Micro-power DC-DC power modules are widely used in circuit design due to their high integration, high reliability, and simplified design. Although their application circuits are simple and easy to operate, some common problems are often encountered during application. This article provides a detailed analysis of the common application problems of power modules and how to troubleshoot them.
Micro-power DC-DC power modules are favored by many electronic designers due to their high integration, high reliability, and simplified design. Although the application circuits of power modules are simple and easy to operate, some common problems are often encountered during application. This article provides a detailed analysis of the common application problems of power modules and how to troubleshoot them, hoping to assist designers in selecting power modules.
Common Problem 1: Output Ripple Noise is Too High
Reason 1: The module is used with a dynamic load, causing the peak-to-peak output voltage of the module to increase, but note that this is not ripple noise.
When the load current has periodic fluctuations, the peak-to-peak output voltage of the module will increase. This is a transient quantity but can sometimes be mistaken for ripple noise. Therefore, when using a power module to supply multiple circuit units, for circuits with periodic load changes, it is necessary to add a π-type filter in the front stage to reduce the transient changes in this part of the circuit from interfering with other circuits.
For example, in the circuit below, circuit B experiences input voltage fluctuations due to changes in load size. To reduce the interference of circuit B on circuit A, it is recommended to add a π-type filter at the input of circuit B.
Figure 1 Circuit Link Block Diagram
Reason 2: Oscilloscope Ground Line Problem
When testing the ripple noise of the power output, the ground clip of the oscilloscope and the ground line form a loop with the module output pins, similar to an antenna receiver, which can introduce other noise. If the testing environment has a lot of interference, this noise can also be introduced by the oscilloscope, affecting the results of the ripple noise test.
Moreover, the ground of the oscilloscope probes we usually purchase is connected to the internal ground of the oscilloscope, which has weak anti-interference capabilities against power frequency interference and is prone to introduce interference noise. Therefore, it is best to ensure that the oscilloscope probe is floating (isolated from the oscilloscope power ground, or directly use a battery-powered oscilloscope) to reduce introduced interference. If the power supply of the measurement object is also floating, that is even better, as it will not cause changes in circuit characteristics, leading to an increase in module output noise.
Common Problem 2: Output Voltage is Low After Module Startup
Reason 1: There is a reverse polarity protection circuit at the input.
Figure 2 Module Reverse Polarity Protection Link Diagram
Example: The ZY_FKES-3W module in Figure 2 is a constant voltage input non-regulated output module, whose output voltage will change with the input voltage and load size. Since a reverse polarity protection diode is added on the input side during circuit design, this will lead to a reduction in the voltage at the module input, thus reducing the output voltage. When designing with a reverse polarity protection diode, we need to consider the forward voltage drop of the diode.
Reason 2: High Output Lead Impedance or Improper Voltage Meter Connection
Figure 3 Module Connection Diagram
When using the power module, we often test the output voltage directly at the input of the powered circuit for convenience. However, due to the high impedance between the module output and the powered circuit input, the measured value may be lower than the actual value. Therefore, when testing the output voltage of the power module, the voltage should be measured between the module output pins, not at the input of the powered circuit.
Reason 3: When using the module, the required power module power was not accurately estimated, causing the module to start or operate in an overloaded state.
For example, the ZY_FKES-3W constant voltage input non-regulated output power module has a rated power of 3W, meaning that the power used by the module cannot exceed 3W. When the ZY0505FKES-3W module is under 5V input and outputs 400mA, the output voltage is about 4.98V; at 600mA, the output voltage is about 4.88V. If overloaded, the output voltage will be even lower. As the load increases, the output voltage decreases, which is a characteristic of this constant voltage input non-regulated output module.
High-quality Isolated Power Modules Make Circuit Design More Efficient
Zhiyuan Electronics independently develops and produces isolated power modules with a wide input voltage range, isolation of 1000VDC, 1500VDC, and 3000VDC in multiple series, various packaging forms, compatible with international standards such as SIP and DIP, and can also provide customized services according to specific project needs, offering tailored features and special packaging for customers.
Zhiyuan power modules, with their high efficiency, wide input voltage range, small size, high reliability, shock resistance, and good isolation characteristics, are suitable for board-level power supply and are widely used in various fields such as power, industrial automation, communications, medical, transportation, building automation, instrumentation, and automotive electronics.
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