Switched mode power supply for single-phase boost commercial AC users in the range of 1 kw to 10 kw

• US 5,255,179 A
• Filed: 06/28/1991
• Issued: 10/19/1993
• Est. Priority Date: 07/23/1990
• Status: Expired due to Fees

• Current Assignee: Boze N. Zekan, Luciano Dellasmirra
• Original Assignee: Boze N. Zekan, Luciano Dellasmirra
• Inventors: Dellasmirra, Luciano, Zekan, Boze N.
• Primary Examiner(s): Voeltz, Emanuel T.
• Application Number:
  US07/723,029
• Time in Patent Office: 844 Days
• Field of Search: 363/8, 363/63, 363/65, 363/71, 363/96, 363/135, 363/139, 363/131, 363/133, 363/24, 363/25, 307/9.1, 307/10.1, 307/150, 307/151
• US Class Current: 363/133
• CPC Class Codes: F02B 2075/027 four
• CPC Class Codes: H02M 7/48 using discharge tubes with control electrode or semiconductor devices with control electrode

Abstract

A DC to AC power converter is disclosed which is connectable to a DC source, and including a first and second pair of switches which converts the DC source directly to AC by alternately switching between each of the first pair of switches at high frequency modulation, and between second pairs of switches alternately switching at each of the half cycles of the low frequency fundamental output voltage, for producing a positive pulse train and a negative pulse train. A transformer boosts the source voltage to the desired high voltage of the output of the converter circuit. A filter is connectable to an AC load and having a plurality of damping modes for extracting fundamental frequency from the output of the transformer, and having a control responsive to a signal for switching between damping modes. A sine wave oscillator generates a sine wave at the fundamental frequency. Feedback circuits maintain the AC output at the fundamental frequency.

Claims

1. A DC to AC power converter, comprising:

a converter circuit connectable to a low voltage DC source, and including a first and second pair of switch means for converting the DC source to an AC voltage by alternately switching between each switch means of the pair of switch means for producing a pulse train and by alternately switching between said first and second pairs of switch means, for producing a positive half cycle from the pulse train of the first pair of switch means and a negative half cycle from the pulse train of the second pair of switch means,

a first pair of transformers for boosting the voltage of the positive half cycle and a second pair of transformers for boosting the voltage of the negative half cycle, each of said transformers having a unidirectional short path for resetting the flux of the core of the transformer whereby one transformer is resetting while the other of the pair is conducting,

a filter means connected between an AC load and the first and second pair of transformers and having a plurality of damping modes for extracting a fundamental frequency from the output of the transformers, and having a control means responsive to a signal for switching between damping modes,

a sine wave oscillator for generating a sine wave at the fundamental frequency, and

feedback means for maintaining the AC at the fundamental frequency by comparing the output of the filter means with the sine wave and producing the signal, which signal is correlatable to the difference therebetween and sending the signal to the filter means.

2. A power converter as claimed in claim 1 wherein said feedback means includes

an integrator circuit for measuring the flux of the output of the filter means and the flux of sine wave

a comparator circuit for comparing the respective fluxes, and

a control circuit responsive to the output of the comparator circuit for generating the signal for switching modes of the filter means correlatable to increase in damping when the flux of the output of the filter means exceeds that of the sine wave after a half cycle transition, and to decrease in damping when the flux of the output of the filter means exceeds the flux of the sine wave before a half cycle transition.

3. A power converter as claimed in claim 2 wherein said filter means comprises a first and second filter connected between the output of the first and second pairs of transformers and ground, and adapted for receiving the positive and negative half cycles of the AC respectively;

said first and second filter each comprising in series

a bank of capacitors connected in parallel and switchable therebetween responsive to the control means and having the AC load connected thereacross,

an inductor having a switchable short circuit path thereacross for shorting the inductor during the opposite half cycle, and

a filter switch means which is continuously triggered during the half cycle and off during the opposite half cycle, and having a unidirectional path from ground across the filter.

4. A power converter as claimed in claim 3 wherein the first and second filters have a common bank of capacitors to each of said first and second filters.

5. A power converter as claimed in claim 4 wherein said bank of capacitors comprise a plurality of capacitors which are switched into and out of the first and second filter as the bank is successively switched.

6. A power converter as claimed in claim 5 wherein said inductors of said first and second filters are wound on a common core.

7. A power converter as claimed in claim 6 wherein said switchable short path includes an SCR and said filter switch means is an SCR.

8. A power converter as claimed in claim 5 wherein the switching of each switch means of a pair of switch means is at a chopping frequency and the switching between said first and second pair of switch means is at twice the fundamental frequency.

9. A power converter as claimed in claim 8 wherein the chopping frequency exceeds the fundamental frequency in the order at least 400 times.

10. A power converter as claimed in claim 9 wherein the chopping frequency equals or exceeds 25 kilohertz.

11. A power converter as claimed in claim 10 wherein the fundamental frequency is less than or equal to 60 hertz.

12. A power converter as claimed in claim 11 wherein said unidirectional path to ground for resetting the flux of the core of the transformer comprises a second primary winding on each of the transformers connected between the DC source and ground and having a diode for restricting the flow of current away from ground.

13. A power converter as claimed in claim 12 wherein said switch means are MOSFETS having a controller for switching the MOSFET between an on and off state, said controller including a regulator responsive to the instantaneous difference between an attenuated output voltage and an attenuated sine wave voltage for regulating the time in which the switch is in the on or off state.

14. A power converter as claimed in claim 13 wherein said transformers are ferrite transformers.

15. A power converter as claimed in claim 14 wherein said converter is connected to an unregulated rectified output of an AC alternator of a vehicle.

16. A power converter as claimed in claim 15 wherein said converter further includes a throttle control means responsive to variations in the output load for regulating the speed of the engine of the vehicle.

17. A power converter as claimed in claim 16 wherein said controller switches said first and second pair of switches at a constant pulse width for producing a constant high DC positive voltage or negative voltage, respectively.