US 8,890,630 B2Granted

Oscillator apparatus and method with wide adjustable frequency range

AssigneeCrane Electronics, Inc.

InventorRodney Alan Hughes

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Abstract

An oscillator formed from low cost discrete semiconductors and passive devices creates a linear periodic ramp of constant frequency with ramp slope based on an external voltage signal. Parameters are stable over a wide range of temperatures and variations of transistor parameters that normally degrade in extreme environments. The oscillator period can be phase and frequency synchronized to an external clock source over a wide range of frequencies. The oscillator ramp generator phase can be synchronized on a cycle by cycle basis for incorporation in power converters employing spread spectral EMI reduction techniques, multi-converter systems employing clock interleaving for distribution bus filter optimization, and resonant mode converters employing zero voltage switching techniques. Oscillator ramp rate is independent of frequency and can be synchronized to DC (inhibit) for use in ultra low power burst mode power conversion.

Claims15

Dependent claims

An oscillator, comprising:

a voltage input terminal to receive an input voltage signal;
a synchronizing signal input terminal to receive a synchronizing signal;
a ramp timing resistance;
a ramp timing capacitor which is charged by the input voltage signal through the ramp timing resistance;
an input voltage resistor divider network coupled to the voltage input terminal and which produces a discharge trigger reference voltage that is proportional to a voltage of the input voltage signal;
a comparator that compares a voltage across the ramp timing capacitor to the discharge trigger reference voltage;
a logic circuit that in response to a first state of a synchronization signal, discharges the ramp timing capacitor and that in response to a second state of the synchronization signal when the value of the voltage across the ramp timing capacitor is equal to the discharge trigger reference voltage, delays a discharging of the ramp timing capacitor, wherein at least the comparator and the logic circuit are each formed of a number of discrete semiconductor components;
a control transistor;
a discharge controlling capacitor;
a discharge termination transistor;
and
a discharge controlling transistor, the control transistor responsive to at least an output of the comparator to selectively charge the discharge controlling capacitor from the voltage input terminal, the discharge controlling capacitor coupled to selectively cause the discharge controlling transistor and the discharge termination transistor to discharge the ramp timing capacitor.

9 more elements

A method of operating an oscillator, the method comprising:

receiving an input voltage signal at a voltage input terminal;
receiving a synchronizing signal at a synchronizing signal input terminal;
charging a ramp timing capacitor via the input voltage signal through a ramp timing resistance;
producing a discharge trigger reference voltage that is proportional to a voltage of the input voltage signal;
comparing a voltage across the ramp timing capacitor to the discharge trigger reference voltage, wherein comparing the voltage across the ramp timing capacitor to the discharge trigger reference voltage includes supplying the discharge trigger reference voltage to a first transistor of a differential pair of transistors and supplying the voltage across the ramp timing capacitor to a second transistor of the differential pair of transistors;
determining whether to trigger discharging of the ramp timing capacitor when the value of the voltage across the ramp timing capacitor is equal to the discharge trigger reference voltage, wherein determining whether to trigger discharging of the ramp timing capacitor when the value of the voltage across the ramp timing capacitor is equal to the discharge trigger reference voltage includes supplying the synchronization signal to a logic network comprising a synchronization capacitor, a first synchronization diode and a second synchronization diode, triggering the discharging of the ramp timing capacitor via the first synchronization diode in response to a first synchronization state and suppressing triggering of the discharging of the ramp timing capacitor via the second synchronization diode in response to a second synchronization state;
in response to a value of the voltage across the ramp timing capacitor being equal to the discharge trigger reference voltage, discharging the ramp timing capacitor if a state of the synchronization signal indicates synchronization and delaying discharging of the ramp timing capacitor if the state of the synchronization signal does not indicate synchronization;
and
in response to the state of the synchronization signal indicating synchronization while the voltage across the ramp timing capacitor is less than the discharge trigger reference voltage, discharging the ramp timing capacitor.

6 more elements

Dependencies are inferred from the claim text.

Facts

Application: 13/185,152Filed 18 Jul 2011
Published: US 2013/0021108 A124 Jan 2013
Granted: 18 Nov 2014
Term ends: Not estimatedThe source records don’t support an estimate.

Classification10 codes

H03B 5/24
With frequency-determining element comprising resistance and either capacitance or inductance, e.g. phase-shift oscillator: active element in…
H02M 3/156
Using semiconductor devices only: with automatic control of output voltage or current, e.g. switching regulators
H03B 5/04
Details: modifications of generator to compensate for variations in physical values, e.g. power supply, load, temperature
H03K 3/0231
By the use of differential amplifiers or comparators, with internal or external positive feedback: astable circuits