A high-side switch design

Abstract

The application relates to a high-side switch, comprising an under-voltage detection unit configured to compare a power supply signal of the high-side switch with a preset threshold value and output an under-voltage protection signal according to a comparison result; a power transistor, a first electrode of which is coupled with a power supply to receive the power supply signal of the high-side switch, and a second electrode of which is coupled with an external load; a control module coupled to a control electrode of the power transistor, which at least comprises a pull-down unit; a buffer module coupled between the power supply signal of the high-side switch and an input end of the control module, configured to receive the power supply signal and provide a buffered power supply signal to the control module; and an over-voltage protection unit coupled between the power supply and a ground, configured to start discharging a voltage between the power supply and the ground when the voltage between the power supply and the ground is greater than an over-voltage threshold voltage. The application further discloses an electronic device comprising the aforementioned high-side switch.

Description

Technical Field

[0001] This application relates to the field of electrical control, and in particular to a high-side switch design. Background Technology

[0002] High-side switches are a type of switching circuit widely used in manufacturing. They can save costs and achieve cost-effective high-current load control, and are widely used in electronic equipment such as automotive control and industrial lighting.

[0003] When the load driven by the high-side switch includes both inductive and resistive loads, a freewheeling current will still flow in the inductive load after the high-side switch is turned off. If the freewheeling current in the inductive load cannot stop within the required time period, the load, such as a relay, will not stop working within the required time period, potentially causing damage to external equipment or system circuits. In existing technologies, the safety issues caused by excessively long freewheeling current discharge time are often overlooked. Since this problem occurs more frequently under abnormal operating conditions, such as equipment failure or a car collision, failure to allow the freewheeling current to discharge completely and disconnect the relay within a short time may lead to serious consequences, such as battery fires. Compensation in external circuits may affect the normal operation of other circuits. Therefore, a high-side switch circuit is needed that can effectively ensure the rapid discharge of the freewheeling current in the inductive load without causing functional damage to the high-side switch and external equipment when the high-side switch malfunctions and needs to be turned off quickly. Summary of the Invention

[0004] To address the technical problems existing in the prior art, this application proposes a high-side switch, characterized by comprising: an undervoltage detection unit configured to compare the power supply signal of the high-side switch with a preset threshold and output an undervoltage protection signal based on the comparison result; a power transistor, the first terminal of which is coupled to a power supply and receives the power supply signal of the high-side switch, and the second terminal of which is coupled to an external load; a control module coupled to the control terminal of the power transistor, which includes at least a pull-down unit configured to pull down the control terminal voltage of the power transistor using the pull-down unit under the control of the undervoltage protection signal; a buffer module coupled between the power supply signal of the high-side switch and the input terminal of the control module, configured to receive the power supply signal and provide a buffered power supply signal to the control module when the power supply signal is lower than the power supply voltage provided by an external power supply, wherein the value of the buffered power supply signal is higher than the power supply signal; and an overvoltage protection unit coupled between the power supply and ground, configured to start working and discharge the voltage between the power supply and ground when the voltage between the power supply and ground is greater than an overvoltage threshold voltage.

[0005] Specifically, the control module further includes a drive unit configured to receive the buffered power signal and provide a drive voltage for the pull-down unit and the gate of the power transistor.

[0006] Specifically, the pull-down unit includes a first controlled current source, which is coupled between the control electrode and the second electrode of the power transistor and is controlled by the control module to pull down the control electrode voltage of the power transistor.

[0007] Specifically, the pull-down unit includes a first controlled current source coupled between the control electrode and the second electrode of the power transistor. When the power supply signal is lower than the preset threshold, the undervoltage protection signal is effective, and the first controlled current source starts to work, pulling down the control electrode voltage of the power transistor.

[0008] Specifically, the buffer module includes a first buffer diode and a first buffer capacitor connected in series. The anode of the first buffer diode is configured to receive the power signal, and the cathode is coupled to one end of the first buffer capacitor, the other end of the first buffer capacitor being grounded. The cathode of the first buffer diode is also coupled to the input terminal of the driving unit to output the buffered power signal to the driving unit.

[0009] Specifically, the undervoltage detection unit includes a comparator, the negative input of which is configured to receive the power signal, the positive input of which is configured to receive a reference signal having the preset threshold, and the output of which is coupled to the control module.

[0010] Specifically, the high-side switch also includes a diode, the anode of which is coupled to the second electrode of the power transistor, and the cathode of which is coupled to the control electrode of the power transistor.

[0011] Specifically, the buffer module includes a second buffer diode, the anode of which is configured to receive the power signal, and the cathode is coupled to the lead-out device; the cathode of the second buffer diode is also coupled to the input terminal of the driving unit, and outputs the buffered power signal to the driving unit; the cathode of the second buffer diode is configured to be coupled to one end of an off-chip second buffer capacitor, and the other end of the second buffer capacitor is grounded.

[0012] Specifically, the buffer module includes a built-in power supply (Vcc), a third buffer diode (Ep1), and a third buffer capacitor (Cp1). The anode of the third buffer diode (Ep1) is coupled to the anode of the built-in power supply (Vcc) and configured to receive the power signal. The cathode of the third buffer diode (Ep1) is coupled to the first terminal of the third buffer capacitor (Cp1), and the second terminal of the third buffer capacitor (Cp1) is coupled to the cathode of the built-in power supply (Vcc) through a first buffer switch (Sp1). The buffer module also includes a fourth buffer diode (Ep2) and a fourth buffer capacitor (Cp2). The anode of the fourth buffer diode (Ep2) is coupled to the cathode of the third buffer diode (Ep1), and the cathode of the fourth buffer diode (Ep2) is coupled to the cathode of the third buffer diode (Ep1). The first end of the fourth buffer capacitor (Cp2) is coupled, and the second end of the fourth buffer capacitor (Cp2) is coupled to the second end of the third buffer capacitor (Cp1) through the second buffer switch (Sp2). The second end of the fourth buffer capacitor (Cp2) is also coupled to the control module, configured to output the buffered power signal to the control module. When the clock signal is high, the first buffer switch (Sp1) is closed, the second buffer switch (Sp2) is open, and the third buffer capacitor (Cp1) stores power. When the clock signal is low, the first buffer switch (Sp1) is open, the second buffer switch (Sp2) is closed, the third buffer capacitor (Cp1) discharges, the fourth buffer capacitor (Cp2) stores power, and the buffered power signal is output to the control module.

[0013] This application also proposes an electronic device that includes a high-side switch as described above.

[0014] By adopting the solution of this application, the problems of the power transistor in the high-side switch failing to turn off in time when the external power supply is interrupted, and the output of the high-side switch failing to become negative to assist in the discharge of inductive load current, can be effectively improved. By designing and controlling specific protection structures for specific situations, the impact of abnormal operating states on other modules of the overall circuit is reduced, while the process and manufacturing costs of modifying the overall external circuit to protect the high-side switch and some circuits are reduced, making the protection method for the high-side switch more universally applicable. Attached Figure Description

[0015] The preferred embodiments of this application will now be described in further detail with reference to the accompanying drawings, wherein:

[0016] Figure 1A This is a schematic diagram of an existing high-side switch circuit structure;

[0017] Figure 1B Is it like this? Figure 1AThe timing diagram shown illustrates the circuit operation when the input voltage of the high-side switch decreases.

[0018] Figure 2A This is a schematic diagram of the structure of a high-side switch according to an embodiment of this application;

[0019] Figure 2B This is a schematic diagram of the circuit structure of a high-side switch according to an embodiment of this application;

[0020] Figure 2C Is it like this? Figure 2B The circuit timing diagram of the high-side switch in one embodiment is shown.

[0021] Figure 2D This is a schematic diagram of the circuit structure of a high-side switch according to another embodiment of this application;

[0022] Figure 3A This is a schematic diagram of the circuit structure of a high-side switch according to another embodiment of this application;

[0023] Figure 3B Is it like this? Figure 3A The schematic diagram of the buffer module circuit structure in the embodiment shown; and

[0024] Figure 4 This is a schematic diagram of the circuit structure of a high-side switch according to another embodiment of this application. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0026] In the following detailed description, reference can be made to the accompanying drawings, which form part of this application and illustrate specific embodiments of the present application. In the drawings, similar reference numerals describe substantially similar components in different figures. Specific embodiments of the present application are described in sufficient detail below to enable those skilled in the art to implement the technical solutions of the present application. It should be understood that other embodiments may also be utilized, or structural, logical, or electrical changes may be made to the embodiments of the present application.

[0027] A transistor can refer to any type of transistor, such as a field-effect transistor (FET) or a bipolar junction transistor (BJT). When a transistor is a field-effect transistor, depending on the channel material, it can be hydrogenated amorphous silicon, metal oxide, low-temperature polycrystalline silicon, organic transistors, etc. Based on whether the charge carriers are electrons or holes, they can be divided into N-type transistors and P-type transistors. The gate of a field-effect transistor is its control electrode; the first electrode can be the drain or source, and the corresponding second electrode can be the source or drain. When a transistor is a bipolar junction transistor (BJT), its control electrode is its base; the first electrode can be the collector or emitter, and the corresponding second electrode can be the emitter or collector.

[0028] In the following detailed description of logic levels, the effective level can be either high or low, depending on the circuit. In the following embodiments, for ease of understanding, a high level will be described as the effective level.

[0029] In the following detailed description, for ease of understanding, the level with zero potential will be described as ground potential.

[0030] In the detailed description below, depending on the actual operation of the circuit, positive voltages with opposite polarities can be generated across the same device. In some cases, the positive terminal of the voltage is ground potential. For ease of understanding, the voltage across the device that is opposite to the voltage when the device is operating normally will be described as a negative voltage.

[0031] A high-side switch is a type of load switch commonly used in electronic devices. Figure 1A This is a schematic diagram of an existing high-side switch circuit structure. For example... Figure 1A As shown, the high-side switch 100 includes at least a gate controller 101, an ESD protection diode E1, and a power transistor M1. During normal operation of the device, the gate controller 101 receives an enable signal EN and, driven by the power supply Vin and the input voltage Vi, regulates the gate voltage of the power transistor M1, thereby controlling the turn-on and turn-off of the power transistor M1.

[0032] During the use of electronic devices, some abnormal operating states may occur. A common example is that the power cord becomes loose during operation. In this case, the power supply Vin cannot continue to supply power to the high-side switch, and the capacitor Cin in the external circuit connected in parallel with the power supply will discharge, thus continuing to supply power to the high-side switch. Therefore, after the power supply Vin is disconnected, the input voltage Vi of the high-side switch will gradually decrease as the charge in the power supply capacitor Cin decreases. If the value of Cin is not large enough, the existing high-side switch 100 may experience potential clamping of the output voltage Vo due to the presence of the ESD protection diode E1, resulting in current still existing in the inductive load for a long time after Vin is disconnected. This could potentially damage external equipment or even cause serious safety accidents such as battery fires.

[0033] Figure 1B Is it like this? Figure 1A The timing diagram shown illustrates the operation of the high-side switching circuit. Figure 1B As shown, when the power supply is on and Vin is at an effective level, the circuit operates normally, the power transistor M1 operates in the linear region, and the gate-source voltage V of the power transistor M1 is... GS For Vgs; when a power supply malfunctions and Vin transitions to an invalid level, the input voltage Vi of the high-side switch becomes the voltage V supplied by the charge stored in the power supply capacitor Cin. CIN And it began to decline.

[0034] The power supply capacitor Cin stores a limited amount of charge, which may cause the input voltage Vi to drop relatively quickly. When the input voltage Vi drops to the undervoltage protection threshold V... UVLO The undervoltage protection function in the chip containing the high-side switch is activated, which causes the gate-source voltage V of the power transistor M1 to change. GS It begins to decrease. At this time, if the input voltage Vi is at the gate-source voltage V of the power transistor M1... GS Before falling to its threshold voltage Vth, it first drops to the switching off voltage V. OFF This will cause the gate-source voltages of other transistors in the gate controller 101 to fail to be biased to the correct operating state, making other circuits containing transistors malfunction. The switching off voltage V here... OFF This refers to a preset input voltage threshold during the operation of the high-side switch. When the input voltage Vi received by the high-side switch is lower than the switch turn-off voltage V... OFF If this happens, the internal circuitry of the high-side switch cannot continue to operate, and the corresponding gate controller 101 will also stop working and no longer control the power transistor M1.

[0035] Since the gate controller 101 can no longer control the power transistor M1, the gate-source voltage V of the power transistor M1 is reduced. GSThe voltage cannot decrease further, resulting in the gate-source voltage V of power transistor M1. GS As long as the voltage remains above Vth, power transistor M1 cannot be turned off. The output voltage Vo continues to decrease until it is clamped by the ESD protection diode E1. Since the output voltage Vo may become lower than the ground potential as it continues to decrease, the output voltage will be clamped by the ESD protection diode E1 to its threshold voltage -Vf, such as -0.7V. At this point, the output voltage Vo is insufficient to discharge the current of the inductive load in a short time, resulting in a long discharge time for the inductive load current, which does not meet the actual operating requirements of the device.

[0036] Common solutions to address the above problems include, for example, coupling a blocking diode or a large-value voltage divider resistor between the high-side switch's ground circuit and the high-side switch's ESD protection diode E1, so that the ESD protection diode E1 is not turned on and Vo is not clamped to the threshold voltage of the ESD protection diode E1.

[0037] However, this method involves improvements made outside the high-side switch, i.e., on the overall external circuitry. Voltage divider diodes or resistors are often placed within the ground network comprised of the device's overall ground circuit. Therefore, the ground potential output by the ground circuit prepared using this method may deviate, potentially affecting logic levels in the circuit, especially low levels, such as the determination of the input level of the enable signal EN. Furthermore, the addition of voltage divider diodes or resistors to the ground network may compromise its integrity, impacting chip heat dissipation through the ground network. In this case, Vo and Vi are equal; therefore, when Vo is negative, the input voltage Vi also becomes negative, potentially damaging other components connected in parallel with the power supply Vin, such as capacitors.

[0038] To address the aforementioned technical issues, this application proposes a circuit design for a high-side switch. By controlling the rate of change of the voltage output to the load, it effectively ensures rapid discharge of the load current when the high-side switch malfunctions. The process cost is relatively low, and since the protection structure for the switching circuit is located inside the switching circuit, it has less impact on external circuits and other components in the equipment.

[0039] According to one embodiment of this application, the external load of the high-side switch may include an inductive load and a resistive load. In practical applications, it is necessary to quickly discharge the current in the inductive load when the high-side switch is turned off. Therefore, this application provides the following embodiment.

[0040] Figure 2AThe diagram shown is a schematic representation of a high-side switch according to an embodiment of this application. According to one embodiment, the high-side switch 200 is a load switch applicable to electronic devices, capable of receiving an input signal Vi and an enable signal EN from an external source, and outputting a signal Vo to an external source. The high-side switch 200 includes an input terminal Vin and a ground terminal Gc.

[0041] According to one embodiment of this application, the ground terminal Gc can be directly coupled to the ground network in an external circuit, or it can be coupled to the ground network in an external circuit through other devices. The ground potential transmitted to the high-side switch 200 may be different depending on the connection method. The following description takes the ground potential of zero level generated by direct coupling as an example.

[0042] According to one embodiment of this application, the enable signal EN is used to externally control the operating state of the high-side switch 200. When the enable signal EN is active, the high-side switch 200 is turned on and remains active until the enable signal EN transitions to inactive. When the enable signal EN is inactive, the high-side switch 200 stops operating. In the following description of the embodiments, the enable signal EN will remain active, keeping the high-side switch 200 active.

[0043] According to one embodiment of this application, in normal operation, the input terminal Vin of the high-side switch 200 receives a power signal with a power supply voltage Vin, i.e., an input signal Vi. In abnormal operation, since the abnormal power signal causes voltage changes, the high-side switch is powered by the voltage stored in the capacitor. Therefore, in the following description, the input signal Vi is used to refer to the power signal of the high-side switch 200.

[0044] like Figure 2A As shown, the high-side switch 200 may include a power transistor 201 and a control module 202. The control module 202 controls the state of the power transistor 201 under the drive of the input signal Vi. The power transistor 201 generates an output signal Vo to drive an external load. According to one embodiment of this application, an external enable signal EN is received by the control module 202. According to one embodiment of this application, the control module 202 may include a drive unit 221. The output terminal of the drive unit 221 is coupled to the power transistor 201 so that the control module 202 controls the power transistor 201 to turn on and off. According to one embodiment of this application, the control module 202 may further include a pull-down unit 222, which is coupled to the output terminal of the drive unit 221. After receiving the signal output by the drive unit 221, the pull-down unit 222 pulls down the gate-source voltage of the power transistor 201, causing the power transistor 201 to turn off.

[0045] According to one embodiment of this application, the high-side switch 200 may further include an undervoltage detection unit 203, which is coupled to the control module 202. The undervoltage detection unit 203 detects an abnormality in the input signal Vi, such as a voltage below the undervoltage detection threshold voltage V. REF When the voltage is low, the undervoltage detection unit 203 will send an undervoltage protection signal SD to the control module 202, causing the high-side switch 200 to stop working.

[0046] According to one embodiment of this application, the high-side switch 200 may further include an overvoltage protection unit 204 coupled between the input terminal Vin and the ground terminal Gc. If, during operation, the voltage between the input terminal Vin and the ground terminal Gc exceeds the overvoltage threshold voltage of the overvoltage protection unit 204, the overvoltage protection unit 204 activates, discharging the voltage between the input terminal Vin and the ground terminal Gc to ensure the device functions normally and prevents the circuit from being burned out by excessive voltage.

[0047] According to one embodiment of this application, the high-side switch 200 may further include a buffer module 205 for buffering the decreasing input signal Vi when the power supply experiences an abnormal operating state, so that the operating state of the control module 202 and the power transistor 201 in the high-side switch 200 meets the requirement of rapidly discharging the load current. According to different embodiments of this application, the buffer module 205 may superimpose a portion of the voltage onto the input signal Vi when it decreases, and output a buffered voltage V. PB (Or, in other words, the buffered power signal) is therefore higher than the input signal Vi, V PB The output is sent to the drive unit 221. The buffered voltage V received by the control module 202 is buffered by the buffer module 205. PB Maintain the switching off voltage V until the power transistor 201 is turned off. OFF Above.

[0048] According to other embodiments of this application, the high-side switch 200 may also include other types of circuits, including but not limited to current detection circuits, fault reporting circuits, and over-temperature protection circuits, the specific structure of which is determined according to actual production needs.

[0049] According to one embodiment of this application, when the voltage signal transmitted to the control module 202 drops to the undervoltage detection threshold voltage V... REF Afterwards, the undervoltage detection unit 203 outputs an undervoltage protection signal SD to the control module 202. After receiving the undervoltage protection signal SD, the pull-down unit 222 starts to work, and the gate-source voltage of the power transistor 201 decreases under the control of the pull-down unit 222.

[0050] As the gate-source voltage of power transistor 201 decreases, the output signal Vo of high-side switch 200 gradually decreases. When the gate-source voltage of power transistor 201 drops to its threshold voltage Vth, the power transistor enters the saturation region, and a small current flows through power transistor 201. Its gate-source voltage does not change much, but its source-drain voltage changes significantly. Therefore, the output signal Vo of high-side switch continues to decrease to a negative voltage.

[0051] According to one embodiment of this application, the output signal Vo is fixed at the discharge threshold voltage (e.g., -Vz) by an external clamping circuit. When the output signal Vo is clamped to the discharge threshold voltage, a large potential difference is formed between the output signal Vo and the ground potential, forming a discharge path between the external protection circuit that clamps the output signal Vo to the discharge threshold voltage and the ground network, allowing the load current to be discharged rapidly in a short time.

[0052] According to one embodiment of this application, the load can be coupled to an external voltage regulator circuit (not shown), which may include a Zener diode (not shown), and the discharge threshold voltage may be the threshold voltage Vz of the Zener diode.

[0053] According to one embodiment of this application, a power supply capacitor Cin connected in parallel with the power supply may be provided outside the high-side switch 200. When the power supply voltage Vin is abnormal, the power supply capacitor Cin provides the input signal Vi.

[0054] Figure 2B This is a schematic diagram of the circuit structure of a high-side switch according to an embodiment of this application. Figure 2B As shown, the buffer module 205 may include a buffer capacitor Cbuffer and a diode E21 connected in series. The anode of E21 is configured to receive the input voltage Vi, the cathode is coupled to one end of Cbuffer, and the other end of Cbuffer is coupled to ground Gc. The cathode of diode E21 is also coupled to the input terminal of the drive unit 221, outputting a buffer voltage V. PB The enable signal EN is received by the control module 202 and remains at a valid level, keeping the high-side switch 200 in the working state.

[0055] According to an embodiment of this application, the ability of the buffer module 205 to superimpose the input signal Vi is related to the threshold voltage of the power transistor 201 and the amount of charge stored in the buffer capacitor Cbuffer. According to one embodiment of this application, the control module 202 may include a drive unit 221 for receiving the buffer voltage V from the buffer module 205. PB Rise to V CPB According to one embodiment of this application, V CPB Can be compared to V PBThe voltage is approximately 5V, depending on actual production needs. According to one embodiment of this application, the drive unit 221 may include a charge pump (not shown).

[0056] According to one embodiment of this application, in an abnormal operating state, as the input signal Vi decreases, V CPB Maintain the switch off voltage V OFF The above time, that is, the time for powering the control module 202 to operate normally and for turning off the power transistor 201 to be greater than 20µs. During this period, the power transistor 201 will be turned off by the control module 202.

[0057] According to one embodiment of this application, the control module 202 may further include a pull-down unit 222 coupled between the gate and source of the power transistor 201, wherein the pull-down unit 222 may include a controlled current source i21 for pulling down the gate-source voltage V of the power transistor 201. GS This turns off power transistor 201. For example... Figure 2B As shown, one end of the controlled current source i21 is coupled to the gate of the power transistor 201, and the other end is coupled to the source of the power transistor.

[0058] According to one embodiment of this application, the high-side switch 200 may further include an undervoltage detection unit 203, which may include a comparator 231. The positive input terminal of the comparator 231 receives an undervoltage detection threshold voltage V. REF The negative input terminal receives the input voltage Vi. When the input signal Vi is less than the undervoltage detection threshold voltage V... REF At this time, comparator 231 outputs an undervoltage protection signal SD to control module 202 to activate pull-down unit 222. According to other embodiments of this application, the undervoltage detection threshold voltage V... REF The value is determined based on actual production needs.

[0059] According to one embodiment of this application, the overvoltage protection unit 204 may further include an ESD protection diode E21. The cathode of the diode E21 receives the input signal Vi, and the anode is coupled to the ground terminal Gc. When the voltage between the input signal Vi received by the high-side switch 200 and the ground terminal Gc is greater than the overvoltage threshold voltage, the diode E21 will break down. At this time, the voltage between the input terminal Vin and the ground terminal Gc will be discharged through the diode E21.

[0060] According to one embodiment of this application, the overvoltage threshold voltage of the overvoltage protection unit 204 can be the breakdown voltage of the ESD protection diode E21.

[0061] According to other embodiments of this application, the overvoltage protection unit 204 may also include a Zener diode circuit (not shown) composed of two diodes or other circuit structures to protect the circuit from overvoltage. The specific circuit structure is not limited in this application and can be determined according to actual production needs.

[0062] According to one embodiment of this application, the load L connected to the output terminal of the high-side switch can be coupled to an external voltage regulation and protection circuit, such as a Zener diode Z1, to prevent the current remaining in the circuit after the high-side switch 200 is turned off from damaging the high-side switch 200 and other circuits.

[0063] like Figure 2B As shown, after the power transistor 200 is turned off, the current in the load L is discharged through the path formed by the Zener diode Z1 and the ground network, clamping the voltage of the output signal Vo of the high-side switch 200 to the discharge threshold voltage. According to an embodiment of this application, the value of the discharge threshold voltage can be the threshold voltage of the Zener diode Z1 - Vz.

[0064] Figure 2C Is it like this? Figure 2B The circuit timing diagram of the high-side switch in one embodiment is shown. Figure 2C As shown, buffer module 205 can slow down V PB The rate of decrease, thereby ensuring the gate-source voltage V of power transistor 201. GS The voltage can drop to the threshold voltage Vth within a predetermined time period, eventually clamping Vo to the discharge threshold voltage -Vz. In the following description of the high-side switch's operation, the enable signal EN remains active. Specifically, it includes the following operating stages:

[0065] t0-t1: Normal working phase

[0066] like Figure 2C As shown, during the normal operation of the high-side switch 200, the power supply outputs a continuous and stable power voltage. The input terminal Vin receives the power voltage, and the control module 202 provides a drive voltage to the gate of the power transistor 201, turning it on. The output signal Vo is the same as the input signal Vi, which is high. The power transistor 201 is in the linear region, with a gate-source voltage of Vgs. The load current io flowing through the inductive load L is at iL. The current iMOS flowing through the power transistor 201 and the current in the power supply capacitor Cin are both consistent with the load current io.

[0067] According to one embodiment of this application, the voltage V stored in the power supply capacitor Cin is at this time CIN Same as power supply Vin.

[0068] t1-t2: The start of abnormal operation

[0069] During the initial stage of abnormal operation, the power supply is disconnected, and a stable voltage is no longer supplied to the high-side switch 200. The high-side switch 200 is powered by an external power capacitor Cin, and its input terminal Vin receives the capacitor voltage V. CIN The input signal Vi is derived from V CIN The input signal Vi gradually decreases. Although the input signal Vi is gradually decreasing, it remains within the normal operating voltage range, and other devices within the high-side switch 200 operate normally. Since the power transistor 201 is still in the on state, the output signal Vo is the same as the input signal Vi and gradually decreases. The load current io, influenced by the power supply Vin, begins to gradually decrease. The values ​​of iMOS and iC are consistent with the load current io.

[0070] t2-t3: Undervoltage protection phase

[0071] like Figure 2C As shown, when the input signal Vi drops to the undervoltage detection threshold voltage V REF The voltage continues to drop, and the high-side switch 200 enters the undervoltage protection phase. The undervoltage detection unit 203 detects that the input signal Vi is lower than V. REF The system outputs an undervoltage protection signal SD to the control module 202. Upon receiving the undervoltage protection signal SD, the control module 202 activates the pull-down unit 222, pulling down the gate-source voltage V of the power transistor 201. GS .

[0072] According to one embodiment of this application, the buffer module 205 superimposes the input signal Vi to provide a buffer voltage V for powering the control module 202. PB The rate of decrease is less than that of the input signal Vi. Therefore, when the input signal Vi is already below the switch turn-off voltage V... OFF Afterwards, the control module 202 can still work normally, and the power transistor 201 is turned off under the control of the undervoltage protection signal SD.

[0073] According to an embodiment of this application, the buffer voltage V PB Maintain the switching off voltage V until the power transistor 201 is turned off. OFF Above, V PB The rate of decrease is related to the parameters of the buffer capacitor Cbuffer, which are determined according to actual production needs.

[0074] t3-t4: Transistor saturation stage

[0075] The gate-source voltage V of power transistor 201 GS Driven by the control module 202, the voltage gradually decreases to the threshold voltage Vth, entering saturation. At this time, the gate-source voltage V of the power transistor... GS It remained near Vth for a period of time.

[0076] In saturation state, the gate-source voltage V GS Although the source-drain voltage V does not change significantly with the current flowing through the power transistor 201, DS It will change significantly with the magnitude of the current. As the load current io flowing through the power transistor 201 gradually decreases, the source potential of the power transistor 201 is much higher than that of the drain, forming a large source-drain voltage, so that Vi and Vo are no longer equal; at this time, the load current io can still be discharged through the power transistor 201.

[0077] Vi continues to decrease gradually as the power supply capacitor Cin discharges. Since the source of power transistor 201 is higher than its drain, Vo decreases after passing through the source-drain voltage V. DS It then falls below Vi. As the load current io discharges, the source-drain voltage V... DS As it gradually increases, Vo decreases at a faster rate than Vi.

[0078] t4-t5: Anomaly Protection Phase

[0079] Because current still exists in the load, the input signal Vi continues to be pulled down after dropping to 0, until it reaches the threshold voltage -Vf of the ESD protection diode 204. Then, because the voltage between ground and Vi is greater than the threshold voltage of the ESD protection diode 204, the ESD protection diode 204 conducts, clamping the input voltage Vi to -Vf. At this time, the load current io is discharged through the ESD protection diode 204, and the power supply capacitor Cin no longer carries the load current discharge, causing the current iC to jump to 0. Since the power transistor 201 is in the off state, the output signal Vo is not affected by the input signal Vi, and Vo continues to decrease while Vi is clamped to -Vf by the ESD protection diode 204.

[0080] t5-t6: Clamping protection phase

[0081] As the current in the load continues to discharge through the power transistor, the output signal Vo continues to decrease until it is clamped to the Zener diode's threshold voltage -Vz by the external Zener diode Z1. At this point, Vo drops to -Vz and remains constant, and the gate-source voltage V of the power transistor 201... GS The current is pulled down to 0, turning off power transistor 201. The load current io no longer flows through power transistor 201, and the iMOS jumps to 0. The load current is now discharged through Zener diode Z1 instead of ESD protection diode 204, and the input voltage Vi, clamped to -Vf, returns to 0. The current in Zener diode Z1 jumps from 0 to the current value of the load current io.

[0082] t6-t7: Switch-off phase

[0083] During the switch-off phase, such as Figure 2C As shown, the load current io is discharged to 0 through the discharge path formed by the external clamping circuit structure. At this time, the high-side switch 200 is completely closed, the output voltage Vo returns to 0, and no current flows through the inductive load L and the Zener diode Z1.

[0084] According to one embodiment of this application, the response time of the high-side switch 200 from the occurrence of an abnormal operating state to the completion of load current discharge can reach about 5ms, which is significantly shortened compared with the time taken by the traditional high-side switch to turn off the inductive load, effectively improving the time required for inductive load current discharge in the circuit.

[0085] Figure 2D This is a schematic diagram of the circuit structure of a high-side switch according to another embodiment of this application. According to one embodiment of this application, the buffer module 205 may include a node (not shown) capable of coupling to an external device. This node is coupled to an external circuit, such as a buffer capacitor Cbuffer integrated outside the high-side switch 200, to buffer the input signal Vi and provide a buffer voltage V to the drive unit 221. PB The external buffer capacitor Cbuffer is coupled to the buffer module 205 and the ground network, respectively.

[0086] According to one embodiment of this application, since the capacitor used for buffering is integrated outside the high-side switch 200 rather than inside the switch, it is not limited by the manufacturing process of the switch circuit, thereby storing more charge, having a stronger buffering capacity for the input signal Vi, and providing power to the control module 202 for a longer period of time.

[0087] According to one embodiment of this application, the buffer capacitor Cbuffer integrated outside the high-side switch 200 can reach the uF level, while the capacitor integrated inside the high-side switch 200 cannot exceed the pF level.

[0088] Figure 3A This is a circuit structure diagram of a high-side switch according to yet another embodiment of this application, and Figure 3B Is it like this? Figure 3A The schematic diagram of the buffer module circuit structure in the embodiment shown.

[0089] According to one embodiment of this application, the high-side switch 300 may include a buffer module 305 that receives an enable signal EN and an input signal Vi, such as... Figure 3B As shown, it is used to buffer the decreasing input signal Vi and provide the drive voltage V to the control module 302. CPB .like Figure 3A As shown, the driving voltage of the power transistor 301 is provided by the buffer module 305, and the pull-down unit 322 is coupled to the buffer module 305.

[0090] According to one embodiment of this application, such as Figure 3B As shown, the buffer module 305 may include a built-in power supply Vcc, a buffer diode Ep1, and a buffer capacitor Cp1. The anode of the buffer diode Ep1 is coupled to the anode of the built-in power supply Vcc and receives the input signal Vi. The cathode of the buffer diode Ep1 is coupled to the first terminal of the buffer capacitor Cp1, and the second terminal of the buffer capacitor Ep1 is coupled to the cathode of the built-in power supply Vcc through a buffer switch Sp1.

[0091] According to one embodiment of this application, the buffer module 305 may further include a buffer diode Ep2 and a buffer capacitor Cp2. According to one embodiment of this application, the anode of the buffer diode Ep2 is coupled to the cathode of the buffer diode Ep1, and the cathode is coupled to the first terminal of the buffer capacitor Cp2. The second terminal of the buffer capacitor Cp2 is coupled to the second terminal of the buffer capacitor Cp1 via a buffer switch Sp2. The second terminal of the buffer capacitor Cp2 is also coupled to the control module 302 and configured to output a drive voltage V to the control module 302. CPB .

[0092] According to one embodiment of this application, diodes Ep1 and Ep2 are both used to prevent reverse current flow, and buffer drive capacitors Cp1 and Cp2 are used to superimpose Vi to obtain the drive voltage V. CPB (Or, in other words, a buffered power signal) causes the drive voltage V to... CPB It can drive the power transistor 301 to work normally.

[0093] According to one embodiment of this application, the buffer module 305 starts after receiving an enable signal EN from the outside, and switches sp1 and sp2 are controlled to close alternately by the clock signal from the control module 302 to achieve buffering and superposition of the input signal Vi.

[0094] According to one embodiment of this application, during normal operation of the high-side switch 300, when the clock signal CLK is high, switch sp1 is closed and sp2 is open, and Cp1 stores the voltage Vcp1 from the voltage source Vcc and the input signal Vi. When the clock signal CLK is low, sp2 is closed and sp1 is open, Cp1 discharges, and Cp2 receives the Vcp1 released by Cp1 and the voltage Vcp2 generated by the input signal Vi. When the input signal Vi begins to decrease, Cp2 outputs a driving voltage V higher than the input signal Vi. CPB Current mirror 323. At this time, the drive voltage V... CPB =Vi+Vcp2.

[0095] According to one embodiment of this application, the buffer drive capacitors Cp1 and Cp2 can be larger than 100pF. According to an embodiment of this application, the buffer module 305 can supply power to the control module 302, enabling it to maintain normal operation for a time greater than 10µs, which meets actual production requirements.

[0096] Figure 4 This is a schematic diagram of the circuit structure of a high-side switch according to another embodiment of this application. According to one embodiment of this application, the pull-down unit 422 can be coupled to the gate of the power transistor 401 at one end and grounded at the other end, and the control module 402 only controls the gate of the power transistor 401.

[0097] like Figure 4 As shown, the anode of diode E42 is coupled to the source of power transistor 401, and the cathode is coupled to the gate of power transistor 401. At V... G V S When much lower for V GS Clamping is performed to prevent the gate-source voltage V of power transistor 401 from being applied. GS Overvoltage caused damage to power transistor 401.

[0098] According to one embodiment of this application, the gate of the power transistor 401 can be coupled to the pull-down unit 422, and the gate voltage is pulled down by the pull-down unit 422.

[0099] This application also discloses an electronic device comprising the high-side switch as described above. The electronic device further includes other necessary modules and accessories to achieve other complex functions. According to one embodiment of this application, the electronic device can quickly shut off the high-side switch in the event of a power abnormality, such as a loose power cord, thereby discharging current from the load circuit in a short time and providing high safety.

[0100] By adopting the solution of this application, the speed at which the high-side switch turns off the power transistor and discharges the current of external loads, especially inductive loads, can be effectively improved when abnormal operating conditions occur. Through the design and control of the protection structure, the impact of abnormal operating conditions on other modules of the overall circuit is reduced, while the process and manufacturing costs of modifying the overall external circuit to protect the high-side switch and some circuits are reduced, making the protection method for the high-side switch more universally applicable.

[0101] The above embodiments are for illustrative purposes only and are not intended to limit the scope of this application. Those skilled in the art can make various changes and modifications without departing from the scope of this application. Therefore, all equivalent technical solutions should also fall within the scope of this application.

Claims

1. A high-side switch, characterized in that, include: The undervoltage detection unit is configured to compare the power signal of the high-side switch with a preset threshold and output an undervoltage protection signal based on the comparison result. The power transistor has its first terminal coupled to the power supply to receive the power signal from the high-side switch, and its second terminal coupled to an external load. A control module, coupled to the control electrode of the power transistor, includes at least a pull-down unit configured to pull down the control electrode voltage of the power transistor under the control of the undervoltage protection signal; A buffer module, coupled between the power signal of the high-side switch and the input terminal of the control module, is configured to receive the power signal and provide a buffered power signal to the control module when the power signal is lower than the power voltage provided by the external power supply, wherein the value of the buffered power signal is higher than the power signal. An overvoltage protection unit, coupled between the power supply and ground, is configured to activate when the voltage between the power supply and ground exceeds an overvoltage threshold voltage, thereby discharging the voltage between the power supply and ground. in The buffer module includes a built-in power supply (Vcc), a third buffer diode (Ep1), and a third buffer capacitor (Cp1). The anode of the third buffer diode (Ep1) is coupled to the anode of the built-in power supply (Vcc) and configured to receive the power signal. The cathode of the third buffer diode (Ep1) is coupled to the first terminal of the third buffer capacitor (Cp1), and the second terminal of the third buffer capacitor (Cp1) is coupled to the cathode of the built-in power supply (Vcc) through a first buffer switch (Sp1). The buffer module further includes a fourth buffer diode (Ep2) and a fourth buffer capacitor (Cp2). The anode of the fourth buffer diode (Ep2) is coupled to the cathode of the third buffer diode (Ep1). The cathode of the fourth buffer diode (Ep2) is coupled to the first terminal of the fourth buffer capacitor (Cp2). The second terminal of the fourth buffer capacitor (Cp2) is coupled to the second terminal of the third buffer capacitor (Cp1) through a second buffer switch (Sp2). The second terminal of the fourth buffer capacitor (Cp2) is also coupled to the control module and configured to output the buffered power signal to the control module.

2. The high-side switch according to claim 1, wherein, The pull-down unit includes a first controlled current source, which is coupled between the control electrode and the second electrode of the power transistor and is controlled by the control module to pull down the control electrode voltage of the power transistor.

3. The high-side switch according to claim 2, wherein, The pull-down unit includes a first controlled current source coupled between the control electrode and the second electrode of the power transistor. When the power supply signal is lower than the preset threshold, the undervoltage protection signal is effective, and the first controlled current source starts to work, pulling down the control electrode voltage of the power transistor.

4. The high-side switch according to claim 1, wherein, The undervoltage detection unit includes a comparator, the negative input of which is configured to receive the power signal, the positive input of which is configured to receive a reference signal having the preset threshold, and the output of which is coupled to the control module.

5. The high-side switch according to claim 1 further includes a diode, the anode of which is coupled to the second electrode of the power transistor, and the cathode of which is coupled to the control electrode of the power transistor.

6. The high-side switch according to claim 1, wherein, When the clock signal is high, the first buffer switch (Sp1) is closed, the second buffer switch (Sp2) is open, and the third buffer capacitor (Cp1) stores electricity. When the clock signal is low, the first buffer switch (Sp1) is open, the second buffer switch (Sp2) is closed, the third buffer capacitor (Cp1) is discharged, the fourth buffer capacitor (Cp2) stores electricity, and outputs a buffered power signal to the control module.

7. The high-side switch according to claim 1, wherein, The third buffer capacitor (Cp1) and / or the fourth buffer capacitor (Cp2) are greater than 100pF.

8. An electronic device comprising a high-side switch as described in any one of claims 1-7.

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