Current sense apparatus and method

• US 6,801,030 B2
• Filed: 05/21/2003
• Issued: 10/05/2004
• Est. Priority Date: 05/27/2002
• Status: Expired due to Fees

• Current Assignee: Richtek Technology Corporation (MediaTek, Inc.)
• Original Assignee: Richtek Technology Corporation (MediaTek, Inc.)
• Inventors: Liu, Jing-Meng, Tai, Liang-Pin, Wang, Hung-I, Hsieh, Shwu-Liang
• Primary Examiner(s): Zarneke, David A.
• Assistant Examiner(s): Nguyen, Tung X.
• Application Number:
  US10/442,084
• Publication Number:
  US 20030218455A1
• Time in Patent Office: 503 Days
• Field of Search: 324/117.R, 324/765, 324/158.1, 323/313, 323/314, 323/315, 323/316, 323/317
• US Class Current: 324/117.00R
• CPC Class Codes: G01R 19/0092 measuring current only all subgroups of G01R19/00 take precedence
• CPC Class Codes: H02M 1/0009 Devices or circuits for detecting current in a converter
• CPC Class Codes: H02M 3/1588 comprising at least one synchronous rectifier element H02M3/1582, H02M3/1584 take precedence
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

A current sense apparatus and method comprises a common drain DMOSFET and a MOSFET connected in series between a high voltage and a low voltage to serve as an output stage. The DMOSFET produces a phase output current, a mirror current mirrored from the phase output current, and a sense voltage. A servo amplifier is connected with the mirror current and sense voltage to produce a current sense signal. Due to the mirror current from the DMOSFET proportional to the phase output current, the current sense apparatus senses the phase output current in a temperature independent manner.

Claims

1. A switching mode DC-to-DC converter for generating a converter output voltage, the converter comprising:

one or more output stages each connected, between a high voltage and a low voltage for producing a phase output current, a mirror current proportional to the phase output current, a phase output voltage and a sense voltage;

one or more serve amplifiers each for converting the mirror currant to a current sense signal;

a voltage feedback circuit for comparing the converter output voltage with a reference voltage to thereby produce a voltage feedback signal;

one or more current feedback circuits each connected with the current sense signal for producing a current feedback-signal; and

a control logic connected with the voltage feedback signal and one or more current feedback signals for producing a control signal to drive the one or more output stage.

2. The converter of claim 1, wherein the output stage comprises:

a phase output node for deriving the phase output voltage;

a common drain DMOSFET connected between the high voltage and phase output node; and

a MOSFET connected between the law voltage and phase output node.

3. The converter of claim 2, wherein the common drain DMOSFET has a gate, a drain connected to the high voltage, a source connected to the phase output node, a current mirror terminal far providing the mirror current, and a sense terminal for providing the sense voltage.

4. The converter of claim 1, wherein the output stage comprising:

a phase output node for deriving the phase output voltage;

a MOSFET connected between the high voltage and phase output mode; and

a common drain DMOSFET connected between the low voltage and phase output node.

5. The converter of claim 4, wherein the common drain DMOSFET has a gate, a drain connected to the phase output node, a source connected to the low voltage, a current mirror terminal for providing the mirror current, and a sense terminal for providing the sense voltage.

6. The converter of claim 1, wherein the servo amplifier comprises:

an operational amplifier having an inverting input connected with the mirror current, a non-inverting input connected with the sense voltage, and an output; and

a MOSFET having a source connected with the inverting input of the operational amplifier, a gate connected with the output of the operational amplifier, and a drain for providing the current sense signal.

7. The converter of claim 1, wherein the voltage feedback circuit comprises:

a reference voltage generator for producing the reference voltage; and

an error amplifier having a non-inverting input connected with the reference voltage and an inverting input connected with the converter output voltage for producing the voltage feedback signal.

8. The converter of claim 7, wherein the reference voltage generator comprises:

a voltage follower connected with an original reference voltage signal for producing the reference voltage;

a capacitor connected to the voltage follower for stabilizing the reference voltage; and

a resistor connected between the non-inverting input of the error amplifier and voltage follower for determining a droop of the converter output voltage.

9. The converter of claim 1, wherein the current feedback circuit is connected with the reference voltage.