Switching power tube cut-off control circuit and driving chip

Abstract

The invention discloses a switch power tube cut-off control circuit and a driving chip, and relates to the technical field of power electronics, the circuit comprises a first controllable switch, a voltage drop detection circuit and a switch controller; wherein the first controllable switch is coupled with the switching power tube, and when the first controllable switch is switched on, the switching power tube is controlled to be switched off; the switch controller is used for receiving a forced conduction signal and an input conduction signal output by the input conduction signal voltage drop detection circuit, and controlling the conduction time of the first controllable switch by taking the longest signal as a criterion; the voltage drop detection circuit is used for detecting the current output to the driven switch power tube when the first controllable switch is turned on, so that the output current is small enough when the first controllable switch is turned off to switch the on-off state of the switch power tube, the oscillation voltage generated on parasitic inductance is reduced, and the power supply reliability is improved. And the voltage of the capacitive load can be fully discharged, so that the use safety and the service life of the switching power tube driving chip can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, and in particular to a switch power tube cutoff control circuit and a switch power tube drive chip. Background Art

[0002] At present, there is a parasitic inductance between the circuit that drives and controls the on and off of the load (i.e., the switch power tube) and the load. When the oscillating voltage generated by the inductance exceeds the withstand voltage of the components in the circuit (such as transistors), it will damage the components in the circuit; and if the shutdown signal output by the circuit is short, the voltage of the capacitive load cannot be discharged, causing the load to be unable to shut down. Therefore, how to reduce the impact of the parasitic inductance of the line between the control circuit and the switch power tube on the switch power tube drive and improve the circuit safety and component life is an urgent problem to be solved today. Summary of the invention

[0003] The purpose of the present invention is to provide a switch power tube cutoff control circuit and a drive chip to reduce the influence of the parasitic inductance of the line between the control circuit and the switch power tube on the switch power tube drive, thereby improving the circuit's safety and component life.

[0004] In order to solve the above technical problems, the present invention provides a switch power tube cut-off control circuit, comprising: a first controllable switch, a voltage drop detection circuit and a switch controller;

[0005] Wherein, the first controllable switch is coupled to the switch power tube, and the switch power tube is controlled to be turned off when the first controllable switch is turned on;

[0006] The input end of the voltage drop detection circuit is controllably connected to the first controllable switch in a conduction phase of the first controllable switch, and detects the conduction voltage drop of the first controllable switch when connected; and when the conduction voltage drop of the first controllable switch is greater than or equal to a first reference voltage, outputs a forced conduction signal until the conduction voltage drop of the first controllable switch is less than a second reference voltage;

[0007] The first input end of the switch controller is connected to the output end of the voltage drop detection circuit, and the output end of the switch controller is connected to the control end of the first controllable switch; the switch controller is used to receive the forced conduction signal and the input conduction signal, and control the conduction time of the first controllable switch based on the signal with the longest time.

[0008] In another aspect, the circuit further comprises: an on-time controller;

[0009] The input end of the voltage drop detection circuit is connected to the first controllable switch through the on-time controller, and the on-time controller controls the first controllable switch to be connected to the voltage drop detection circuit all or part of the time in the on-state.

[0010] On the other hand, the portion of time is from when the first controllable switch is turned on to when the on-state voltage drop of the first controllable switch reaches a peak value.

[0011] On the other hand, the portion of time is a set time after the first controllable switch is turned on.

[0012] In another aspect, the voltage drop detection circuit includes: a comparator circuit and a reference voltage output circuit;

[0013] The first input end of the comparator circuit is connected to the voltage drop detection end through the conduction controller, and the voltage drop detection end is an end of the first controllable switch used to be connected to the control end of the switch power tube; the conduction time controller is used to conduct the connection between the first input end of the comparator circuit and the voltage drop detection end when the first controllable switch is turned on;

[0014] The output end of the comparator circuit is connected to the control end of the reference voltage output circuit, and the first reference voltage output end and the second reference voltage output end of the reference voltage output circuit are both connected to the second input end of the comparator circuit;

[0015] The reference voltage output circuit is used to output a first reference voltage to the second input terminal of the comparator circuit when the comparator circuit outputs a first level signal; and output a second reference voltage to the second input terminal of the comparator circuit when the comparator circuit outputs a second level signal;

[0016] The comparator circuit is used to output a first level signal when the voltage of the voltage drop detection terminal input at the first input terminal is greater than the first reference voltage or the second reference voltage input at the second input terminal; and output a second level signal when the voltage of the voltage drop detection terminal input at the in-phase input terminal is less than the first reference voltage or the second reference voltage input at the inverting input terminal;

[0017] The common end of the output end of the comparator circuit connected to the control end of the reference voltage output circuit is connected to the first input end of the switch controller as the output end of the voltage drop detection circuit.

[0018] On the other hand, the comparator circuit includes: an operational amplifier; wherein the forced conduction signal is a high-level signal; the non-inverting input terminal of the operational amplifier is connected to the voltage drop detection terminal through the conduction controller, the inverting input terminal of the operational amplifier is connected to the first reference voltage output terminal and the second reference voltage output terminal of the reference voltage output circuit, and the output terminal of the operational amplifier is connected to the control terminal of the reference voltage output circuit;

[0019] The reference voltage output circuit is used to output a first reference voltage to the inverting input terminal of the operational amplifier when the operational amplifier outputs a high level signal; and to output a second reference voltage to the inverting input terminal of the operational amplifier when the operational amplifier outputs a low level signal.

[0020] In another aspect, the reference voltage output circuit includes: a first reference voltage circuit, a second reference voltage circuit, an inverter, a first reference voltage switch, and a second reference voltage switch;

[0021] Wherein, the control end of the second reference voltage switch is connected to the output end of the operational amplifier as the control end of the reference voltage output circuit, and its common end is connected to the control end of the first reference voltage switch through the inverter; the inverting input end of the operational amplifier is connected to the first end of the first reference voltage circuit and the second reference voltage circuit respectively; the second ends of the first reference voltage circuit and the second reference voltage circuit are grounded; the first reference voltage switch and the second reference voltage switch are used to be turned on when a high level signal is input to the control end, and turned off when a low level signal is input to the control end;

[0022] The operational amplifier is specifically used to output a low-level signal to turn off the second reference voltage switch and turn on the first reference voltage switch when the voltage of the voltage drop detection terminal input at the non-phase input terminal is less than the first reference voltage input at the inverting input terminal, so that the first reference voltage provided by the first reference voltage circuit is input at the inverting input terminal; output a high-level signal to turn on the second reference voltage switch and turn off the first reference voltage switch when the voltage of the voltage drop detection terminal input at the non-phase input terminal is greater than the first reference voltage input at the inverting input terminal, so that the second reference voltage provided by the second reference voltage circuit is input at the inverting input terminal; output a low-level signal to turn on the first reference voltage switch and turn off the second reference voltage switch when the voltage of the voltage drop detection terminal input at the non-phase input terminal is less than the second reference voltage input at the inverting input terminal, so that the first reference voltage provided by the first reference voltage circuit is input at the inverting input terminal.

[0023] In another aspect, the circuit further comprises: a second controllable switch;

[0024] Among them, the first end of the first controllable switch is connected to the power supply end through the second controllable switch, the common end connected to the first end of the first controllable switch and the second controllable switch is connected to the control end of the switch power tube, and the second end of the first controllable switch is connected to one end of the switch power tube and grounded.

[0025] On the other hand, the switch controller is specifically used to receive the forced conduction signal, the input conduction signal and the minimum conduction time control signal, and control the conduction time of the first controllable switch based on the signal with the longest time.

[0026] In addition, the present invention also provides a switch power tube driver chip, comprising: the switch power tube cutoff control circuit as described above.

[0027] A switch power tube cut-off control circuit provided by the present invention comprises: a first controllable switch, a voltage drop detection circuit and a switch controller; wherein the first controllable switch is coupled to the switch power tube, and controls the switch power tube to be cut off when the first controllable switch is turned on; the input end of the voltage drop detection circuit is controllably connected to the first controllable switch in the turn-on stage of the first controllable switch, and detects the turn-on voltage drop of the first controllable switch when connected; and when the turn-on voltage drop of the first controllable switch is greater than or equal to a first reference voltage, a forced turn-on signal is output until the turn-on voltage drop of the first controllable switch is less than a second reference voltage; the first input end of the switch controller is connected to the output end of the voltage drop detection circuit, and the output end of the switch controller is connected to the control end of the first controllable switch; the switch controller is used to receive the forced turn-on signal and the input turn-on signal, and control the turn-on time of the first controllable switch based on the signal with the longest time;

[0028] It can be seen that the present invention uses a voltage drop detection circuit to detect the current output to the driven switch power tube when the first controllable switch is turned on, so as to ensure that when the switch power tube is switched on and off by turning off the first controllable switch, the output current is small enough, reducing the oscillation voltage generated on the parasitic inductance, and being able to fully discharge the voltage of the capacitive load to avoid the situation where the load cannot be turned off, and being able to reduce the influence of the parasitic inductance of the line between the control circuit and the switch power tube on the switch power tube drive, thereby improving the circuit safety and component life. In addition, the present invention also provides a switch power tube driver chip, which also has the above-mentioned beneficial effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0030] Figure 1 A structural block diagram of a switch power tube cutoff control circuit provided by an embodiment of the present invention;

[0031] Figure 2 A structural block diagram of another switch power tube cutoff control circuit provided by an embodiment of the present invention;

[0032] Figure 3 A signal schematic diagram of a turn-on voltage drop of a first controllable switch provided by an embodiment of the present invention;

[0033] Figure 4 This is a structural block diagram of a switching power tube driver chip provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] Please refer to Figure 1 , Figure 1 This is a structural block diagram of a switch power tube cutoff control circuit provided by an embodiment of the present invention. The circuit may include: a first controllable switch 10, a voltage drop detection circuit 20 and a switch controller 30;

[0036] The first controllable switch 10 is coupled to the switch power tube, and the switch power tube is controlled to be turned off when the first controllable switch 10 is turned on;

[0037] The input end of the voltage drop detection circuit 20 is controllably connected to the first controllable switch 10 in the conduction phase of the first controllable switch 10, and detects the conduction voltage drop of the first controllable switch 10 when connected; and when the conduction voltage drop of the first controllable switch 10 is greater than or equal to the first reference voltage, a forced conduction signal is output until the conduction voltage drop of the first controllable switch 10 is less than the second reference voltage;

[0038] The first input end of the switch controller 30 is connected to the output end of the voltage drop detection circuit 20, and the output end of the switch controller 30 is connected to the control end of the first controllable switch 10; the switch controller 30 is used to receive a forced conduction signal and an input conduction signal, and control the conduction time of the first controllable switch 10 based on the signal with the longest time.

[0039] It is understandable that the switch controller 30 in this embodiment can drive and control the on and off (i.e., off) of the switch power tube by controlling the on and off of the first controllable switch 10 coupled to the switch power tube. In other words, the switch power tube can be off when the first controllable switch 10 is on, and can be on when the first controllable switch 10 is off.

[0040] Correspondingly, the specific coupling connection mode between the first controllable switch 10 and the switch power tube in this embodiment can be set by the designer according to practical scenarios and user needs. For example, when the input end of the voltage drop detection circuit 20 is connected to the first controllable switch 10 in the conduction stage of the first controllable switch 10, the input end of the voltage drop detection circuit 20 can be connected to the first end of the first controllable switch 10, and the common end of the connection can be connected to the control end of the switch power tube. The common end can be used as a voltage drop detection end for detecting the conduction voltage drop of the first controllable switch 10, so that the voltage drop detection circuit 20 can detect the conduction voltage drop (i.e., voltage) of the first controllable switch 10 through the voltage drop detection end, and determine the current that drives the switch power tube when the first controllable switch 10 is turned on, thereby correspondingly controlling the conduction and cutoff of the switch power tube. For example, if Figure 2 As shown, the first end of the first controllable switch 10 (T2) is connected to the power supply end (VCC) through the second controllable switch (T1), the common end of the first end of the first controllable switch 10 and the second controllable switch is connected to the control end of the switch power tube, and the second end of the first controllable switch 10 is connected to one end of the switch power tube and grounded. Correspondingly, the first end of the first controllable switch 10 can also be directly connected to the power supply end or the output end of the external power supply circuit, and the second end of the first controllable switch 10 can also be grounded through other circuit elements (such as a resistor), and this embodiment does not impose any restrictions on this.

[0041] It should be noted that the voltage drop detection circuit 20 in this embodiment can be used to output a corresponding safety drive signal according to the comparison between the on-state voltage drop of the first controllable switch 10 and the first reference voltage and the second reference voltage, so as to output a safety drive signal (i.e., a forced on-state signal) for controlling the first controllable switch 10 to turn on when the on-state voltage drop is greater than or equal to the first reference voltage, until the on-state voltage drop is less than the second reference voltage, thereby ensuring that the current driving the switch power tube when the first controllable switch 10 is turned off is small enough; when the on-state voltage drop is less than the second reference voltage, the safety drive signal for controlling the first controllable switch 10 to turn off is output. In other words, the voltage drop detection circuit 20 can output a safety drive signal as a forced on-state signal when the voltage at the voltage drop detection terminal (i.e., the on-state voltage drop) is greater than or equal to the first reference voltage, and control the first controllable switch 10 to turn on, so as to reduce the voltage at the voltage drop detection terminal; when the voltage at the subsequent voltage drop detection terminal is less than the second reference voltage, the output safety drive signal is adjusted to a turn-off signal, so that the first controllable switch 1020 can maintain the on-state or switch off according to the control requirements of the switch power tube. This embodiment does not impose any limitation on this.

[0042] Correspondingly, the first reference voltage in this embodiment can be greater than the second reference voltage to ensure that the current driving the switch power tube is sufficiently small when the first controllable switch 10 is turned off. The input end of the voltage drop detection circuit 20 in this embodiment can be controllably connected to the first controllable switch 10 when the first controllable switch 10 is turned on, so as to detect the conduction voltage drop of the first controllable switch 10 when connected. Figure 2 As shown, the switch power tube cut-off control circuit provided in this embodiment may further include a conduction time controller; wherein, the input end of the voltage drop detection circuit 20 is connected to the first controllable switch 10 through the conduction time controller, and the conduction time controller controls the first controllable switch 10 to be connected to the voltage drop detection circuit 20 during the entire time or part of the time when it is in the conduction state; that is, the input end of the voltage drop detection circuit 20 may be connected to one end of the first controllable switch 10 that serves as the voltage drop detection end (i.e., the end connected to the control end of the switch power tube) through the conduction time controller, so that the input end of the voltage drop detection circuit 20 can be connected to the first controllable switch 10 during the entire time or part of the time when the first controllable switch 10 is in the conduction state, thereby detecting the conduction voltage drop of the first controllable switch 10.

[0043] Accordingly, the specific on-time of the on-time controller can be set by the designer according to practical scenarios and user needs. For example, the on-time controller can be turned on at the same time as the first controllable switch 10 is turned on, and the on-time of the on-time controller can be less than or equal to the on-time of the first controllable switch 10; for example, the on-time of the on-time controller can be the same as the on-time of the first controllable switch 10, so that the input end of the voltage drop detection circuit 20 can be connected to the first controllable switch 10 during the entire time when the first controllable switch 10 is in the on state. The on-time controller can also be turned on for a preset set time (such as 20ns), that is, the above part of the time can be within the set time after the first controllable switch 10 is turned on. The on-time controller can also be turned on in the time period from the first controllable switch 10 being turned on to the time when the on-voltage drop of the first controllable switch 10 reaches a peak value, that is, the above part of the time can be from the time when the first controllable switch 10 is turned on to the time when the on-voltage drop of the first controllable switch 10 reaches a peak value.

[0044] For example, the on-state voltage drop of the first controllable switch 10 can be as follows: Figure 3 As shown, the on-time controller can be turned on at the same time as the first controllable switch 10 is turned on, and the on-voltage drop of the first controllable switch 10 reaches a peak value (such as Figure 3 For example, by taking the derivative of the difference between two consecutive on-state voltage drops detected, the moment when the on-state voltage drop of the first controllable switch 10 reaches the peak value is determined. For example, when the derivative result is 0, it is determined that the on-state voltage drop of the first controllable switch 10 reaches the peak value.

[0045] Among them, the specific circuit structure of the voltage drop detection circuit 20 in this embodiment can be set by the designer. For example, the voltage drop detection circuit 20 can include a comparator circuit for comparing the on-state voltage drop of the first controllable switch input at the first input terminal with the first reference voltage or the second reference voltage input at the second input terminal; when the on-state voltage drop is greater than the first reference voltage or the second reference voltage, a first level signal (i.e., a forced on-state signal) is output to the first input terminal of the switch controller 30; when the on-state voltage drop is less than the first reference voltage or the second reference voltage, a second level signal is output. Accordingly, when the comparator circuit outputs a first level signal, the second input terminal of the comparator circuit can input the second reference voltage; when the comparator circuit outputs a second level signal, the second input terminal of the comparator circuit can input the first reference voltage.

[0046] Correspondingly, in order to realize the automatic switching of the first reference voltage or the second reference voltage inputted at the second input terminal of the comparator circuit, the voltage drop detection circuit 20 may also include: a comparator circuit and a reference voltage output circuit; wherein the first input terminal of the comparator circuit is connected to the voltage drop detection terminal through a conduction controller, and the voltage drop detection terminal is an end of the first controllable switch 10 used to be connected to the control terminal of the switch power tube; the conduction time controller is used to conduct the connection between the first input terminal of the comparator circuit and the voltage drop detection terminal when the first controllable switch 10 is turned on; the output terminal of the comparator circuit is connected to the control terminal of the reference voltage output circuit, and the first reference voltage output terminal and the second reference voltage output terminal of the reference voltage output circuit are both connected to the second input terminal of the comparator circuit; the reference voltage output The circuit is used to output a first reference voltage to the second input terminal of the comparator circuit when the comparator circuit outputs a first level signal; output a second reference voltage to the second input terminal of the comparator circuit when the comparator circuit outputs a second level signal; the comparator circuit is used to output a first level signal when the voltage (i.e., the on-state voltage drop) of the voltage drop detection terminal input at the first input terminal is greater than the first reference voltage or the second reference voltage input at the second input terminal; output a second level signal when the voltage of the voltage drop detection terminal input at the in-phase input terminal is less than the first reference voltage or the second reference voltage input at the inverting input terminal; the common terminal of the output terminal of the comparator circuit connected to the control terminal of the reference voltage output circuit is connected to the first input terminal of the switch controller 30 as the output terminal of the voltage drop detection circuit 20.

[0047] For example, the above-mentioned comparator circuit may include an operational amplifier; wherein, when the forced conduction signal is a high-level signal, the non-inverting input terminal of the operational amplifier is connected to the voltage drop detection terminal through the conduction controller, the inverting input terminal of the operational amplifier is connected to the first reference voltage output terminal and the second reference voltage output terminal of the reference voltage output circuit, and the output terminal of the operational amplifier is connected to the control terminal of the reference voltage output circuit; the reference voltage output circuit is used to output a first reference voltage to the inverting input terminal of the operational amplifier when the operational amplifier outputs a high-level signal; and output a second reference voltage to the inverting input terminal of the operational amplifier when the operational amplifier outputs a low-level signal. Correspondingly, when the forced conduction signal is a low-level signal, it can be set up in a manner corresponding to the above-mentioned connection manner, as long as it is ensured that the reference voltage output circuit can switch the output voltage of the operational amplifier from the first reference voltage to the second reference voltage when the conduction voltage drop of the first controllable switch 10 is greater than or equal to the first reference voltage, so that the operational amplifier can output the forced conduction signal (i.e., the above-mentioned first-level signal) when the conduction voltage drop of the first controllable switch 10 is greater than or equal to the first reference voltage, until the conduction voltage drop of the first controllable switch 10 is less than the second reference voltage. This embodiment does not impose any restrictions on this.

[0048] Correspondingly, such as Figure 2As shown, the reference voltage output circuit may include: a first reference voltage circuit, a second reference voltage circuit, an inverter (U2), a first reference voltage switch (S2) and a second reference voltage switch (S1); wherein the control end of the second reference voltage switch is connected to the output end of the operational amplifier as the control end of the reference voltage output circuit, and its common end is connected to the control end of the first reference voltage switch through the inverter; the inverting input end of the operational amplifier is respectively connected to the first end of the first reference voltage circuit and the second reference voltage circuit; the second ends of the first reference voltage circuit and the second reference voltage circuit are grounded; the first reference voltage switch and the second reference voltage switch are used to be turned on when a high level signal is input to the control end, and turned off when a low level signal is input to the control end; the operational amplifier is specifically used to detect the voltage at the voltage drop detection end input at the same phase input end When the voltage at the voltage drop detection terminal input at the non-inverting input terminal is less than the first reference voltage (VREF2) input at the inverting input terminal, a low-level signal is output to turn off the second reference voltage switch and turn on the first reference voltage switch, so that the first reference voltage provided by the first reference voltage circuit is input at the inverting input terminal; when the voltage at the voltage drop detection terminal input at the non-inverting input terminal is greater than the first reference voltage input at the inverting input terminal, a high-level signal is output to turn on the second reference voltage switch and turn off the first reference voltage switch, so that the second reference voltage (VREF1) provided by the second reference voltage circuit is input at the inverting input terminal; when the voltage at the voltage drop detection terminal input at the non-inverting input terminal is less than the second reference voltage input at the inverting input terminal, a low-level signal is output to turn on the first reference voltage switch and turn off the second reference voltage switch, so that the first reference voltage provided by the first reference voltage circuit is input at the inverting input terminal.

[0049] It can be understood that the switch controller 30 in this embodiment can output a corresponding final drive signal to the control end of the first controllable switch 10 according to the input first control signal for controlling the on and off of the switch power tube and the safety drive signal output by the voltage drop detection circuit 20, so as to drive the on and off of the first controllable switch 10 and control the on and off of the switch power tube accordingly. Among them, the first control signal is an externally input control signal for controlling the on and off of the switch power tube through the switch power tube cut-off control circuit (such as Figure 2 VIN in the output); the final driving signal can be the driving signal that the switch controller 30 finally outputs to the control end of the first controllable switch 10; that is, the switch controller 30 can control the conduction and shutdown of the first controllable switch 10 according to the input first control signal and the safety driving signal, thereby adjusting the voltage of the voltage drop detection end of the switch power tube cutoff control circuit, that is, the voltage (or current) output to the control end of the switch power tube, correspondingly driving the conduction and shutdown of the switch power tube. That is to say, the second input end of the switch controller 30 in this embodiment can be connected to the output end of the input conduction signal (such as the first control signal output end).

[0050] Correspondingly, when the switch controller 30 receives a forced on-signal and an input on-signal, the on-time of the first controllable switch 10 can be controlled based on the signal with the longest time. That is, when the safety drive signal is a forced on-signal, regardless of whether the first control signal drives the first controllable switch 10 to be turned on by an input on-signal or drives the first controllable switch 10 to be cut off by an input off-signal, the final drive signal output by the switch controller 30 is a on-signal to maintain the conduction of the first controllable switch 10 and reduce the voltage at the voltage drop detection end.

[0051] Further, in some embodiments, the switch controller 30 may specifically receive a forced conduction signal, an input conduction signal, and a minimum conduction time control signal, and control the conduction time of the first controllable switch 10 based on the signal with the longest time; wherein the minimum conduction time control signal may be a signal for controlling the conduction time of the first controllable switch 10 to be greater than or equal to a preset time. In other words, the third input terminal of the switch controller 30 may be connected to the output terminal of the minimum conduction time control signal, and the input of the minimum conduction time control signal may be controlled by the switch controller 30 to ensure that the conduction time of the first controllable switch 10 (i.e., the off time of the switch power tube) is greater than or equal to the specified minimum time (i.e., the preset time).

[0052] like Figure 2 As shown, the switch power tube cut-off control circuit provided in this embodiment may also include a minimum off-time controller, which is used to output a minimum on-time control signal of a preset time to the switch controller 30. For example, the output end of the minimum off-time controller may be connected to the third input end of the switch controller 30, and the switch controller 30 may output a corresponding final drive signal to the control end of the first controllable switch 10 according to the second control signal, the first control signal and the safety drive signal output by the minimum off-time controller; that is, when the second control signal is the minimum on-time control signal for driving the first controllable switch 10 to turn on or the safety drive signal is a forced on-signal, regardless of whether the first control signal input externally for controlling the first controllable switch 10 is a turn-on signal (i.e., an input turn-on signal) or a turn-off signal, the final drive signal is controlled to be a turn-on signal to maintain the turn-on of the first controllable switch 10.

[0053] It should be noted that the specific switch types of the first controllable switch 10, the second controllable switch and the switch power tube in this embodiment can be set by the designer according to practical scenarios and user needs. For example, the first controllable switch 10, the second controllable switch and the switch power tube can be power triodes, power MOSFETs (metal oxide semiconductor field effect transistors) and IGBTs (insulated gate bipolar transistors). Figure 2As shown, the first controllable switch 10 (T2) can be an NMOS transistor, and the second controllable switch (T1) can be a PMOS transistor; the drain of the second controllable switch is connected to the power supply terminal, the source of the second controllable switch is connected to the drain of the first controllable switch 10, the source of the first controllable switch 10 is grounded, and the gates of the second controllable switch and the first controllable switch 10 are connected to the output terminal of a switch controller 30 (such as Figure 2 the adder in

[0054] For example, as Figure 2 shown, before the T2 transistor (i.e., the first controllable switch 10) is turned on, the reference voltage at the inverting input terminal of the operational amplifier U1 is VREF2 (i.e., the first reference voltage); when the T2 transistor is turned on, the external T3 transistor (i.e., the switching power transistor) is turned off; the Time Controller (on-time controller) switch is also turned on at the same time. At this time, the on-state voltage drop of the T2 transistor can be detected at the non-inverting input terminal of U1; there are two durations for controlling the on-time of the Time Controller. One is to turn on for 20 ns, and the other is to turn on during the on-time of the T2 transistor; during the on-time of the Time Controller, if the on-state voltage drop of the T2 transistor exceeds VREF2, the output of U1 will flip, and at the same time, the reference voltage at the inverting input terminal of U1 becomes VREF1 (i.e., the second reference voltage), and VREF1 < VREF2. In this way, the T2 transistor will be locked in the on state; only when the on-state voltage drop of the T2 transistor is less than VREF1, the output state of U1 will return to the original state, and at this time, the conduction of T2 will be released and controlled by other signals (such as the first control signal VIN and the second control signal of the minimum off-time controller Min Off Controller).

[0055] It should be noted that the switching power transistor cut-off control circuit provided in this embodiment can be arranged in a switching power transistor drive chip (such as a gate isolation drive chip) for driving the conduction and cut-off of the switching power transistor, that is, the input conduction signal input by the switch controller 30 can be a control signal for controlling the cut-off of the switching power transistor input externally to the switching power transistor drive chip; that is to say, the above-mentioned first control signal can be a control signal for controlling the conduction or cut-off of the switching power transistor input externally to the switching power transistor drive chip. For example, Figure 2The switch power tube cut-off control circuit shown can be set in the gate isolation driver chip, so that the gate isolation driver chip can control the conduction time of the first controllable switch 10 (T2) based on the input conduction signal input from the outside and the generated forced conduction signal and the minimum conduction time control signal, and correspondingly control the cut-off time of the switch power tube (T3) connected to the gate isolation driver chip. Correspondingly, the switch power tube cut-off control circuit provided in this embodiment can also be directly applied to devices such as inverters, chargers or motor drivers, that is, the input conduction signal input by the switch controller 30 can be a control signal directly input to the switch controller 30 from the outside of the circuit.

[0056] In this embodiment, the embodiment of the present invention uses a voltage drop detection circuit 20 to detect the current output to the driven switch power tube when the first controllable switch 10 is turned on, so as to ensure that when the on-off state of the switch power tube is switched by turning off the first controllable switch 10, the output current is small enough, thereby reducing the oscillation voltage generated on the parasitic inductance, and being able to fully discharge the voltage of the capacitive load to avoid the situation where the load cannot be turned off, and being able to reduce the influence of the parasitic inductance of the line between the control circuit and the switch power tube on the drive of the switch power tube, thereby improving the safety of circuit use and the life of components.

[0057] Corresponding to the above circuit embodiment, the embodiment of the present invention further provides a switch power tube driver chip. The switch power tube driver chip described below and the switch power tube cutoff control circuit described above can refer to each other.

[0058] Please refer to Figure 4 , Figure 4 This is a structural block diagram of a switch power tube driver chip provided by an embodiment of the present invention. The switch power tube driver chip may include: a switch power tube cutoff control circuit 100 provided by the above circuit embodiment.

[0059] Among them, this embodiment does not limit the specific chip type of the switching power tube driver chip. For example, the switching power tube driver chip can be a gate isolation driver chip, or it can be other driver chips used to drive the switching power tube used in inverters, chargers or motor drivers.

[0060] The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other. For the chip disclosed in the embodiment, since it corresponds to the circuit disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the circuit part description.

[0061] The above is a detailed introduction to a switch power tube cutoff control circuit and a driver chip provided by the present invention. This article uses specific examples to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present invention, the present invention can also be improved and modified in a number of ways, and these improvements and modifications also fall within the scope of protection of the present invention.

Claims

1. A switch power tube cut-off control circuit, characterized in that: include: a first controllable switch, a voltage drop detection circuit and a switch controller; Wherein, the first controllable switch is coupled to the switch power tube, and the switch power tube is controlled to be turned off when the first controllable switch is turned on; The input end of the voltage drop detection circuit is controllably connected to the first controllable switch in a conduction phase of the first controllable switch, and detects the conduction voltage drop of the first controllable switch when connected; and when the conduction voltage drop of the first controllable switch is greater than or equal to a first reference voltage, outputs a forced conduction signal until the conduction voltage drop of the first controllable switch is less than a second reference voltage; The first input end of the switch controller is connected to the output end of the voltage drop detection circuit, and the output end of the switch controller is connected to the control end of the first controllable switch; the switch controller is used to receive the forced conduction signal and the input conduction signal, and control the conduction time of the first controllable switch based on the signal with the longest time.

2. The switch power tube cut-off control circuit according to claim 1, characterized in that: Also includes: On-time controller; The input end of the voltage drop detection circuit is connected to the first controllable switch through the on-time controller, and the on-time controller controls the first controllable switch to be connected to the voltage drop detection circuit all or part of the time in the on-state.

3. The switch power tube cut-off control circuit according to claim 2, characterized in that: The portion of time is from when the first controllable switch is turned on to when the on-state voltage drop of the first controllable switch reaches a peak value.

4. The switch power tube cut-off control circuit according to claim 2, characterized in that: The part of time is the set time after the first controllable switch is turned on.

5. The switch power tube cut-off control circuit according to claim 2, characterized in that: The voltage drop detection circuit comprises: a comparator circuit and a reference voltage output circuit; The first input end of the comparator circuit is connected to the voltage drop detection end through the conduction controller, and the voltage drop detection end is an end of the first controllable switch used to be connected to the control end of the switch power tube; the conduction time controller is used to conduct the connection between the first input end of the comparator circuit and the voltage drop detection end when the first controllable switch is turned on; The output end of the comparator circuit is connected to the control end of the reference voltage output circuit, and the first reference voltage output end and the second reference voltage output end of the reference voltage output circuit are both connected to the second input end of the comparator circuit; The reference voltage output circuit is used to output a first reference voltage to the second input terminal of the comparator circuit when the comparator circuit outputs a first level signal; and output a second reference voltage to the second input terminal of the comparator circuit when the comparator circuit outputs a second level signal; The comparator circuit is used to output a first level signal when the voltage of the voltage drop detection terminal input at the first input terminal is greater than the first reference voltage or the second reference voltage input at the second input terminal; and output a second level signal when the voltage of the voltage drop detection terminal input at the in-phase input terminal is less than the first reference voltage or the second reference voltage input at the inverting input terminal; The common end of the output end of the comparator circuit connected to the control end of the reference voltage output circuit is connected to the first input end of the switch controller as the output end of the voltage drop detection circuit.

6. The switch power tube cut-off control circuit according to claim 5, characterized in that: The comparator circuit comprises: an operational amplifier; wherein the forced conduction signal is a high-level signal; the non-inverting input terminal of the operational amplifier is connected to the voltage drop detection terminal through the conduction controller, the inverting input terminal of the operational amplifier is connected to the first reference voltage output terminal and the second reference voltage output terminal of the reference voltage output circuit, and the output terminal of the operational amplifier is connected to the control terminal of the reference voltage output circuit; The reference voltage output circuit is used to output a first reference voltage to the inverting input terminal of the operational amplifier when the operational amplifier outputs a high level signal; and to output a second reference voltage to the inverting input terminal of the operational amplifier when the operational amplifier outputs a low level signal.

7. The switch power tube cut-off control circuit according to claim 6, characterized in that: The reference voltage output circuit comprises: a first reference voltage circuit, a second reference voltage circuit, an inverter, a first reference voltage switch and a second reference voltage switch; Wherein, the control end of the second reference voltage switch is connected to the output end of the operational amplifier as the control end of the reference voltage output circuit, and its common end is connected to the control end of the first reference voltage switch through the inverter; the inverting input end of the operational amplifier is connected to the first end of the first reference voltage circuit and the second reference voltage circuit respectively; the second ends of the first reference voltage circuit and the second reference voltage circuit are grounded; the first reference voltage switch and the second reference voltage switch are used to be turned on when a high level signal is input to the control end, and turned off when a low level signal is input to the control end; The operational amplifier is specifically used to output a low-level signal to turn off the second reference voltage switch and turn on the first reference voltage switch when the voltage of the voltage drop detection terminal input at the non-phase input terminal is less than the first reference voltage input at the inverting input terminal, so that the first reference voltage provided by the first reference voltage circuit is input at the inverting input terminal; output a high-level signal to turn on the second reference voltage switch and turn off the first reference voltage switch when the voltage of the voltage drop detection terminal input at the non-phase input terminal is greater than the first reference voltage input at the inverting input terminal, so that the second reference voltage provided by the second reference voltage circuit is input at the inverting input terminal; output a low-level signal to turn on the first reference voltage switch and turn off the second reference voltage switch when the voltage of the voltage drop detection terminal input at the non-phase input terminal is less than the second reference voltage input at the inverting input terminal, so that the first reference voltage provided by the first reference voltage circuit is input at the inverting input terminal.

8. The switch power tube cut-off control circuit according to claim 1, characterized in that: Also includes: a second controllable switch; Among them, the first end of the first controllable switch is connected to the power supply end through the second controllable switch, the common end connected to the first end of the first controllable switch and the second controllable switch is connected to the control end of the switch power tube, and the second end of the first controllable switch is connected to one end of the switch power tube and grounded.

9. The switch power tube cutoff control circuit according to any one of claims 1 to 8, characterized in that: The switch controller is specifically configured to receive the forced conduction signal, the input conduction signal and the minimum conduction time control signal, and control the conduction time of the first controllable switch based on the signal with the longest time.

10. A switch power tube driver chip, characterized in that: include: A switch power tube cut-off control circuit as claimed in any one of claims 1 to 9.

Images