U1 is a 4060 12-stage binary ripple counter that is used as a free-running oscillator; its frequency of oscillation is: 1/2.2 CIR2. The output of U1 is applied to U2, a 14-stage binary ripple counter that provides square-wave outputs of lfz, 1/4, `is, and `lls of the clock frequency. These signals are combined in U3 and U4 to provide a complementary drive for Q1 and Q2.
Outputs from U3 and U4 are ac-coupled to Q1 and Q2 via C2 and C4, respectively. R3 and R4 adjust tbe gate drive to Q1 and Q2. Q1 and Q2 alternately draw current through opposing sides of the primary to synthesize an ac input voltage at a given frequency. Only one side of the primary of T2 is driven at one time, so maximum power output is half of the transformer rating.