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
  • H02M3/00—Conversion of dc power input into dc power output
  • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
  • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
  • H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
  • H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac 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
  • H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac 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
  • H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac 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 with automatic control of output voltage or current, e.g. switching regulators
  • H02M3/1563—Conversion of dc power input into dc power output without intermediate conversion into ac 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 with automatic control of output voltage or current, e.g. switching regulators without using an external clock
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
  • G01R19/12—Measuring rate of change

Definitions

• the present invention relates to switching circuits regulating the current in a load.
• the invention aims to provide a cut-out circuit for controlling the current using the current decay prediction method, the decay sensor being galvanically isolated so as to avoid the use of level translators between different potentials, maintaining good accuracy for an output voltage dynamic greater than 200 and easily adaptable in the case of a bidirectional load current.
• This problem is solved by converting the time gradient of the load current into a galvanically isolated voltage step, then integrating this step into a capacitor with a high dynamic range circuit after selecting the appropriate polarity.
• FIG. 1 represents a circuit carrying out with two distinct chains the measurement of the growth of the current and the prediction of its decrease.
• FIG. 6 shows a variant circuit based on a sampler-blocker simultaneously processing the growth and decline of the current.
• the vast majority of switching regulators operate by means of a power inductor in series with the load, either directly or through a transformer, the current of which oscillates between two extreme values.
• the voltage across this inductor represents the derivative of the load current as a function of time and it is easy to obtain a galvanically isolated image of it, by combining a secondary around at least a fraction of this inductor, serving then an inductive sensor.
• To reconstruct the current from this information one must compensate for the effect of the derivation by a consecutive temporal integration, initialized by the adequate integration constant.
• the invention provides a current control circuit for a switching regulator based on this principle, a first variant using a fixed integration constant, a second proposing an adaptive assembly. The presentation will first be made with very general modular sets, then several specific achievements will be proposed for each module. To facilitate the comparison of modules of the same type, their homologous inputs / outputs are referenced identically.
• the first circuit manages with two distinct chains the increase and the decrease of the load current.
• the signal supplied by load current sensors referenced to a fixed potential is processed by the adaptation interface module 20, ensuring protection, selection, amplification and inversion functions as required. .
• Its VR output is then compared to a peak current setpoint VI by the comparator 42, so as to deactivate the output of a state flip-flop A3 as soon as the authorized peak value is reached (the input polarities of the comparators are not not specified, because dependent on the overall polarity of the assembly).
• the decrease in the load current is predicted by an independent chain made up of the module 10, generator galvanically isolated from a current proportional to the time gradient of the load current, this generator being of switchable po ⁇ larity when the load current is bidirectional, and of the precision integrator module 30 providing a voltage VE proportional to the excursion of the decrease in the load current.
• This voltage is compared to a set point V3 by the comparator 41 so as to reactivate the output of the state flip-flop 43 when the desired excursion has been carried out, which restarts a new cycle.
• the simplified embodiment of the module 10 given in FIG. 1 applies to a unidirectional current of the load.
• This current flows in the inductor 11, fraction or all of the power inductor in series with the load, the voltage at its terminals A and B being taken by the secondary 12 galvanically isolated.
• the resistor 13, in series with the optional resistor 71, makes this module a current generator proportional to the time variations of the load current (the insertion of a resistor 71 in the CE branches or DF makes it possible to detect at its terminals the possibility of an interruption of the load current).
• the polarity of this current generator must be able to be reversed when the direction of the load current is reversed (when it is bidirectional).
• Figures 2 and 3 offer two classic examples of polarity inverters, one using a complete inverter with 4 switches, the other using only two switches but requiring a secondary 12 at midpoint (the switches can of course be realized with integrated analog doors).
• the precision of this stage is due to that of the inductor 11, easily obtained with an air gap, and to that of the resistors 13 and 71 associated with those of the analog gates, preferably paired.
• the capacitive integrator 30 of FIG. 1 is a conventional precision circuit whose voltage follower 33 allows the potential of point F to faithfully follow that of point E.
• the current supplied by generator 10 then becomes completely independent of the instantaneous voltage of the capacitor 31.
• This arrangement is recommended in the case of a unidirectional load current, the integrated follower amplifiers generally having excellent characteristics in offset voltage and in scanning speed.
• the no less conventional assembly of FIG. 5, said capacitive integrator with virtual mass is on the other hand preferable in the case of a bidirectional current of the load, since the constant voltage of points E and F, equal to REF1, allows the use of simplified analog doors.
• the integrator 30 is systematically reset to the voltage REF1 during the phases of growth of the current, by closing the switch 32 preferably produced with a NOS or JFET semiconductor (not having a waste voltage).
• This arrangement provides a current decay excursion proportional to the difference between V3 and REF1. Its precision, limited by the bias current and the offset voltage of the circuit 33 as well as that of the comparator 41, can be excellent thanks to the large dynamic range authorized by V3-REF1.
• the module 20 is essentially an interface for adapting to the type of current sensors used.
• the module 20 needs two inputs, protection circuits 21 and an analog multiplexer 22, as shown in FIG. 1, this case corresponding for example to certain four-quadrant current controllers.
• an H-circuit controlling a bidirectional current it is often possible to have only one current measurement resistance in series with one of the supply poles.
• the task is even simpler with recent power components, with current mirrors, providing an image fraction of their main current. It then suffices, as indicated in FIG. 4, to link the two image current outputs of the two legs of the H together, before attacking the mass amplifier 24 and possibly an inverting amplifier 23.
• the switch 52 is closed, the module 50 then behaving like a gain amplifier fixed by the resistors 55 and 56, its source being module 20.
• the signal VE is thus di ⁇ directly an image of the load current and is compared to the setpoint VI of authorized peak current.
• comparator 62 deactivates the output of flip-flop 63.
• the potential REF2 can be non-zero, so as to introduce an offset voltage.
• the switch 52 is then open and the capacitor 51 discharges at a rate proportional to the gradient of the load current growth, supplied by the module 10. This decrease will be stopped as soon as the signal VE reaches the setpoint V1-V2 , V2 being a voltage proportional to the desired excursion of the decrease in the load current.
• the comparator 61 then reactivates the output of the flip-flop 63 which can of course be provided with priority STOP and GO priority inputs.
• the circuit of FIG. 8 is a variant of follower-blocker well known to those skilled in the art. It has the same advantages as those of FIG. 5, namely a virtual mass which allows the analog switches to work at a fixed potential.
• the comparator 60 of FIG. 6, comparing a signal VE with two high and low thresholds, is called window comparator. This type of comparator can be replaced by the variable threshold comparator described in FIG. 7, advantageous by a very high triggering rapi ⁇ (by a strong positive reaction) and a small number of components.
• Its analog multiplexer can be produced very simply in FIG. 9 with a differential pair 91 and 92 which may or may not subtract from the voltage VI a voltage V2 at the terminals of the resistor 93.
• This second circuit (Fig 6) has the advantage of not claiming any amplifier from module 20, this function can be performed by the follower-blocker. It is obvious to those skilled in the art that the circuits of FIGS. 1 and 6 adapt to the measurement of both positive and negative voltages, the polarities of the inputs of the comparators 40 and 60 being appropriately chosen.
• the invention mainly applies to current control circuits in power cut-off regulators, particularly at high frequency.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Measurement Of Current Or Voltage (AREA)
• Dc-Dc Converters (AREA)
• Amplifiers (AREA)

Applications Claiming Priority (2)

Publications (1)

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Citations (3)

• 1992
  • 1992-01-23 FR FR9200714A patent/FR2686748A1/fr active Granted
• 1993
  • 1993-01-18 AU AU35026/93A patent/AU3502693A/en not_active Abandoned
  • 1993-01-18 WO PCT/FR1993/000043 patent/WO1993015548A1/fr active Application Filing

Patent Citations (3)

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