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Common faults and troubleshooting methods for medical power supplies
Issue Time:2019-07-03
Common faults and troubleshooting methods for medical power supplies

一.The line is faulty
Line faults, including power cord damage, non-energization, poor contact contact oxidation, etc. Focus on checking whether the input and output lines are powered.

If the line is faulty, you can solve it by replacing the power cord.

二.The output voltage is too low
The following are the main reasons for the low output voltage:

1. Medical power load short-circuit fault (especially short circuit or poor performance of DC/DC converter). At this time, first disconnect all the load of the medical power supply circuit, check whether the switching power supply circuit is faulty or the load circuit is faulty. 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, indicating that the switching power supply circuit is faulty.

2. The output voltage terminal filter capacitor or rectifier diode is invalid, etc., which can be judged by the replacement method.

3. The performance of the switch tube is degraded, which causes the switch tube to fail to conduct normally, which increases the internal resistance of the power supply and reduces the load capacity.

4. The switching transformer is not good, which not only causes the output voltage to drop, but also causes the switching tube to be insufficiently excited to damage the switching tube.

5, 300V filter capacitor is poor, resulting in poor power supply load capacity, the load output voltage will drop when connected.

三.The output voltage is too high
The output voltage is too high and generally comes from the regulated sampling and voltage regulation control circuit. In the closed control loop formed by DC output, sampling resistor, error sampling amplifier such as TL431, optocoupler, power control chip and other circuits, any one of the parts will cause the output voltage to rise.

四.The fuse is normal, no output voltage
The fuse is normal and no output voltage indicates that the switching power supply is not working or has entered the protection state. The first step is to check the value of the starting voltage of the start pin of the power control chip. If there is no starting voltage or the starting voltage is too low, check whether the external components of the starting pin and the starting resistor are leaking.

If the power control chip is normal, the fault can be quickly detected through the above monitoring. If there is a starting voltage, whether the output of the control chip has a high or low transition at the instant of power-on, if there is no jump, it indicates that the control chip is damaged, the peripheral oscillating circuit component is damaged or the protection circuit is faulty, and the control is replaced by The chip, check the peripheral components, check one by one; if it is a jump, in most cases, the switch is defective or damaged.

五.Insurance burns or blows up
Mainly check the rectifier bridge, each diode, switch tube and large filter capacitors on 300 volts. This may cause the insurance to burn and blacken, or it may be caused by a problem with the anti-interference circuit. It is particularly noteworthy that the power supply control chip and the current sense resistor are usually burned out due to the breakdown of the switch tube. The thermistor is also easily burned out together with the insurance.

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