From traditional analog power supplies to efficient switching power supplies, the types and sizes of power supplies vary greatly. They all face complex and dynamic work environments. The equipment load and demand may undergo significant changes in an instant. Even a "daily" switching power supply must be able to withstand instantaneous peaks that far exceed its average operating level. Engineers who design power supplies or systems to use power supplies need to understand the operating conditions of the power supply under static and worst-case conditions.
For those accustomed to using an oscilloscope for high-bandwidth measurements, power measurement may be simple because its frequency is relatively low. In fact, there are also many challenges that high-speed circuit designers never have to face in power measurement.
The voltage of the entire switchgear may be high and floating, meaning it is not grounded. The pulse width, period, frequency, and duty cycle of the signal will all vary. It is necessary to capture and analyze the waveform truthfully and detect any abnormalities in the waveform. The requirements for oscilloscopes are demanding. Multiple probes - simultaneously requiring single ended probes, differential probes, and current probes. The instrument must have a large memory to provide recording space for long-term low-frequency acquisition results. And it may require capturing different signals with significant amplitude differences in one acquisition.
The mainstream DC power supply architecture in most modern systems is a switching power supply (SMPS), which is well-known for its ability to effectively cope with changing loads. The electrical signal path of a typical switching power supply includes passive components, active components, and magnetic components. Switching power supplies should minimize the use of lossy components such as resistors and linear transistors, and mainly use (ideally) lossless components such as switching transistors, capacitors, and magnetic components.
The switching power supply device also has a control part, which includes components such as pulse width modulation regulator, pulse frequency modulation regulator, and feedback loop 1. The control section may have its own power supply. Figure 1 is a simplified schematic diagram of a switching power supply, which shows the power conversion part, including active devices, passive devices, and magnetic components.
Switching power supply technology uses power semiconductor switching devices such as metal oxide field-effect transistors (MOSFETs) and insulated gate bipolar transistors (IGBTs). These devices have a short switching time and can withstand unstable voltage spikes. Equally important, they consume very little energy in both open and closed states, with high efficiency and low heat generation. Switching devices largely determine the overall performance of switching power supplies. The main measurements of switching devices include: switching loss, average power loss, safe working area, and others.
