| 摘要 |
A controllable circuit (10) having protection against damaging switching conditions for its component transistors (12) is described. The circuit (10) is a full-wave inverter bridge being controlled by a pulse width modulation technique, to which is connected an inductive load (50) and a resonant circuit (30). The circuit (10) also comprises snubber circuit (18) and free-wheeling diodes (14) associated with each transistor (12). The transistors (12) are switched between on-states and off-states to synthesize a pulse width modulation waveform from input supplies Vs<+> and Vs<-> at the output terminals VA and VB. The elements of the resonant circuit (30) provide for placing the transistors (12) in an advantageous condition for switching between states, such that they do not experience undue damage or stresses. The method of operation includes switching-on one of the controllable transistors (22) to provide an alternative path for the load current, IL, thereby forming a resonant circuit by two capacitors (20), the inductor LC and the load. In this way, there is control over the rate of rise of the off-state voltage, dv/dt, and the rate of rise of on-state current, di/dt, and minimization of the static off-state voltage all with respect to the transistors (12). The diodes (24) provide blocking in respective opposite half cycles. |
