Fundamentals of Power Electronics 超清晰，文本完全版，有标签，已加入空白页

dickzzzzz

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i0977454522

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i0977454522

Note that the propensity to enter this state increases as the
duty cycle increases (input lowered). So we should always try to rule out this possibility at
VINMIN . We could certainly avoid this problem altogether, by choosing DCM (discontinuous
conduction mode). But otherwise, in CCM, slope compensation is the recognized sure-fix.
Though it is interesting to note that by applying slope compensation, we are in effect
blending a little voltage mode control with current mod

i0977454522

Note that the propensity to enter this state increases as the
duty cycle increases (input lowered). So we should always try to rule out this possibility at
VINMIN . We could certainly avoid this problem altogether, by choosing DCM (discontinuous
conduction mode). But otherwise, in CCM, slope compensation is the recognized sure-fix.
Though it is interesting to note that by applying slope compensation, we are in effect
blending a little voltage mode control with current.

i0977454522

The subharmonic pole peaking is akin to the double-pole response of an LC filter. So it, too,
has a certain “Q”, which depends on the slopes of the inductor current, and the applied slope
compensation. If the applied slope compensation is too low, the Q will increase, unless we
increase the inductance (to decrease the slopes of the inductor current correspondingly).
In effect, this means we need a certain minimum inductance for a given slope compensation,
to remain stable. Alternatively, we need a minimum slope compensation for a given
inductance, to remain stable. However, slope compensation, the way it is commonly applied,
affects the peak current limit too, and that can affect the output power capability of the
converter. We have to be careful about that too. In general, we should check that we are
being able to meet the required output power, at both ends of the input voltage range.
So how much of slope compensation should we really apply? In the chapter on DC-DC
converter design, equations for the minimum inductance were provided. These were actually
based on ensuring that Q never exceeds a value of 2 — that value in turn being based on
various bench measurements and data, using typical dc-dc converters. A smaller value of Q
will certainly be more “safe”, but it will require a larger inductor. A large value of Q will
lead to subharmonic instability. Hence Q = 2 is normally a good compromise, but it is
prudent to confirm the resulting choice of inductor on the bench, on a case-by-case basis.

i0977454522

The subharmonic pole peaking is akin to the double-pole response of an LC filter. So it, too,
has a certain “Q”, which depends on the slopes of the inductor current, and the applied slope
compensation. If the applied slope compensation is too low, the Q will increase, unless we
increase the inductance (to decrease the slopes of the inductor current correspondingly).
In effect, this means we need a certain minimum inductance for a given slope compensation,
to remain stable. Alternatively, we need a minimum slope compensation for a given
inductance, to remain stable. However, slope compensation, the way it is commonly applied,
affects the peak current limit too, and that can affect the output power capability of the
converter. We have to be careful about that too. In general, we should check that we are
being able to meet the required output power, at both ends of the input voltage range.

iceburg

文字清晰版整合，有标签

shenkehit

回复 1# zhanghanru
感谢楼主分享！

努力攒积分

谢谢楼主分享~很有用！

mrzhoubin

回复 1# zhanghanru


   good very thanks