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
  • H02M1/32—Means for protecting converters other than automatic disconnection
• • 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
  • H02M3/158—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 including plural semiconductor devices as final control devices for a single load

Definitions

• FIG. 1 represents a first example of a conventional diagram of step-up converter of the type to which s
• This converter essentially consists of an inductance L in series with a rectifying diode D between two terminals E and S respectively defining positive input terminals of a direct supply voltage Vdc and of positive output of a continuous voltage Vout and of a higher level than the voltage Vdc.
• the voltages Vdc and Vout are, " in this example, referenced to a common ground M.
• a switch K (generally a transistor N channel power MOS) connects midpoint 1, between inductance L and diode D, to ground M.
• This switch K is controlled by a train of pulses supplied by an electronic control circuit 2 (CTRL) .
• CTRL electronice control circuit 2
• an energy storage capacitor C connects the terminals S and M in order to provide a stable voltage to a load 3 (Q) connected between the terminals S and M.
• the capacitor C is sometimes omitted, either because a capacitor is included in load 3, either because it does not need a stable power supply.
• the control pulse train of switch K can be a pulse train of fixed frequency and width modulated (PWM), a pulse train of fixed but frequency modulated duty cycle (PFM), or any other adjustable pulse train.
• circuit 2 receives information REG relating to the output voltage Vout to enable the closing periods of the switch K to be controlled in order to maintain the desired voltage Vout.
• a recurring problem of a step-up converter of the type represented in FIG. 1 is that in the event of a short circuit in the load 3, the current accumulated in the inductance is no longer controllable, which leads to a deterioration of that -this.
• FIG. 1 A first known solution to overcome this phenomenon is shown in FIG. 1 and consists in providing a load shedding circuit consisting of a resistor in series with a switch Kd for short-circuiting the inductance at start-up and in the event of detection of short -circuit in the load.
• a load shedding circuit can also directly short-circuit the association in series of the diode and the inductance.
• FIG. 2 represents a second conventional example of control of a step-up converter making it possible to protect the inductance at the start of the circuit.
• the switch K has been represented in the form of an N-channel OS transistor and the load Q has not been represented.
• a P channel MOS transistor 4 is interposed between the cathode of the diode D and the terminal S (positive electrode of the capacitor C and / or of the load).
• the gate of transistor 4 is connected by a switch SI either directly to the source 6 of transistor 4, or to a potential lower than this source, imposed by a Zener diode DZ.
• the anode of the diode is polarized by a current source 5 connected, for example to ground.
• Side switch K its grid is connected to point 1 by a Zener diode DZ2 in series with a switch S2 and to ground M by a Zener diode DZ3.
• the role of the Zener DZ3 diode is to protect the switch K by limiting its gate voltage.
• the role of the diode DZ2 is to impose a voltage difference between the point 1 and the gate of the transistor K when the switch S2 is closed.
• a switch S3 in series with a diode D3 is interposed between the output of the circuit 2 'supplying the pulse train and the gate of the transistor K.
• the switch S3 is closed, the switch S2 is open and the switch SI is in the position where it connects the gate of transistor 4 to the fixed potential by the diode DZ, which makes this transistor on.
• the control of the switch K by means of a pulse train therefore takes place normally, causing successive charging and discharging phases of the inductance L in the capacitor C. In the event of a short circuit in the load (between terminals S and M), this must be detected by additional means (for example by monitoring by means of the signal REG entering the control circuit 2 'that the voltage Vout is canceled).
• the circuit 2 ′ controls the opening of the switch S3 and the closing of the switch S2 so as to activate the active clipping stage of the gate voltage of the NMOS transistor K constituted by the diode DZ2.
• a resistor R3 is provided connecting the gate of transistor K to ground so as to allow discharge.
• a drawback of the protection circuit of Figure 2 is that it requires a particular sequence of switch control. In particular, the opening of transistor 4 ne 'must take place once the transistor K has been blocked by the opening of the switch S3 and the floor clipping has been put into operation by closing 1 switch S2.
• Another drawback of the circuit of FIG. 2 is that the amount of energy stored in the inductor L is not controlled.
• Another drawback is that such a circuit is relatively bulky by the number of auxiliary switches that it requires.
• restarting the circuit generally requires a time delay from the detection of a problem.
• the diode D is replaced by a transistor controlled by the circuit 2 (figure 1) or 2 '(figure 2) in order to make synchronous rectification and thus avoid the voltage drop of the diode D.
• Summary of the The present invention aims to overcome all or part of the drawbacks of conventional converters.
• the present invention aims to provide a short-circuit management circuit in a load supplied by a step-up converter, which overcomes the drawbacks of known solutions.
• the invention aims in particular to reduce the number of switching elements necessary to minimize the surface area of silicon in an integrated embodiment.
• the invention also aims to allow a simplification of the sequencing of the control of the protection switches used.
• the invention also relates, in a preferred aspect, to simplify the detection of short circuit and more particu larly ⁇ to provide a protective element that can be independent of the main switch control circuit of the converter.
• the invention also aims to automatically manage the energy stored in the inductive element as well as the precharging phase, thus limiting the current peaks.
• the invention also aims to automatically control the restart following a problem.
• the present invention provides a protection circuit for a step-up converter comprising a first switch with reverse input logic between a rectifying element in series with an inductor and an output terminal of the converter, comprising means for connecting the control electrode of the first switch to a first potential linked to the power supply potential of the inductor as long as the output voltage is below a threshold.
• said means connect said control electrode to a potential lower than the potential of the switch, inductance side, as soon as said threshold is reached.
• the circuit includes a circuit for selecting the highest potential between the supply voltage of the inductor and the voltage of the first switch on the inductance side.
• the first switch is a P-channel MOS transistor or a PNP type bipolar transistor.
• the control electrode of the first switch is connected to its power electrode on the inductance side, by a voltage source through a second switch.
• the control electrode of the first switch is connected to ground via a second switch.
• the rectifying element is a synchronous rectifying switch.
• the present invention also provides a method of protecting a step-up converter comprising a first switch with reverse input logic between a rectifying element in series with an inductor and an output terminal of the converter, consisting in biasing the electrode.
• the control electrode of the first switch receives a potential, lower than the potential of its power electrode on the inductance side, as soon as said threshold is reached.
• the threshold corresponds to the supply voltage of the inductor.
• the present invention also provides a voltage step-up converter provided with a protection circuit.
• FIG. 3 schematically represents a first embodiment of a control and protection circuit of a step-up converter according to the invention
• FIG. 4 represents a second embodiment of the invention applied to an autonomous protection circuit
• Figure 5 illustrates the operation of the protection circuit of Figure 4
• Figure 6 shows a practical embodiment of the protection circuit of Figure 4
• FIG. 7 schematically represents a third embodiment of a control and protection circuit of a step-up converter with synchronous rectification according to the invention.
• a feature of an embodiment of the present invention is to create an overvoltage on the output switch of the converter which is automatically canceled. More specifically, the invention provides for using a switch with reverse input logic (PP transistor or PMOS transistor) at the output of the converter and for controlling this switch independently of the main switch of the step-up converter.
• PP transistor or PMOS transistor reverse input logic
• this converter represents a first embodiment of a step-up converter according to the invention.
• this converter comprises an inductance L in series with a rectifying element (for example a diode D) and a protection switch 4 between an input terminal E of application of a DC voltage Vdc and an output terminal S for supplying a higher output voltage Vout.
• a load 3 (Q) is connected, if necessary in parallel with a capacitor C (not shown), between the terminal S and a ground terminal M, common or not with the ground of the input voltage.
• a circuit 10 controls by pulse train a switching switch K connecting the anode 1 of the diode D to the ground M.
• the transistor 4 (here a MOS transistor with channel P) is connectable, via a switch SU, either to a potential lower than its source 6, or to a potential corresponding to the input supply potential Vdc.
• the SU switch connects the source 6 of the transistor 4 via a Zener diode DZ setting a voltage threshold between gate and source of the transistor 4 when the SU switch is connected to it (terminal NOT) .
• the anode of the diode DZ (terminal N) is polarized, for example, by a current source 5. Any other voltage source imposing, between gate and source of the transistor 4, a voltage lower than its threshold voltage in order to make it passable is suitable.
• the terminal N of the switch SU can correspond to the ground M rather than being connected to the source 6 of the transistor 4 by a diode DZ, if the transistor 4 supports a voltage Vgs close to the voltage Vout.
• the other terminal CC of the switch SU intended to connect the gate to the positive potential of the voltage Vdc, is connected, for example to the terminal E via a switch S12.
• the role of the switch S12 is to force the blocking of the transistor 4 when the circuit must be turned off.
• the point of polarization of the gate of transistor 4 is always less than the output voltage in normal operation, but becomes greater than this output voltage at least in the event of a short circuit. At the start of the circuit, i.e. when the voltage
• Vout is zero, switch S12 is closed and switch SU is in the CC position.
• the transistor 4 is then on and the circuit 10 controls the switch K in a conventional manner.
• the circuit 10 switches the switch SU towards the terminal N. This has the effect of keeping the transistor 4 in the on state but now being biased by the voltage difference between its gate and its source, fixed by the Zener diode DZ.
• the switch S12 is indifferently left closed or open.
• Another advantage of the invention is that it avoids a Zener diode device for active clipping.
• Another advantage of the invention is that it facilitates the starting of the converter by introducing automatic protection thanks to the connection to the input voltage (for example, the voltage of a battery).
• the fact that the transistor 4 leads to start-up avoids differentiating the start-up phase from a short circuit.
• This advantage is important insofar as, as long as the voltage Vout has not started to increase, a conventional control circuit must distinguish this starting from a short-circuit. In particular, the use of a timer is thus avoided as would be the case in a conventional device (FIG. 2).
• FIG. 4 represents a second preferred embodiment of a converter according to the invention.
• the detection of short-circuit (or insufficient voltage Vout) is performed by a circuit 20 autonomous with respect to the control circuit 21 supplying the pulse train to the gate of the switch K.
• the circuit 20 has two inputs A and B receiving respectively the source voltage 6 of the transistor 4 reduced by a voltage DZ and the supply voltage Vdc taken at point E of the assembly.
• a MAX output (A, B) of circuit 20 is connected to the gate of transistor 4.
• circuit 20 The function of circuit 20 is to provide the highest voltage of those present on its inputs A and B.
• circuit 20 measures the voltage of the source 6 of the transistor 4 and supplies the voltage present on its input A as soon as the voltage of the source 6 becomes greater than the voltage Vdc.
• An advantage of this embodiment is that it allows automatic detection of the short circuit by the circuit 20.
• the control circuit 21 is then a conventional circuit which is satisfied with the pulse train control and the servo-control of this train of pulses with respect to the measurement of the output voltage (for example, a circuit such as circuit 2 in FIG. 1, without the control of the switch Kd).
• FIG. 5 illustrates the operation of the circuit 20 of FIG. 4. It will however be noted that the same function can be performed by the circuit 10 of FIG.
• FIG. 5 shows an example of the shape of several characteristic voltages of the circuit 20 as a function of time when the circuit is started.
• the voltage Vout is shown in solid lines.
• the voltage V6 of the source 6 of the transistor 4 is shown in dotted lines.
• the gate control voltage Vg of transistor 4 is shown in dashed lines. For simplicity, we have neglected any voltage drops in the switches SU and S12 when they are on.
• the circuit is switched off, no voltage is applied to terminal E.
• the converter is energized.
• the gate voltage of transistor 4 is then brought to the potential of terminal E (Vdc).
• the voltage V6 of its source corresponds to the voltage Vdc (applied to the gate of the transistor) increased by a periodic overvoltage linked to the switching in the inductance.
• the transistor 4 is then on and the energy transfer takes place towards the voltage Vout when the switch K is open at the rate of the train of control pulses.
• the circuit 20 switches its output and now applies, to the gate of the transistor 4, the voltage V6 reduced by the value Vdz of the Zener diode and the overvoltage disappears.
• the voltage Vout continues to increase until the level desired by the circuit 21 is reached (not shown in FIG. 5). The same operation occurs in the event of a decrease in the voltage Vout.
• FIG. 6 represents a practical embodiment of the circuit 20 of FIG. 4.
• the terminals A and B are respectively connected to the output terminal MAX (A, B) by two diodes DB and DA by their respective cathodes.
• An advantage of the invention is that it manages all the current overloads (Vout less than Vdc) whatever its origin, whether it is an overload, a short circuit, or inrush current calls.
• FIG. 7 represents a third embodiment of a control and protection circuit of a step-up converter applied to a synchronous rectification. Compared to the embodiment shown in FIG.
• the diode D is replaced by a controlled transistor M by a circuit 21 '(CTRL) so as to operate a synchronous rectification and thus minimize the voltage drop between the terminals 1 and 6.
• CTRL circuit 21 '(CTRL)
• FIG. 7 the parasitic diodes D' and D4 of the transistors M 'and 4 have been shown, the transistors M 'and 4 being connected so that their respective parasitic diodes are in anti-series.
• the gate of transistor M ' can be connected either directly to terminal 6, or to this same terminal 6 via a voltage source 31. These connections are obtained by means of two switches 32 and 33 respectively connecting the gate of transistor M 'at terminal 6 and this gate at a first terminal of the voltage source 31, the other terminal of which is connected to terminal 6.
• the switches 32 and 33 are controlled inversely, an inverter 34 of a signal control unit supplied, for example, by an AND logic gate 35 being interposed between the control terminal of switch 33 and that of switch 32.
• Logic gate 35 combines the inverse (inverter 36) of the control signal of the MOS switching transistor K with a signal, supplied by the circuit 21, indicating that the output voltage Vout is greater than a threshold.
• the operation of the circuit of FIG. 7 is as follows.
• the transistor M ' is turned on when the switch K is open (that is to say that the inductive element L discharges towards the output 6 and that the corresponding current is higher than a threshold TH).
• the transistor M ' is blocked when the switch K is on or when the current (flowing in ' the supplied load) is lower than the threshold TH.
• This threshold TH is chosen at a low value (ideally zero) so as to open the switch M 'when the inductor has no more current to discharge in the load.
• the switch 32 is closed and the switch 33 is open.
• the switch 33 is closed and the switch 34 is open so as to impose a voltage sufficient grid / source thanks to the voltage source 31 (for example a Zener diode of a few volts).
• the above operation amounts to the fact that, when the output voltage Vout is less than a threshold, the transistor M 'operates as a diode.

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Dc-Dc Converters (AREA)
• Protection Of Static Devices (AREA)
• Ac-Ac Conversion (AREA)

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• 2003
  • 2003-12-30 FR FR0351231A patent/FR2864720B1/fr not_active Expired - Fee Related
• 2004
  • 2004-12-30 WO PCT/FR2004/050762 patent/WO2005074109A1/fr active Application Filing
  • 2004-12-30 EP EP04816609A patent/EP1704634A1/de not_active Withdrawn
  • 2004-12-30 JP JP2006546294A patent/JP2007517490A/ja not_active Withdrawn
• 2006
  • 2006-06-30 US US11/480,754 patent/US7835119B2/en active Active

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