Appeal No. 1997-3996
Application 08/519,952
external reference clock signal oscillator which are synchronized in order to prevent beat noise in the
circuit (see appellant’s Figure 1 and pages 1 to 3 of the specification). As indicated in the specification
(see Figure 5 and page 1), power source circuits are known in the art to be used in portable electronic
devices for the purpose of stabilizing power source voltage and thus securing the stable operation of the
electronic devices. However, appellant’s invention of claims 1 to 18 provides several important
advantages as stated at the end of appellant’s specification (page 17):
In [appellant’s] power source circuit, the oscillating operation of the oscillator circuit is
synchronized with a reference clock signal of the external circuit. Because of this, the beat noise that is due
to the fact that the noise unremovable by smoothing circuits is not synchronized with the reference clock
signal can be removed. As a result, no deterioration of the external circuit characteristics, no erroneous
operation of the power source circuit, and improvement of the reliability of the power source circuit are
ensured. Further, since the oscillator circuit generates a triangle wave voltage, the triangle wave voltage
contains [sic] less noise by harmonic components than that of a saw-tooth wave voltage.
As further discussed, infra, we find that appellant’s admitted prior art (Figure 5 and pages 1 to
3 of the specification) and the applied references to Komori, Kikuchi, and Driscoll, whether taken
singly or in any combination thereof, fail to teach or suggest at least the feature of a power source circuit
having an external clock oscillator synchronized with a triangle wave oscillator for preventing beat noise
as defined in claims 1 to 18 on appeal.
Representative independent claim 1 is reproduced below:
1. A power source comprising:
an oscillator circuit for outputting a triangle wave voltage;
a pulse width control circuit for comparing the triangle wave voltage outputted from said
oscillator circuit with a reference voltage, and for controlling a width of a pulse signal to be outputted in
2
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