ES2366378T3 - PROTECTION CIRCUIT DEVICE FOR A SOLAR MODULE. - Google Patents

Abstract

Protection circuit device for a solar module, in which a plurality of solar cells that work partly in normal service and at the same time partly in case of shading are connected in series, with at least one switching element (1) controllable electrical that serves as a branch element, whose switching section can be connected in parallel to the plurality of solar cells, with a power circuit (50) to supply a control voltage for the control electrode control of the branch element ( 1), characterized by a disconnector (40) for blocking the voltage applied in the normal service to the switching section of the branch element to the supply circuit (50) and for switching the voltage applied to the switching section in case of shading of at least one solar cell to the power circuit (50).

Description

The invention relates to a protection circuit device for a solar module, in which a plurality of solar cells are connected in series. A protection circuit device of this type is known from JP 2000 174 308.

Solar modules are generally known and are formed according to Figure 1a usually by a series connection of cells, which provide an individual voltage Uz of approx. 0.5 V to 1 V. In case of partial shading of one or more cells or also in case of different properties of the cells, in particular of the short-circuit current, in case of a load, the voltage in the shaded cells. In the worst case, that is, in case of a short circuit of the solar generator, eg in the case of a service in a bypass battery charge regulator, the sum of the voltages of all the non-shaded cells in the blocking direction in the shaded cell.

Next, the concept "case of shading" will always be used regardless of the actual cause of the voltage inversion and for the non-shaded service the concept of "normal service".

The permissible blocking voltage of a solar cell is located in a few V to a few 10 V. Depending on the number of non-shaded cells connected in series with the shaded cells, the permissible blocking voltage can be exceeded, which can lead to local penetrations of the barrier layer already irreversible damage to the cell. To avoid this inadmissibly high blocking voltage, it is known to ideally connect a so-called bypass diode in parallel to each of the cells. The costs are considerable and are only acceptable in special applications, see eg space navigation. In current solar modules on the market, therefore, according to Figure 1a subgroups UGA, UGB, ... UGX of cells connected in series, eg 18 to 24, which are respectively protected by a bypass diode are formed. These are connected by connection points 11, 12 with the corresponding subgroup. For clarity, in Figure 1a, the bypass diode is only represented for the UGB subgroup.

In normal service, according to Figure 1b, the sum of the voltages of the Z1 cells, to Zn, belonging to the subgroup, that is, approx. 15 V to more than + 20 V. The blocking current IS should be minimal to avoid losses. In the case of a total shading of one or more cells in a subgroup according to Figure 1c, the bypass diode 2 flows the short-circuit current or the ISG working point current generated by the cells arranged outside the subgroup, the non-shaded cells This generates a drop in voltage UD of approx. Depending on the diode technology used, the current flowing and the temperature of the diode. -0.4 V to more than -1 V. In the shaded cell, therefore, in the worst case, the sum of the voltages of all the non-shaded cells inside the corresponding subgroup, plus the drop, falls of voltage in the bypass diode.

The number of cells gathered in a subgroup is chosen in such a way that in the worst case the permissible blocking voltage of the disconnected individual cell is not exceeded. This leads to a typical number of approx. 18 to 24 cells per subgroup.

For the known bypass diode, the following operating conditions therefore result:

In the normal service shown in Figure 1b, the voltage of the cells gathered in a subgroup in the blocking direction is applied to this diode, that is, typically approx. +15 V to + 20 V. In the case represented in Figure 1c, with a total shading of a cell inside the corresponding group, the current of the ISG solar generator flows through the bypass diode and causes a voltage drop UD of approx. -0.4 V to more than -1 V. In the description set forth below, it is assumed for ease that a blocking voltage of + 20 V and a voltage in conduction state UD of - 0.6 V are produced, other values may also occur.

Bypass diodes are usually housed in a junction box that is connected to the solar module, so they are exposed to ambient temperatures of approx. -20 ° C to more than 85 ° C. Two or three diodes are typically housed in a box for two or three UGA, UGB and UGC subgroups. To increase the permissible ISG solar generator currents, it is also possible to connect several bypass diodes in parallel.

In the bypass diodes used in the state of the art, in case of shading a relatively large lost power is produced. For a short time, a lost power of this type can be absorbed without problems by the diode, although in the case of long-lasting shading it is difficult to dissipate the amount of heat that is generated from the diode and the junction box. It is also necessary to take into account the circumstance that the maximum loads, that is, the maximum solar currents occur in most cases when at the same time the ambient or module temperatures are high. The problem is complicated as the size of the solar cells increases, since they supply a short-circuit or nominal current that increases proportionally to the cell surface.

Therefore, the invention has the objective of creating a protection circuit device for a solar module that assumes the functions of a bypass diode providing little lost power and presenting a simple structure and guaranteeing high reliability and long duration.

This objective is achieved according to the invention by the features of the main claim.

Since a controllable electrical switching element is provided which serves as a branch element, whose switching section can be connected in parallel to the plurality of solar cells and since a supply circuit supplies a control voltage for the control of the control electrode A shunt circuit is provided that can easily absorb the short-circuit current or the working point current of the shaded cells. The controllable branch element in its function is controlled by the supply voltage in such a way that little power is lost. Thanks to the disconnector also provided, the voltage applied in the normal service of the solar cells to the switching section of the switching element to the power circuit can be blocked, while in the case of shading, the disconnector switches the voltage applied to the section switching to the power circuit.

Thanks to the measures indicated in the dependent claims, advantageous variants and improvements are possible.

It is especially advantageous if the power circuit is made as a charging circuit for an energy accumulator or one is present, which increases the voltage available in the case of shading at a higher voltage for the control of the controllable bypass element. In this way, the available supply voltage can be used thanks to the switching section in the case of -0.6 V shading to control the controllable bypass element and, if necessary, supply other circuits.

It is advantageous that the controllable bypass element is realized as a MOS field effect transistor (MOSFET), and the existing body diode can be assumed inherently in the MOSFET for a short time completely the solar generator current, being able to be used in the case of small currents of solar generator of lasting form like diode of derivation.

Advantageously, the inherent capacity of the controllable bypass element, in the MOSFET used, the gate capacity, is used as an energy accumulator of the power circuit or of the load circuit, so that no additional accumulator components are needed.

The disconnector is particularly advantageously operated as a bipolar transistor that is operated in an inverse manner, since it is operated in the normal service in a conventional manner in a common collector circuit, thus being able to block drainage voltage without problems. 20V positive source that occurs in normal service.

It is advantageous to carry out the disconnector as a field effect transistor, preferably as a J-FET that conducts itself, since it has a low connection resistance, so that the next circuit is connected almost without losses to the section voltage switching of the bypass element, the drain-source voltage of the MOSFET.

The supply circuit and / or the load circuit advantageously presents a transformer with a positive reaction winding and a first electronic switching element, the switching element and the transformer exerting similarly to a blocking oscillator a process of tilt, in which the accumulated energy in the transformer is transmitted to the energy accumulator, eg the gate capacity. Thanks to this measure it is possible to generate from the reduced voltage in the case of shading of approx. 0.6 V a high voltage of approx. 15 V, being able to transfer the energy needed to load the gate capacity quickly, preferably in a single step.

The first electronic switching element is advantageously connected in an inverse manner, thus forming the disconnector while no additional components are necessary for separation.

Thanks to the fact that a first discharge circuit is provided, which is connected to the control electrode of the controllable bypass element, the time constant of the discharge circuit having been chosen in such a way that the driving time relation of the bypass element that of the non-conduction is large, preferably greater than 5, it is possible to control the controllable bypass element in such a way that reduced power losses are produced, thus reducing heat generation.

It is advantageous to perform the first discharge circuit as an active discharge circuit that does not act in a linear manner, which above a threshold voltage has a high impedance and below the threshold voltage a low impedance, depending on the threshold voltage of the electrode voltage control required for complete control of the bypass switching element. In this way the lost power that is produced inside the MOSFET can be further reduced.

It is especially advantageous to carry out the first discharge circuit with a J-FET that conducts itself, which in normal service connects the control electrode of the bypass switching element with a reference potential and thus prevents an unwanted connection of the element bypass switching and in the case of shading together with a diode, capacitor and discharge resistor network a timer element, which disconnects the bypass switching element periodically after a defined time. In this way, the control electrode of the bypass switching element can always be kept charged at an optimum value in the connected state, whereby the lost power is further reduced.

Examples of embodiment of the invention are shown in the drawing, which will be explained in more detail in the description set forth below. They show:

Figure 1 the wiring of solar cells and bypass diodes according to the state of the art, as well as the voltage of the diode in normal service and in case of shading;

Figure 2 a block diagram of the protection circuit device according to the invention;

Figure 3 a first circuit configuration of the protection circuit device according to the invention;

Figure 4 the development in time of the drain-source tension of the controllable bypass element;

Figure 5 the development in time of the gate-source voltage;

Figure 6 a second circuit-like configuration of the switching device according to the invention and

Figure 7 a third circuit configuration of the protection circuit device according to the invention;

Figure 8 a fourth circuit configuration of the invention and

Figure 9 the development in time of the gate-source voltage of the controllable bypass element and of the gate-source voltage of the J-FET driving by itself as well as the development in time of the drain voltage- source of controllable bypass element.

The protection circuit device shown in Figure 2 has as substantial components a field effect transistor MOS 1, which is part of a switching unit 30 which will be described in more detail below. The drain-source section as a switching section is located between the connections 11 and 12 that are connected with the serial connection of the solar cells of the solar module. In normal service, a positive voltage of 20 V is applied in the drain-source section, while in the case of shading there is a negative drain-source voltage of 0.6 V. The inherently existing body diode of the MOS-FET 1 is designated with 2.

A disconnector 40 is connected, on the one hand, with the drain connection of the MOSFET 1 and, on the other hand, with a power and / or load circuit 50 (hereinafter referred to as substantially load circuit), the disconnector must be blocked 40 in normal service the positive drain-source voltage of up to approx. 20 V, while in the case of shading, the reduced negative voltage drop of 0.6 V or less with the lowest possible losses must be transmitted to the load circuit 50 provided below.

The charging circuit 50 transforms the reduced negative continuous voltage available in the case of shading behind the switch 40 into a higher positive voltage, necessary for the control of the MOSFET 1 and / or for feeding other parts of the circuit. Concepts based on an intermediate accumulation of energy in a reactance coil or a transformer as well as load pumps that work capacitively can be used, and a preferable embodiment will be described below. The transformed voltage is accumulated in an intermediate manner in an energy accumulator 60, which is drawn here as a capacitor, taking advantage of the gate capacity of the MOSFET 1 directly as an energy accumulator in an especially advantageous manner.

The gate electrode G of the MOSFET 1 is sent as a function of time by means of a timer circuit 80, the MOSFET being controlled for the longest time of the cycle time completely to reduce the lost power, working, if necessary, linearly during a shorter time interval and being completely blocked for a short time interval. The bypass current of the MOSFET 1 flows in this case through the body diode 2. In the protection circuits according to Figures 3, 6 and 7, the gate capacity of the gate is discharged according to Figure 5 in the first two time intervals. MOSFET while at the end of the third time interval it is recharged by the charging circuit. In the protection circuit according to Figure 8, the discharge is performed according to Figure 9 only in time intervals 2 and 3; At the end of the fourth time interval, the capacity is reloaded by the charging circuit.

Preferably, a comparator 70 is provided, which monitors the drain-source voltage and which emits in the admissible state a signal to a logic circuit 90, which also receives the signal from the timer circuit. The monitoring criteria of the comparator circuit 70 are, for example, the polarity as well as the value of the drain-source voltage of the MOSFET 1. An excitation circuit 100, which is connected just like the other circuits with the power circuit or load 50 sends the MOSFET 1 gate according to the logic circuit signal.

The functional blocks represented in Figure 2 are represented to improve clarity; in the other embodiments it can be seen that it is not mandatory that all functional blocks must be arranged separately; It is also possible to gather several functions provided by the blocks in a component.

A first embodiment of the protection circuit device according to the invention with discrete components is shown in Figure 3, the functional blocks being represented in part with broken lines. The switching unit 30 has, as already explained above, the MOSFET 1 with the body diode 2, as well as an inherently existing gate capacity 3. A first Zener diode 7 is connected by the reference potential line connected to the connection 12 in the conduction direction with the gate connection. It is used to limit the gate voltage to an allowable value of eg 15 V. Between the reference potential 32 and the gate pilot line 31 a transistor 9 is connected to its switching section, whose base is connected by a resistor high impedance 10 with the drain connection of the MOSFET 1. In parallel to the switching section of the transistor 9 another capacitor 8 is connected and between the capacitor 8 and the first Zener diode 7 an interleaved resistor 6 is connected in the pilot line 31 A diode 13 and a second Zener diode 14 are arranged between the drain connection and the gate pilot line 31.

In parallel to the inherently existing body 2 diode of the MOSFET 1, another diode 4 can be connected, which conducts a part of the bypass current or also the entire bypass current when the MOSFET 1 is not connected.

A surge protector 5, eg a varistor or a TransZorb diode, is connected in parallel to the MOSFET 1 and limits extremely high voltage pulses of short duration.

With this protection circuit, the MOSFET with the inherently existing body diode 2 is protected from too high voltages in the drain-source section and the gate-source section. In addition, when switching to normal service, that is, when there is a positive drain-source voltage, a rapid disconnection is necessary and, in addition, an unwanted connection of the MOSFET in the normal service must be prevented.

In case of a positive drain-source voltage, that is, when switching to normal service, the transistor 9 is completely controlled by the interleaved resistor 10 of high impedance and discharges the gate capacity 3 of the MOSFET 1 very quickly by the resistor interleaved 6 of low impedance (positive reaction). In addition, transistor 9 maintains the gate-source voltage via the interleaved resistor 6 in normal service at almost 0

V. In this way, an unwanted connection is reliably prevented, eg by a gate voltage induced from the outside. The leakage current that exits the normal service through the base interleaved resistor 10 is negligibly reduced in case of a corresponding dimensioning.

At first. MOSFETs have limited avalanche resistance, that is, if the maximum permissible drain-source voltage is exceeded for a short time, eg exceeding 60 V in case of a specified MOSFET for 40 V, the MOSFET will It becomes a conductor and limits the tension tip without damage. However, in this service mode the permissible working range can be abandoned and the component may be subject to more stress. Therefore, in case of excessive voltage, the MOSFET is sent by the Zener diode 14 and the diode 13 selectively through its gate-source section, the gate rising to a positive potential when the Zener diode is exceeded 14 the Zener voltage and the MOSFET 1 being operated in a linear fashion. In order to establish a positive gate voltage when transistor 9 is conductive, an interleaved resistor 6 is needed.

The capacitor 8 connected by the interleaved resistor 6 in parallel to the gate capacity 3, which typically has a capacity greater than that of the gate capacity 3, reduces the susceptibility to circuit interference. The capacitor is advantageously connected on the side not facing the gate of the interleaved resistor 6, since thanks to this, in case of a transient overvoltage, only the gate capacity 3 comparatively low must be charged by means of the Zener diode 14 and diode 13 .

As explained above, the switch 40 has the function of separating the positive drain-source voltage of 20 V in the normal service from the circuit connected below and transmitting the negative drain-source voltage of 0.6 V in the case shading with little loss to the circuit components arranged below. The disconnector 40 shown in Figure 3 presents a n-channel junction field effect transmitter 28 (J-FET) that conducts itself, whose source electrode is connected to the drain connection of the MOSFET 1, whose electrode The drain is connected to the supply and load circuit 50 arranged below and whose gate electrode is connected by a high resistance gate resistance 29 with the reference potential line 32. This resistor 29 limits the current through the diodes of gate in case of a gate-drain or positive gate-source voltage greater than 0.5 V, as occurs in the case of shading. For blocking, the low impedance J-FET 28 requires a negative gate voltage of approx. 5 V both with respect to drainage and with respect to the source. This is achieved in normal service directly for the source-gate section. For the drain-gate section, on the contrary, this can only be achieved if the drainage potential adopts a positive value. For this, it is necessary that the supply and load circuit 50 arranged below can absorb a blocking voltage of a value similar to the threshold voltage of the J-FET, that is, approximately 5 V. This special property is guaranteed by the charging circuit 50 described below.

Instead of the J-FET 28 described, a self-driving MOSFET can also be used, which can have a similar behavior, although in this case a current limitation by the resistor 29 is not necessary, since the isolation of the gate can typically absorb + 20 V.

The power and / or load circuit 50 has the function of transforming a negative input voltage of 0.6 V into a positive output voltage sufficient for the MOSFET 1 control, eg 15 V. Taking into account the voltage drop that is reduced as the temperature increases through the body diode 2 of the MOSFET 1, as well as eventual voltage drops that occur in the switch 40, a safe start must be guaranteed already at tensions even below 0.4 V. In addition, the charging circuit must be robust and can be manufactured with minimal costs. In addition, it additionally assumes the functions of comparator 70, as well as in part of the timer circuits and excitation circuits 80, 100 of Figure 2.

The charging circuit 50 according to Figure 3 has a transistor 24 that operates in a common emitter circuit, whose emitter is connected to the drain connection of J-FET 28 and whose collector is connected to the primary winding 21 of a transformer 20. The base of the transistor 24 is connected by an interleaved resistor 25 with a positive reaction winding 22. An output winding 21 'is connected in series with the primary winding 21, whereby the transformer 20 is connected as an autotransformer. The collector of transistor 24 is connected between the primary winding 21 and the output winding 21 ’. The output winding 21 ’is connected by a rectifier diode 23 and the interleaved resistor 6 with the gate capacity 3 directly with the supplementary capacitor 8. Another diode 23’ connects the end of the primary winding with the supplementary capacitor 8.

In addition, the charging circuit 50 has a transistor 26, whose emitter is connected to the drain connection of the J-FET 28, whose collector is connected between the diode 3 and the interleaved resistor 6 and whose base is connected by an interleaved resistor 28 with the connection of the positive reaction winding 22.

A discharge resistor 81, which can be part of a timer circuit 80 ’, is connected between the reference potential line 32 and the gate pilot line 31.

The mode of operation, in particular of the power or load circuit, as well as the switching behavior of the MOSFET 1, will be described with reference to the developments of the voltage as a function of time according to Figures 4 and 5. In case of shading With the MOS-FET 1 connected, a negative voltage of a few millivolts falls, for example, -30 mV, in the drain-source section, depending on the connection resistance (RDSon) of the MOSFET 1 and the generator current momentary solar. This is indicated in Figure 4 with the interval (1). Since in this case the voltage supplied through the disconnector 40 is not sufficient, the supply circuit 50 is correspondingly not active either. The discharge resistor 81 slowly discharges, eg in 100 ms (interval (1)), the gate capacity 3 of MOSFET 1, which according to Figure 4 was charged, eg, to 15 V. When the threshold voltage of MOSFET 1 is reached, eg with a gate-source voltage of 5 V, it it passes from the fully controlled interval to the linear interval (interval (2)) and the drain-source voltage increases slowly according to Figure 4. Without the recharge described below of the source-gate capacity 3 via the load circuit 50, the MOSFET 1 would enter the completely blocked state, in this case the current of the solar generator flowing completely through the body diode 2, which is linked to a negative voltage drop of approx. 0.4 V at approx. 1 V.

With a tension of approx. 0.3 V to 0.4 V between the line 34 and the reference potential line 32, that is, from the drain connection of the disconnector 40, in the transistor 24 flows a sufficiently large base current to cause a collector current remarkable and, therefore, current in the primary winding 21 of the transformer 20. In this way a voltage is induced in the positive reaction winding 22 which, thanks to the winding direction, is added reaching the voltage between lines 32 and 34 therefore reinforcing the base current, so a tilt process begins. The transistor 24 is connected directly and according to the inductance of the primary winding 21 and the voltage applied to the primary winding, which substantially corresponds to the voltage applied between the lines 32, 34, a primary current is established that increases over time.

When the core of the transformer 20 reaches saturation or when the base current of transistor 24 is no longer sufficient for complete control, the positive reaction is reversed and transistor 24 is abruptly blocked. The energy accumulated in the transformer inductance is transmitted by the primary winding 21, as well as the output winding 21 'and the rectifying diode 23 to the gate capacity 3, as well as to the supplementary capacitor 8. This can be seen at the end of the interval (3) or at the beginning of the interval (1) of Figures 4 and 5. The MOSFET 1 is connected accordingly and has, as described, according to its internal resistance and only a negative voltage drop of a few millivolts. Load circuit 50 is no longer powered with sufficient voltage and is not active. The transformer 20 is sized in such a way that the energy accumulated in it is sufficient to charge the gate capacity 3 or the capacitor 8 with a single transformation step to the theoretical value of eg 15 V.

In a real transformer, the inevitable dispersion inductance of the winding of the transformer 21 leads to an overvoltage tip in transistor 24 when transistor 24 is quickly disconnected, which can lead to damage therein. Diode 23 ’prevents this tip, letting the current flowing at the moment of disconnection in the winding of the transformer flow to the capacitor not charged at this time.

It is again indicated that "step" always refers to the load circuit 50, while the concept "cycle" always refers to the circuit as a whole. The loading step is formed by two phases: The first phase has been described above and begins and is maintained during the time interval (3) of the total cycle. The tilt process itself only lasts a few µs; the substantial part of the time is occupied by the "slow" increase in the current until the end of the interval (3). Then the second phase of the step begins, in which the energy is transmitted from the transformer to the capacities. This process takes place on the falling edge, that is, partly in the interval (3) and in the interval (1) of the following cycle. However, this whole recharge process lasts only a few µs.

As can be seen from the operating mode described above, transistor 24 assumes with its base-emitter section in addition to the switching function also the function of comparator 70 of Figure 2, that is, it only works when the drain-source voltage applied It is big enough. Therefore, it is advantageous for transistor 24 to be thermally coupled to MOSFET 1. Since the two components are based on silicon technology, the voltages in conduction state of the body diode and also of the base-emitting diode vary in the same sense, so that safe operation of the circuit at all temperatures is guaranteed.

When the negative drain-source voltage of the MOSFET or the voltage supplied to the load circuit 50 is not large enough, eg due to the internal resistance of the switch 40, the tilting process or the transformation step described above, which takes place in the interval (3), it does not necessarily develop completely. Therefore, the gate capacity 3 of the MOSFET 1 or the capacitor 8 may not be fully charged, in particular in the case of small currents from the solar generator.

To further guarantee a stable service of the protection circuit device, at the beginning of the tilting process, the MOSFET gate 1 is discharged very quickly through the connected transistor 26, as can be seen in Figure 5, interval (3). MOSFET 1 momentarily blocks and the drain-source voltage increases according to Figure 4 quickly of approx. -0.4 V, the threshold value of the tilting process, at approx. -0.6 V, the voltage in the conduction state of the body diode 2. Therefore, thanks to transistor 26 a supplementary positive reaction is generated. In the second phase of the transformation step, the transistor 26 is completely blocked by the voltage at this negative moment in the positive reaction winding 22, so that the gate capacity 3 or the capacitor 8 can be charged.

The total cycle of the circuit according to Figure 3 is formed according to Figures 4 and 5 by a first long phase (100 ms), in which the MOSFET 1 is completely controlled, a second shorter phase (20 ms), in the which reaches the linear zone and the drain-source tension rises slowly to approx. -0.4 V, and a third short phase, in which it is completely disconnected by the positive reaction circuit for a short time (eg 1 ms). However, the amount of heat that is generated in the second and third phases is no problem and can be dissipated in a conventional manner.

As explained several times, in the normal service of the module, the drain-source voltage of the MOSFET rises to positive values of approx. 15 V at approx. 20 V. To block the J-FET 28 used in disconnector 40, both its drain connection and its source connection approx. 5 V with respect to the gate connection; if this is not the case, an inadmissible leakage current would flow in the load circuit 50. Since in the circuit according to Figure 3, the emitter-base sections of transistors 24 and 26 for positive voltages on line 34 They are arranged in the blocking direction, and can also absorb a blocking voltage of up to approx. 5V, can

raise the drainage potential of the J-FET 28 to 5 V and the J-FET 28 can completely block, as required.

Another exemplary embodiment is shown in Figure 6, which achieves a simplification of the circuit represented in Figure 3, because the functions of the disconnector 40 and the transistor 24 of the supply or load circuit 50 are combined. Otherwise, the circuit corresponds to the circuit according to Figure 3 and the voltage diagrams according to Figure 4 and Figure 5 are also applicable.

As can be seen, transistor 24 is operated in reverse. When the emitter and the collector are exchanged in a bipolar transistor, the main transistor properties are maintained; however, in the reverse service the amplification of the current is reduced approximately corresponding to a factor of 30. This property is taken into account with a base interleaved resistor 25 of a correspondingly low impedance. In practice, for the current limitation, the ohmic resistance of the positive reaction winding 22 is sufficient, so it is not necessary to use a concentrated component 25. The reverse service of transistor 24 has the great advantage that in the normal service of the solar module it is operated in a common collector circuit, its base and also the emitter being connected as a continuous voltage to the reference potential

32. In this operating mode, the transistor can easily absorb the voltage that is produced from 20 V, it is also possible to use a type of stable voltage transistor, which better resists possible overvoltage pulses. An oscillation of the supply or load circuit is excluded by the positive reaction winding 22 which in this case acts as feedback.

Transistor 26 continues to operate in conventional service and its function corresponds to that of Figure 3. However, its emitter is connected to the emitter of transistor 24. Therefore, in the connected state of transistor 24, the MOSFET gate 1 it can be quickly discharged through transistor 26, since it is no longer necessary to absorb negative blocking voltages in this mode of connection in the conduction phase of MOSFET 1 or in the normal service of the module.

As described above, in the circuits according to Figure 3 and Figure 6, the energy required for charging the gate capacity 3 or the capacitor 8 is transmitted in a single step, that is, in a single tilt process. of transformer 20 and transistor. However, the charging circuit can also transmit the energy in several steps, charging the gate capacity of the MOSFET 1 or a multi-step energy accumulator, then disconnecting.

Finally, the aforementioned incomplete charging process of the gate or capacitor capacity 8 can also be constituted as a principle by a corresponding dimensioning, eg of the base interleaved resistor 25, to achieve a continuously linear service of the MOSFET 1. In this service mode, transistor 24 serves as a regulator for drain-source voltage. MOSFET 1 is not fully controlled but is maintained in linear service by transistor 24 as a regulator. Therefore, in the case of shading a negative voltage of approx. 0.3 V to 0.4 V in the drain-source section, which is enough to continuously operate the power or load circuit 50. In this concept, the losses inside the MOSFET 1 are greater than in the case of a fully switched MOSFET. However, it is advantageous that with this MOSFET that works in a linear way, there are no jumps in the solar generator voltage or the solar generator current.

To further reduce the lost power that is produced inside the MOSFET 1, the transitory service in the linear area of the MOSFET can be prevented according to the interval (2) in Figure 4 and in Figure 5. A circuit of this type is shown in Figure 7, which is distinguished from the circuit according to Figure 3 or Figure 6 by the discharge circuit designated with 80 ". In the circuits according to Figure 3 and Figure 6, the moment of disconnection of the MOSFET 1 depends on the timer element formed by its gate capacity 3, the possibly existing capacitor 8, as well as the discharge resistor 81. Instead of the resistor of discharge 81 an active gate discharge circuit is used that does not act linearly. This has the property of having a high impedance above a certain threshold voltage, on the contrary being of a clearly lower impedance when the value falls below the threshold voltage. A circuit with this property can be made, for example, by a Schmitt trigger circuit. When the switching point of this trigger circuit, that is, the tilt threshold of the gate discharge circuit 80 ", is higher than the maximum gate voltage necessary for complete control of the MOSFET 1, eg it is of 6 V or higher, it will first lower slowly after a load on the load circuit 50 to quickly lower again when it is below the trip or tilt threshold by initiating a new charging step. With such a circuit, the service of the MOSFET 1 in the linear interval is avoided, which is designated in Figure 4 and in Figure 5 with the interval (2), and the lost power is reduced again.

With this circuit 80 "a weak signal MOSFET 87 is connected between the gate pilot line 31 and the reference potential line 32, whose gate connection is connected to the collector of a transistor 83, whose emitter is connected again to the potential reference 32. The base connection is connected to a voltage divider 84, 85 between the gate pilot line 31 and the reference potential line 32. Finally, a resistor 86 is connected between line 31 and the gate connection of the MOSFET 87. From the collector connection

5

fifteen

25

35

Four. Five

of transistor 83, a capacitor 88 is connected to the positive reaction winding 22.

In case of high gate voltages of MOSFET 1, transistor 83 is completely controlled by voltage divider 84, 85. Its collector potential and, therefore, also the gate potential of MOSFET 87 are therefore close to reference potential 32, so the MOSFET 87 is blocked.

The gate capacity 3 of the MOSFET 1, as well as the capacitor 8, are slowly discharged by the high impedance resistors 84, 85 and 86. When the gate voltage of the MOSFET 1 falls below a minimum value, transistor 83 begins to be blocked and the gate voltage of the MOSFET 1 rises. When the threshold voltage of eg approx. 1… 2 V, when it is a weak signal MOSFET 87, the drain-source section changes to a low impedance and the gate capacity 3 or the capacitor 8 is quickly discharged. In this way the base current for transistor 83 continues to drop and a tilt process begins. This tilting process is favored because, from a certain drain-source voltage of the MOSFET 1, the power or load circuit 50 starts in the manner described above. In the first part of the step, the voltage in the positive reaction winding 22 is raised to positive values. This increase is transmitted through the coupling capacitor 88 to the MOSFET gate 87, so that the positive reaction process is reinforced again with the capacity of gate 3 or the capacitor 8 completely discharged. In this way it also blocks very Quickly completely MOSFET 1.

Due to the supplementary positive reaction by the capacitor 88, the positive reaction shunt shown in Figure 6 through transistor 26 and interleaved resistor 27 can be suppressed.

In the second phase of the charging step, the MOSFET 87 is completely blocked in the positive reaction winding by the negative voltage jump transmitted by the capacitor 88, so that the gate capacity 3 or the capacitor 8 can be recharged . Figure 8 shows another especially advantageous embodiment of the protection circuit. It corresponds substantially to the circuit according to Figure 6, the transistor being suppressed as well as the interleaved resistor 10 and the passive discharge circuit 80 ’being replaced by an active discharge circuit 80’.

The central point of the active 80 ”’ discharge circuit is the J-FET 81 ’that drives itself. On the one hand, replace the transistor 9 with the interleaved resistor 10, connecting the MOSFET gate 1 in the normal operation of the solar module by means of the interleaved resistor 6 and the windings 21 'and 21 of the transformer with the reference potential conductor 32. In this way, an unwanted connection of the MOSFET 1 is surely prevented by gate voltages induced from the outside or also leakage currents of diodes 13 and 14. On the other hand, it allows an optimal control of the MOSFET 1 according to Figure 9, which leads to another reduction of the lost power in the bypass switching element.

In contrast to the circuits described above, in the circuit according to Figure 8, the MOSFET 1 gate is not discharged after the loading process by a resistor, but the UGS gate voltage maintains its value throughout the time interval 1 full. Thus, the MOSFET has a very low impedance during this time interval, whereby the lost power is correspondingly reduced. The moment of disconnection of the MOSFET 1 depends on a time constant of the timer element formed by the capacitor 82 ’and the resistance 84’. In the charging phase of the capacitors 8 and 3 at the end of the time interval 4 the capacitor 82 'is also charged by the diode 83' reaching the sum of the voltages in the three windings 21, 21 'and 22, in this example at 17.5 V. When after the demagnetization of the transformer 20 the voltage of the windings 21 and 21 'changes again to zero, the potential in the gate of the J-FET 81' changes to a value of -17.5 V Therefore, the J-FET is completely blocked and, in the ideal case, no charge can be generated from the capacitors 8 and 3. The capacitor 82 'is slowly discharged, eg, in 100 ms, by the resistor 84' . When the gate voltage of J-FET 81 'reaches its threshold voltage (in this example - 2 V), the J-FET becomes low impedance and discharges capacitors 8 and 3 via windings 21' and 21 , so that the UGS gate voltage of the MOSFET 1 falls very quickly, which is represented in Figure 9 in the time interval

2. When this voltage falls below the threshold voltage of MOSFET 1, it begins to block and its drain-source voltage UDS rises rapidly according to Figure 9, interval 3. When a value of approx. -0.4 V, the tilt process of the charging circuit 50 begins, as described in relation to the circuits described so far, which is linked to a very rapid continuation of the discharge of the capacitors 8 and 3 by the transistor

26. The interval 4 follows, in which the transistor 24 is completely conductive and energy is accumulated in the transformer 20. At the end of this interval the new charge of the capacitors 8 and 3, as well as 82 ’, is carried out.

Since MOSFET 1 is fully controlled for most of the cycle time and since the time interval in the blocking state represents less than 1% of the cycle time, the power lost in the circuit is reduced again according to the Figure 8 compared to the other circuits.

Of course, all the described circuits can be formed with complementary semiconductor types.

In addition to the function as a low loss bypass element, the MOSFET 1 can also assume as an additional function a short-circuit of the solar generator voltage during installation, in the case of an inspection or in the event of a fire. For this purpose, for example, through a pilot line, the gate connections of all MOSFETs in a solar generator with a control voltage are requested, so that it is set to

5 short-circuit the voltage of each individual module. In this way a safe contact of the active parts and of the solar generator lines is possible.

10

Claims (24)

1.-Protection circuit device for a solar module, in which a plurality of solar cells that work partly in normal service and at the same time partly in case of shading are connected in series, with at least one switching element (1) controllable electrical that serves as a branch element, whose switching section can be connected in parallel to the plurality of solar cells, with a power circuit (50) to supply a control voltage for the control of the element control electrode bypass (1), characterized by a disconnector (40) to block the voltage applied in the normal service to the switching section of the branch element to the supply circuit (50) and to switch the voltage applied to the switching section in case of shading of at least one solar cell to the power circuit (50). 2.-Protection circuit device according to claim 1, characterized in that the power circuit is made as a charging circuit (50) for an energy accumulator (3, 8, 60), which converts an available voltage into the case of shading at a higher voltage for the control of the controllable bypass element. 3.-Protection circuit device according to claim 1 or 2, characterized in that the branch element (1) Controllable is performed as an MOS field effect transistor. 4. Protection circuit device according to claim 2 or 3, characterized in that the energy accumulator is made as a capacitor (8) and / or as an inherent capacity (3) of the controllable bypass element (1). 5. Protection circuit device according to one of claims 1 to 4, characterized in that the disconnector (40) is performed as a field effect transistor, preferably as J-FET or MOSFET. 6. Protection circuit device according to one of claims 1 to 4, characterized in that the disconnector is made as a bipolar transistor that is operated in reverse. 7. Protection circuit device according to one of claims 1 to 6, characterized in that a timer circuit (80) is provided, which defines a cycle time, during which the controllable branch element (1) is fully connected during a first time interval and completely blocked during a second time interval, the energy accumulator (3, 8, 60) being charged during the second time interval. 8. Protection circuit device according to claim 7, characterized in that the time cycle has a third time interval between the first and the second time interval, in which the branch element (1) Controllable is operated in a linear state. 9.-Protection circuit device according to one of claims 1 to 6, characterized in that the power or load circuit (50) has a regulation circuit (24) with which the controllable bypass element can be operated continuously in the linear state. 10.-Protection circuit device according to one of claims 1 to 9, characterized in that, in order to generate the voltage necessary for the control of the controllable bypass element (1), the supply or load circuit (50) has a transformer or at least one coil or at least one capacitor for intermediate energy accumulation to increase the available voltage in case of disconnection. 11. Protection circuit device according to one of claims 1 to 10, characterized in that, in order to generate the voltage necessary for the control of the controllable bypass element (1), the supply or load circuit (50) has a pump of load to increase the available voltage in case of disconnection. 12. Protection circuit device according to one of claims 1 to 10, characterized in that the power circuit (50) has a transformer (20) with a positive reaction winding (22) and a first switching element (24) electronic, the switching element and the transformer (20) exerting a tilt process similar to a blocking oscillator, during which the energy accumulated in the transformer (20) is transferred to the energy accumulator (3, 8, 60). 13.-Protection circuit device according to claim 12, characterized in that the first electronic switching element (24) is operated in an inverse manner while forming the disconnector (40). 14. Protection circuit device according to claim 12 or 13, characterized in that a supplementary output winding (21 ’) is connected in series with the primary winding (21) as an autotransformer. 15. Protection circuit device according to one of claims 12 to 14, characterized in that the switching section of the first switching element (24) is connected in series with the primary winding (21) and the positive reaction winding (22 ) is connected to the control electrode of the first switching element (24). 16.-Protection circuit device according to one of claims 1 to 15, characterized in that the control electrode of the controllable branch element (1) is connected to a first discharge circuit (80 ', 80 ", 80"') , the time constant of the first discharge circuit having been chosen such that the ratio of the conduction time of the branch element (1) to the non-conduction time is large, preferably> 5. 17. Protection circuit device according to claim 16, characterized in that the first discharge circuit has a resistor (81) connected in parallel to the inherent capacity (3) of the branch element

(one)

and, if necessary, to a capacitor (8) connected in parallel to this inherent capacity.

18.-Protection circuit device according to one of claims 12 to 17, characterized in that the power circuit (50) has a rapid discharge circuit (26), which rapidly discharges the inherent capacity

(3)

and, if necessary, the supplementary capacitor (8) connected in parallel at the beginning of the tilting process.

19.-Protection circuit device according to claim 18, characterized in that the rapid discharge circuit has a second electronic switching element (26), whose control electrode is connected to the positive reaction winding and whose switching section is connected , starting from the connection of the control electrode of the bypass switching element (1), in parallel to the switching section of the first electronic switching element (24) or in series with it. 20.-Protection circuit device according to claim 16, characterized in that the first discharge circuit (80 ") is made as an active discharge circuit that does not act linearly, which above a threshold voltage has a high impedance and Below the threshold voltage it has a low impedance, depending on the threshold voltage of the voltage necessary for complete control of the bypass switching element (1) in its control electrode. 21.-Protection circuit device according to claim 20, characterized in that the first discharge circuit (80 ") is made as a Schmitt trigger circuit. 22.-Protection circuit device according to claim 16, characterized in that the first discharge circuit (80 "') has a J-FET that conducts itself and a diode network (83'), capacitor (82 ') and discharge resistor (83 '), which form a timer element for periodic disconnection of the bypass switching element after a defined time. 23.-Protection circuit device according to one of claims 1 to 22, characterized in that the controllable bypass switching element is assigned a protection circuit (30) against overvoltage, as well as against an unwanted connection. 24.-Protection circuit device according to one of claims 1 to 23, characterized in that for the short-circuiting of the solar module for inspection purposes or in case of fire, the control electrodes of the branch elements apply a voltage such that the branch elements are switched to conduction mode.