Constant voltage drive type driver circuit

A constant voltage drive type driver circuit includes a pulse transformer (10) for outputting output pulses having a predetermined peak value and having primary and secondary windings (L1, L2), where the secondary winding (L2) has first and second terminals (101, 102) and an equivalent load impedance (RL) is connected to the primary winding (L1) when viewed from the pulse transformer excluding an impedance of the primary winding itself, a power source (6, 7) for supplying a voltage, a switching circuit (20) for supplying the voltage from the power source to the secondary winding of the pulse transformer in a first mode and for cutting off the supply of the voltage to the secondary winding in a second mode in response to control signals (A, B), and a short-circuiting part (30) for short-circuiting the first and second terminals of the secondary winding of the pulse transformer for a predetermined time from a time when the switching circuit assumes the second mode.