InnoSwitch3-EP
Applications Example
ꢇ10
ꢅꢄ0 ꢈꢉ
ꢌꢆ0 ꢋꢏꢇ
ꢋRꢌ
ꢐꢑꢏꢒ8ꢋꢌꢂ1ꢃꢂꢉ
8.ꢌ ꢋ
ꢀꢁ ꢂꢃ ꢄꢅꢆ ꢇ
ꢌ
1
ꢉꢍ1
ꢍꢌ
10 µꢎ
ꢇꢌ1 Rꢌꢆ
1 ꢚꢉ ꢃ0 Ω
ꢌ00 ꢋ 1/8 ꢘ
ꢇ1ꢅ
ꢌ.ꢌ µꢉ
ꢇ1ꢓ
ꢊ80 µꢉ
1ꢊ ꢋ
Rꢃ0
Rꢌꢄ
1.ꢌ ꢑΩ
1ꢛ
100 Ω
1/10 ꢘ
ꢌꢆ ꢋ
ꢀꢁ ꢂ
ꢉꢊꢋ
ꢇꢌꢅ
ꢌ.ꢌ ꢚꢉ
ꢆ0 ꢋ
1/1ꢊ ꢘ
ꢉꢍꢌ
ꢊ
ꢇꢅ
1000 ꢈꢉ
ꢊꢃ0 ꢋ
Rꢃ
ꢌ ꢑΩ
1ꢛ
R8
ꢌ00 ꢗΩ
ꢜꢌ
ꢏꢝꢅꢅ8ꢊ
ꢈ ꢂꢃ ꢄꢅ3 ꢇ
ꢍꢃ
10 µꢎ
Rꢌꢅ
ꢇꢌꢌ
ꢙR1
Rꢌꢓ
ꢊꢌ Ω 1 ꢚꢉ
R1ꢊ
Dꢉ08ꢐ
800 ꢋ
100 Ω
1/10 ꢘ
ꢇ18
ꢆꢊ0 µꢉ
ꢊ.ꢃ ꢋ
1/8 ꢘ ꢌ00 ꢋ
1ꢃꢃ ꢗΩ
1ꢛ
D1
Rꢌꢌ DꢉꢍR1ꢊ00ꢂꢄ
ꢊ8 Ω
ꢊ00 ꢋ
ꢇꢌꢃ
ꢌ.ꢌ ꢚꢉ
ꢆ0 ꢋ
1/1ꢊ ꢘ
Rꢅ
1.8 ꢑΩ
1ꢛ
ꢆ
ꢖꢇ
ꢜ1
ꢏꢝꢊꢅꢌ0
ꢅ
ꢃ
ꢇꢌ
10 µꢉ
ꢅ00 ꢋ
ꢇꢃ
10 µꢉ
ꢅ00 ꢋ
ꢉ1
1 ꢏ
R1ꢃ
ꢃꢃ.ꢌ ꢗΩ
1ꢛ
ꢔ1
ꢕꢕ1ꢊꢌ1
Rꢓ
ꢎ
Rꢔ1
10 Ω
1/1ꢊ ꢘ
ꢟ
ꢅꢄ Ω
ꢇ1ꢌ
ꢌ.ꢌ µꢉ
ꢌꢆ ꢋ
1/10 ꢘ
ꢇꢄ
Dꢄ
ꢌ.ꢌ µꢉ
ꢇ8
ꢃꢃ0 ꢈꢉ
ꢆ0 ꢋ
ꢔꢄ - ꢁꢕꢈ
ꢂꢇꢒ
DꢉꢍR1ꢌ00ꢂꢄ
ꢌꢆ ꢋ
ꢋR1
ꢑꢑꢐꢒꢆꢌꢃ1ꢙꢂꢄꢂꢉ
ꢓ
ꢋ
ꢌ
S
ꢂ
Dꢃ
R1ꢌ
0.ꢌ Ω
1ꢛ
ꢙꢏꢋꢌ1ꢘꢐꢂꢄꢂꢉ
ꢒꢎꢋꢊꢉꢎꢓ
Rꢌꢊ
ꢏꢑ
ꢃꢊ Ω
Rꢊ
ꢊ.ꢌ ꢗΩ
1/10 ꢘ
1/10 ꢘ
ꢑPP
IS
InnoSwitch3-EP
ꢞ1
ꢇꢊ
ꢅ.ꢄ µꢉ
1ꢊ ꢋ
ꢇꢆ
ꢌꢌ µꢉ
ꢆ0 ꢋ
ꢍ1
ꢃꢃ0 µꢎ
ꢁꢖꢖꢃꢊꢄꢌꢇꢂꢎꢊ0ꢌ
ꢉꢊꢋ
ꢀꢁꢂ8ꢃꢄꢅꢂ0ꢆ1818
Figure 9. Schematic DER-611, 5 V, 0.3 A and 12 V, 0.7 A for HVAC (Heating, Ventilation and Air-Conditioning) Application.
The circuit shown in Figure 9 is a low cost 5 V, 0.3 A and 12 V, 0.7 A
dual output power supply using INN3672C. This dual output design
features high efficient design satisfying cross regulation requirement
without a post-regulator.
the transformer is rectified by SR FET Q1 and filtered by capacitor
C18. High frequency ringing during switching transients that would
otherwise create radiated EMI is reduced via a snubber (resistor R24
and capacitor C22). The 12 V secondary of the transformer is rectified
by SR FET Q2 and filtered by capacitor C19. High frequency ringing
during switching transients that would otherwise create radiated EMI
is reduced via a snubber (resistor R25 and capacitor C21).
Bridge rectifier BR1 rectifies the AC input supply. Capacitors C2 and
C3 provide filtering of the rectified AC input and together with
inductor L1 form a pi-filter to attenuate differential mode EMI.
Y capacitor C10 connected between the power supply output and
input help reduce common mode EMI.
Synchronous rectifications (SR) are provided by MOSFETs Q1 and Q2.
Q1 and Q2 are turned on by the secondary-side controller inside IC
U1, based on the winding voltage sensed via resistor R9 and fed into
the FORWARD pin of the IC.
Thermistor RT1 limits the inrush current when the power supply is
connected to the input AC supply.
In continuous conduction mode of operation, the MOSFET is turned
off just prior to the secondary-side’s commanding a new switching
cycle from the primary. In discontinuous conduction mode of
operation, the power MOSFET is turned off when the voltage drop
across the MOSFET falls below 0 V. 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.
Input fuse F1 provides protection against excess input current
resulting from catastrophic failure of any of the components in the
power supply. One end of the transformer primary is connected to
the rectified DC bus; the other is connected to the drain terminal of
the MOSFET inside the InnoSwitch3-EP IC (U1).
A low-cost RCD clamp formed by diode D1, resistors R22, R8, 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 secondary-side of the IC is self-powered from either the
secondary winding forward voltage or the output voltage. Capacitor
C7 connected to the SECONDARY BYPASS pin of InnoSwitch3-EP IC
U1, provides decoupling for the internal circuitry.
The InnoSwitch3-EP IC is self-starting, using an internal high-voltage
current source to charge the PRIMARY BYPASS pin capacitor (C6)
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 D7
and filtered using capacitor C5. Resistor R6 limits the current being
supplied to the PRIMARY BYPASS pin of InnoSwitch3-EP IC (U1). The
latch off primary-side overvoltage protection is obtained using Zener
diode VR1 with current limiting resistor R26.
Total output current is sensed by R12 between the IS and GROUND
pins with a threshold of approximately 35 mV to reduce losses. Once
the current sense threshold is exceeded the device adjusts the
number of switch pulses to maintain a fixed output current.
The output voltages are sensed via resistor divider R13, R16, and
R27, and output voltages are regulated so as to achieve a voltage of
1.265 V on the FEEDBACK pin. The 12 V phase boost circuit, R30 and
C24, in parallel with 12 V feedback resistor, R27, and 5 V phase boost
circuit, R29 and C23, in parallel with 5 V feedback resistor, R16,
reduce the output voltage ripples. Capacitor C8 provides noise
The secondary-side controller of the InnoSwitch3-EP IC provides
output voltage sensing, output current sensing and drive to a
MOSFET providing synchronous rectification. The 5 V secondary of
9
Rev. D 08/18
www.power.com
POWERINT [ Power Integrations ]
