VOLTAGE MONITOR

• US 20130082684A1
• Filed: 10/04/2011
• Published: 04/04/2013
• Est. Priority Date: 10/04/2011
• Status: Active Grant

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Analog Devices, Inc.
• Inventors: SPALDING, GEORGE REDFIELD Jr.
• Granted Patent: US 9,081,038 B2
• Time in Patent Office: Days
• US Class Current: 324/111
• CPC Class Codes: G01R 15/06 having reactive components, e.g. capacitive transformer
• CPC Class Codes: G01R 19/0038 Circuits for comparing several input signals and for indicating the result of this comparison, e.g. equal, different, greater, smaller (comparing pulses or pulse trains according to amplitude)
• CPC Class Codes: G01R 19/2506 Arrangements for conditioning or analysing measured signals, e.g. for indicating peak values G01R19/003 takes precedence; Details concerning sampling, digitizing or waveform capturing displaying waveforms G01R13/00; analog sampling G01R19/0053
• CPC Class Codes: H03F 2203/45536 the FBC comprising a switch and being coupled between the LC and the IC
• CPC Class Codes: H03F 2203/45544 the IC comprising one or more capacitors, e.g. coupling capacitors
• CPC Class Codes: H03F 2203/45548 the IC comprising one or more capacitors as shunts to earth or as short circuit between inputs
• CPC Class Codes: H03F 2203/45594 the IC comprising one or more resistors, which are not biasing resistor
• CPC Class Codes: H03F 2203/45604 the IC comprising a input shunting resistor
• CPC Class Codes: H03F 2203/45616 the IC comprising more than one switch, which are not cross coupled
• CPC Class Codes: H03F 3/45475 using IC blocks as the active amplifying circuit

Abstract

A voltage monitor comprising a first capacitive potential divider for presenting an attenuated representation of an input voltage to a comparator.

Claims

1. A voltage monitor comprising a capacitive potential divider for presenting an attenuated representation of an input voltage to a comparator.

2. A voltage monitor as claimed in claim 1, further comprising electrically controlled devices for setting the capacitors of the potential divider to a predetermined state.

3. A voltage monitor as claimed in claim 2, in which the electrically controlled devices comprise transistors.

4. A voltage monitor as claimed in claim 2, wherein the voltage monitor comprises at least a first switch in series with the capacitors of the capacitive potential divider.

5. A voltage monitor as claimed in claim 4, further including a second switch in series with the capacitive divider, and wherein first and second capacitors of the capacitive potential divider are electrically interposed between the first and second switches.

6. A voltage monitor as claimed in claim 2, further comprising a switching arrangement for selectively discharging the capacitors of the capacitive divider.

7. A voltage monitor as claimed in claim 2, further comprising a switching arrangement for sampling an offset voltage of the comparator onto the capacitors of the capacitive potential divider.

8. A voltage monitor as claimed in claim 2, in which the capacitive potential divider comprises a first capacitor having first and second plates and a second capacitor having first and second plates;

wherein a first plate of the first capacitor is connected to a first end of a first switch, a second plate of the first capacitor is connected to an output node, a first plate of the second capacitor is connected to the output node, and a second plate of the second capacitor is connected to a first end of a second switch, and a second end of the first switch is connected to an input node and a second end of the second switch is connected to a reference voltage.

9. A voltage monitor as claimed in claim 8, further comprising a third switch for selectively connecting the first plate of the first capacitor to a reference voltage, a fourth switch for selectively connecting the second plate of the second capacitor to the reference voltage, and a further switch for selectively connecting the output node to the reference voltage or to an output of the comparator.

10. A voltage monitor as claimed in claim 1, further comprising a sampling capacitor for sampling and storing a representation of a reference voltage.

11. A voltage monitor as claimed in claim 10, further comprising a further capacitor in series with the sampling capacitor so as to form a further capacitive potential divider.

12. A voltage monitor as claimed in claim 11, further comprising a switching arrangement for selectively discharging the further capacitor and for connecting the sampling capacitor to the reference voltage.

13. A monitor as claimed in claim 1, in which at least one of the capacitors of the capacitive potential divider is a variable capacitor.

14. A voltage monitor as claimed in claim 11, in which at least one of the capacitors of the further capacitive potential divider is a variable capacitor.

15. A voltage monitor as claimed in claim 14, in which both of the capacitors of the further potential divider are variable capacitors, and/or first and second capacitors of the potential divider are variable capacitors;

and

a controller adjusts the capacitor such that the sum of the capacitance of the capacitors in the potential divider is substantially equal to the sum of the capacitance of the capacitors of the further potential divider.

16. A voltage monitor as claimed in claim 2, comprising first and second channels used in an alternating manner such that one channel is active whilst the other channel is being set to its initial state.

17. A voltage monitor comprising a sampling capacitor arranged to sample and hold a reference voltage such that a reference voltage generator can be de-powered.

18. A voltage monitor as claimed in claim 17, further comprising a capacitive potential divider arranged to attenuate an input voltage that is monitored by the voltage monitor.