Linear D.C. drive circuit

Apparatus for driving a d.c. load from a sinusoidal a.c. source in accordance with a d.c. control signal comprising:

• a transformer for coupling energy from said a.c. source to the load;
• pulse width modulating means including means to produce a sinusoidal signal in quadrature with a signal from said a.c. source, means to produce first and second offset signals equal to the instantaneous sum and difference, respectively, of said quadrature and said d.c. control signals, means to produce a variable duration d.c. voltage when and only when said first and second offset signals are of opposite polarity with respect to the zero axis of said quadrature signal;
• switching means including forward and reverse transistor means connected to pass energizing current from said transformer through said load in forward and reverse directions, respectively;
• and
• steering means for applying said variable duration d.c. voltages to said forward transistor means in response to a d.c. control signal of one polarity and to said reverse transistor means in response to a d.c. control signal of the opposite polarity;
• said forward and reverse transistor means being constructed and arranged to saturate throughout the occurrence of an applied variable duration d.c. voltage.