Gate driver for controlling power switch and corresponding method

Abstract

The invention discloses a gate driver for controlling a power switch and a corresponding method. The gate driver includes a zero cross detection circuit and a control signal generation circuit. The zero-crossing detection circuit receives a load current signal indicative of a load current of the power switch, detects a zero-crossing of the load current, and generates a zero-crossing detection signal based on detecting the zero-crossing. The control signal generation circuit receives an input control signal indicating to turn on or off the power switch. The control signal generation circuit generates a turn-off signal based on the zero-cross detection signal if the input control signal indicates turning off the power switch, or determines whether a timeout interval after indicating the turn-off has expired, generates the turn-off signal independently of the zero-cross detection signal if the timeout interval has expired, and outputs the turn-off signal based on the zero-cross detection signal if the timeout interval has expired. And provide a turn-off signal to the power switch.

Description

Technical Field

[0001] The present invention relates generally to gate drivers and more precisely to soft-switching gate drivers, ie, zero-current turn-off drivers with safe turn-off functionality. Background Art

[0002] Solid-state relays (SSRs) including thyristors inherently provide turn-off zero current switching (ZCS), i.e., the SSR turns off only when the load current crosses 0A. Based on ZCS, the SSR is able to achieve soft switching, i.e., switching with reduced or even no switching losses, because the load current may be at or close to 0A at turn-off. In addition to the reduction in switching losses, soft switching based on ZCS can also increase the reliability of the driven power switch due to the reduction in current-induced voltage overshoot. However, the ZCS function may cause safety issues during turn-off in cases where the load current never crosses 0A. In these cases, the thyristors will not turn off due to the inherent ZCS function. For example, these situations may occur when the current supplied to the SSR by the inverter changes from AC to DC due to a fault at the inverter, or when the load coupled to the SSR provides leakage current resulting in the current never crossing 0A.

[0003] Despite these safety issues, ZCS is still desirable in view of the reduction of switching losses and the increase of reliability of the driven power switch. Therefore, there are methods of introducing ZCS functionality into switches that do not inherently have ZCS functionality, such as metal oxide field effect transistors (MOSFETs), insulated gate bipolar transistors (IGBTs), or bipolar junction transistors (BJTs), for example, by using a snubber or similar circuitry. Therefore, in order to give these types of switches a ZCS functionality, additional circuitry is required.

[0004] Therefore, an object of the present disclosure is to provide ZCS functionality for any type of switch with less work while achieving safe shutdown when the load current does not reach or cross 0A. Summary of the invention

[0005] To achieve this purpose, the present disclosure provides a gate driver configured to control a power switch. The gate driver includes a zero-crossing detection circuit coupled to a load terminal of the power switch. The zero-crossing detection circuit is configured to: receive a load current signal indicating a load current of the power switch, detect the zero-crossing of the load current based on the received load current signal, and generate a zero-crossing detection signal based on the zero-crossing of the load current signal. The gate driver also includes a control signal generating circuit coupled to the zero-crossing detection circuit. The control signal generating circuit is configured to receive an input control signal indicating turning on or off the power switch. The control signal generating circuit is also configured to: if the input control signal indicates turning off the power switch, generate a shutdown signal based on the zero-crossing detection signal, or determine whether a timeout interval after indicating the shutdown has expired, and if the timeout interval has expired, generate a shutdown signal regardless of the zero-crossing detection signal, and provide the shutdown signal to the control terminal of the power switch.

[0006] The present disclosure also provides a method for controlling a power switch using a gate driver. The method includes: receiving a load current signal indicating a load current of the power switch; detecting a zero crossing of the load current of the power switch; detecting the zero crossing of the load current based on the received load current signal; generating a zero crossing detection signal based on detecting the zero crossing of the load current signal; receiving an input control signal indicating turning on or off the power switch; and if the input control signal indicates turning off the power switch, generating a shutdown signal based on the zero crossing detection signal, or determining whether a timeout interval after indicating the shutdown has expired, and if the timeout interval has expired, generating a shutdown signal regardless of the zero crossing detection signal, and providing the shutdown signal to a control terminal of the power switch. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Examples of the present disclosure will be described with reference to the following drawings, wherein like reference numerals refer to like elements throughout.

[0008] Figures 1A to 1D A gate driver configured to control a power switch according to an example of the present disclosure is shown.

[0009] Figure 2 A gate driver including a transformer across a galvanic isolation arrangement is shown according to an example of the present disclosure.

[0010] Figure 3 A flow chart of a method of controlling a power switch using a gate driver according to an example of the present disclosure is provided.

[0011] It should be understood that the above-mentioned drawings are in no way intended to limit the present disclosure. Rather, these drawings are provided to aid in understanding the present disclosure. It will be readily understood by those skilled in the art that aspects of the present invention shown in one drawing may be combined with aspects in another drawing, or may be omitted, without departing from the scope of the present disclosure. DETAILED DESCRIPTION

[0012] The present disclosure generally provides a gate driver configured to control a power switch and a corresponding method. The gate driver is configured to receive an input control signal that instructs the gate driver to turn on or off the power switch and switch the power switch accordingly. At least when the power switch is turned off, the gate driver is configured to perform such operation when the load current of the power switch crosses a current level of 0A. To this end, the gate driver is configured to detect zero crossings, i.e., detect whether the load current crosses a current level of 0A, and to turn off the power switch according to the input control signal when zero crossing is detected. In order to ensure that the power switch is safely turned off, the gate driver is also configured to: if a timeout interval has expired, the power switch is turned off regardless of the detection of zero crossing. The timeout interval starts when the input control signal indicates that the power switch is to be turned off, and expires after a duration defined according to a turn-off delay, which is acceptable for the practical implementation of the gate driver considering the voltage level at which the power switch operates.

[0013] The gate drivers of some examples of the present disclosure may be implemented as solid-state isolators. In such examples, the input control signal causes power to be supplied to the control terminal of the power switch until the power switch is instructed to be turned off. Therefore, the gate driver in such examples continues to supply power to the control terminal of the power switch until a zero crossing is detected or until a timeout interval expires. It will therefore be understood that the term "gate driver" in the context of the present disclosure should be understood to refer to both a drive circuit that couples the control terminal of the power switch to one of an off voltage and an on voltage according to an input control signal, and a solid-state relay that generates an on voltage and an off voltage according to an input control signal.

[0014] The general concept will be described with reference to the accompanying drawings, in which Figures 1A to 1D The gate driver is shown as a drive circuit, and Figure 2 The gate driver is shown as a solid-state isolator. Figure 3 A flow chart of a method of controlling a power switch according to the above general concept is provided.

[0015] Figure 1A FIG. 2 shows a gate driver 200 configured to control a power switch. To this end, the gate driver 200 is configured to control a power switch. Figure 1A 1 is shown coupled to the power switch 100 .

[0016] The power switch 100 can be any type of power switch configured to have a high voltage blocking capability. For example, the power switch can block voltages of at least 400V, such as 450V, 900V, 1200V, 1800V, or 3300V. In order to achieve such a voltage blocking capability, the power switch can be, for example, a silicon or silicon carbide (SiC) MOSFET, a silicon or SiC IGBT, or a gallium nitride high electron mobility transistor (GaN-HEMT). It will be understood that the voltage levels and technology types discussed with respect to the power switch are provided only as examples. In addition to those mentioned herein, the present disclosure can be practiced with other high voltage levels and other power switch technologies.

[0017] In some examples of the present disclosure, the power switch 100 may include a current sensing capability. That is, the power switch 100 may be configured to provide a current sensing capability indicating a load current of the power switch 100 , ie, a current sensed at the first load terminal 100 . L1 With the second load terminal 100 L2 The current sensing capability may be implemented, for example, by shunting the current through some of the transistor cells (e.g., one or ten transistor cells) that form the power switch 100. It will be understood that the current sensing capability of the power switch 100 may also be provided in other ways, and in some examples of the present disclosure, the current sensing capability of the power switch 100 may not exist.

[0018] The power switch 100 has a control terminal 100 C , first load terminal 100 L1 and the second load terminal 100 L2 . Control terminal 100 C Coupled to the gate driver 200. The first load terminal 100 L1 Can be coupled to the power supply voltage V DD , power supply voltage V DD For example, a voltage level of 600 V, 1200 V or 1800 V may be provided. L2 can be coupled to a current sensing resistor R as shown SENSE , or can be coupled to the ground voltage GND. If the power switch 100 is used in a half-bridge configuration, the first load terminal 100 L1 and / or the second load terminal 100 L2 It may also be coupled to another power switch. In addition, the power switch 100 may be coupled to a load at one of its load terminals. If the power switch 100 includes a current sensing capability, the power switch 100 may also include a current sensing terminal.

[0019] The gate driver 200 includes a zero-crossing detection circuit 230. The zero-crossing detection circuit 230 is configured to receive a load current signal S indicating a load current of the power switch 100. LC , and based on the detected load current signal S LC The zero crossing detection signal S is generated by ZCD As discussed above, in the context of the present disclosure, zero crossing refers to the load current of the power switch 100 and thus the load current signal S LC A value corresponding to a current level of 0 A load current is reached or crossed.

[0020] To this end, the zero-crossing detection circuit 230 may be coupled to the load current terminal T of the gate driver 200. LC and ground terminal T GND ,like Figure 1A to Figure 2 As shown. Load current terminal T LC Can be configured to receive a load current signal S LC . Ground terminal T GND Can be configured to be coupled to a ground voltage GND, and the ground voltage GND can be used as a reference voltage for detecting zero crossing. Figure 1A to Figure 2 In the example, the load current terminal T LC and ground terminal T GND Also coupled to the current sensing resistor R SENSE . Figure 1A to Figure 2 The current sensing resistor R SENSE The zero-crossing detection circuit 230 is coupled in series with the power switch 100 and thus receives the load current of the power switch 100. Therefore, the zero-crossing detection circuit 230 can be based on the current sensing resistor R SENSE In this example, the zero-crossing detection circuit 230 may include a circuit coupled to the ground terminal T GND and load current terminal T LC The zero-crossing comparator 231 can be configured to output a zero-crossing detection signal S ZCD , zero-crossing detection signal S ZCD With load current signal S LC has crossed the value corresponding to the current level of the 0A load current; and maintaining the zero-crossing detection signal S ZCD Until the power switch 100 is turned off. In other examples, if the power switch 100 includes a current sensing capability, the load current terminal T LCThe zero-crossing detection circuit 230 may be coupled to a current sensing terminal of the power switch 100 or may be coupled to other current sensing elements, such as a Hall effect sensor, a giant magnetoresistance (GMR) sensor, or a tunnel magnetoresistance (TMR) sensor. In other words, the zero-crossing detection circuit 230 may be configured to interface with any type of current sensing element that is configured to sense the load current of the power switch 100 and thereby provide a load current signal S to the zero-crossing detection circuit 230. LC Based on the load current signal S LC The zero-crossing detection circuit 230 is configured to generate a zero-crossing detection signal S ZCD , for example, by converting the load current signal S LC Compared with the reference voltage (such as Figure 1B to Figure 2 as shown), or by using a load current signal S LC Any other means of providing an indication of a value that indicates the load current of the power switch 100 has crossed a 0 A current value.

[0021] The gate driver 200 further includes a control signal generating circuit 220. The control signal generating circuit 220 is coupled to the zero-crossing detection circuit 230 to receive the zero-crossing detection signal S ZCD The control signal generating circuit 220 is configured to receive an input control signal S indicating turning on or off the power switch 100. IN Therefore, the input control signal S IN Determine whether the power switch 100 is to be closed or opened, and instruct the power switch 100 to open or close the power switch 100 accordingly. IN It may be provided, for example, by a microcontroller or some other control logic coupled to the gate driver 200. In order to receive the input control signal S IN , the gate driver 200 may include a control input terminal T IN , and the control signal generating circuit 220 can be coupled to the control input terminal T accordingly. IN .

[0022] If the input control signal S IN Instructing to turn off the power switch, the control signal generating circuit 220 is configured to ZCD To generate the shutdown signal S OFF That is, if the input control signal S IN indicates to the gate driver 200 that the power switch 100 is to be turned off, and if the zero-crossing detection signal S ZCD Indicating that a zero crossing of the load current of the power switch 100 has occurred, the control signal generating circuit 220 generates a shutdown signal S OFF In addition, the control signal generating circuit 220 is configured to determine the input control signal SIN Indicates whether the timeout interval after shutdown has expired. If the timeout interval has expired, the control signal generation circuit 220 is configured to communicate with the zero-crossing detection signal S ZCD The shutdown signal S is generated independently OFF In other words, the control signal generating circuit 220 generates a control signal according to the input control signal S IN The following instructions generate a shutdown signal S OFF , that is, once the load current of the power switch 100 is detected to be zero-crossing, the gate driver 200 should turn off the power switch 100. However, if the input control signal S IN If the load current of the power switch 100 is not detected to be zero-crossing within the timeout interval after the power switch 100 is turned off, the control signal generating circuit 220 generates the turn-off signal S even if the load current of the power switch 100 is not detected to be zero-crossing, OFF .

[0023] In short, the input control signal S IN After the power switch 100 is turned off, once the zero-crossing detection signal S ZCD Indicating that the load current of the power switch 100 crosses zero, or once the timeout interval has expired, the control signal generation circuit 220 generates the shutdown signal S OFF Then, the control signal generating circuit 220 turns off the signal S OFF The control terminal T provided to the power switch 100 CTRL Therefore, the control signal generating circuit 220 can achieve soft switching while ensuring safe shutdown when the zero crossing of the load current does not occur as quickly as required by the environment in which the gate driver 200 is deployed. Therefore, this function of the control signal generating circuit 220 can also be referred to as safe soft switching.

[0024] In order to determine the input control signal S IN Indicating whether the timeout interval after turning off the power switch 100 has expired, the control signal generating circuit 220 can also be configured to: IN The time is counted from the time the shutdown is indicated, and the counted time is compared with a time threshold, which defines a timeout interval.

[0025] In some examples of the present disclosure, for safety reasons, it may be desirable to controllably decide whether to input the control signal S IN Indicates whether the power switch 100 is to be turned off immediately or only when the load current crosses zero or a timeout interval expires. To this end, the control signal generation circuit 220 may also be configured to receive a zero-crossing control activation signal S ZCTRL . Zero-crossing control activation signal S ZCTRLIt can have a zero-crossing control activation value or a zero-crossing control inactivation value. ZCTRL When the zero-crossing control activation value is set, the control signal generating circuit 220 may generate the shutdown signal S only when the load current of the power switch 100 crosses zero or when the load current of the power switch 100 does not cross zero within a timeout interval. OFF When the zero-crossing control activation signal S ZCTRL When the control signal generating circuit 220 has a zero-crossing control inactive value, the control signal generating circuit 220 may input the control signal S IN The shutdown signal S is generated immediately when indicating that the power switch 100 is to be turned off. OFF In other words, if the input control signal S IN Instructs to turn off the power switch, and if the zero crossing control activation signal S ZCTRL With a zero-crossing control inactive value, the control signal generating circuit 220 can be connected to the zero-crossing detection signal S CZD The shutdown signal S is generated independently OFF , and there is no need to determine whether the timeout interval has expired. In order to receive the zero-crossing control activation signal S ZCTRL , the control signal generating circuit 220 can be coupled to the zero-crossing control terminal T of the gate driver 200 ZCTRL . Zero-crossing control activation signal S ZCTRL can be coupled to the gate driver 200 and can also provide an input control signal S IN A microcontroller or some other logic circuit system is provided.

[0026] In summary, in the case of receiving the zero-crossing control activation signal S according to the present disclosure ZCTRL In the example of the gate driver 200, the gate driver 200 can be controlled to switch between the following two: IN The power switch 100 is turned off when it is indicated that the power switch 100 is to be turned off, or the power switch 100 is turned off when the load current of the power switch 100 crosses zero or when the load current crosses zero within the timeout interval and the timeout interval expires. In other words, the activation signal S is controlled based on the zero crossing. ZCTRL , the gate driver 200 can controllably switch between hard switching and safe soft switching.

[0027] To implement the above-discussed functions of the control signal generating circuit 220 , the control signal generating circuit 220 may include a shutdown counter 221 , a first OR gate 222 , a first AND gate 223 , a second OR gate 224 , and a second AND gate 225 .

[0028] The shutdown counter 221 can be configured to: INThe shutdown counter 221 may generate a timeout signal S based on the counted time and the comparison result with the timeout interval. TO .

[0029] Based on the various signals discussed above, the first OR gate 222, the first AND gate 223, the second OR gate 224, and the second AND gate 225 can implement the following logic functions:

[0030]

[0031] Therefore, formula (1) shows that in order to realize the zero-crossing control activation signal S ZCTRL The above-discussed functions of the control signal generating circuit 220 are examples of the case where the zero-crossing control activation signal S is not implemented. ZCTRL , then formula (1) can be simplified as shown in formula (2):

[0032]

[0033] It will be understood that the implementation of the control signal generating circuit 220 with logic gates is provided only as an example. According to the principles discussed above, the functions discussed above can be implemented, for example, as program code executed by a microcontroller integrated into the gate driver 200 (which can be programmed into a field programmable gate array (FPGA)), or can be implemented by a controller suitable for generating the shutdown signal S OFF Any other type of circuit system may be implemented.

[0034] The gate driver 200 may further include an output stage 210. The output stage 210 may be configured to IN and the shutdown signal S OFF The gate driver control terminal T CTRL And thus the control terminal 100 C is coupled to one of the on-state voltage and the off-state voltage to generate an output control signal S CTRL The on-state voltage may be, for example, a voltage source coupled to the power supply voltage terminal T of the gate driver 200. SUP The voltage provided by the voltage source may exceed the threshold voltage of the power switch 100. The turn-off voltage may be, for example, the ground voltage GND. In order to realize the function of the output stage 210, the output stage 210 may include a turn-on transistor 211 and a turn-off transistor 212 arranged in a half-bridge configuration. The turn-on transistor 211 may receive an input control signal S at its control terminal. IN and can be coupled to the power supply voltage terminal T SUP and gate driver control terminal T CTRLThe turn-off transistor 212 may receive a turn-off signal S at its control terminal. OFF and can be coupled to the ground terminal T GND and gate driver control terminal T CTRL .

[0035] It will be appreciated that for simplicity, the control terminal of the turn-on transistor 211 is Figures 1B to 1D is shown as being directly coupled to the control input terminal T IN In some examples (not shown) of the present disclosure, the control terminal of the turn-on transistor 211 may be connected to the control input terminal T IN An intermediate element is coupled between the control terminal of the turn-on transistor 211 and the control input terminal T , for example, a logic circuit that provides additional functions of the gate driver. IN An intermediate logic circuit is arranged between the input control signal S IN After the instruction to turn off the switch 100 is given, the conduction transistor 211 may be kept in the on state until the control signal generation circuit 220 generates the turn-off signal S OFF Such logic may also be integrated in the control signal generating circuit 220. The conducting transistor 211 is kept in the on state until the off signal S is generated. OFF , avoiding the output control signal S CTRL The output terminal T CTRL The potential at may be in a floating state, which may occur when both the on transistor 211 and the off transistor 212 are not turned on.

[0036] In some examples of the present disclosure, the gate driver 200 may include galvanic isolation that separates the gate driver 200 into an input side and an output side, such that, for example, the gate driver 200 is electrically isolated from the control terminal 100 C With the first load terminal 100 L1 In the event of a failure of the isolation between the gate driver 200 and the gate driver 200, the components coupled to the input side are protected from the high voltage switched by the power switch 100. The input side may be an input terminal of the gate driver 200 coupled to the gate driver 200 that receives a signal from other logic circuits such as a microcontroller, i.e., a control input terminal T IN and zero-crossing control terminal T ZCTRL The output side may be the output terminal of the gate driver 200 coupled to the gate driver 200, that is, the control terminal T CTRL On one side. Figure 1C and Figure 1D The current isolation is shown by two vertical dashed lines. In such an example, the control signal generation circuit 220 can be as follows Figure 1Cis arranged on the input side as shown, or as Figure 1D Shown is arranged on the output side.

[0037] like Figure 1C As shown, if the control signal generating circuit 220 is arranged on the input side, the gate driver 200 may further include a circuit configured to transmit the shutdown signal S across the galvanic isolation. OFF The gate driver 200 may further include a circuit configured to transmit the input control signal S across the galvanic isolation. IN The input control signal is transmitted to the circuit 201. Figure 1C In the example of , the zero-crossing detection circuit 230 is arranged on the output side. Therefore, Figure 1C The gate driver 200 of the example further includes a circuit configured to transmit the zero-crossing detection signal S across the galvanic isolation ZCD In the example of the gate driver 200 in which the zero-crossing detection circuit 230 is arranged at the output side, the gate driver 200 may further include a circuit configured to transfer the load current signal S LC The load current signal is transmitted to the input side of the transmission circuit.

[0038] like Figure 1D As shown, if the control signal generating circuit 220 is arranged on the output side, the gate driver 200 may further include a circuit configured to transmit the zero-crossing control activation signal S across the current isolation. ZCTRL The zero-crossing control activation signal transfer circuit 204. In addition, Figure 1D The gate driver 200 may also include a gate driver configured to transmit an input control signal S across the galvanic isolation IN The input control signal is transmitted to the circuit 201.

[0039] about Figure 1C and Figure 1D The various signal transfer circuits shown and discussed in the present invention may be implemented, for example, using level shifters, optocouplers, or coreless transformers, or any other circuitry configured to transfer signals from one voltage domain to another across an isolation barrier.

[0040] By including the output stage 210, Figures 1A to 1D The example of the gate driver 200 corresponds to a gate driver that couples the control terminal of the driven switch to one of two voltages in response to a control signal. To illustrate that the above-discussed functionality of the control signal generating circuit 220 can also be used in a gate driver 200 implemented as a solid-state isolator, Figure 2 An example of a gate driver 200 implemented as a solid-state isolator is provided.

[0041] Figure 2The gate driver 200 is shown, which is configured to be based on the above description of the shutdown signal S OFF The discussed principle of generation is used to generate one of the on-voltage and the off-voltage.

[0042] Figure 2 The gate driver 200 includes a galvanic isolation barrier shown by a vertical dashed line. The transformer 260 crosses Figure 2 The gate driver 200 is coupled to a galvanic isolation barrier. Therefore, the gate driver 200 can be separated into an input side 240, i.e., a circuit system coupled to the primary side of the transformer 260, and an output side 250, i.e., a circuit system coupled to the secondary side of the transformer 260, by galvanic isolation and the transformer 260. The transformer 260 can be formed based on any type of galvanic isolation, such as a coreless transformer.

[0043] The input side 240 may include an input voltage source 241, an input switch 242, an input ground 243, an on-off keying (OOK) element 244, and a control signal generating circuit 220. The OOK element 244 may be coupled to the control input terminal T IN Between the control terminal of the input switch 242. By coupling the control input terminal T IN The OOK element 244 can be connected to the control terminal of the input switch 242 in response to the input control signal S IN In other words, as long as the input control signal S IN Indicating that the power switch 100 will be turned on, the OOK element 244 can generate an OOK signal. In addition, by being coupled to the control terminal of the input switch 242, the OOK element 244 can control the input switch 242 based on the OOK signal. When the input switch 242 is controlled to be in the on state based on the OOK signal, a magnetizing current can flow through the primary winding of the transformer 260. The magnetizing current flowing through the primary side of the transformer 260 can cause magnetic energy to be stored in the transformer 260, and thus can cause a voltage drop on the secondary side of the transformer 260. The voltage drop on the secondary side can be reversed relative to the voltage drop on the primary side of the transformer 260 caused by the input voltage source 241. Once the input switch 242 is controlled to no longer be in the on state based on the OOK signal, the magnetic energy stored in the transformer 260 can be released on the secondary side of the transformer 260, which causes a reverse voltage drop on the secondary side.

[0044] It will be understood that the input voltage source 241 is shown as being arranged at the input side 240 and thus inside the gate driver 200 only as an example. In some examples of the present disclosure, the input voltage source 241 may be provided externally. In such examples of the present disclosure, the input side 240 may include a terminal configured to be coupled to the input voltage source 241.

[0045] From the discussion of the input side 240, it can be seen that the input control signal S IN The gate driver 200 may be powered by causing the OOK element 244 to generate an OOK signal, which may cause a magnetizing current to flow through the primary side of the transformer 260. The magnetizing current flows through the primary side of the transformer 260, thereby causing energy to be released on the secondary side of the transformer 260. Therefore, in order to achieve the safety soft switching function discussed above, Figure 2 The control signal generating circuit 220 needs to input the control signal S IN After the power switch 100 is turned off, the OOK element 244 continues to generate the OOK signal. Figure 2 The control signal generating circuit 220 may be configured to: IN After instructing to turn off the power switch 100, power is provided to the gate driver 200 until a turn-off signal S is generated. OFF , that is, when the input control signal S IN After the power supply to the gate driver 200 is stopped, it is not until the load current of the power switch 200 crosses zero or until the timeout interval expires if the load current crosses zero without occurring during the timeout interval.

[0046] In order to input the control signal S IN After stopping power supply to the gate driver 200, power is supplied to the gate driver 200 until the load current of the power switch 200 crosses zero or until the timeout interval expires if the load current crosses zero without occurring during the timeout interval. The control signal generating circuit 220 may include a third OR gate 226, a third AND gate 227, and an input control signal latch 228.

[0047] The input control signal latch 228 can be coupled to the control input terminal T IN and OOK element 244. More specifically, the set input of the input control signal latch 228 can receive the input control signal S IN , and an input control signal S may be provided at the output of the input control signal latch 228 IN The output of the input control signal latch 228 can be coupled to the OOK element 244. Based on the input control signal S IN The latch value of the input control signal latch 228 can be IN After indicating that the power switch 100 is to be turned off, the OOK element 244 continues to provide the OOK signal to the control terminal of the input switch 242. TO To indicate that the power switch 100 is turned off if no zero crossing occurs during the timeout interval, a turn-off signal S may be provided to the reset input of the input control signal latch 228. OFF.in other words, Figure 2 In the example of the shutdown signal S OFF It can be a reset signal for input control signal latch 228. Figure 2 In the example, the shutdown signal S OFF It can be generated by the third OR gate 226 and the third AND gate 227, as shown in formula (3):

[0048]

[0049] It will be appreciated that based on the latch input control signal S IN The concept of the control signal generating circuit 220 is provided as an example only. In the context of the gate driver 200 being implemented as a solid-state isolator, the control signal generating circuit 220 can be configured in any of the following ways: the way is suitable for the input control signal S IN After stopping supplying power to the gate driver 200 , power is continuously supplied to the gate driver 200 until a zero crossing of the load current of the power switch 100 is detected or a timeout interval has expired without a zero crossing occurring.

[0050] The output side 250 may include a first diode 251, a second diode 252, a turn-off switch 253, a first buffer capacitor 254, a resistor 255, a second buffer capacitor 256, a zero-crossing detection circuit 230, and a zero-crossing detection signal transfer circuit 203. The first diode 251, the resistor 255, and the second buffer capacitor 256 may also be collectively referred to as a negative charge pump. The output side 250 may also include two output terminals T CTRL1 and T CTRL2 , which can be coupled to the control terminal 100 C and the second load terminal 100 L2 The zero-crossing detection circuit 230 and the zero-crossing detection signal transmission circuit 203 may have the above Figures 1A to 1D Functionality discussed.

[0051] When based on the input control signal S IN When the control signal generating circuit 220 controls the input switch 242 to cause a reverse voltage drop on the secondary side of the transformer 260, the second buffer capacitor 256 can be charged. The energy charged in the second buffer capacitor 256 can be used to charge the control terminal of the off switch 253, thereby turning on the off switch 253. When the off switch 253 is turned on, the control terminal 100 C and the second load terminal 100 L2In addition, since the reverse voltage on the secondary side of the transformer 260 makes the potential at the anode of the second diode 252 lower than the potential at the cathode of the second diode 252, the second diode 252 blocks the current from flowing to the control terminal 100. C .

[0052] Once based on the input control signal S IN Or the control signal generating circuit 220 controls the input switch 242 to no longer be in the on state, and the voltage on the secondary side of the transformer 260 is no longer reversed. Therefore, the second diode 252 can no longer prevent the current from flowing to the control terminal 100. C This allows the energy stored in the transformer 260 to be directed toward the control terminal 100. C The energy stored in the first buffer capacitor 254 can be discharged to the control terminal 100. C In addition, the second buffer capacitor 256 can be discharged during the release of the energy stored in the transformer 260, so that the control terminal of the disconnect switch 253 is also discharged and the disconnect switch 253 is not turned on. Therefore, the disconnect switch 253 can no longer connect the control terminal 100 to the on state. C Coupled to the second load terminal 100 L2 , so that the control terminal 100 C Charge.

[0053] Figure 3 A flow chart of a method of controlling a power switch 100 using a gate driver 200 is provided. For example, the method 300 may be performed by the control signal generating circuit 220 discussed above. The method 300 may start at step 301 where the power switch 100 may be in an off state.

[0054] At step 301, the method 300 may monitor an input control signal S IN Whether it indicates that the power switch 100 is to be turned on. If the input control signal S IN Indicates that the power switch 100 is to be turned on, then the method 300 continues to step 302. Otherwise, the power switch 100 remains in the off state, as indicated by the arrow pointing to step 308, which corresponds to the off state of the power switch 100.

[0055] At step 302 , the method 300 may be performed by, for example, providing a control terminal 100 based on the output stage 210 . C Provide an output control signal S that exceeds the threshold of the power switch 100 CTRL, or by turning on the power switch 100 by providing turn-on energy based on the first buffer capacitor 254 .

[0056] At step 303, the method 300 may monitor the input control signal S IN Whether it indicates that the power switch 100 will be turned off. If the input control signal S IN indicates that the power switch 100 is to be turned off, then the method 300 proceeds to step 304. Otherwise, the method remains at step 303 and continues to keep the power switch 100 turned on, as indicated by the arrow pointing to step 302.

[0057] At step 304 , the method 300 may check the zero-crossing control activation signal S ZCTRL Whether it has a zero-crossing control inactive value. If the zero-crossing control activation signal S ZCTRL With a zero-crossing control inactive value, the method 300 may proceed to step 308 and the power switch 100 may be turned off accordingly. ZCTRL With a zero-crossing control activation value, the method 300 may proceed to step 305 .

[0058] At step 305 , the method 300 may start the shutdown counter 221 to count the time that has passed since the input control signal indicated to shut down the power switch 100 . The method 300 may then proceed to steps 306 and 307 .

[0059] At step 306 , the method 300 may monitor the zero-crossing detection signal S ZCD In step 307, the method 300 can monitor the timeout signal S TO To monitor whether the shutdown counter 221 indicates that the timeout interval has passed. As will be understood from the above discussion of the safe soft switching function, steps 306 and 307 can be performed substantially simultaneously, as indicated by the arrows pointing from step 306 to step 307 and from step 307 to step 306. If step 306 determines that the zero-crossing detection signal S ZCD indicates that the load current crosses zero, or step 307 determines the timeout signal S TO Indicating that the timeout interval has elapsed, method 300 may proceed to step 308 to turn off power switch 100 .

[0060] The present invention can be further illustrated by the following examples.

[0061] In an example, a gate driver configured to control a power switch includes: a zero-crossing detection circuit configured to receive a load current signal indicating a load current of the power switch, detect a zero-crossing of the load current based on the received load current signal, and generate a zero-crossing detection signal based on the detected zero-crossing of the load current signal; and a control signal generation circuit coupled to the zero-crossing detection circuit and configured to receive an input control signal indicating turning on or off the power switch, generate a shutdown signal based on the zero-crossing detection signal if the input control signal indicates turning off the power switch, or determine whether a timeout interval has expired after indicating shutdown, generate a shutdown signal regardless of the zero-crossing detection signal if the timeout interval has expired, and provide the shutdown signal to a control terminal of the power switch.

[0062] In the example gate driver, to determine whether a timeout interval has expired after indicating shutdown, the control signal generating circuit 220 may also be configured to count time since indicating shutdown and compare the counted time with a time threshold that defines the timeout interval.

[0063] In an example gate driver, the control signal generating circuit may further be configured to: receive a zero-crossing control activation signal having a zero-crossing control activation value or a zero-crossing control inactivation value, and if the input control signal indicates to turn off the power switch and the zero-crossing control activation signal has a zero-crossing control inactivation value, generate a shutdown signal regardless of the zero-crossing detection signal, and without determining whether a timeout interval has expired.

[0064] An example gate driver may further include an input side and an output side separated from the input side by galvanic isolation, and a shutdown signal transfer circuit, wherein the control signal generation circuit may be arranged on the input side and the shutdown signal transfer circuit may be configured to transfer the shutdown signal from the input side to the output side.

[0065] In the example gate driver, the zero-crossing detection circuit may be disposed on the output side, and the example gate driver may further include a zero-crossing detection signal transfer circuit configured to transfer the zero-crossing detection signal from the output side to the input side.

[0066] In an example gate driver, the gate driver may further include an input side and an output side separated from the input side by galvanic isolation, and an input control signal transfer circuit, wherein the control signal generating circuit may be arranged on the input side, and the input control signal transfer circuit may be configured to at least transfer the input control signal from the input side to the output side.

[0067] In the example gate driver, the example gate driver may further include an input side and an output side separated from the input side by galvanic isolation and a transformer arranged across the galvanic isolation, the input control signal may be configured to provide power to the gate driver when indicating turning on the power switch, and the control signal generating circuit may be arranged on the input side and may further be configured to: if the input control signal indicates turning off the power switch, then provide power to the gate driver after the input control signal indicates turning off the power switch until a shutdown signal is generated.

[0068] In the example gate driver, the control signal generating circuit may be further configured to provide power if the zero-crossing control signal has a zero-crossing control activation value.

[0069] In the example gate driver, the zero-crossing detection circuit may be disposed on the output side, and the example gate driver may further include a zero-crossing detection signal transfer circuit configured to transfer the zero-crossing detection signal from the output side to the input side.

[0070] An example method for controlling a power switch using a gate driver may include receiving a load current signal indicating a load current of the power switch, detecting a zero crossing of the load current based on the received load current signal, generating a zero crossing detection signal based on detecting the zero crossing of the load current signal, receiving an input control signal indicating turning the power switch on or off, generating a shutdown signal based on the zero crossing detection signal if the input control signal indicates turning off the power switch, or determining whether a timeout interval has expired after indicating shutdown, generating a shutdown signal regardless of the zero crossing detection signal if the timeout interval has expired, and providing the shutdown signal to a control terminal of the power switch.

[0071] In an example method, determining whether a timeout interval has expired after indicating the shutdown may include counting a time since indicating the shutdown and comparing the counted time to a time threshold that defines the timeout interval.

[0072] The example method may also include receiving a zero-crossing control activation signal having a zero-crossing control activation value or a zero-crossing control inactivation value, and if the input control signal indicates to turn off the power switch and the zero-crossing control activation signal has the zero-crossing control inactivation value, generating a shutdown signal independently of the zero-crossing detection signal, and without determining whether a timeout interval has expired.

[0073] In an example method, the input control signal may be configured to provide power to the gate driver when indicative of turning on the power switch, and the method may further include providing power to the gate driver after the input control signal indicative of turning off the power switch until a turn-off signal is generated.

[0074] The foregoing description has been provided to illustrate a zero current turn-off driver with a safe turn-off function. It should be understood that this description is by no means meant to limit the scope of the present invention to the precise implementations discussed throughout the specification. Rather, those skilled in the art will appreciate that the examples of the present disclosure may be combined, modified or streamlined without departing from the scope of the present disclosure as defined by the appended claims.

Claims

1. A gate driver (200) configured to control a power switch (100), comprising: A zero crossing detection circuit (230) is configured to: Receiving a load current signal (S) indicating a load current of the power switch (100) LC ), Based on the received load current signal (S LC ) to detect the zero crossing of the load current, and Based on the load current signal (S LC ) to generate a zero-crossing detection signal (S ZCD ),as well as A control signal generating circuit (220) is coupled to the zero-crossing detection circuit (230) and is configured to: Receive an input control signal (S) indicating turning on or off the power switch (100) IN ), If the input control signal (S IN ) indicates to turn off the power switch, then: Based on the zero-crossing detection signal (S ZCD ) to generate a shutdown signal (S OFF ),or determining whether a timeout interval has expired after indicating the shutdown, If the timeout interval has expired, then the zero-crossing detection signal (S ZCD ) independently generates the shutdown signal (S OFF ),as well as The shutdown signal (S OFF ) is provided to the control terminal of the power switch.

2. The gate driver (200) according to claim 1, wherein: In order to determine whether a timeout interval has expired after indicating the shutdown, the control signal generating circuit (220) is further configured to: counting the time since the shutdown was indicated, and The counted time is compared to a time threshold, which defines the timeout interval.

3. The gate driver (200) according to claim 1 or 2, wherein: The control signal generating circuit (220) is further configured to: Receive a zero-crossing control activation signal (S) having a zero-crossing control activation value or a zero-crossing control inactivation value ZCTRL );as well as If the input control signal (S IN ) indicates to turn off the power switch (100) and if the zero-crossing control activation signal (S ZCTRL ) has the zero-crossing control inactive value, then with the zero-crossing detection signal (S ZCD ) independently of generating the shutdown signal (S OFF ), and there is no need to determine whether the timeout interval has expired.

4. The gate driver (200) according to any one of claims 1 to 3, wherein: The gate driver (200) further comprises an input side and an output side separated from the input side by galvanic isolation and a shutdown signal transmission circuit (202), wherein: The control signal generating circuit (220) is arranged on the input side, and The shutdown signal transmission circuit (202) is configured to transmit the shutdown signal (S OFF ) is transferred from the input side to the output side.

5. The gate driver (200) according to claim 4, wherein: The zero-crossing detection circuit (230) is arranged on the output side, and The gate driver (200) further includes a circuit configured to convert the zero-crossing detection signal (S ZCD ) is a zero-crossing detection signal transmission circuit (203) that transmits the signal from the output side to the input side.

6. The gate driver (200) according to any one of claims 1 to 3, wherein: The gate driver (200) further comprises an input side and an output side separated from the input side by galvanic isolation and an input control signal transfer circuit (201), wherein: The control signal generating circuit (220) is arranged on the output side, and The input control signal transmission circuit (201) is configured to at least transmit the input control signal (S IN ) is transferred from the input side to the output side.

7. The gate driver (200) according to any one of claims 1 to 3, wherein: The gate driver (200) further comprises an input side and an output side separated from the input side by galvanic isolation and a transformer (260) arranged across the galvanic isolation, The input control signal (S IN ) is configured to provide power to the gate driver (200) when instructing to turn on the power switch (100), and The control signal generating circuit (220) is arranged at the input side and is further configured to: if the input control signal (S IN ) indicates to turn off the power switch (100), then The input control signal (S IN ) indicates to turn off the power switch (100) and then provide power to the gate driver (200) until the turn-off signal (S OFF ).

8. The gate driver (200) according to claim 7, wherein: The control signal generating circuit (220) is further configured to: ZCTRL ) provides the power with the zero-crossing control activation value.

9. The gate driver (200) according to claim 7 or 8, wherein: The zero-crossing detection circuit (230) is arranged on the output side, and The gate driver (200) further includes a circuit configured to convert the zero-crossing detection signal (S ZCD ) is a zero-crossing detection signal transmission circuit (203) that transmits the signal from the output side to the input side.

10. A method (300) of controlling a power switch (100) using a gate driver (200), comprising: receiving a load current signal indicative of a load current of the power switch (100), Based on the received load current signal (S LC ) to detect the zero crossing of the load current, Based on the load current signal (S LC ) to generate a zero-crossing detection signal (S ZCD ); Receive (301) an input control signal (S) instructing to turn on or off the power switch (100) IN ), If (303) the input control signal (S IN ) indicates to turn off the power switch (100), then: Based on the zero-crossing detection signal (S ZCD ) to generate (306) a shutdown signal (S OFF );or determining (305, 307) whether a timeout interval has expired after indicating said shutting down; If the timeout interval has expired, then the zero-crossing detection signal (S ZCD ) independently generates (307) the shutdown signal (S OFF ),as well as The shutdown signal (S OFF ) is provided (308) to the control terminal (100) of the power switch (100) C ).

11. The method (300) of claim 10, wherein: Determining (305, 307) whether a timeout interval has expired after indicating the shut down includes: counting the time since the shutdown was indicated, and The counted time is compared to a time threshold, which defines the timeout interval.

12. The method (300) according to claim 10 or 11, further comprising: A zero crossing control activation signal (S) having a zero crossing control activation value or a zero crossing control inactivation value is received (304). ZCTRL );as well as If the input control signal (S IN ) indicates to turn off the power switch (100) and if the zero-crossing control activation signal (S ZCTRL ) has the zero-crossing control inactive value, then with the zero-crossing detection signal (S ZCD ) independently generates (304, 308) the shutdown signal (S OFF ), and there is no need to determine whether the timeout interval has expired.

13. The method (300) according to any one of claims 10 to 12, wherein: The input control signal (S IN ) is configured to provide power to the gate driver (200) when instructing to turn on the power switch (100), and The method (300) further comprises: IN ) indicates to turn off the power switch (100) and then provide power to the gate driver (200) until the turn-off signal (S OFF ).

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