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Zakładka z wyszukiwarką danych komponentów |
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Zakładka z wyszukiwarką danych komponentów |
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ISL6322CRZ Arkusz danych(PDF) 35 Page - Intersil Corporation |
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ISL6322CRZ Arkusz danych(HTML) 35 Page - Intersil Corporation |
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35 / 41 page  35 FN6328.2 August 2, 2007 “Compensation with Load-line Regulation” on page 35 and “Compensation without Load-line Regulation” on page 36. COMPENSATION WITH LOAD-LINE REGULATION The load-line regulated converter behaves in a similar manner to a peak current mode controller because the two poles at the output filter L-C resonant frequency split with the introduction of current information into the control loop. The final location of these poles is determined by the system function, the gain of the current signal, and the value of the compensation components, RC and CC. Since the system poles and zero are affected by the values of the components that are meant to compensate them, the solution to the system equation becomes fairly complicated. Fortunately, there is a simple approximation that comes very close to an optimal solution. Treating the system as though it were a voltage-mode regulator, by compensating the L-C poles and the ESR zero of the voltage mode approximation, yields a solution that is always stable with very close to ideal transient performance. Select a target bandwidth for the compensated system, f0. The target bandwidth must be large enough to assure adequate transient performance, but smaller than 1/3 of the per-channel switching frequency. The values of the compensation components depend on the relationships of f0 to the L-C pole frequency and the ESR zero frequency. For each of the following three, there is a separate set of equations for the compensation components. In Equation 41: - L is the per-channel filter inductance divided by the number of active channels, - C is the sum total of all output capacitors, - ESR is the equivalent series resistance of the bulk output filter capacitance, and -VPP is the peak-to-peak sawtooth signal amplitude as described in the “Electrical Specifications” on page 7. Once selected, the compensation values in Equation 41 assure a stable converter with reasonable transient performance. In most cases, transient performance can be improved by making adjustments to RC. Slowly increase the value of RC while observing the transient performance on an oscilloscope until no further improvement is noted. Normally, CC will not need adjustment. Keep the value of CC from the case equations in Equation 41 unless some performance issue is noted. The optional capacitor C2, is sometimes needed to bypass noise away from the PWM comparator (see Figure 23). Keep a position available for C2, and be prepared to install a high-frequency capacitor of between 22pF and 150pF in case any leading edge jitter problem is noted. FIGURE 23. COMPENSATION CONFIGURATION FOR LOAD-LINE REGULATED ISL6322 CIRCUIT ISL6322 COMP CC RC RFB FB VDIFF C2 (OPTIONAL) IDROOP 1 2 π LC ⋅ ⋅⋅ --------------------------------f 0 > R C R FB 2 π f 0 Vpp LC ⋅ ⋅⋅ ⋅ ⋅ 0.66 V IN ⋅ -------------------------------------------------------- ⋅ = C C 0.66 V IN ⋅ 2 π V PP RFB f0 ⋅⋅ ⋅ ⋅ ---------------------------------------------------- = Case 1: 1 2 π LC ⋅ ⋅⋅ -------------------------------- f 0 1 2 π C ESR ⋅⋅ ⋅ ------------------------------------- < ≤ R C R FB V PP 2 π ⋅ () ⋅ 2 f 0 2 LC ⋅⋅ ⋅ 0.66 V IN ⋅ ----------------------------------------------------------------- ⋅ = C C 0.66 V IN ⋅ 2 π ⋅ ()2 f 0 2 V PP RFB LC ⋅ ⋅⋅ ⋅ ⋅ ------------------------------------------------------------------------------------- = Case 2: (EQ. 41) f 0 1 2 π C ESR ⋅⋅ ⋅ ------------------------------------- > R C R FB 2 π f 0 Vpp L ⋅⋅ ⋅ ⋅ 0.66 V IN ESR ⋅⋅ --------------------------------------------- ⋅ = C C 0.66 V IN ESR C ⋅⋅ ⋅ 2 π V PP RFB f0 L ⋅⋅ ⋅ ⋅ ⋅ ---------------------------------------------------------------- = Case 3: ISL6322 |
Podobny numer części - ISL6322CRZ |
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Podobny opis - ISL6322CRZ |
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