Cause: The ripple is the output ripple of the power supply.

Solution: In practical application, there must be some filtering circuit between the two levels of power supply, you can refer to our technical manual. First confirm the working frequency of the power supply, and make clear whether the source of interference is the front-stage power supply or the rear-stage power supply module.

Reason: The reflected ripple to the front stage will be bigger when the relay is working.

Solution: It is recommended to do some filtering measures, or you can add Y capacitor between the ground of input and output.

Reason: Check the test method of ripple noise (parallel line test method or leaning test method), the oscilloscope bandwidth is set to 20MHz, and the large ripple noise at the input side may be the interference signal introduced at the input side of the module.

Solution: It is recommended to add a common mode inductor at the input of the module to filter out the interfering signals, and test the actual ripple noise of the module according to the parallel line test method or the leaning test method. If there is a requirement of smaller ripple noise, it is recommended to add a π-type filtering circuit to the output, or to add a Y capacitor at the input and output to suppress the common mode noise.

Answer: The customer's machine needs to pass the surge level 4, because K78T products have no internal surge protection circuit, it is necessary to add surge suppression devices or circuits such as varistors, TVS tubes, etc. in the front end of the power supply to reduce the surge voltage to the input voltage range.

Answer: Tantalum capacitors are easy to break down and short-circuit characteristics, poor surge resistance, may be due to a large instantaneous current leading to capacitance burnt and short circuit, or power on instantly generate a very high surge voltage, resulting in over-voltage breakdown of tantalum capacitors, modules in the application of the input side of the best not to connect tantalum capacitors. It is recommended to use ceramic capacitors or electrolytic capacitors for the input filter circuit. The output voltage of the module is very stable, the tantalum capacitor must be connected to the output side to ensure that the withstand voltage value is more than two times the output voltage.

Answer: Fixed-voltage products are open-loop, the output of positive and negative is only a relative value, by the wiring method to realize the negative voltage output there are two commonly used form:

a. The output labeled Vo, 0V is the output of the product itself, the output of positive, negative output; to get a negative output, as long as the circle labeled "the original output is changed to the output ground, the output of the ground is changed to a negative output can be"

b. The input ground, the output is connected to get a common ground, the original output ground has become a negative output. Note that at this time the product is no longer isolated and the noise becomes larger, the input and output must be added capacitance (capacitance value refer to the technical manual).

Reason: The electrostatic capacity of fixed-voltage products can reach 6-8KV of contact discharge, but since fixed-voltage products are secondary power supply, its volume is restricted and no special protection circuit is designed for other items of EMC.

Solution: If the customer's application environment has higher requirements for EMC, please refer to the recommended circuits in the technical manual to build relevant circuits in the periphery of the product.

Answer: The data acquisition signal on the output ripple noise requirements are relatively large, try to use a Y capacitor isolation module, or in the application of the module as far as possible in the input with a common-mode inductor to inhibit high-frequency interference, the output plus LC filter circuit to inhibit the signal interference of the back-end circuits.

Answer: Feasible, this is already our mature program. Use in series, add reverse bias diode and filter capacitor can be (refer to the application notes), but the ripple will become larger, the accuracy is reduced, it is recommended to add LC filter circuit at the output side to deal with.

Answer: The starting current of the module is generally about 1.4 to 1.6 times Iin-max, it is recommended to choose a slightly larger power preamplifier; the minimum input current is under no-load condition, refer to the indicator "no-load current" in the technical manual of the corresponding module.

Answer: The starting current of the module is generally about 1.4 to 1.6 times Iin-max, it is recommended to choose a slightly larger power preamplifier; the minimum input current is under no-load condition, refer to the indicator "no-load current" in the technical manual of the corresponding module.

Reason:

(1) Module load has a large capacitive resistance, start-up requires a large start-up current, high current shock damage to the module.

(2) Backfeeding at the output interferes with the input control system.

Solution:

(1) It is recommended to reduce the output capacitive load, according to the recommended capacitance in the technical manual.

(2) It is recommended to connect a diode to the output to prevent backfilling or connect an inductive filter circuit to the output to reduce the impact of backfilling.

Answer: In the output current is relatively large and the input and output voltage difference is large, the higher efficiency requirements do not require isolation of the occasion can choose K78 series products; K78 series and linear regulator compared to: small size, high efficiency, do not need an external heat sink, no-load power consumption is small, the input voltage range is relatively wide, the ripple noise is very low, K78XXT series output voltage is adjustable.

Answer: The output CS pin just plays a role of filtering, if the actual application of the ripple requirements are not high occasions can not be connected, but connected up to the output of the ripple noise has a certain suppression effect.

High voltage danger! Please take the necessary precautions! Production and commissioning employees must be trained before starting work!

Dangerous high voltage on the AC input side.

Protect against high voltage during production and commissioning!

Make sure that high voltage warnings are displayed at the production and commissioning sites!

Pay attention to the residual high voltage of the external capacitor after power failure during production and commissioning!