Title of Invention | "A LINEAR BIPOLAR CURRENT REGULATED DC POWER SUPPLY FOR INDUCTIVE LOADS. |
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Abstract | This invention relates to a linear bipolar current regulated DC power supply for inductive loads comprising a bipolar source of input signal (1) connected to an error amplifier (2) characterized in that said amplifier connected to a bipolar output stage (3) through an integrator (2a) comprising resistance R6 and capacitor C2 to decide the output ramp rate such as herein described, the output of the bipolar output stage connected to a load (4) through a shunt (5), an output filter (4a) connected across the output of the power supply, a feedback circuit (6) connected between the output of the power supply and the input of the error amplifier and the input of the integrator, a zero ampere start (7) circuit being connected across the integrator capacitor. |
Full Text | s 2 i This invention relates to a linear bipolar current regulated DC potter supply for inductive loads. The power supply is used -for precision beam transport applications. The power supply is designed to energise a steerer magnet with direct current stabilized to 25 to 50 ppa of max i mum output current. The power supply is a DC current bipolar output power supply with extremely low cross over distortion designed -for use with beam steerer where high stability is required. The bipolar power supply is as such known in the art and comprises a bipolar source o-f input signal connected to an error amplifier. The output o-f the error amplifier ia connected to a bipolar output stage which is connected to the load through a shunt. A feed back quiscient current control circuit is connected between bipolar output stage and the ccMuson terminal of input signal and error amplifier. There are certain disadvantages associated with the prior art. One of the main disadvantage is that programmable ramp rate control required to avoid large back e.m.f generated by the magnet, for the safety of the power supply and the magnet is not there. s 3 s Another disadvantage is that the conventional power supply does not. have the means to compensate the inductive loads. Yet another disadvantage is that the zero ampere start -facility of the current is not there with the conventional power supply which is required to avoid output spikes when main power is turned ON. Still another disadvantage is that the stability o-f the current of the conventional powersupply is poor. There-fore the main object o-f this invention is to provide a power supply which obviates the disadvantage associated with the conventional power supply. Another object o-f this invention is to provide a power supply having the weans to provide zero ampere start facility o-f the current. : 4 : Yet further object of this invention is to provide a power supply having means to provide programmable ramp rate control facility. Still another object of this invention is to provide a power supply having the means to compensate the inductive loads. According to this invention there is provided a linear bipolar current regulated DC power supply for inductive loads comprising a bipolar source of input signal connected to an error amplifier characterized in that said amplifier connected to a bipolar output stage through an integrator comprising resistance Re and capacitor Ca to decide the output ramp rate such as herein described, the output of the bipolar output stage connected to a load (4) through a shunt, an output filter connected across the output of the power supply, a feedback circuit connected between the output of the power supply and the input of the error amplifier and the input of the integrator, a zero ampere start circuit being connected across the integrator capacitor. s 5 i In accordance with this invention the linear bipolar current regulated DC power supply for inductive load has an integrator connected in between error amplifier and bipolar output stage. Further an output filter is provided across the output of the power supply. Also a zero ampere start circuit is connected to the integrator. The feed back circuit according to this invention is connected to the bipolar output stage through a shunt. The integrator is provided to decide the output ramprate. The zero ampere start is provided to discharge the integrator when the power supply is in Off condition to ensure a zero ampere start when the power supply is put ON irrespective of the input. Further a output filter consisting of a capacitor is provided to compensate for the large inductive loads and to make the power supply less susceptible to osci 1 lations. A linear bipolar current regulated DC power supply for inductive loads according to a preferred embodiment is herein described and illustrated in the accompanying drawings wherein: Fig. 1 shows the block diagram of the conventional pouter supply. Fig. 2 shows the block diagram of the power supply of the present invention and, Fig. 3 shows the circuit diagram of the power supply. Referring to the drawings particularly fig. 1 linear DC power supply as known in the art comprises a bipolar source of input signal 1 the output of which is connected to the input terminal of an error amplifier 2 which is connected to the input terminal of a bipolar output stage 3. The output terminals of the bipolar output stage 3 is connected to a load 4 through a shunt 5. Further the bipolar stage 3 is interconnected with a feed back quiscient current control circuit 6. The quiscient current control circuit 6 is also connected to the common terminal of the bipolar source 1 and error amplifier 2. A load 4 is connected to an output terminal of the bipolar output stage 3 through a shunt 5. The common terminal of the shunt 5 and load 4 is connected to the quiscient current control circuit 6. 8 7 S The current control circuit 6 is provided to establish the quisclent current in both the positive and negative pass transistors to eliminate the cross over distortion. Reference is now made to fig. 2 which shows the block diagram of the linear bipolar current regulated DC power supply for inductive loads of the present invention. The power supply comprises a bipolar source of input signal 1 connected to an error amplifier 2- The output of the error amplifier is connected to an integrator 2a which is provided to decide the output ramp-rate. The output of integrator 2a is connected to a bipolar output stage 3 which is connected to a load 4 through a shunt 5. An output filter 4a is connected across the output of the power supply. The output filter 4a comprises a capacitor provided to compensate the large inductive loads and to make the regulator/ supply less susceptible to oscillations. The common terminals of the load 4, shunt 5 and output filter 4a is connected to a feed back circuit 6 which is connected to I 8 s the common terminal of the bipolar source 1 and error amplifier 2. A zero amplifier start 7 its connected to the common point of the error amplifier 2, integrator 2a and feed back circuit 6. The zero ampere start is provided to keep the integrator discharge t*hen the regulator/power eupply is in Off condition. When the regulator is put ON the output always starts from zero ampere regardless to the input control signal. Reference is not* made to fig. 3 wherein the circuit diagram of bipolar current regulator/power supply is shown. The bipolar current regulator is basically a voltage regulator regulating the voltage across the shunt and the voltage across the shunt is directly propotional to the load current. As the current regulator is a bipolar current regulator it comprises an output stage having two type of transistors connected in a push-pull configuration. Transistor 02 is an NPN type transistor whose collector is connected to the positive terminal of voltage source 1. Transistor QT is PNP type transistor whose collector is connected to 8 9 8 the negative terminal of the voltage source 2. The emitter* of the transistor Q-^ ant* ®3 are connected together and form a common point G for the control circuit. The negative side terminal of the positive voltage source i is connected to the positive terminal o-f the voltage source 2. which are connected together and is connected to the load 4. The other end of the load 4 is connected to the common point 6 through a shunt resistance ft 12. The shunt R 12 is connected in series with the load 4 so that the voltage developed across the shunt R12 is directly propotional to the load current. The control circuit consist of a limited gain limited bandwidth error amplifier 2 connected to a integrator 2a through the resistance Rg and R^. The control circuit is provided to compare the control input voltage with the voltage from the shunt RJ2 *nd regulates the output voltage through the output stage transistor Q^ And 63 in the control circuit. The error amplifier 2 is a noninverting difference amplifier with a DC gain of 3000. : 10 s The gain is kept so high that even a small error between the input signal and feed back can be amplified for output correction. This stage also has a reactive -feed back in order to limit its frequency bandwidth to reduce the noise. A capacitor Cj is provided across feed back resistance R^ to Minimise output voltage error due to the noise. Capacitor C^ shunts feed back resistance R^ at high noise frequencies. in case of DC the capacitor C| acts as an open circuit so that the effective feed back impedance remain equal to the resistance R^ only and hence the gain remain 5000 apprOKimatly. But when frequency increases the capacitive reactance of capacitors decreases and the effective feed back impedance decreases and hence the gain decreases. Therefore the high frequencies are not amplified and hence stability of the power supply against the noise increases. The error amplifier 2 is followed by the integrator 2a for the purpose to limit the rate of rise of the output current. When there is : 11 no error the output of the error amplifier 2 is virtually zero. If the control input changes the output from the error amplifier 2 at point C is clamped in positive or negative direction depending on the polarity of the error at a level determined by the variable limit circuit 5. The output of the variable limit circuit 5 is set between 0.2V to IV. Resistance R6 and capacitor G£ now acts as components of a simple integrator with operational amplifier 2A. Now the integration speed is determined by resistance R^, Capacitor (>> and the input voltage to the integrator. To calculate the ramp time formula is t- Vo » -yjt wherein Re Vo r Output erf the integrator which is voltage across shunt (R12> Vi - Input to the integrator which is clamped voltage at Point t - Time required to reach the output ramp to the set value. RC - s 12 s Suppose the regulator its set 4 or +5A th«r» the voltage across shunt (R^* will be =*~0.5V So Vo - 8.5V Vi - is the output of error amplifier which can be 8.2V to IV if limitter is set to Vo - 0.5V R^ - 3M C2 - 3.3uF tm_v «-VoXRC - a. max . . ~ ~ ~5X5X5. 3 Vimin 0.2 *• 24.75 sec. if limitter is set to R6 - 3M C2 * 3.3uF tmin -VoXRC - 0.5X3X5.5 Vimax 1 » 4.95 SBC. From the calculation it is clear that the •full scale ramp time can be set -fro* 4.95 sec to 24.75 sec, so t*e can programe the ramp by setting the variable limit circuit to any value between 0.2V to IV. i 13 The resistance R7 and the relay R^ are provided to atop the generation of spikes when main power 11 and 22 is switched ON. The contact of relay RLJ is normally in close position, when the regulator is in the Off position it discharges C2 through th* resistance R7. When the power is switched ON the contact of relay RL1 becomes open and the capacitor C2 starts charging always from zero volt. Hence the regulator always starts at zero ampere and then ramp to the value which is set by the input control signal 1. The amplifier 2A with driver Transistor Qj form the driver for the output transistors Qg and Bhj. The transistor Ql« 32, Q3 and 2A makes a single amplifier with capacitive feedback as C2 having output at point filter compensate for large inductive load. For high current bipolar regulators a high value bipolar 5 14 I capacitor is required. Two electrolytic capacitors are connected back to back to make a big bipolar capacitor. A resistor R^j is also connected in series with C^ to limit initial surg currents. To ensure stability and repeatability a thermally stable SHUNT the resistance of the SHUNT will not change with time due to heating. So the output remain free of thermal drift. gf power supply working through Exaf>plas The regulator /power supply ha» a feedback resistance R2 and input resistance Rj. The gain of the regulator depends upon Rj and R^ anc* *9 «Qual to &QQ-R2/R1. The ratio between R^ and R2 i« 20i 1 corresponds to the ratio of the input signal (10M) and 0,5V for 5A of aax current across 0. 1R shunt resistance. i 15 : Example!- for +§A output current for a +10V input signal. The control input voltage -from source 6 is fed to the percision resistor Rj, another per ci si on resistor 1^ gives direct feedback from reference shunt. The junctions of the resistor point is fed to the non—inverting input of error amplifier 2. initially point A is +ve so the output of 2 goes +ve and clamped to 0.2V. The output of 2A will go We and emitter of Qj(D> becomes +ve. This way Qj will conduct and Qg remains OFF because +ve at the base. The current starts flowing from 6 to 3 and a -ve voltage is developed across SHUNT As soon as it becomes -0.5V point (A) will be zero and the error ampere output becomes zero, hence the input to the integrator becomes zero, so no more increase in base drive Q^. This way circuit stabilizes. This way the output current locks to +5A. : 16 s Examples- for -5A output current for a -10V input signal. If a -10V signal is fed to the input resistance fij, point becomes -ve, s»o the output of the error amplifier will be clamped to -0.2V. The output integrator driver op - amp. emitter of Q* (D) becomes -ve. This time Q-? will conduct •* •-/ and Q'j remains off because of +ve base drive1. The current start flowing from 8-M3 and keep on increasing until the voltage across shunt 'Rj-?) becoines +0.5V. As soon as shunt voltage becomes 0.5V point, A will be QV and the error amplifier output becomes 0V. Hence the jjuput to the ivstegr «st-or becomes GV» so no tta.it & incifeaae in base drive to Q-T. This way the output current \J stabilize to -5A. WE CLAIM: 1. A linear bipolar current regulated DC power supply for inductive loads comprising a bipolar source of input signal (1) connected to an error amplifier (2) characterized in that said amplifier connected to a bipolar output stage (3) through an integrator (2a) comprising resistance R6 and capacitor C2 to decide the output ramp rate such as herein described, the output of the bipolar output stage connected to a load (4) through a shunt (5), an output filter (4a) connected across the output of the power supply, a feedback circuit (6) connected between the output of the power supply and the input of the error amplifier and the input of the integrator, a zero ampere start (7) circuit being connected across the integrator capacitor. 2. A linear bipolar as claimed in claim 1 wherein said zero ampere comprises a resistance and a relay connected in series. 3. A linear bipolar as claimed in claim 1, wherein said output filter comprises a capacitor adapted to be connected across the output of said power supply. 4. A linear bipolar current regulated DC power supply for inductive loads substantially as herein described and illustrated. |
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459-del-1999-correspondence-others.pdf
459-del-1999-correspondence-po.pdf
459-del-1999-description (complete).pdf
Patent Number | 245062 | |||||||||
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Indian Patent Application Number | 459/DEL/1999 | |||||||||
PG Journal Number | 01/2011 | |||||||||
Publication Date | 07-Jan-2011 | |||||||||
Grant Date | 30-Dec-2010 | |||||||||
Date of Filing | 23-Mar-1999 | |||||||||
Name of Patentee | NUCLEAR SCIENCE CENTRE | |||||||||
Applicant Address | ARUNA ASAF ALI MARG, NEW DELHI-110067, INDIA. | |||||||||
Inventors:
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PCT International Classification Number | H02M 7/00 | |||||||||
PCT International Application Number | N/A | |||||||||
PCT International Filing date | ||||||||||
PCT Conventions:
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