SM-SX100
– 19 –
14/23
17/20
IN
15/22
NF(+)
NF(–)
-1
-1
Integrator/Adder
Group
Comparator
Double width
conversion
Input Step
Figure 19-1
MODULATION 1-BIT CONVERSION CIRCUIT
Vs
1
2
4
Q
1
Q
2
C
R
i
i
C
GS
X
point
Y point
Diode prevents
i
2
from
returning to Vs.
Q2 is turned on,
and the holding
gate voltage is
gained from C.
It is necessary to
periodically
charge C.
Figure 19-2 BOOT STRAP CIRCUIT
• Protect circuit
When the protect circuit is activated, the speaker relays RLY107 and RLY108 and the power relay RLY106 are turned off, and
the function switch key is not received.
When the power switch is turned off, it is once reset.
For detection, the overcurrent detection circuit and the output offset detection circuit are provided and the relays and so on are
controlled by the microcomputer.
• Current detection section (Fig. 20-1)
If any overcurrent flows in R256, the potential difference will be generated both ends of R256 to supply it to Pins 2 and 3 of IC201.
If the output signal from Pin 1 of the output of IC201 is supplied to the comparator IC201 (Pins 5 to 7) (through the time constant
circuit) and reaches the level of the specified value or more, the comparator will be activated to set H at Pin 7. Then, the
transistors Q201 and Q202 will be turned on, and the signal of H level will be supplied to Pin 27 of the microcomputer IC904.
Thus, the protect will be activated.
• Offset detection section (Fig. 20-2)
If any potential difference is generated between the terminals of the speaker (L+ and L- as an example), the potential which
drives Q651 and Q653 will stand at the terminal connected section of the emitter of Q651 or the base of Q653, and either will
be turned on. (Pin 1 of IC651 as reference)
(If + level is established, Q653 will be turned on, and if - level is established, Q651 will be turned on.)
If Q651, Q653 or Q652, Q654 are turned on, Q201 will be activated like the said current detection to supply the signal of H level
to Pin 27 of the microcomputer IC904.
