What should I do if the ripple measurement method is constant voltage constant current power supply?
2021-03-07 10:20:39
Ripple refers to the fluctuation of the output capacitor voltage caused by the current flowing through the inductor and capacitor when the constant voltage and constant current power supply is output. This fluctuation is related to the capacity of the output capacitor, the equivalent series resistance, and the frequency of the power supply.
Ripple (invasion and deletion of network diagram)
Measuring method of constant voltage constant current power supply ripple
To objectively measure the ripple-noise output of the constant voltage and constant current power supply, the bandwidth of the oscilloscope must be limited to 20MHz. To ensure that the probe ground is as short as possible, it is recommended to use the original test short pin (too long the ground wire will cause the measurement ripple to be high), and Hang the oscilloscope ground, do not share the ground with other test equipment.
Oscilloscope (invasion and deletion of network diagram)
Method for restraining ripple of constant voltage constant current power supply
Ripple is caused by the switch of the switch tube, so it cannot be completely removed, it can only be suppressed. Several methods for suppressing the ripple of the constant voltage and constant current power supply are summarized below.
PCB design: PCB distribution parameters will lead to adjustment errors or poor filter efficiency. The sampling circuit and filter circuit should be as close as possible to the switching power supply IC, and the traces should not be too long or too thin.
Increase the inductance and output capacitor filtering: the relationship between the ripple and capacitance of the constant voltage and current output is vripple = Imax / (Co × f), so increasing the output capacitor value can reduce the ripple to a certain extent.
Parallel or series resistance capacitance (filter) in the output loop: The ripple frequency characteristic is obtained through calculation, and the precise resistance and capacitance values ​​are selected in parallel or in series in the output loop of the constant voltage and constant current power supply, which can also effectively suppress the ripple Wave, but when the capacitor or resistor fails, it is very likely that new ripple or noise will be mixed, which will increase the output ripple.
Heat dissipation structure of constant voltage constant current power supply
Due to its own structure, the generation of ripple cannot be avoided because of its own structure. Different application environments have different requirements for each parameter of the power supply. Various ripple suppression methods have their own advantages and disadvantages. Consider options comprehensively.
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