Protection circuit for regulated power supplies

Claim 2

In a voltage regulated switching power supply for operation from a source of direct current voltage having voltage sensing means for developing an error voltage in response to the output voltage of the supply, and pulse width control means for varying the switching duty cycle of the supply in response to the error voltage in a manner tending to maintain said output voltage substantially constant, a protection system comprising; a source of reference potential independent of said output voltage, and clamping means connected to said voltage sensing means and to said reference potential source for clamping said error voltage to said reference potential when the output of said supply is below a predetermined level for maintaining said error voltage within a predetermined voltage range to maintain the duty cycle of the supply within predetermined limits.

Claim 3

A system as recited in claim 1 wherein said clamping means includes a diode having first and second terminals, said first terminal being connected to said source of reference potential and said second terminal being connected to said voltage sensing means.

Claim 4

A system as recited in claim 2 wherein said source of reference potential is said source of direct current potential.

Claim 5

A switching mode power supply for operation from a source of direct current potential comprising; oscillator means for providing a variable pulse width signal, means connected to said oscillator means for utilizing said variable pulse width signal to provide an output voltage in response thereto, voltage sensing means connected to said utilization means for sensing the magnitude of said output voltage to provide an error voltage in accordance therewith, means connecting said voltage sensing means to said oscillator means for varying the pulse width of the signal therefrom in accordance with the magnitude of said error voltage in a manner tending to maintain said output voltage substantially constant, and limiting means connected to said voltage sensing means for maintaining said error voltage at a predetermined amplitude when said output voltage drops below a predetermined level, thereby maintaining the pulse width of said oscillator means within a predetermined range.

Claim 6

A switching mode power supply for operation from a source of direct current potential comprising; oscillator means for providing a variable pulse width signal, means connected to said oscillator means for utilizing said variable pulse width signal to provide an output voltage in response thereto, voltage sensing means connected to said utilization means for sensing the magnitude of said output voltage to provide an error voltage in accordance therewith, means connecting said voltage sensing means to said oscillator means for varying the pulse width of the signal therefrom in accordance with the magnitude of said error voltage in a manner tending to maintain said output voltage substantially constant, and limiting means connected to said voltage sensing means for maintaining said error voltage at a predetermined amplitude when said output voltage drops below a predetermined level, thereby maintaining the pulse width of said oscillator means within a predetermined range.

Claim 7

A power supply as recited in claim 4 wherein said limiting means includes a source of reference potential independent of said output voltage and a diode having first and second terminals, said first terminal being connected to said source of direct current potential and said second terminal being connected to said voltage sensing means.

Claim 8

A power supply as recited in claim 5 wherein said utilization means includes a transformer and transistor switch means having input, output and common termInals, and wherein said transformer is connected to said input terminal.

Claim 9

A power supply as recited in claim 5 wherein said source of reference potential includes said source of direct current potential.

Claim 10

A switching mode power supply including in combination, means for producing variable width pulses, said variable width pulse producing means being responsive to voltages applied thereto for varying the width of the pulses, output circuit means for providing voltage to a load, switching means responsive to said variable width pulse producing means connected to said output circuit means for intermittently applying power thereto in response to said variable width pulses, energy storage means connected to said variable width pulse producing means and said switch means for receiving said variable width pulses and storing the energy contained therein and transferring said energy to said switch means for operation thereof, feedback means connected to said output circuit means and to said variable width pulse producing means for varying the width of said pulses in response to said output voltage in a manner tending to maintain said output voltage substantially constant, and means connected to said variable width pulse producing means for maintaining the width of said pulses within a predetermined range containing sufficient energy for proper operation of said switch means when the voltage provided by said output circuit means is below a predetermined level.

Claim 11

A switching mode power supply including in combination, means for producing variable width pulses, said variable width pulse producing means being responsive to voltages applied thereto for varying the width of the pulses, output circuit means for providing voltage to a load, switching means responsive to said variable width pulse producing means connected to said output circuit means for intermittently applying power thereto in response to said variable width pulses, energy storage means connected to said variable width pulse producing means and said switch means for receiving said variable width pulses and storing the energy contained therein and transferring said energy to said switch means for operation thereof, feedback means connected to said output circuit means and to said variable width pulse producing means for varying the width of said pulses in response to said output voltage in a manner tending to maintain said output voltage substantially constant, and means connected to said variable width pulse producing means for maintaining the width of said pulses within a predetermined range containing sufficient energy for proper operation of said switch means when the voltage provided by said output circuit means is below a predetermined level.

Claim 12

A power supply as recited in claim 8 wherein said storage means is an inductive storage means.

Claim 13

A power supply as recited in claim 9 wherein said storage means is a transformer.

Claim 14

A power supply as recited in claim 8 wherein said means for maintaining the width of said pulses includes a source of reference potential and a diode having first and second terminals, said first terminal being connected to said reference potential source, and said second terminal being connected to said variable pulse width producing means for applying a voltage related to said reference potential to said variable pulse width producing means to control the width of said pulses.