Constant voltage drive type driver circuit

A constant voltage drive type driver circuit includes a pulse transformer for outputting output pulses having a predetermined peak value and having primary and primary windings. The secondary winding has first and second terminals and an equivalent load impedance is connected to the secondary winding when viewed from the pulse transformer excluding an impedance of the secondary winding itself. A power source supplies a voltage, and a switching circuit supplies the voltage from the power source to the primary winding of the pulse transformer in a first mode and cuts off the supply of the voltage to the primary winding in a second mode in response to control signals. A short-circuiting part short-circuits the first and second terminals of the primary winding of the pulse transformer for a predetermined time from a time when the switching circuit assumes the second mode.