Circuit Descriptions, List of Abbreviations, and IC Data Sheets FM23, FM24, FM339.EN 135
compared to the L4973V that is used in the FM23 and Note: The POK signal is fed to buffer 7366, together with the
FM24."8V6_UNDER_VOLTAGE" and "SWITCH" sensing. The output
All these circuits use double diodes per voltage, in order create of this buffer, the POWER_OK line, will follow the inputs.
a symmetrical load for the transformer.
Operation
Audio Supply
This is a "floating" symmetrical supply (?14.5 V) derived from V_s Protection
V_s via transformer 5290. Because this voltage is tightly Detection of over- or under voltage on V_S_UNSW by
coupled to the V_s voltage, this voltage varies considerable, comparators IC7308-A and -B. If this voltage exceeds certain
between 11 V (max. load, V_s = 70 V) and 20 V (min. load, V_s levels (set via voltage dividers), the protection will activate the
= 90 V).Power OK (POK, active "low"), which will shut down the set.
The Audio ground is connected to the normal secondary
ground, with a capacitor (C2290) and a resistor (R3292) in
V_a Protection
parallel, in order to suppress spurious oscillations.
Detection of over- or under voltage on V_a by comparators
IC7308-C and -D. If this voltage exceeds certain levels (set via
9.2.8 Power Supply Protections (Diagram P3)voltage dividers), the protection will activate the Power OK
(POK, active "low"), which will shut down the set.
1450Aux. outputs
1460
MAINS INVac_SWMAIN+5V / VccV_cc Protection
SUPPLY
Vs_UNSWVsDetection of over- or under voltage on V_cc (+5 V) by
SUPPLY_ON OFFcomparators IC7330-A and -B. If this voltage exceeds certain
+9V_STBY_SW
STANDBY&levels (set via voltage dividers), the protection will activate the
DC_PROTPower OK (POK, active "low"), which will shut down the set.
TEMP. ERROR>1LATCHLATCH
+3V3 Protection
OVP
(Vs_unsw, Va,+5V,+3V3)Detection of over- or under voltage on the +3V3 voltage by
>1POWER_OKcomparators IC7330-C and -D. If this voltage exceeds certain
UVP&
(Vs_unsw, Va,+5V,+3V3)levels (set via voltage dividers), the protection will activate the
Vsago
Power OK (POK, active "low"), which will shut down the set.
Discharge
Vs_UNSW OK&
OVP protection
This line detects, if one of the above mentioned voltage
Vs_UNSWVaprotections is an over-voltage protection. Therefore, this works
orSUPPLYVa
Vac_SWin combination with the above-mentioned under/over voltage
CL16532099_012.eps
OFF180901protections.
Figure 9-13 Protections
Latch Protection
When an OVP-, DC-, or Temperature protection occurs,
In general, all efforts are taken, to make a safe power supply. thyristor 6348 is fired and the LATCH signal is made "low". This
Therefore, all major outputs are monitored with respect to over- signal will switch "off" the main supply and prevents that the
and/or under voltage. All protections are handled by hardware. supply is switched "on" again, as long as the protection is
The software only monitors the hardware to generate error active.
codes for service. In addition, the V_cego signal can activate the LATCH signal
Via I2C, errors of the power supply are transmitted to the (via TS7352 and 7348), but this is temporarily. This is done for
microprocessor on the SCAVIO panel. If an error occurs, the correct start-up behaviour.
POWER_OK line will change from "high" to "low". The errors
are transmitted to the microprocessor, on the following ports
DC Protection
and pin numbers of the I/O expander PCF8574AT (item 7370):
Detection of a DC voltage on the audio amplifier outputs. If a
DC voltage is detected, TS7362 will activate the Power OK
Table 9-2 IC7370 Inputs(POK, active "low"), which will shut down the set.
PinNameDescriptionTemperature Protection
4V_sDetection of under- or overvoltage on V_sFM23 and FM24: Detection of the temperature (via PTC
5V_aDetection of under- or overvoltage on V_a3368) in the power supply by comparator IC7366-A. If this
voltage exceeds a certain level (set via voltage dividers),
6+5VDetection of under- or overvoltage on +5V
the protection will activate the Power OK (POK), which will
7+3V3Detection of under- or overvoltage on
shut down the set.
+3V3
FM33: via an I2C temp sensor IC7372. This LM75A is a
9OVPDetection of overvoltage on V_s, V_a,temperature-to-digital converter using an on-chip
+5V or +3V3temperature sensor, and provides an Over-temp Shutdown
10SwitchDetection of functional switch(OS) output. It communicates via I2C. The device is
11 DC_PROT Detection of DC_PROT going highpowered-up in normal operation mode with the OS in
comparator mode, temperature threshold of 80 °C and
12TEMPDetection of over temp. inside power sup-
hysteresis of 75 °C, so that it can be used as a stand-alone
ply
thermostat with those pre-defined temperature set points.
This POWER_OK signal is connected to an interrupt pin of the
OTC, in order to be read as fast as possible. This is very
important in case of a time-limited error like over-voltage. After
detection of the error, the control system will log the error in
NVM, and transmit the first occurrence back to the power
supply through the I2C bus. |
ACEC
