Check analyses the ground connection in power source of switch of DC ／ DC to rebound
[introduction] circuit ground connection looks very simple in circuit principle graph, but, the real property of circuit is by its printed circuit board (PCB) layout decides. If understand well ” ground connection ” the intuitionistic understanding that the physical essence of the ground connection noise that cause can provide a kind to reduce problem of ground connection noise.
Circuit ground connection looks very simple in circuit principle graph, but, the real property of circuit is by its printed circuit board (PCB) layout decides. If understand well ” ground connection ” the intuitionistic understanding that the physical essence of the ground connection noise that cause can provide a kind to reduce problem of ground connection noise.
Ground connection rebounds (Ground Bounce) the transient state voltage that abbreviation ground plays meeting generation extent to be a few bend over; Commonly is cause by flux change. The lead annulus road of transmission electric current made a magnetic field actually, intensity of its magnetic field and electric current become direct ratio. Flux and cross annulus road area and product of magnetic field intensity to become direct ratio.
Road surface of annulus of × of intensity of flux ∝ magnetic field is accumulated
More expressing is: φ of Φ B = BA Cos
Among them flux Φ B is equal to B of magnetic field intensity to multiply in order to cross annulus road plane the Yu Xian of A and magnetic field direction and φ of included angle of vector of unit of face of annulus Lu Ping.
Graph 1 show gave the concern between flux and electric current. Electric current of drive of source of a voltage overcomes flow of road of annulus of resistor edge lead. Electric current and surround the flux photograph of lead is associated. For will different physical quantity connection rises, the right hand that can consider to use you handholds lead (formula of applied right hand) . If your big toe points to voltaic direction, so your other finger surrounds direction of lines of force of edge magnetic field lead. Because those lines of force cross annulus path, formed flux so, in this exemple flux direction enters a page to wear.
Intensity of change magnetic field or annulus road area can cause flux to change. When flux changes, in lead generation and flux change lead D Φ B/d T to become the voltage of direct ratio. What should notice is, secure when annulus road area, electric current changes; Or electric current is constant, annulus road area changes; Or two kinds of circumstances change at the same time — metropolis change flux.
For example, pursue suppose 2 medium switch disconnect suddenly. When electric current stops flow, flux disappears, this meeting produces big tension of a transient state everywhere along lead. If the one part of lead is a ground connection is returned,cite a base, so the voltage that carries for reference with ground n can produce an aiguille, the metropolis in the circuit that is in any use to should bring a foot to be carried for ground connection reference thereby generates wrong signal.
Normally, PCB prints the voltage drop on line resistor is not the main source that ground connection rebounds. 1 ounce (Oz) cupreous resistor is 500 small Europe / number of squares (μ Ω / □ ) , because electric current of this 1 A changes,can produce □ of V/ of 500 μ only rebound voltage — problem consist in uses slightness to print a line or chrysanthemum chain ground connection or accurate electron circuit.
Of parasitism capacitor charge to returned the ground to offer a way for transient state big electric current with discharge. The flux change that because electric current changes,causes also causes ground connection to rebound.
The method that reduces ground connection to rebound in DC/DC switch power source controls flux to change namely — make area of voltaic annulus road and annulus road area change.
Below certain circumstance, pursue for example 3 are shown, electric current keeps constant, and switch switch causes annulus road area to change, because this produces the change of flux. In switch condition 1 in, a good voltage cause passes ideal lead and an ideal current source to be linked together. Electric current includes the flow in the annulus road of ground connection loop in.
In switch condition 2 in, when switch changes the position, same electric current flows in different method. Current source is dc (DC) , and did not change, but annulus road face produced change. The change of annulus road area means the change of flux, produced tension so. Because ground connection loop is the one part of metabolic annulus road, so its meeting generation rebounds voltage.
Ground connection rebounds because flux change is caused,voltage basically is. In DC/DC switch power source, because what electric current of DC of high speed switch causes is in between area of different voltaic annulus road,flux change is.
A reasonable wiring should put true land in the ground floor of join load, won’t cause the change of the change of annulus road area or electric current. Any other and guide connect relevant point to be able to be called ” the ground ” , but it is only along what return way a bit just.
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