Bi-directional field control for proportional control based generator/alternator voltage regulator

• US 20040155632A1
• Filed: 02/07/2003
• Published: 08/12/2004
• Est. Priority Date: 02/07/2003
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Visteon Global Technologies Incorporated (Visteon Corporation)
• Inventors: Wilson, Scott R.
• Granted Patent: US 7,038,406 B2
• Time in Patent Office: Days
• US Class Current: 322/28
• CPC Class Codes: H02P 9/305 controlling voltage H02P9/302 takes precedence

Abstract

An H-bridge switching topology for bi-directional field excitation to null the effects of a rotor'"'"'s permanent magnets is disclosed. The present invention uses both a low-side and a high-side field excitation driver to control the rotor'"'"'s average field current. A standard proportional control signal for generators using uni-directional field excitation is used to control an H-bridge for bi-directional field excitation. The H-bridge consists of two pair of power switches. In a preferred embodiment, the switches are n-channel MOSFETs. A drive circuit interfaces a logic block with the H-bridge in order to properly bias the power switches. The present invention also comprises a method of monitoring the uni-directional field control duty cycle as a means of determining if the system voltage is rising and going out of control. If the system voltage exceeds a voltage range, a logic circuit then provides reverse field current in a pulse width modulation fashion to null the effects of the permanent magnets.

Claims

1. A method of controlling voltage using bi-directional field excitation current, comprising the steps of:

monitoring a field control duty cycle;

determining if a system voltage exceeds a range; and

providing field current, whereby effects of permanent magnets are nulled.

2. The method according to claim 1, wherein said step of providing field current further comprises providing reverse field current that is pulse width modulated.

3. The method according to claim 2, further comprising the steps of:

continually monitoring said field control duty cycle; and

determining when said reverse current is no longer needed.

4. The method according to claim 1, wherein said step of monitoring a field control duty cycle comprises measuring a field driver control signal'"'"'s pulse width;

wherein said step of determining if a system voltage exceeds a range comprises determining whether said field driver control signal'"'"'s duty cycle is above or below a threshold; and

wherein said step of providing field current comprises supplying forward field current if said field drive duty cycle is above a threshold.

5. The method according to claim 1, further comprising the step of using a low-side and a high-side field excitation driver to control said field current.

6. The method according to claim 4, further comprising the step of supplying reverse field current by turning on a first switch and pulse width modulating a second switch on and off after said field driver control signal'"'"'s duty cycle falls outside a threshold a predetermined number of times.

7. The method according to claim 4, further comprising the step of supplying forward field current comprises turning a third switch on and turning a fourth switch on and off with a duty cycle corresponding to said field driver control signal'"'"'s duty cycle.

8. The method according to claim 4, wherein said step of measuring a field driver control signal'"'"'s pulse width comprises:

counting a number of clock cycles that occur when said field driver control signal is high.

9. The method according to claim 4, wherein said step of determining whether said field driver control signal'"'"'s duty cycle is above or below a threshold comprises comparing a bit count a predetermined consecutive number of times.

10. The method according to claim 4, further comprising the step of determining a set point voltage.

11. The method according to claim 6, wherein said step of supplying forward field current comprises turning a third switch on and turning a fourth switch on and off with a duty cycle corresponding to said field driver control signal'"'"'s duty cycle, whereby forward current is supplied to said rotor and said generator output is increased;

wherein said step of measuring a field driver control signal'"'"'s pulse width comprises counting a number of clock cycles that occur when said field driver control signal is high; and

wherein said step of determining whether said field driver control signal'"'"'s duty cycle is above or below a threshold comprises comparing a bit count.

12. A method of controlling voltage using bi-directional field excitation current, comprising the steps of:

measuring a field driver control signal'"'"'s pulse width by counting a number of clock cycles that occur when said field driver control signal is high;

determining whether said field driver control signal'"'"'s duty cycle is above or below a threshold by comparing a bit count a predetermined consecutive number of times, whereby field drive duty-cycle noise is filtered;

supplying reverse field current if said field driver control signal'"'"'s duty cycle falls below a reverse direction threshold, comprising;

turning a first switch on and pulse width modulating a second switch on and off,

whereby reverse current is supplied to a rotor and generator/alternator output is

decreased and whereby the effects of permanent magnets are nulled; and

supplying forward field current if said field drive duty cycle falls below said reverse direction threshold, comprising;

turning a third switch on and turning a fourth switch on and off with a duty cycle

corresponding to said field driver control signal'"'"'s duty cycle, whereby forward

current is supplied to said rotor and said generator output is increased.

13. A voltage regulator, comprising:

a logic block;

a controller having a field driver control output operably connected to a first input of said logic block;

an H-bridge;

a drive block operably connected between said H-bridge and said logic block; and

a power train control module operably connected between said controller and said drive block.

14. The voltage regulator according to claim 13, wherein said H-bridge comprises:

a first pair of switches, comprising a first and a second switch connected in series;

a second pair of switches, comprising a third and a fourth switch connected in series, wherein said first and second pair of switches are operably connected in parallel across a power source; and

a rotor operably connected between said series connections of said first and second pair of switches.

15. The voltage regulator according to claim 13, wherein said logic block comprises:

a counter having an output, whereby a number of clock cycles that occur when a field driver control signal is high is counted; and

a comparator, whereby said output from said counter is compared to a threshold a predetermined consecutive number of times, whereby field duty cycle noise is filtered.

16. The voltage regulator according to claim 13, wherein said driver block comprises:

an AND gate having a mode signal input and an inverted field driver signal input and a fourth output operably connected to a control input of said fourth switch, whereby said fourth output signal'"'"'s duty cycle equal said field driver signal'"'"'s duty cycle when said mode signal is low;

a third output signal operably connected to a control input of said third switch, whereby said third switch is on when said mode signal is low;

a first output signal operably connected to a control input of said first switch, whereby said first switch is on when said mode signal is high; and

a pulse width modulation circuit having a mode signal input and a second output operably connected to a control input of said second switch, whereby said second switch is pulse modulated on and off when said mode signal is high.

17. The voltage regulator according to claim 13, wherein said driver block comprises:

a mode signal input and a pulse width modulation input operably connected to corresponding outputs of said logic block;

a first output signal operably connected to a control input of said first switch, whereby said first switch is on when said mode signal is high;

a second output operably connected to a control input of said second switch, whereby said second switch is pulse modulated on and off when said mode signal is high;

a third output signal operably connected to a control input of said third switch, whereby said third switch is on when said mode signal is low; and

a fourth output operably connected to a control input of said fourth switch, whereby said fourth output signal'"'"'s duty cycle equal said field driver control signal'"'"'s duty cycle when said mode signal is low.

18. The voltage regulator according to claim 13, wherein said controller is a proportional controller for uni-directional field excitation.

19. The voltage regulator according to claim 13, wherein said power control module comprises:

an output operably connected to an input of said controller, whereby a pulse width modulated signal is transmitted to said controller; and

an input operably connected to an output of said logic block, whereby said power control module receives a torque demand signal.

20. The voltage regulator according to claim 13,

wherein said H-bridge comprises:

a first pair of switches, comprising a first and a second switch connected in series;

a second pair of switches, comprising a third and a fourth switch connected in series, wherein said first and second pair of switches are operably connected in parallel across a power source; and

a rotor operably connected between said series connections of said first and second pair of switches; and

wherein said logic block comprises;

a counter having an output, whereby a number of clock cycles that occur when a field driver control signal is high is counted; and

a comparator, whereby said output from said counter is compared to a threshold a predetermined consecutive number of times, whereby field drive duty cycle noise is filtered; and

wherein said driver block comprises;

a mode signal input and a pulse width modulation input operably connected to corresponding outputs of said logic block;

a first output signal operably connected to a control input of said first switch, whereby said first switch is on when said mode signal is high;

a second output operably connected to a control input of said second switch, whereby said second switch is pulse modulated on and off when said mode signal is high;

a third output signal operably connected to a control input of said third switch, whereby said third switch is on when said mode signal is low; and

a fourth output operably connected to a control input of said fourth switch, whereby said fourth output signal'"'"'s duty cycle equals said field driver control signal'"'"'s duty cycle when said mode signal is low.