WO1994013049A1 - Dispositif de circuit a courant limite destine a transferer une surcharge de puissance - Google Patents

Dispositif de circuit a courant limite destine a transferer une surcharge de puissance Download PDF

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Publication number
WO1994013049A1
WO1994013049A1 PCT/FI1993/000509 FI9300509W WO9413049A1 WO 1994013049 A1 WO1994013049 A1 WO 1994013049A1 FI 9300509 W FI9300509 W FI 9300509W WO 9413049 A1 WO9413049 A1 WO 9413049A1
Authority
WO
WIPO (PCT)
Prior art keywords
current
semiconductor switch
arrangement
switch
resistor
Prior art date
Application number
PCT/FI1993/000509
Other languages
English (en)
Inventor
Jarmo Loukusa
Kauko Varanka
Original Assignee
Nokia Telecommunications Oy
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Nokia Telecommunications Oy filed Critical Nokia Telecommunications Oy
Priority to AU55646/94A priority Critical patent/AU5564694A/en
Publication of WO1994013049A1 publication Critical patent/WO1994013049A1/fr

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Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
    • H03K17/08—Modifications for protecting switching circuit against overcurrent or overvoltage
    • H03K17/082—Modifications for protecting switching circuit against overcurrent or overvoltage by feedback from the output to the control circuit
    • H03K17/0826—Modifications for protecting switching circuit against overcurrent or overvoltage by feedback from the output to the control circuit in bipolar transistor switches
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
    • H03K17/08—Modifications for protecting switching circuit against overcurrent or overvoltage
    • H03K17/081—Modifications for protecting switching circuit against overcurrent or overvoltage without feedback from the output circuit to the control circuit
    • H03K17/0814—Modifications for protecting switching circuit against overcurrent or overvoltage without feedback from the output circuit to the control circuit by measures taken in the output circuit
    • H03K17/08146—Modifications for protecting switching circuit against overcurrent or overvoltage without feedback from the output circuit to the control circuit by measures taken in the output circuit in bipolar transistor switches

Definitions

  • the invention relates to an arrangement in a current limited circuit for transferring overload power, the arrangement being used in transferring current e.g. from a source of potential to a signal path, the arrangement comprising a current limited semiconductor switch, which comprises a control electrode and main current path electrodes, through which main current path electrodes current can be transferred to the signal path; current limiting of the semiconductor switch being implemented in the arrangement by a current limiter contained in the arrangement, the limiter being coupled from the control electrode of the semiconductor switch to the signal path, and the arrangement further com ⁇ prising a resistor coupled from the second electrode on the main current path to the signal path.
  • a circuit means e.g. switches.
  • Semiconductor switches can be used e.g. for switching on a current. When switching on a current, the semiconductor switch is only capable of feeding a pre ⁇ determined maximum current, which depends on the size of the switch and current feeder power as well as other factors.
  • the switches should normally be protected against overload and short circuit. They can be used e.g. to couple ground potential to a signal path, such as a dialling line in devices of telecommunication technology.
  • the connection used is single transistor connection, where the current of the transistor coupling ground potential to the line is limited by a zener diode. In overload conditions, power thereby accumulates in the switching transistor itself.
  • the object of the present invention is to pro ⁇ vide a new kind of arrangement in a current limited circuit for transferring overload power, avoiding the problems involved with the known solutions.
  • the solution of the invention enables the use of less expensive components that require less space.
  • the solution of the invention can be applied to all electronic apparatuses where power tolerant direct-current switches that require little space and must tolerate even heavy overload are needed.
  • increase in voltage means that a transistor experiences more stress, whereas in the new solution the transistor experiences less stress since the resistor takes a larger part of the current.
  • the solution of the invention also improves reliability since the switches are not subjected to overload condi ⁇ tions.
  • a hybrid resistor or power resistor is used, and the maximum power that the switch ⁇ ing transistor can take does not exceed 0.5 W.
  • Fig. 1 shows a circuit diagram of the arrange ⁇ ment according to the invention
  • Fig. 2 illustrates the current of the switch as a function of the collector-emitter voltage of the switch.
  • Fig. 1 shows the arrangement according to the invention in a current limited circuit for transferring overload power.
  • the arrangement is used for transferring current e.g. from a source of potential G to a signal path A.
  • the arrangement may be e.g. a switching element in a direct-current signal device, by which element e.g. ground potential G is coupled via resistors e.g. to a dialling line, such as the signal path A in Fig. 1.
  • the arrangement comprises a current limited semiconductor switch Q17, which comprises a control electrode 1 or a base B, and main current path electrodes 2 and 3 or a collector C and an emitter E, current being transferable via said main current path electrodes 2 and 3 to the signal path A.
  • the current limiting of the semiconductor switch Q17 is implemented by a current limiter or advantageous ⁇ ly a zener diode Z4 contained in the arrangement, the limiter being coupled from the control electrode 1 or base B of the semiconductor switch Q17 to the signal path A.
  • the arrangement further comprises a resistor R49 coupled from the second electrode 2 or emitter E on the main current path to the signal path A.
  • a resistor R48 which on account of a voltage drop U(CE) brought about over said resistor R48 by a decrease in the control current I B caused by a current limiter Z4 is arranged to take part of the current of said semiconductor switch Q17 in overload conditions.
  • the decrease in the control current naturally reduces the current in the collector circuit, i.e. the current on the current path called a main current path in normal conditions.
  • the decrease in the control current I B naturally reduces the collector current I c or in normal conditions the current on the main current path.
  • the reduction in the collector current caused by the decrease in the control current thus produces a voltage difference over the transistor or the resistor R48.
  • the arrangement comprises a second semiconductor switch Q16, which comprises a control electrode 4 or a base B and main current path electrodes 5 and 6 or a collector C and an emitter E.
  • Said second semiconductor switch Q16 is current unlimited, and it is connected in series with the first current limited semiconductor switch Q17, and it is further characterised in that the current unlimitedness of the second semiconductor switch Q16 is implemented by switching said semiconductor switch to a saturation state. This enables e.g. coupling of ground potential 7 by a current unlimited switch Q16, a current limited switch Q17 provided with a resistor R48 being connected above it in series as shown in Fig. 1.
  • the switches Q16 and Q17 or advantageously transistors are connected in series such that the main current path of the current unlimited switch Q16 is connected with the main current path of the current limited switch Q17 and they are advantageously separated by a power resistor R47.
  • the emitter E of the current unlimited switching transistor Q16 is thus coupled via a low ohmage resistor R47 to the collector C of the first switching transistor Q17.
  • the arrangement comprises a third semi ⁇ conductor switch Q15, which comprises a control electrode or a base B and main current path electrodes 10 and 11 or a collector C and an emitter E, the switch Q15 being coupled at the collector C or electrode 10 to control the switching operation of the current unlimited second semiconductor switch Q16.
  • the third semiconductor switch is connected at the base or electrode 9 to a control line 12, by which the base can be activated for a switching operation. For example, ground potential can be taken from the control line 12 to the base or electrode 9.
  • the control line 12 can be used for coupling positive current from a source of potential 13 to the main current path or collector or electrode 10 of the third switch Q15, the potential of the source being +5 V (5 volts positive).
  • This is an advantageous way of switching the current unlimited switch Q16 to a saturation or short circuit state in overload condi ⁇ tions.
  • the current I ⁇ o ⁇ flowing from the ground potential G via the current unlimited switch Q16 and the resistors R47, R48 and R49 to the signal path A is high.
  • the resistance on this current path is very low, i.e. the sum of the resistances R47, R48 and R49, which makes 839 ohm based on the values indicated in Fig. 1.
  • the resistance (550 ohm) of the shunt resistor of the current limited switch Q17 provides for the major part of the resistance on said current path. The power thereby remains at the shunt resistor R48.
  • the current unlimited semiconductor switch Q16, and also Q17 is an npn transistor, and the third semiconductor switch Q15 controlling the switch Q16 is of the opposite type, i.e. a pnp transistor. A change in the voltage set between B and A reverses the situ ⁇ ation.
  • the base of the switch Q15 receives ground potential from the control line 12, the ground potential establishing control current at the base. This produces a main current path from the potential 13 via the resistor R43 to the collector 10 of the switch Q15 or transistor, and it passes the control current to the base of the switch Q16.
  • Q16 undergoes saturation or short circuit. In short circuit or saturation conditions, hardly any power remains in the transistor Q16.
  • Current is then set up from ground potential G to flow via the collector 5 and the emitter 6 and via the resistor R47 through the current limited switch Q17 to the resistor R49 and further to the point to be controlled, i.e. the signal path A.
  • the current flowing on the path brings about a voltage drop in the resistors R49 and R47.
  • the voltage in the resistor R47 maintains the current limiting circuit in a conductive state.
  • a second voltage drop in the resistor R49 causes current limiting such that when the voltage drop grows sufficiently great (threshold voltage of the zener diode e.g. 4.7 V), i.e. when the current in the resistor R49 is sufficiently high, the zener diode Z4, which is coupled between the resistor R49 and the base of the switching transistor Q17, begins to limit the voltage and current I B flowing to the base.
  • the current I c of the transistor Q17 is thereby limited to a predetermined maximum.
  • the voltage drop U(CE) over the transistor Q17 establishes current in the resistor R48.
  • the resistor R49 also measures the current of the resistor R48; the total current I ⁇ o ⁇ remains the same as shown by the direct por- tion in Fig. 2, but the power remains in the resistor R48.
  • the essential point is that in overload conditions the resistor R48 of the current limited switch (circuit) takes the power to itself.
  • the resistor R49 limits current, i.e. determines the maximum current that can pass through the transistor Q17.
  • the zener diode Z4 limits the control current coming to the base and thereby makes the current flow via the resistor R48.
  • the upper switch or switch Q17 is a current limited circuit by operation, operating such that the current flowing to the signal path A grows to be sufficiently high, i.e. so high that the voltage of the emitter resistor R49 reaches a voltage that is equal to the threshold voltage of the zener diode minus the base-emitter voltage of the transistor Q17; at this stage the potential in this point is so high that the zener diode Z4 can draw base voltage downward, whereby limiting of the current of the transistor begins.
  • the base current is limited by the zener diode.
  • the zener diode prevents base control, whereby the current flowing through the transistor Q17 is limited thereto.
  • the current of the transistor Q17 thereby starts to transfer to the power resistor R48, as shows in Fig. 2.
  • the solution according to the invention operates as a current limiter in which the transistor Q17 is not loaded.
  • the collector of the current limited switch Q17 is then coupled directly to ground potential G and not to the switch Q16 as in Fig. 1.
  • the arrangement according to the invention as shown in Fig. 1 is based on the idea that the current of the switch Q16 is not limited in any way but the switch is an unlimited switch, i.e. at a saturation state, and is connected in series with a current limited switch Q17.
  • voltage dividing resistors R45 and R46 are arranged between the base 4 of the current unlimited switch Q16 and the base 1 of the current limited switch Q17.

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  • Electronic Switches (AREA)

Abstract

L'invention concerne un dispositif appliqué à un circuit courant limité pour transférer une surcharge de puissance. Ce dispositif comprend un commutateur à semi-conducteur à courant limité (Q17), et la limitation de courant du commutateur à semi-conducteur (Q17) est mise en oeuvre par un limiteur de courant (Z4) intégré au dispositif, lequel comprend en outre une résistance (R49), couplée depuis la deuxième électrode du trajet de courant principal vers le trajet de signal (A), et une résistance (R48) couplée entre les électrodes placées sur le trajet de courant principal du commutateur à semi-conducteur à courant limité. Cette résistance - dufait d'une baisse de tension qu'elle subit de par la baisse du courant de commande due au limiteur de courant (Z4) - est conçue pour absorber une partie du courant dudit commutateur à semi-conducteurs (Q17) dans des conditions de surcharge.
PCT/FI1993/000509 1992-11-30 1993-11-30 Dispositif de circuit a courant limite destine a transferer une surcharge de puissance WO1994013049A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU55646/94A AU5564694A (en) 1992-11-30 1993-11-30 Arrangement in a current limited circuit for transferring overload power

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI925452 1992-11-30
FI925452A FI925452A (fi) 1992-11-30 1992-11-30 Arrangemang foer oeverfoering av effekt fraon en stroembegraensad krets vid oeverbelastning

Publications (1)

Publication Number Publication Date
WO1994013049A1 true WO1994013049A1 (fr) 1994-06-09

Family

ID=8536300

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/FI1993/000509 WO1994013049A1 (fr) 1992-11-30 1993-11-30 Dispositif de circuit a courant limite destine a transferer une surcharge de puissance

Country Status (3)

Country Link
AU (1) AU5564694A (fr)
FI (1) FI925452A (fr)
WO (1) WO1994013049A1 (fr)

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0048758A1 (fr) * 1979-12-28 1982-04-07 International Rectifier Corporation Japan, Ltd. Configuration de circuit de transistor a effet de champ
DE3330045A1 (de) * 1983-08-19 1985-03-07 Siemens AG, 1000 Berlin und 8000 München Schaltungsanordnung zur speisung von elektrischen gleichstromverbraucheranordnungen
DE3535864A1 (de) * 1985-10-08 1987-04-16 Ant Nachrichtentech Strombegrenzungsschaltung
EP0470850A2 (fr) * 1990-08-10 1992-02-12 Xerox Corporation Circuit servant à commuter un transistor haute tension à film mince

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0048758A1 (fr) * 1979-12-28 1982-04-07 International Rectifier Corporation Japan, Ltd. Configuration de circuit de transistor a effet de champ
DE3330045A1 (de) * 1983-08-19 1985-03-07 Siemens AG, 1000 Berlin und 8000 München Schaltungsanordnung zur speisung von elektrischen gleichstromverbraucheranordnungen
DE3535864A1 (de) * 1985-10-08 1987-04-16 Ant Nachrichtentech Strombegrenzungsschaltung
EP0470850A2 (fr) * 1990-08-10 1992-02-12 Xerox Corporation Circuit servant à commuter un transistor haute tension à film mince

Also Published As

Publication number Publication date
FI925452A0 (fi) 1992-11-30
FI925452A (fi) 1994-05-31
AU5564694A (en) 1994-06-22

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