Oscillation circuit

Patent metadata

Field	Value
Publication number	US-10348189-B2
Application number	US-201715428333-A
Country	US
Kind code	B2
Filing date	Feb 9, 2017
Priority date	Feb 10, 2016
Publication date	Jul 9, 2019
Grant date	Jul 9, 2019

Abstract

An oscillation circuit includes: a periodic signal generator which generates a periodic signal whose frequency varies; and a clock generator which generates a clock signal having a frequency commensurate with the frequency of the periodic signal.

First claim

What is claimed is:

1. An oscillation circuit comprising:
a periodic signal generator configured to generate a periodic signal of which a frequency varies; and
a clock generator configured to generate a clock signal having a frequency commensurate with a value of the periodic signal,
wherein the frequency of the periodic signal varies periodically by first decreasing from a maximum value via a center value to a minimum value and then increasing from the minimum value via the center value to the maximum value, and
a frequency at which the frequency of the periodic signal is varied periodically varies.

2. The oscillation circuit of claim 1 , wherein the periodic signal is a triangular wave signal.

3. The oscillation circuit of claim 2 , wherein the triangular wave signal has a waveform that swings up and down about a predetermined level as a center.

4. The oscillation circuit of claim 1 , wherein the clock generator includes:
a ring oscillator having
an odd number of inverters connected in a ring form and
capacitors connected to output terminals of the inverters respectively; and

a variable current feeder configured to feed the inverters with a current commensurate with the periodic signal.

5. The oscillation circuit of claim 4 , wherein the variable current feeder includes:
a current-output DAC configured to subject the periodic signal to digital-to-analog conversion to output a current; and
a current mirror configured to mirror the current output from the current-output DAC to feed the current to the inverters.

6. The oscillation circuit of claim 1 , wherein the clock generator includes:
a current-output DAC configured to subject the periodic signal to digital-to-analog conversion to output a current; and
a capacitor configured to be charged by the current output from the current-output DAC;
a switch configured to be turned ON and OFF to charge and discharge the capacitor; and
a comparator configured to be fed with a voltage of the capacitor and a reference voltage.

7. A semiconductor device comprising:
the oscillation circuit of claim 1 for generating a clock signal, wherein
the semiconductor device generates a switching signal for a switching power supply device by using the clock signal.

8. A display device comprising:
a switching power supply device including the semiconductor device of claim 7 ; and
a display configured to be supplied with electric power from the switching power supply device.

9. The display device of claim 8 , wherein the display device is for vehicle-mounted use.

10. The semiconductor device of claim 7 , wherein the semiconductor device is for vehicle-mounted use.

11. The oscillation circuit of claim 1 , wherein the oscillation circuit is for vehicle-mounted use.

Assignees

• Rohm Co Ltd

Inventors

• Takenaka Seiji

Classifications

• H03K3/0315

  Ring oscillators · CPC title

• H02M1/44 Primary

  Circuits or arrangements for compensating for electromagnetic interference in converters or inverters · CPC title

• H03K4/50

  in which a sawtooth voltage is produced across a capacitor · CPC title

• H03B23/00

  Generation of oscillations periodically swept over a predetermined frequency range (angle-modulating circuits in general H03C3/00) · CPC title

• H03K3/84 Primary

  Generating pulses having a predetermined statistical distribution of a parameter, e.g. random pulse generators · CPC title