CA2331345A1 - Dc to ac converter - Google Patents
Dc to ac converter Download PDFInfo
- Publication number
- CA2331345A1 CA2331345A1 CA002331345A CA2331345A CA2331345A1 CA 2331345 A1 CA2331345 A1 CA 2331345A1 CA 002331345 A CA002331345 A CA 002331345A CA 2331345 A CA2331345 A CA 2331345A CA 2331345 A1 CA2331345 A1 CA 2331345A1
- Authority
- CA
- Canada
- Prior art keywords
- capacitor
- transformer
- diode
- resistor
- current
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
- H02M7/5383—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a self-oscillating arrangement
- H02M7/53832—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a self-oscillating arrangement in a push-pull arrangement
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Dc-Dc Converters (AREA)
Abstract
An electronic transformer consisting of a square wave power oscillator having a diode reverse capacitance serving as frequency tuning, wherein said power oscillator connected to a dc source typicly derived from the ac outlet and said generator is driving a transformer having substantial leakage inductance and the primary of said transformer is connected through a capacitor that forms a resonant circuit with said leakage inductance.
A second capacitor is connected to the junction of said first capacitor and transformer primary and a resistor are in series with said second capacitor .
The voltage developed on said first resistor is proportional to the current in the transformer primary and after rectified it is fed to a diode with apritiable reverse capacitance. This capacitance then will decrease in response to the current and will increase the frequency of said power oscillator and in turn will limit said current to a safe value.
A second capacitor is connected to the junction of said first capacitor and transformer primary and a resistor are in series with said second capacitor .
The voltage developed on said first resistor is proportional to the current in the transformer primary and after rectified it is fed to a diode with apritiable reverse capacitance. This capacitance then will decrease in response to the current and will increase the frequency of said power oscillator and in turn will limit said current to a safe value.
Description
Background of the Invention:
This invention relates to off line resonant converters, in particular to those unregulated in nature i.e. electronic transformers. More importantly those having some form of protection far no toad or overload condition.
Description of the Prior art:
The prior art described below is of a series resonant type. Such converters have simple overload protection but at the cost of much degraded transiFormer construction. In order to answer the need for cost reduction an overload protection consisting of two diodes connected to the do rail and their junction is connected to the resonant capacitor.
The operation of the prior art will be described in reference to figure 1.
Mosfet 1 and mosfet 2 is connected to do rail 3 positive and 4 negative. The drive oscillator 5 providing square wave pulses to said mosfet l and mosfet 2.
The junction of said mosfet 1 and mosfet 2 is connected to transformer 6 having appreciable leakage inductance and the other side; of the primary winding 7 is connected to resonant capacitor 8. The other side of capacitor 8 is connected to the negative rail 4. The current limiting first diode 9 is connected between do rail positive 3 and to the other side of capacitor8. Second limiting diode 10 is connected between negative rail of 4 and the cathode of diode 10 is connected to the anode of diode 9.
Transformer 6 having a secondary winding 11 connected to load 12.
By decreasing the load resistance 12, the voltage across capacitor 8 will increase until the rail voltage. If the load 12 is a short circuit, the diode 9~ and diode ' i 0 will limit the current to approximately twice of the nominal value.
This has two major disadvantages. Upon short circuit the flux density in the core will rise to double of the nominal, and the current in the transformer will do the same.
__. ___ _.-____ __ This is self defeating -because even-though the mosfets are protected they will have to endure twice as much current, translating 4 times higher heat loss then nominal, which means more e~pens-ive mosfets. Furthermore the doubling of the ~u~derasity sill require more then double cross sectional area for the transformer ~. The wire dimensioning suffers similarly coupled with the need for a much increased core diameter.
To sum it up this inexpensive overload protection leads to an n expensive overall solution.
This is not including applications requiring rectification that would demand much larger heatsinking.
The present invention is free from the shortcomings of the garevions art yielding a truly low cost converter with low thez-n~ai gnat current stresses under overlo2td conditions Description of the ~'referreri Embodiment:
The present invention will be described in relation to fig. 2 mosfet l 3 and mosfet 14 is connected to do rail l 5 positive and 1 S
negative.
The junction of the mosfet 13 andl4 is connected to transformer 28 having primary 27 and secondary windings 17. The other side of primary 27 is connected to resonant capacitor 18 and the other side of capacitor 18 is connected to negative rail l~.The junction of said capacitor 18 and primary winding 27 is connected to capacitor 19 in series with sensing resistor 25. The other side of resistor 2_'i is connected to ground.
square wave oscillator 2fl having a tuning capacitance using diode 2l,having sustentiai reverse capacitance. The voltage across sensing resistor 2_'i is rectified by diode 22 and filtered by capacitor 25. This rectified voltage is fed through resistor 23 to diode 21. The diode 21 is connected to the oscillator via capacitor 23. ~scillator 20 outputs are driving mosfet 13 and 14. Under nominal conditions the voltage across resistor 25 is less then a diode drop. If load 24 connected to the secondary 17 having a short condition, then the voltage across sensing resistor 25 will be greater then a diode drop and start tuning the oscillator to a higher frequency thereby reducing current .
This action will bring about a safe current limit while increasing the converter frequency proportionally so the magnetics will operate ~viin safe limits under overload conditions. The amount of overload can be desyd ~y the; appropriate choice of a ~ener diode placed in series w~t~i the voltage developed 'lOy rcetifier diode 22.
Typical ratios of i.3 0-~~rload/n~minal is easily achieved.
The present invention en .~. resonant converter of unregulated nature to be protected under overlap r~ion by loss-less sensing said condition and using this information sets a Limit to the stresses on both the semiconductor and the magnetics thereby yielding a high frequency high performance elecWonic transformer at a low cost.
It is believed that the method used to obtain such a converter described in present invention is not obvious to those trained in the art and is of significant improvement in relation to the prior art ,therefore the following are claimed
This invention relates to off line resonant converters, in particular to those unregulated in nature i.e. electronic transformers. More importantly those having some form of protection far no toad or overload condition.
Description of the Prior art:
The prior art described below is of a series resonant type. Such converters have simple overload protection but at the cost of much degraded transiFormer construction. In order to answer the need for cost reduction an overload protection consisting of two diodes connected to the do rail and their junction is connected to the resonant capacitor.
The operation of the prior art will be described in reference to figure 1.
Mosfet 1 and mosfet 2 is connected to do rail 3 positive and 4 negative. The drive oscillator 5 providing square wave pulses to said mosfet l and mosfet 2.
The junction of said mosfet 1 and mosfet 2 is connected to transformer 6 having appreciable leakage inductance and the other side; of the primary winding 7 is connected to resonant capacitor 8. The other side of capacitor 8 is connected to the negative rail 4. The current limiting first diode 9 is connected between do rail positive 3 and to the other side of capacitor8. Second limiting diode 10 is connected between negative rail of 4 and the cathode of diode 10 is connected to the anode of diode 9.
Transformer 6 having a secondary winding 11 connected to load 12.
By decreasing the load resistance 12, the voltage across capacitor 8 will increase until the rail voltage. If the load 12 is a short circuit, the diode 9~ and diode ' i 0 will limit the current to approximately twice of the nominal value.
This has two major disadvantages. Upon short circuit the flux density in the core will rise to double of the nominal, and the current in the transformer will do the same.
__. ___ _.-____ __ This is self defeating -because even-though the mosfets are protected they will have to endure twice as much current, translating 4 times higher heat loss then nominal, which means more e~pens-ive mosfets. Furthermore the doubling of the ~u~derasity sill require more then double cross sectional area for the transformer ~. The wire dimensioning suffers similarly coupled with the need for a much increased core diameter.
To sum it up this inexpensive overload protection leads to an n expensive overall solution.
This is not including applications requiring rectification that would demand much larger heatsinking.
The present invention is free from the shortcomings of the garevions art yielding a truly low cost converter with low thez-n~ai gnat current stresses under overlo2td conditions Description of the ~'referreri Embodiment:
The present invention will be described in relation to fig. 2 mosfet l 3 and mosfet 14 is connected to do rail l 5 positive and 1 S
negative.
The junction of the mosfet 13 andl4 is connected to transformer 28 having primary 27 and secondary windings 17. The other side of primary 27 is connected to resonant capacitor 18 and the other side of capacitor 18 is connected to negative rail l~.The junction of said capacitor 18 and primary winding 27 is connected to capacitor 19 in series with sensing resistor 25. The other side of resistor 2_'i is connected to ground.
square wave oscillator 2fl having a tuning capacitance using diode 2l,having sustentiai reverse capacitance. The voltage across sensing resistor 2_'i is rectified by diode 22 and filtered by capacitor 25. This rectified voltage is fed through resistor 23 to diode 21. The diode 21 is connected to the oscillator via capacitor 23. ~scillator 20 outputs are driving mosfet 13 and 14. Under nominal conditions the voltage across resistor 25 is less then a diode drop. If load 24 connected to the secondary 17 having a short condition, then the voltage across sensing resistor 25 will be greater then a diode drop and start tuning the oscillator to a higher frequency thereby reducing current .
This action will bring about a safe current limit while increasing the converter frequency proportionally so the magnetics will operate ~viin safe limits under overload conditions. The amount of overload can be desyd ~y the; appropriate choice of a ~ener diode placed in series w~t~i the voltage developed 'lOy rcetifier diode 22.
Typical ratios of i.3 0-~~rload/n~minal is easily achieved.
The present invention en .~. resonant converter of unregulated nature to be protected under overlap r~ion by loss-less sensing said condition and using this information sets a Limit to the stresses on both the semiconductor and the magnetics thereby yielding a high frequency high performance elecWonic transformer at a low cost.
It is believed that the method used to obtain such a converter described in present invention is not obvious to those trained in the art and is of significant improvement in relation to the prior art ,therefore the following are claimed
Claims (10)
1. An unregulated resonant converter consisting at least two switching elements a first and second switch driven by a square wave oscillator having a first diode with appreciable reverse capacitance as a tuning element.
Said first and second switches connected to a dc supply and to a transformer with substantial leakage inductance.
A first capacitor serving as resonant capacitor connected in series with the primary of said transformer and this junction are connected to a second capacitor in series with a sensing resistor. The voltage developed across the sensing resistor is rectified by second diode , filtered by a third capacitor and said voltage is fed via first resistor to change the reverse voltage across said first diode having substantial reverse capacitance. The voltage developed across the sensing resistor is proportional to the current and vill tune the oscillator above the resonance so as to keep sqaid current from reaching destructive values.
Said first and second switches connected to a dc supply and to a transformer with substantial leakage inductance.
A first capacitor serving as resonant capacitor connected in series with the primary of said transformer and this junction are connected to a second capacitor in series with a sensing resistor. The voltage developed across the sensing resistor is rectified by second diode , filtered by a third capacitor and said voltage is fed via first resistor to change the reverse voltage across said first diode having substantial reverse capacitance. The voltage developed across the sensing resistor is proportional to the current and vill tune the oscillator above the resonance so as to keep sqaid current from reaching destructive values.
2. A tunable oscillator as in claim 1. Having a first diode as the essential tuning element.
3. A first diode as in claim 1 and 2 having a substantial reverse capacitance
4. A pair of switching element driven by said oscillator as in claim 1 connected to a dc rail and to a transformer
5. A transformer as in claim1 and 4 having a substantial leakage inductance
6. A first capacitor as in claim 1 connected in series with said transformer primary serving as resonant capacitor
7. A second capacitor as in claim 1 connected to the junction of said first capacitor and transformer primary and said capacitor is in series with a first resistor.
8. A first resistor as in claim 1 and 7 serving as current sensing resistor having a second diode to rectify the voltage across it and a third capacitor.
9. third capacitor as in claim 1 and 8 to filter the rectified ac.
10. Second resistor as in claim 1 feeding first diode with the voltage developed in proportional to the current through the primary of said transformer so as to tune said oscillator by reducing its reverse capacitance to increase frequency and keep device stresses to a minimum. A zener diode in series with said second resistor maybe employed to set suitable threshold for the current through the primary of said transformer.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002331345A CA2331345A1 (en) | 2001-01-12 | 2001-01-12 | Dc to ac converter |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002331345A CA2331345A1 (en) | 2001-01-12 | 2001-01-12 | Dc to ac converter |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2331345A1 true CA2331345A1 (en) | 2002-07-12 |
Family
ID=4168114
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002331345A Abandoned CA2331345A1 (en) | 2001-01-12 | 2001-01-12 | Dc to ac converter |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2331345A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108695829A (en) * | 2017-04-03 | 2018-10-23 | 维洛西门子新能源汽车法国简式股份公司 | Guard method, protective device, electrical system and the charger system of resonance circuit |
-
2001
- 2001-01-12 CA CA002331345A patent/CA2331345A1/en not_active Abandoned
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108695829A (en) * | 2017-04-03 | 2018-10-23 | 维洛西门子新能源汽车法国简式股份公司 | Guard method, protective device, electrical system and the charger system of resonance circuit |
| CN108695829B (en) * | 2017-04-03 | 2022-05-17 | 维洛西门子新能源汽车法国简式股份公司 | Protection method and protection device for resonant circuit, electrical system and charger system |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued | ||
| FZDE | Discontinued |
Effective date: 20050112 |