FAST SWITCHING FOR POWER INVERTER

• US 20120195079A1
• Filed: 01/31/2011
• Published: 08/02/2012
• Est. Priority Date: 01/31/2011
• Status: Active Grant

• Current Assignee: Tesla Inc.
• Original Assignee: Tesla Motors Incorporated (Tesla Inc.)
• Inventors: Kroeze, Ryan, Campbell, Colin, Kalayjian, Nicholas R.
• Granted Patent: US 8,664,907 B2
• Time in Patent Office: Days
• US Class Current: 363/55
• CPC Class Codes: H02M 1/32 Means for protecting converters other than automatic disconnection
• CPC Class Codes: H02M 7/5387 in a bridge configuration

Abstract

An apparatus includes an inverter including a high-side switch coupled to a low-side switch, the inverter generating a time-varying drive current from a plurality of drive control signals, a positive rail voltage, and a negative rail voltage wherein controlling the switches to generate the time-varying drive current produces a potential transitory overshoot condition for one of the switches of the inverter; a drive control, coupled to the inverter, to generate the drive control signals and to set a level of each of the rail voltages responsive to a plurality of controller signals; and a controller monitoring one or more parameters indicative of the potential transitory voltage overshoot condition, the controller dynamically adjusting, responsive to the monitored parameters, the controller signals to reduce a risk of occurrence of the potential transitory voltage overshoot condition.

Claims

1. An apparatus, comprising:

an inverter including a high-side switch coupled to a low-side switch, said inverter generating a time-varying drive current from a plurality of drive control signals, a positive rail voltage, and a negative rail voltage wherein controlling the switches to generate said time-varying drive current produces a potential transitory overshoot condition for one of said switches of said inverter;

a drive control, coupled to said inverter, to generate said drive control signals and to set a level of each of said rail voltages responsive to a plurality of controller signals; and

a controller monitoring one or more parameters indicative of said potential transitory voltage overshoot condition, said controller dynamically adjusting, responsive to said monitored parameters, said controller signals to reduce a risk of occurrence of said potential transitory voltage overshoot condition.

2. The apparatus of claim 1 wherein said parameters include a magnitude of said time-varying current, a magnitude of said positive rail voltage, and a magnitude of said negative rail voltage.

3. The apparatus of claim 1 wherein said controller dynamically adjusts said controller signals to reduce a magnitude of said negative rail voltage and to thereby reduce said risk.

4. The apparatus of claim 2 wherein said controller dynamically adjusts said controller signals to reduce a magnitude of said negative rail voltage and to thereby reduce said risk.

5. The apparatus of claim 1 wherein said parameters are oversampled and said dynamic adjustment is performed in substantially real time.

6. The apparatus of claim 1 wherein one or more of said parameters are converted to a root means square signal or a rectified mean signal and wherein said controller signals are generated responsive to said root mean square signal or to said rectified mean signal.

7. The apparatus of claim 1 wherein said controller signals include a first series of high-side pulse width modulation (PWM) signals and second series of low-side PWM signals for generation of said time-varying current and wherein said controller signals include a regulator control signal to set said negative voltage rail at a second regulated voltage in a range from about zero volts to less than said negative supply voltage.

8. The apparatus of claim 7 wherein said controller includes a programmatic control element controlling said PWM signals and wherein said controller includes a discrete hardware element controlling said regulator control signal.

9. The apparatus of claim 8 wherein said discrete hardware element includes a comparator having an output providing said regulator control signal wherein said comparator includes a first input receiving a first input voltage derived from said drive current and a second input receiving a preselected voltage threshold to configure said regulator control signal to reduce said risk.

10. The apparatus of claim 9 including a low pass filter coupled to said first input of said comparator.

11. The apparatus of claim 1 wherein said one or more parameters include an estimate of a junction temperature of one or more said components in a heat rejection path of said inverter and wherein said controller signals are responsive to said junction temperature when setting said negative voltage rail.

12. A method, the method comprising the steps of:

a) generating a time-varying drive current from a plurality of drive control signals, a positive rail voltage, and a negative rail voltage wherein said time-varying drive current produces a potential transitory overshoot condition for a switch of an inverter;

b) generating said drive control signals and setting a level of one or more of said rail voltages for said inverter responsive to a plurality of controller signals;

c) monitoring one or more parameters indicative of said potential transitory voltage overshoot condition; and

d) adjusting dynamically, responsive to said monitored parameters, said controller signals to at least reduce a risk of occurrence of said potential transitory voltage overshoot condition.

13. The method of claim 12 wherein said one or more parameters include a magnitude of said time-varying drive current, a magnitude of said positive rail voltage, and a magnitude of said negative rail voltage and wherein said adjusting step includes varying said magnitude of said negative voltage rail voltage to reduce said risk.

14. The method of claim 12 further comprising the step of:

e) low pass filtering said one or more parameters to produce an rms current signal;

wherein said adjusting step d) is responsive to said rms current signal.

15. The method of claim 12 further comprising the steps of:

e) low pass filtering said one or more parameters to produce an rms current signal;

f) comparing said rms current signal to a predetermined threshold allowing non-risky operation for a predetermined range of said rail voltages to produce an comparator output signal;

wherein said adjusting step d) is responsive to said comparator output signal.

16. The method of claim 12 further comprising the step of:

e) estimating a junction temperature of a device in a heat rejection path of said inverter;

wherein said one or more parameters includes said junction temperature.

17. A method, the method comprising the steps of:

a) calculating a maximum available voltage overshoot for an inverter producing a time-varying drive current;

b) determining a current voltage overshoot for said inverter responsive to said time-varying drive current;

c) operating said inverter in a first operational mode for minimization of switching losses when said current voltage overshoot is not greater than said maximum available voltage overshoot while increasing a risk of occurrence of a potential transitory voltage overshoot condition destructive to said inverter; and

d) operating said inverter in a second operational mode for reduction of said risk of occurrence of said potential transitory voltage overshoot condition when said current voltage overshoot is greater than said maximum available voltage overshoot while increasing switching losses.

18. The method of claim 17 further comprising the step of:

e) low pass filtering said one or more parameters to produce an rms current signal;

wherein said adjusting step d) is responsive to said rms current signal.

19. The method of claim 17 further comprising the steps of:

e) low pass filtering said one or more parameters to produce an rms current signal;

f) comparing said rms current signal to a predetermined threshold allowing non-risky operation for a predetermined range of said rail voltages to produce an comparator output signal;

wherein said adjusting step d) is responsive to said comparator output signal.

20. The method of claim 17 further comprising the steps of:

e) estimating a junction temperature of a device in a heat rejection path of said inverter;

wherein said one or more parameters includes said junction temperature.

21. The method of claim 17 wherein said operational modes are set by controlling a negative rail voltage wherein said negative rail voltage for said first operational mode has a voltage magnitude greater than said negative rail voltage for said second operational mode.

22. The method of claim 21 wherein a magnitude of said negative rail voltage in said second operational mode does not vary responsive to a magnitude of a difference between said maximum voltage overshoot and said current voltage overshoot.

23. The method of claim 22 wherein said operational mode is set by an output of a comparator comparing a voltage derived from said drive current against a predetermined threshold voltage.

24. The method of claim 17 wherein said risk is responsive to an estimated breakdown voltage for a device in a heat rejection path of said inverter that is inversely proportional to a temperature of said multi-level inverter and wherein said calculated maximum voltage overshoot is directly related to said temperature.