the clock signal only for the period in which the input signal indicates the second level;
• an H bridge circuit having a plurality of output terminals connected to both ends of the primary side coil respectively;
• a first on-state signal output circuit that outputs a first on-state signal to a switching element providing the H bridge circuit to generate the pulse signal for flowing the current in the primary side coil in the one direction by the H bridge circuit in synchronization with one change edge of the input signals;
• and
• a second on signal output circuit that outputs a second on-state signal to the switching element providing the H bridge circuit to generate the pulse signal for flowing the current in the primary side coil in the another direction opposite to the one direction by the H bridge circuit in synchronization with one change edge of the clock signal output through the logic circuit.