InnoSwitch3-CP
Applications Example
ꢒ1
ꢔꢇ
ꢎꢏ0 ꢕꢝꢒ
1
Rꢊ
ꢃꢄ.ꢄ ꢤΩ
1ꢥ
ꢀ
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ꢁꢂ
ꢁꢂ
3
3
ꢃ
ꢃ
ꢒꢊ
ꢒꢆ
ꢍ1
ꢍꢎ
ꢉꢄ0 µꢇ ꢉꢄ0 µꢇ
ꢡꢟꢒ0ꢉ0ꢀ0ꢉꢑꢟꢉ
ꢢ
ꢡꢟꢒ0ꢉ0ꢀ0ꢉꢑꢟꢉ
ꢣ
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ꢅꢀ ꢁꢂ
3
ꢃ
1/10
ꢎ0
ꢕ
ꢎ0
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ꢇꢈ1
ꢇꢈꢃ
ꢇꢈꢉ
ꢁꢆꢇꢈ
ꢒ1ꢊ
Rꢆ
ꢒꢏꢗ
100 ꢔꢇ
ꢎ00 Ω
ꢊ.8 ꢔꢇ
ꢏ0
ꢕ
1ꢥ
ꢒꢃ
Rꢎ
1ꢏ0 ꢤΩ
1ꢥ
Rꢃ
100 ꢤΩ
1ꢥ
ꢏ0 ꢕ
ꢡR1
ꢡRꢎ
ꢎ.ꢎ ꢔꢇ
ꢕ
R8
10
1ꢥ
ꢒ8
ꢔꢇ
ꢎ00
ꢒ1ꢆ
ꢋꢡꢟꢎ0ꢦꢂꢋꢀ
ꢋꢡꢟꢎ0ꢦꢂꢋꢀ
ꢊꢉ0
R10ꢗ
ꢃ.0ꢎ ꢤΩ
1ꢥ
Ω
1
1
µꢇ
ꢊ00
ꢕ
ꢊ00 ꢕ
R1
ꢎ.00 ꢞΩ
1ꢥ
Rꢏ
ꢉꢏ
ꢕ
ꢕ
ꢒ10
D1
ꢎ0
Ω
Rꢄ
ꢒꢄ
ꢎ.ꢎ µꢇ
Rꢎꢉ
100 ꢤΩ
1ꢥ
DꢇꢈR1800ꢂꢆ
1ꢥ
1.00 ꢤΩ
10 µꢇ
ꢎꢏ
ꢕ
ꢇꢈꢎ
1ꢥ
ꢉꢏ ꢕ
1/8
ꢣ
Rꢎꢏ
CꢒPꢍꢌꢅ3ꢓ
ꢃ.ꢆ ꢨΩ
ꢐꢎ
ꢛꢉꢔS ꢁꢍꢍꢍ
ꢇꢈꢊ
ꢇꢈꢏ
Rꢉ
1.8 ꢞΩ
1ꢥ
R11
ꢎPIꢆꢅꢗ
ꢁCCꢍ
10
Ω
1ꢥ
ꢎPIꢆꢀ
IꢌCꢖSꢍꢃꢖPꢗꢘꢗ
IꢌCꢖSCꢙꢖPꢗꢘꢅ
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ꢎPIꢆꢕ
CCꢅ
ꢒ11
ꢉꢉ0 ꢖꢇ
ꢏ0
ꢕ
ꢋ1
ꢌꢍꢎꢆ
CCꢌ
Rꢎꢃ
10 ꢤΩ
1ꢥ
ꢒꢎ
ꢒꢉ
R1ꢉ
R1ꢎ
ꢔPꢃꢍ
ꢉꢄ µꢇ
ꢉꢄ µꢇ
ꢃꢆ
Ω
100 ꢤΩ
1
ꢎ
ꢉ
ꢃ
R1ꢃ
R1ꢏ
ꢃ00
ꢕ
ꢃ00 ꢕ
1/10
ꢣ
1ꢥ
ꢃ0ꢎ
Ω
1.ꢏ ꢞΩ
ꢈ1
ꢉꢃ ꢜꢓ
R1ꢊ
1ꢥ
1ꢥ
ꢉ1.ꢊ ꢤΩ
1ꢥ
R1ꢆ
ꢒꢎ0
ꢒ1ꢄ
ꢒ18
µꢇ
1ꢊ
ꢉ1.ꢊ ꢤΩ
ꢉꢉ0 ꢖꢇ ꢉꢉ0 ꢖꢇ
1
ꢒ1ꢎ
1ꢥ
1ꢊ
ꢕ
1ꢊ
ꢕ
ꢕ
100 ꢔꢇ
ꢉ0ꢏ ꢕꢝꢒ
ꢒ1ꢉ
ꢎ.ꢎ µꢇ
ꢎꢏ
R18ꢗ
18.0 ꢤΩ
1ꢥ
ꢕ
ꢎ
ꢃ
ꢉ
Rꢎ0
ꢍ
S
ꢁ
R1ꢄ
1ꢎ.ꢆ ꢤΩ
1ꢥ
ꢈꢎ
ꢊ00 µꢓ
ꢃ.0ꢎ ꢤΩ
Cꢆꢊꢈꢉꢆꢙ
1
1ꢥ
ꢕRꢎ
Dꢠꢎꢟ100ꢞ0ꢈ
10
ꢏꢑ
ꢕ
ꢆ
ꢙ
ꢇ1
ꢝ
Rꢋ1
ꢑPP
IS
Rꢎ1
0.01
1ꢥ
ꢎ
ꢏ
Ω
InnoSwitch3-CP
Ω
ꢒ1ꢏ
ꢒ1ꢃ
ꢐ1
ꢜꢀ
-
ꢌꢕꢀ
ꢁꢃC
ꢃ.ꢆ µꢇ
ꢎꢎ µꢇ
ꢏ0
ꢁꢑꢑꢉꢎꢊ8ꢒꢂꢓꢎ08
ꢏ0
ꢕ
ꢉꢈꢊ
ꢕ
ꢋꢅ
ꢋꢌ
ꢗꢑꢘꢙ ꢚꢘꢔꢔeꢚꢙeꢛ
ꢀꢁꢂ8ꢃ0ꢄꢅꢂ0ꢄ0ꢆ1ꢆ
Figure 11. 5 V, 3 A ; 9 V, 3 A ; 15 V, 3 A USB PD 2.0 Compliant Adapter.
The circuit shown in Figure 11 is a 5 V, 3 A ; 9 V, 3 A ; 15 V, 3 A USB
PD 2.0 compliant adapter using INN3268C. This design is DOE Level
6 and EC CoC 5 compliant.
The secondary-side controller of the InnoSwitch3-CP IC provides
output voltage sensing and output current sensing as well as driving
the synchronous rectification FET. The secondary output from the
transformer is rectified by FET Q3 and filtered by capacitors C6 and
C7. High frequency ringing during switching transients that would
Common mode chokes L1 and L2 provide attenuation for EMI. Bridge
rectifiers BR1 and BR2 rectify the AC line voltage and provide a full
wave rectified DC. Thermistor RT1 limits the inrush current when the
power supply is connected to the input AC supply. Fuse F1 isolates
the circuit and provides protection from component failure.
otherwise create radiated EMI is reduced via an RC snubber, R8 and C8.
The gate of Q3 is turned on by the secondary-side controller inside
U1, based on the voltage (sensed via resistor R13) fed to the
FORWARD pin of the IC.
One end of the transformer primary is connected to the rectified DC
bus; the other is connected to the drain terminal of the integrated
MOSFET in the InnoSwitch3-CP IC (U1).
In continuous conduction mode, the FET is turned off prior to the
secondary-side’s requesting the start of a new switching cycle from
the primary. The power FET is turned off when the voltage drop
across the FET falls below a threshold of VSR(TH). Secondary-side
control of the primary-side power MOSFET avoids any possibility of
cross conduction of the two MOSFETs and provides extremely reliable
synchronous rectification.
A low cost RCD clamp formed by diode D1, resistors R2 and R5 and
capacitor C4 limits the peak drain voltage of U1 at the instant of turn
off of the MOSFET inside U1. The clamp helps to dissipate the energy
stored in the leakage reactance of transformer T1.
The InnoSwitch3-CP IC is self-starting, using an internal high-voltage
current source to charge the PRIMARY BYPASS pin capacitor (C15)
when AC is first applied. During normal operation, the primary-side
block is powered from an auxiliary winding on the transformer T1.
Output of the auxiliary (or bias) winding is rectified using diode D3
and filtered using capacitor C14. Resistors R15 and R20 along with
Q7 and VR2 form a linear regulator circuit to control the current
supplied to the PRIMARY BYPASS pin of U1 irrespective of the output
voltage. The Zener VR1 along with resistor R14 and diode D2 provide
a latching OVP in the event of an output overvoltage condition.
The secondary-side of the IC is self-powered from either the output
winding forward voltage or the output voltage. Capacitor C10,
connected to the SECONDARY BYPASS pin of IC U1 provides
decoupling for the internal circuitry.
During CC operation, when the output voltage falls, the device will
directly power itself from the secondary winding. During the on-time
of the primary-side power MOSFET, the forward voltage that appears
across the secondary winding is used to charge the decoupling
capacitor C10 via resistor R13 and an internal regulator. This allows
output current regulation to be maintained down to ~3.4 V. Output
current is sensed by monitoring the voltage drop across resistor R21
between the IS and SECONDARY GROUND pins. A threshold of
approximately 35 mV reduces losses. Once the internal current sense
threshold is exceeded the device regulates the number of switch
pulses to maintain a fixed output current.
In a flyback converter, output of the auxiliary winding tracks the
output voltage of the converter. In the event of an overvoltage on
the output of the converter, the auxiliary winding voltage increases
and causes VR1 to breakdown. This puts current into the PRIMARY
BYPASS pin of U1. If the current into the PRIMARY BYPASS pin
increases above the ISD threshold, the InnoSwitch3-CP controller will
latch-off, preventing any further increase in output voltage.
9
Rev. D 08/18
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