InnoSwitch3-EP
(1-D) × T
KP ≡ KDP
=
t
T = 1/fS
Primary
(1-D) × T
D × T
t
Secondary
(a) Discontinuous, KP > 1
T = 1/fS
Primary
(1-D) × T = t
D × T
Secondary
(b) Borderline Discontinuous/Continuous, KP = 1
PI-2578-103114
Figure 18. Discontinuous Conduction Mode Current Waveform, KP > 1.
Repeat tests under steady-state conditions and verify that the
leading edge current spike is below ILIMIT(MIN) at the end of tLEB(MIN)
Under all conditions, the maximum drain current for the primary
Quick Design Checklist
.
As with any power supply, the operation of all InnoSwitch3-EP
designs should be verified on the bench to make sure that component
limits are not exceeded under worst-case conditions.
MOSFET should be below the specified absolute maximum ratings.
3. Thermal Check – At specified maximum output power, minimum
input voltage and maximum ambient temperature, verify that
temperature specification limits for InnoSwitch3-EP IC,
transformer, output SR FET, and output capacitors are not
exceeded. Enough thermal margin should be allowed for
part-to-part variation of the RDS(ON) of the InnoSwitch3-EP IC.
Under low-line, maximum power, a maximum InnoSwitch3-EP
SOURCE pin temperature of 110 °C is recommended to allow for
these variations.
As a minimum, the following tests are strongly recommended:
1. Maximum Drain Voltage – Verify that VDS of InnoSwitch3-EP and
SR FET do not exceed 90% of breakdown voltages at the highest
input voltage and peak (overload) output power in normal
operation and during start-up.
2. Maximum Drain Current – At maximum ambient temperature,
maximum input voltage and peak output (overload) power.
Review drain current waveforms for any signs of transformer
saturation or excessive leading-edge current spikes at start-up.
18
Rev. D 08/18
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