Magnetic field sensor

• US 6,727,684 B2
• Filed: 07/10/2002
• Issued: 04/27/2004
• Est. Priority Date: 07/26/2001
• Status: Expired due to Term

• Current Assignee: Collabo Innovations, Inc. (Wi-LAN Inc.)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Hatanaka, Tadata
• Primary Examiner(s): Le, N.
• Assistant Examiner(s): Nguyen, Vincent Q.
• Application Number:
  US10/191,520
• Publication Number:
  US 20030020470A1
• Time in Patent Office: 657 Days
• Field of Search: 324/251, 324/235, 324/51, 324/117.R, 324/117.H, 324/158.1, 324/207.2, 338/32.H, 327/511, 327/185, 327/205
• US Class Current: 324/117.00H
• CPC Class Codes: G01D 3/02 with provision for altering or correcting the law of variation
• CPC Class Codes: G01D 5/145 influenced by the relative movement between the Hall device and magnetic fields see G01R33/06

Abstract

A magnetic field sensor includes: a Hall element; a voltage amplifier for amplifying an output voltage from the Hall element so as to output an amplified signal; a voltage comparison circuit for receiving the amplified signal; a switch circuit provided between the voltage amplifier and the voltage comparison circuit for inverting a polarity of the amplified signal; and a latch circuit for holding an output signal from the voltage comparison circuit. The voltage comparison circuit inverts a polarity of a hysteresis voltage that determines a reference value of a magnetic field intensity in response to a first synchronizing signal, which triggers a detection of a magnetic field, and a second synchronizing signal following the first synchronizing signal.

Claims

1. A magnetic field sensor, comprising:

a Hall element;

a voltage amplifier for amplifying an output voltage from the Hall element so as to output an amplified signal, said voltage amplifier including a first and second output terminal;

a capacitor including a first and second electrode which are connected to the first and second output terminal, respectively;

a first switch circuit provided between one of the first and second output terminals and one of the first and second electrodes for being closed by an external signal in a first phase while being opened by an external signal in a second phase;

a voltage comparison circuit for receiving the amplified signal from both ends of the first switch circuit in the second phase;

a second switch circuit provided between the voltage amplifier and the voltage comparison circuit for inverting a polarity of the amplified signal; and

a latch circuit for holding an output signal from the voltage comparison circuit,

wherein the voltage comparison circuit inverts a polarity of a hysteresis voltage that determines a reference value of a magnetic field intensity in response to a first synchronizing signal, which triggers a detection of a magnetic field, and a second synchronizing signal following the first synchronizing signal.

2. A magnetic field sensor, comprising:

a Hall element;

a voltage amplifier for amplifying an output voltage from the Hall element so as to output an amplified signal;

a voltage comparison circuit for receiving the amplified signal;

a switch circuit provided between the voltage amplifier and the voltage comparison circuit for inverting a polarity of the amplified signal; and

a latch circuit for holding an output signal from the voltage comparison circuit,

wherein the voltage comparison circuit inverts a polarity of a hysteresis voltage that determines a reference value of a magnetic field intensity in response to a first synchronizing signal, which triggers a detection of a magnetic field, and a second synchronizing signal following the first synchronizing signal,

wherein the latch circuit includes a first flip-flop circuit and a second flip-flop circuit for receiving binary values respectively in response to the first synchronizing signal and the second synchronizing signal, so as to hold an operated value as an output value, which is obtained by an operation on the binary values, in response to the second synchronizing signal.

3. A magnetic field sensor, comprising:

a Hall element including two pairs of external terminals;

a first switch circuit connected to the two pairs of external terminals for selecting one of the two pairs of external terminals as output terminals;

a voltage amplifier for amplifying an output voltage of the Hall element that is received via the first switch circuit and outputting an amplified signal;

a memory device for storing the amplified signal;

a second switch circuit provided between the voltage amplifier and the memory device for opening/closing a connection to the memory device;

a voltage comparison circuit for receiving the amplified signal;

a third switch circuit provided between the voltage amplifier and the voltage comparison circuit for inverting a polarity of the amplified signal; and

a latch circuit for holding an output signal from the voltage comparison circuit,

wherein;

in response to a first synchronizing signal, which triggers a detection of a magnetic field, the first switch circuit selects one of the two pairs of external terminals of the Hall element as input terminals and the other one of the two pairs of external terminals of the Hall element as output terminals, with the second switch circuit being closed;

in response to a second synchronizing signal following the first synchronizing signal, the first switch circuit selects the one of the two pairs of external terminals of the Hall element as output terminals and the other one of the two pairs of external terminals of the Hall element as input terminals, with the second switch circuit being opened, thereby inputting to the voltage comparison circuit a sum of a first amplified signal, which has been stored in the memory device, and a second amplified signal from the voltage amplifier;

in response to a third synchronizing signal following the second synchronizing signal, the third switch circuit inverts a polarity of the sum of the first amplified signal and the second amplified signal; and

the voltage comparison circuit inverts a polarity of a hysteresis voltage that determines a reference value of a magnetic field intensity in response to the second synchronizing signal and the third synchronizing signal as triggers.

4. The magnetic field sensor of claim 3, wherein the latch circuit includes a first flip-flop circuit and a second flip-flop circuit for receiving binary values respectively in response to the second synchronizing signal and the third synchronizing signal, so as to hold an operated value as an output value, which is obtained by an operation on the binary values, in response to the third synchronizing signal.

5. The magnetic field sensor of claim 3, wherein the memory device includes a capacitor.