Три Приклади З Комутація Живлення Живлення Несправності Інвертор
The 2844 chip is powered on separately, there is no pulse at pin 6, and the voltages at pins 1, 2, and 3 are all normal. The voltage of pin 4 is 1.8V, and there is no sawtooth wave pulse at pin 4 measured by the oscilloscope; the former repairer replaced four chips in a row. Measure the resistance of 4 feet to the ground, it is obviously too small, and other circuits are more than ten thousand ohms. The machine is about 3 thousand ohms. Remove the chip and the peripheral components of the chip, make the 4 pins floating, and measure the resistance value to the ground as 9 kohms, which is not infinite. Obviously, the 4-pin via hole or the copper foil has a leakage point to the 5-pin ground point. At this time, try to apply a 30V DC voltage between the 4 pins and the ground, and the displayed current value is tens of milliamperes and is getting smaller and smaller. When the power is off when it is as small as a few milliamperes, then measure the resistance of the 4 pins to the ground, and it becomes 60 kohms. above. Restore the chip and 4-pin components, and eliminate the power-on fault.
Two examples:
Складно до вібрації. Після чіп і те магістраль схема є живлення увімкнено разом, the виміряний вихід of plus 15V after живлення is 11V, і the output of 24V is 19V, both which are low. the oscillograph measures the duty cycle of the 7b{4}}pin pulse, which is small. Analyz the reason, the output pulse duty cycle is small, which is related to the state of pin 1 and pin 3. pins 1 and 2 are connected to pins 3 and 4 of the feedback optocoupler, and there is no problem in checking the voltage regulator circuit. There is an 18V Zener diode connected between pin 3 and pin 7. After removing it, the fault is elivened.
If the output voltage is low, if it is not insufficient self-power supply, it is the cause of voltage regulation miscontrol or overcurrent. This example is the latter.
Три приклади:
Комутація живлення живлення, чіп увімкнення і основна схема увімкнення, робота нормальна, і робота нормально після видалення чіп живлення живлення. Перевірте що там є немає навантаження коротка схема, і вимикач трубка has no температура підвищення. The причина of недостатня власна потужність supply can be ruled out. That is, the power-on excitation ability is is insufficient, and there is no change after reducing the starting resistance. Still 5, 7 pin живлення живлення або збудження проблема. очевидно, it contains the internal circuit of pins 5 and 7 of the chip.
Після зміна чіп це працює добре.
