Pre-charging circuit for power converters

Patent metadata

Field	Value
Publication number	US-10693367-B1
Application number	US-201916279436-A
Country	US
Kind code	B1
Filing date	Feb 19, 2019
Priority date	Feb 19, 2019
Publication date	Jun 23, 2020
Grant date	Jun 23, 2020

Abstract

In some examples, an electrical power system includes a differential bus including a high-side rail and a low-side rail, a power source configured to generate power, and a bulk capacitor coupled between the high-side rail and the low-side rail, the bulk capacitor configured to filter the power generated by the power source. The electrical power system also includes a converter configured to convert the power filtered by the bulk capacitor and a pre-charging circuit comprising one or more switches and a middle capacitor, the pre-charging circuit configured to pre-charge the bulk capacitor.

First claim

What is claimed is:

1. An electrical power converter comprising:
a differential bus including a high-side rail and a low-side rail;
a power source configured to generate power;
a bulk capacitor coupled between the high-side rail and the low-side rail, the bulk capacitor configured to filter the power generated by the power source;
a converter configured to convert the power filtered by the bulk capacitor; and
a pre-charging circuit comprising one or more switches and a middle capacitor, the pre-charging circuit configured to pre-charge the bulk capacitor, wherein the one or more switches comprise:
a first switch, wherein a drain terminal of the first switch is directly coupled to a first node of the power source;
a second switch, wherein a drain terminal of the second switch is directly coupled to a second node of the power source;
a third switch coupled to the high-side rail, wherein a source terminal of the first switch and a source terminal of the third switch are coupled to a first node of the middle capacitor, and wherein a drain terminal of the third switch is directly coupled to a first terminal of the bulk capacitor; and
a fourth switch coupled to the low-side rail, wherein a source terminal of the second switch and a source terminal of the fourth switch are coupled to a second node of the middle capacitor, and wherein a drain terminal of the fourth switch is directly coupled to a second terminal of the bulk capacitor.

2. The electrical power system of claim 1 ,
wherein the pre-charging circuit is configured to pre-charge the bulk capacitor prior to enabling conversion of the power by the converter, and
wherein the pre-charging circuit is configured to connect and disconnect the high-side rail and the low-side rail while pre-charging the bulk capacitor.

3. The electrical power system of claim 1 ,
wherein the first node of the middle capacitor is coupled between the first switch and the third switch, and
wherein the second node of the middle capacitor is coupled between the second switch and the fourth switch.

4. The electrical power system of claim 1 , further comprising a controller configured to:
activate and deactivate the one or more switches to transfer energy from the power source to the middle capacitor and isolate the middle capacitor from the bulk capacitor; and
activate and deactivate the one or more switches to transfer energy from the middle capacitor to the bulk capacitor and isolate the middle capacitor the power source.

5. The electrical power system of claim 1 , further comprising a controller,
wherein the one or more switches include a first switch coupled between the power source and the middle capacitor and a second switch coupled between the middle capacitor and the differential bus,
wherein the controller is configured to transfer energy from the power source to the middle capacitor at least in part by activating the first switch and deactivating the second switch, and
wherein the controller is configured to transfer energy from the power source to the middle capacitor at least in part by deactivating the first switch and activating the second switch.

6. The electrical power system of claim 1 , further comprising a controller configured to:
deactivate the first switch, the second switch, the third switch, and the fourth switch;
activate the first switch after deactivating the first switch, the second switch, the third switch, and the fourth switch;
deactivate the first switch after activating the first switch;
activate the fourth switch after deactivating the first switch; and
deactivate the fourth switch after activating the fourth switch.

7. The electrical power system of claim 1 , further comprising a controller is configured to:
determine a short circuit condition in the third switch; and
suppress operation in a reverse charging mode in response to determining the short circuit condition in the third switch.

8. The electrical power system of claim 1 , further comprising a controller is further configured to:
measure a discharge time of the middle capacitor; and
determine an estimated capacitance of the bulk capacitor based on the discharge time of the middle capacitor.

9. The electrical power system of claim 1 , further comprising a controller is further configured to:
measure a discharge time of the middle capacitor;
determine whether the discharge time is less than a threshold level; and
determine a short circuit condition in the bulk capacitor in response to determining that the discharge time is less than the threshold time duration.

10. The electrical power system of claim 1 , further comprising a controller is further configured to:
determine whether a voltage across the middle capacitor has a reverse polarity after transferring energy from the power source to the middle capacitor; and
refrain from transferring energy from the middle capacitor to the bulk capacitor in response to determining that the voltage across the middle capacitor has the reverse polarity.

11. The electrical power system of claim 1 , further including a controller is configured to:
detect a ground fault at the high-side rail or at the low-side rail; and
deactivate the first switch, the second switch, the third switch, and the fourth switch.

12. The electrical power system of claim 1 , further comprising:
a first diode coupled in parallel with the first switch and configured to conduct electricity from the first node of the middle capacitor to the first node of the power source;
a second diode coupled in parallel with the second switch and configured to conduct electricity from the second node of the middle capacitor to the second node of the power source;
a third diode coupled in parallel with the third switch and configured to conduct electricity from the first node of the middle capacitor to the high-side rail; and
a fourth diode coupled in parallel with the fourth switch and configured to conduct electricity from the second node of the middle capacitor to the low-side rail,
wherein a drain terminal of the first switch is coupled to the first node of the power source,
wherein a drain terminal of the second switch is coupled to the second node of the power source,
wherein a drain terminal of the third switch is coupled to the high-side rail and the bulk capacitor,
wherein a drain terminal of the fourth switch is coupled to the low-side rail and the bulk capacitor,
wherein the first switch comprises a first n-channel metal-oxide-semiconductor field-effect transistor and a first antiparallel diode, and
wherein the second switch comprises a second n-channel metal-oxide-semiconductor field-effect transistor and a second antiparallel diode.

13. The electrical power system of claim 1 , wherein the middle capacitor comprises a self-healing, non-polarized capacitor.

14. A method for controlling a pre-charging circuit coupled between a power source and a differential bus, the method comprising:
activating and deactivating one or more switches of the pre-charging circuit to transfer energy from the power source to a middle capacitor of the pre-charging circuit and isolate the middle capacitor from a bulk capacitor coupled between a high-side rail and a low-side rail of the differential bus;
activating and deactivating the one or more switches to transfer energy from the middle capacitor to the bulk capacitor and isolate the middle capacitor from the power source;
measuring a discharge time of the middle capacitor; and
determining an estimated capacitance of the bulk capacitor based on the discharge time of the middle capacitor.

15. The met

Assignees

• Rolls Royce Nam Tech Inc
• Rolls Royce Singapore Pte Ltd

Inventors

• Chatterjee Pradip
• Gajanayake Chandana Jayampathi
• Schneider Eric D
• Molligoda Devinda A
• Gupta Amit Kumar

Classifications

• H02M1/325

  with means for allowing continuous operation despite a fault, i.e. fault tolerant converters · CPC title

• H02M1/007

  Plural converter units in cascade (push-pull DC/DC converters with pre-regulator H02M3/3374; DC-AC converters following a DC-DC stage including a high frequency transformer H02M7/4807; DC-AC converters following a DC-DC conversion stage generating periodically varying voltages H02M7/4826) · CPC title

• H02M3/07 Primary

  using capacitors charged and discharged alternately by semiconductor devices with control electrode {, e.g. charge pumps} · CPC title

• H02M3/158

  including plural semiconductor devices as final control devices for a single load · CPC title

• H02M1/36 Primary

  Means for starting or stopping converters · CPC title