RU2497274C1 - Shaper of energy pulses using metal oxide voltage-variable resistors - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: shaper includes pulse electric energy accumulators: inductance and/or a charged capacitor, at least one fully controlled quick-acting key with a parallel protective chain that restricts voltage at activation of a quick-acting key, in series with the quick-acting key(s) there installed is at least one locking key that is able to lock or pass load current, a controller connected to control chains of keys through the corresponding control devices. The protective chain of the quick-acting key(s) includes at least one metal oxide voltage-variable resistor (VVR), thus forming a pulse limiter of load current flowing either through the quick-acting key, or through VVR. In the load current chain there installed is a sensor of an electric mode and connected to a control controlling the load current on low or high frequency.

EFFECT: development of an energy shaper for the purpose of providing a powerful current pulse capable of reducing switching bursts and resonant current oscillations in load, improving operating reliability of keys and other devices physically connected to that energy shaper, and the specified limitation of load current pulse.

2 cl, 7 dwg

Description

FIELD OF THE INVENTION

The invention relates to the formation of pulses of electrical energy. First of all, it is intended for use in high-voltage pulse power conditioners of external defibrillators. In addition, it can be used in devices that use the inclusion, shutdown or limitation of electrical energy, for example, adaptable to the current electric mode artificial current switching circuits and high-voltage modulators.

State of the art

To protect the keys from overload, protective circuits are used, which consist of active and / or reactive elements. The introduction of constant active resistance into the key circuit causes additional energy losses. The introduction of reactive protection circuits causes transient overvoltages that distort the parameters of the energy pulse.

To reduce switching losses and increase reliability, high-voltage switches switch at high speed, but fast switching creates unwanted electromagnetic radiation and causes electromagnetic compatibility problems for analog and digital devices that surround us everywhere.

The desired solution for key protection and pulse energy generation during switching is the introduction of adjustable active resistance into the switching circuit when the keys are turned off. It is also preferable to provide switching keys in the absence of electric current or at its minimum level.

A device for limiting the current pulse by introducing into the circuit a resistance consisting of discrete resistors. The resistance of the current limiter is controlled by a current sensor by controlling transistor switches shunting discrete resistors. The device reduces the dependence of the discharge current on the load resistance. The disadvantage is an increase in the number of discrete resistors with keys and independent control loops for individual switching of keys, while increasing the accuracy of the current setting, which increases the dimensions and reduces the reliability of the device.

US Patent No. 6096063, 08/01/2000, ELECTROTHERAPY CIRCUIT HAVING CONTROLLED CURRENT DISCHARGE BASED ON PATIENT-DEPENDENT ELECTRICAL PARAMETER.

RF patent 2421899, March 9, 2009, DEVICE FOR FORMING A BIPOLAR SIGNAL.

The closest in technical essence and the achieved positive effect and adopted for the prototype is the device described in RF patent No. 2398347, 08/06/2009, ENERGY PULSE FORMER WITH REGULATED FORM.

The switches regulating the pulse current are used in conjunction with protective circuits based on voltage limiters. The protective circuit is used in a special mode: as a voltage limiter for control switches and as a circuit limiting the load current. The disadvantage is the limited use of the protective circuit.

It is known that metal oxide varistors, commonly known as MOB (MOV), which will be used in the following discussion, are widely used as protective devices. MOBs based on metal oxides (for example, zinc oxide) have a high response rate and the ability to absorb tremendous energy. When a surge occurs above the classification voltage, the space around the zinc oxide granules becomes electrically conductive with increasing discharge current through the MOB for nanoseconds. MOBs with an absorbed energy of more than 100 MJ are currently being produced. The absorption of such energy becomes possible due to the efficient field emission of electrons. In this case, high-energy pulses of thermal energy are scattered throughout the entire MOB. MOB cannot work in the high conductivity mode for a long time, since it overheats (Tregubov S.V., Panteleev V.A., Frese O.G. “General principles for choosing varistors for protection against impulse voltages”, http: // www.komi.com).

It is known the use of varistors for the formation of voltage of complex shape. (See the article "The use of varistors", the journal "Radio" No. 7, 1971). Examples of using varistors for generating signals in low-voltage television technology, including at high frequencies, are given. The disadvantage is the low efficiency of the proposed solutions in powerful pulse circuits.

Disclosure of invention

The invention is directed to the development of an electric energy generator that is capable of providing a high pulse power (high voltage and / or current) capable of reducing switching voltage spikes and resonant oscillations in a load, increasing the reliability of keys and devices physically connected to this electric energy generator, and limiting pulse current in the load.

The invention was created during the development of an electric energy pulse shaper for a defibrillator that generates a bipolar voltage with a amplitude of more than 2000 V and a current of up to 100 A. At the same time, the task of increasing the reliability of all power switches of a pulse shaper under adverse electrical conditions was solved.

In accordance with the present invention, pulsed electric energy storage devices are installed in the driver circuit: inductance and / or charged capacitor, as well as one or more loads. At least one fully controllable high-speed key is connected to a parallel protective circuit that limits the voltage when the high-speed key is turned off. In series with the high-speed key (s), at least one blocking key is included, which can block or pass the circuit current. Locking keys may be semiconductor and / or mechanical. The driver includes a controller connected to the key control circuits. Key switch-on intervals are synchronous or are set individually, both under permissible load and power source states and when deviating from valid states that are independent of the driver.

The protective circuit includes at least a metal oxide varistor (MOB) connected with a minimum inductance of the connections to the high-speed switch. The mentioned elements form a pulse current limiter. MOBs define certain parameters that, after high-speed shutdown of a high-speed key, provide a longer conservation of the load current compared to the time of turning off a high-speed key. At the same time, the voltage on the MOB should not exceed the maximum allowable voltage of the high-speed key, including at the maximum possible load current. The maximum allowable absorbed energy MOB or the total maximum allowable absorbed energy of the series-connected MOBs should be at least 10% of the energy of the pulse energy storage connected to the shaper. The driver adjusts the load current using the MOB resistance for the time intervals defined by the controller, switching the current between the high-speed switch and the MOB resistance at low or high frequency.

The shaper is configured in such a way that it enables fast-acting and blocking keys to be switched on in the absence of electric current or at its minimum level, and blocking keys to be turned off in the absence of electric current or at its minimum level.

In series with the pulse current limiter, blocking keys are introduced, forming a circuit for switching the polarity of the current in the load on semiconductor switches or electromagnetic relays.

When adjusting the parameters of the current pulse, the controller provides high-frequency switching of the current in the MOB, for example, at a frequency of more than 50 kHz with a redistribution of pulsed energy between the MOB and the load at a level of more than 10%.

The shaper is configured to work with one or more sources of electrical energy for one or more loads.

The maximum allowable absorbed energy MOB is selected taking into account the parameters of energy storage and / or devices are introduced into the shaper that limit the absorbed energy MOB to an acceptable level.

Description of drawings

The figure 1 shows a simplified diagram of the construction of a pulse shaper of energy using a high-speed fully managed key and MOB.

Figure 2 shows a graph of the current through a quick-acting key and through MOB as a function of time (a) and a graph of current through a load as a function of time (b).

Figure 3 shows graphs of the current through the load as a function of time, showing the process of adjusting the current parameters using the MOB.

The figure 4 shows a diagram for the formation of bipolar electrical pulses.

The figure 5 shows a graph of the transition of the load current from the positive phase to the negative phase as a function of time.

The figure 6 shows a "energy efficient" circuit for the formation of bipolar electrical pulses.

7 is a graph of a bipolar electric pulse across a load as a function of time. The implementation of the invention

The figure 1 shows a pulse generator of energy using a high-speed fully controlled key and MOB, as well as a pulsed energy source - inductance.

A pulsed source of electrical energy 1 (for example, a charged capacitor) is connected through the inductance of circuit 2, the high-speed key 3, MOB 4, as well as the blocking key 5 to the load 6. MOB 4 is connected to the terminals of the key 3. The controller 7 is connected to the control circuits of the keys 3 and 5. An electric mode sensor 8 is connected to the circuit, which is connected to the controller 7. In the load circuit 6, the inductance of circuit 2 and the blocking switch 5, current i ₀ flows.

Inductance 2 is specially introduced into the circuit or it can be formed by the load inductance. The inductance of the conductors in the current circuit i _{0 is} considered as the load inductance.

As a key 3, it is possible to use semiconductor devices, for example, insulated-gate bipolar transistors, known as IGBTs. As the locking key 5, you can use any known semiconductor keys or mechanical keys.

MOB 4 has the ability to instantly absorb electrical energy and dissipate thermal energy. The level of absorbed energy is limited by the maximum allowable absorbed energy.

The connections between the key 3 and MOB 4 should have a minimum inductance, which ensures that the current through the MOB 4 is turned on in response to a decrease in the current through the key 3 during nanosecond time intervals.

The remaining voltage on the MOB 3, for example, when using IGBT, should not exceed the maximum allowable voltage of IGBT and its reverse diode, at any possible current through IGBT. For example, if the maximum current through the IGBT can rise to 200 A, and the maximum voltage applied to the IGBT should not exceed 1200 V, then the MOB must provide a residual voltage of up to 1200 V at a current of 200 A.

Let us pay attention to the processes occurring in the circuit shown in figure 1. At the initial moment of switching on the keys 3 and 5, there is no current in the circuit and then a current i _{0 is formed} equal to the current i ₀₁ through keys 3 and 5, increasing at a certain speed. The slew rate of the current (di ₀ / dt) is limited by inductance 2, which stores energy. When the current i ₀ reaches the specified level and / or after a certain time, the controller 7 turns off the key 3. The current of the key 3 is interrupted, and the current i ₀₂ through MOB 4 reaches its maximum value due to the fact that the inductance 2 transfers the stored energy to the circuit. In this case, such a voltage is generated on MOB 4 at which i ₀₁ = i ₀₂ . (Such a process is possible with a rapid decrease in current through switch 3). Further, the circuit current i ₀ monotonically attenuates to zero or to the level of static current through MOB 4. By switching the key 3, it is possible to adjust the circuit current i ₀ for a time that is limited by the maximum allowable absorbed energy MOB 4.

The ratio of the accumulated energy in the inductance 2, the turn-off time of the switch 3 and the load 6 should be such that this energy is enough to form a current pulse through MOB 4 and load 6. For example, with a current decay rate of more than 5 times the speed current decay through key 3.

The figure 2 shows a graph of the current through a high-speed key and through MOB as a function of time (a) and a graph of the current through the load as a function of time (b). From the graphs it follows that after the key 3 is turned off, the discharge current i ₀₂ begins to monotonically decay at a current decay rate exceeding the current decay rate through key 3. By selecting the switching moments of key 5, it can be turned off at minimum current or in the absence of current.

The switching system of the keys of the pulse shaper, according to figure 1, under the control of the controller 7, must ensure that the keys 3 and 5 are turned on in the absence of electric current or at its minimum level, as well as the blocking key 5 is turned off in the absence of electric current or at its minimum level. Under the minimum current should be understood as a current at least 20 times less than the maximum current.

If, without waiting for the current i ₀₂ to decay, turn on key 3, then current i ₀₁ will begin to increase from the current current level i ₀₂ to a certain set value, when key 3 can be turned off again. Figure 3 shows diagrams (a and b) of the load current with pulse modulation of key 3 with different duty cycle. Obviously, with the key 3 closed, the minimum current level i ₀ will be determined by the discharge current i ₀₂ , which corresponds to the input voltage and current-voltage characteristics of MOB 4. The maximum voltage level during switching does not exceed the remaining voltage on MOB 4. The energy released during switching is absorbed MOB 4. Using a high frequency modulation of key 3 (for example, when using IGBT, the frequency can exceed 50 kHz), reduces the inductance of circuit 2 and increases the resolution of amplitude regulation s the load current for a time limited by the ability to absorb MOB 4 energy.

Based on the scheme of figure 1, it is possible to build a pulse amplitude stabilizer or an adjustable pulse shaper. Key 3 can be controlled with pulse width modulation (PWM), pulse frequency modulation (PFM) or relay control.

In the circuit of FIG. 1, it is possible to limit the absorbed energy of MOB 4 by creating a discharge path for current i ₀₂ using key 3 or by limiting the stored energy in pulse energy storage circuits, bypassing the inductance 2 with an additional circuit.

The maximum allowable absorbed energy MOB 4 (the total absorbed energy of the series-connected MOBs) must be at least 10% of the energy of the pulse storage connected to the shaper.

If the input voltage of source 1 can rise above the classification voltage of MOB 4, then it must be applied to MOB 4 for a strictly limited time, which can be controlled using a blocking key 5. MOB 4 mode control can be created using a current sensor or using temperature control . It is possible to combine several control methods to limit the absorbed energy of MOB 4.

Consider an example implementation of the invention in a specific high-voltage shaper of bipolar pulses of electrical energy, which is shown in figure 4. Such a device can be used to form a defibrillator of therapeutic pulses of electrical energy.

The pulse limiter, made in accordance with paragraph 1 of the claims, form three series-connected keys 3 based on the IGBT, which are bridged by MOB 4. The key control circuits 3 are connected to the controller 7 through the control device 10, which form the key switching path 3.

To switch the polarity of the current in the load 6, an H-shaped bridge circuit 9, known in the art as an H-bridge, is used, based on blocking keys 5, which can be performed, for example, on thyristors. As already noted, as blocking keys 5, it is possible to use mechanical switches made according to any of a variety of known relay polarity switching circuits, for example, on conventional or on-off electromagnetic relays. In any case, turning the keys 5 on and off is ensured at low or zero current. The main requirement for switches 5 is that in a state of low conductivity they must block the current at any possible voltage of the energy source 1 and / or from the voltage coming from the load side.

A load 6 is installed at the shoulders of the N-bridge 9, in which a current pulse of direct or reverse polarity is formed. The upper terminals of the H-bridge 9, through a pulse current limiter and inductance 2, are connected to the positive terminal of the source 1. The lower terminals of the H-bridge 9 are connected to the negative terminal of the source 1. The N-bridge 9 control circuit and sensor output 8 are connected to the controller 7.

Various options are possible for the operating modes of the circuit shown in figure 4. The keys 3 and MOB 4, as well as the H-bridge 9, allow the formation of bipolar discharge pulses at load 6 in the resonant mode (see figure 2) and / or adjustable mode (see figure 3). Switching keys 3 can be performed by the controller 7 synchronously or individually. Obviously, the possibility of individual (non-synchronous) switching of series-connected keys 3 provides MOB 4, even when the voltage of source 1 exceeds the total voltage of keys 3 remaining in a low-conductivity state. The decrease in the rate of change of current in the load 6 when the keys 3 are turned off both in the controlled and in the resonant mode increases the reliability of the driver, reduces the stability requirements of the insulating control circuits for the keys 3 and keys 5.

Figure 5 shows a graph of the transition of current from the positive phase to the negative phase generated using MOB 4. When the energy of the charged capacitor of source 1 or the inductance energy of circuit 2 is reduced to a critical level at which the voltage applied to MOB 4 decreases below the level of the classification voltage , the circuit current changes direction. The residual energy of inductance 2 forms a short pulse of negative current (i ₀₃ ).

In other words, as a result of a short MOB 4 transient of short duration, an interphase pause is formed (see figure 5). When the key 3 is turned off for 1 μs, the current in the load 6 drops over the time interval (t2-t1), which significantly exceeds the time to turn off the key 3. Thus, MOB 4 provides the ability to quickly turn off the keys 3 at any time with small switching overloads and subsequent switching off of the keys 5 in the absence of circuit current, both in the case of a resonant discharge and in a controlled discharge of energy of pulsed energy storage devices. Using high-speed disconnection of the keys 3, it is possible to protect the pulse shaper from high currents in the load (see figure 2). As a threshold overload current sensor, you can use the calibrated parameters of one of the IGBT keys 3.

The invention allows the introduction of additional circuits to absorb the energy of the inductance 2 and / or the use of several inductances. It is possible to use a shaper according to the scheme of a step-down pulse converter with high energy efficiency (see RF patent No. 2398347) while maintaining the principles of the present invention. In this case, part of the inductance energy, when the keys are turned off, is dissipated in the MOB, and the remaining part is closed via diodes to the load.

Figure 6 shows an energy efficient circuit for generating bipolar electrical pulses. Part of the inductance energy is closed through the load 6 with the help of reverse diodes 11, which provide a current circuit between the upper terminal of the inductance 2 and the lower terminal of the bridge 9.

Figure 7 shows an example of a generated bipolar pulse of a controlled discharge at load 6 using MOB 4.

The application of the invention is possible in artificial switching systems of electrical energy. The use of a shaper for artificial switching makes it possible to switch the key of the main circuit at zero current. At the same time, the shaper provides quick adaptation of the artificial switching circuit to the current electrical load mode. For example, when turning on and off a single-operation power thyristor or mechanical keys in DC and AC circuits. In this case, the energy storage of a pulsed storage device could reach 100 MJ, and the overvoltage of such a system would be minimal due to the regulation of the active component of the current of the artificial switching circuit at high frequency using MOB. It is possible to switch the load from one energy source to another energy source without changing the load current. Moreover, at the time of switching the sources, the load current can be formed by the mentioned circuit of artificial switching, including the proposed pulse shaper.

It is possible to series-connect a large number of high-speed keys at high voltage, which can exceed the total maximum allowable voltage of high-speed keys when they are switched on synchronously or asynchronously.

The technical result is achieved due to the fact that high-speed keys are shunted by MOB with parameters that, in combination with high-speed shutdown of high-speed key and energy in a pulse drive, provide a long-term load current conservation compared to the time of switching off a high-speed key. The shaper provides quick inclusion, shutdown, or limitation of electrical energy in the load and protects the keys of the shaper and other devices that are physically connected to the shaper. With MOB, it is possible to adjust the load current for limited time intervals by switching the circuit current between the high-speed switch and the MOB resistance at low or high frequency. The shaper is configured in such a way that it enables fast-acting and blocking keys to be switched on in the absence of an electric current, a high-speed shutdown of a high-speed key with current transfer to the MOB, and a blocking key is turned off in the absence of electric current.

The invention removes the restrictions on the number of MOB operations due to the loss of field emission. Unnormalized energy effects characteristic of the use of MOB as limiters of external overvoltages are excluded. The use of a blocking key eliminates the long-term effect of voltage on the MOB, which also significantly increases the reliability of the isolation of the MOB during switching operations.

Thus, the purpose of the invention is the development of an electric energy generator that is able to provide high pulse power (high voltage and / or current) with the possibility of limiting current, as well as capable of reducing switching surges and resonant fluctuations in the load, increasing the reliability of keys and devices physically associated with this shaper of electric energy - achieved.

Claims (2)

1. An energy pulse generator, in the circuit of which pulse electric energy storage devices are installed: an inductance and / or a charged capacitor and a load containing keys, at least one fully controllable high-speed key with a parallel protective circuit that limits the voltage when the high-speed key is turned off, in series with a high-speed key (s), at least one blocking key (semiconductor or mechanical) is installed, which can block or pass to the circuit, the controller connected to the key control circuits through the corresponding control devices, the switching intervals of all the keys are synchronized in a certain way by the controller both under permissible load and power source states and when deviating from permissible states that are independent of the driver, characterized in that the protective circuit includes at least a metal oxide varistor (MOB) connected to a high-speed switch, forming a pulsed current limiter, while the MOB set the parameters to which, after a high-speed switch is turned off quickly (if there is a certain energy in the inductance of the circuit and / or a charged capacitor), provide a longer load current than the turn-off time of the high-speed switch, with the maximum allowable absorbed energy MOB or the total maximum allowable energy absorbed in series MOB , which is at least 10% of the energy of the pulse energy storage of the shaper, while the voltage on the MOB should not To increase the maximum allowable voltage of a quick-acting key, including at the maximum possible load current, an electric mode sensor is installed in the load current circuit and connected to the driver controller that controls the load current at low or high frequency. 2. The shaper according to claim 1, characterized in that additional blocking keys are introduced in series with the pulse current limiter, forming a circuit for switching the direction of the current in the load.

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