International Rectifier IRAUDAMP4, Руководство пользователя

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RD-0617
or have them separated by at least 25 kHz. With the installed components, it is possible
to change the self-oscillating frequency from about 160 kHz up to 600 kHz.
Potentiometers for adjusting self-oscillating frequency
R29P
Switching frequency for CH1*
R30P Switching frequency for CH2*
*Adjustments have to be done at an idling condition with no signal input.
Switches and Indicators
There are three different indicators on the reference design:
– An orange LED, signifying a fault / shutdown condition when lit.
– A green LED on the motherboard, signifying conditions are normal and no fault
condition is present.
– A green LED on the daughter board, signifying there is power.
There are three switches on the reference design:
– Switch S1 is a trip and reset push-button. Pushing this button has the same effect of
a fault condition. The circuit will restart about three seconds after the shutdown
button is released.
– Switch S2 is an internal clock-sync frequency selector. This feature allows the
designer to modify the switching frequency in order to avoid AM radio interference.
With S3 is set to INT, the two settings “H” and “L” will modify the internal clock
frequency by about 20 kHz to 40 kHz, either higher “H” or lower “L.” The actual
internal frequency is set by potentiometer R113 - “INT FREQ.”
– Switch S3 is an oscillator selector. This three-position switch is selectable for
internal self-oscillator (middle position – “SELF”), or either internal (“INT”) or
external (“EXT”) clock synchronization.
Switching Frequency Lock / Synchronization Feature
For single-channel operation, the use of the self-oscillating switching scheme will yield
the best audio performance. The self-oscillating frequency, however, does change with
the duty ratio. This varying frequency can interfere with AM radio broadcasts, where a
constant-switching frequency with its harmonics shifted away from the AM carrier
frequency, is preferred. In addition to AM broadcasts, multiple channels can also reduce
audio performance at low power, and can lead to increased residual noise. Clock
frequency locking/synchronization can address these unwanted characteristics.
Please note that the switching frequency lock / synchronization feature is not possible for
all frequencies and duty ratios, and operates within a limited frequency and duty-ratio
range around the self-oscillating frequency (Figure 5).