For the convenience of analysis, Q1 on the left is called A and Q1 on the right is called B. When an uncertain factor (usually a noise factor) causes the base voltage of A to rise, it will cause the collector voltage of A to drop, which is coupled to the base of B by the capacitor C1. The base voltage of B drops, causing the collector voltage of B to drop. The voltage rises, and the voltage is coupled back to the base of A through left C1, further intensifying the conduction of A, and soon A enters a saturated conduction state. At this time, the two capacitors C1 are in charging and discharging states respectively. The charging process of the left C1 is: right R1 - left C1 - BE junction of A - negative electrode of the battery; the discharging process of the right C1 is: right C1 - A CE junction - battery negative - B's BE junction - right C1. As the left C1 is fully charged, the base voltage of B slowly increases, the BE junction current of B gradually increases, and the collector voltage of B decreases. This voltage is coupled to the base of A by the left C1, and is redirected The opposite process in the first half of the cycle, and the left C1 enters the charging state, and so on, the square wave oscillation signal is continuously output. This is its oscillation principle.

If you change the input DC12V to 24V and do not want to change the transformer, you can only change the pulse width. That is, changing the "duty cycle" can be done at the base of the two Q2 and the two This is achieved by adding an integrating circuit consisting of a resistor and a capacitor between the collectors of Q1, and then adding a level of shaping amplifier circuit. However, the increase in voltage will inevitably change the original oscillation frequency. The circuit modified in this way will produce a higher harmonic voltage. When the power supply output is no-load, there may be a high floating voltage. It is recommended to add a damping resistor during use.

Replacing the transformer and adjusting the bias resistor can also adjust the input voltage requirements, but it is very troublesome and is not recommended.

The transformation ratio of the transformer is: primary voltage to primary coil turns = secondary voltage to secondary coil turns. You can adjust it by yourself according to this formula. However, due to the limitation of the magnetic permeability of the transformer core, if you use ordinary silicon steel sheets, it is recommended to set the voltage drop per turn to 0.2V.

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