Easily solve common application problems DC-DC power module
Original title: easily solve common application problems DC-DC power module
Micro-power DC-DC power module with high integration, high reliability, simplify the design, multiple advantages, is widely used in circuit design. Although the application circuit is simple, simple, but often still encounter some common problems in the application. For this paper a detailed analysis of the application of the common power supply module and how to troubleshoot.
Micro-power DC-DC power module with high integration, high reliability, simplify the design, multiple advantages, favored by many electronic designers. Although the power supply module application circuit is simple, easy to operate, but often still encounter some common problems in the application. For this article, common application problems of power supply modules and how to troubleshoot a detailed analysis, I hope to help the designer's power supply module selection.
A common problem: too large output ripple noise
Reason 1: When using module, the load of the dynamic load, so that the module output peak voltage increases, but that this is not ripple noise.
When the load current is periodically if mutated, peak to peak output voltage of the module becomes large. This amount is a transient, but sometimes mistaken ripple noise. Therefore, when using a power supply module to a plurality of circuit units, for a cyclical load change circuit, the first stage is necessary to increase π-type filter, to reduce the transient part of this circuit the interference with other circuits.
For example, the circuit B of FIG. Since the size of the load change, so that the input voltage fluctuation. In order to reduce interference to the circuit A circuit B, the proposed increase in the π-type filter circuit B input.
A circuit block diagram of the link
Reason 2: The oscilloscope ground problem
When the test power supply output ripple noise, and ground clip to the oscilloscope, the output pin modules forming a loop antenna similar to the receiver may introduce additional noise. If the test of the big environmental interference, this noise will be introduced by the oscilloscope, the ripple effects of the results of noise tests.
And we usually buy oscilloscope probe with an internal earth line connected to the oscilloscope, immunity to frequency interference such cases weak, easy to introduce interference noise. In use, it is preferably treated to ensure that oscilloscope probe floating (isolated from power ground oscilloscope, or directly from the battery oscilloscope) to reduce the interference introduced. If the measurement object is a floating power supply, such better, so it will not lead to changes in circuit characteristics, so that the module output noise is increased.
Frequently Asked Question two: After the module starts, the output voltage is low
Reason 1: anti-reverse input terminal of the circuit
Figure 2 a block diagram of the module anti-reverse link
Example: in FIG. 2 ZY_FKES-3W constant pressure module unregulated input output module, the output voltage over input voltage and the magnitude of the load varies. Since the circuit design, at its input side of the anti-reverse diode increases, so that the module will cause the input voltage is lowered, so that the output voltage becomes small. Because we use in the design of anti-reverse diode, to consider the forward voltage drop of the diode.
Reason 2: Output lead impedance voltmeter is too large or non-standard connector
3 a block diagram of the connection module
When using the power supply module, we tested the output voltage, often directly testing the sake of convenience voltage is input to the power supply circuit. However, since the module is output to the impedance between the input terminal of the power supply circuit is too large, so that the measured value will be lower than the actual value. Therefore, when the output voltage of the test power supply module, the module should measure the voltage between the output pins, not being a supply voltage input circuit.
Cause 3: When the module is not accurately estimate the power required by the power module, the module to start overload or overload in the operating state.
For example, power module ZY_FKES-3W unregulated pressure input given output power rating of 3W, i.e., a power range module can not exceed 3W. ZY0505FKES-3W input module at 5V, 400mA output, the output voltage is approximately 4.98V; 600mA output, the output voltage is approximately 4.88V, if overloading, the output voltage will be lower. As the load increases, the output voltage will decrease, the constant pressure unregulated input output module characteristics.