NCP1397A データシートの表示（PDF） - ON Semiconductor

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NCP1397A

High Performance Resonant Mode Controller with Integrated High-Voltage Drivers

ON Semiconductor 

NCP1397A, NCP1397B

Fstart(adj) − RFstart/RFmin

Fmin(adj) − RFmin

Fmax(adj) − Rc + Rskip1 + Rskip2

RFstart

RFmin

Rc

CSS

OK1

Rskip1

SS

Fmax

Rt

VCC

FB

GND

Skip/Disable

NCP1397

Rskip2

Figure 34. Feedback Configuration Using Direct Connection to the Rt Pin

Fstart(adj) − RFstart/RFmin

Fmin(adj) − RFmin

Fmax(adj) − Rc + Rskip1 + Rskip2

RFstart

RFmin

Rc

CSS

OK1

Rskip1

Rskip2

Rbias

SS

Fmax

Rt

VCC

FB

GND

Skip/Disable

NCP1397

1N4148

Figure 35. Feedback Configuration Using Direct Connection to the Rt Pin – No Open FB Loop Detection

Dead−Time Control

Deadtime control is an absolute necessity when the

half−bridge configuration comes to play. The deadtime

technique consists in inserting a period during which both

high and low side switches are off. Of course, the deadtime

amount differs depending on the switching frequency, hence

the ability to adjust it on this controller. The option ranges

between 100 ns and 2 ms. The deadtime is actually made by

controlling the oscillator discharge current. Figure 36

portrays a simplified VCO circuit based on Figure 25.

During the discharge time, the clock comparator is high and

invalidates the AND gates: both outputs are low. When the

comparator goes back to the low level, during the timing

capacitor Ct recharge time, A and B outputs are validated.

By connecting a resistor RDT to ground, it creates a current

whose image serves to discharge the Ct capacitor: we control

the dead−time. The typical range evolves between 100 ns

(RDT = 3.5 kW) and 2 ms (RDT = 83.5 kW). Figure 39 shows

the typical waveforms.

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