High voltage temperature compensated foldback circuit
First Claim
Patent Images
1. A foldback circuit, comprising:
- a first conductor path including in series, an input terminal connectable to a direct current power supply, shutoff circuitry including transistor means, and an output terminal connectable to a load; and
control circuitry for the shutoff circuitry including an operational amplifier connected to operate the shutoff circuitry in response to a load demand which exceeds a current pass limit, to decrease the base current of the transistor means and cause the output current to foldback, said operational amplifier including a +V terminal connected to input voltage, a -V terminal connected to ground, an output terminal connected to the base of the transistor means, a noninverting input terminal, means powered by the input voltage and connected to provide a reference voltage at the noninverting input terminal which is less than but varies directly with the input voltage, an inverting input terminal, a conductor extending from a point in the first conductor path ahead of the shutoff circuitry to the inverting input terminal, and a foldback conductor extending from a point in the first conductor path between the shutoff circuitry and the output terminal to the inverting input terminal.
1 Assignment
0 Petitions
Accused Products
Abstract
A resistor (R3) reduces voltage between an input voltage and the emitter terminal of a series pass transistor pair (Q1, Q2). An operational amplifier (U1) compares this reduced voltage with a reference voltage that is less than, but varies with, the input voltage. The emitter voltage decreases until the current reaches a design limit. Then, a resistor senses the output voltage and pulls the operational amplifier'"'"'s input voltage down. This action causes the base current of the transistor pair (Q1, Q2) to decrease and the output current to foldback.
-
Citations
18 Claims
-
1. A foldback circuit, comprising:
-
a first conductor path including in series, an input terminal connectable to a direct current power supply, shutoff circuitry including transistor means, and an output terminal connectable to a load; and control circuitry for the shutoff circuitry including an operational amplifier connected to operate the shutoff circuitry in response to a load demand which exceeds a current pass limit, to decrease the base current of the transistor means and cause the output current to foldback, said operational amplifier including a +V terminal connected to input voltage, a -V terminal connected to ground, an output terminal connected to the base of the transistor means, a noninverting input terminal, means powered by the input voltage and connected to provide a reference voltage at the noninverting input terminal which is less than but varies directly with the input voltage, an inverting input terminal, a conductor extending from a point in the first conductor path ahead of the shutoff circuitry to the inverting input terminal, and a foldback conductor extending from a point in the first conductor path between the shutoff circuitry and the output terminal to the inverting input terminal. - View Dependent Claims (2, 3, 12)
-
-
4. A foldback circuit, comprising:
-
a first conductor path including in series, an input terminal connectable to a direct current power supply, shutoff circuitry including transistor means, and an output terminal connectable to a load; control circuitry for the shutoff circuitry including an operational amplifier connected to operate the shutoff circuitry in response to a load demand which exceeds a current pass limit, to decrease the base current of the transistor means and cause the output current to foldback, said operational amplifier including a +V terminal connected to input voltage, a -V terminal connected to ground, and an output terminal connected to the base of the transistor means, a first voltage divider powered by the input voltage and connected to provide a reference voltage at the noninverting input terminal of the operational amplifier which is less than but varies directly with the input voltage; a current limit establishing third resistor in the first conductor path in series between the input terminal and the shutoff circuitry, to establish an input voltage to the shutoff circuitry and establish the current limit of the circuit, and a second voltage divider connected to apply a fraction of the input voltage to the shutoff circuitry to the inverting input terminal of the operational amplifier. - View Dependent Claims (5, 6, 7, 8, 9, 10, 11)
-
-
13. A foldback circuit, comprising:
-
an input terminal connectable to a direct current power supply; an output terminal connectable to a load; shutoff circuitry between the input and output terminals, including transistor means; a current limit establishing resistor between the input terminal and the shutoff circuitry, to establish an input voltage to the shutoff circuitry on a current pass limit; control circuitry for the shutoff circuitry including an operational amplifier connected to operate the shutoff circuitry in response to a load demand which exceeds the current pass limit, to decrease the base current of the transistor means and cause the output current to fold back; a first voltage divider powered by the input voltage and connected to provide a reference voltage at the noninverting input of the operational amplifier which is lower than but varies directly with the input voltage; a second voltage divider powered by the emitter voltage and including an output junction connected to provide a voltage signal to the inverting input of the operational amplifier; and conductor means connected between the output junction of the second voltage divider and an output region of the circuit, said conductive path including an output sensing seventh resistor which senses the output voltage and pulls down the voltage to the inverting input of the operational amplifier when the load demand exceeds the current pass limit. - View Dependent Claims (14, 15, 16, 17, 18)
-
Specification