The power source module is may paste directly installs the power source supply (refers to Figure on the printed wiring board 1), its characteristic is may for the specific IC (ASIC), digital signal processor (DSP), the microprocessor, the memory, scene programmable gate array (FPGA) and other digit or the fictitious load provides the power supply. Generally speaking, this kind of module is called the loading point (POL) power source supply system or application point power source supply system (PUPS). Because module type structure merit very many, therefore systems and so on high performance telecommunication, network relation and data communication widely use each kind of module. Although uses the module to have many merits, but engineer designs when the power source module on the majority of boards directs current/the direct-current switch, often neglects reliable and the survey aspect question. This article will penetrate discusses these questions, and proposes the related solution separately.
Figure 1, power source supply
Uses the power source module the merit
At present the different supplier promotes many kinds of different power source modules in the market, but the different product’s input voltage, the output, the function and topology and so on have nothing in common. Uses the power source module to be possible to save the development time, enables the product to be possible to promote the market quickly, therefore the power source module is more superior than the integration-like solution. Below the power source module also has many merits:
* each module may perform the strict test separately, guaranteed that it is highly reliable, including the circular telegram test, with the aim of rejecting the product which is not up to standard. Comparatively speaking, the integration-like solution is then difficult to test, because on entire power supply system and circuit’s other functional system close relation same place.
* the different supplier may defer to the existing technical standard design identical size the module, to design the power source supply engineer provides many kinds of different choices.
* each module’s design and the test defer to the standard performance the stipulation to carry on, are helpful to reduce use the risk which the new technology withstands.
* if uses the integration-like solution, once the power source supply system has the problem, then needs to put in order the block motherboard replacement; If uses the module-like design, so long as the question module replacement then may, be helpful to save like the cost and the development time.
Easily the power source module design question which neglects
Although uses the module-like design to have the above many merits, down to but the module type design on the board directs current/the direct-current switch design also has the question, many people these question understanding insufficiency, or do not give the enough value. The following is partial questions:
* output noise survey;
* magnetic system’s design;
* synchronized voltage dropping switch’s puncture phenomenon;
* printed wiring board reliability.
These questions 11 will discuss in as follows, meanwhile will introduce that many kinds of may solve these question simple technology.
Output noise measuring technique
All uses the switch pattern the power source supply to be able to output the noise. The turn-on frequency is higher, then more needs to use the correct measuring technique, guaranteed measures data accurate reliable. When measurement output noise and other important data, may use Tektronix which shown in Figure 2 the probe probe head (to be called cold spray nozzle probe head generally), guarantees the survey digit accurately reliable, moreover conforms to the forecast. This kind of measuring technique also guaranteed that the ground loop may reduce to is smallest.
Figure 2, survey output noise digit
Carries on when the survey we must possibly appear the measuring instrument the propagation delay this factor computation. The majority of current probe’s propagation delay is bigger than the voltage probe head. Must therefore simultaneously demonstrate that the voltage and current waveform’s survey is then unable to guarantee the survey digit the accuracy, only if using manpower different detention balanced.
The current probe also the inductance input circuit. The typical current probe can input 600nH the inductance. Regarding the high frequency circuit design, because the electric circuit may withstand the inductance cannot surpass 1mH, therefore, will affect the di/dt current measurement by way of the probe head input’s inductance the accuracy, even the command will survey the digit to present the very big error. If the inductor has been saturated, then may use another more accurate method survey amperage, for example, we may survey and the inductor serial together small shunt resistance voltage.
Magnetism design
Whether the magnetic core reliable is another frequently the question which is neglected by the human. The majority outputs the inductor to use the powdered iron magnetic core, because the powdered iron is the cost lowest material. In the powdered iron magnetic core’s ingredient probably some 95% are the ferrite grain, but these hard silt use organic binding agent agglutination same place. These binding agents also each hard silt separation, cause inside and outside the magnetic core the full cloth ventilation space.
The powdered iron constitutes the magnetic core raw material, but the powdered iron includes the small amount impurity like manganese and the chromium, but these impurities can affect the magnetic core the reliability, the influence to regard contains the impurity quantity. We may use the spectrum electron microscope (SEM) careful examination magnetic core the section, with the aim of determining the impurity the relatively distributed situation. The magnetic core is whether reliable, the key lies in the material whether can forecast as well as it supplies whether stable reliable.
If the powdered iron magnetic core is in for a long time the high temperature environment, the core loss will possibly increase, will lose, once will increase, then forever will be unable to recover, because the organic binding agent will present the individual contribution to decompose, is increased the eddy current loss. This kind of phenomenon may be called the thermosenescence, finally will possibly bring about the magnetic core to appear loses control hotly.
Core loss’s size is exchanged the electric induction, the operating frequency, the magnetic core size and the material category and so on many different factor influences. As regularly said take the high frequency operation that the majority of losses are the eddy current loss. If by the low frequency operation, the hysteresis loss instead is the biggest loss.
The eddy current loss make the magnetic core heating, so that the efficiency will also receive affects falls. The turbulization loses the reason is the object which creates by the ferromagnetic material is made the different time different magnetic flux influence the electric current which in the object produces moves in endless cycles. So long as we select ferromagnetic thin slice a piece by piece, but must honestly the ferromagnetic achievement magnetic core’s material, then may decrease the eddy current loss. For example, Metglas which circles by the magnetic tape is such one kind of magnetic core. Other ferromagnetic product supplier like Magnetics also produces the magnetic core which circles by the magnetic tape.
Magnetic core product suppliers and so on Micrometals provide the newest material which and the computing mode specially for design magnetic product’s engineer the related magnetic core heating gets older. Will use the inorganic binding agent the powdered iron magnetic core not to have the situation which the heating will get older to appear. In the market had this kind of magnetic core sell, the Micrometals 200C series magnetic core then belongs to this kind of product.
Synchronized voltage dropping switch’s puncture phenomenon
Loading point power source supply system (POL) or power supply systems and so on application point power source supply system (PUPS) widely use the synchronized voltage dropping switch (Figure 3). This kind of synchronized voltage dropping switch uses the high-end and the low end MOSFET substitution tradition voltage dropping switch’s clamping diode, with the aim of reducing the load current the loss.
Figure 3, synchronized voltage dropping switch
Engineer designs when the voltage dropping switch neglects “the puncture” frequently question. When the high-end and carries at the same time lowly MOSFET comprehensive or the partial start, will then present “the puncture” the phenomenon, will enable the input voltage to be possible to transport directly the electric current the earth.
The puncture phenomenon will cause the electric current to present the peak in switch’s flash, is unable the switch to display its maximum efficiency. We cannot use the current probe survey puncture the situation, because probe head’s inductance will disturb electric circuit’s operation seriously. We may inspect two field effect transistor (FET) the gate extremely/source voltage, has a look whether to have the peak to appear. This is another examination puncture phenomenon method. (the upper formation MOSFET gate/source voltage may monitor extremely using difference way.)
We may use the following method reduction puncture phenomenon the appearance.
Uses is equipped with “the fixed dead time” the controller chip is feasible means. This kind of controller chip may guarantee after upper formation MOSFET closure, will present a section of delay time, only will then let lower level MOSFET start. This method is simpler, but implements truly time must be very careful. If the dead time is too short, possibly is unable to prevent to penetrate the phenomenon the appearance. If the dead time is too long, the electric conductance will lose will then increase, because the first floor field effect transistor built-in diode has been starting in the entire section dead time. Because this diode in the dead time the electric conduction, will therefore use this method the system efficiency to be then decided by the first floor MOSFET built-in diode’s characteristic.
Another reduced puncture’s method is uses is equipped with “the auto-adapted dead time” the controller chip. This method’s merit is may monitor upper formation MOSFET unceasingly the gate extremely/source voltage, with the aim of determining He Shi only then starts first floor MOSFET.
When high-end MOSFET start, will lower through the inductance induction command carries MOSFET the gate to present the dv/dt peak extremely, so that will push the wealthy and prominent family pole tension (Figure 4). If gate/source voltage Gao Zhi start, the puncture phenomenon will then appear extremely the sufficiently.
Figure 4, appears is carrying MOSFET lowly the dv/dt induced level oscillation amplitude
The auto-adapted dead time controller is responsible in outside to monitor MOSFET the gate pole tension. Therefore, any new Canada’s outside sets at the gate resistance to be able to divide extremely goes to the controller built-under to pull the resistance the partial voltages, so that the gate pole tension the voltage which will monitor the controller will be in fact higher.
The forecasting gate actuation is extremely another feasible plan, the means is retards using the digit feedback circuit examination built-in diode’s electric conduction situation as well as the adjustment dead time, in order to reduces to few built-in diode’s electric conduction, guaranteed that the system may display the maximum efficiency. If uses this method, the controller chip needs to increase more pins, so that the chip and the power source module’s cost will increase.
Some point needs to pay attention, even if uses the forecasting gate to actuate extremely, is also unable to guarantee the field effect transistor not to be able, because the dv/dt inductance induces starts.
The detention high-end MOSFET start is also helpful to reduce the puncture situation to appear. Although this method may reduce or eliminate the puncture phenomenon thoroughly, but the shortcoming is the switching loss is high, but the efficiency will also drop. If we select good MOSFET, is also helpful to reduce appears in first floor MOSFET the gate dv/dt inductance voltage amplitude extremely. Between Cgs and the Cgd ratio is higher, on presents the inductance voltage in the MOSFET gate to be then lower extremely.
The puncture test situation is neglected frequently by the human, when for example - - the load has relieved or reduces suddenly - the air-operated controller in the load transient process to produce the narrowband pulse unceasingly particularly. At present are majority of the high electric current system to use the leggy design, actuates MOSFET using the driver chip. But will use the driver chip command to penetrate the question to be more complex, when particularly the load will be in the transient process. For example, the narrowband drive pulse’s disturbance, in addition the driver presents the propagation delay, can cause the puncture situation the appearance.
The majority of driver chip producers special regulation controller’s pulse width must not be possible to be lower than some lowest request, if is lower than this lowest request, will then not have the pulse input MOSFET gate extremely.
In addition, the producer also supposes for driver chip other Canada may establish dead time (TRT) the function, strengthens the auto-adapted transformation accuracy fixed time. The means are in may establish between the dead time pin and the earth Canada supposes one available to establish the dead time the resistance, by determines in the height end switching process the dead time. This dead time hypothesis function adds on the propagation delay to be possible to be in the switching process the complementarity MOSFET closure, in order to avoid the synchronized voltage dropping switch has the puncture situation.
Reliability
Any module must in the early stage through the strict test, guarantee that the design consummation is reliable, in order to avoid only then has the unexpected problem in production process’s final stage. The related module must be possible to carry on the test in the customer system, guaranteed that all has the possibility to cause the system to present the breakdown the correlation factor, for example the radiation fan breakdown, questions and so on radiation fan intermittence stop can give the full consideration. Uses the dispersion-like structure engineers hoped designs the system may long-term usage many years, but very few or will not even present the breakdown. Because the test digit demonstrated that the power source module MTBF reaches as high as for several million hours, can achieve this goal how difficultly not.
But is neglected by the human instead is the printed wiring board reliable question frequently. Looked according to the present tendency that printed wiring board’s area more shrinks is smaller, but needs to process the amperage is getting bigger and bigger, therefore the current density will increase will possibly bring about the hiding-like or other through holes is unable to carry out the normal function.
The printed wiring board has the part to hide the through hole to transmit the massive electric currents, regarding these hiding through hole, its surroundings must have the enough copper to make the protective equipment to provide the protection for it, guaranteed that the design is more reliable durably. This kind of protective equipment may also suppress the z axis the heating inflation scope, if not so, in time production process as well as product use once printed wiring board’s ambient temperature has any change, the covert through hole will then appear externally. Engineer must refer to the printed wiring board manufacturer the specialized opinion, thorough duplicate examines the printed wiring board the design, but the printed wiring board manufacturer may according to them the productivity to provide the related printed wiring board design reliable specialized opinion.
Summary
If we set up the reliable power source supply system using the power source module, then must solve the design reliable problem. The preceding text centralism discusses several subject matters, including the powdered iron magnetic core the reliability, magnetism system’s characteristic, the synchronized voltage dropping switch’s puncture phenomenon as well as high electric current system printed wiring board questions and so on reliability.
