CN102158063A - Method for reducing voltage ripples - Google Patents
Method for reducing voltage ripples Download PDFInfo
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- CN102158063A CN102158063A CN2011100797072A CN201110079707A CN102158063A CN 102158063 A CN102158063 A CN 102158063A CN 2011100797072 A CN2011100797072 A CN 2011100797072A CN 201110079707 A CN201110079707 A CN 201110079707A CN 102158063 A CN102158063 A CN 102158063A
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- voltage ripples
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- 238000000034 method Methods 0.000 title claims abstract description 12
- 239000003990 capacitor Substances 0.000 claims abstract description 8
- 208000032365 Electromagnetic interference Diseases 0.000 abstract 2
- 238000013461 design Methods 0.000 description 5
- 238000010586 diagram Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000007792 addition Methods 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000004088 simulation Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
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Abstract
The invention provides a method for reducing voltage ripples. The method comprises the particular steps that a capacitor with resonance frequency of about 26MHz is added for reducing impedance, namely, one or more than one 47 nF capacitor is added in a range of smaller than 200mil close to a power pin 1 of a power chip U1, and voltage ripples are measured to be reduced to 69mV from the original 299mV and obviously improved by about 6 times after the 47 nF filter capacitors are added. By the way of simulating target impedance by frequency domain, a point with the problem of larger voltage ripples can be found, the problem can be solved, the voltage ripples can be reduced, and the quantity of power integrity can be improved, therefore, the quality of signal integrity is further improved and EMI (Electro-Magnetic Interference) is reduced.
Description
Technical field
The present invention relates generally to power supply integrality field, comprises that all is the chip of groundwork with high-speed computation, conversion of signals, storage.Such as: CPU, north and south bridge, SAS RAID card, network interface card or the like.These chips have the computing stored logic speed of last Gbps, and the high-frequency resistance of power supply is had higher requirement.
Background technology
At present, the continuous lifting of the speed of high speed signal, from the 2.5GHZ of Gen 1, the 5GHZ of Gen 2 has risen to the 8GHZ of PCIe Gen3 as the speed of PCIe bus; Usb bus has risen to the 5GHZ of USB3.0 from the 480MHZ of USB2.0 ... the importance of signal integrity has more and more caused electronic design engineering teacher's attention.
The design of power supply integrality is self-evident for the importance of signal integrity, and power quality is more little, and ripple is more little, and quality of signals will be guaranteed more.We design the final purpose that improves the power supply integrality also is in order to improve the integrality of signal.
The ripple of voltage is a crucial aspect for the power supply integrality.We will focus on a kind of method that reduces voltage ripple of research.
Summary of the invention
The purpose of this invention is to provide a kind of method that reduces voltage ripple.
The objective of the invention is to realize in the following manner, concrete steps are: force down impedance by increasing the electric capacity of resonance frequency about 26MHZ, promptly in the close scope of power pin 1 of power supply chip U1 less than 200mil, increase one or more 47nF electric capacity, be reduced to 69mV by measuring voltage ripple after increasing the 47nF filter capacitor by original 295mV, voltage ripple has had nearly 6 times obvious improvement.
The present invention reduces the excellent effect of ripple voltage method
Approach by the impedance of frequency domain simulation objectives can find voltage ripple problem points bigger than normal, deals with problems, and reduces ripple, has improved power supply integrality quality.So just can further improve the signal integrity quality, reduce EMI.The voltage ripple comparative parameter is as shown in the table.
Description of drawings
Fig. 1 illustrates the target impedance curve chart of voltage in the frequency domain;
Fig. 2 improves the voltage ripple circuit theory diagrams.
Embodiment
Explain below with reference to Figure of description method of the present invention being done.
Concrete steps are: force down impedance by increasing the electric capacity of resonance frequency about 26MHZ, promptly in the close scope of power pin 1 of power supply chip U1 less than 200mil, increase one or more 47nF electric capacity, be reduced to 69mV by measuring voltage ripple after increasing the 47nF filter capacitor by original 295mV, voltage ripple has had nearly 6 times obvious improvement.
Embodiment
We are when observing voltage ripple, and general all is the voltage waveform that measures a period of time by oscilloscope.When we measured the voltage waveform of a 1V in the laboratory, its ripple voltage has reached 295mV, and was as shown in table 1, obviously exceeds 5% voltage ripple standard.
Can find out more intuitively that from the waveform of time domain its voltage ripple is bigger, not meet our requirement quality of voltage.But we can not see problem points from its waveform, such as ripple is so greatly owing to what reason causes.This just need we by other means in other words method find problem points.
The target impedance (Target Impedance) of observing electric power network (Power Net) in the frequency domain is a method very effectively.We can't find problem points by the measurement waveform in time domain, but we can open-and-shutly see that the voltage ripple what reason causes is bigger than normal in frequency domain.
Fig. 1 uses target impedance curve in the frequency domain that the PowerSI software emulation of Sigrity company obtains for us.Curve A is the original design target impedance curve of P1V0.Can obviously find out its source impedance (impedance of higher frequency can be ignored for power supply) bigger than normal on the frequency about 26MHZ, and its target impedance is very little on the frequency about 1MHZ.
Like this, we just are easy to find ripple voltage problem of higher point, and the filter capacitor collocation that is its electric power network is smaller in the filter action that the frequency band of 26MHZ frequency rises.We just can suit the remedy to the case according to the source of problem, force down impedance by increasing the electric capacity of resonance frequency about 26MHZ.
Shown in the curve C of Fig. 1, for we near in the scope of power pin of chip U1 less than 200mil, add the target impedance curve behind the 47nF electric capacity (recording the resonance frequency of 47nF about 25MHZ) through the frequency impedance analyzer.As shown in Figure 2, C245, C257 47nF electric capacity for newly adding in the circuit theory diagrams after renewal, their point of additions on pcb board are the Bottom layer under U1 chip pcb board shown in the right figure of Fig. 2.By Fig. 1 curve C as can be seen the impedance of power supply about 26MHZ, had and declined to a great extent, as shown in table 1, added that the measuring voltage ripple is 69mV after the 47nF filter capacitor, voltage ripple has had nearly 6 times obvious improvement!
Remove to analyze ripple voltage if not the method for in frequency domain, watching target impedance, will compare blindly.As
Curve B shown in Figure 1 is to have added the target impedance that obtains behind the electric capacity of two 1uF in aforesaid same position, and it also makes moderate progress with respect to original design, but effect is not fairly obvious.Table 1 is that its corresponding voltage measures waveform.Its ripple is reduced to 188mV.
Emulation and test environment
Simulation software: Sigrity SpeedXP9.1 PowerSI
Oscilloscope: Tek DPO7054
Except that the described technical characterictic of specification, be the known technology of those skilled in the art.
Claims (1)
1. method that reduces voltage ripple, it is characterized in that, concrete steps are to force down impedance by increasing the electric capacity of resonance frequency about 26MHZ, promptly in the close scope of power pin 1 of power supply chip U1 less than 200mil, increase one or more 47nF electric capacity, be reduced to 69mV by measuring voltage ripple after increasing the 47nF filter capacitor by original 295mV, voltage ripple has had nearly 6 times obvious improvement.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2011100797072A CN102158063A (en) | 2011-03-31 | 2011-03-31 | Method for reducing voltage ripples |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2011100797072A CN102158063A (en) | 2011-03-31 | 2011-03-31 | Method for reducing voltage ripples |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN102158063A true CN102158063A (en) | 2011-08-17 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN2011100797072A Pending CN102158063A (en) | 2011-03-31 | 2011-03-31 | Method for reducing voltage ripples |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103488836A (en) * | 2013-09-26 | 2014-01-01 | 浪潮电子信息产业股份有限公司 | Design method to reduce PWM (pulse width modulation) noise interference |
| CN104102785A (en) * | 2014-07-22 | 2014-10-15 | 浪潮(北京)电子信息产业有限公司 | Method and device for reducing source synchronous switch noise |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1777745A2 (en) * | 2005-10-21 | 2007-04-25 | E.I.Du pont de nemours and company | Power core device including a capacitor and method of making thereof |
-
2011
- 2011-03-31 CN CN2011100797072A patent/CN102158063A/en active Pending
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1777745A2 (en) * | 2005-10-21 | 2007-04-25 | E.I.Du pont de nemours and company | Power core device including a capacitor and method of making thereof |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103488836A (en) * | 2013-09-26 | 2014-01-01 | 浪潮电子信息产业股份有限公司 | Design method to reduce PWM (pulse width modulation) noise interference |
| CN104102785A (en) * | 2014-07-22 | 2014-10-15 | 浪潮(北京)电子信息产业有限公司 | Method and device for reducing source synchronous switch noise |
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Application publication date: 20110817 |