Open circuit detection circuit of high-side switch

Abstract

According to the open circuit detection circuit of the high-side switch, one end of a zero-temperature-drift current generated by a band-gap reference module is electrically connected with an internal low-voltage power supply, and the other end of the zero-temperature-drift current is electrically connected with one end of a shunt resistor and the negative input end of a source electrode input comparator; the positive input end of the source input comparator is electrically connected with the output end of the high-side switch driving chip, and the output end of the source input comparator is electrically connected with the logic control and driving module; one end of the off-chip pull-up resistor is electrically connected with the output end of the high-side switch driving chip, the other end of the off-chip pull-up resistor is electrically connected with an external power supply, and the shunt resistor is used for obtaining a detection threshold voltage based on the zero temperature drift current and the reference current; and the source input comparator is used for obtaining an output end voltage based on an external power supply voltage, an off-chip pull-up resistor and a sink current, detecting that the output end voltage is greater than a maximum value of a detection threshold voltage, and determining a load open circuit, so that the sink current is constantly equal to a reference current, and low sink current in a wide working voltage range is realized.

Description

Technical Field

[0001] The present disclosure relates to the technical field of integrated circuits, and in particular to an open circuit detection circuit of a high-side switch. Background Art

[0002] High-side switches can provide efficient, reliable, safe, and intelligent load control, including resistive loads, capacitive loads, inductive loads, and LED loads. They are in high demand in the fields of automotive electronics, industrial automation, and IoT devices. In some critical applications, the load must remain in normal working condition. If the load is open and the high-side switch is in the on state, it will cause unnecessary power loss and may even affect the safety and reliability of the system. Therefore, the load open circuit detection circuit is very important for the design of high-side switches. It helps diagnose whether the load is damaged or the line is disconnected to ensure that the system can take appropriate responses. The open circuit detection of the high-side switch in the on and off states is different. In the on state, the current on the load can be detected by the built-in high-precision current detection circuit, while an external pull-up resistor is required in the off state. Usually, the output voltage is converted to a low voltage by using a resistor divider, and then a comparator is used at the low voltage threshold to compare with the detection threshold voltage to achieve detection. Such as Figure 1 The schematic diagram of the conventional open circuit detection circuit of the high-side switch in the off state is as follows: the output voltage V OUT Resistor voltage division is performed, where the sum of the resistance values ​​of the first resistor R1 and the second resistor R2 is much larger than the load. When the load is connected, the open circuit detection circuit should not transmit an erroneous load open circuit diagnosis, that is, it is necessary to avoid the positive terminal voltage of the comparator exceeding the minimum value of the detection threshold voltage V OL,min : When the load is open, the open detection circuit should transmit the correct load open diagnosis, that is, the positive terminal voltage of the comparator must exceed the maximum value of the detection threshold voltage V OL,max : However, the conventional open circuit detection circuit mentioned above has the following two problems: (1) To ensure the normal operation of the system, the output current is usually limited to a reasonable range. If the load is short-circuited to the power supply, the output current will be affected by the external power supply voltage V CC Due to the influence of the output current, under a wide operating voltage range, the output current will exceed the specified maximum value, which may affect the normal operation of the system. Therefore, this circuit is not suitable for a wide operating voltage range. (2) When connecting an inductive load, when the high-side switch is suddenly turned off, a reverse electromotive force will be generated at both ends of the inductor, that is, a transient negative high voltage will be generated at the output end. If there is no appropriate protection measure, it may cause breakdown and damage to the internal components. Therefore, this circuit is not compatible with inductive loads. Summary of the invention

[0003] The technical problem to be solved by the present disclosure is to overcome the defect that the conventional open circuit detection circuit in the prior art cannot achieve low sink current under a wide operating voltage range, and to provide an open circuit detection circuit for a high-side switch.

[0004] The present invention solves the above technical problems through the following technical solutions:

[0005] In a first aspect, the present disclosure provides an open circuit detection circuit of a high-side switch, which is applicable to a high-side switch driver chip. The high-side switch driver chip includes an NMOS tube, which is in an off state. The high-side switch driver chip also includes an open circuit detection circuit, a bandgap reference module, and a logic control and drive module. The open circuit detection circuit includes a source input comparator, a shunt resistor, and an off-chip pull-up resistor; one end of the zero temperature drift current generated by the bandgap reference module is electrically connected to an internal low-voltage power supply, and the other end of the zero temperature drift current generated by the bandgap reference module is electrically connected to the shunt resistor. and the negative input terminal of the source input comparator, the other end of the shunt resistor is grounded, the positive input terminal of the source input comparator is electrically connected to the output terminal of the high-side switch driver chip, the input terminal of the high-side switch driver chip is electrically connected to one end of the logic control and drive module, and the other end of the logic control and drive module is electrically connected to the output terminal of the source input comparator and an external power supply respectively; one end of the off-chip pull-up resistor is electrically connected to the output terminal of the high-side switch driver chip, and the other end of the off-chip pull-up resistor is electrically connected to the external power supply;

[0006] The bandgap reference module is used to generate a zero temperature drift current;

[0007] The shunt resistor is used to obtain a detection threshold voltage based on the zero temperature drift current and the reference current;

[0008] The source input comparator is used to obtain the output terminal voltage of the high-side switch driver chip based on the external power supply voltage, the off-chip pull-up resistor and the input current of the output terminal of the high-side switch driver chip, and when detecting that the output terminal voltage is greater than the maximum value of the detection threshold voltage, determine that the load is in an open circuit state, so that the input current of the output terminal of the high-side switch driver chip is always equal to the reference current.

[0009] Preferably, the source input comparator is also used to obtain the output voltage of the high-side switch driver chip based on the external power supply voltage, the off-chip pull-up resistor and the load resistor, and to determine that the load is in a connected state when it detects that the output voltage is less than the minimum value of the detection threshold voltage.

[0010] Preferably, the high-side switch driver chip includes an NMOS tube, and the open circuit detection circuit further includes a first switch;

[0011] The gate of the NMOS tube is electrically connected to the other end of the logic control and driving module, the drain of the NMOS tube is electrically connected to the external power supply and one end of the first switch respectively, the source of the NMOS tube is electrically connected to the output end of the high-side switch driver chip and the positive input end of the source input comparator respectively, and the other end of the first switch is electrically connected to the other end of the off-chip pull-up resistor;

[0012] The logic control and driving module is used to control the turning off or on of the NMOS tube;

[0013] The first switch is used to pull up the output terminal voltage of the high-side switch driver chip when the NMOS tube is in the off state.

[0014] Preferably, the source input comparator comprises a first MOS transistor and a second MOS transistor;

[0015] The drain of the first MOS tube is electrically connected to the other end of the bandgap reference module and one end of the shunt resistor respectively, the source of the first MOS tube is electrically connected to the gate of the first MOS tube, the drain of the second MOS tube is electrically connected to the output end of the high-side switch driver chip, and the source of the second MOS tube is electrically connected to the gate of the second MOS tube;

[0016] The first MOS tube is used to ensure that the voltage drop of the detection threshold voltage and the output terminal voltage is introduced symmetrically;

[0017] The second MOS tube is used to isolate the negative high voltage at the output end of the high-side switch driver chip.

[0018] Preferably, the source input comparator comprises a first MOS tube, a second MOS tube, a third MOS tube, a fourth MOS tube and an inverter;

[0019] The drain of the third MOS tube is electrically connected to the source of the first MOS tube, the gate of the third MOS tube is electrically connected to the output end of the input end of the high-side switch driver chip through the inverter, the drain of the fourth MOS tube is electrically connected to the source of the second MOS tube, and the gate of the fourth MOS tube is electrically connected to the output end of the input end of the high-side switch driver chip through the inverter;

[0020] The third MOS transistor is used to cooperate with the first MOS transistor to ensure that the voltage drop of the detection threshold voltage and the output terminal voltage is introduced symmetrically;

[0021] The fourth MOS tube is used to isolate the positive high voltage at the output end of the high-side switch driver chip.

[0022] Preferably, the source input comparator includes a first MOS tube, a second MOS tube, a third MOS tube, a fourth MOS tube, a fifth MOS tube, a sixth MOS tube, a seventh MOS tube, and an eighth MOS tube;

[0023] The source of the fifth MOS tube is electrically connected to the source of the third MOS tube, the gate of the fifth MOS tube is electrically connected to the gate of the sixth MOS tube and the drain of the fifth MOS tube respectively, the source of the sixth MOS tube is electrically connected to the source of the fourth MOS tube, the gate of the seventh MOS tube is electrically connected to the drain of the eighth MOS tube and the drain of the sixth MOS tube respectively, the source of the seventh MOS tube and the source of the eighth MOS tube are both grounded, and the gate of the eighth MOS tube is electrically connected to the input end of the high-side switch driver chip;

[0024] The fifth MOS tube and the sixth MOS tube are input pair tubes of the source input comparator;

[0025] The sixth MOS tube is used to pull up the gate voltage of the seventh MOS tube when the output terminal voltage of the high-side switch driver chip is greater than the detection threshold voltage, so as to turn on the seventh MOS tube;

[0026] The seventh MOS tube is used to lower the drain voltage of the seventh MOS tube;

[0027] The eighth MOS tube is used to pull down the gate voltage of the seventh MOS tube.

[0028] Preferably, the source input comparator includes a first MOS tube, a second MOS tube, a third MOS tube, a fourth MOS tube, a fifth MOS tube, a sixth MOS tube, a seventh MOS tube, an eighth MOS tube, and a ninth MOS tube;

[0029] The source of the ninth MOS tube is electrically connected to the internal low-voltage power supply, the gate of the ninth MOS tube is grounded, and the drain of the ninth MOS tube is electrically connected to the drain of the seventh MOS tube;

[0030] The ninth MOS tube is used to pull down the gate voltage of the seventh MOS tube and turn off the seventh MOS tube when the output terminal voltage of the high-side switch driver chip is less than the detection threshold voltage, so as to pull up the drain voltage of the seventh MOS tube to the voltage of the internal low-voltage power supply.

[0031] Preferably, the source input comparator includes a first MOS tube, a second MOS tube, a third MOS tube, a fourth MOS tube, a fifth MOS tube, a sixth MOS tube, a seventh MOS tube, an eighth MOS tube, a ninth MOS tube, a Schmitt trigger and an inverter;

[0032] The input end of the inverter is electrically connected to the input end of the high-side switch driver chip, the output end of the inverter is electrically connected to the gates of the third MOS tube and the fourth MOS tube, the input end of the Schmitt trigger is electrically connected to the drain of the seventh MOS tube and the drain of the ninth MOS tube respectively, and the output end of the Schmitt trigger is electrically connected to the logic control and drive module;

[0033] The Schmitt trigger is used to output a low-level detection signal or a high-level detection signal.

[0034] Preferably, the first MOS tube, the second MOS tube, the third MOS tube and the fourth MOS tube are all high-voltage tubes; the fifth MOS tube, the sixth MOS tube, the seventh MOS tube, the eighth MOS tube and the ninth MOS tube are all low-voltage isolation tubes.

[0035] Preferably, the first MOS tube, the second MOS tube, the fifth MOS tube, the sixth MOS tube and the ninth MOS tube are all PMOS tubes; the third MOS tube, the fourth MOS tube, the seventh MOS tube and the eighth MOS tube are all NMOS tubes.

[0036] On the basis of being in accordance with the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present disclosure.

[0037] The positive and progressive effects of this disclosure are:

[0038] The present invention combines a bandgap reference module, a logic control and drive module, a source input comparator, a shunt resistor and an off-chip pull-up resistor, uses a zero temperature drift current generated by the bandgap reference module, and then combines it with a reference current to obtain a detection threshold voltage; then when the source input comparator detects that the output voltage is greater than the maximum value of the detection threshold voltage, it is determined that the load is in an open circuit state, so that the input current of the output end of the high-side switch driver chip is always equal to the reference current, thereby achieving low input current under a wide operating voltage range. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a structural schematic diagram of an open circuit detection circuit of a high side switch in the prior art;

[0040] Figure 2 A first structural schematic diagram of an open circuit detection circuit of a high-side switch provided in Embodiment 1 of the present disclosure;

[0041] Figure 3 This is a second structural schematic diagram of an open circuit detection circuit for a high-side switch provided in Example 1 of the present disclosure. DETAILED DESCRIPTION

[0042] The present disclosure is further described below by way of examples, but the present disclosure is not limited to the scope of the examples.

[0043] Prefixes such as "first" and "second" are used in the embodiments of the present disclosure only to distinguish different description objects, and have no limiting effect on the position, order, priority, quantity or content of the described objects. The use of prefixes such as ordinal numbers to distinguish description objects in the embodiments of the present disclosure does not constitute a limitation on the described objects. For the statement of the described objects, please refer to the description in the context of the claims or embodiments, and no unnecessary limitation should be constituted due to the use of such prefixes. In addition, in the description of the present embodiment, unless otherwise specified, the meaning of "plurality" is two or more.

[0044] In the embodiments of the present disclosure, the collection, storage, use, processing, transmission, provision and disclosure of user personal information involved are in compliance with the provisions of relevant laws and regulations and do not violate public order and good morals.

[0045] Example 1

[0046] Figure 2 A schematic diagram of a high-side switch open circuit detection circuit provided by an exemplary embodiment of the present disclosure is provided. The high-side switch open circuit detection circuit is suitable for a high-side switch driver chip. The high-side switch driver chip includes an NMOS tube, which is in an off state. The high-side switch driver chip also includes an open circuit detection circuit 1, a bandgap reference module 2 and a logic control and drive module 3. The open circuit detection circuit 1 includes a source input comparator 11, a shunt resistor R L and an external pull-up resistor R pu ; One end of the zero temperature drift current generated by the bandgap reference module 2 is connected to the internal low voltage power supply V DD The other end of the zero temperature drift current generated by the bandgap reference module 2 is electrically connected to the shunt resistor R L and the negative input terminal of the source input comparator 11, the shunt resistor R L The other end of the source input comparator 11 is grounded, the positive input end of the source input comparator 11 is electrically connected to the output end OUT of the high-side switch driver chip, the input end IN of the high-side switch driver chip is electrically connected to one end of the logic control and drive module 3, and the other end of the logic control and drive module 3 is respectively connected to the output end OUT of the source input comparator 11 and the external power supply V CC Electrical connection; off-chip pull-up resistor R pu One end of the high-side switch driver chip is electrically connected to the output terminal OUT, and the off-chip pull-up resistor R pu The other end is connected to the external power supply V CC Electrical connection;

[0047] Bandgap reference module 2, used to generate zero temperature drift current I ZTC ;

[0048] Shunt resistor R L , for zero temperature drift current I ZTC And the reference current I REF Get the detection threshold voltage V OL ;

[0049] The source input comparator 11 is used to generate a voltage based on the external power supply voltage V CC , external pull-up resistor R pu The output voltage V of the high-side switch driver chip is obtained by the input current of the output end of the high-side switch driver chip. OUT , and detect the output voltage V OUT Greater than the maximum detection threshold voltage V OL,max When the load is in an open circuit state, the output current I L(off) Constantly equal to the reference current I REF .

[0050] In this embodiment, the source input comparator is used to generate a voltage based on the external power supply voltage V CC With the external pull-up resistor R pu and the output current I of the high-side switch driver chip L(off) The difference of the product is the output voltage V of the high-side switch driver chip. OUT , and detect that the output voltage is greater than the maximum value of the detection threshold voltage (i.e. ), it is determined that the load is in an open circuit state, so that the input current of the output end of the high-side switch driver chip is always equal to the reference current.

[0051] Specifically, when the load is open circuit (such as Figure 2 6 in the figure), the open circuit detection circuit diagnoses that the load is open circuit, that is, the output voltage V OUT The detection threshold voltage must exceed the maximum value V OL,max .

[0052] It should be noted that, for example, the load may be Figure 2 The device in the dashed box 8.

[0053] In addition, the zero temperature drift current generated by the bandgap reference module is divided into two paths, one path flows to the shunt resistor to generate the detection threshold voltage, and the other path flows to the negative input terminal of the source input comparator.

[0054] This embodiment combines a bandgap reference module, a logic control and drive module, a source input comparator, a shunt resistor and an off-chip pull-up resistor, uses the zero temperature drift current generated by the bandgap reference module, and then combines it with the reference current to obtain the detection threshold voltage; then when the source input comparator detects that the output voltage is greater than the maximum value of the detection threshold voltage, it is determined that the load is in an open circuit state, so that the input current of the output end of the high-side switch driver chip is always equal to the reference current, thereby achieving low input current under a wide operating voltage range.

[0055] In an optional embodiment, the source input comparator is also used to obtain the output voltage of the high-side switch driver chip based on the external power supply voltage, the off-chip pull-up resistor and the load resistor, and to determine that the load is in a connected state when the output voltage is detected to be less than the minimum value of the detection threshold voltage.

[0056] In this embodiment, the source input comparator is used to generate a voltage based on the external power supply voltage V CC With the load resistor R and the external pull-up resistor R pu The output voltage V of the high-side switch driver chip is obtained by multiplying the ratio of the sum of the load resistance R OUT , and detects that the output voltage is less than the minimum value of the detection threshold voltage (i.e. ), make sure the load is connected.

[0057] Specifically, when the load is connected (such as Figure 2 As shown in 6 in the figure), the open circuit detection circuit diagnoses that the load is not open circuited, that is, the output voltage V OUT Exceeds the minimum detection threshold voltage V OL,min .

[0058] It should be noted that it is also necessary to select an external pull-up resistor R with a suitable resistance value. pu , the output current I when the load is open L(off) Constantly equal to the reference current I REF , thus supporting a wide operating voltage range.

[0059] In an optional embodiment, if Figure 2 As shown, the high-side switch driver chip further includes an NMOS tube, and the open circuit detection circuit 1 further includes a first switch S1;

[0060] The gate of the NMOS tube is electrically connected to the other end of the logic control and driving module 3, and the drain of the NMOS tube is electrically connected to the external power supply V CC The source of the NMOS tube is electrically connected to the output end of the high-side switch driver chip and the positive input end of the source input comparator, and the other end of the first switch S1 is electrically connected to the off-chip pull-up resistor R pu The other end is electrically connected;

[0061] Logic control and drive module 3, used to control the NMOS tube to be turned off or on;

[0062] The first switch S1 is used to pull up the output voltage of the high-side switch driver chip when the NMOS tube is in the off state.

[0063] In the specific implementation process, the zero temperature drift current I ZTC Generates detection threshold voltage V OL And the reference current I REF , and then through the source input comparator 11 to the output voltage V OUT The detection threshold voltage V OL Compare to determine whether the load is open circuit.

[0064] Specifically, when the load is connected, the open circuit detection circuit diagnoses that the load is not open circuited, that is, the output voltage V OUT Exceeds the minimum detection threshold voltage V OL,min , as shown in formula (1):

[0065] (1)

[0066] When the load is open, the open circuit detection circuit diagnoses that the load is open, that is, the output voltage V OUT The detection threshold voltage must exceed the maximum value V OL,max , as shown in formula (2):

[0067] (2)

[0068] In an optional embodiment, if Figure 3 As shown, the source input comparator includes a first MOS transistor PM1 and a second MOS transistor PM2;

[0069] The drain of the first MOS transistor PM1 is electrically connected to the other end of the bandgap reference module and one end of the shunt resistor respectively, the source of the first MOS transistor PM1 is electrically connected to the gate of the first MOS transistor PM1, the drain of the second MOS transistor PM2 is electrically connected to the output end OUT of the high-side switch driver chip, and the source of the second MOS transistor PM2 is electrically connected to the gate of the second MOS transistor PM2;

[0070] The first MOS tube PM1 is used to ensure the detection threshold voltage V OL and the output voltage V OUT The pressure drop is introduced symmetrically;

[0071] The second MOS transistor PM2 is used to isolate the negative high voltage at the output terminal OUT of the high-side switch driver chip.

[0072] In an optional embodiment, if Figure 3 As shown, the source input comparator 11 includes a first MOS transistor PM1, a second MOS transistor PM2, a third MOS transistor NM1, a fourth MOS transistor NM2 and an inverter 5;

[0073] The drain of the third MOS transistor NM1 is electrically connected to the source of the first MOS transistor PM1, the gate of the third MOS transistor NM1 is electrically connected to the output end of the input end IN of the high-side switch driver chip through the inverter, the drain of the fourth MOS transistor NM2 is electrically connected to the source of the second MOS transistor PM2, and the gate of the fourth MOS transistor NM2 is electrically connected to the output end of the input end IN of the high-side switch driver chip through the inverter;

[0074] The third MOS transistor NM1 is used to cooperate with the first MOS transistor PM1 to ensure the detection threshold voltage V OL and the output voltage V OUT The pressure drop is introduced symmetrically;

[0075] The fourth MOS transistor NM2 is used to isolate the positive high voltage at the output terminal OUT of the high-side switch driver chip.

[0076] In an optional embodiment, if Figure 3 As shown, the source input comparator 11 includes a first MOS transistor PM1, a second MOS transistor PM2, a third MOS transistor NM1, a fourth MOS transistor NM2, a fifth MOS transistor PM3, a sixth MOS transistor PM4, a seventh MOS transistor NM3, and an eighth MOS transistor NM4;

[0077] The source of the fifth MOS transistor PM3 is electrically connected to the source of the third MOS transistor NM1, the gate of the fifth MOS transistor PM3 is electrically connected to the gate of the sixth MOS transistor PM4 and the drain of the fifth MOS transistor PM3, the source of the sixth MOS transistor PM4 is electrically connected to the source of the fourth MOS transistor, the gate of the seventh MOS transistor NM3 is electrically connected to the drain of the eighth MOS transistor NM4 and the drain of the sixth MOS transistor PM4, the source of the seventh MOS transistor NM3 and the source of the eighth MOS transistor NM4 are both grounded, and the gate of the eighth MOS transistor NM4 is electrically connected to the input terminal IN of the high-side switch driver chip;

[0078] The fifth MOS transistor PM3 and the sixth MOS transistor PM4 are input pairs of transistors of the source input comparator 11;

[0079] The sixth MOS transistor PM4 is used to drive the output voltage V OUT Greater than the detection threshold voltage V OL When the gate voltage of the seventh MOS tube NM3 is pulled high, the seventh MOS tube NM3 is turned on;

[0080] The seventh MOS tube NM3 is used to pull down the drain voltage of the seventh MOS tube NM3;

[0081] The eighth MOS transistor NM4 is used for pulling down the gate voltage of the seventh MOS transistor NM3.

[0082] In an optional embodiment, if Figure 3 As shown, the source input comparator 11 includes a first MOS transistor PM1, a second MOS transistor PM2, a third MOS transistor NM1, a fourth MOS transistor NM2, a fifth MOS transistor PM3, a sixth MOS transistor PM4, a seventh MOS transistor NM3, an eighth MOS transistor NM4, and a ninth MOS transistor PM5;

[0083] The source of the ninth MOS tube PM5 is connected to the internal low voltage power supply V DD The gate of the ninth MOS transistor PM5 is grounded, and the drain of the ninth MOS transistor PM5 is electrically connected to the drain of the seventh MOS transistor NM3;

[0084] The ninth MOS tube PM5 is used to drive the output voltage V OUT Less than the detection threshold voltage V OL When the gate voltage of the seventh MOS tube NM3 is pulled down, the seventh MOS tube NM3 is turned off, so as to pull the drain voltage of the seventh MOS tube NM3 up to the internal low voltage power supply V DD voltage.

[0085] In an optional embodiment, if Figure 3 As shown, the source input comparator includes a first MOS transistor PM1, a second MOS transistor PM2, a third MOS transistor NM1, a fourth MOS transistor NM2, a fifth MOS transistor PM3, a sixth MOS transistor PM4, a seventh MOS transistor NM3, an eighth MOS transistor NM4, a ninth MOS transistor PM5, a Schmitt trigger 4 and an inverter 5;

[0086] The input end of the inverter 5 is electrically connected to the input end IN of the high-side switch driving chip, the output end of the inverter 5 is electrically connected to the gates of the third MOS tube NM1 and the fourth MOS tube NM2, the input end of the Schmitt trigger 4 is electrically connected to the drain of the seventh MOS tube NM3 and the drain of the ninth MOS tube PM5, and the output end of the Schmitt trigger 4 is electrically connected to the logic control and driving module 3;

[0087] The Schmitt trigger 4 is used to output a low-level detection signal or a high-level detection signal.

[0088] In an optional embodiment, if Figure 3As shown, the first MOS transistor PM1, the second MOS transistor PM2, the third MOS transistor NM1 and the fourth MOS transistor NM2 are all high-voltage transistors; the fifth MOS transistor PM3, the sixth MOS transistor PM4, the seventh MOS transistor NM3, the eighth MOS transistor NM4 and the ninth MOS transistor PM5 are all low-voltage isolation transistors.

[0089] In an optional embodiment, if Figure 3 As shown, the first MOS transistor PM1, the second MOS transistor PM2, the fifth MOS transistor PM3, the sixth MOS transistor PM4 and the ninth MOS transistor PM5 are all PMOS transistors; the third MOS transistor NM1, the fourth MOS transistor NM2, the seventh MOS transistor NM3 and the eighth MOS transistor NM4 are all NMOS transistors.

[0090] In the specific implementation process, the fifth MOS transistor PM3 and the sixth MOS transistor PM4 are input pairs of the source input comparator 11; the fourth MOS transistor NM2 controlled by the input terminal IN of the input high-side switch driver chip is used to isolate the positive high voltage of the output terminal OUT; the inverted normally closed second MOS transistor PM2 is used to isolate the negative high voltage of the output terminal OUT; the third MOS transistor NM1 and the fourth MOS transistor NM2 are used to ensure that the input detection threshold voltage V OL and the output voltage V OUT The voltage drop is introduced symmetrically; the ninth MOS tube PM5 and the seventh MOS tube NM3 form a common source amplification.

[0091] Specifically, when the output voltage V OUT Below the detection threshold voltage V OL When the node n1 (for example, the gate voltage of the seventh MOS transistor NM3) is referenced by the current I REF The seventh MOS transistor NM is turned off, so that the node n2 (for example, the drain voltage of the seventh MOS transistor NM3) is pulled up to the internal low-voltage power supply V by the ninth MOS transistor PM5. DD , the Schmitt trigger 4 outputs a low-level detection signal indicating that the load is not open-circuited; when the output voltage V OUT Higher than the detection threshold voltage V OL When the node n1 (for example, the gate voltage of the seventh MOS transistor NM3) is pulled high by the sixth MOS transistor PM4, the seventh MOS transistor is turned on, so that the node n2 (for example, the drain voltage of the seventh MOS transistor NM3) is pulled low to 0 by the seventh MOS transistor NM3, and the high-level detection signal outputted by the Schmitt trigger 4 indicates that the load is open.

[0092] In this embodiment, if the load is short-circuited to the power supply, the output current I L(off) It is also always equal to the reference current I REF, so the invention supports a wide operating voltage range. Further, when open circuit detection is not performed, that is, when the input terminal IN of the input high-side switch driver chip is at a high level, the third MOS tube NM1 and the fourth MOS tube NM2 in the specific example are turned off, and the node n1 is pulled down by the eighth MOS tube NM4. At this time, the invention can achieve non-injection current introduction; in addition, when an inductive load is connected, the inverted normally closed high-voltage tube second MOS tube PM2 in the specific example can isolate the negative high voltage of the output terminal OUT, so the invention is compatible with inductive loads.

[0093] Although the specific embodiments of the present disclosure are described above, those skilled in the art should understand that this is only an example, and the protection scope of the present disclosure is defined by the appended claims. Those skilled in the art may make various changes or modifications to these embodiments without departing from the principles and essence of the present disclosure, but these changes and modifications all fall within the protection scope of the present disclosure.

Claims

1. An open circuit detection circuit for a high side switch, characterized in that: Applicable to a high-side switch driver chip, the high-side switch driver chip includes an NMOS tube, the NMOS tube is in an off state, the high-side switch driver chip also includes an open circuit detection circuit, a bandgap reference module and a logic control and drive module, the open circuit detection circuit includes a source input comparator, a shunt resistor and an off-chip pull-up resistor; one end of the zero temperature drift current generated by the bandgap reference module is electrically connected to an internal low-voltage power supply, the other end of the zero temperature drift current generated by the bandgap reference module is respectively electrically connected to one end of the shunt resistor and the negative input end of the source input comparator, the other end of the shunt resistor is grounded, the positive input end of the source input comparator is electrically connected to the output end of the high-side switch driver chip, the input end of the high-side switch driver chip is electrically connected to one end of the logic control and drive module, and the other end of the logic control and drive module is respectively electrically connected to the output end of the source input comparator and an external power supply; one end of the off-chip pull-up resistor is electrically connected to the output end of the high-side switch driver chip, and the other end of the off-chip pull-up resistor is electrically connected to the external power supply; The bandgap reference module is used to generate a zero temperature drift current; The shunt resistor is used to obtain a detection threshold voltage based on the zero temperature drift current and the reference current; The source input comparator is used to obtain the output terminal voltage of the high-side switch driver chip based on the external power supply voltage, the off-chip pull-up resistor and the input current of the output terminal of the high-side switch driver chip, and when detecting that the output terminal voltage is greater than the maximum value of the detection threshold voltage, determine that the load is in an open circuit state, so that the input current of the output terminal of the high-side switch driver chip is always equal to the reference current.

2. The open circuit detection circuit of the high side switch according to claim 1, characterized in that: The source input comparator is also used to obtain the output voltage of the high-side switch driver chip based on the external power supply voltage, the off-chip pull-up resistor and the load resistor, and to determine that the load is in a connected state when it detects that the output voltage is less than the minimum value of the detection threshold voltage.

3. The open circuit detection circuit of the high side switch according to claim 1, characterized in that: The high-side switch driving chip includes an NMOS tube, and the open circuit detection circuit also includes a first switch; The gate of the NMOS tube is electrically connected to the other end of the logic control and driving module, the drain of the NMOS tube is electrically connected to the external power supply and one end of the first switch respectively, the source of the NMOS tube is electrically connected to the output end of the high-side switch driver chip and the positive input end of the source input comparator respectively, and the other end of the first switch is electrically connected to the other end of the off-chip pull-up resistor; The logic control and driving module is used to control the turning off or on of the NMOS tube; The first switch is used to pull up the output terminal voltage of the high-side switch driver chip when the NMOS tube is in the off state.

4. The open circuit detection circuit of the high side switch according to claim 1, characterized in that: The source input comparator includes a first MOS tube and a second MOS tube; The drain of the first MOS tube is electrically connected to the other end of the bandgap reference module and one end of the shunt resistor respectively, the source of the first MOS tube is electrically connected to the gate of the first MOS tube, the drain of the second MOS tube is electrically connected to the output end of the high-side switch driver chip, and the source of the second MOS tube is electrically connected to the gate of the second MOS tube; The first MOS tube is used to ensure that the voltage drop of the detection threshold voltage and the output terminal voltage is introduced symmetrically; The second MOS tube is used to isolate the negative high voltage at the output end of the high-side switch driver chip.

5. The open circuit detection circuit of the high side switch according to claim 1, characterized in that: The source input comparator comprises a first MOS tube, a second MOS tube, a third MOS tube, a fourth MOS tube and an inverter; The drain of the third MOS tube is electrically connected to the source of the first MOS tube, the gate of the third MOS tube is electrically connected to the output end of the input end of the high-side switch driver chip through the inverter, the drain of the fourth MOS tube is electrically connected to the source of the second MOS tube, and the gate of the fourth MOS tube is electrically connected to the output end of the input end of the high-side switch driver chip through the inverter; The third MOS transistor is used to cooperate with the first MOS transistor to ensure that the voltage drop of the detection threshold voltage and the output terminal voltage is introduced symmetrically; The fourth MOS tube is used to isolate the positive high voltage at the output end of the high-side switch driver chip.

6. The open circuit detection circuit of the high side switch according to claim 1, characterized in that: The source input comparator includes a first MOS tube, a second MOS tube, a third MOS tube, a fourth MOS tube, a fifth MOS tube, a sixth MOS tube, a seventh MOS tube, and an eighth MOS tube; The source of the fifth MOS tube is electrically connected to the source of the third MOS tube, the gate of the fifth MOS tube is electrically connected to the gate of the sixth MOS tube and the drain of the fifth MOS tube respectively, the source of the sixth MOS tube is electrically connected to the source of the fourth MOS tube, the gate of the seventh MOS tube is electrically connected to the drain of the eighth MOS tube and the drain of the sixth MOS tube respectively, the source of the seventh MOS tube and the source of the eighth MOS tube are both grounded, and the gate of the eighth MOS tube is electrically connected to the input end of the high-side switch driver chip; The fifth MOS tube and the sixth MOS tube are input pair tubes of the source input comparator; The sixth MOS tube is used to pull up the gate voltage of the seventh MOS tube when the output terminal voltage of the high-side switch driver chip is greater than the detection threshold voltage, so as to turn on the seventh MOS tube; The seventh MOS tube is used to lower the drain voltage of the seventh MOS tube; The eighth MOS tube is used to pull down the gate voltage of the seventh MOS tube.

7. The open circuit detection circuit of the high side switch according to claim 1, characterized in that: The source input comparator includes a first MOS tube, a second MOS tube, a third MOS tube, a fourth MOS tube, a fifth MOS tube, a sixth MOS tube, a seventh MOS tube, an eighth MOS tube, and a ninth MOS tube; The source of the ninth MOS tube is electrically connected to the internal low-voltage power supply, the gate of the ninth MOS tube is grounded, and the drain of the ninth MOS tube is electrically connected to the drain of the seventh MOS tube; The ninth MOS tube is used to pull down the gate voltage of the seventh MOS tube and turn off the seventh MOS tube when the output terminal voltage of the high-side switch driver chip is less than the detection threshold voltage, so as to pull up the drain voltage of the seventh MOS tube to the voltage of the internal low-voltage power supply.

8. The open circuit detection circuit of a high side switch according to claim 1, characterized in that: The source input comparator includes a first MOS tube, a second MOS tube, a third MOS tube, a fourth MOS tube, a fifth MOS tube, a sixth MOS tube, a seventh MOS tube, an eighth MOS tube, a ninth MOS tube, a Schmitt trigger and an inverter; The input end of the inverter is electrically connected to the input end of the high-side switch driver chip, the output end of the inverter is electrically connected to the gates of the third MOS tube and the fourth MOS tube, the input end of the Schmitt trigger is electrically connected to the drain of the seventh MOS tube and the drain of the ninth MOS tube respectively, and the output end of the Schmitt trigger is electrically connected to the logic control and drive module; The Schmitt trigger is used to output a low-level detection signal or a high-level detection signal.

9. The open circuit detection circuit of the high side switch according to claim 8, characterized in that: The first MOS tube, the second MOS tube, the third MOS tube and the fourth MOS tube are all high-voltage tubes; the fifth MOS tube, the sixth MOS tube, the seventh MOS tube, the eighth MOS tube and the ninth MOS tube are all low-voltage isolation tubes.

10. The open circuit detection circuit of a high side switch according to claim 8, characterized in that: The first MOS tube, the second MOS tube, the fifth MOS tube, the sixth MOS tube and the ninth MOS tube are all PMOS tubes; the third MOS tube, the fourth MOS tube, the seventh MOS tube and the eighth MOS tube are all NMOS tubes.

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