Single stage isolated power converter

• US 10,277,114 B2
• Filed: 09/19/2016
• Issued: 04/30/2019
• Est. Priority Date: 09/19/2016
• Status: Active Grant

• Current Assignee: Black & Decker Incorporated (Stanley Black & Decker, Inc.)
• Original Assignee: Black & Decker Incorporated (Stanley Black & Decker, Inc.)
• Inventors: Pant, Pradeep M., Forster, Michael K.
• Primary Examiner(s): Santana, Eduardo Colon
• Assistant Examiner(s): Joseph, Devon A
• Application Number:
  US15/268,960
• Publication Number:
  US 20180083529A1
• Time in Patent Office: 953 Days
• Field of Search: 418400
• CPC Class Codes: B24B 23/02 with rotating grinding tools; Accessories therefor
• CPC Class Codes: B25F 5/02 Construction of casings, bodies or handles B25F5/006, B25F5/008 take precedence
• CPC Class Codes: H02M 1/0025 Arrangements for modifying reference values, feedback values or error values in the control loop of a converter
• CPC Class Codes: H02M 1/4208 Arrangements for improving power factor of AC input
• CPC Class Codes: H02M 1/4258 using a single converter stage both for correction of AC input power factor and generation of a regulated and galvanically isolated DC output voltage H02M1/4241 takes precedence
• CPC Class Codes: H02P 23/26 Power factor control [PFC]
• CPC Class Codes: H02P 27/08 with pulse width modulation
• CPC Class Codes: H02P 29/50 Reduction of harmonics
• CPC Class Codes: Y02P 70/10 Greenhouse gas [GHG] capture, material saving, heat recovery or other energy efficient measures, e.g. motor control, characterised by manufacturing processes, e.g. for rolling metal or metal working

Abstract

Typically, power factor is improved by adding a full power factor correction (PFC) stage between the rectifier and the power converter. This disclosure applies line voltage modulation to the control feedback of an isolated full bridge converter, thereby combining the PFC stage with the isolated power stage and forming a single state isolated power converter.

Claims

1. A power tool, comprising:

a brushless electric motor;

a rectifier circuit configured to receive an incoming alternating current (AC) voltage signal and operable to convert the incoming AC voltage signal to a rectified voltage signal having direct current;

a switching arrangement having a plurality of electronic switches configured as an H-bridge circuit and interposed between the electric motor and the rectifier;

a transformer electrically coupled between the switching arrangement and the electric motor to provide a load voltage to the electric motor;

a control module configured to receive a first feedback signal indicative of voltage applied to the electric motor and a second feedback signal indicative of current applied to the electric motor, and generate a control signal representing a combination of amounts by which the first feedback signal and the second feedback signal respectively deviate from a desired voltage amount and a desired current amount, where the control signal is used to maintain a target setpoint load voltage applied to the electric motor;

a modulator configured to receive a feed-forward AC voltage signal corresponding to the incoming AC voltage signal and the control signal, and to modulate the control signal with the incoming AC voltage signal to produce pulse-width modulated (PWM) signals, the PWM signals having duty cycles set based on the feed-forward AC voltage to form an AC current waveform substantially proportional and in phase with the AC voltage for power factor correction of AC current, the duty cycles being also proportional to the control signal so as to maintain the target setpoint load voltage; and

a drive circuit interfaced with the electronic switches and configured to control switching operation of the electronic switches to modulate the rectified voltage signal in accordance with the PWM signals and output modulated voltage to the transformer.

2. The power tool of claim 1 wherein the control module is further configured to (i) generate a correction signal based on an error signal, wherein the error signal is proportional to a difference between the first feedback signal and the target setpoint voltage;

and (ii) multiply the incoming AC voltage signal with the correction signal to generate the control signal.

3. The power tool of claim 1 wherein the control module is further configured to generate a current control signal in response to the current applied to the electric motor exceeding a current limit.

4. The power tool of claim 1 further comprises a second rectifier circuit electrically coupled between the transformer and the electric motor.

5. The power tool of claim 1 further comprising a bus capacitor disposed in parallel to rectifier circuit.

6. The power tool of claim 1 includes a housing that detachably couples to an adapter, wherein the electric motor resides in the housing and the adapter houses the rectifier circuit, the switching arrangement, the transformer, the drive circuit and the control module.

7. The power tool of claim 6 wherein the adapter includes a power cord connectable to an AC power socket to receive the incoming AC voltage signal.

14. The power tool of claim 1, further comprising an AC voltage sensor configured to produce the feed-forward voltage signal based on the incoming AC voltage signal.

8. An apparatus adaptable to be electrically connected between an alternating current (AC) power supply and a load, comprising:

a rectifier circuit configured to receive an incoming alternating current (AC) voltage signal from the AC power supply and operable to convert the incoming AC voltage signal to a rectified voltage signal having direct current;

a switching arrangement having a plurality of electronic switches configured as an H-bridge circuit and interposed between the load and the rectifier;

a transformer electrically coupled between the switching arrangement and the load to provide a load voltage to the load;

a control module configured to receive a first feedback signal indicative of voltage applied to the load and a second feedback signal indicative of current applied to the load, and generate a control signal representing a combination of amounts by which the first feedback signal and the second feedback signal respectively deviate from a desired voltage amount and a desired current amount, where the control signal is used to maintain a target setpoint load voltage applied to the load;

a modulator configured to receive a feed-forward AC voltage signal corresponding to the incoming AC voltage signal and the control signal, and to modulate the control signal with the incoming AC voltage signal to produce pulse-width modulated (PWM) signals, the PWM signals having duty cycles set based on the feed-forward AC voltage to form an AC current waveform substantially proportional and in phase with the AC voltage for power factor correction of AC current, the duty cycles being also proportional to the control signal so as to maintain the target setpoint load voltage; and

a drive circuit interfaced with the electronic switches and configured to control switching operation of the electronic switches to modulate the rectified voltage signal in accordance with the PWM signals and output modulated voltage to the transformer.

9. The apparatus of claim 8 wherein the control module is further configured to generate a current control signal in response to the current applied to the electric motor exceeding a current limit.

15. The apparatus of claim 8, further comprising an AC voltage sensor configured to produce the feed-forward voltage signal based on the incoming AC voltage signal.

10. An adaptor for powering a power tool having an electric motor, comprising:

a housing;

a rectifier circuit configured to receive an incoming alternating current (AC) voltage signal and operable to convert the incoming AC voltage signal to a rectified voltage signal having direct current;

a switching arrangement having a plurality of electronic switches configured as an H-bridge circuit electrically interconnecting the input signal to the electric motor;

a transformer electrically coupled between the switching arrangement and the electric motor;

a control module configured to receive a first feedback signal indicative of voltage applied to the electric motor and a second feedback signal indicative of current applied to the electric motor, and generate a control signal representing a combination of amounts by which the first feedback signal and the second feedback signal respectively deviate from a desired voltage amount and a desired current amount, where the control signal is used to maintain a target setpoint voltage applied to the electric motor;

a modulator configured to receive a feed-forward AC voltage signal corresponding to the incoming AC voltage signal and the control signal, and to modulate the control signal with the incoming AC voltage signal to produce pulse-width modulated (PWM) signals, the PWM signals having duty cycles set based on the feed-forward AC voltage to form an AC current waveform substantially proportional and in phase with the AC voltage for power factor correction of AC current, the duty cycles being also proportional to the control signal so as to maintain the target setpoint load voltage; and

a drive circuit interfaced with the electronic switches and configured to control switching operation of the electronic switches to modulate the rectified voltage signal in accordance with the PWM signals and output modulated voltage to the transformer,

wherein the rectifier, the switching arrangement, the transformer, the motor drive circuit and the control module residing in the housing, where the housing detachably couple to a mounting portion of the power tool and electrically interfaces the transformer to the electric motor in the power tool.

11. The adapter of claim 10 further comprises a power cord connectable to an AC power socket to receive the incoming AC voltage signal.

12. The adapter of claim 10 wherein the control module is further configured to combine the second feedback signal with the first feedback signal.

13. The adapter of claim 12 wherein the control module is further configured to generate a current control signal in response to the current applied to the electric motor exceeding a current limit.

16. The adapter of claim 10, further comprising an AC voltage sensor configured to produce the feed-forward voltage signal based on the incoming AC voltage signal.