JPH11234103A - Method and device to control switching operation in power transistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an improved control method and device of a switching operation composed of a turn-on operation or a turn-off operation in a voltage controlled power transistor. SOLUTION: These method and device control the switching operation composed of the turn-on operation or the turn-off operation in the voltage controlled power transistor. In this case, at least one current source (S1 and S2) is connected to the control electrode (G) of the power transistor, the recharging of at least one capacitance performed between the control electrode (G) of the power transistor and the main electrodes (C and E) of the power transistor is controlled and thus, the time-depending change rate of at least one of a voltage amount and a current amount is decided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving mechanism for a power transistor, and the driving mechanism is used to control the power transistor during a turn-on operation, a turn-off operation, and a current limiting operation.

[0002]

2. Description of the Related Art Self-excited transducers are currently used in some applications, for example, in static transducers for motor drives, feeders, UPS systems, and the like. In such applications, individual power transistors are typically used to derive relatively high generated voltages.

There are several types of power transistors, the most common being MOSFET and IGBT transistors, bipolar transistors and Darlington transistors. Although the principles of the drive mechanism disclosed by this description can be applied to all types of power transistors, the present invention is essentially applicable to IGBTs.
And for a drive mechanism associated with a voltage controlled power transistor. In the following, when referring to the electrodes of a power transistor, the names gate, emitter and collector are used, in which case the term "emitter" may also include the term "source" as used in MOSFET literature. And, correspondingly, the term "collector" may also include the word "drain".

The following description is intended to illustrate several different reasons why control of turn-on and turn-off operations is desired in power transistors. In this context, the concept of dv / dt control and di
The concept of / dt control is used. These concepts relate to methods that allow controlling or limiting the derivative of voltage and the derivative of current, respectively, in relation to turning on and turning off a transistor. The concepts of turn on and turn off are used to indicate switching on and switching off a power transistor, respectively.

During the turn-on of a power transistor, for example, an IGBT, the turn-on process
In connection with the BT, to prevent overloading of the reverse voltage diode (reverse diode) caused by too fast current increase (di / dt) or too fast voltage breakdown (dv / dt) in the power transistor, the IGBT
Is controlled by controlling the gates. This is especially important for high voltage (≧ 1600V) diodes. High voltage diodes typically have a relatively high recovery charge due to a relatively long charge carrier lifetime. This, in conjunction with the low doping level in the high field region, makes the diode more sensitive to dynamic avalanche or avalanche injection during turn-on, which can be detrimental to the diode. This is the derivative of the current that is negative during turn-on operation (di / d
t) and the amount of voltage increase (dv / dt) need to be limited to acceptable values for the diode. This can be done by smoothly turning on the inverse transistor, ie, keeping the derivative of the voltage at the gate small. At the same time, it is desirable to keep the turn-on loss of the power transistor and the turn-off loss of the diode as small as possible.

During turn-off of the power transistor, voltage increase (dv / dt) can be suppressed by using control via the gate for several reasons. d
By controlling v / dt, it is possible to limit the amplitude of the voltage overshoot that always occurs when the current in the inductive circuit is turned off. This may be necessary to limit the stress on the transistor, as described in the transistor data sheet. Control of the derivative of the voltage is also usually required when the power transistor is turned off (in connection with the current limitation of the power transistor) when a short circuit or so-called arcing occurs. Without control or limiting of the voltage derivative (dv / dt), transistor elements can be easily damaged due to the fact that high peak voltages readily occur during the turn-off of the short-circuit pulse.

A high voltage IGBT (eg, ≧ 1600V
Other difficulties are added when utilizing IGBTs in the voltage range of The IGBT's SOA (Safe Operating Area) becomes dependent on where the voltage derivative turn-off occurs. By limiting the voltage derivative, higher currents can be turned off or higher peak voltages can be tolerated. This is the correct dv / dt
Control continues electron injection for a significant portion of the turn-off operation, thereby suppressing the process of creating a dynamic avalanche, thereby allowing higher current / voltage during turn-off operation than would otherwise have been the case. Can be explained by the facts that make it possible.

The control of dv / dt also depends on the load (eg,
It is also used to limit the dv / dt that the motor receives. The reason is that high dv / dt imposes local stress on the insulation at the load, which can subsequently destroy the insulation. Similarly, a high voltage derivative dv / dt can cause a voltage transient, which is sent out and reflected on the cable, creating voltage spikes and creating insulation problems. High dv / dt values can also cause radio interference, ie, interfere with other electronic devices. To comply with the EMC standard (EMC = electromagnetic compatibility), it may be necessary to design a filter that reduces these disturbances. In that case, dv / dt control helps to solve the problem, so to speak, at the root.

A disadvantage of controlling the voltage derivative dv / dt is that the turn-on and turn-off losses are usually increased to some extent. However, if the turn-on and turn-off operations are completely controlled, the loss can be minimized. The best way to turn on and turn off a transistor, respectively, can always exist if its purpose is to minimize turn-on and turn-off losses, respectively. One requirement in that case is that this optimal method is known and that by adapting the control parameters the transistor can always be turned on / off in this optimal way.

There are other reasons why it is desirable to control the turn-on and turn-off operations of the power transistor. One such case where a particularly high demand is placed on this control is in the series connection of the transistors. In such a series connection of power transistors, the individual transistors are:
It is intended to receive part of the high voltage due to the voltage division, and there are several factors to consider. Some of the most important problems to be solved are: static partial voltage, dynamic partial voltage, partial voltage under short-circuit conditions. The main task of the present invention with respect to these above-mentioned factors is to seek a solution to the problem of how dynamic voltage division is realized in an optimal way, i.e. during transistor turn-on and turn-off. is there. For this, various proposed methods are known, among which several different methods are known,
In these methods, an external partial pressure element, for example, a combination of a diode, a resistor and a capacitor is used. However, these methods do not provide a solution to the underlying problem,
It merely provides an attempt to limit the voltage difference that occurs across the individual transistor modules in the chain of series-connected transistors to an acceptable level by adding external components, which are designed according to such known principles. This increases both the volume and the cost of the device, for example in the form of a transducer.

Currently used converters typically use a very simple method of controlling or limiting each of dv / dt and di / dt. In a general way, during turn-on of the transistor,
The gate is connected to a voltage source by a resistor called a so-called gate resistor. This resistor limits the current supplied by the voltage source, so that the proper selection of the resistor can affect the speed at which turn-on occurs.
Similarly, a combination of a voltage source and another resistor can be used to affect the speed at which turn-off occurs. This method is simple and often used,
It offers only limited control possibilities. During the turn-on of the transistor, it is di / dt and dv / d
and t cannot be affected separately. Similarly, for example, the voltage derivative during turn-off depends greatly on what current the turn-off takes place (the higher the current, the larger the voltage derivative). In order to avoid overshoot of the voltage during the turn-off of the short-circuit current, a method is often used to first detect whether the on-voltage of the transistor exceeds a given level. If so, the current is determined to be large enough that the turn-off must be performed smoothly, ie, with a reduced voltage derivative, which means that the turn-off is
This means that the operation is performed with a higher gate resistance than usual.

[0012] The turn-off and turn-on operations at a given current also depend on the temperature of the transistor. Further, when different samples of the same type of transistor are tested by the same drive mechanism, significant changes in turn-off and turn-on behavior can occur. Such a change presents a problem with regard to the division of the transient current in the case of a parallel connection of the transistors and a problem with the division of the transient voltage in the case of the series connection of the transistors.
Therefore, with the aim of achieving a more optimal turn-on and turn-off, in part by better control of the process in its details, and in part by the current, temperature and temperature of the turn-on and turn-off operations, and of transistors of the same type. There is a need for a method that can better control each possible turn-on and turn-off operation of a power transistor with the aim of reducing the dependence on naturally occurring fluctuations.

Since the known solution has not been determined to be the best solution to meet our needs, it is necessary to control the so-called linear region, ie the controllable region, during the switching of power transistors such as IGBTs. One approach is to use the "intelligent" drive mechanism shown by the present invention. The solution suggested in the present invention is the most commonly used today,
Although somewhat more complex than methods involving so-called gate resistance adaptation, the burden for that complexity is that in many applications, the power transistor can be used more efficiently with more optimal control. Give more than that burden.

[0014] PCT application WO 95/28767 includes:
An apparatus for controlling turn-on and turn-off operations of a semiconductor device is described. The turn-off operation is
The feedback of the voltage of the freewheeling diode is controlled by continuously reducing the current flowing into the control electrode of the transistor, and the current flowing into the control electrode of the transistor is minimized when the voltage of the freewheeling diode becomes equal to zero. Reaches the value. If PCT application WO 95 /
According to 28767, if an attempt is made to control the turn-off operation, and if it is desired, as is often the case, to combine the short delay of turn-off with the control of the voltage derivative, it enters the control electrode of the transistor. The control current must be reduced, preferably in a well-controlled manner and as a function of the voltage across the other components, by a fraction of a microsecond. Such a method is not simple enough to perform satisfactorily.

[0015]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method and an apparatus for controlling a switching operation including a turn-on operation or a turn-off operation in a voltage-controlled power transistor.

[0016]

Some features of the invention will be apparent from the features set forth in the independent claims. The concept described is based on the fact that the gate charging characteristics of a power transistor are known at different collector voltages during the switching of the transistor, and that this characteristic does not change significantly between different samples of the same power transistor. Partially based. This is especially important in devices that include several power transistors working together in a circuit, for example in a high-voltage valve with power transistors connected in series or in a high-current valve with power transistors connected in parallel. It is.

In switching a power transistor, some charge must be added to (or removed from) the gate in order to change the transistor between on and off states. By controlling the charging current during the switching operation of the power transistor, switch-on and switch-off operations (herein referred to as turn-on and turn-off operations, respectively) can be controlled. Attempts to control the charging current by using a voltage source and a resistor connected to the gate in such a method are not particularly advantageous. In that case, the magnitude of the charging current and its time dependence depends on several factors, such as the leakage inductance between the gate and the power transistor, and the internal gate resistance often provided internally by the manufacturer in the transistor module. And the crystal temperature of the transistor and the main current through the power transistor.

A better method, one feature of the present invention, is that a controllable current source is more sufficient when the operating point of the transistor moves through a current-limiting part (commonly referred to as a linear part) of the transistor's characteristics. Controlled (for example,
The charging current (of the current source) is supplied to the gate. For better control of the collector voltage and the voltage derivative dv / dt, it is also advantageous to increase and linearize the Miller capacitance of the transistor by introducing a special capacitor between the collector and the gate. is there. This capacitor must generally be attenuated to prevent oscillation.

The technique of the present invention described above offers many advantages over the possibility of controlling a transistor by a MOS gate, such as an IGBT transistor. Furthermore, this technique allows the control of the transistor during switching and current-limiting operations, with the aim of minimizing switching losses, increasing the safe operating area (SOA), ie the transistor is always SOA To provide a reliable method for short circuit protection, and to limit dv / dt at the load if desired, ie, EM
It is to simplify C protection, to provide good current division during parallel connection of power transistors, and to provide good voltage division during series connection of power transistors.

This technology uses a high voltage IGBT (1600 V
Or more), because good control of the dynamics of such a transistor during switching can increase its SOA while minimizing switching losses. is there. However, this technique also requires lower voltage IGB
Other MOS like T and MOSFET transistors
It can also be used for control power transistors.

During the turn-off of the power transistor, the voltage derivative dv / at different values of the collector voltage
Being able to control dt, that is to say that the derivative of the voltage with respect to time can be given different values at different collector voltages can be very important. At low collector voltages, it is usually advantageous to increase the value of this voltage derivative in order to keep the switching losses low. on the other hand,
At high collector voltages (near or above the nominal voltage), it is desirable to reduce the increase in voltage, ie, to limit the voltage derivative to low values. The limitation of the voltage derivative at this high voltage is also
What is called (switching safe operation area), that is, the safe operation area during switching of the transistor is increased. Furthermore, it can be used during the series connection of transistors for the purpose of improving the dynamic voltage division. By limiting the voltage derivative to a very low value as soon as the voltage of the transistor exceeds a certain level, the maximum voltage picked up by the transistor in connection with the turn-off process can be limited.

According to another feature of the invention, the voltage derivative is controlled to be dependent on the collector voltage by controlling the current source connected to the gate of the power transistor by its collector voltage. A voltage divider is used to detect the collector voltage, and the detected voltage is used to control the value of the current supplied from the current source. This means that the driving mechanism including the variable current source performs the most appropriate turn-off operation. For example, if a transistor is turned off in one case where a current limit is imposed on the device containing the transistor, ie, there is a high collector voltage on the transistor even before the turn-off operation is initiated When it does, the gate drive automatically detects this and slowly turns off the transistor (with a small voltage derivative), keeping the transistor in the safe operating area.

The capacitance in coordination with the above-mentioned controlling current source can in principle consist of the self-capacitance of the power transistor between the gate and the emitter. However, to achieve better linearity and better control of the function, a capacitance substantially determined by the capacitor connected between the gate and the collector in parallel with the self-capacitance of the power transistor is preferred. Control of the type described above is performed almost independently of the load. This means that complete control of the turn-off is performed independently of the current through the load.

According to yet another feature of the present invention,
During the turn-on of the power transistor, the current derivative and the voltage derivative (associated with the current and voltage, respectively, between the emitter and collector, which are the main electrodes of the transistor), are controlled substantially independently of each other. The gate voltage is varied with the aid of a current source connected to this control electrode, thereby charging the gate-emitter capacitance. At a certain voltage level _Vth , the power transistor starts conducting. During the time of the current increase (di / dt), the current through the transistor is controlled by the gate voltage. According to the present invention, the capacitor providing the extra capacitance (in addition to the transistor's self-capacitance) is now usually connected between the gate and the emitter, so that when the turn-on operation is started, Starts charging soon. In order not to unnecessarily increase the turn-on delay and the charge required for the turn-on operation, a zener diode can be introduced in series with this capacitor, which has a gate voltage of approximately V
_When it becomes equal to _th , conduction starts. This is done properly by choosing a Zener diode that starts conducting at the appropriate voltage. The total capacitance between the gate and the emitter (plus the external capacitance and the self-capacitance of the transistor), together with the magnitude of the gate current, determines the derivative of the voltage between the gate and the emitter, and this voltage derivative The function thus determines the current derivative (di / dt) in the transistor. Choosing the desired value of the special capacitor between the gate and the emitter can reduce its current derivative to the desired amount.
During normal turn-on (without a short circuit), the current derivative is controlled as described above until the collector current reaches a peak value ( _ipk ) determined by the load and the reverse diode (see FIG. 4). ). Reaches the peak value (i _pk), voltage of the transistor (v _CE) begins to drop.
According to a feature of the invention, where the voltage derivative dv / dt
Is instead combined with the capacitance between collector and gate (intended for turn-on operation)
It is controlled by a current source.

The current sources intended for turn-on and turn-off, respectively, are voltage limited, since the current therefrom is such that the gate voltage is the desired value for the static on-state and off-state of the controlled transistor. Means to descend toward zero.

For example, in the case of a series connection, the present invention provides for an arbitrary number of power transistors in the valve because the control device of the present invention limits a large voltage increase in each of the series connected transistors. Can be connected in series. Other features of the invention will be apparent from the appended claims.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Some embodiments of the present invention are attached.
This will be described below with reference to the drawings. One typical example of the present invention
A typical area of application is during the control of the bridge connection in FIG.
It is about. This figure shows two IGBTs (T1 and T1).
And T2) and two power transistors of the form
With their reverse diodes (D2 and D1, respectively)
1 shows a prior art bridge connection. Used in description
The symbols used are evident from the figures. DC voltage V_DCIs 2
Supply to this bridge for conversion in one valve
Each valve is connected to the power transistor T1 and the power transistor T1.
And T2. Power transistor, for example
If the current flowing through T1 is the symbol i _cRepresented by
While the reverse diode flows through D2 in this example.
Current is i_FIt is represented by Take on the transistor
The voltage is v_CEIt is represented by Intermediate link capacitor C
_DC, T1 and D2 (or C_DC, T2 and D1)
In the loop that passes, the intended inductance is usually
No, but an unavoidable stray inn here represented by L1
Ductance is dependent on turn-on and turn-off
affect. Converted current out of this bridge
Is i_ph(I_phase). Transistor T
1 and T2 are designated DU1 respectively.
And DU2.

FIG. 2 shows an example of a driving mechanism, which controls a power transistor, for example, an IGBT according to a conventional technique. This control is performed by the control unit GD
C controls the two switches synchronously, causing the gate G of the transistor to pass through a separate series resistor to + 15V
And -5 V, respectively.

FIG. 5 shows a drive mechanism constituting one embodiment of the present invention. The rightmost symbol C in this figure,
G and E respectively relate to the collector, gate and emitter of the power transistor to be controlled by the drive mechanism of this figure.

In this example, the emitter E is connected to the zero voltage line of the drive mechanism. The gate G is connected to a driving voltage of +15 V by the first current source S1. The first current source S1 is controlled so as to supply a current to the contact line 1 of the gate G. Thereby, the current source S
The current from 1 charges the capacitance that exists between the gate G and the emitter E. This capacitance is
The self-capacitance between the electrodes described above,
If it is desired to be able to set both / dt and dv / dt substantially independently of each other, preferably a capacitor C1 as a complement to the self-capacitance connected between the gate and the emitter is provided. Used.
Between the emitter and the gate there is a zener diode Z1 in series with the capacitor C1. In the simplest embodiment of the invention, this Zener diode is omitted, in which case the current source S1 must supply a somewhat higher charge. The current source S1 supplies a current under the control of the gate drive controller (GDC) and simultaneously turns on the power transistor controlled by the drive mechanism, with the voltage on the contact line of the gate rising. As described above, at some voltage level _Vth , the power transistor will carry current. By selecting the value of the Zener diode Z1,
This zener diode is made conductive at a voltage approximately equal to V _th . Thus, the capacitor C
One begins to charge at the same time as the internal capacitance of the transistor between the gate and the emitter. In this way, the capacitor C1 limits the rate at which the voltage vg between the gate G and the emitter E increases, which in turn determines the rate at which the collector current of the transistor increases.
In this way, as long as the power transistor is substantially turned on in the inductive circuit, the capacitor C1
Of the capacitance value determines the magnitude of the current derivative during turn-on of the power transistor when the power transistor is within a current-limiting (linear) operating range (see FIG. 4).

After turning on the power transistor, the collector current _ic flows between its main electrodes (C, E), and the current increases to a peak value _ipk determined by the load and the reverse diode. Thereafter, the current of the power transistor is not controlled by the gate G. Instead, the voltage v _CE drops and the voltage derivative dv / dt, ie the voltage breakdown of the power transistor, is controlled with the aid of the capacitance present between the collector C and the gate G. According to the invention, this capacitance can also consist in principle of self-capacitance. However, again, it is advantageous to switch at an external capacitance in the form of a capacitor C2 between the collector and the gate. This capacitance linearizes the internal Miller capacitance, which makes the voltage derivative sufficiently proportional to the gate current (see FIG. 4). At this time, the value of the capacitance of the capacitor C2 controls the magnitude of the voltage derivative dv / dt in cooperation with the magnitude of the control current.

In order to be able to control the turn-off operation of the power transistor also as desired, according to one embodiment of the invention, a second current source S2 further conducting the gate G to a drive voltage of, for example, -5V Connect to The second current source S2 is controlled so as to supply a current to the gate contact line 1. At that time, the current source S2 supplies a negative current, which recharges the capacitance present between the collector and the gate of the transistor. Even during turn-off, the capacitance between the collector and the gate can consist of self-capacitance. To obtain better control of the turn-off operation, it is more advantageous to switch an external external capacitor C2 in parallel with the self-capacitance between the gate G and the collector C.

During the turn-off of the power transistor, the current source S2 is controlled by the gate drive controller GDC to supply a current during the turn-off of the power transistor controlled by the drive mechanism, and to reduce the voltage on the contact line 1. Causes a gate descent. With this gate descent,
The current source S2 draws charge from the gate. For example, if the power transistor is made of an IGBT, the gate voltage will be the voltage V _CE between the main electrode and the transistor _.
>> Before starting pickup of V _CEsat (sat = saturated), drop to about + 10V. However, at what gate voltage this happens depends, inter alia, on the current flowing through the transistor at this very moment. During the initial phase of the voltage increase, the current source substantially charges the internal Miller capacitance between the gate and the collector. However, as the voltage increases, this capacitance decreases,
At a voltage of about 40V, the external capacitor C2 is dominant instead. The increase in voltage (dv / dt) is then substantially determined by the current used by current source S2 and by the capacitance value of external capacitor C2 (FIG. 3).

By the operation described above, the capacitor C2 cooperates with the current from the current source S1 during the turn-on and the current from the current source S2 during the turn-off,
Determine the voltage derivative of the transistor. In this way, the voltage derivatives during turn-on and turn-off can be selected independently of each other. The size of the capacitor C2 is suitably chosen to be more dominant than the transistor's Miller capacitance at voltages above, for example, 50-100V. The current that must be supplied by the current sources S1 and S2 is then controlled by the maximum voltage derivative during each of the desired turn-on and turn-off. At that time, the current provided by current source S2 will typically be reduced during turn-on, if only the internal input capacitance (between gate and emitter) of the transistor is allowed to determine di / dt during turn-on. Becomes too large with respect to the reverse diode. In that case, an external capacitor C1 may be added between the gate and the emitter to limit the current derivative di / dt during turn-on to an appropriate value for the reverse diode.
In this way, both di / dt and dv / dt during turn-on can be selected sufficiently independently of each other.

In order not to unnecessarily increase the turn-on delay and the charge required for the turn-on operation, a Zener diode Z1 can be introduced in series with the capacitor C1. During the turn-off of the power transistor, the Zener diode Z1 is conducting and the capacitor C1 is at a voltage sufficiently equal to the gate G of the power transistor, for example-.
Charged to 5V. Thus, the breakdown voltage of the Zener diode is 5 V + V _th in this example, such that during turn-on of the power transistor, the Zener diode starts conducting when the voltage at the gate G of the transistor reaches the voltage V _th. They should be chosen almost equally. Thus, the capacitor C1 is
From the moment when the current starts to flow between the main electrodes of the power transistor, it affects the entire turn-on operation. By properly selecting the gate voltage level in the off state of the power transistor, it is possible to prevent the capacitor C1 from affecting the turn-off operation of the power transistor. For example, if V _th is 5 V and the gate voltage level of the power transistor in the ON state is +15 V
Then, the gate voltage level in the off state of the power transistor should be ≦ −5V. In that case,
A suitable breakdown voltage for this Zener diode is ≧ 10V, and when the power transistor is turned on, the aforementioned capacitor will have approximately V _th , ie +5
It has been recharged higher than V. Therefore, during the subsequent turn-off operation, the Zener diode Z
1 does not carry current until the voltage between the gate and the emitter of the power transistor drops below _Vth . Then the capacitor C1 can no longer influence the transistor turn-off process.

The current sources S1 and S2 are voltage limited. The main task of the Zener diodes Z2 and Z3 is to ensure that the gate voltage does not exceed the value specified for the transistor (eg, in the context of a short circuit) or fall below the value specified for the transistor. It is to limit the voltage.

The gate drive controller GDC can be controlled using at least two methods. The two current sources S1 and S2 have a gate voltage of +1 during the turn-on operation and the turn-off operation, respectively.
It can be controlled to supply a varying current according to a predetermined process without detection of the collector voltage v _CE until it has finished rising or falling to a voltage level near 5V or -5V, in which case the gate drive control The equipment is
It is only supplied with an input signal In which supplies information about the times at which the transistors are switched on and off. In another embodiment of the present invention, R
A broadband voltage divider including C circuits RC1 and RC2 is connected in parallel with the connection between the emitter and collector of the power transistor (FIG. 6). At this time, a detection line 2 for detecting the collector voltage v _CE is connected to a point 3 between these two RC circuits. In this case, the voltage of the detection line is controlled as described above by controlling the gate drive control device GDC during turn-on and during turn-off, respectively, to increase the current from each of the first and second current sources. Can be used to obtain the current and voltage derivatives of The gate drive control device GDC
The currents from the first current source S1 and the second current source S2 are controlled to have a predetermined function of the collector voltage v _CE . In this way, the dependence of the control signal on the collector voltage is described, for example, by the function cs ₁ (t) = f (v _CE (τ), τ ≦ t), where the instantaneous value of v _CE and / or Or both of the history values can be used to influence the control signal. This gives, for example, the possibility to create a voltage derivative during turn-off according to FIG. 3, in which case this derivative is given a different value step by step depending on the collector voltage. By way of example, FIG. 3 shows that the value of the first derivative during the increase of the voltage of the transistor is 4 kV / μs and that as the voltage approaches _VDC , the value of the derivative is reduced to 1 kV / μs. I have. Of course, values other than those shown may be selected. Also, the decreasing value of the voltage derivative may be more than two steps,
Alternatively, it can be changed continuously.

The gate drive control device GDC supplies two control signals, one control signal cs ₁ for controlling the current source S1 during the turn-on of the power transistor, and another control signal cs _1. cs ₂ is for controlling the current source S2 during turning off of the power transistor. Gate drive controller GDC
Uses only known techniques and will not be described in further detail here. Each of the control signals cs ₁ and cs ₂ can be digital or analog depending on the nature of the current source to be controlled.

The current sources S1 and S2 are also each designed by known techniques. The controllable current source can be designed with a normal transistor switch. If very good temperature stability is desired, the switch of FIG. 7 can be used. This figure shows an example of a current source S2 according to the invention, in this case, for example, Siliconix Incorporati
on) constitutes a modification of a current source of the type commercially available from On). If a controllable current source with very good stability is desired, a larger number of digitally controlled current sources can be used, the task of each of these current sources being to supply a fixed current. It is. In that case it is possible to realize a current source that can change quickly between a number of different values of supply current, thereby giving the transistor voltage derivative different values depending on the instantaneous value of the collector voltage. The above-described control can be realized.

The design of the current source S1 is the same as the design described for S2. Cs ₂ in the example of FIG.
Is a digital signal that controls the switch SW that changes between two positions. In the examples of FIGS. 5 and 6, two controllable current sources are shown. If only one of the turn-on or turn-off operations requires optimized control, of course, by using only one of the first and second current sources (S1, S2) described above with an associated capacitor, It is possible to control the desired derivative as described above, and in such a case,
The second current source can be replaced by a conventional solution including the voltage source, the semiconductor switch and the resistor of FIG.

[Brief description of the drawings]

FIG. 1 shows a bridge connection with two IGBTs and two reverse diodes according to the prior art, which may constitute a branch for the phases in a three-phase inverter.

FIG. 2 shows a conventional drive circuit for an IGBT, in which the setting of the turn-on operation and the turn-off operation is performed by selecting the respective gate resistors to a value appropriate for the transistor and for the application. Will be

FIG. 3, for example, shows the ideal control of the voltage derivative dv / dt during turn-off of an IGBT during high-current turn-off in an inductive circuit or during turn-off of an IGBT to avoid over-voltage during a series connection of several transistors. .

FIG. 4 is an example of independent independent control of di / dt and dv / dt during IGBT turn-on to reduce turn-on losses without exceeding an acceptable amount for the negative current derivative of the reverse diode. Is shown.

FIG. 5 shows a solution for controlling a power transistor according to the invention, in which di / dt and dv / dt at turn-on and dv / dt at turn-off.
A fixed value of / dt has been previously selected.

FIG. 6 shows another solution for the control of a power transistor according to the invention, in which the control of di / dt and dv / dt at turn-on and dv / dt at turn-off further comprises the turn-on operation; And prior to each turn-off operation, it may depend on the collector voltage developed across the transistor.

FIG. 7 shows an example of a voltage limited current source design that provides a stable current with low temperature dependence, which is useful when it is desired to control the power transistor in a very well-defined manner. Which may be, for example, the case of a series connection of several transistors according to the invention.

[Explanation of symbols]

C Collector C1 capacitor C2 capacitor cs ₁ control signal cs ₂ control signal E emitter G gate GDC gate drive control apparatus i power transistors of the current RC1 RC circuit RC2 RC circuits S1 first current source S2 second current source v voltage of the power transistor v Collector voltage of _CE power transistor

Continuation of the front page (72) Inventor Anders Persson Vestelås, Sweden Sora Niigatan 1 (72) Inventor Rennard Zdanskiy Sweden Vestelås, Vegagatan 6di

Claims (26)

[Claims] 1. A method for controlling a switching operation including a turn-on operation or a turn-off operation in a voltage-controlled power transistor, wherein the power transistor comprises:
Control electrode (G), first main electrode (E), and second main electrode (C)
And a voltage (v) and a current (i), which are operating variables of the transistor, are generated between these main electrodes. The turn-off operation of the power transistor is performed by the control electrode (G) of the power transistor; The second
The capacitance between the main electrode and the collector (C) is controlled by recharging controlled by the current source (S2); and the capacitance is controlled by the control electrode (G) of the power transistor and the second electrode. Comprising the sum of the self-capacitance of the power transistor between the main electrode (C) and the capacitance of the external capacitor (C2); and the voltage of the voltage between the main electrodes (C, E) of the power transistor. The rate of change over time (dv / dt) is determined. 2. The turn-on operation of the power transistor causes an additional current source (S1) of the capacitance between the control electrode (G) of the power transistor and its second main electrode, the collector (C). ), And a rate of change (dv / dt) of the voltage between the main electrodes (C, E) of the power transistor is determined. The method of claim 1, wherein 3. The turn-on operation of the power transistor comprises an additional current source (S1) of capacitance between the control electrode (G) of the power transistor and its first main electrode, the emitter (E). And a time change rate (di / dt) of the current passing through the main electrodes (C, E) of the power transistor is determined. Item 3. The method according to Item 2. Wherein said current source (S2) is characterized and supplying a constant current having a predetermined time course, and that the current source is controlled by the control signal (cs _2), claim 2. The method according to 1. 5. at least one of said current sources (S1, S2), is controlled and supplying a constant current having a predetermined time course, current source is a control signal (cs _1, cs ₂₎ The method according to claim 2 or 3, wherein: 6. A control signal (c) provided by said current source (S2).
_2. The method according to claim 1, characterized in that it is controlled by s ₁ , cs ₂ ) to supply a current dependent on the effective value of the collector voltage (v _CE ) in the power transistor. 7. is controlled by at least one control signal of said current source _{(S1, S2) (cs 1} , cs 2),
Collector voltage (v _CE ) in the power transistor
4. A method according to claim 2 or 3, characterized in that a current is supplied which is dependent on the effective value of. 8. A control signal (c) provided by said current source (S2).
The method according to claim 1, characterized in that it is controlled by s ₂ ) to supply a current dependent on the effective and historical value of the collector voltage (v _CE ) at the power transistor. 9. controlled by at least one control signal of said current source _{(S1, S2) (cs 1} , cs 2),
Collector voltage (v _CE ) in the power transistor
4. A method according to claim 2 or 3, characterized in that a current is supplied which depends on the effective value and the history value of. 10. The current source (S2) comprises a number of digitally controlled partial current sources, the current from the current source (S2) being connected to each individual partial current source by a respective partial current source. 9. The method according to claim 8, wherein the selection is made by controlling by a control signal assigned to the source. 11. At least one of said current sources (S1, S2) comprises a number of digitally controlled partial current sources, said current from said current sources (S1, S2) being each individual part. 10. The method according to claim 9, wherein the current sources are selected by controlling them by means of control signals assigned to the respective partial current sources. 12. The current source (S2) is controlled by an analog control.
Signal (cs₁, Cs _TwoAnalog control controlled by
9. The method according to claim 8, being a current source. 13. at least one of said current sources (S1, S2), A method according to claim 9, characterized in that an analog controlled current source which is controlled by an analog control signal (cs _1, cs ₂₎ . 14. A gate drive controller (GDC) for applying at least one control signal (cs ₁ ) to said additional current source (SDC).
1), and a predetermined temporal change rate (di / dt) of the current during the turn-on of the power transistor.
And / or a predetermined temporal change rate (dv /
14. The method according to claim 11 or claim 13, wherein the control signal controls the current source such that dt) is obtained. 15. A gate drive controller (GDC) for applying at least one control signal (cs ₂ ) to said current source (S2).
And the control signal controls the current source so that a predetermined temporal change rate (dv / dt) of the voltage is obtained while the power transistor is turned off. Item 13. The method according to Item 12. 16. The gate drive control device (GDC) is supplied to at least one control signal (cs ₂₎ the current source for controlling the turn-off operation of (S2), the voltage during the turn-off of the power transistor 14. The method according to claim 11 or claim 13, wherein the control signal controls the current source such that a predetermined rate of change over time (dv / dt) is obtained. 17. The method according to claim 1, wherein the turning off operation of the transistor is performed such that the value of the voltage derivative (dv / dt) decreases. The current is applied to the control signal (c
The method of claim 15 or claim 16, characterized in that s ₂₎ is controlled. 18. A control device for a switching operation including a turn-on operation or a turn-off operation in a voltage-controlled power transistor, wherein the power transistor includes a control electrode (G), a first main electrode (E), and a second main electrode ( C), a voltage (v) and a current (i), which are operating variables of the transistor, are generated between these main electrodes, and the control electrode (G) of the power transistor and a collector which is a second main electrode thereof At least one capacitance between the control electrode (G) and the control electrode (G) between the control electrode (G) of the power transistor and its second main electrode (C); Comprising the sum of the capacitance of an external capacitor (C2) connected between the second main electrode (C) and the collector; A flow source (S2) is connected to the control electrode (G) of the power transistor, and when the power transistor is turned off, the control electrode (G) of the power transistor and the collector, which is a second main electrode thereof. Controlling the recharging of said capacitance between (C) and
Thereby, a temporal change rate (dv / d) of the voltage between the main electrodes (C, E) of the power transistor is obtained.
determining t). 19. The capacitance between the control electrode (G) of the power transistor and an emitter (E) that is a first main electrode thereof is also determined by the self-capacitance, the control electrode (G) and the first main electrode. 19. The device according to claim 18, comprising the sum of the capacitance of an external capacitor (C1) connected between the emitter and the electrode (E).
An apparatus according to claim 1. 20. An additional current source (S1) is connected to the control electrode (G) of the power transistor, and during the turn-on of the power transistor, the control electrode (G) of the power transistor and its second electrode. Controlling the recharging of the capacitance with the collector (C), which is the main electrode, whereby the rate of change of the voltage over time (dv / d) between the main electrodes (C, E) of the power transistor; dt) is determined.
Or the device according to claim 19. 21. The additional current source (S1) is connected to the control electrode (G) of the power transistor, and during turn-on of the power transistor, the control electrode (G) of the power transistor and its second electrode. Controlling the recharging of the capacitance between the emitter (E), which is one main electrode, and thereby the rate of time change (di) of the current between the main electrodes (C, E) of the power transistor. 21. The apparatus according to claim 20, wherein / dt) is determined. 22. A gate drive control device (GDC) for generating a control signal (cs ₂ ) for controlling said current source (S2) to supply a predetermined current during said turn-off operation. Apparatus according to claim 18 or claim 19, characterized in that: 23. A control signal (cs ₁ , cs ₂ ) for controlling the current sources (S1, S2) to supply a predetermined current during the turn-on operation and the turn-off operation, respectively, by a gate drive control device (GDC). 22. Apparatus according to claim 20 or claim 21, wherein the apparatus is adapted to generate). 24. A voltage divider (RC1, RC2) between the two main electrodes (C, E) of the transistor detects a collector voltage and supplies a feedback signal to a gate drive controller (GDC). It is adapted to generate, thereby characterized in that the current from the at least one current source (S1, S2) is controlled by a control signal which constitutes a function of the collector voltage (cs _1, cs ₂₎ An apparatus according to claim 20 or claim 21. 25. A voltage divider (RC1, RC2) between the two main electrodes (C, E) of the transistor detects a collector voltage and provides a feedback signal to a gate drive controller (GDC). the is adapted to generate, whereby the current from the at least one current source (S1, S2) is controlled by a control signal dependent on the instantaneous value and historical values of the collector voltage (cs _1, cs ₂₎ 22. The device according to claim 20 or claim 21. 26. The method according to claim 20, wherein at least one of said current sources comprises a plurality of digitally controlled partial current sources.
An apparatus according to claim 1.