ncp1397a ON Semiconductor, ncp1397a Datasheet - Page 16

• Manufacturer Part Number: ncp1397a
• Description: High Performance Resonant Mode Controller With Integrated High-voltage Drivers
• Manufacturer: ON Semiconductor

Dead−Time Control
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.
Deadtime control is an absolute necessity when the
Figure 35. Feedback Configuration Using Direct Connection to the Rt Pin – No Open FB Loop Detection
Figure 34. Feedback Configuration Using Direct Connection to the Rt Pin
Fstart(adj) − RFstart/RFmin
Fmin(adj) − RFmin
Fmax(adj) − Rc + Rskip1 + Rskip2
CSS
Fstart(adj) − RFstart/RFmin
Fmin(adj) − RFmin
Fmax(adj) − Rc + Rskip1 + Rskip2
RFstart
CSS
RFmin
RFstart
RFmin
OK1
OK1
http://onsemi.com
Rc
Rc
Rskip1
Rskip2
Rskip1
Rskip2
16
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 R
whose image serves to discharge the Ct capacitor: we control
the dead−time. The typical range evolves between 100 ns
(R
the typical waveforms.
DT
1N4148
= 3.5 kW) and 2 ms (R
SS
Fmax
Rt
FB
Skip/Disable
SS
Fmax
Rt
FB
Skip/Disable
NCP1397
NCP1397
Rbias
GND
VCC
GND
VCC
DT
DT
to ground, it creates a current
= 83.5 kW). Figure 39 shows