MV1012SC datasheet(23/33 Pages) SHINDENGEN

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MV1012SC

(a) Noise fades within

LEB period

(b) Noise does not fade

within LEB period

Figure 17 Example of false detection due to switching-on noise

The resonant current flowing in toff2 period also flows to the current detection resistor Rcs. Vcs oscillates around 0 V

during the toff2 period. Even in case of the same VREF, Io accuracy and smoothness of dimming characteristics may be

degraded (see VREF ripple: Small in Figure 19) if the on-time changes significantly depending on whether Vcs at on-timing

exceeds 0 V, as shown in Figure 18.

The amplitude of Vcs during the toff2 period can be reduced by reducing the Coss of MOSFET and the Cr of the

resonant capacitor. Increasing the ripple voltage of VREF averages any changes in the on-time and reduces

Vcs-dependent changes in Io at switching-on. (See VREF ripple: Large in Figure 19.)

Figure 18 Changes in on-time determined by switching-on

timing in the [B] region

Figure 19 Example illustrating degraded smoothness of

dimming characteristics

LEB period

VCS

VDS

Vi+VF

Gate

Vcc

VREF

×1/5

VREF

VREF ripple: Small

VREF ripple: Large

CAT.No.1A0602-1E

MV1012SC Arkusz danych(PDF) 23 Page - Shindengen Electric Mfg.Co.Ltd