Oscilloscope Power Supply Circuit

Power supply circuit: Supply negative high voltage, filament voltage, etc. required for vertical and horizontal amplification circuits, scanning and synchronization circuits, oscilloscope tubes, and control circuits.
From the principle and function of the oscilloscope, it can be seen that the measured signal voltage is applied to the Y-axis input terminal of the oscilloscope, and then applied to the vertical deflection plate of the oscilloscope tube through a vertical amplification circuit. The horizontal deflection voltage of the oscilloscope tube, although in most cases sawtooth voltage is used (for observing waveform), sometimes other applied voltages are also used (for measuring frequency, phase difference, etc.). Therefore, there is a horizontal signal selection switch at the input end of the horizontal amplification circuit to select the sawtooth voltage inside the oscilloscope as required, or select other voltages applied to the X-axis input end as the horizontal deflection voltage.

In addition, in order to maintain stability in the graphics displayed on the fluorescent screen, it is necessary to keep the frequency of the sawtooth voltage signal synchronized with the frequency of the measured signal. In this way, it is not only necessary to continuously adjust the frequency of the sawtooth voltage, but also to input a synchronization signal on the circuit that generates the sawtooth wave. In this way, for a simple oscilloscope (such as a domestic SB10 type oscilloscope) that can only generate a continuous scanning state (i.e., generating cyclic and continuous sawtooth waves), it is necessary to input a synchronous signal related to the frequency of the observed signal on its scanning circuit to control the oscillation frequency of the sawtooth wave. For oscilloscopes (such as domestic ST-16 oscilloscopes, SR-8 dual trace oscilloscopes, etc.) that have a waiting scan function (that is, they do not generate a sawtooth wave at ordinary times, but only generate a sawtooth wave when the measured signal arrives, and perform a scan), in order to meet various needs, the synchronization (or trigger) signal can be selected through the synchronization or trigger signal selection switch, usually from three sources:
① The measured signal is introduced from the vertical amplification circuit as a synchronization (or trigger) signal, which is called an "internal synchronization" (or "internal trigger") signal;
② Introducing a related external signal is a synchronization (or trigger) signal, which is called an "external synchronization" (or "external trigger") signal, and this signal is added to the external synchronization (or external trigger) input terminal;
③ Some oscilloscopes also have a "power synchronization" switch for synchronizing signal selection, which uses a 220V, 50Hz power supply voltage as a synchronizing signal after secondary voltage reduction through a transformer.