A high-side switch design and driving method thereof

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 and a pull-down enhancement unit; and an over-voltage protection unit coupled between the power supply and a ground, configured to start working when a voltage between the power supply and the ground is greater than an over-voltage threshold voltage, and discharge the voltage between the power supply and the ground. The application also discloses an electronic device comprising the high-side switch and a driving method for protecting the 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 and a method for driving the high-side switch. 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 quickly turned off. Summary of the Invention

[0004] To address the technical problems existing in the prior art, this application proposes a high-side switch, including 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, whose first terminal is coupled to the power supply and receives the power supply signal of the high-side switch, and whose second terminal 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 and a pull-down enhancement unit, configured to pull down the control terminal voltage of the power transistor using the pull-down unit and / or the pull-down enhancement unit under the control of the undervoltage protection 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 the overvoltage threshold voltage.

[0005] Specifically, the control module further includes a drive unit configured to receive a 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 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; the pull-down enhancement unit includes a second controlled current source 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 third 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 active, and the third controlled current source starts to operate, pulling down the control electrode voltage of the power transistor. The pull-down enhancement unit includes a fourth 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 active, and the fourth controlled current source starts to operate, pulling down the control electrode voltage of the power transistor.

[0008] Specifically, the preset threshold includes a first sub-threshold and a second sub-threshold, the second sub-threshold being less than the first sub-threshold; the pull-down unit includes a fifth 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 first threshold, a first undervoltage protection signal is active, the fifth controlled current source starts working, and pulls down the control electrode voltage of the power transistor; the pull-down enhancement unit includes a sixth 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 second sub-threshold, a second undervoltage protection signal is active, the fifth controlled current source stops working, and the sixth controlled current source starts working; or when the power supply signal is lower than the second sub-threshold, the second undervoltage protection signal is active, the fifth controlled current source remains active, and the sixth controlled current source starts working.

[0009] Specifically, the current of the sixth controlled current source is greater than the current of the fifth controlled current source.

[0010] Specifically, the undervoltage detection unit includes a first comparator, the negative input of which is configured to receive the power signal, the positive input of which is configured to receive a first reference signal having the preset threshold, and the output of which is coupled to the control module.

[0011] Specifically, the undervoltage detection unit includes a second comparator and a third comparator. The negative input of the second comparator is configured to receive a power supply signal, the positive input is configured to receive a second reference signal having the first sub-threshold, and the output is coupled to the control module. The negative input of the third comparator is configured to receive a power supply signal, the positive input is configured to receive a third reference signal having the second sub-threshold, and the output is coupled to the control module.

[0012] 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.

[0013] This application also discloses an electronic device comprising a high-side switch as described above.

[0014] This application also discloses a driving method for protecting a high-side switch, including detecting whether the power supply voltage is lower than a preset threshold, wherein the preset threshold is higher than the turn-off voltage of the high-side switch; when the power supply voltage is lower than the preset threshold, activating undervoltage protection, and turning on a pull-down unit and / or a pull-down enhancement unit to pull down the control electrode voltage of the power transistor in the high-side switch.

[0015] Specifically, the preset threshold includes a first sub-threshold and a second sub-threshold, the second sub-threshold being lower than the first sub-threshold, but both being higher than the turn-off voltage of the high-side switch; when the power supply voltage is lower than the first sub-threshold, the pull-down unit is activated to pull down the control voltage of the power transistor in the high-side switch; when the power supply voltage is lower than the second sub-threshold, the pull-down unit is deactivated, and the pull-down enhancement unit is activated to pull down the control voltage of the power transistor in the high-side switch; or when the power supply voltage is lower than the second sub-threshold, the pull-down unit remains activated, and the pull-down enhancement unit is activated to pull down the control voltage of the power transistor in the high-side switch; wherein the pull-down capability of the pull-down enhancement unit is higher than the pull-down capability of the pull-down unit.

[0016] 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

[0017] The preferred embodiments of this application will now be described in further detail with reference to the accompanying drawings, wherein:

[0018] Figure 1AThis is a schematic diagram of an existing high-side switch circuit structure;

[0019] Figure 1B Is it like this? Figure 1A The timing diagram shown is for the operation of the high-side switching circuit.

[0020] Figure 2A This is a schematic diagram of the structure of a high-side switch according to an embodiment of this application;

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

[0022] Figure 2C Is it like this? Figure 2B The circuit timing diagram of the high-side switch in one embodiment is shown.

[0023] Figure 3A This is a schematic diagram of the circuit structure of a high-side switch according to another embodiment of this application;

[0024] Figure 3B Is it like this? Figure 3A The circuit timing diagram of the high-side switch of one embodiment is shown; and

[0025] 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

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] In the following detailed description, for ease of understanding, the level with zero potential will be described as ground potential.

[0031] 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.

[0032] 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 under the drive of the power supply Vin and the input voltage Vi, regulates the gate voltage of the power transistor M1 to control the turn-on and turn-off of the power transistor M1.

[0033] 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.

[0034] 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.

[0035] 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 has begun to descend.

[0036] 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.

[0037] 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.GS The 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.

[0038] Common solutions to address the above problems include, for example, coupling a voltage divider diode or a large-value voltage divider resistor between the ground potential of the external circuit and the ESD protection diode E1 of the high-side switch, using voltage division to prevent the ESD protection diode E1 from conducting, so that Vo is not clamped to the threshold voltage of the ESD protection diode E1.

[0039] 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.

[0040] To address the aforementioned technical problems, this application proposes a circuit design for a high-side switch. This design controls the rate of change of the output voltage to the load under specific conditions, effectively ensuring rapid discharge of the load current when the high-side switch malfunctions. The design also has lower manufacturing costs. Furthermore, 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] According to one embodiment of this application, the input terminal Vin of the high-side switch 200 receives a power signal, i.e., an input signal Vi, with a power supply voltage Vin during normal operation. In abnormal operating conditions, due to voltage changes caused by abnormal power signal, the high-side switch is powered by the voltage stored in the capacitor. Therefore, in the following description, the input signal Vi refers to the power signal received by the high-side switch 200 after an external power supply failure. The initial value of this power signal, or input signal Vi, is the power supply voltage of the external power supply, which gradually decreases over time, depending on factors such as the capacitance value in the external power supply.

[0046] 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.

[0047] 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 drop 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.

[0048] like Figure 2A As shown, the control module 202 may further include a pull-down enhancement unit 223. According to one embodiment, when the power supply is not abnormal, the pull-down enhancement unit 223 may not be disconnected from the pull-down unit 222. When the power supply experiences an abnormal operating state, the pull-down enhancement unit 223 is coupled to and operates with the pull-down unit 222. The control module 202 can receive the undervoltage protection signal SD output by the undervoltage detection unit 203. The pull-down enhancement unit 223 and the pull-down unit 222 together accelerate the pull-down speed of the gate-source voltage of the power transistor 201, enhancing the ability of the pull-down unit 222 to pull down the power transistor 201, ensuring that when Vi drops to V... OFF Previously, the gate-source voltage of power transistor 201 had already reached its threshold voltage Vth, ensuring that power transistor 201 could be turned off.

[0049] According to one embodiment of this application, the pull-down capability of the pull-down enhancement unit 223 can be 5-20 times that of the pull-down unit 222. According to another embodiment of this application, the pull-down capability of the pull-down enhancement unit 223 can be 10 times that of the pull-down unit 222. According to one embodiment of this application, since the pull-down enhancement unit 223 can enable the power transistor 201 to turn off faster, the capacitance of the power supply capacitor Cin can be less than 10uF, depending on actual production needs.

[0050] 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.

[0051] 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, etc., and the specific structure is determined according to actual production needs.

[0052] According to one embodiment of this application, during normal operation of the high-side switch 200, the undervoltage detection unit 203 receives the input signal Vi and detects the voltage state. When the voltage signal transmitted to the control module 202 drops to the undervoltage detection threshold voltage V... REF When the undervoltage detection unit 203 outputs an undervoltage protection signal SD to the control module 202, the pull-down unit 222 and the pull-down enhancement unit 223 start working after receiving the undervoltage protection signal SD, and the gate-source voltage of the power transistor 201 decreases under the control of the pull-down unit 222 and the pull-down enhancement unit 223.

[0053] 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 the source-drain voltage changes greatly. Therefore, the output signal Vo of high-side switch continues to decrease to a negative voltage.

[0054] According to one embodiment, 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, and a discharge path is formed between the source of the power transistor 201 and the ground network, allowing the load current to be discharged rapidly in a short time.

[0055] 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.

[0056] 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.

[0057] 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 high-side switch 200 includes a power transistor 201. The gate of the power transistor 201 is coupled to the control module 202, the first terminal is coupled to the input terminal Vin to receive the input signal Vi, and the second terminal is coupled to the inductive load L. The load current on the inductive load L is io. The enable signal EN is received by the control module 202 and remains at an active level, keeping the high-side switch 200 in operation.

[0058] According to one embodiment of this application, the control module 202 may include a drive unit 221, wherein the drive unit 221 may include a charge pump (not shown) for boosting the received input signal Vi to the drive voltage of the power transistor 201. According to one embodiment of this application, the drive voltage may be approximately 5V higher than Vi, depending on actual production requirements.

[0059] 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 of the power transistor 201, thereby turning off the power transistor 201. 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 201.

[0060] like Figure 2B As shown, the control module 202 may further include a pull-down enhancement unit 223 connected in parallel with the pull-down unit 222. The pull-down unit 223 may include a controlled current source i22 for accelerating the turn-off speed of the power transistor 201. One end of the controlled current source i22 is coupled to the gate of the power transistor 201, and the other end is coupled to the source of the power transistor 201.

[0061] According to one embodiment of this application, considering the impact of the high-side switch 200 circuit structure on EMI radiation, the design of the pull-down enhancement unit can be tailored to determine its parameters and configuration based on actual production needs. The current sources i22 and i21 in pull-down enhancement unit 223 and pull-down unit 222 should not be excessively large. According to one embodiment of this application, the current provided by current source i22 in pull-down enhancement unit 223 can be 5-20 times that of current source i21 in pull-down unit 222. According to one embodiment of this application, the current provided by current source i22 in pull-down enhancement unit 223 can be 10 times that of current source i21 in pull-down unit 222.

[0062] According to other embodiments of this application, the control module 202 may also include other circuits for coupling the gate of the power transistor 201 with the pull-down unit and / or the pull-down enhancement unit 223. This application does not limit this, and it can be determined according to actual production needs.

[0063] 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 the undervoltage detection threshold voltage V. REF The negative input terminal receives the input signal Vi. When the input signal Vi is less than the undervoltage detection threshold voltage V... REFAt this time, comparator 231 outputs an undervoltage protection signal SD to control module 202 to activate pull-down unit 222 and pull-down enhancement unit 223. According to other embodiments of this application, the undervoltage detection threshold voltage V... REF The value is determined based on actual production needs.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] like Figure 2B As shown, during normal operation of the control module 202, the voltage output by the drive unit 221 is transmitted to the gate of the power transistor 201; the control module 202 receives an undervoltage protection signal SD from the undervoltage detection unit 203, and the undervoltage detection unit 203 detects that the input signal Vi is lower than the undervoltage detection threshold voltage V. REF When the voltage is low, an undervoltage protection signal SD is sent to the control module 202. The control module 202 then activates the pull-down unit 222 and the pull-down enhancement unit 223. The controlled current sources i21 and i22 start working and together pull down the gate-source voltage V of the power transistor 201. GS This causes the power transistor 201 to turn off quickly.

[0068] According to one embodiment of this application, the control module 202 can simultaneously start the pull-down unit 222 and the pull-down enhancement unit 223 after receiving the undervoltage protection signal SD, so as to pull down the gate-source voltage of the power transistor 201 together. 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, the pull-down enhancement unit 223 accelerates the decrease rate of the gate-source voltage Vgs of the power transistor 201, ultimately clamping Vo to the discharge threshold voltage -Vz. In the following description of the high-side switch operation, the enable signal EN remains active. Specifically, it includes the following operating stages:

[0069] t0-t1: Normal working phase

[0070] 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 power transistor 201, causing the power transistor 201 to conduct. The output signal Vo is the same as the input signal Vi, which is a high level. The power transistor 201 is in the linear region, and the gate-source voltage is 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 of the power supply capacitor Cin are both consistent with the load current io.

[0071] According to one embodiment of this application, the voltage V stored in the power supply capacitor Cin at this time CIN Same as power supply Vin.

[0072] t1-t2: The start of abnormal operation

[0073] like Figure 2C As shown, 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.

[0074] t2-t3: Undervoltage protection phase

[0075] 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 enhancement unit 223 and the pull-down unit 222, pulling down the gate-source voltage V of the power transistor 201. GS .

[0076] According to one embodiment of this application, after the pull-down unit 222 and the pull-down enhancement unit 223 are turned on, the power transistor 201 discharges through the parasitic capacitance between the gate and source.

[0077] t3-t4: Transistor saturation stage

[0078] like Figure 2C As shown, under the action of pull-down enhancement unit 223 and pull-down unit 222, the gate-source voltage V of power transistor 201 is... GS When the input signal Vi drops to the switching off voltage V OFF Previously, the voltage dropped to the threshold voltage Vth, entering the transistor saturation stage. At this time, power transistor 201 is in the saturation region, and the gate-source voltage V... GS No significant changes occur, and the load current io can still freewheel through the power transistor 201, but due to the source-drain voltage V of the power transistor 201... DS A significant change occurs, and the input signal Vi and the output signal Vo are no longer equal. The output signal Vo decreases at a faster rate until it is clamped by an external clamping circuit, such as a Zener diode Z1. During this stage, the current iC of the power supply capacitor Cin in the discharge path and the current iMOS of the power transistor 201 are aligned with the load current io.

[0079] t4-t5: Clamping protection phase

[0080] 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 decreases to -Vz and remains constant, and the gate-source voltage V of the power transistor 201... GS When the voltage is pulled down to 0, power transistor 201 is in the off state. The discharged load current io no longer flows through power transistor 201 and power supply capacitor Cin, and iMOS and iC jump to 0. The load current io is now discharged through external Zener diode Z1 instead of power transistor 201. At this time, the value of input signal Vi is greater than V. OFF The current in Zener diode Z1 jumps from 0 to the value of the current load current io, and remains unchanged.

[0081] t5-t6: Switch-off phase

[0082] During the switch-off phase, such as Figure 2C As shown, the load current io drops to 0 after being discharged through the discharge path formed by the external clamping circuit. At this time, the high-side switch 200 is completely closed, the output signal Vo returns to 0, and no current flows through the inductive load L and the Zener diode Z1.

[0083] According to one embodiment of this application, when the pull-down enhancement unit 223 and pull-down unit 222 in the high-side switch 200 work together, the high-side switch 200 can turn off the power transistor 201 within 10µs. According to other embodiments of this application, the turn-off time can be less than 1µs. Under the action of pull-down unit 222 and pull-down enhancement unit 223, the rate at which the output signal Vo decreases can be greater than 2V / µs. When pull-down enhancement unit 223 is working, the size of the power supply capacitor Cin can also be reduced according to actual production needs. According to one embodiment of this application, the power supply capacitor Cin can be less than 10µF.

[0084] According to the embodiments of this application, the EMI radiation and corresponding noise interference generated by the pull-down enhancement unit 223 do not have a significant impact on the circuit itself and the actual operation of the device compared with the high-side switches of the prior art, and can be ignored.

[0085] According to one embodiment of this application, the high-side switch 200 can discharge the current in the inductive load L within 5ms, thereby turning off the corresponding relay. Compared with existing high-side switches, which typically require at least 40ms to completely turn off the relay, this significantly improves the safety of the system.

[0086] Figure 3A This is a schematic diagram of the circuit structure of a high-side switch according to another embodiment of this application. Figure 3A As shown, the high-side switch 300 may include components such as... Figure 2B The high-side switch 200 shown includes a power transistor 301, a control module 302, and an overvoltage protection unit 304 with the same or similar structure. Figure 2B The high-side switch 300 shown is identical to the one described above. Its input terminal Vin receives the power supply voltage, and its ground terminal Gc is directly coupled to the ground network, generating a ground potential of zero. In the following embodiment, the enable signal EN will remain active, keeping the high-side switch 300 operational.

[0087] According to one embodiment of this application, the high-side switch 300 includes a power transistor 301. The gate of the power transistor 301 is coupled to a control module 302, the first terminal receives an input signal Vi, and the second terminal is coupled to an inductive load L. A load current io is generated on the inductive load L that needs to be discharged after turn-off.

[0088] like Figure 3A As shown, the high-side switch 300 may further include an undervoltage detection unit 303, which includes comparators 331 and 332. The positive input terminal of comparator 331 receives a first undervoltage detection threshold voltage V. REF1 The negative input terminal receives the input signal Vi; the positive input terminal of comparator 332 receives the second undervoltage detection threshold voltage V. REF2The negative input terminal receives the input signal Vi.

[0089] According to one embodiment of this application, the second undervoltage detection threshold voltage V REF2 It can be less than the first undervoltage detection threshold voltage V REF1 Greater than the switch-off voltage V OFF The specific value will be determined based on actual production needs.

[0090] According to one embodiment of this application, during normal operation of the high-side switch 300, the undervoltage detection unit 303 receives the input signal Vi and detects the voltage status.

[0091] According to one embodiment of this application, the undervoltage detection unit 303 receives the input signal Vi when the input signal Vi begins to gradually decrease. When the input signal Vi is less than a first undervoltage detection threshold voltage V... REF1 At this time, comparator 331 outputs a first undervoltage protection signal SD1 to control module 303. Upon receiving SD1, control module 303 activates pull-down unit 322, and controlled current source i31 starts working, pulling down the gate-source voltage V of power transistor 301. GS At this time, the pull-down enhancement unit 323 is not activated. The input signal Vi continues to decrease until it is lower than the second undervoltage detection threshold voltage V. REF2 At this time, comparator 332 outputs a second undervoltage protection signal SD2 to control module 303. Upon receiving SD2, control module 303 activates pull-down enhancement unit 323. At this time, controlled current source i32 also starts working, and pull-down enhancement unit 323 and pull-down unit 322 together pull down the gate-source voltage V of power transistor 301. GS .

[0092] According to another embodiment of this application, when the control module 303 receives SD2, it can stop using the pull-down unit 322 and turn on the pull-down enhancement unit 223. At this time, the controlled current source i31 stops working, and the controlled current source i32 starts working, changing from the pull-down unit 322 to the pull-down enhancement unit 323 to pull down the gate-source voltage V of the power transistor 301. GS .

[0093] According to one embodiment of this application, the pull-down capability of the pull-down enhancement unit 323 can be 5-20 times that of the pull-down unit 322. According to another embodiment of this application, the pull-down capability of the pull-down enhancement unit 323 can be 10 times that of the pull-down unit 322. According to one embodiment of this application, the current provided by the controlled current source i32 in the pull-down enhancement unit 323 can be 5-20 times that of the controlled current source i31 in the pull-down unit 322. According to one embodiment of this application, the current provided by the controlled current source i32 in the pull-down enhancement unit 323 can be 10 times that of the controlled current source i31 in the pull-down unit 322.

[0094] Figure 3B Is it like this? Figure 3A The diagram shows the timing of the high-side switch circuit according to another embodiment. In the following description of the high-side switch's operation, the enable signal EN remains active. Specifically, the operation includes the following stages:

[0095] t0-t1: Normal working phase

[0096] like Figure 3B As shown, during the normal operation of the high-side switch 300, the power supply outputs a continuous and stable power voltage. The input terminal Vin receives the power voltage, and the control module 302 provides a drive voltage to the power transistor 301, causing the power transistor 301 to conduct. The output signal Vo is the same as the input signal Vi, which is a high level. The power transistor 301 is in the linear region, and the gate-source voltage is Vgs. The load current io flowing through the inductive load L is at iL. The current iMOS flowing through the power transistor 301 and the current of the power supply capacitor Cin are both consistent with the load current io.

[0097] According to one embodiment of this application, the voltage V stored in the power supply capacitor Cin at this time CIN Same as power supply Vin.

[0098] t1-t2: The start of abnormal operation

[0099] like Figure 3B As shown, 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 300. The high-side switch 300 is powered by an external power supply capacitor Cin, and its input terminal Vin receives the capacitor voltage V. CIN The input signal Vi is derived from V CIN The voltage 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 300 operate normally. Since the power transistor 301 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.

[0100] t2-t3: Undervoltage protection phase

[0101] When the input signal Vi drops to the first undervoltage detection threshold voltage V REF1 The voltage continues to drop, and the high-side switch 300 enters the undervoltage protection phase. The undervoltage detection unit 303 detects that the input signal Vi is lower than V. REF1 The system outputs an undervoltage protection signal SD1 to the control module 302. Upon receiving the undervoltage protection signal SD1, the control module 302 activates the pull-down unit 322 to pull down the gate-source voltage V of the power transistor 301.GS .

[0102] According to one embodiment of this application, after the pull-down unit 322 is turned on, the power transistor 301 discharges through the parasitic capacitance between the gate and source.

[0103] t3-t4: Enhanced undervoltage protection phase

[0104] When the input signal Vi drops to the second undervoltage detection threshold voltage V REF2 The voltage continues to drop, and the high-side switch 300 enters the undervoltage protection enhancement stage. The undervoltage detection unit 303 detects that the input signal Vi is lower than V. REF2 The system outputs an undervoltage protection signal SD2 to the control module 302. Upon receiving the undervoltage protection signal SD2, the control module 302 activates the pull-down enhancement unit 323.

[0105] At this time, pull-down enhancement unit 323 and pull-down unit 322 together pull down the gate-source voltage V of power transistor 301. GS Power transistor 301 discharges through the parasitic capacitance between its gate and source, resulting in a gate-source voltage V. GS It will decrease at a faster rate, taking less time to drop to the threshold voltage Vth and enter the cutoff phase.

[0106] According to another embodiment of this application, after the control module 302 receives the undervoltage protection signal SD2, it stops using the pull-down unit 322 and turns on the pull-down enhancement unit 323. At this time, the pull-down enhancement unit 323 pulls down the gate-source voltage V of the power transistor 301 alone. GS Because the pull-down capability of the pull-down enhancement unit 323 is greater than that of the pull-down unit 322, the gate-source voltage V of the power transistor 301 is... GS It will drop at a faster rate, taking less time to reach the threshold voltage Vth and enter the transistor saturation stage.

[0107] t4-t5: Transistor saturation stage

[0108] like Figure 3B As shown, under the action of pull-down enhancement unit 323 and pull-down unit 322, the gate-source voltage V of power transistor 301 is... GS When the input signal Vi drops to the switching off voltage V OFF Previously, the voltage dropped to the threshold voltage Vth, entering the transistor saturation stage. At this time, power transistor 301 is in the saturation region, and the gate-source voltage Vth... GS No significant changes occur, and the load current io can still freewheel through the power transistor 301, but due to the source-drain voltage V of the power transistor 301... DSA significant change occurs, and the input signal Vi and the output signal Vo are no longer equal. The output signal Vo decreases at a faster rate until it is clamped by an external clamping circuit, such as a Zener diode Z1. During this stage, the current iC of the power supply capacitor Cin in the discharge path and the current iMOS of the power transistor 301 are kept in line with the load current io.

[0109] t5-t6: Clamping protection phase

[0110] 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 decreases to -Vz and remains constant, and the gate-source voltage V of the power transistor 301... GS Pulled down to 0, power transistor 301 is in the off state. The discharged load current io no longer flows through power transistor 301 and power supply capacitor Cin, and iMOS and iC jump to 0. The load current io is now discharged through external Zener diode Z1 instead of power transistor 301. At this time, the value of input signal Vi is greater than V. OFF The current in Zener diode Z1 jumps from 0 to the value of the current load current io, and remains unchanged.

[0111] t6-t7: Switch-off phase

[0112] During the switch-off phase, such as Figure 3B As shown, the load current io drops to 0 after being discharged through the discharge path formed by the external clamping circuit. At this time, the high-side switch 300 is completely closed, the output signal Vo returns to 0, and no current flows through the inductive load L and the Zener diode Z1.

[0113] 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 source of the power transistor 401 can be grounded, and the control module 402 only controls the gate voltage of the power transistor 401.

[0114] 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.

[0115] According to one embodiment of this application, the gate of the power transistor 401 may be coupled to a pull-down unit 422 and / or a pull-down enhancement unit 423, and the gate voltage is pulled down by the pull-down unit 422 and / or the pull-down enhancement unit 423.

[0116] 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.

[0117] This application also discloses a driving method for protecting a high-side switch, the driving method comprising the following steps:

[0118] The system detects whether the power supply voltage is lower than a preset threshold, wherein the preset threshold is higher than the turn-off voltage of the high-side switch.

[0119] When the power supply voltage is lower than the preset threshold, undervoltage protection is activated, and the pull-down unit and / or pull-down enhancement unit are turned on to pull down the control electrode voltage of the power transistor in the high-side switch.

[0120] According to one embodiment of this application, the preset threshold includes a first sub-threshold and a second sub-threshold, wherein the second sub-threshold is lower than the first sub-threshold, but both are higher than the turn-off voltage of the high-side switch.

[0121] According to one embodiment of this application, when the power supply voltage is lower than the first sub-threshold, the pull-down unit is turned on to pull down the control electrode voltage of the power transistor in the high-side switch; when the power supply voltage is lower than the second sub-threshold, the pull-down unit is turned off and the pull-down enhancement unit is turned on to pull down the control electrode voltage of the power transistor in the high-side switch.

[0122] According to another embodiment of this application, when the power supply voltage is lower than the first sub-threshold, the pull-down unit is activated to pull down the control electrode voltage of the power transistor in the high-side switch; when the power supply voltage is lower than the second sub-threshold, the pull-down unit is kept in the activated state, and the pull-down enhancement unit is activated to pull down the control electrode voltage of the power transistor in the high-side switch.

[0123] According to an embodiment of this application, the pull-down enhancement unit has a higher pull-down capability than the pull-down unit.

[0124] By adopting the solution of this application, the speed at which the high-side switch turns off the power transistor and the current discharge of external loads, especially inductive loads, can be effectively improved when the power supply experiences abnormal operating conditions. Through the design and control of specific protection structures for specific situations, the impact of abnormal operating conditions on other modules of the overall circuit is reduced without generating interference and radiation that would significantly affect equipment operation. Simultaneously, the process and manufacturing costs of modifying the overall external circuitry to protect the high-side switch and some circuitry are reduced, making the protection method for the high-side switch more universally applicable.

[0125] 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, comprising: An undervoltage detection unit is configured to compare the power supply signal of the high-side switch with an undervoltage detection threshold and output an undervoltage protection signal based on the comparison result. When the power supply signal is lower than the undervoltage detection threshold, the undervoltage protection signal is effective. The undervoltage detection threshold is higher than the turn-off voltage of the high-side switch. When the power supply signal received by the high-side switch is lower than the switch turn-off voltage, the internal circuit of the high-side switch stops working. 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 is coupled to the control electrode of the power transistor and the undervoltage detection unit, respectively. The control module includes at least a pull-down unit and / or a pull-down enhancement unit. When the undervoltage protection signal is valid, the pull-down unit and / or the pull-down enhancement unit are configured to pull down the control electrode voltage of the power transistor, so that the voltage difference between the control electrode and its second electrode of the power transistor drops to at least the threshold voltage of the power transistor before the power supply signal drops to the switch off voltage. as well as 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, thereby discharging the voltage between the power supply and ground.

2. The high-side switch according to claim 1, wherein the control module further includes... A driving unit configured to receive the power signal and provide a driving voltage to the pull-down unit and the control electrode of the power transistor.

3. The high-side switch according to claim 2, 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 configured to pull down the control electrode voltage of the power transistor under the control of the control module. The pull-down enhancement unit includes a second controlled current source coupled between the control electrode and the second electrode of the power transistor, configured to pull down the control electrode voltage of the power transistor under the control of the control module.

4. The high-side switch according to claim 2, wherein the undervoltage detection threshold includes a first undervoltage detection sub-threshold and a second undervoltage detection sub-threshold, and the second undervoltage detection sub-threshold is less than the first undervoltage detection sub-threshold; The pull-down unit includes a third 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 first undervoltage detection threshold, the first undervoltage protection signal is effective, and the third controlled current source starts to work, pulling down the control electrode voltage of the power transistor. The pull-down enhancement unit includes a fourth 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 second undervoltage detection sub-threshold, the second undervoltage protection signal is active, the third controlled current source stops working, and the fourth controlled current source starts working; or When the power supply signal is lower than the second undervoltage detection threshold, the second undervoltage protection signal is effective, the third controlled current source remains in operation, and the fourth controlled current source starts to operate.

5. The high-side switch according to claim 4, wherein... The current of the fourth controlled current source is greater than the current of the third controlled current source.

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

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

8. The high-side switch according to claim 2 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.

9. An electronic device comprising a high-side switch as described in claims 1-8.

10. A driving method for protecting a high-side switch, comprising: The system detects whether the power supply voltage is lower than the undervoltage detection threshold, wherein the undervoltage detection threshold is higher than the turn-off voltage of the high-side switch. When the power supply signal received by the high-side switch is lower than the switch turn-off voltage, the internal circuit of the high-side switch stops working. When the power supply voltage is lower than the undervoltage detection threshold, undervoltage protection is activated, and the pull-down unit and / or pull-down enhancement unit are turned on to pull down the control electrode voltage of the power transistor in the high-side switch, so that the voltage difference between the control electrode and its second electrode of the power transistor drops to at least the threshold voltage of the power transistor before the power supply signal drops to the switch turn-off voltage.

11. The driving method according to claim 10, wherein The undervoltage detection threshold includes a first undervoltage detection sub-threshold and a second undervoltage detection sub-threshold. The second undervoltage detection sub-threshold is lower than the first undervoltage detection sub-threshold, but both are higher than the turn-off voltage of the high-side switch. When the power supply voltage is lower than the first undervoltage detection threshold, the pull-down unit is activated to pull down the control electrode voltage of the power transistor in the high-side switch; When the power supply voltage is lower than the second undervoltage detection threshold, the pull-down unit is turned off, and the pull-down enhancement unit is turned on to pull down the control voltage of the power transistor in the high-side switch; or When the power supply voltage is lower than the second undervoltage detection threshold, the pull-down unit is kept in the open state, and the pull-down enhancement unit is activated to pull down the control electrode voltage of the power transistor in the high-side switch. The pull-down enhancement unit has a higher pull-down capability than the pull-down unit.

Images