Real current sense apparatus for a DC-to-DC converter

• US 7,180,278 B2
• Filed: 03/28/2005
• Issued: 02/20/2007
• Est. Priority Date: 03/30/2004
• Status: Expired due to Fees

• Current Assignee: Richtek Technology Corporation (MediaTek, Inc.)
• Original Assignee: Richtek Technology Corporation (MediaTek, Inc.)
• Inventors: Chen, Jiun-Chiang, Tai, Liang-Pin
• Primary Examiner(s): HAN, YOUNGHUIE JESSICA
• Application Number:
  US11/090,179
• Publication Number:
  US 20050219926A1
• Time in Patent Office: 694 Days
• Field of Search: 323/222, 323/225, 323/273, 323/274, 323/275, 323/276, 323/277, 323/280, 323/224
• US Class Current: 323/280
• 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 real current sense apparatus for a DC-to-DC converter uses a current mirror composed by two JFETs to mirror the output current of the converter to generate a temperature-independent mirror current to further generate a current sense signal. Due to the temperature-independence of the mirror current, the current sense signal is also temperature-independent.

Claims

1. A real current sense apparatus for a DC-to-DC converter including a high-side switch connected between an input voltage and a phase node, the real current sense apparatus comprising:

a first JFET connected to the phase node for serving as a low-side switch to conduct an output current;

a second JFET connected to the first JFET for forming a current mirror to mirror the output current to thereby generate a mirror current; and

a transconductive amplifier for amplifying the mirror current to thereby generate a current sense signal.

2. The real current sense apparatus of claim 1, wherein the mirror current is proportional to the output current.

3. The real current sense apparatus of claim 1, further comprising a sample and hold circuit for sampling and holding the current sense signal.

4. A real current sense apparatus for a DC-to-DC converter including a low-side switch connected to a phase node, the real current sense apparatus comprising:

a first JFET connected between the phase node and an input voltage for serving as a high-side switch to conduct an output current;

a second JFET connected to the first JFET for forming a current mirror to mirror the output current to thereby generate a mirror current; and

a transconductive amplifier for amplifying the mirror current to thereby generate a current sense signal.

5. The real current sense apparatus of claim 4, wherein the mirror current is proportional to the output current.

6. The real current sense apparatus of claim 4, further comprising a sample and hold circuit for sampling and holding the current sense signal.