Electrical device, electrical appliance and method for operating an electrical device

Abstract

In order to increase efficiency, the invention proposes an electrical device (10), having at least one insulated gate driver (12) for controlling at least one gate electrode (32), wherein the gate driver (12) has: at least one transformer (14) for transferring a driver signal, generated via a modulation of a carrier signal, from a primary side (20) to a secondary side (30) of the gate driver (12); a rectifying unit (34) on the secondary side (30); and a latch unit (36) for discharging the gate electrode (32), the latch unit (36) being connected between the gate electrode (32) and the rectifying unit (34).

Description

[0001] Electrical device, electrical appliance and method for operating an electrical device

[0002] The invention relates to an electrical device according to claim 1, an electrical appliance according to claim 11 and a method for operating an electrical device according to claim 12.

[0003] Gate drivers for controlling the gate electrode of a semiconductor switch are already known in the art, but these lack a rectifier unit on a secondary side and / or a latch unit. For example, US 11264985 B1 discloses a transformer-isolated gate driver, which, however, features single-path control without modulation of the carrier signal, thus requiring a bulky transformer. Such designs are also known from: C. Jiang, H. Peng, O. Yue, and Q. Tong, 'Study on the Impacts of Signal Carrier in a Compact Gate Driver with Single Isolation Channel for Both Signal and Power Transferring', in 2022 IEEE Energy Conversion Congress and Exposition (ECCE), Oct. 2022, pp. 1-7. doi: 10.1109 / ECCE50734.2022.9947991, and, for example, from WO 2022096122 A1. WO 2024056532 A1 shows a bus discharge unit for discharging a bus capacitor of an induction cooktop.

[0004] The object of the invention is, in particular but not limited to, providing a generic device with improved efficiency characteristics. This object is achieved according to the invention by the features of claim 1, while advantageous embodiments and further developments of the invention can be found in the dependent claims.

[0005] An electrical device is proposed comprising at least one isolated gate driver for controlling at least one gate electrode. The gate driver generates at least one transformer for transferring a driver signal via modulation of a carrier signal from a primary to a secondary side of the gate driver. It includes a rectifier on the secondary side and a latch unit for discharging the gate electrode, the latch unit being connected between the gate electrode and the rectifier. Such a design allows for advantageous efficiency, particularly space efficiency of the gate driver, efficiency with respect to the switching characteristics of a switch comprising the gate electrode, cost efficiency, and / or efficiency with respect to the power supply of the gate driver.Advantageously, generating the driver signal by modulating the carrier signal, particularly with a lower-frequency signal compared to the carrier signal, can increase driver information, space efficiency, and / or cost efficiency of the transformer, especially since its dimensions for transmitting the high-frequency driver signal generated by the modulation can be advantageously reduced. In particular, the driver information can be advantageously restored on the secondary side by means of the rectification unit, and the driver signal received on the secondary side can be amplified. Furthermore, the latching unit can provide a particularly fast discharge of the gate electrode, thereby enabling a particularly safe and / or efficient switching operation of a switch with a gate electrode.In contrast to simply including high resistances in the gate driver to increase discharge efficiency, which would slow down the charging of the gate electrode, the latch unit can advantageously provide fast discharge with particularly high efficiency and / or charging speed. Furthermore, an isolated power supply referenced to a live conductor and / or neutral conductor in a circuit containing the switch is not required to operate the gate driver. Advantageously, the gate driver can be powered independently of a mains voltage.

[0006] The electrical device is, in particular, a device with a function based on an electric current, which in particular comprises various electrical and / or electronic components. The electrical device, in particular, has at least one circuit or is configured as such. Furthermore, the electrical device may have additional components, for example, at least one housing for receiving at least the circuit. Preferably, the electrical device is configured at least as a part, in particular as a subassembly, of an electrical appliance. It would be conceivable for the electrical device to comprise the entire electrical appliance. The electrical device is preferably configured as a household appliance, more preferably as a cooktop appliance, and most preferably as an induction cooktop appliance.The terms “household appliance device”, “cooking hob device” and “induction cooking hob device” shall in particular be understood to mean at least a part, in particular a sub-assembly, of an electrical appliance designed as a household appliance, a cooking hob and an induction cooking hob, respectively.Alternatively, the electrical device can be at least part of any differently designed electrical appliance that would appear sensible to a person skilled in the art, in particular an electrical appliance that differs from a household appliance or a household appliance that differs from a cooktop, for example, a different type of cooking appliance, in particular an oven, microwave, grill, steam cooker, or the like, or, for example, a chest freezer, in particular a refrigerator and / or freezer, or a household cleaning appliance, for example, a dishwasher and / or washing machine and / or dryer, or an air conditioner, or the like. The electrical device can, in particular, be at least part of any electrical appliance that would appear sensible to a person skilled in the art, comprising at least one switch and a gate electrode that can be controlled by means of the gate driver.The gate driver is preferably designed to control the at least one switch. The switch is specifically configured as a semiconductor switch, preferably a transistor, and more preferably a MOSFET switch. Alternatively, the switch can be configured as another type of switch that would be suitable to a person skilled in the art, particularly a semiconductor switch, for example, a bipolar transistor with an insulated gate electrode (IGBT), a thyristor, or the like. The electrical device preferably includes the at least one gate electrode, and in particular at least one gate capacitor, for example, with a total capacitance of at least 1 nF and / or a maximum of 10 nF. Alternatively, other values ​​that would be suitable to a person skilled in the art are conceivable. The electrical device can include the at least one switch.The switch is specifically enabled for a charged state of the gate electrode and specifically disabled for a discharged state of the gate electrode. An enabled state of the switch is understood to mean, in particular, a conducting state, especially one that allows current to flow between the source and the outlet or between the collector and emitter of the switch. The same applies, conversely, to the disabled state. The switch is preferably configured as a high-side switch. The gate driver is preferably configured as a high-side gate driver. Alternatively, it would be conceivable for the switch to be configured as a low-side switch.

[0007] The isolated gate driver is, in particular, galvanically isolated, especially transformer-isolated. The isolated gate driver is, in particular, magnetically isolated. The transformer is provided, in particular, for at least a data transfer and, in particular, for an energy transfer from the primary side to the secondary side of the gate driver during the transfer of the driver signal. The primary side and the secondary side are preferably, in particular, only connected via the transformer. The transformer preferably has at least one primary coil and at least one secondary coil for the transfer. Preferably, the primary side has the primary coil and, in particular, a portion of the gate driver electrically, in particular by means of wiring, connected to the primary coil.The secondary side preferably comprises the secondary coil and, in particular, a portion of the gate driver electrically connected to the secondary coil, especially by means of a wire. The primary side of the gate driver is specifically designed for generating the driver signal, particularly by modulating the carrier signal. The driver signal is preferably a digitally modulated carrier signal, preferably by means of amplitude-shift keying (ASK), based on the driver information. Alternatively or additionally, modulation by means of phase-shift keying (PSK) and / or frequency-shift keying (FSK) is conceivable for generating the driver signal. The driver information specifies, in particular, a charging time interval and a discharging time interval of the gate electrode, specifically an activation time interval and a deactivation time interval of the switch. The driver information also specifies, in particular, a switching characteristic of the switch.The carrier signal is preferably formed from a modulation of the carrier signal with a signal containing the driver information to be transmitted. The signal preferably contains the driver information in the form of voltage pulses and / or at least one voltage pulse. Alternatively, the driver information is preferably contained in rectangular pulses and / or at least one rectangular pulse, although another pulse shape that would be considered useful by a person skilled in the art would be conceivable. Preferably, the driver signal has an envelope, in particular in the form of at least one voltage pulse and / or voltage pulse containing the driver information.Preferably, the period of the carrier signal is smaller, for example by a factor of at least 50, preferably at least 100, preferably at least 200, and particularly preferably at least 250, than the pulse duration of the signal modulated onto the carrier signal to generate the driver signal. The driver signal contains the driver information to be transmitted and / or the pulse duration of the envelope of the driver signal. The pulse duration of the signal containing the driver information and / or the pulse duration of the driver signal, in particular the envelope of the driver signal, is preferably at least 1 ms, preferably at least 2 ms, particularly preferably at least 3 ms, and particularly advantageously at least 4.1 ms and / or preferably a maximum of 20 ms, preferably a maximum of 10 ms, particularly preferably a maximum of 8 ms, and particularly advantageously a maximum of 5 ms. The signal can, for example, have a repetition period of at least 16 ms and / or a maximum of 20 ms.Alternatively, depending on the application of the switch and the corresponding desired switching frequency, other longer or shorter pulse durations and / or repetition periods that appear sensible to a person skilled in the art are conceivable. The signal containing the carrier information preferably has a low frequency. The carrier signal is preferably a high-frequency signal, in particular with a frequency of at least 9 kHz, preferably at least 50 kHz, advantageously at least 100 kHz, preferably at least 200 kHz, particularly preferably at least 300 kHz, and particularly advantageously at least 450 kHz. By way of example, the carrier signal can have a frequency of at least substantially 500 kHz, wherein in particular the deviation of the frequency from 500 kHz is less than 25%, preferably less than 10%, and particularly preferably less than 5% of 500 kHz. In particular, signal transmission at the transformer can be provided with particular efficiency.Advantageously, the transformer, in particular at least the primary and secondary coils, and thus especially the isolated gate driver, can be designed to be particularly compact and / or achieve particularly high temporal precision of the signal transmitted by the transformer. In particular, space efficiency and / or transmission efficiency can be improved. Advantageously, pulse distortion can be reduced and particularly high temperature stability of the isolated gate driver can be achieved by means of the transformer. The transformer can...

[0008] The transformer must include a common-mode choke (CMC) and, in particular, a primary-to-secondary winding ratio of 1:1. The transformer can, for example, be based on a commercially available transformer and, in particular, must have the necessary clearances and creepage distances for effective network insulation. The gate driver is preferably designed as a direct gate driver based on a magnetically isolated DC-DC converter, for example, a 2 W, 24 V-24 V converter. Alternatively, other power and voltage values ​​and / or transformer configurations that appear sensible to those skilled in the art are conceivable. The electrical device, in particular the gate driver, preferably has at least one modulation unit on the primary side for generating the driver signal, which is provided, in particular, for digital keying and frequency up-conversion to generate the driver signal.The primary side can, for example, include a circuit based on a complementary totem pole output and / or a totem pole output which is controlled in particular by several level-shifting MOSFET inverters and / or a common collector current gain stage.

[0009] The rectifier unit is connected directly downstream of the secondary coil, for example. Preferably, the rectifier unit comprises at least one diode. More preferably, the rectifier unit comprises at least two diodes. The rectifier unit can be configured as a full-wave rectifier or as a half-wave rectifier. Preferably, the rectifier unit comprises at least one capacitor, for example, exactly two capacitors. The rectifier unit is preferably configured as a voltage multiplier, more preferably as a voltage doubler, for example according to a Delon bridge circuit or the like. Advantageously, the signal strength, in particular of the driver signal, can be increased on the secondary side.The phrase "the latch unit is connected between the gate electrode and the rectifier unit" means, in particular, that the latch unit is electrically connected between the gate electrode and the rectifier unit, especially by wire. The latch unit is preferably, and especially in at least one operating state, at least partially interposed between the gate electrode and the rectifier unit. The latch unit preferably comprises at least one switching element, preferably a bipolar transistor. The latch unit can have at least two switching elements, for example, at least one switching element configured as a PNP transistor and at least one further switching element configured as an NPN transistor. The switching element can, for example, be configured as a high-side switching element and / or the further switching element as a low-side switching element. By way of example, the latch unit can have exactly two switching elements.The latch unit functions, in particular, at least equivalently to an electronic latch. The latch unit can preferably be activated by activating the at least one switching element, preferably the at least two switching elements. The activated latch unit is particularly intended for discharging the gate electrode.

[0010] The term "intended" means specifically programmed, designed, and / or equipped. The fact that an object is intended for a specific function means that the object fulfills and / or executes this specific function in at least one application and / or operating state.

[0011] It is further proposed that the latch unit can be activated to discharge the gate electrode, at least based on the driver signal, thereby enabling particularly efficient discharge of the gate electrode based on the driver signal. Advantageously, the gate electrode can be controlled with particular precision by means of the switch. The latch unit can be activated, in particular, based on a falling edge of the driver signal, especially the envelope of the driver signal, wherein the falling edge of the driver signal on the primary side correlates, in particular, with a falling edge of a signal received on the secondary side and rectified by the rectifier unit. The latch unit is preferably activated by activating the at least one switching element based on the driver signal, in particular the falling edge of the envelope.The switching element is preferably designed to activate upon reaching at least one base-emitter threshold voltage. Preferably, the latch unit is configured such that the base-emitter threshold voltage of the at least one switching element is reached for the falling edge of the envelope of the driver signal.

[0012] Furthermore, it is proposed that the latch unit provides a discharge path for discharging the gate electrode, distinct from a charging path for charging the gate electrode. This allows for particularly fast discharge along the discharge path, especially without reducing the charging efficiency along the charging path. Advantageously, a discharge path with a dynamic range different from that of the charging path can be provided. In particular, the discharge path can be optimized separately from the charging path, which is especially advantageous for discharge. The latch unit preferably provides discharge along the discharge path, distinct from discharge in the opposite direction to the charging direction along the charging path. The latch unit provides the discharge path, especially in the activated state.The latch unit, in particular the at least one switching element, is preferably deactivated during charging, especially for the rising edge of the envelope of the driver signal. The charging path and the discharging path are preferably arranged on the secondary side. The charging path is preferably designed for charging along a charging direction, preferably starting from the secondary coil and / or the rectifier unit, to the gate electrode. The charging path preferably passes through a resistive element of the gate driver. The resistive element is connected, for example, directly downstream of the rectifier unit. The charging path preferably passes through another resistive element of the gate driver. This resistive element preferably has a resistance at least one order of magnitude greater than the resistance of the other resistive element.The current along the charging path is particularly limited, wherein the loss of the limited current is preferably due to at least substantially, in particular at least 75%, preferably at least 90%, and preferably at least 95% of the loss, by the resistive element. The discharge path preferably runs through the at least one switching element of the activated latch unit. The discharge path preferably runs through the further resistive element and is particularly free of the resistive element in the charging path. The discharge path preferably runs through a shunt resistive element of the gate driver. The current along the discharge path is particularly limited, wherein the loss of the limited current is preferably due to at least substantially, in particular at least 75%, preferably at least 90%, and preferably at least 95% of the loss, by the further resistive element and / or the shunt resistive element.

[0013] Furthermore, it is proposed that the discharge path dynamics be faster than the charge path dynamics, thereby enabling particularly efficient and / or safe deactivation of the switch. The discharge path provided by the activated latch unit is preferably configured approximately as a short-circuit path. The discharge duration during activation of the latch unit, starting from a saturation voltage of the gate electrode, is preferably shorter than the charging duration of the gate electrode to the saturation voltage along the charge path. In particular, the "discharge duration" is understood to mean the discharge of the gate electrode from the saturation voltage to a voltage of at least substantially zero, and the "charge duration" is understood to mean the charging of the gate electrode from a voltage of at least substantially zero to the saturation voltage.The saturation voltage of the gate electrode can be, for example, at least 5 V, preferably at least 10 V, and particularly preferably at least 15 V, and / or, for example, a maximum of 50 V, preferably a maximum of 40 V, preferably a maximum of 30 V, and particularly preferably a maximum of 20 V. The charging time depends in particular on the capacitances of the at least one capacitor of the rectifier unit. Preferably, the charging time depends on an RC circuit of the gate electrode, wherein the RC circuit also functions in particular as a filter unit with respect to high-frequency ripple. The charging time is preferably less than 50 ps. The discharging time is preferably less than 50 ps, ​​advantageously less than 30 ps, ​​preferably less than 10 ps, ​​particularly preferably less than 5 ps, and particularly advantageously less than 2 ps.The duration of the discharge starting from the cessation of the pulse of the driver signal is preferably shorter by a factor of at least 5, preferably at least 10, preferably at least 15 and particularly preferably at least 20 than the duration of the charging.

[0014] It is further proposed that the latch unit be connected at least partially in parallel with the gate electrode. Advantageously, the discharge of the gate electrode can be provided in parallel with the gate electrode and at least partially in parallel with the charging path. In particular, the latch unit can provide a low-impedance circuit in parallel with the gate electrode for the discharge. Preferably, the latch unit is connected at least partially in parallel with the charging path. The latch unit is preferably connected in parallel with the gate electrode, except for at least one rectifying element mentioned below.

[0015] Furthermore, it is proposed that the latch unit comprises at least one rectifying element, in particular a diode, which has a forward bias along a charging path, in particular the one mentioned above, and blocks discharge along the charging path in the opposite direction, in particular to the charging direction. Advantageously, discharge along the charging path can be blocked, thereby achieving, in particular, a voltage drop at the latch unit during discharge. In particular, a particularly fast discharge can be ensured by the advantageous activation of the latch unit.Preferably, the diode is configured to block discharge along the charging path, particularly opposite to the charging direction, thus providing a voltage drop across the latching unit for activation on the falling edge of the driver signal. The rectifier element is preferably arranged in the charging path and is designed to provide a unidirectional current flow along the charging path. The latching unit is preferably unidirectional, particularly with respect to the charging path.

[0016] Furthermore, it is proposed that the gate driver include at least one overcurrent protection unit, wherein the latch unit can be activated by means of the overcurrent protection unit to provide overcurrent protection. In particular, the gate electrode can be discharged particularly quickly and / or efficiently in the event of an overcurrent by means of the activated latch unit, thereby enabling the switch to be deactivated particularly quickly in the event of an overcurrent. Advantageously, the safety of a circuit incorporating the switch can be increased. In particular, the service life of the switch, and especially of the circuit, can be increased by deactivating the switch in the event of an overcurrent.Furthermore, the requirements for overcurrent resistance of components in the circuit, particularly those downstream of the switch, can be reduced, thereby increasing cost-efficiency and / or reducing the complexity of the components and, in particular, the circuit. The latch unit can preferably be activated independently of the driver signal by means of the overcurrent protection unit. The gate electrode can preferably be discharged independently of the driver signal by means of the overcurrent protection unit, especially during charging and / or during the voltage pulse of the driver signal. The overcurrent protection unit is preferably designed to detect an overcurrent upstream of an input, in particular the source and / or the emitter and / or the collector, of the switch and, based on this detection, to activate the latch unit.The overcurrent protection unit is preferably designed to discharge the gate electrode via the latch unit in the event of an overcurrent and, in particular, to deactivate the switch. The overcurrent protection unit is preferably designed to detect the overcurrent by means of a comparison.

[0017] It is further proposed that the overcurrent protection unit includes a reference voltage source, in particular a shunt reference. Advantageously, the overcurrent can be detected particularly efficiently and / or reliably, especially with temperature stability. Preferably, the overcurrent protection unit, in particular the shunt reference, is designed to detect the overcurrent by comparing a voltage across the shunt resistor element with an internal reference voltage. The internal reference voltage is preferably configured as a bandgap reference and exhibits particularly high stability with respect to fluctuations in temperature, power supply, electrical load, and / or time. Preferably, the internal reference voltage has a value of less than 5 V, more preferably less than 2.5 V.The internal reference voltage can, for example, be silicon-based and preferably has a value of at least 1.2 V and / or a maximum of 1.3 V. The overcurrent protection unit is preferably designed to function as an open-collector comparator, which reduces the current, and thus in particular the voltage, at the switching element of the latch unit when the voltage to be compared, especially at the shunt resistor, is greater than the internal reference voltage. The electrical device, in particular the overcurrent protection unit, preferably includes at least one voltage limiter, in particular at least one Zener diode. The voltage limiter, in particular the Zener diode, is preferably designed to limit the voltage applied to the reference voltage source, in particular the shunt reference, and thus to protect it. Preferably, the gate voltage of the gate electrode is limited by means of the voltage limiter.The voltage limiter is preferably designed to limit the voltage to a value below the maximum rating of the shunt reference. The voltage, particularly that supplied to the shunt reference and limited by the voltage limiter (designed as a Zener diode), is preferably lower than the breakdown voltage of the Zener diode. For example, to ensure the shunt reference is suitable for a maximum voltage of 20 V, the voltage limiter can be designed to limit the voltage to a maximum of 18 V. Alternatively, other values ​​that would be considered reasonable by someone skilled in the art are conceivable.

[0018] Furthermore, it is proposed that the latch unit have the same trigger point for activation, in particular of the latch unit, by means of the overcurrent protection unit and by means of the driver signal. Advantageously, the precision and / or reliability of the overcurrent protection unit can be increased. In particular, the implementation of the overcurrent protection unit incorporating the shunt reference can be advantageously simplified, thereby advantageously improving temperature stability. The trigger point is preferably located at the base of the switching element. The latch unit is preferably designed to be triggered at the same switching element for activation by means of the overcurrent protection unit and by means of the driver signal.The overcurrent protection unit is preferably designed to trigger the latch unit, in particular the switching element, based on a falling current at the base of the switching element caused by the overcurrent protection unit, in particular caused by a current flow to the overcurrent protection unit.

[0019] Alternatively, the latch unit can have two different trigger points for activation by means of the overcurrent protection unit and by means of the driver signal. The latch unit is preferably designed to be triggered at the switching element by the driver signal and at the other switching element by means of the overcurrent protection unit. A first trigger point for activating the latch unit by means of the driver signal is preferably located at the base of the switching element, and a second trigger point for activating the latch unit by means of the overcurrent protection unit is preferably located at the base of the other switching element.The overcurrent protection unit triggers the latch unit, in particular the further switching element, preferably directly based on an input current, in particular a source current, in particular originating from the source and / or the emitter and / or the collector, of the switch at a base of the further switching element to activate the latch unit.

[0020] The gate driver is preferably designed to control at least one switch, in particular at least one high-side switch, of a bus discharge unit. Furthermore, it is proposed that the electrical device includes a bus discharge unit, in particular the one mentioned above, wherein the gate driver is designed to control at least one high-side switch of the bus discharge unit, in particular the one mentioned above. Advantageously, the switch can be controlled with particular precision, especially with a particularly short deactivation time. The bus discharge unit is preferably designed for the controlled discharge of at least one bus capacitor, in particular a circuit of the household appliance. The bus capacitor is preferably designed as a smoothing capacitor. The bus discharge unit is preferably designed for regenerative, in particular non-dissipative, discharge of the bus capacitor.In particular, the bus discharge unit can be controlled with exceptional precision by means of the gate driver, thereby enabling particularly precise charging of the bus capacitor. The charging of the bus capacitor can be set with exceptional accuracy, both in terms of timing and / or a specific charge value, by means of control via the gate driver. The bus capacitor can be part of the electrical device. The electrical device can comprise an entire circuit of the electrical appliance, preferably a household appliance, preferably a cooktop, which includes the bus capacitor and, for example, at least one rectifier connected upstream of the bus capacitor.The electrical device can include a filter unit, in particular one connected at least upstream of the rectifier, and in particular an inverter connected downstream of the bus capacitor, wherein the inverter can, for example, be provided for supplying an alternating voltage to an electrical resonant circuit for the emission of inductive radiation. The bus discharge unit can, for example, be provided for discharging the bus capacitor for the purpose of cookware detection, for example, to provide a reduced charge in the bus capacitor for the generation of a detection signal based on the charge and / or to reduce electromagnetic interference, in particular caused by a charge of the bus capacitor, during a detection.Alternatively or additionally, the bus discharge unit can be provided with any further function that would appear useful to a person skilled in the art by means of discharging the bus capacitor. The electrical device can include at least one further gate driver, for example, for controlling at least one low-side switch of the bus discharge unit. The gate driver and the further gate driver can be at least partially integrated and, for example, share at least a section of the primary side, for example, for generating the driver signal. Alternatively, the gate driver and the further gate driver can be separate from each other and / or the further gate driver can be separate from the electrical device.

[0021] Alternatively, the gate driver can be configured to control a switch that would be suitable to a person skilled in the art, for a function other than bus discharge, such as an inverter switch or the like. In particular, the gate driver can be configured to control any switch that would be suitable to a person skilled in the art and can include at least one gate electrode.

[0022] Furthermore, a method for operating an electrical device, in particular one of the above-mentioned devices, is proposed, comprising at least one isolated gate driver which controls the at least one gate electrode, wherein the driver signal is generated via modulation of the carrier signal and is transmitted via the transformer from the primary side to the secondary side of the gate driver, and wherein the gate driver has the rectifier unit on the secondary side and the latch unit connected between the gate electrode and the rectifier unit, wherein the gate electrode is discharged by means of the latch unit. Advantageously, at least one efficiency of the

[0023] The electrical device is enhanced. The method preferably comprises at least one process step, in particular a signal generation step, in which the driver information is modulated onto the carrier signal. In a further process step, in particular a transmission step, the driver signal is preferably transmitted from the primary side to the secondary side via the transformer. The driver information is then recovered and / or amplified for further use on the secondary side, preferably by means of the rectification unit, in a further process step, in particular a rectification step. The method preferably comprises a further process step, in particular a charging step, in which the gate electrode is charged along the charging path starting from the rectification unit based on the driver signal, and the switch comprising the gate electrode is activated.Preferably, the method, particularly in a first case in the absence of an overcurrent, especially at the source of the switch, comprises a further method step, in particular a driver signal discharge step, in which the gate electrode is discharged based on the driver signal. The gate electrode is discharged, particularly in the driver signal discharge step, preferably for a falling edge of the driver signal, in particular the envelope of the driver signal.

[0024] Preferably, the latch unit, particularly in the driver signal discharge step, is activated to discharge the gate electrode based on the driver signal, especially the falling edge of the driver signal. Preferably, the method, particularly in a second case where an overcurrent is present, includes a further method step, particularly an overcurrent discharge step, in which the gate electrode is discharged for a detected overcurrent, particularly at the switch source. Preferably, the latch unit, particularly in the overcurrent discharge step, is activated based on the detected overcurrent. The activated latch unit, particularly in the driver signal discharge step and / or the overcurrent discharge step, preferably provides the discharge path for discharging the gate electrode.

[0025] The electrical device, the household appliance, and the method for operating the electrical device are not limited to the application and embodiment described above. In particular, the electrical device, the household appliance, and the method for operating the electrical device may, to achieve a functionality described herein, comprise a different number of individual elements, components, units, and process steps than specified herein.

[0026] Further advantages become apparent from the following description of the drawings. The drawings illustrate exemplary embodiments of the invention. The drawings, the description, and the claims contain numerous features in combination. A person skilled in the art will expediently consider the features individually and combine them into meaningful further combinations.

[0027] They show:

[0028] Fig. 1 A schematic representation of an exemplary electrical device with an electrical component, Fig. 2 a simplified circuit diagram of the electrical component with a gate driver for controlling a gate electrode of a switch,

[0029] Fig. 3 shows a simplified circuit diagram of the gate driver, which controls the gate electrode via at least one driver signal.

[0030] Fig. 4 shows exemplary graphs with curves in a time window of (a) a rising edge and (b) a falling edge of an envelope of the driver signal.

[0031] Fig. 5 shows exemplary graphs with curves in a case of overcurrent and Fig. 6 shows a flowchart of a method for operating the electrical device.

[0032] Figure 1 shows a schematic top view of an electrical appliance 100 with an electrical device 10. The electrical appliance 100 is designed here as an exemplary household appliance 102. By way of example, the household appliance 102 is designed as a cooktop 104, in particular as an induction cooktop.

[0033] The electrical device 10 is designed in this case as a household appliance device, for example as a cooktop device, in particular as an induction cooktop device. Alternatively, another embodiment of the electrical device 10 and in particular of the electrical appliance 100, which would appear sensible to a person skilled in the art, is conceivable.

[0034] Figure 2 shows a simplified circuit diagram of at least one part of the electrical appliance 100 and, in this case, the exemplary electrical device 10 as part of the cooktop 104.

[0035] The electrical device 10, as exemplified here, includes a bus capacitor 82, in particular one connected upstream of a rectifier 80 of the electrical device 10. The bus capacitor 82 can, by way of example, function at least as a smoothing capacitor.

[0036] In the schematic electrical circuit diagram of Figure 2, a simplified equivalent resistance 84 is shown, which is arranged electrically in parallel with the bus capacitor 82. The equivalent resistance 84 represents all electrical loads that can be connected downstream of the bus capacitor 82, for example, at least one inverter (not shown) and / or at least one inductor (not shown) and / or the like. The electrical device 10 can include at least some of the components associated with the equivalent resistance 84. In this example, the electrical device 10 includes a bus discharge unit 90. The bus discharge unit 90 has at least one high-side switch 92 and one low-side switch 94. The high-side switch 92 is connected in parallel with at least one high-side diode 86 of the rectifier 80. The low-side switch 94 is connected in parallel with at least one low-side diode 88 of the rectifier 80.

[0037] The bus capacitor 82 can be discharged, particularly regeneratively, by means of the bus discharge unit 90. The bus capacitor 82 can be discharged by controlling the high-side switch 92 and / or the low-side switch 92.

[0038] The electrical device 10 has at least one isolated gate driver 12, which is intended to control at least the high-side switch 92 of the bus discharge unit 90. At least a part of the electrical device 10, and for example of the gate driver 12, may be intended to at least partially control the low-side switch 92 of the bus discharge unit 90. Alternatively, the electrical device 100 and / or the electrical device 10 may have at least one further gate driver separate from the gate driver 12 for controlling the low-side switch 92.

[0039] Alternatively, the electrical device 10 can be designed without at least a part of the bus discharge unit 90, the bus capacitor 82, the loads represented by the equivalent resistor 84, and / or the like. In particular, it is conceivable that the electrical device 10 comprises only the at least one gate driver 12 and, by way of example, additionally at least one gate electrode 32 controlled by the gate driver 12, and in particular at least one switch comprising the at least one gate electrode 32. In particular, the switch comprising the gate electrode 32 can be the high-side switch 92 of the bus discharge unit 90 or any other switch that would be suitable to a person skilled in the art (not shown), for example, a switch of an inverter or the like.Alternatively or additionally, the gate driver 12 can, for example, be integrated into a switch control circuit in a circuit diagram that differs at least partially or completely from the circuit diagram in Figure 2 and appears sensible to a person skilled in the art, exemplified by an embodiment of the electrical device different from the cooktop 104. Figure 3 shows a simplified circuit diagram of the gate driver 12 of the electrical device 10.

[0040] The electrical device 10 includes at least one isolated gate driver 12 for controlling at least one gate electrode 32. The electrical device 10 includes the gate electrode 32. The gate electrode 32 can be controlled by charging and / or discharging via the gate driver 12.

[0041] The high-side switch 92 includes the gate electrode 32. The high-side switch 92 can be activated to charge the gate electrode 32 and deactivated to discharge the gate electrode 32. The high-side switch 92 is shown as an example of a MOSFET switch; alternatively, another design of the high-side switch 92 that would be suitable for a person skilled in the art is conceivable.

[0042] The gate driver 12 has at least one transformer 14 for transferring a driver signal from a primary side 20 to a secondary side 30 of the gate driver 12. The primary side 20 and the secondary side 30 are galvanically isolated from each other via the transformer 14 and, in particular, are connected to each other at least for data transmission purposes.

[0043] The gate driver 12 has a modulation unit 24 on the primary side 20, shown here in a highly simplified form, which generates the driver signal. The driver signal is generated by modulating a carrier signal. Specifically, the driver signal is generated by modulating, for example, an amplitude-shift keying (AMK) signal from a high-frequency carrier signal with a signal containing driver information. The carrier signal contains the driver information in an envelope. The envelope is designed as a square-wave voltage pulse, by means of which the gate electrode 32 can be charged.

[0044] The transformer 14 has a primary coil 22 on the primary side 20. The gate driver 12 has a resonant capacitance 26 on the primary side 20, which together with at least the primary coil 22 forms a resonant circuit for the emission of the driver signal.

[0045] The transformer 14 has a secondary coil 62 on the secondary side 30, which is designed to receive a signal originating from the primary coil 22. The gate driver 12 has a rectifier unit 34 on the secondary side 30. The rectifier unit 34 is connected downstream of the secondary coil 62. The rectifier unit 34 is configured as a voltage doubler.

[0046] The gate driver 12 has a latch unit 36 ​​for discharging the gate electrode 32, the latch unit 36 ​​being connected between the gate electrode 32 and the rectifier unit 34. The latch unit 36 ​​has at least one switching element 96. The switching element 96 is configured as a pnp bipolar transistor. The latch unit 36 ​​has at least one further switching element 98. The further switching element 98 is configured as an npn bipolar transistor.

[0047] The latch unit 36 ​​can be activated, at least based on the driver signal, to discharge the gate electrode 32. The latch unit 36 ​​can be activated by activating the switching element 96. The switching element 96 is designed to activate itself upon reaching at least a base-emitter threshold voltage. The switching element 96 can be silicon-based and have a base-emitter threshold voltage of at least substantially 0.7 V.

[0048] Latch unit 36 ​​can be activated based on a falling edge of the envelope of the driver signal. Switching element 96 can also be activated based on the falling edge of the envelope of the driver signal. Latch unit 36 ​​is connected such that at least the base-emitter threshold voltage for the falling edge of the envelope of the driver signal is reached at switching element 96 to activate it.

[0049] The further switching element 98 can be activated based on the descending edge of the envelope of the driver signal, in particular based on the activation of the switching element 96.

[0050] The latch unit 36 ​​provides a discharge path 44 for discharging the gate electrode 32, distinct from a charging path 40 for charging the gate electrode 32. The charging path 40 is designed for charging along a charging direction 42, in particular from the secondary coil 62 and / or the rectifier unit 34, to the gate electrode 32. The discharge path 44 is designed for discharging along a discharge direction 46 from the gate electrode 32. The charging path 40 and the discharge path 44 partially overlap, particularly at the gate electrode 32. The discharge direction 46 is directed opposite to the charging direction 42, at least in an overlapping section of the charging path 40 and the discharge path 44.

[0051] The charging path 40 passes through a resistor element 70 of the gate driver 12. In this example, the resistor element 70 is connected directly downstream of the rectifier unit 34. The resistor element 70 is connected between the rectifier unit 34 and a rectifier element 38. The charging path 40 passes through another resistor element 72 of the gate driver 12. This further resistor element 72 is connected downstream of the resistor element 70 along the charging direction 42. This further resistor element 72 is connected between the rectifier element 38 and the gate electrode 32.

[0052] The resistive element 70 has a resistance at least one order of magnitude greater than the resistance of the further resistive element 72. For example, the resistive element 70 can have a value of at least 1 kΩ and / or a maximum of 10 kΩ, and / or the further resistive element 72 a value of at least 10 Ω and / or a maximum of 200 Ω, for instance, at least substantially 100 Ω. Alternatively, other values ​​that appear reasonable to a person skilled in the art are conceivable. The current along the charging path 40 is limited, with the limited current being limited at least substantially by the resistive element 70.

[0053] The discharge path 44 passes through the switching element 96. The discharge path 44 passes through the further switching element 98. The discharge path 44 passes through the further resistor element 70. The discharge path 44 passes through a shunt resistor element 76 of the gate driver 12. The shunt resistor element 76 can have an exemplary resistance of at least 0.5 Ω and / or a maximum of 1 Ω. Alternatively, another value that appears reasonable to a person skilled in the art is conceivable. The current along the discharge path 44 is limited, the limited current being restricted at least substantially by the further resistor element 72 and the shunt resistor element 76.

[0054] A dynamic along the charging path 40 in the charging direction 42 is faster than a

[0055] Dynamics of a path (not shown) from the rectifier unit 34 to a trigger point 60 at the base of the switching element 96 during charging. The base-emitter threshold voltage is undershot during charging. The switching element 96 is deactivated during charging. The latch unit 36 ​​is deactivated during charging.

[0056] The dynamics of the discharge path 44 are faster than those of the charging path 40. The duration of a discharge process by activating the latch unit 36 ​​is shorter than the duration of a charging process for charging the gate electrode 32 along the charging path 40 (see Figures 4a and 4b).

[0057] The latch unit 36 ​​includes at least the rectifying element 38, which has a forward direction along the charging direction 42 along the charging path 40 and blocks a discharge along the charging path 40 in the opposite direction 52 to the charging direction 42. The rectifying element 38 is designed as a diode 48. The rectifying element 38 is connected in series upstream of the gate electrode 32 along the charging direction 42.

[0058] By means of the rectifying element 38, in particular by blocking discharge along the charging path 40 in the opposite direction 52 to the charging direction 42, discharge is only provided along the discharge path 44. By means of the rectifying element 38, in particular by blocking discharge along the charging path 40 in the opposite direction 52 to the charging direction 42, exceeding the base-emitter threshold voltage of the switching element 96, in particular activating the latch unit 36, is provided and / or supported during discharge.

[0059] The latch unit 36 ​​can, by way of example, include at least one further rectifying element 50. This further rectifying element 50 is configured as a diode. The further rectifying element 50 is designed to cancel the voltage drop of the rectifying element 38. The rectifying element 38 and the further rectifying element 50 can share a common anode pair to maintain identical design equations for the latch unit 36, particularly with respect to a holding current, since their voltage drops cancel each other out.

[0060] Alternatively, the latch unit 36 ​​can be configured without the further rectifying element 50. The latch unit 36 ​​is connected at least partially in parallel to the gate electrode 32. The latch unit 36, excluding at least the rectifying element 38, is connected in parallel to the gate electrode 32.

[0061] The gate driver 12 has at least one overcurrent protection unit 54, wherein the latch unit 36 ​​can be activated by means of the overcurrent protection unit 54 to provide overcurrent protection. The latch unit 36 ​​can be activated by means of the overcurrent protection unit 54 to discharge the gate electrode 32. The latch unit 36 ​​can be activated by means of the overcurrent protection unit 54 independently of the driver signal. The gate electrode 32 can be discharged by means of the overcurrent protection unit 54 independently of the driver signal.

[0062] The overcurrent protection unit 54 is designed to activate the latch unit 36 ​​in the event of a detected overcurrent. The overcurrent protection unit 54 is designed to detect the overcurrent. The overcurrent is an overcurrent at a source of the high-side switch 92. The overcurrent protection unit 54 is electrically connected to the source of the high-side switch 92.

[0063] The overcurrent protection unit 54 includes a reference voltage source 56. The reference voltage source 56 can be configured as a shunt reference 58.

[0064] The overcurrent protection unit 54 is designed to detect overcurrent by comparing the voltage across the shunt resistor element 76 with an internal reference voltage. For example, the internal reference voltage in this case has a value of at least substantially 1.24 V. Alternatively, another value that would be considered reasonable by a person skilled in the art is conceivable.

[0065] The gate driver 12 includes a pull-down resistor element 74. The pull-down resistor element 74 is designed to keep the latch unit 36 ​​deactivated until the falling edge and / or overcurrent occurs. The pull-down resistor element 74 can, for example, have a resistance greater than 10 kΩ. Alternatively, another value that would be considered reasonable by a person skilled in the art is conceivable.

[0066] The latch unit 36 ​​has the same trigger point 60 for activation by means of the overcurrent protection unit 54 and by means of the driver signal. The trigger point 60 is connected to and specifically arranged at the base of the switching element 96. The latch unit 36 ​​is designed to be triggered at the switching element 96 for activation by means of the overcurrent protection unit 54 and by means of the driver signal. The latch unit 36 ​​is designed to activate the same switching element 96 first, in each case by means of the overcurrent protection unit 54 and by means of the driver signal, with the further switching element 98 being activatable subsequently. The overcurrent protection unit 54 is designed to trigger the latch unit 36, specifically the switching element 96, based on a current drop at the base of the switching element 96 caused by the overcurrent protection unit 54.

[0067] Alternatively or additionally, the electrical device 10 can include a further overcurrent protection unit 66. In this example, the electrical device 10 includes a circuit diagram unit 64, which can be configured as the further overcurrent protection unit 66, either as an alternative or in addition to the overcurrent protection unit 54. The latch unit 36 ​​has different trigger points 60 and 68 for activation by means of the further overcurrent protection unit 66 and by means of the driver signal. The latch unit 36 ​​is designed to be triggered at the further switching element 98 by means of the further overcurrent protection unit 54 for activation. The latch unit 36 ​​is designed to first activate the further switching element 98 in order to activate the latch unit 36 ​​by means of the further overcurrent protection unit 66, whereby the switching element 96 can be activated subsequently.The additional overcurrent protection unit 66 triggers the latch unit 36, in particular the additional switching element 98, directly based on a source current originating from the source at a base of the additional switching element 98, thus activating it. The additional switching element 96 can be activated by the additional overcurrent protection unit 66 through a voltage generated at the shunt resistor element 76, based on the overcurrent. Alternatively, other values ​​that appear sensible to a person skilled in the art are conceivable.

[0068] Figure 4a shows graphs with curves 120, 122, 124 in a time window of a rising edge of the envelope of the driver signal.

[0069] Curve 120 shows the signal containing the driver information on axis 114, with voltage in volts plotted against axis 110, representing time in milliseconds. Curve 122 shows the driver signal, whose envelope contains the driver information, on axis 116, with voltage in volts plotted against axis 110, representing time in milliseconds. Curve 124 shows the voltage of the gate electrode 32 on axis 118, with voltage in volts plotted against axis 110, representing time in milliseconds. The gate electrode 32 is charged upon the onset of the voltage pulse of the driver signal, with the voltage of the gate electrode 32 rising until saturation. For example, the charging time from the onset of the driver signal pulse until the gate electrode 32 reaches saturation is 31 ps.

[0070] Figure 4b shows graphs with curves 120 and 122 from Figure 4a in a time window of a falling edge of the envelope of the driver signal over an axis 112 representing time in milliseconds, which has an increased time resolution compared to axis 110 representing time in Figure 4a. The gate electrode 32 is discharged to interrupt the voltage pulse of the driver signal, whereby the voltage of the gate electrode 32 decreases. The duration of the discharge from the saturation voltage is, for example, less than 2 ps, in particular less than 1.5 ps, and in this case between 1 ps and 2 ps. In this case, at least 90% of the discharge duration is configured as a delay for activating the latch unit 36. In particular, the latch unit 36, in the activated state, is designed to discharge at least 90%, and in particular at least 95%, of the charge of the gate electrode 32.The discharge time in the activated state of the latch unit 36 ​​is, for example, less than 0.2 ps, in particular less than 0.15 ps, and in this case between 0.1 ps and 0.2 ps. The discharge time, starting from the cessation of the driver signal pulse and the saturation voltage of the gate electrode 32, is in this case at least 20 times shorter than the charging time, starting from the onset of the driver signal pulse until the saturation voltage of the gate electrode 32.

[0071] Figure 5 shows graphs with curves 120, 122, 132, and 134 in a case where an overcurrent is present. Curve 120 shows the signal containing the driver information, and curve 122 shows the driver signal from Figures 4a and 4b plotted against a time in milliseconds on axis 126, with a reduced time resolution compared to Figures 4a and 4b. Curve 132 shows the overcurrent plotted against a current in amperes on axis 130 and a time in milliseconds on axis 126. An example is an overcurrent with a pulse duration of 1 ms during the last millisecond of the driver signal pulse. The at least one overcurrent protection unit 54, 66 is designed to discharge the gate electrode 32 before the voltage pulse of the driver signal is interrupted by means of the latch unit 36 ​​when the overcurrent occurs.Curve 134 shows the voltage of the gate electrode 32, discharged by means of at least one overcurrent protection unit 54, 66, on axis 128, a voltage in volts over axis 126, and time in milliseconds. The voltage of the gate electrode 32 drops before the voltage pulse of the driver signal is interrupted, in the presence of the overcurrent.

[0072] Figure 6 shows a flowchart for a method for operating the electrical device 10, wherein the at least one isolated gate driver 12 controls the at least one gate electrode 32, wherein the driver signal is generated via modulation of the carrier signal and is transmitted via the transformer 14 from the primary side 20 to the secondary side 30 of the gate driver 12, and wherein the gate driver 12 has the rectifier unit 34 on the secondary side 30 and the latch unit 36 ​​connected between the gate electrode 32 and the rectifier unit 34, wherein the gate electrode 32 is discharged by means of the latch unit 36.

[0073] The method includes a signal generation step 200 in which the driver information for generating the driver signal on the primary side 20 is modulated onto the carrier signal.

[0074] In a transmission step 202 of the procedure, the driver signal is transmitted via the transformer 14 from the primary side 20 to the secondary side 30.

[0075] The driver information is restored and / or amplified in a rectification step 204 of the procedure by means of the rectification unit 34 on the secondary side 30.

[0076] The method includes a charging step 206 in which the gate electrode 32 is charged based on the driver signal along the charging path 40 starting from the rectifier unit 34.

[0077] In a first case, particularly in the absence of an overcurrent, the method includes a driver signal discharge step 208 in which the gate electrode 32 is discharged based on the driver signal. The gate electrode 32 is discharged in the driver signal discharge step 208 based on a falling edge of the envelope of the driver signal. The latch unit 36 ​​is activated in the driver signal discharge step 208 based on the falling edge of the envelope of the driver signal to discharge the gate electrode 32.

[0078] In a second case, particularly in the presence of an overcurrent, the method includes an overcurrent discharge step 210 in which the gate electrode 32 is discharged for the detected overcurrent. The latch unit 36 ​​is activated in the overcurrent discharge step 210 based on the detected overcurrent.

[0079] Reference sign

[0080] 10 Electrical device

[0081] 12 gate drivers

[0082] 14 Transformer

[0083] 20 Primary page

[0084] 22 Primary coil

[0085] 24 modulation units

[0086] 26 Resonance capacity

[0087] 30 Secondary page

[0088] 32 Gate electrode

[0089] 34 Rectifier unit

[0090] 36 Latch units

[0091] 38 Rectifying element

[0092] 40 charging path

[0093] 42 Charging direction

[0094] 44 Unloading path

[0095] 46 Discharge direction

[0096] 48 diodes

[0097] 50 additional rectifying elements

[0098] 52 direction

[0099] 54 Overcurrent protection unit

[0100] 56 Reference voltage source

[0101] 58 Shunt Reference

[0102] 60 trigger point

[0103] 62 Secondary coil

[0104] 64 Circuit diagram unit

[0105] 66 additional overcurrent protection units

[0106] 68 more trigger points

[0107] 70 resistance element further resistance element

[0108] Pull-down resistor element

[0109] Shunt resistance element

[0110] rectifier

[0111] bus capacitor

[0112] Equivalent resistance

[0113] High-side diode

[0114] Low-side diode

[0115] Bus discharge unit

[0116] High-side switch

[0117] Low-side switch

[0118] Switching element, further switching element

[0119] electrical appliance

[0120] household appliance

[0121] cooktop

[0122] axis

[0123] axis

[0124] axis

[0125] axis

[0126] axis

[0127] curve

[0128] curve

[0129] curve

[0130] axis

[0131] axis

[0132] axis

[0133] curve

[0134] curve

[0135] Signal generation step

[0136] Transmission step, rectification step, charging step, driver signal discharge step, overcurrent discharge step

Claims

Claims 1. Electrical device (10), comprising at least one isolated gate driver (12) for controlling at least one gate electrode (32), wherein the gate driver (12) generates at least one transformer (14) for transferring a driver signal via modulation of a carrier signal from a primary side (20) to a secondary side (30) of the gate driver (12), a rectifier unit (34) on the secondary side (30) and a latch unit (36) for discharging the gate electrode (32), wherein the latch unit (36) is connected between the gate electrode (32) and the rectifier unit (34).

2. Electrical device (10) according to claim 1, characterized in that the latch unit (36) can be activated at least on the basis of the driver signal to discharge the gate electrode (32).

3. Electrical device (10) according to claim 1 or 2, characterized in that the latch unit (36) provides a discharge path (44) for discharging the gate electrode (32) different from a charging path (40) for charging the gate electrode (32).

4. Electrical device (10) according to claim 3, characterized in that the dynamics of the discharge path (44) are faster than the dynamics of the charging path (40).

5. Electrical device (10) according to one of the preceding claims, characterized in that the latch unit (36) is at least partially connected in parallel to the gate electrode (32).

6. Electrical device (10) according to one of the preceding claims, characterized in that the latch unit (36) has at least one rectifying element (38), in particular a diode (48), which has a forward direction along a charging direction (42) along a charging path (40) and blocks a discharge along the charging path (40) in the opposite direction (52).

7. Electrical device (10) according to one of the preceding claims, characterized in that the gate driver (12) has at least one overcurrent protection unit (54, 66), wherein the latch unit (36) can be activated to provide protection against an overcurrent by means of the overcurrent protection unit (54, 66).

8. Electrical device (10) according to claim 7, characterized in that the overcurrent protection unit (54, 66) has a reference voltage source (56), in particular a shunt reference (58).

9. Electrical device (10) according to claim 7 or 8, characterized in that the latch unit (36) has the same trigger point (60) for activation by means of the overcurrent protection unit (54) and by means of the driver signal.

10. Electrical device (10) according to one of the preceding claims, characterized by a bus discharge unit (90), wherein the gate driver (12) is provided to control at least one high-side switch (92) of the bus discharge unit (90).

11. Electrical appliance (100), in particular household appliance (102), advantageously hob (104), with an electrical device (10) according to one of the preceding claims.

12. Method for operating an electrical device (10) according to one of claims 1 to 10, comprising at least one isolated gate driver (12) which controls the at least one gate electrode (32), wherein the driver signal is generated via modulation of the carrier signal and is transmitted via the transformer (14) from the primary side (20) to the secondary side (30) of the gate driver (12), and wherein the gate driver (12) has the rectifier unit (34) on the secondary side (30) and the latch unit (36) connected between the gate electrode (32) and the rectifier unit (34), wherein the gate electrode (32) is discharged by means of the latch unit (36).

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