ON Semiconductor NCP1351 Series User Manual

NCP1351PRINTGEVB
NCP1351 16 V/32 V – 40 W
Printer Power Supply
Evaluation Board
User's Manual
Description
The present document describes a printer power supply
operated by the NCP1351, a fixed
controller. The board can deliver 10 W average on a 16 V
output and 30 W average on a 32 V output with a transient
peak power capability of 80 W. It however exhibits a low
standby power: below 150 mW at no load whatever the input
voltage. Let us first review the benefit of using the
NCP1351:
The NCP1351 at a Glance
Fixed t , Variable t Current-mode Control:
on off
Implementing a fixed peak current mode control (hence
the more appropriate term "quasi-fixed" t
modulates the off time duration according to the output
power demand. In high power conditions, the switching
frequency increases until a maximum is hit. This upper limit
depends on an external capacitor selected by the designer. In
light load conditions, the off time expands and the NCP1351
operates at a lower frequency. As the frequency reduces, the
contribution of all frequency-dependent losses accordingly
goes down (driver current, drain capacitive losses, switching
losses), naturally improving the efficiency at various load
levels.
Peak Current Compression at Light Loads:
Reducing the frequency will certainly force the converter
to operate into the audible region. To prevent the transformer
mechanical resonance, the NCP1351 gradually reduces –
compresses – the peak current setpoint as the load becomes
lighter. When the current reaches 30% of the nominal value,
the compression stops and the off duration keeps expanding
towards low frequencies.
Low Standby-power:
The frequency reduction technique offers an excellent
solution for designers looking for low standby power
converters. Also, compared to the skip-cycle method, the
smooth off time expansion does not bring additional ripple
in no-load conditions: the output voltage remains quiet.
© Semiconductor Components Industries, LLC, 2012
October, 2012 − Rev. 0
t
/variable off time
on
), the NCP1351
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EVAL BOARD USER'S MANUAL
Natural Frequency Dithering:
The quasi-fixed t mode of operation improves the EMI
on
signature since the switching frequency varies with the
natural bulk ripple voltage.
Extremely Low Start-up Current:
Built on a proprietary circuitry, the NCP1351 startup
section does not consume more than 10 mA during the
startup sequence. The designer can thus easily combine
startup time and standby consumption.
Overload Protection Based on Fault Timer:
Every designer knows the pain of building converters
where a precise over current limit must be obtained. When
the fault detection relies on the auxiliary V
increases. Here, the NCP1351 observes the lack of feedback
current and starts a timer to countdown. At the end of its
charge, the timer either triggers an auto-recovery sequence
(auto-restart, B and D versions) or permanently latches-off
(A and C). On C and D versions the fault timer is started at
an output power corresponding to 60% of the maximum
deliverable power; to allow transient peak power delivery.
Latch Fault Input:
A dedicated input lets the designer externally trigger the
latch to build additional protections such as over-voltage
(OVP) or over-temperature (OTP).
Figure 1. NCP1351 Evaluation Board
, the pain even
CC
Publication Order Number:
EVBUM2150/D