MS1003SH datasheet(10/41 Pages) SHINDENGEN

10 / 41 page

MS1003SH･MS1004SH

Application Note Ver.2.2

SHINDENGEN ELECTRIC MFG. CO. , LTD

10/41

3.2.3 Soft drive

The soft drive circuit supplies a trigger voltage slightly greater than

the gate threshold of the main switch as a gate drive voltage before

constant voltage driving begins. This prevents the supply of greater

gate voltage than necessary.

The soft drive reduces losses by the gate charge voltage and reduces

noise by controlling the resonating capacitor discharge peak current.

3.2.4 Trough skip operation

The MS1003SH and MS1004SH monitor the switching cycle. If the switching cycle length becomes shorter

than the trough skip start cycle T (bottom skip start) of 7.5 μs (TYP), the IC enter the following modes:

MS1003SH moves from the normal partial resonance mode to the 1 trough skip mode (switching on

at the second trough).

MS1004SH moves from the normal partial resonance mode to the 2 trough skip mode (switching on

at the third trough).

In trough skip mode, the MS1003SH extends the off-period by a cycle of resonance and the MS1004SH by

two cycles of resonance. This controls an increase in the frequency. Once in trough skip mode, the cycle

monitoring timer setting changes. When the time from switching on to the first voltage trough becomes

longer than T (bottom skip stop) of 13 μs (TYP), the IC returns to normal partial resonance mode. Using

hysteresis in this manner prevents jitter and acoustic noise.

VDS

動作

ﾓｰﾄﾞ

部分共振

谷飛び

ｵﾌ幅

監視

ﾀｲﾏ

T(bottom skip start)

T(bottom skip stop)

T(bottom skip start)

Sequence of MS1003SH

VGS

ドレイン電流にあわせた

ゲート電圧供給

急峻なゲートチャージ

を低減

軽負荷時の

無効電荷削減

共振コンデンサ放電電流の

ダンピング

Gate voltage supply

matched to drain current

Reducing gate charge

spikes

Reducing

reactive charge

under light loads

Damping of resonating

capacitor discharge current

Partial

resonance

Trough skip

Partial

resonance

OFF range

monitoring

timer

Operating

mode

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