1. After the module is started, the output voltage is unstable or low.
1. The output lead impedance is too large or the voltmeter connection is not standardized.
Figure 1 module connection block diagram
When the customer uses the power module, the output voltage is tested and the voltage at the input of the power supply circuit is often tested. Since the impedance of the input of the module to the input of the powered circuit is too large, the measured value is lower than the actual value. Test the output voltage of the module and measure the voltage between the module's output pins.
When the module is checked into the warehouse, the voltage displayed on the electronic load meter is directly read. Special attention must be paid to the impedance of the module output wire and the contact of the cable.
2. When the customer uses the module, the required power module power is not accurately estimated, so that the module is overloaded or overloaded.
For example, the power rating of the E_UHBDD-10W power module is 10W, that is, the power range used by the module cannot exceed 10W. Otherwise, the module may not start properly or the output voltage may be low. It is recommended to switch to a larger power module or reduce the load.
Second, the module burned out
1, the input power polarity is reversed
When the power module is used, the power module is powered upside down and is easily burned out. There may be some modules that can output normally due to insufficient voltage or current. For this type of module, it is recommended not to use it (can be used to debug the product). If the power supply is reversed, it will affect the service life of the module.
2. The input voltage exceeds the normal input voltage range.
Figure 3 ZY_WRFCS-3W Series Power Module
The input voltage range of the product is given in the power module data sheet. Figure 4 shows the input surge voltage of the ZY_WRFCS-3W series module. When the instantaneous input voltage is higher than the maximum value, the FET inside the module and the diode withstand voltage exceed the rated withstand voltage and may burn out.
Figure 4 ZY_WRFCS-3W series input impulse voltage
3. When the module is in use, the wire between the power supply and the module is too long, which will make the inductance of the wire large. The switching characteristics of the switching power supply module cause current ripple at the input, which easily causes oscillation between the wire and the module. The long-term working module is severely heated and easily damaged.
5 power module connection block diagram
Third, the module can not start normally
1. It is recommended to add a certain filter capacitor to the output of the power module. Due to the lack of understanding, the capacitive load at the output of the module is too large, and the module starts poorly.
Figure 6 12 series module parameters in ZY_WRFCS-3W
The ZY1205WRFCS-3W module, by referring to the data sheet shown in Figure 6, suggests that the module's maximum output capacitance is 2200μF. It is recommended that the external output capacitor value of the module is not greater than the maximum capacitive load specified in the product manual.
Note: The LDO is added to the output of the module. The capacitive load after the LDO is also the capacitive load of the power module.
2. When the module is tested, the input power often limits the current to prevent the module from burning out. When the module is started with load, if the input power limit is not increased, the module will be started badly.
3. In the module application circuit, due to the difference in the startup time of the module, the subsequent circuit has a difference in power-on sequence. The circuit of the latter stage is powered on first, which may cause the transformer inside the module to be short-circuited, which may cause damage to the module. It is recommended to add a diode with a small on-voltage drop between the negative output of the module and the positive terminal of the output.
Fourth, the output ripple noise is large
1. When the module is in use, the load is a dynamic load, which makes the peak-to-peak value of the module output voltage become larger, which is no longer ripple noise.
Figure 7 Output voltage waveform of periodic variation of 50% to 75% load
As shown in Figure 7, the output voltage waveform of the E2405UHBD-20W module load current 50% to 75% load cyclically abrupt, this is not ripple noise. According to the product data sheet, this parameter is a transient response.
Ripple noise test also needs to pay attention to the test method. Commonly used test methods include relying on hair extension, parallel line test method, and twisted pair test method.
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