Input control apparatus and method with inrush current, under and over voltage handling

• US 8,885,308 B2
• Filed: 07/18/2011
• Issued: 11/11/2014
• Est. Priority Date: 07/18/2011
• Status: Active Grant

• Current Assignee: Crane Electronics, Inc. (Crane Company)
• Original Assignee: Crane Electronics, Inc. (Crane Company)
• Inventors: Waltman, Barry F., Hughes, Rodney Alan, Adriance, Reid, Nkei, Bertrand, Kuehny, Jay Allen
• Primary Examiner(s): Leja, Ronald W
• Application Number:
  US13/185,210
• Publication Number:
  US 20130021702A1
• Time in Patent Office: 1,212 Days
• Field of Search: 361/90
• US Class Current: 361/90
• CPC Class Codes: H02H 3/087 for dc applications
• CPC Class Codes: H02H 3/202 for dc systems
• CPC Class Codes: H02H 3/24 responsive to undervoltage or no-voltage H02H3/207 takes precedence
• CPC Class Codes: H02H 9/001 limiting speed of change of electric quantities, e.g. soft switching on or off progressive control of electronic switches for eliminating interferences H03K17/16
• CPC Class Codes: H02H 9/025 Current limitation using field effect transistors
• CPC Class Codes: H02M 1/32 Means for protecting converters other than automatic disconnection
• CPC Class Codes: H02M 1/36 Means for starting or stopping converters
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators

Abstract

Control circuitry handles inrush current, and may provide under voltage and/or over voltage monitoring and handling, as well as remote enable handling. The circuitry may advantageously employ a sense capacitor in parallel with an input capacitor (e.g., bulk input filter capacitor), and a current mirror to produce a signal proportional to input current. A clamp circuit may control a series pass device to regulate current in response to the proportional signal, or to interrupt current flow in response to an under voltage or over voltage condition or receipt of a signal indicative of a disable state. An enable signal may be summed into a comparator that handles under voltage condition determination.

Claims

1. An input control circuit that controls inrush current, comprising:

a series switch electrically coupled in series on an input line and operable in response to control signals to adjust a flow of an input current along the input line;

a sense capacitor directly connected to an input filter capacitor on the input line to develop a signal that is proportional to the input current;

a current sense mirror electrically coupled to the sense capacitor to receive the signal that is proportional to the input current that is charging the input filter capacitor; and

a clamp circuit responsive at least to the current sense mirror to provide the control signals to the series switch to cause the series switch to adjust the flow of the input current along the input line.

2. The input control circuit of claim 1 wherein the current sense mirror includes a first mirror transistor coupled to a ground reference through a first mirror resistor and a second mirror transistor coupled to the ground reference through a second mirror resistor, a base of the first mirror transistor and a base of the second mirror transistor commonly coupled to the sense capacitor to maintain a constant inrush charge current to the input filter capacitor.

3. The input control circuit of claim 2, further comprising:

a pair of trickle bias resistors electrically coupled between the input line and a source of the first mirror transistor of the current sense mirror.

4. The input control circuit of claim 1, further comprising:

an over voltage lockout monitor circuit operable to detect an over voltage condition on the input line and coupled to supply a signal indicative of the over voltage condition to the clamp circuit, wherein the clamp circuit is further responsive at least to the over voltage lockout monitor circuit to provide control signals to the series switch to cause the series switch to stop the flow of the input current along the input line.

5. The input control circuit of claim 4 wherein the over voltage lockout monitor circuit includes a pair of over voltage lockout resistors coupled as a voltage divider between the input line and a ground reference via an over voltage lockout Zener diode which is coupled to drive a switch controlling transistor which is in turn coupled to control the series switch.

6. The input control circuit of claim 5 wherein the over voltage lockout monitor circuit further includes a low impedance charge path formed by a speedup diode and a speedup resistor electrically coupled between the input line and the base of the transistor.

7. The input control circuit of claim 1, further comprising:

an under voltage lockout monitor circuit operable to detect an under voltage condition on the input line and coupled to supply a signal indicative of the under voltage condition to the clamp circuit, wherein the clamp circuit is further responsive at least to the under voltage lockout monitor circuit to provide control signals to the series switch to cause the series switch to stop the flow of the input current along the input line.

8. The input control circuit of claim 7 wherein the under voltage lockout monitor circuit includes an under voltage lockout comparator that has a first input and a second input, the first input coupled to the input line via a first under voltage lockout resistor and the second input coupled to a voltage reference source via a second under voltage lockout resistor.

9. The input control circuit of claim 8, further comprising:

an enable monitor circuit operable in response to an enable single to provide control signals to to cause the series switch to stop the flow of the input current along the input line.

10. The input control circuit of claim 9 wherein the enable monitor circuit is selectively operable electrically short the first and second inputs of the under voltage lockout comparator.

11. The input control circuit of claim 1 wherein the series switch Q1 is a P-Channel metal oxide semiconductor field effect transistor (MOSFET) having a gate coupled to the clamp circuit and the clamp circuit includes a switch controlling transistor coupled to control the series switch.

12. The input control circuit of claim 11, further comprising:

an over voltage lockout monitor circuit operable to detect an over voltage condition on the input line and coupled to supply a signal indicative of the over voltage condition to the clamp circuit;

an under voltage lockout monitor circuit operable to detect an under voltage condition on the input line and coupled to supply a signal indicative of the under voltage condition to the clamp circuit;

an enable monitor circuit operable in response to an enable single to provide control signals to the clamp circuit indicative of a disable state, and

wherein the clamp circuit is further responsive at least to the over voltage lockout monitor circuit, the under voltage lockout monitor circuit, and the enable monitor circuit to provide control signals to the series switch Q1 to cause the series switch to stop the flow of the input current along the input line in response to a signal indicative of the over voltage condition, the under voltage condition, or a disable state.

13. The input control circuit of claim 1 wherein the sense capacitor has a capacitance that is less than a capacitance of the input filter.

14. A method of operating an input control circuit, the method comprising:

capacitively producing a signal proportional to an input current;

mirroring the signal proportional to input current; and

adjusting a flow of the input current in response at least to the signal that is proportional to the input current to control an inrush current.

15. The method of claim 14 wherein capacitively producing a signal proportional to input current includes allowing a sense capacitor directly coupled to an input filter capacitor on an input line to be charged by the input current and adjusting a flow of the input current includes supplying a signal from a clamp circuit to a series pass device electrically coupled in series on the input line.

16. The method of claim 15, further comprising:

detecting at least one of an over voltage condition or an under voltage condition on the input line; and

in response to detecting at least one of the over voltage condition or the under voltage condition on the input line providing a signal to the clamp circuit that causes the series pass device to stop the flow of the input current.

17. The method of claim 15, further comprising:

detecting an enable signal indicative of a selected one of two states;

in response to detecting the enable single of a first one of the two states providing a signal that causes the series pass device to stop the flow of the input current; and

in response to detecting the enable single of a second one of the two states providing a signal that causes an under voltage lockout monitor circuit to function.

18. An input control circuit operable to control inrush current, comprising:

a series switch operable in response to control signals to adjust a flow of an input current along an input line;

an over voltage lockout monitor circuit operable to detect an over voltage condition on the input line and to produce a signal indicative of the over voltage condition;

an under voltage lockout monitor circuit operable to detect an under voltage condition on the input line and to produce a signal indicative of the under voltage condition;

a sense capacitor directly connected to an input filter capacitor on the input line to develop a signal that is proportional to the input current;

a current sense mirror electrically coupled to the sense capacitor to receive the signal that is proportional to the input current;

an enable monitor circuit operable in response to an enable single to provide a signal indicative of an enable/disable condition; and

a clamp circuit that provides control signals to control the series switch to adjust the flow of the input current along the input line in response to the current sense mirror, the clamp circuit is responsive to the signals from the over voltage lockout monitor circuit, the under voltage lockout monitor circuit, and the enable monitor circuit to provide control signals that cause the series switch to stop the flow of the input current along the input line.