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
  • H02M1/00—Details of apparatus for conversion
  • H02M1/44—Circuits or arrangements for compensating for electromagnetic interference in converters or inverters
• • 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
  • H02M1/00—Details of apparatus for conversion
  • H02M1/12—Arrangements for reducing harmonics from ac input or output
• • 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
  • H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
  • H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
  • H02M7/06—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes without control electrode or semiconductor devices without control electrode
  • H02M7/062—Avoiding or suppressing excessive transient voltages or currents
• • 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
  • H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
  • H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
  • H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
  • H02M7/145—Conversion of ac power input into dc 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 thyratron or thyristor type requiring extinguishing means
  • H02M7/155—Conversion of ac power input into dc 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 thyratron or thyristor type requiring extinguishing means using semiconductor devices only
  • H02M7/1552—Conversion of ac power input into dc 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 thyratron or thyristor type requiring extinguishing means using semiconductor devices only in a biphase or polyphase arrangement

Definitions

• the present invention relates to switching volt- age regulators, and more particularly to a switching voltage regulator in which circuitry is provided to reduce transients generated by reverse current surges in a commutating diode.
• Switching-type voltage regulators typically produce higher levels of RFI (radio frequency interfer ⁇ ence) than dissipative-type regulators.
• the higher noise level of the switching regulator is a general result of the abrupt transition of the switching function.
• Each switching cycle of the regulator may produce a large current surge that is often accompanied by a noise tran ⁇ sient.
• a switching regulator typically employs either thyristor or transistor switching means. Although thy- ristors are somewhat more efficient than transistors in this application, they are also noisier with regard to RFI. The reason for this is that unlike a transistor, a thyristor cannot conduct at an intermediate level. That is to say, it cannot be turned on gradually; when the thyristor is properly biased and its gate terminal is energized, the thyristor conducts fully. Each conduction cycle of the thyristor may produce current surges which affect the operation of other circuit elements and result in the generation of RFI.
• the reverse current flow in the commutating diode is the result of a well known phenomenon commonly referred to as the "minority carrier sweep out effect.”
• the effect is such that a momentary reverse current flows in a forward biased diode during the interval of its transition from a conducting state to a nonconducting state.
• a switching voltage regulator adapted for coupling a source of AC potential to a DC load.
• Thyris- tor full wave rectifier means provide a source of DC potential which is connected to the load through an in ⁇ ductance in series with the load.
• the input of the in ⁇ ductance is shunted by a commutating diode which provides a path for the inductive current when the thyristor means are in the nonconducting phase of their operating cycle.
• Circuit means are provided to reverse bias the commutating diode in advance of each conduction cycle of the thyristor means. Accordingly, the level of RFI con- duction to the AC power line by the switching voltage regulator of the invention is significantly lower than by switching voltage regulators constructed in the manner of the prior art.
• Fig. 1 is a schematic diagram of a switching regulator constructed in accordance with the prior art.
• Figs. 2a-2d illustrate waveforms associated with the circuit of Fig. 1.
• Fig. 3 is a schematic diagram of a switching regulator circuit embodying the invention.
• FIG. 1 there is shown in sche ⁇ matic form a typical switching voltage regulator circuit.
• Reference numeral 2 designates a source of AC potential which is connected to the input of a full wave bridge rectifier 4.
• Rectifier 4 includes two oppositely poled diodes 6 and 8, respectively, and two oppositely poled thyristors 10 and 12, respectively.
• the AC signal from AC source 2 is rectified by recti ier 4 to provide a DC current to load 14 through inductor 16 in series with the load.
• a filter capacitor 18 is connected across the load and a commutating diode 20 is connected across the filter comprising inductor 16 and the capacitor 18.
• thyris ⁇ tors 10 and 12 serve as signal gating means to vary the magnitude of the DC current supplied to the load by rec ⁇ tifier 4.
• the conduction of the thyristors 10 and 12 is controlled by pulses supplied from a thyristor trigger circuit 22. The pulses are conveyed to the gate 11 of thyristor 10 and the gate 13 of thyristor 12 via the transformer 24.
• Transformer 24 has a primary winding 25 connected to the thyristor trigger circuit 22 and a sec ⁇ ondary winding 26 having end terminals 11 and 13 and center tap 15 which are connected by means not shown in the drawing to gate 11 of thyristor 10, gate 13 of thy- ristor 12 and the positive output terminals 15 of recti ⁇ fier 4, respectively.
• the thyristor trigger circuit 22 is powered by the AC source 2 thro ' ugh connections not shown in the drawing.
• the thyristor trigger circuit 22 operating in synchronism with the alternating current, triggers thyristors 10 and 12 into conduction during a portion of each positive and negative alternation of the alternating current cycle.
• This conduction extends over a selected angle (conduction angle) in each half of the cycle.
• the DC current that is delivered to the load therefore, can be varied in magnitude by varying the conduction angles of thyristors 10 and 12.
• the conduc ⁇ tion angles are varied by varying the timing point of the pulses from trigger circuit 22. That is, the pulses are caused to occur at a point representing either a larger or smaller interval in advance of the zero crossing of the AC waveform. Under all circum ⁇ stances, the conduction angles of thyristors 10 and 12 are made to be identical.
• FIG. 2a-2d there are depicted waveforms associated with the operation of the prior art switching voltage regulator of Fig. 1.
• Fig. 2a-2d there are depicted waveforms associated with the operation of the prior art switching voltage regulator of Fig. 1.
• Reverse conduction by diode 20 in effect, short circuits the output of rectifier 4 and produces a high amplitude, extremely short duration reverse current spike in diode 20.
• the waveform of the current flowing in diode 20 is seen in Fig. 2c, wherein the reverse current spike is identified by reference numeral 28.
• the current spike 28 produces an RFI transient which is both radiated within the immediate circuit enclosure, and also propa ⁇ gated along the AC line, causing disturbances in other circuits.
• the transient is illustrated by voltage spike 30 in Fig. 2a which shows the waveform of the AC voltage at input terminals 7 and 9 of rectifier 4.
• Fig. 2d shows the waveform of the current which flows between AC source 2 and terminal 7 of rectifier 4. It will be seen that at time t-
• thyristor 10 stops conducting, and as shown in the waveform of Fig. 2c, diode 20 becomes forward biased and conducts the inductive current sup- p ⁇ ed by inductor 16.
• thyristor 12 is trig ⁇ gered into conduction, and the process described at time t ⁇ is repeated.
• the momentary reverse current in the commutating diode 20 is in effect like a very low impedance shunting the AC line.
• its waveform is that of a high frequency component.
• the impedance of the typical AC input line is very low at line frequency (e.g. 60 Hertz)
• there is sufficient inductance in the wiring to develop a significant amount of reactance at high frequency, such as represented by the short duration current spike in the commutating diode.
• a large voltage is dropped across this reactance as was shown by voltage spike 30 of Fig. 2a.
• Fig. 3 there is shown the switching regulator of Fig.
• circuitry 59 for reducing the level of RFI transients produced by such regulators.
• the circuitry of the invention accomplishes this by "sweeping" the forward charge from the commutating diode 20 just prior to triggering either thyristor 10 or 12.
• any transients developed in the commutating diode 20 cannot be conducted to the AC line, since both thyristors are at this point in time still in a nonconducting state.
• the commutating diode 20 is already in a reverse biased (non ⁇ conducting) state, and so, does not react significantly to the thyristor switched current which developed RFI in the prior art switching voltage regulator such as depic- ted in Fig. 1.
• an additional rectifier means 36 and 38 is provided to main ⁇ tain a charge in an added capacitor 42, which is con ⁇ nected through a switching transistor 46 to the commu- tating diode 20.
• a timing circuit 59 triggers the switching tran ⁇ sistor 46, 50 microseconds in advance of triggering the thyristor. This enables the added capacitor 42 to dis ⁇ charge a portion of its charge through the switching transistor to the commutating diode 20, and by so doing, neutralize the forward bias on the diode.
• the diode will already be in a nonconducting state.
• tran- sistor 46 has its source terminal 45 connected to the cathode of commutating diode 20, and its gate 44 is con ⁇ trolled by optical coupler 48.
• Optical coupler 48 is an isolating device comprising a photo-transistor 48a acti ⁇ vated by an LED (light emitting diode) 48b.
• a source of positive voltage not shown, supplies the operating volt ⁇ age to power the various circuit devices of circuitry 59. Included among these devices is optical coupler 48 in which the driving voltage to LED 48b is supplied from such voltage source through the input terminal labeled "+v.”
• a charged capacitor 42 is connected to the drain terminal 43 of transistor 46 so that when the transistor conducts, the charge in capacitor 42 is conveyed to the commutating diode 20.
• a pair of rectifier diodes 36 and 38 have their anodes connected one to each terminal, respectively, of AC power source 2, to provide a source of positive DC voltage. This positive voltage maintains a charge on capacitor 42 through resistor 40 and supplies the gate voltage to transistor 46 via the voltage regula- tor comprised of resistor 47 and Zener diode 51, and through the series resistor 50. It will be seen that the collector 54 and emitter 56 of the transistor section of optical coupler 48 are connected to the gate 44 and source 45, respectively, of the transistor 46.
• the circuitry 59 controlling the operation of the switching voltage regulator includes a phase variable
• phase variable pulse generator 60 which delivers pulses to one-shot multivibrator 61.
• the phase variable pulse generator 60 is an AC line synchronized circuit of a type well known in the art and commonly used for triggering thyristors.
• One example of such a circuit is shown in Fig. 13.40 of G. ⁇ . TRANSISTOR MANUAL, 1964, 7TH EDITION. While the output from the phase variable pulse generator 60 is for convenience, referred to herein as a "triangular" pulse, it will be understood that the requirements of the cir- cuit are noncritical as to the form, amplitude or dura ⁇ tion of the pulse. The latter, for example, has been found suitable in the range of from 1 to 5 microseconds duration.
• the pulse timing or phase determines the conduction angles of thyristors 10 and 12, which, in turn, determine the output voltage of the regulator.
• the phase variable pulse generator 60 therefore, is set according to the output voltage level desired.
• the tri ⁇ angular pulse output of phase variable pulse generator 60 is fed to one-shot multivibrator 61 which converts the triangular pulse to a 50 microsecond pulse waveform.
• One-shot multivibrator 61 converts the input pulse to a 50 microsecond pulse waveform.
• line frequency pulse generator 62 which provides a square wave pulse at each zero-crossing of the AC line voltage, and which is connected to a bistable circuit comprised of NOR gates 66 and 72.
• a square wave pulse is emitted by line frequency pulse generator 62 upon each zero crossing of the AC line voltage.
• This square wave pulse is fed to terminal 64 of NOR gate 66, which causes the output of gate 66 to go low.
• This low output signal appears at input terminal 70 of NOR gate 72, setting the output of gate 72 high.
• the high output of NOR gate 72 is fed back to input terminal 68 of NOR gate 66, thereby latching NOR gate 66 in a low output state.
• the high output signal of NOR gate 72 is also fed to input terminal 77 of NAND gate 78.
• NAND gate 78 outputs the one-shot multivibrator 61 (a 50 micro ⁇ second pulse) appearing at the other input terminal 80.
• the output of NAND gate 78 is set low.
• the low state output of NAND gate 78 is fed to terminal 85 of inverting driver 81 which provides the level of current necessary, through resistor 86, to dri.ve the LED section 48b of optical coupler 48.
• the low-state signal received from NAND gate 78 causes the output of the inverting driver 81 to go high, which removes the drive to the LED section of optical coupler 48 and causes the transistor section 48a to cease conduction.
• the bias is therefore restored on the gate of transistor 46, enabling it to conduct, and thereby discharge a portion of the charge in capacitor 42 across the commutating diode 20.
• the positive charge which appears at the cathode of commutating diode 20 reverse biases it, which curtails the flow of forward current in the diode from inductor 16.
• the 50 microsecond pulse output of one-shot multivibrator 61 is also fe ' d to one-shot multivibrator 82 which outputs a 10 microsecond wide square wave pulse which is displaced in time from its input by 50 micro ⁇ seconds.
• the trailing edge of the 50 microsecond input pulse is coincident in time with the leading edge of the 10 microsecond output pulse of one- shot multivibrator 82.
• the output from one-shot multi ⁇ vibrator 82 is fed into the thyristor trigger circuit 22, to produce a triggering pulse to trigger one of the alternately conducting thyristors 10 and 12.
• the thyristor trigger circuit 22 is connected to the primary winding 25 of transformer 24.
• the secondary winding 26 of transformer 24 had output terminals 11 and 13 which are connected to the gate terminals of thyris ⁇ tors 10 and 12, respectively.
• the center tap 15 of secondary winding 26 is connected to output terminal 15 of rectifier 4. It will be recalled that the thyristors 10 and 12 are triggered alternately during - -
• each thyristor is triggered into conduction 50 microseconds after commutating diode 20 has been reverse biased thereby precluding any significant interaction between the diode and the current conducted by the thy ⁇ ristor.
• This feedback signal (a 10 microsecond square wave pulse) serves to reset the bis ⁇ table circuit comprised of NOR gates 66 and 72 so that their output, which appears at input terminal 76 of NAND gate 78, is low. This inhibits NAND gate 78 from con ⁇ ducting any additional pulses until the following AC half-cycle, with the result that capacitor 42 will be discharged only once during each half cycle.
• Thyristors 10 and 12 25 amp, 400 volts

Landscapes

• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• Power Conversion In General (AREA)
• Rectifiers (AREA)

Priority Applications (2)

Applications Claiming Priority (2)

Publications (1)

Family

ID=23309997

Family Applications (1)

Country Status (5)

Cited By (3)

Families Citing this family (3)

Citations (1)

Family Cites Families (15)

• 1981
  • 1981-12-28 US US06/335,041 patent/US4412279A/en not_active Expired - Fee Related
• 1982
  • 1982-12-21 WO PCT/US1982/001809 patent/WO1983002370A1/en active IP Right Grant
  • 1982-12-21 JP JP1983600012U patent/JPS58500011U/ja active Pending
  • 1982-12-21 EP EP83900473A patent/EP0097711B1/en not_active Expired
  • 1982-12-21 DE DE8383900473T patent/DE3270050D1/de not_active Expired

Patent Citations (1)

Also Published As

Similar Documents

Legal Events