US 5,510,753 AGranted

Composite bridge amplifier with output overload and thermal protection

AssigneeBlade Technologies Inc.

InventorJohn B. French

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Abstract

A composite bridge amplifier has four output transistors in a bridge configuration. The transistor control terminals (gates or bases) are controlled by an input signal which is amplified in a phase splitter and voltage gain stage. The output terminals of the transistors receive a power signal which varies with the input signal at a level sufficient to maintain headroom above the output signal but to reduce power dissipation in the transistors. The power signal is produced by a switch connected between a floating power supply and a filter and operated at e.g. 200 kHz. The switch is operated by a pulse width modulated (pwm) signal derived from the absolute value of the input signal. A proportional integral controller is coupled between the filter output and the pulse width modulator for closed loop feedback. The output is aligned with the input signal by a phase shifter connected to the controller. Since there is no time delay in the input signal (i.e. audio) path, high performance is achieved at reduced cost. For improved high frequency performance, the amplifier includes a peak detector circuit for tracking a high frequency input signal and compensating the pwm signal. The amplifier also features thermal overload protection and output current overload protection circuits which protect the output stage by reducing the headroom. Because the protection circuits do not "clip" the output signal, the effect to the listener is minimized.

Claims20

Dependent claims

An amplifier for amplifying an input signal, said amplifier comprising:

(a) first, second, third and fourth amplifier means each having first and second power terminals and a control terminal;
said amplifier means being connected in a bridge configuration, said first and second amplifier means each having their first power terminals coupled together and to a first power input terminal, said third and fourth amplifier means each having their first power terminals coupled together and to a second power input terminal;
(c) the second power terminals of said first and third amplifier means being coupled together and to a first output terminal, the second power terminals of said second and fourth amplifier means being coupled together and to a second output terminal, said first and second output terminals being adapted to being connected to a load;
(d) an input terminal for said input signal, and a control circuit coupled between said input terminal and said control terminals of said first to fourth amplifier means to operate alternately said first and third amplifier means and then said second and fourth amplifier means, to direct current from said first power input terminal through said first amplifier means, said first output terminal, said load, said second output terminal, said fourth amplifier means and said second power input terminal, and then to direct current from said first power input terminal through said second amplifier means, said second output terminal, said load, said first output terminal, said third amplifier means and said second power input terminal;
(e) modulating means coupled to said input terminal for producing a modulated signal having modulation dependent on said input signal;
(f) power supply means, and filter means for said power supply means;
(g) switch means having a control input, said switch means coupling said power supply means to said filter means, said filter means being coupled to said first and second power input terminals;
(h) said modulating means being coupled to said control input of said switch means for controlling said switch means to produce at said power input terminals a power signal dependent on said input signal;
and
(i) said modulating means including means for producing a power control signal for controlling said switch means and phase shifter means for phase shifting said power control signal so that said power signal is shifted for alignment with said input signal.

7 more elements

An amplifier for amplifying an input signal, said amplifier comprising:

(a) first, second, third and fourth amplifier means each having first and second power terminals and a control terminal;
(b) said amplifier means being connected in a bridge configuration, said first and second amplifier means each having their first power terminals coupled together and to a first power input terminal, said third and fourth amplifier means each having their first power terminals coupled together and to a second power input terminal;
(c) the second power terminals of said first and third amplifier means being coupled together and to a first output terminal, the second power terminals of said second and fourth amplifier means being coupled together and to a second output terminal, said first and second output terminals being adapted to being connected to a load;
(d) an input terminal for said input signal, and a control circuit coupled between said input terminal and said control terminals of said first to fourth amplifier means to operate alternately said first and third amplifier means and then said second and fourth amplifier means, to direct current from said first power input terminal through said first amplifier means, said first output terminal, said load, said second output terminal, said fourth amplifier means and said second power input terminal, and then to direct current from said first power input terminal through said second amplifier means, said second output terminal, said load, said first output terminal, said third amplifier means and said second power input terminal;
(e) modulating means coupled to said input terminal for producing a modulated signal having modulation dependent on said input signal;
(f) power supply means, and filter means for said power supply means;
(g) switch means having a control input, said switch means coupling said power supply means to said filter means, said filter means being coupled to said first and second power input terminals;
(h) said modulating means being coupled to said control input of said switch means for controlling said switch means to produce at said power input terminals a power signal dependent on said input signal;
and
(i) overload current protection means including sensor means coupled to one of said amplifier means for sensing the current flowing in said amplifier means, said sensor means comprising averaging means for producing an output signal corresponding to the average value of said sensed current and peak detector means for producing an output signal corresponding to the peak value for said sensed current, and said averaging means including threshold means for producing a current overload signal when said averaged output signal exceeds a first pre-determined threshold, and said peak detector means including said threshold means for producing a current overload signal when said peak output signal exceeds a second pre-determined threshold, and divider means coupled to said modulating means for proportionately reducing said power control signal in response to said current overload signal.

7 more elements

An amplifier for amplifying an input signal, said amplifier comprising:

(a) first, second, third and fourth amplifier means each having first and second power terminals and a control terminal;
(b) said amplifier means being connected in a bridge configuration, said first and second amplifier means each having their first power terminals coupled together and to a first power input terminal, said third and fourth amplifier means each having their first power terminals coupled together and to a second power input terminal;
(c) the second power terminals of said first and third amplifier means being coupled together and to a first output terminal, the second power terminals of said second and fourth amplifier means being coupled together and to a second output terminal, said first and second output terminals being adapted to being connected to a load;
(d) an input terminal for said input signal, and a control circuit coupled between said input terminal and said control terminals of said first to fourth amplifier means to operate alternately said first and third amplifier means and then said second and fourth amplifier means, to direct current from said first power input terminal through said first amplifier means, said first output terminal, said load, said second output terminal, said fourth amplifier means and said second power input terminal, and then to direct current from said first power input terminal through said second amplifier means, said second output terminal, said load, said first output terminal, said third amplifier means and said second power input terminal;
(e) modulating means coupled to said input terminal for producing a modulated signal having modulation dependent on said input signal;
(f) power supply means, and filter means for said power supply means;
(g) switch means having a control input, said switch means coupling said power supply means to said filter means, said filter means being coupled to said first and second power input terminals;
(h) said modulating means being coupled to said control input of said switch means for controlling said switch means to produce at said power input terminals a power signal dependent on said input signal;
and
(i) thermal overload protection means having a temperature sensor coupled to one of said amplifier means and having means for producing a temperature output signal in response to a change in temperature in said amplifier means, and means coupled to said temperature sensor for producing a thermal protection signal when said temperature output signal exceeds a first pre-determined threshold, and divider means coupled to said modulating means and including means responsive to said thermal protection signal for proportionately reducing the magnitude of said power control signal.

7 more elements

Dependencies are inferred from the claim text.

Facts

Application: 08/345,728Filed 22 Nov 1994
Priority: CA 210975523 Nov 1993
Granted: 23 Apr 1996
Term ends: Not estimatedThe source records don’t support an estimate.

Classification5 codes

H03F 3/217
With semiconductor devices only: class D power amplifiers; Switching amplifiers
H03F 1/0227
By using a signal derived from the input signal: using supply converters
H03F 1/52
Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements: circuit…
H03F 3/3081
Single-ended push-pull [SEPP] amplifiers ; Phase-splitters therefor: duplicated single-ended push-pull arrangements, i.e. bridge circuits