What is an oscilloscope power supply circuit
The power supply circuit supplies the negative high voltage and filament voltage required by the vertical and horizontal amplification circuits, the scanning and synchronisation circuits, as well as the oscilloscope and control circuits.
As seen in the block diagram of the oscilloscope principle and function, the measured signal voltage is added to the Y-axis input of the oscilloscope, and then added to the vertical deflection plate of the oscilloscope through the vertical amplification circuit. The horizontal deflection voltage of the oscilloscope tube, although most cases use the sawtooth voltage (used to observe the waveform), but sometimes also use other applied voltages (used to measure the frequency, phase difference, etc.), so there is a horizontal signal selection switch at the input of the horizontal amplifier circuit in order to select the oscilloscope's internal sawtooth voltage as needed, or select the X-axis input of other voltages added as the horizontal deflection voltage. voltage.
In addition, the frequency of the sawtooth voltage signal is required to be synchronised with the frequency of the measured signal in order to maintain the stability of the graph displayed on the fluorescent screen. Thus, not only is the frequency of the sawtooth voltage required to be continuously adjusted, but a synchronisation signal is also input to the circuit that generates the sawtooth wave. In this way, for can only produce continuous scanning (i.e., produce week after week, continuous sawtooth wave) a state of the simple oscilloscope (such as domestic SB10 type oscilloscope), the need to be observed in its scanning circuit on the input of a synchronisation signal with the frequency of the signal to be observed, in order to control the frequency of sawtooth wave oscillation. For a waiting scan function (i.e., usually do not produce a sawtooth wave, when the measured signal comes to produce a sawtooth wave, a scan) function of oscilloscopes (such as domestic ST-16 oscilloscopes, SR-8 dual-trace oscilloscopes, etc.), it is necessary to input a trigger signal related to the measured signal in its scanning circuit, so that the scanning process and the measured signal is closely coordinated. In order to adapt to various needs, the sync (or trigger) signal can be selected by the sync or trigger signal selector switch, and there are usually three sources:
① from the vertical amplifier circuit leads to the measured signal as the synchronisation (or trigger) signal, this signal is called "internal synchronisation" (or "internal trigger") signal;
② the introduction of a related external signal as a synchronous (or trigger) signal, this signal is called "external synchronous" (or "external trigger") signal, the signal is added to the external synchronous (or external trigger) input;
③ Some oscilloscopes have a synchronous signal selector switch and a "power supply synchronous", from 220V, 50Hz supply voltage, through the transformer secondary step-down as a synchronous signal.
