Isolation amplifier

An electrical signal isolator comprising:

• input and output sections;
• a transformer coupling said input and output sections;
• a first amplifier forming part of said input section to receive an input signal;
• a second amplifier forming part of said output section to develop an output signal;
• means for generating in said transformer an alternating pulse signal comprising a power pulse followed by a flyback pulse;
• first winding means for said transformer comprising at least one multi-turn winding;
• a first diode/capacitor half-wave rectifier/filter circuit forming part of said input section and coupled to said multi-turn winding;
• said first rectifier/filter circuit being poled to respond to said flyback pulse;
• means coupling said first amplifier to said first half-wave rectifier/filter circuit to effect modulation of the magnitude of said flyback pulse in accordance with said input signal;
• a second diode/capacitor half-wave rectifier/filter circuit forming part of said input section and coupled to said winding means;
• said second rectifier/filter circuit being poled to respond to said power pulse to produce a d-c power voltage for said first amplifier;
• a third diode/capacitor half-wave rectifier/filter circuit forming part of said input section and coupled to said multi-turn winding;
• said third rectifier/filter circuit being poled to respond to said flyback pulse to develop a d-c negative feedback signal for said first amplifier;
• a fourth diode/capacitor half-wave rectifier/filter circuit forming part of said input section and coupled to said first winding means;
• said fourth rectifier/filter circuit being poled to respond to said power pulse to produce a d-c level-shifting voltage;
• means connecting said level-shifting voltages in series with said feedback signal to provide a feedback voltage level within the operating range of said first amplifier;
• second winding means for said transformer separate from said first winding means;
• and
• diode/capacitor rectifier means coupled to said second winding means to develop an input signal for said second amplifier.

In an electrical signal isolator of the type including input and output sections, a transformer coupling said input and output sections, a first amplifier forming part of said input section to receive an input signal, a second amplifier forming part of said output section to develop an output signal, means for generating in said transformer an alternating pulse signal comprising a power pulse followed by a flyback pulse, that improvement comprising:

• a first multi-turn winding for said transformer;
• a first series-connected diode-capacitor rectifier/filter circuit connected across said first winding and poled to respond to said flyback pulse;
• means coupling said first amplifier to said first rectifier circuit to effect modulation of the magnitude of said flyback pulse in accordance with said input signal;
• a second series-connected diode-capacitor rectifier/filter circuit connected across said first winding and poled to respond to said power pulse to produce a d-c power voltage for said first amplifier;
• a third series-connected diode-capacitor rectifier/filter circuit connected across said first winding and poled to respond to said flyback pulse to develop a d-c negative feedback signal for said first amplifier;
• a second multi-turn winding for said transformer separate from said first winding;
• a fourth series-connected diode-capacitor rectifier/filter circuit connected across said second winding and poled to respond to said power pulse to produce a d-c level-shifting voltage;
• means connecting said level-shifting voltage in series withsaid feedback signal to provide a feedback voltage having a level within the operating range of said first amplifier;
• a third multi-turn winding for said transformer identical to said first winding;
• a fifth series-connected diode-capacitor rectifier/filter circuit connected across said third winding and poled to respond to said flyback pulse to produce a d-c modulation signal;
• a fourth multi-turn winding for said transformer identical to said second winding;
• a sixth series-connected diode-capacitor rectifier/filter circuit connected across said fourth winding to produce a d-c bias signal;
• and
• means connecting said d-c modulation signal in series with said bias signal to produce an input signal for said second amplifier.

In an electrical signal isolator of the type including input and output sections, a transformer having first and second winding means coupling said input and output sections, a first amplifier forming part of said input section to receive an input signal, a second amplifier forming part of said output section to develop an output signal, means for generating in said transformer winding means an alternating pulse signal comprising a power pulse followed by a flyback pulse;

• that improvement in such an isolator comprising:
• first diode-capacitor rectifier means coupled to said first winding means and poled to respond to said flyback pulse to produce a corresponding d-c voltage;
• means connecting said corresponding d-c voltage to a supply terminal of said first amplifier to provide for modulation of the magnitude of said flyback pulse in accordance with the amount of supply current drawn by said first amplifier;
• second diode-capacitor rectifier means coupled to said first winding means to develop a d-c negative feedback signal for said first amplifier;
• and
• third diode-capacitor rectifier means coupled to said second winding means to produce an input signal for said second amplifier corresponding to the modulated magnitude of said flyback pulse.

In an electrical signal isolator of the type including input and output sections, a transformer coupling said input and output sections, a first amplifier forming part of said input section to receive an input signal, a second amplifier forming part of said output section to develop an output signal;

• that improvement in such isolator comprising:
• a transistor having a base, collector, and emitter;
• first winding means for said transformer coupled between said base and said emitter;
• second winding means for said transformer including at least one multi-turn winding coupled between said emitter and said collector;
• d-c power supply means coupled to said emitter and said one multi-turn winding to energize said transistor and said windings to provide a free-running inductance-coupled blocking oscillator producing a power pulse followed by flyback pulse;
• third winding means for said transformer;
• first diode-capacitor rectifier means coupled to said third winding means and poled to respond to said flyback pulse;
• means connecting said first amplifier to said first rectifier means to effect modulation of the magnitude of said flyback pulse in accordance with the input signal applied to said first amplifier;
• second diode-capacitor rectifier means coupled to said third winding means to develop a d-c negative feedback signal for said first amplifier;
• third diode-capacitor rectifier means coupled to said third winding means and poled to respond to said power pulse to produce a d-c power supply voltage for said first amplifier;
• and
• fourth diode-capacitor rectifier means coupled to said second winding means to produce an input signal for said second amplifier corresponding to the modulated magnitude of said flyback pulse.

In an electrical signal isolator of the type including input and output sections, a transformer having first and second winding means coupling said input and output sections, a first amplifier forming part of said input section to receive an input signal, a second amplifier forming part of said output section to develop an output signal, means for generating in said transformer winding means an alternating pulse signal comprising a power pulse followed by a flyback pulse;

• a diode-capacitor circuit coupled to one of said winding means for modulating the magnitude of said flyback pulse in accordance with the input signal applied to said first amplifier;
• the improved method of modulating said flyback pulse comprising the steps of:
• developing a d-c voltage on the capacitor of said diode-capacitor circuit responsive to said flyback pulse;
• and
• altering the magnitude of said flyback pulse by drawing from said d-c voltage a supply current for said amplifier which varies in accordance with said applied input signal.