Common Fault and Removal Method of Medical Power Supply

Issue Time:2019-06-26
Common Fault and Removal Method of Medical Power Supply
一.The line failure
Line failure, including power line damage without power, contact point oxidation contact such as poor. Focus on checking whether the input line and the output line are energized.
If the line fails, it can be solved by replacing the power cord.

二.Low output voltage
The following are the main reasons for the output voltage pressure:
1, the medical power supply load short circuit failure(especially the DC/DC converter short circuit or poor performance, etc.), at this time, first disconnect all the load of the medical power supply circuit, check whether the switch power supply circuit failure or the load circuit failure. If the load circuit is disconnected and the voltage output is normal, it means that the load is too heavy; Or it is still not normal to indicate that the switch power supply circuit is malfunctioning.
2, the output voltage end filter capacitor or rectifier diode failure, etc., can be judged by the replacement method.
3, the performance of the switch tube decreases, resulting in the switch tube can not be normally turned on, so that the internal resistance of the power supply increases, and the load capacity decreases.
4, poor switching Transformers not only cause the output voltage to drop, and at the same time cause the switch tube insufficient excitation to damage the switch tube
5, 300V filter capacitance is poor, resulting in poor load capacity of the power supply band, and the output voltage will drop as soon as the load is connected.

三.High output voltage
High output voltage generally comes from voltage control sampling and voltage control circuits. In the closed control loop formed by DC output, sampling resistance, error sampling amplifier such as TL 431, optical coupling, power control chip and other circuits, any problem with any part will cause the output voltage to increase.
四.The insurance tube is normal, no output voltage
The safety tube is normal, and no output voltage indicates that the switch power supply is not working or is in a protective state. The first step is to check the value of the boot voltage of the boot of the power control chip. If there is no boot voltage or the boot voltage is too low, check whether the components and starting resistors of the boot foot leak.
If the power control chip is normal, the fault can be quickly found through the above monitoring. If there is a start voltage, it is measured whether the output of the control chip has a high or low level jump at the moment of boot. If there is no jump, it indicates that the control chip is damaged, the peripheral oscillation circuit element is damaged, or the protection circuit is malfunctioning. By replacing the control chip, checking the peripheral components, check one by one; If it is changing, most cases are bad or damaged for the switch tube.

五.Insurance burned or blown up
The main inspection of rectifier bridges, various diodes, switch tubes and 300 volts on the large filter capacitance and other parts. It may also be caused by problems with anti-interference circuits. In particular, it is worth noting that due to the safety burn caused by the breakdown of the switch tube, the power control chip and the current detection resistor are usually burned. Thermistors are also easily burned with insurance.

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