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
  • H03K17/081—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 present invention relates to circuits reducing the switching losses of power switches.
• the break in the current is most often softened by a capacitor in series with a diode, the whole set in parallel with the terminals of the switch so as to divert the current at the opening of the switch.
• the capacitor is re ⁇ charged at the supply voltage and the diode prevents it from being suddenly discharged during the next closing of the switch. This discharge is carried out slowly by a resistor placed in parallel on the capacitor or by a more sophisticated circuit recovering its energy.
• the interim diode This function must be performed in the interim by another diode, which will be called the "interim" diode, in series with a voltage generator e.
• the generator e is conventionally produced with a voltage clipping device, for example a reverse Zener diode, or by a transformer whose secondary is rectified on a continuous voltage, so that the energy is recovered.
• a voltage clipping device for example a reverse Zener diode
• transformer whose secondary is rectified on a continuous voltage
• the invention aims to allow rapid saturation of the protective inductance without requiring an exaggerated voltage, while ensuring a favorable energetic balance with a slightly complex assembly.
• FIG. 1 shows a conventional switching circuit regulating an incoming current, presenting the desired improvements in a module 10 framed in dotted lines.
• FIG. 3 shows that a circuit identical to that of Figure 1, but regulating an outgoing current, réali ⁇ sand perfectly symmetrical.
• the power switch 1 is put in parallel with the diode 3 and the capacitor 4 which de- bank the output current during the opening of the switch.
• the power diode 2 is in series with an inductance 5, preferably saturable, limiting the overcurrent caused on closing of the switch 1 by the diode 2 in reverse recovery phase.
• the interim diode 6 and the voltage generator 7 limit the overvoltage at the terminals of the power switch 1 and allow the output current to find a path until the inductor 5 is saturated.
• the diode 8 makes it possible to avoid the undesirable voltage oscillations generated when the diode 2 suddenly recovers its breaking capacity.
• a possible switch 9 allows the stage to be bidirectional in current, to be associated with a stage of the same type in a structure called in H.
• the module 10 characteristic of the invention is framed in dots: at each opening of the switch 1, the capacitor 12 put in series with the diode 11 short-circuits briefly to ground the side of the inductor 5 connected to the power diode 2, the diode 11 preventing the capacitor 12 from being discharged on the next closure of the switch 1.
• the potential difference across the inductors increased by the over-voltage created by the interim diode 6 and the generator e, allows a rapid growth of its current, which allows the output current to pass entirely through the freewheeling diode 2.
• the capacitor 12 must be of significant value, which fully justifies recover its stored energy. To do this, the energy recovery circuit of the capacitor 4, barely complex. Diode 14 prevents any possibility of discharging the capacitor
• the different operating phases are represented on the timing diagrams of FIG. 2: between T0 and Tl, the power switch 1 opens. Its current II can be interrupted very quickly because the voltage "a" at its terminals evolves slowly thanks to the capacitor 4 charged by the output current and the capacitive feedback is weak. At time T1, this voltage, clipped by the diode 6 at the value V + e, fully applies to the terminals of the inductor 5 and then allows it to saturate fairly quickly, at time T2. The capacitor 12 then charges at an increasing rate to reach very quickly at the point of a voltage equal to V at time T3. The little current which still circulates in diode 6 is soon canceled and the potential of the point has dropped to V.
• the switch 15 can be closed at time T6, slightly before the definitive recovery of the diode 2, as long as the potential at point ba already started to decrease, then it can be cut at time T8, as soon as the potential of the points c and d is below V / 2.
• the total current 113 in the two windings of the inductor 13 rises and then descends in the form of a truncated sinusoid between T6, T8 and T9.
• the energy recovery efficiency of the capacitors 4 and 12 commonly exceeds 95%, even if the switch 15 has a high saturation voltage.
• FIG. 1 regulating an incoming current
• FIG. 3 regulating an outgoing current
• the invention applies to circuits for assisting in the switching of power switches, in particular high frequency semiconductor switches.

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• Electronic Switches (AREA)
• Rectifiers (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=9419966

Family Applications (1)

Country Status (3)

Citations (3)

• 1991
  • 1991-12-12 FR FR9115426A patent/FR2685147A1/fr active Granted
• 1992
  • 1992-12-08 WO PCT/FR1992/001161 patent/WO1993012580A1/fr active Application Filing
  • 1992-12-08 AU AU33562/93A patent/AU3356293A/en not_active Abandoned

Patent Citations (3)

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