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The molecular beam epitaxy method (MBE method) is an important film preparation technology, which can realize two-dimensional layered growth, and can control the film thickness within the atomic single layer or subatomic single layer precision range, which can be used for preparation. Ultra-thin films such as GaN, AlGaAs and ZnO, which have clear mechanism in high-quality LED structure and their heterostructures, are currently used in the research field of LED chips.
The DC Power Module is an "industrial grade" design power supply that supplies power to the source furnace of the molecular beam epitaxy system and controls the temperature of the source furnace. Its performance stability is the preparation of high quality semiconductor thin films and their heterostructures. key. The overall system of the control power supply is a plate-type design with strict design, difficult control and complicated structure. The power supply consists of first and second EMI filtering (electromagnetic compatibility filter), rectification full bridge and filter circuit, main power switch tube, push stage transformer, standby power switch tube, anti-surge control circuit, standby power switch tube transformer, The main power switch tube transformer, pulse width modulator and power factor correction circuit, power factor correction circuit, push tube, main control IC, intelligent control microcontroller and rectification filter output circuit. When the power supply fails and cannot work normally, the fault point detection can be performed as follows.
1. Static detection [under power failure]: "Look, smell, ask, measure"
Look: Open the casing of the whole power supply, check whether the fuse is blown, whether there is component burning, wire burnout, device discoloration, whether the device is broken, whether the capacitor is deformed, whether the plug is loose, whether the plug is loose, etc. If the above structure or device is found to be abnormal, the components and peripheral circuit components should be inspected.
Smell: Smell the inside of the power supply for a smell.
Q: Consult the operator. The process of power supply damage is caused by the illegal operation of the power supply or natural damage.
Measurement: Use a multimeter to measure the quality of vulnerable components, such as: resistance between two or three stages, resistance of varistor, resistance of thermistor, resistance of IC to ground, capacitance of various types, Inductor value of transformer coil, power switch parameters of power MOSFET, resistance value of resistor, on/off of each connection line, etc. If the above structure and device are found to be abnormal, the component and peripheral circuit should be checked.
Second, dynamic detection [on power]: flow measurement, pressure measurement, frequency measurement, measurement efficiency
After the suspected point is removed by the above static detection, the power-on test can be performed.
Flow measurement: Each current meter is connected to the input and output terminals of the power system. When the system is powered up, check whether the input and output are normal.
Manometry: Measure the critical voltage values ​​in the circuit, such as the voltage across the high voltage capacitor. The voltage across the high-voltage filter capacitor is more than 300 volts, the operation needs attention; if the power supply has no output or the voltage output is unstable, this situation is mainly caused by the following reasons: open circuit, short circuit phenomenon, over voltage and overcurrent protection circuit in the power supply In case of failure, the oscillating circuit does not work, the power supply load is too heavy, the rectifier diode in the high-frequency rectification and filtering circuit is broken down, the filter capacitor is leaking, etc. The IC has no control function. If the power supply load capacity is poor, it usually appears in the old fashion or work. The main reason for the long time power supply is that the components have aging problems, cannot be repaired, or the operation of the switching transistor is unstable, and the heat is not released in time. Should focus on checking whether the Zener diode is hot and leaky, whether the rectifier diode is damaged, whether the high-voltage filter capacitor is damaged, whether the transistor operating point is selected, etc.; Zener diode clamping voltage; Measuring the high-frequency transformer primary and secondary coils with or without output voltage, if not, It is important to check whether the switch tube is damaged, whether it is oscillating, whether the protection circuit is operating, etc. If there is, it should focus on checking the rectifier diode, filter capacitor, three-way voltage regulator tube of each output; if the power supply starts, the power supply is at In the protection state, the voltage of the control chip protection input pin can be directly measured. If the voltage exceeds the specified value, the power supply is in the protection state, and the cause of the protection should be checked.
Unfinished
For more information, please refer to the October issue of "High-tech LED-Technology and Applications" 
Molecular beam epitaxy system source furnace control power supply fault point maintenance common method
[Source: "High-tech LED - Technology and Applications" October issue]