Charging apparatus and current/voltage detector for use therein

• US 5,850,137 A
• Filed: 12/02/1996
• Issued: 12/15/1998
• Est. Priority Date: 01/29/1996
• Status: Expired due to Term

• Current Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Original Assignee: Fujitsu Limited
• Inventors: Takimoto, Kyuichi, Matsumoto, Takashi, Sano, Yoshiaki
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): SHIN, KYUNG E
• Application Number:
  US08/758,890
• Time in Patent Office: 743 Days
• Field of Search: 320/140, 320/164, 320/162, 320/163, 320/145, 313/275, 313/276, 313/277, 313/274, 313/284, 313/285, 330/199, 330/200, 330/297, 330/110
• US Class Current: 320/164
• CPC Class Codes: G05F 1/575 characterised by the feedback circuit
• CPC Class Codes: H02J 7/00 Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries

Abstract

A charging apparatus having a power supply circuit that provides a DC output current via a sense resistor. A current detector amplifies, detects and provides a voltage across the sense resistor. A controller designates the output of the current detector as a determination signal when the DC output current is equal to a preset voltage. Responsive to the determination signal, the controller generates a control signal in order to control the DC output current of the power supply circuit. More particularly, the current detector includes a first differential amplifier that amplifies and output the voltage across the sense resistor, a second differential amplifier amplifies and supplies a differential voltage between the output of the first differential amplifier and a predetermined first reference voltage, and a first output circuit responsive to the output of the second differential amplifier delivers the determination signal. The second differential amplifier includes a first clamp circuit provided between the first differential amplifier and the first output circuit to clamp the input to the second differential amplifier.

Claims

1. A charging apparatus including a power supply circuit for providing a DC output current via a sense resistor, a current detector for amplifying, detecting and providing a voltage across the sense resistor, and a controller for designating the output of the current detector as a determination signal when the DC output current is equal to a preset current and responsive to the determination signal for generating a control signal in order to control the DC output current of the power supply circuit, the current detector of the charging apparatus comprising:

a first differential amplifier for amplifying and outputting the voltage across the sense resistor;

a second differential amplifier for amplifying and supplying a differential voltage between the output of the first differential amplifier and a predetermined first reference voltage; and

a first output circuit responsive to the output of the second differential amplifier for producing the determination signal;

wherein the second differential amplifier has a first clamp circuit provided between the first differential amplifier and the first output circuit for clamping a first input to the second differential amplifier when the current detector has not delivered the determination signal and wherein the first clamp circuit includes a PNP transistor having a base to which an internal power supply voltage is applied, a collector connected to the first input of the second differential amplifier, and an emitter connected to the first output circuit.

2. A charging apparatus according to claim 1 further comprising a level shift circuit connect between the first clamp circuit and the first output circuit.

3. A charging apparatus including a power supply circuit for providing a DC output current via a sense resistor, a current detector for amplifying, detecting and outputting a voltage across the sense resistor, a voltage detector for amplifying and detecting a DC output voltage of the power supply circuit, and a control circuit for designating the output of the current detector as a determination signal when the DC output current is equal to a preset current, and for designating the output of the voltage detector as the determination signal when the DC output voltage is equal to the output of the voltage detector, wherein the control circuit generates a control signal responsive to the designated determination signal for controlling the DC output current and DC output voltage of the power supply circuit, said current detector including:

a first differential amplifier for amplifying and outputting the voltage across the sense resistor;

a second differential amplifier for amplifying and supplying a differential voltage between the output of the first differential amplifier and a predetermined first reference voltage; and

a first output circuit responsive to the output of the second differential amplifier for producing the determination signal;

wherein the second differential amplifier has a first clamp circuit provided between the first differential amplifier and the first output circuit for clamping a first input to the second differential amplifier when the current detector has not delivered the determination signal and wherein the first clamp circuit includes a PNP transistor having a base to which an internal power supply voltage is applied, a collector connected to the first input of the second differential amplifier, and an emitter connected to the first output circuit;

said voltage detector including;

a voltage dividing circuit for dividing the DC output voltage of the power supply circuit to produce a divided voltage signal;

a third differential amplifier for amplifying and outputting a differential voltage between the divided voltage signal and a preset second reference voltage; and

a second output circuit responsive to the output of the third differential amplifier for producing the determination signal;

wherein the third differential amplifier has a second clamp circuit provided between the third differential amplifier and the second output circuit for clumping a first input to the third differential amplifier when the voltage detector has not delivered the determination signal.

4. A charging apparatus according to claim 3 further comprising a level shift circuit connected between the first clamp circuit and the first output circuit.

5. A charging apparatus according to claim 3, wherein the second clamp circuit includes a diode having an anode connected to the second output circuit and a cathode connected to the input of the third differential amplifier.

6. A charging apparatus according to claim 3 further comprising a level shift circuit connected between the second clamp circuit and the second output circuit.

7. A charging apparatus including a power supply circuit for providing a DC output current via a sense resistor, a current detector for amplifying, detecting and outputting a voltage across the sense resistor, a voltage detector for amplifying and detecting a DC output voltage of the power supply circuit, and a control circuit for designating the output of the current detector as a determination signal when the DC output current is equal to a preset current, and for designating the output of the voltage detector as the determination signal when the DC output voltage is equal to the output of the voltage detector, wherein the control circuit generates a control signal responsive to the designated determination signal for controlling the DC output current and the DC output voltage of the power supply circuit, said current detector including:

a first differential amplifier for amplifying and outputting the voltage across the sense resistor;

a second differential amplifier for amplifying and supplying a differential voltage between the output of the first differential amplifier and a predetermined first reference voltage; and

a first output circuit responsive to the output of the second differential amplifier for producing the determination signal;

wherein the second differential amplifier has a first clamp circuit provided between the first differential amplifier and the first output circuit for clamping a first input to the second differential amplifier when the current detector has not delivered the determination signal;

said voltage detector including;

a voltage dividing circuit for dividing the DC output voltage of the power supply circuit to produce a divided voltage signal;

a third differential amplifier for amplifying and outputting a differential voltage between the divided voltage signal and a preset second reference voltage; and

a second output circuit responsive to the output of the third differential amplifier for producing the determination signal;

wherein the third differential amplifier has a second clamp circuit provided between the third differential amplifier and the second output circuit for clamping a first input to the third differential amplifier when the voltage detector has not delivered the determination signal and wherein the second clamp circuit includes an NPN transistor having a collector to which a drive voltage is applied, a emitter connected to the first input of the third differential amplifier, and a base connected to the second output circuit.

8. The charging apparatus according to claim 7 further comprising a level shift circuit connected between the first clamp circuit and the first output circuit.

9. The charging apparatus according to claim 7 further comprising a level shift circuit connected between the second clamp circuit and the second output circuit.

10. A charging apparatus including a voltage detector for amplifying and detecting a DC output voltage of a power supply circuit and a control circuit for designating the output of the voltage detector as a determination signal when the DC output voltage is equal to a preset voltage, wherein the control circuit generates a control signal responsive to the designated determination signal for controlling the DC output voltage of the power supply circuit, the voltage detector of the charging apparatus comprising:

a voltage dividing circuit for dividing the DC output voltage of the power supply circuit and delivering a divided voltage signal;

a differential amplifier for amplifying and outputting a differential voltage between the divided voltage signal and a preset reference voltage; and

an output circuit responsive to the output of the differential amplifier for producing the determination signal;

wherein the differential amplifier has a clamp circuit provided between the differential amplifier and the output circuit for clamping a first input to the differential amplifier when the voltage detector has not delivered the determination signal and wherein the clamp circuit includes an NPN transistor having a collector to which a drive supply voltage is applied, an emitter connected to the first input of the differential amplifier, and a base connected to the output circuit.

11. A charging apparatus according to claim 10 further comprising a level shift circuit connected between the clamp circuit and the output circuit.

12. A current detector comprising:

a power supply circuit for providing a DC output current via a sense resistor;

a first differential amplifier for amplifying and outputting a voltage across the sense resistor;

a second differential amplifier for amplifying and supplying a differential voltage between the output of the first differential amplifier and a predetermined reference voltage; and

an output circuit responsive to the output of the second differential amplifier for producing the determination signal;

wherein the second differential amplifier has a clamp circuit provided between the first differential amplifier and the output circuit for clamping an input to the second differential amplifier when the output of the first differential amplifier exceeds the predetermined reference voltage and wherein the clamp circuit includes a PNP transistor having a base to which an internal power supply voltage is applied, a collector connected to the first input of the second differential amplifier, and an emitter connected to the output circuit.

13. A voltage detector comprising:

a voltage dividing circuit for dividing a DC output voltage to produce a divided voltage signal;

a differential amplifier for amplifying and outputting a differential voltage between the divided voltage signal and a preset reference voltage; and

an output circuit responsive to the output of the differential amplifier for producing a determination signal;

wherein the differential amplifier has a clamp circuit provided between the differential amplifier and the output circuit for clamping an input to the differential amplifier when the divided voltage signal exceeds the preset reference voltage, wherein the clamp circuit includes an NPN transistor having a collector to which a drive supply voltage is applied, an emitter connected to the first input of the differential amplifier, and a base connected to the output circuit.