SCYW99143 Datasheet, PDF (28/35 Pages) ON Semiconductor – Universal High Voltage Control Block

CONFIDENTIAL AND PROPRIETARY
NOT FOR PUBLIC RELEASE
SCYW99143
Active OFF Version
1. Application start, remote off/on then AC line off –
Figure 51:
Application has been plugged into the mains at point A.
The HV pin receives rectified AC line voltage and the X2
sense pin charges up via external charge pump sensing
circuitry. As the high voltage is present on the HV pin the
startup current source is activated to charge Vcc capacitor to
VCC_bias. The BO block bias is enabled at this point (point
B). The Vcc_bias is maintained until the controller receives
BO−OK information from the BO block. When line voltage
is high enough to enable application operation the startup
current source continues to ramp up the Vcc voltage (point
C) up to Vcc_on threshold (point D) where PWM block
operation is enabled (PWM_ON signal). The voltage on
REM pin follows voltage on FB pin of slave controller (i.e.
REM pin is connected directly to FB opto−coupler).
The voltage on REM falls under VREM_off. It is mean
slave controller goes into skip mode. If the skip mode takes
too long time, Vcc crosses Vcc_off level due to internal
consumption (voltage on REM pin is still below VREM_off),
then the off−mode is detected (point E). The Vcc capacitor
is then internally discharged to 5V and all blocks are
disabled to reduce IC consumption to minimum needed
level. The Vcc pin remains unbiased during whole off−mode
operation. The X2 discharge and remote internal blocks
remain biased by the HV leakage current Istart_off (HV
current source is OFF) − consuming minimum power but
still keeping them operated.
FB opto−coupler is turned off and the voltage on REM pin
is slowly increased by internal pull−up current source
I_REM_bias. When the voltage on REM pin exceed
V_REM_on threshold at point F, Vcc capacitor is fully
discharged and the controller enables the HV startup current
source to built Vcc bias up again. The BO block bias is
enabled and PWM_ON signal is disabled at point G. This
Vcc_bias level (5 V) is maintained until the controller
receives BO_OK information from the BO block. If the line
voltage is high enough to enable operation the startup
current source continues to ramp up Vcc voltage (point H)
up to Vcc_on threshold (point I) where controller PWM is
enabled (PWM_ON signal). Application then operates
normally under any load conditions (e.g. standard PWM
operation, frequency foldback or skip mode).
Application has been unplugged from the mains at point
J. Let us consider the light load operation mode during this
event as a worst case for X2 capacitor discharging process.
The X2 capacitor stays charged on its actual voltage level
(line peak voltage in worst case). The X2 capacitor provides
DC bias to HV pin. The X2 sense input voltage starts to drop
in the same time because there is no AC voltage and charge
pump cannot transfer any charge to X2 pin. The 100 ms X2
timer is activated when the X2 input voltage drops below
internal X2 timer disable switch threshold voltage (Vth_X2)
point K. After the X2 timer elapses (point L), the PWM
block operation is disabled by pulling down the FB pin via
internal FB switch, the discharge switches (X2 and VCC)
are activated and X2 capacitor discharges via HV startup
current source until the X2 capacitor voltage drops to safe
level and internal bias is lost (point M). The over
temperature protection is active during discharging process
to overcome HV startup damage that would occur otherwise
under fault cases – like when X2 pin is not connected.
2. Application start, AC line dropout, low line off,
BO restart, AC line off – Figure 52:
This case is the same as for Active ON version except
levels of voltage on REM pin. The voltage on REM pin
follows voltage on FB pin of the slave controller
3. Off−mode operation – restart by primary remote
pull−up then AC line off – Figure 53:
The voltage on REM falls under VREM_off. The slave
controller goes to skip mode for long time. Vcc crosses
Vcc_off level due to internal consumption (voltage on REM
pin is still below VREM_off) and off−mode is initiated (point
A). As soon as the FB opto−coupler is turned off, the voltage
on REM pin is slowly increased by internal pull−up current
source I_REM_bias. When the voltage on REM pin exceed
V_REM_on threshold at point B, Vcc capacitor is fully
discharged and the controller enables the HV startup current
source to built Vcc bias for BO block and PWM_ON signal
is disabled (point C). Once the BO_OK information is
received (point D) the HV startup current source ramps up
to Vcc_on level (point E). PWM block operation is enabled
and the voltage on REM pin is decreasing by turning on of
FB opto−coupler. The application enters into off−mode
again when remote pin voltage crosses V_REM_off
threshold and Vcc falls under VCC_off (point F). Restart
occurs because REM pin is biased when FB opto−coupler is
turned off.
User unplugged application from the mains at point G.
The application was operating in off−mode at that time. The
X2 pin voltage drops because charge pump does not operate
and X2 timer disable switch is opened at point H (X2 timer
start counting). The X2 discharger is activated after X2 timer
elapses (point I).
4. Application start into short circuit, auto−recovery
restart, overloads then AC line off – Figure 54:
This case is the same as for Active ON version except
levels of voltage on REM pin. The voltage on REM pin
follows voltage on FB pin of the slave controller.
5. Application start, latch−off after 120 ms, AC line
restart – Figure 55:
This case is the same as for Active ON version except
levels of voltage on REM pin. The voltage on REM pin
follows voltage on FB pin of the slave controller.
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