Regulated power supply circuit permitting an adjustment of output current when the output thereof is grounded

• US 5,642,034 A
• Filed: 12/21/1994
• Issued: 06/24/1997
• Est. Priority Date: 12/24/1993
• Status: Expired due to Fees

• Current Assignee: NEC Electronics Corporation (Renesas Electronics Corporation)
• Original Assignee: NEC Corporation
• Inventors: Amano, Nobutaka
• Primary Examiner(s): Sterrett, Jeffrey L.
• Application Number:
  US08/361,217
• Time in Patent Office: 916 Days
• Field of Search: 323/273, 323/275, 323/276, 323/277, 323/279
• US Class Current: 323/277
• CPC Class Codes: G05F 1/573 with overcurrent detector

Abstract

In a regulated power supply circuit, a "J characteristic curve" is obtained between an output current and an output voltage. Moreover, the output current is minimized in a grounded state in which the output terminal is grounded to minimize heat dissipation so as to facilitate circuit integration. Between the input and output terminals, there are connected an output-stage transistor and a current sense resistor in series. A voltage sense circuit senses voltage between an output terminal of the transistor and a ground terminal. The current sense circuit senses the output current by the current sense resistor. The transistor has a base terminal connected to output terminals of the voltage and current sense circuits, respectively. In this configuration, when the output terminal is grounded, the output current is set independently of a current value sensed at occurrence of an excess current. This consequently lowers the power consumption of the regulated voltage circuit in the grounded state.

Claims

1. A regulated power supply circuit for adjusting an output current when an output terminal of the circuit is grounded, the circuit comprising:

current control means, disposed between an input terminal of the circuit and said output terminal and provided with two control input terminals, for controlling a current flowing through said input and output terminals of the circuit;

current sense means, inserted between a downstream end of said current control means and said output terminal, for sensing said current and supplying a resultant signal to a first one of said two control terminals; and

voltage sense means for comparing a voltage between said output terminal of said circuit and a ground potential (GND) with a reference voltage and supplying an error signal to a second one of said two control input terminals,

wherein said current sense means includes comparator means for sensing said current as a voltage applied to input terminals thereof; and

the circuit further comprises a current source for causing the current to flow through a circuit including one of said input terminals of said comparator means so that the potential difference between said input terminals of said comparator means does not become zero even when the output current of the regulated power supply circuit is equal to zero.

2. A regulated power supply circuit which permits an adjustment of output current when an output terminal of the circuit is grounded, the circuit comprising:

current control means, disposed between an input terminal of the circuit and said output terminal and provided with two control input terminals, for controlling a current flowing through said input and output terminals of the circuit;

current sense means, inserted between a downstream end of said current control means and said output terminal, for sensing said current and supplying a resultant signal to a first one of said two control terminals; and

voltage sense means for comparing a voltage between said output terminal of said circuit and a ground potential (GND) with a reference voltage and supplying an error signal to a second one of said two control input terminals, wherein;

said current sense means includes comparator means for sensing said current as a voltage applied to input terminals thereof; and

said comparator means includes bias means for providing said input terminals of said current sense means with a bias voltage so that the potential difference between said input terminals of said comparator means does not become zero even when the output current of the regulated power supply circuit is equal to zero.

3. A regulated power supply circuit comprising:

current control means disposed between an input terminal and an output terminal, said current control means having a control terminal;

current sense means arranged between said output terminal and an output terminal of said current control means, said current sense means having a sense terminal; and

voltage sense means for sensing a voltage between an output terminal of said current control means and a ground potential (GND), said voltage sense means having a sense terminal,

said sense terminal of said current sense means, said sense terminal of said voltage sense means, and said control terminal of said current control means being connected to each other,

wherein a predetermined bias current flows through said current control means when said output terminal is grounded to the GND potential.