InnoSwitch3-CP
The interaction between the leakage reactance of the output
windings and the SR FET capacitance (COSS) leads to ringing on the
voltage waveform at the instance of voltage reversal at the winding
due to primary MOSFET turn-on. This ringing can be suppressed
using an RC snubber connected across the SR FET. A snubber
resistor in the range of 10 Ω to 47 Ω may be used (higher resistance
values lead to noticeable drop in efficiency). A capacitance value of
1 nF to 2.2 nF is adequate for most designs.
+
R1
Rꢇ
1ꢈꢃ1ꢃ8
ꢀ
S
ꢁ
Output Capacitor
ꢁꢂꢃꢄ
Low ESR aluminum electrolytic capacitors are suitable for use with
most high frequency flyback switching power supplies though the use
of aluminum-polymer solid capacitors have gained considerable
popularity due to their compact size, stable temperature characteristics,
extremely low ESR and high RMS ripple current rating. These
capacitors enable the design of ultra-compact chargers and adapters.
ꢅPP
IS
InnoSwitch3-CP
ꢀꢁꢂ8ꢃ0ꢄꢂ081ꢅ1ꢆ
(a)
Typically, 200 mF to 300 mF of aluminum-polymer capacitance per
ampere of output current is adequate. The other factor that
influences choice of the capacitance is the output ripple. Ensure that
capacitors with a voltage rating higher than the highest output
voltage plus sufficient margin be used.
+
R1
Rꢆ
Output Voltage Feedback Circuit
The output voltage FEEDBACK pin voltage is 1.265 V [VFB]. A voltage
divider network should be connected at the output of the power
supply to divide the output voltage such that the voltage at the
FEEDBACK pin will be 1.265 V when the output is at its desired
voltage. The lower feedback divider resistor should be tied to the
SECONDARY GROUND pin. A 300 pF (or smaller) decoupling
capacitor should be connected at the FEEDBACK pin to the
SECONDARY GROUND pin of the InnoSwitch3-CP IC. This capacitor
should be placed close to the InnoSwitch3-CP IC.
ꢀ
S
ꢁ
ꢄ.ꢆ ꢇ
ꢁꢂꢃꢄ
ꢅPP
IS
InnoSwitch3-CP
ꢀꢁꢂ8ꢃ0ꢄꢂ0ꢅ1818
(b)
Figure 17. (a) Line OV Only; (b) Line UV Only.
ꢆR ꢑꢒꢓ
ꢀ
S
ꢁ
InnoSwitch3-CP
ꢎꢆ
100 ꢉꢑ
ꢁꢂꢃꢄ
ꢀꢌꢔꢕꢋꢌꢍ ꢑꢒꢓ
ꢋꢉꢊ ꢎꢈꢉꢏꢌꢈꢐꢐeꢌ
ꢅPP
IS
ꢆeꢇꢈꢉꢊꢋꢌꢍ
ꢎꢈꢉꢏꢌꢈꢐ ꢁꢎ
ꢀꢁꢂ8ꢃ08ꢂ081ꢄ1ꢅ
Figure 18. Fast AC Reset Configuration.
13
Rev. D 08/18
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