Bipolar DC-DC converter circuit diagram without inductor

Inverters Ula and Ul b form a 20kHz oscillator , and the square wave output of the oscillator (shaped by D2. R4 and R5 on the one hand, and D5. R6 and R7 on the other hand) drives the power field effect transistors Q2 and Q3. These two field effect transistors, P-channel and N-channel respectively, conduct alternately in a push-pull structure. When Q2 is turned on, the positive charge of Cout forces diode D4 to also turn on, thereby generating a positive voltage at terminal A determined by Zener diode D5. Likewise, when Q3 turns on, the negative charge on Cout forces D7 to turn on as well. Therefore, a negative voltage is generated at terminal B, and its level is determined by D6.