|
|
PDF AND8331 Data sheet ( Hoja de datos )
| Número de pieza | AND8331 | |
| Descripción | Quasi-Resonant CurrentMode Controller | |
| Fabricantes | ON Semiconductor | |
| Logotipo |  |
|
Hay una vista previa y un enlace de descarga de AND8331 (archivo pdf) en la parte inferior de esta página. Total 16 Páginas | ||
|
No Preview Available !
AND8331/D
Quasi-Resonant Current-
Mode Controller for High-
Power ac-dc Adapters
Prepared by: Stéphanie Conseil
ON Semiconductor
http://onsemi.com
Introduction
This document describes the implementation of the
DAP013 inside an AC-DC adapter.
The DAP013 offers everything to build high performance
AC-DC converters or offline adapters. Thanks to a novel
valley lockout system, the controller is able to switch inside
the drain-source valley and is immune to valley jumping
instabilities. When the output load decreases significantly,
the controller toggles to a fixed peak current/variable
frequency mode that ensures very low standby power
consumption. And last, but not least, the DAP013 features
the usual protections that help to build cheap and safe power
supplies: OVP, OTP, Brown-Out (C and D options),
Short-circuit protection (latched for A, C versions and
auto-recovery for D, F versions), soft-start, OPP, internal
TSD...
To summarise, the DAP013 offers the following
characteristics:
• Quasi-resonant Peak Current-mode Control Operation
• Valley Switching Operation with Valley-lockout for
Noise-immune Operation
• VCO Mode (fixed peak current, variable frequency) in
Light Output Load for Improved Standby Dissipation
• Internal 5 ms Soft-start
• Loss-free Adjustable Over Power Protection
• Auto-recovery or Latched Internal Output Short-circuit
Protection
• Adjustable Timer for Improved Short-circuit Protection
• Over-voltage and Over-temperature Protection Inputs
• Brown-out Input for C and D Versions
• +500 mA / –800 mA Peak Current Source/Sink
Capability
• Internal Temperature Shutdown
• Direct Optocoupler Connection
• 3 ms Blanking Delay to Ignore Leakage Ringing at
Turn-off
• Extremely Low No-load Standby Power
• SO14 Package
Pin Description
Over Power Protection pin (OPP, pin 1): applying a
negative voltage on this pin reduces the internal maximum
peak current set point.
Over Temperature Protection pin (OTP, pin 2): Connect
an NTC between this pin and ground. An internal current
source biases the NTC. When the NTC pulls the pin down,
the circuit permanently latches-off.
Timer pin (Timer, pin 3): Wiring a capacitor from this pin
to ground helps selecting the timer duration.
Zero Voltage Detection pin (ZCD, pin 4): Connected to
the auxiliary winding, this pin detects the core reset event.
Timing Capacitor pin (Ct, pin 5): A capacitor connected
to this pin acts as the timing capacitor in VCO mode.
Feedback pin (FB, pin 6): Hooking an optocoupler
collector to this pin will allow regulation.
Current Sense pin (CS, pin 7): This pin monitors the
primary current and triggers the fault if needed.
Ground pin (GND, pin 8): The controller ground.
Driver pin (DRV, pin 9): This pin delivers pulses to the
power MOSFET.
Power Supply pin (VCC, pin 10): This pin supplies the
controller and accepts voltage up to 28 V.
Brown-Out pin (BO, pin 11): Allows shutting-down the
controller for a chosen input voltage level. (C and D versions
only)
Over Voltage Protection pin (OVP, pin 12): By pulling
this pin high, the controller can be permanently latched-off.
High Voltage pin (HV, pin 14): Connected to the bulk
capacitor, this pin powers the internal current source to
deliver a start-up current that charges the VCC capacitor.
I. Over Power Protection
1. How Does It Work?
A flyback operated in Quasi Resonant mode exhibits wide
peak current variations in relationship to the input voltage
conditions. As a result, the converter output power range
widens as the input voltage increases. To cope with safety
requirements, the designer needs to make the power output
capability independent from the input conditions. A possible
© Semiconductor Components Industries, LLC, 2008
June, 2008 − Rev. 0
1
Publication Order Number:
AND8331/D
1 page  
AND8331/D
The Ilatch current (91 mA typ.) biases the Negative
Temperature Coefficient sensor (NTC), naturally imposing
a dc voltage on the OTP pin. When the temperature
increases, the NTC’s resistance reduces (at 110°C, RNTC =
8.8 kW instead of 470 kW at 25°C) bringing the pin 2 voltage
down until it reaches a typical value of 0.8 V: the comparator
trips and latches-off the controller (Figure 7). Controller
reset occurs when a) the VCC is cycled from on to off b) the
brown-out pin senses a stop condition on the bulk voltage.
During start-up and soft-start, the output of the OTP
comparator is masked to allow the voltage on pin OTP to
grow if a filtering capacitor is installed across the NTC.
The filtering capacitor value should be 1 nF.
In DAP013, the OTP trip point corresponds to a resistance of:
RNTC
+
VOTP
Ilatch
+
0.8
91 m
+
8.79
kW
(eq. 17)
This corresponds to a temperature of 110°C using the
TTC03-474.
VCC
VDRV
VOTP
Figure 7. Capture of an OTP Event. Here, the NTC was Heated with a Hairdryer...
III. Timer Pin and Fault Management
Protection against short-circuit or overload is insured by
monitoring the current sense signal. The controller reaction
is thus fully independent from the auxiliary to power
winding coupling. When the primary current exceeds ILimit,
the “Max Ip” comparator trips and the timer capacitor
charges by the ItimerC current source. When the current
comes back within safe limits, the “Max Ip” comparator
becomes silent and the PWM comparator triggers the
discharge of the timer capacitor. The timer capacitor is thus
discharged by a constant current ItimerD. The internal
circuitry appears in Figure 8.
http://onsemi.com
5
5 Page 
AND8331/D
Based on lab experiments, the switching period gap
between the end of 4th valley operation (Tsw1) and VCO
mode (Tsw2) for a FB voltage near 1.4 V (which is the
threshold for VCO mode to 4th valley transition, VFB
increasing ) must not exceed 12 ms. Thus, for VFB = 1.4 V,
we will have:
Thus, we can deduce the timing capacitor value knowing
VCt, Tsw2 and the charging current source ICt (20 mA typ.
from datasheet):
Ct
+
ICtTsw2
1.83
(eq. 23)
Tsw2 + Tsw1 ) 12 ms
(eq. 21)
Equation 13 allows calculating VCt for VFB = 1.4 V:
VCt + 6.5 * (10ń3) 1.4 + 1.83 V (eq. 22)
Application Example: 19 V/60 W Adapter
• VIN,minDC = 100 V
• Vout + Vf = 19 + 0.6 V
• Lp = 190 mH
• Clump = 200 pF
• Nps = 0.25
• Rsense = 0.25
First, with Equation 14, we estimate Tsw1 which is the
switching period of our power supply for an output load
corresponding to a VFB = 0.8 V:
ǒ Ǔ ǸTsw1
+
0.2
Rsense
LP
1
VIN,minDC
)
Nps
Vout )
Vf
) 7p
LpClump
(eq. 24)
ǒ Ǔ+
0.2
0.25
190
10*6
1
100
)
0.25
19 ) 0.6
) 7p Ǹ190
10*6
200
10*12 + 7.75 ms (129 kHz)
When measured on the adapter we have: Tsw1 = 8.47 ms (Fsw1 = 118 kHz) corresponds to an ouput power of 9 W.
We calculate the timing capacitor value:
Ct
+
ICT(Tsw1 )
1.83
12
m)
+
20
We select Ct = 220 pF.
10*6(7.75 10*6 ) 12
1.83
10*6) + 216 pF
(eq. 25)
VI. Feedback
The feedback pin features an internal pull-up resistor
which connects to the optocoupler, as shown in Figure 18.
This pin is also connected to the internal valley comparators
that will select the operating valley according to the FB
voltage (see datasheet).
It is recommended to add a capacitor between FB pin and
GND pin of the controller. This capacitor has two
advantages: it offers a filtering action on the FB signal and
it forms with Rpullup a pole located at:
fp
+
2p
1
RpullupCpole
(eq. 26)
Rpullup
This pole will help you to stabilize the power supply.
+
VDD
5V
FB
GND
Cpole
Figure 18. FB Pin Features an Internal Pull-up
Resistor...
The pull-up resistor value is typically around 20 kW and
is referenced in the datasheet.
VII. VCC
The DAP013 includes a high voltage startup circuitry that
derives current from the bulk line to charge the VCC
capacitor. When the power supply is first connected to the
mains outlet, the internal current source is biased and
charges up the VCC capacitor. When the voltage on this VCC
capacitor reaches the VCCon level, the current source turns
off, reducing the amount of power being dissipated. At this
time, the controller is only supplied by the VCC capacitor,
and the auxiliary supply should take over before VCC
collapses below VCCmin. Figure 19 shows the internal
arrangement of this structure:
http://onsemi.com
11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet AND8331.PDF ] | |
Hoja de datos destacado
| Número de pieza | Descripción | Fabricantes |
| AND8331 | Quasi-Resonant CurrentMode Controller | ON Semiconductor |
| AND8331D | Quasi-Resonant CurrentMode Controller | ON Semiconductor |
| Número de pieza | Descripción | Fabricantes |
| SLA6805M | High Voltage 3 phase Motor Driver IC. |
 Sanken |
| SDC1742 | 12- and 14-Bit Hybrid Synchro / Resolver-to-Digital Converters. |
 Analog Devices |
|
DataSheet.es es una pagina web que funciona como un repositorio de manuales o hoja de datos de muchos de los productos más populares, |
| DataSheet.es | 2020 | Privacy Policy | Contacto | Buscar |