MV1012SC datasheet(21/33 Pages) SHINDENGEN

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MV1012SC

5.1 Operation in each mode

5.1.1

[A] Frequency modulation region

The operation waveforms in the frequency modulation region are those in critical conduction mode shown in Figure 14.

Figure 13 shows the internal circuit of the CS pin. Voltage 1/5 of VREF is compared to current detection threshold voltage

Vth_CS (0.495V); the lower voltage is used as the CS pin reference voltage. In actual use, both Vth_CS and VREF x1/5 will

change slightly. To make sure Vth_CS is used as the reference, set VREF to 2.6 V or greater.

If resonant period Toff2 is significantly less than ton and toff1, IL may be regarded as a triangle wave. Thus, Io = 1/2 x Ip,

and output current Io becomes proportional to VREF. However, the oscillation frequency increases as VREF decreases; the

ratios of Toff2 and detection delay to the period of a cycle will therefore increase. In this case, the proportional relationship

between Io and VREF may change somewhat.

REF pin voltage VREF: 2.6 V or more

REF pin voltage VREF: 2.5 V or less

Figure 13 CS pin internal circuit diagram

Figure 14 Operation waveforms in [A] frequency modulation region

GND

VREF×1/5

GND

Vth_CS

=0.495V

●

VREF ≥ 2.6V (dimming ratio of 100%)

●

VREF < 2.5V

CAT.No.1A0602-1E

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