Method and apparatus for energy conversion utilizing circuit phase and time variables

• US 6,324,080 B1
• Filed: 09/08/1998
• Issued: 11/27/2001
• Est. Priority Date: 09/10/1997
• Status: Expired due to Fees

• Current Assignee: GE Medical Systems Norway AS (General Electric Company)
• Original Assignee: GE Medical Systems Norway AS (General Electric Company)
• Inventors: Laeuffer, Jacques
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): Laxton, Gary L
• Application Number:
  US09/149,644
• Time in Patent Office: 1,176 Days
• Field of Search: 363/15, 363/16, 363/17, 363/24, 363/25, 363/98, 363/132, 363/133, 323/911
• US Class Current: 363/25
• CPC Class Codes: H02M 3/3376 with automatic control of output voltage or current
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

A conversion apparatus having transistors, comprising means for inverting a DC voltage in order to obtain an AC voltage, means for filtering the AC voltage, including at least one parallel inductor L_p, the device being capable of operating above a resonant frequency F_p. The conversion apparatus comprises means for predicting a zero crossing of the instantaneous current I_1p in the parallel inductor L_p, and means for causing a transistor of the device to switch if a zero crossing of the current I_1p is predicted.

Claims

1. Apparatus for converting DC voltage to AC voltage comprising:

an inverter for receiving DC voltage and providing unfiltered AC voltage at an operating frequency, said inverter having transistors operable between conductive and nonconductive states;

filtering means for filtering said AC voltage, said filtering means having at least one resonant circuit formed of a capacitor and a first inductor connected in parallel and possessing a first resonant frequency determined by the values of said capacitor and said first inductor with said first resonant frequency being different from said operating frequency;

means for measuring current flowing in said filtering means through said first inductor; and

comparator means responsive to the amplitude of said current to provide an output signal for switching at least one of said transistors from its nonconductive state to its conductive state at a pre-selected time period.

2. The apparatus according to claim 1 wherein said filtering means includes a second inductor connected in series with said capacitor with said second inductor and capacitor possessing a second resonant frequency determined by the values of said capacitor and said second inductor so that the filtering means has a double resonance, whereby the output of the converting apparatus is a monotonically increasing function of said operating frequency, said operating frequency being greater than said first resonant frequency.

3. The apparatus according to claim 1 wherein the filtering means includes a capacitor and an inductor which are arranged in series at the output of the inverter.

4. The apparatus according to claim 1 wherein said inverter includes at least one half-bridge having two transistors, each transistor being provided with a freewheeling diode.

5. The apparatus according to claim 1 further comprising a step-up voltage transformer, having a primary and secondary winding with the primary winding coupled to said inverter and voltage rectification means connected to the secondary winding of the transformer.

6. Apparatus as claimed in claim 1 wherein said pre-selected time period occurs when said amplitude of said current approaches zero.

7. Apparatus according to claim 1 comprising:

means for measuring the instantaneous value of said current;

means for calculating the value of the derivative of said current with respect to time;

means for calculating a value derived by the product of said derivative of said current multiplied by a predetermined time period; and

wherein said comparator means compares the instantaneous value of said current and said value for developing said output signal.

8. The apparatus according to claim 7 comprising a transformer for measuring said current and providing a first voltage representative of the instantaneous value of said current;

a circuit for differentiating said first voltage and providing a second voltage representative of the product of said derivative of said current multiplied by said predetermined time period;

wherein said comparator means compares said first and second voltages.

9. The apparatus according to claim 8 wherein said filtering means includes a second inductor connected in series with said capacitor and with said second inductor and capacitor possessing a second resonant frequency determined by the values of said capacitor and said second inductor so that the filtering means has a double resonance, whereby the output of the converting apparatus is a monotonically increasing function of said operating frequency, being greater than said first resonant frequency.

10. The apparatus according to claim 8 wherein the filtering means includes a capacitor and an inductor which are arranged in series at the output of the inverter.

11. The apparatus according to claim 7 wherein said filtering means includes a second inductor connected in series with said capacitor with said second inductor and capacitor possessing a second resonant frequency determined by the values of said capacitor and said second inductor so that the filtering means has a double resonance, whereby the output of the converting apparatus is a monotonically increasing function of said operating frequency, said operating frequency said operating frequency being greater than said first resonant frequency.

12. The apparatus according to claim 7 wherein the filtering means includes a capacitor and an inductor which are arranged in series at the output of the inverter.

13. A method of converting DC voltage to AC voltage comprising the steps of:

receiving said DC voltage and providing unfiltered AC voltage at an operating frequency utilizing transistors operable between conductive and nonconductive states;

filtering said AC voltage utilizing a resonant circuit formed of a capacitor and an inductor connected in parallel and possessing a resonant frequency determined by the values of said capacitor and said inductor said resonant frequency being different from said operating frequency;

measuring the amplitude of current flowing through said inductor; and

providing an output signal in response to the measured amplitude of said current for switching at least one of said transistors from its nonconductive state to its conductive state at a pre-selected time period.

14. The method according to claim 13 wherein providing said output signal includes the steps of:

measuring the instantaneous value of said current;

calculating the derivative of said instantaneous current with respect to time;

calculating a value derived by the product of this derivative multiplied by a predetermined period and comparing said value with a reference value, said preselected time period occurring when said derived value is less than the reference value.

15. The method according to claim 14 wherein said reference value is said current flowing through said inductor.

16. A method as claimed in claim 13 wherein said pre-selected time period occurs when said amplitude of said current approaches zero.