MINMAX电源模块的应用

2011年03月24日 10:25来源：北京赛为达科技有限公司 >>进入该公司展台人气：2747

General Test Set-Up
Figure 1 shows a general equipment set-up for testing DC/DC converters. Except where otherwise required, the following conditions should be applied:

● Nominal DC input voltage
● +25°C ambient temperature
● Full rated output load

Measurements

All connections to the converters should be made with great care, especially to the output pins. Standard four-terminal or Kelvin, measurement practices should always be observed in making DC/DC converters measurements. Figure 2 shows a voltage measurement being made from the output terminals of a DC/DC converter by means of separate contacts that do not carry load current. If contacts carrying load current are used for measurement, an erroneous reading of many millivolts can be resulted.

Output Voltage Accuracy
Make and record the following measurements:

1.Output voltage at nominal input voltage （VON）.

Output Voltage Accuracy =	VO - VON	X *
	VON
VO is output voltage specified in the data sheet.

2.Output voltage accuracy is derived by the formula.

Line Regulation
Unregulated
Make and record the following measurements:

1.Output voltage at nominal input voltage （VON）.

Line Regulation =	VO - VD	X *
	VON
	?VIN%
VD is maximum output voltage deviation measured.

2.Output voltage at maximum input voltage （VOH）.

3.Output voltage at minimum input voltage （VOL）.

4.Line regulation is derived by the formula.

Regulated
Make and record the following measurements:

1.Output voltage at nominal input voltage （VON）.

Line Regulation =	VO - VD	X *
	VON

VD is maximum output voltage deviation measured.

2.Output voltage at maximum input voltage （VOH）.

3.Output voltage at minimum input voltage （VOL）.

4.Line regulation is derived by the formula.

Load Regulation
Make and record the following measurements:

1.Output voltage at full load （VOF）.

Load Regulation =	VOM - VOF	X *
	VOF

2.Output voltage at minimum load specified in the data sheet （VOM）.

3.Load regulation is derived by the formula.

Efficiency
Make and record the following measurements:

1.Output voltage at nominal input voltage （VON）.

Efficiency =	VON x IO	X *
	VIN x IIN

VIN is nominal input voltage and IO is output current.

2.Input Current at nominal input voltage （IIN）.

3.Efficiency is derived by the formula.

Output Ripple & Noise

This is an AC measurement at the output of a power converter at rated load and +25°C ambient temperature. The Measurement is made in either millivolts RMS or millimvolts peak-to-peak. Figure 3 shows the typical voltage waveform.

In the case of DC/DC converters, the output ripple voltage is a series of small pulses with high frequency content and for this reason, it is almost always specified as peak-to-peak rather than RMS value. A 50 millivolts peak-to-peak output ripple from a DC/DC converter can have a very low RMS value – perhaps just 5V – but this type of specification would be of questionable value to the designer who must specify the power supply for his system.

Because of the high frequency content of this ripple, special measurement techniques must be employed so that correct measurements are obtained. First, a 20MHz bandwidth oscilloscope is normally used for the measurement so that all significant harmonics of the ripple spikes are included.

The actual ripple voltage measurement must be carefully made in order not to induce error voltages in the test equipment. Therefore, the conventional ground clip on an oscilloscope probe （see Figure 4） should never be used in this type of measurement. This clip, when placed in a field of radiated high frequency energy, acts as an antenna or inductive pickup loop, creating an extraneous voltage that is not part of the output noise of the converter.

This noise pickup is eliminated as shown in Figure 5 by using a scope probe with an external ground band or ring and pressing this band directly against the output common terminal of the power converter while the tip contacts the voltage output terminal. This makes the shortest possible connection across the output terminals.

Another method of measuring the output voltage ripple & noise that is specified for many switching power supplies is shown in Figure 6. A 30cm twisted pair of no. 20 AWG copper wire is connected to a 10uF capacitor of proper polarity and voltage rating. The oscilloscope probe ground led should connect right to the ground ring of the probe and be as short as possible. The oscilloscope bandwidth should be at 20MHz and connected to AC ground.

上一篇：MINMAX 电源模块的应用

下一篇：安全阀的概念分类及选用技巧

全年征稿/资讯合作 联系邮箱：1271141964@qq.com

版权与免责声明

凡本网注明"来源：智能制造网"的所有作品，版权均属于智能制造网，转载请必须注明智能制造网，https://www.gkzhan.com。违反者本网将追究相关法律责任。
企业发布的公司新闻、技术文章、资料下载等内容，如涉及侵权、违规遭投诉的，一律由发布企业自行承担责任，本网有权删除内容并追溯责任。
本网转载并注明自其它来源的作品，目的在于传递更多信息，并不代表本网赞同其观点或证实其内容的真实性，不承担此类作品侵权行为的直接责任及连带责任。其他媒体、网站或个人从本网转载时，必须保留本网注明的作品来源，并自负版权等法律责任。
如涉及作品内容、版权等问题，请在作品发表之日起一周内与本网联系，否则视为放弃相关权利。