In today's intelligent switch-mode power supplies, an internal microprocessor or DSP is commonly integrated for internal monitoring and communication purposes. The microprocessor chip demands a highly stable power supply with minimal amplitude fluctuations and absolutely no significant spikes, which can cause electromagnetic interference. Additionally, it requires the auxiliary power supply to have a broader AC adaptability than the rectifier's normal operating range. Aviation power supply
When the rectifier is connected to AC input power, the monitoring section must function properly first, performing self-checks and various status detections to determine if the rectifier can be powered on. In the event of extremely high or low AC voltages, although the rectifier has stopped working, the monitoring section must still operate normally, maintaining regular monitoring and communication. Certain power supply products have experienced unintended resets during operation. During the design of auxiliary power supplies for high-power switching power supplies, an analysis was conducted, revealing that the auxiliary power supply has many issues under different AC input voltages and load conditions: AC adaptability range, low load capacity, unstable and highly asymmetric working waveforms, magnetic bias, and severe electromagnetic interference. Generally, the working principle of the auxiliary power supply for a switching rectifier is: input AC power is rectified into high-voltage DC, then transformed by the circuit into low-voltage high-frequency square waves, and finally rectified and filtered by the circuit to become the stable low-voltage DC power required by the system. This is typically stabilized by a three-terminal voltage regulator and provided by a single DC output to supply the voltage feedback signal for the high-frequency transformation drive pulse control loop. The current feedback signal is taken from the main power conversion circuit by串联电阻 sampling, and the drive pulses for the power conversion tubes are generated by control chips like the UC3844 and their peripheral circuits. (Note: AC low voltage is the measured low input voltage when the auxiliary power supply starts to operate). 36V Aviation Power Supply
Under lower communication input voltages and without current feedback, the auxiliary transformer is unable to function properly. The pulse widths of its waveform are inconsistent, with some being wide and others narrow, and it experiences oscillations, making it impossible for the oscilloscope to stabilize the waveform. With current feedback, the pulse widths are also varied, with a duty cycle reaching 47%, while the UC3844's maximum duty cycle is only 50%. Increasing the load would lower the output voltage. Ensuring the auxiliary power supply can stabilize under both the upper and lower limits of AC input voltages, and that it can operate stably over the full range from no load to overload, presents significant challenges. This involves several technical difficulties: the voltage and overload capabilities of power devices; the design of high-frequency transformers; and the selection of parameters for the drive pulse control circuit. 400HZ Variable Frequency Power Supply
