CN111786356B - High-side switch circuit - Google Patents
High-side switch circuit Download PDFInfo
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- CN111786356B CN111786356B CN202010767684.3A CN202010767684A CN111786356B CN 111786356 B CN111786356 B CN 111786356B CN 202010767684 A CN202010767684 A CN 202010767684A CN 111786356 B CN111786356 B CN 111786356B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/08—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current
- H02H3/087—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current for dc applications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H5/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal non-electric working conditions with or without subsequent reconnection
- H02H5/04—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal non-electric working conditions with or without subsequent reconnection responsive to abnormal temperature
- H02H5/041—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal non-electric working conditions with or without subsequent reconnection responsive to abnormal temperature additionally responsive to excess current
Abstract
The invention relates to a high-side switch circuit, and belongs to the technical field of electronics and power supplies. The high-side switching circuit includes: a third switching tube Q3 serially connected toThe control end of the power supply circuit is connected with the power supply end; driving circuit of the third switching tube Q3: the driving control circuit comprises a second switching tube Q2 connected with a third switching tube Q3, and a first switching tube Q1 connected with a second switching tube Q2; the ON end is connected with the control end of the second switching tube Q2; an OFF end connected with the control end of the first switching tube Q1; still include protection circuit and auto-lock circuit: one end of the protection circuit is connected with the output end, the other end of the protection circuit is connected with one end of a second switching tube Q2 which is in drive control connection with a third switching tube Q3, and a divider resistor R8 and a thermistor R with a negative temperature coefficient are connected in series on the protection circuitNTC(ii) a One end of the self-locking circuit is connected with the divider resistor R8 and the thermistor RNTCAnd the other end of the voltage division point is connected with the control end of the second switching tube Q2. The invention reliably realizes the overcurrent/overtemperature protection of the high-side switch circuit.
Description
Technical Field
The invention relates to a high-side switch circuit, and belongs to the technical field of electronics and power supplies.
Background
The current known high-side switch chip for the vehicle can basically cover the control and protection of all loads with the current less than or equal to 10A, and for the loads with the current more than 10A, the high-side switch chip has higher cost and less use; for loads with current more than 20A, no corresponding high-side switch chip exists at present, and loads with current more than 20A can only be controlled by using a relay and are short-circuit protected by using a fuse. As is known, the relay has the disadvantages of large volume, heavy weight, short service life, poor reliability and the like, and the fuse has the disadvantages of slow protection, inaccurate protection, replacement after being burnt and the like during protection, and is not suitable for the automobile equipment with high requirements on real-time performance, reliability and accuracy.
Therefore, in order to solve the problem of vehicle large current control, the automobile industry generally adopts a design scheme of an MOS tube and a driving chip, and overcurrent and short-circuit protection is realized through an additional hardware circuit. In the design scheme, the driving chip is expensive, and the standby current is higher and generally higher than 20 mA; in addition, the driving chip needs a microcontroller MCU to input a level signal to maintain the opening of the MOS tube, and the coupling degree of the level signal and the microcontroller MCU is high, so that the decoupling of faults is not facilitated. Such circuits are not only very costly but also have high requirements on the use specifications.
For this reason, there has been proposed a switching circuit which does not require a driving chip, for example: the application publication number is CN 111049509 a, which discloses a self-locking switch circuit and a power module, wherein the self-locking switch circuit is built by using MOS transistors, has a self-locking function, and can be controlled to be turned on and off by positive pulse signals.
However, the self-locking switch circuit of the above application document cannot realize protection, resulting in lower reliability.
Disclosure of Invention
An object of the present application is to provide a high-side switch circuit for solving the problem of low reliability of the existing switch circuit.
In order to achieve the above object, the present application provides a technical solution of a high-side switching circuit, including:
the third switching tube Q3 is used for being connected between a power supply end and an output end in series; the control end of the third switching tube Q3 is used for connecting a power supply end;
the driving circuit of the third switching tube Q3 comprises a second switching tube Q2 and a first switching tube Q1, and the first switching tube Q1 is in driving control connection with the second switching tube Q2; the second switching tube Q2 is in driving control connection with a third switching tube Q3;
the ON end is connected with the control end of the second switching tube Q2;
an OFF end connected with the control end of the first switching tube Q1;
the protection circuit and the self-locking circuit are used for providing a feedback signal to realize continuous conduction of the second switching tube Q2:
one end of the protection circuit is connected with the output end, the other end of the protection circuit is connected with one end of a second switching tube Q2 which is in drive control connection with a third switching tube Q3, and a divider resistor R8 and a thermistor R with a negative temperature coefficient are connected in series on the protection circuitNTC(ii) a The thermistor RNTCThe temperature of the third switching tube Q3 is acquired;
one end of the self-locking circuit is connected with the divider resistor R8 and the thermistor RNTCAnd the other end of the voltage division point is connected with the control end of the second switching tube Q2.
The technical scheme of the high-side switching circuit has the beneficial effects that: the high-side switch circuit is provided with a protection circuit, and a thermistor R with a negative temperature coefficient is connected in series on the protection circuitNTCI.e., the higher the temperature, the lower the resistance; over-current occurs in the high-side switching circuitWhen the current or the over-temperature is failed, the temperature of the third switching tube Q3 is increased, and the thermistor R is causedNTCThe temperature rises so that the thermistor RNTCResistance reduction of (2), thermistor RNTCAfter the resistance of (2) is reduced, the voltage dividing resistor R8 and the thermistor RNTCThe voltage of the voltage division point is reduced, the feedback voltage fed back to the second switching tube Q2 is reduced, the second switching tube Q2 cannot be conducted, the voltage of the control end of the third switching tube Q3 is increased, and the third switching tube Q3 is turned off, so that the overcurrent/overtemperature protection of the high-side switching circuit is reliably realized.
Further, in order to realize output short-circuit protection, a voltage regulator tube D3 is further arranged on the protection circuit, the cathode of the voltage regulator tube D3 is connected with the output end, and the anode of the voltage regulator tube D3 is connected with the voltage dividing resistor R8.
Furthermore, in order to protect the third switching tube Q3, a first voltage dividing circuit is arranged between one end of the second switching tube Q2 which is in drive control connection with the third switching tube Q3 and a power supply end, and a resistor R5 and a resistor R are connected in series on the first voltage dividing branchQ3The control end of the third switching tube Q3 is connected with a resistor R5 and a resistor RQ3And at the voltage division point, two ends of the resistor R5 are connected in parallel with a voltage regulator tube D2 for performing overvoltage protection on the third switch tube Q3.
Further, in order to reduce the feedback signal and protect the second switching tube Q2, a resistor R7 is provided on the self-locking circuit for limiting the feedback current.
Further, in order to protect the second switch tube Q2, a resistor Rin is disposed between the ON terminal and the control terminal of the second switch tube Q2, and the resistor Rin performs a current limiting protection function ON the second switch tube Q2.
Further, in order to protect the second switching transistor Q2, a resistor R4 is disposed between the control terminal of the second switching transistor Q2 and ground, and is used for providing a stable level for the control terminal of the second switching transistor Q2.
Further, in order to filter the input signal, a capacitor Cin is disposed between the control terminal of the second switching tube Q2 and ground, and is used for filtering the input signal.
Further, in order to protect the second switching tube Q2, a voltage regulator tube D1 is arranged between the control end of the second switching tube Q2 and the ground, the cathode of the voltage regulator tube D1 is connected with the control end of the second switching tube Q2, and the anode of the voltage regulator tube D1 is grounded and used for protecting the control end of the second switching tube Q2, so that overvoltage is prevented from being generated.
Further, in order to protect the first switch tube Q1, a second voltage dividing branch is connected in series between the OFF terminal and the ground, and a voltage dividing point of the second voltage dividing branch is connected with the control terminal of the first switch tube Q1.
Furthermore, in order to improve the reliability of the high-side switching circuit, the third switching tube Q3 is one or more P-type MOS tubes connected in parallel.
Drawings
FIG. 1 is a circuit block diagram of the high side switching circuit of the present invention;
FIG. 2 is a timing diagram of the operation of the high side switching circuit of the present invention;
fig. 3 is a flow chart of the design of the high-side switching circuit of the present invention.
Detailed Description
High side switching circuit embodiment:
the high-side switching circuit is shown in fig. 1 and includes: the third switch tube Q3, a driving circuit of the third switch tube Q3, an ON terminal, an OFF terminal, a power supply terminal, an output terminal, a protection circuit and a self-locking circuit.
The third switching tube Q3 is a MOS tube Q3, and is serially connected between a power supply end and an output end, the power supply end is used for connecting a power supply VBAT, and the output end is used for connecting a load, specifically, a source electrode S of the MOS tube Q3 is connected with the power supply end, and a drain electrode D output of the MOS tube Q3 is connected with the output end; the control end of the MOS transistor Q3 is connected with a power supply end through a resistor R5, a resistor R5 and a resistor RQ3A first voltage-dividing branch circuit is formed and is arranged between the power supply end and the driving circuit of the third switching tube Q3, a resistor R5 and a resistor RQ3Is connected to the gate G of the MOS transistor Q3 (i.e., the control terminal of the MOS transistor Q3). Meanwhile, a voltage regulator tube D2 is connected in parallel with the two ends of the resistor R5, the cathode of the voltage regulator tube D2 is connected with the source S of the MOS tube Q3, and the anode of the voltage regulator tube D2 is connected with the gate G of the MOS tube Q3.
The driving circuit of the MOS transistor Q3 comprises a second switching tube Q2 and a first switching tube Q1, wherein the first switching tube Q1 is in driving control connection with the second switching tube Q2; the second switch tube Q2 is connected with the third switch tube Q3 in a driving control mode. The method specifically comprises the following steps:
the second switch transistor Q2 is a MOS transistor Q2, and a drain D of the MOS transistor Q2 (i.e., one end of the driving control connection MOS transistor Q3) is connected to a resistor RQ3The source S of the MOS transistor Q2 is grounded; the gate G of the MOS transistor Q2 (namely the control end of the MOS transistor Q2) is connected with the ON end through a resistor Rin; the ON end is used for receiving an ON signal;
the first switching tube Q1 is a triode Q1, a base B (i.e., a control end) of the triode Q1 is connected to the OFF end through a resistor R2, a resistor R2 and a resistor R3 form a second voltage division branch which is arranged between the OFF end and the ground, and the base B of the triode Q1 is connected to the voltage division point of the resistor R2 and the resistor R3; a collector C (namely one end of the drive control connection MOS tube Q2) of the triode Q1 is connected with a gate G of the MOS tube Q2, and an emitter E of the triode Q1 is grounded; the OFF terminal is used for receiving an OFF signal;
meanwhile, a resistor R4, a capacitor Cin and a voltage regulator tube D1 which are connected in parallel are further arranged between the control end of the MOS tube Q2 and the ground, the cathode of the voltage regulator tube D1 is connected with the control end of the MOS tube Q2, and the anode of the voltage regulator tube D1 is grounded.
The protection circuit can realize overcurrent, overtemperature and output short-circuit protection, and is provided with a voltage regulator tube D3, a resistor R8 (namely a divider resistor which can be one or more resistors connected in series) and a thermistor R which are connected in seriesNTC(negative temperature coefficient thermistor), resistor R8 and thermistor RNTCSeries voltage-dividing thermistor RNTCIs arranged in the vicinity of the MOS transistor Q3 to detect the temperature of the MOS transistor Q3. Thermistor RNTCThe high-side switch MOS transistor Q3 is arranged near the MOS transistor Q3 as much as possible, and the thermal resistance between the high-side switch MOS transistor Q3 and the MOS transistor Q3 needs to be designed as small as possible, so that the junction temperature of the MOS transistor Q3 and the thermistor RNTCThe temperature difference Δ T of (a) is as small as possible. One end of the protection circuit is connected with the output end, and the other end is connected with a drain D of an MOS transistor Q2, specifically, a thermistor RNTCOne end of the diode is connected with a resistor R8, the other end of the diode is connected with a drain electrode D of a MOS tube Q2, the anode of a voltage stabilizing tube D3 is connected with a resistor R8, and the cathode of a voltage stabilizing tube D3 is connected with an output end.
The self-locking circuit is provided with a resistor R7, and one end of the resistor R7 is connected with the resistor R8 and the thermosensitive resistorResistance RNTCAnd the other end of the voltage division point is connected with a gate G of the MOS transistor Q2.
The functions of the devices in the high-side switching circuit are as follows:
the resistor Rin plays a role in current limiting protection of the MOS transistor Q2; the resistor R4 is used for providing a stable level for the gate G of the MOS transistor Q2; the capacitor Cin has a filtering effect on an input signal and is used together with the resistor Rin to adjust the delay opening time of the high-side switch circuit; the voltage regulator tube D1 is used for protecting the gate G of the MOS tube Q2 and ensuring that overvoltage cannot be generated; the capacitor Cin has a filtering effect on an input signal and is used together with the resistor Rin to adjust the delay opening time of the high-side switch;
the resistor R2 plays a role in current-limiting protection of the triode Q1, the resistor R3 is used for ensuring reliable control of the triode Q1, and the resistor R2 and the resistor R3 form a second voltage division circuit together to protect the base B of the triode Q1 from generating overvoltage;
the MOS tube Q3 is used for controlling the output and the turn-off of the power supply VBAT; the MOS transistor Q2 is used for controlling the conduction state of the MOS transistor Q3; the triode Q1 is used for controlling the conducting state of the MOS transistor Q2; the voltage regulator tube D2 plays an overvoltage protection role in the MOS tube Q3; the resistor R5 provides a stable pull-up power supply for the MOS transistor Q3; resistance RQ3The current limiting protection effect on the MOS transistor Q3 is achieved, and the rising edge time of the MOS transistor Q3 can be adjusted while current is limited; the voltage regulator tube D3 plays a role in output short-circuit protection; resistor R8 and thermistor RNTCThe series connection plays a role in current limiting, and the thermistor RNTCThe overcurrent and overtemperature protection function is realized; the resistor R7 is a feedback resistor, and inputs a feedback signal to the gate G of the MOS transistor Q2 to continuously control the conduction of the MOS transistor Q2.
The types of the devices in the high-side switch circuit are selected as follows:
the MOS tube Q3 is a power type P channel MOSFET, and can be one or a plurality of parallel-connected; the MOS tube Q2 is a small-signal N-channel MOSFET; the resistance value of the resistor R5 is 47K omega; resistance RQ3The resistance value of (1) is 10K omega; the resistance value of the resistor R7 is 1K omega; the resistance value of the resistor R8 is 30K omega; the resistance value of the resistor Rin is 47K omega; the resistance value of the resistor R2 is 1K omega; the resistance value of the resistor R3 is 10K omega; the resistance value of the resistor R4 is 81K omega; pulse for turning ON signal and turning OFF signalThe impulse size is about 5V, and the pulse width depends on the specific application; the on-state voltage of the MOS transistor Q2 is about 3V.
The main idea of the high-side switch circuit is that based on the problem of poor protection reliability in the prior art, the over-current/over-temperature protection function and the output short-circuit protection function of the high-side switch circuit are added on the basis of the prior art, and because the over-current/over-temperature phenomenon occurs, the general design idea of the over-current/over-temperature protection function is to detect the temperature, the electronic element commonly used for detecting the temperature at present is a negative temperature coefficient resistor, and the working principle of the negative temperature coefficient resistor is as follows: based on the principle that the higher the temperature is, the lower the resistance is, in order to protect the output of the power supply to be cut off at the time of overcurrent/overtemperature, the MOS transistor Q3 needs to be controlled to be cut off, namely the MOS transistor Q2 is cut off, and the voltage at the control end of the MOS transistor Q3 is pulled up. In order to realize the over-current/over-temperature protection working process, a designer generally uses the thermistor RNTCGrounding enables the feedback signal of the resistor R7 to be reduced so as to ensure that the MOS transistor Q2 is disconnected when overcurrent/overtemperature occurs, however, in the actual test process, the phenomenon that the MOS transistor Q2 cannot be conducted when the ON signal is turned ON is found. Through analysis, the thermistor R is foundNTCThe other end of the resistor is grounded, and then a resistor Rin, a resistor R7 and a thermistor R are connectedNTCThe series connection is carried out to divide the voltage of 5V of the ON signal, the voltage of the gate G of the MOS transistor Q2 cannot reach the breakover voltage of 3V due to the large resistance of the resistor Rin (the resistance of the resistor Rin is large to prevent the feedback current from influencing the signal end, so the resistance of the resistor Rin cannot be reduced), and the breakover control of the MOS transistor Q3 cannot be realized, therefore, the thermistor R is connected in series to divide the voltage of 5V of the ON signal, and the invention divides the voltage of the gate G of the MOS transistor Q2 into the large voltage and the large voltageNTCThe other end of the first resistor is connected to the drain D of the MOS transistor Q2, which avoids the above situation.
In order to realize the timing control of the high-side switch shown in fig. 2, the invention performs the design process shown in fig. 3:
1) designing the on-resistance R of the MOS transistor Q3 according to the working currentQ3ds_on(ii) a On-resistance R of P-channel MOS tube Q3Q3ds_onThe calculation formula is as follows:
wherein: rQ3ds_onIs the on-resistance of the MOS transistor Q3; t isj_MOSJunction temperature of the MOS transistor Q3; t isambIs ambient temperature; i isloadIs the load current of the application; rthja_MOSIs the thermal resistance of the MOS transistor Q3.
The on-resistance R as derived from this formulaQ3ds_onIf the value is too small, no P-channel MOS tube meeting the requirement exists, a mode of connecting a plurality of P-channel MOS tubes in parallel can be adopted to achieve the on-resistance R required by the working currentQ3ds_on。
2) Designing the delay opening time t of the high-side switch circuit according to the application requirementon_delayI.e. the delayed turn-on time t of the MOS transistor Q3delay_Q3；tdelay_Q3The calculation formula is as follows:
CQ2＝CQ2_gate+Cin；
wherein: t is tdelay_Q3The delayed turn-on time of the MOS transistor Q3 is set; vQ2_ThIs the threshold voltage of the MOS transistor Q2; vin_ONIs a control voltage; rinIs the resistance value of the input resistor (i.e., the resistance value of the resistor Rin); cQ2The input total capacitance of the MOS transistor Q2; cQ2_gateThe gate capacitance of the MOS transistor Q2; cinThe capacitance value of the input capacitance (i.e., the capacitance value of the capacitor Cin).
3) Designing the rising edge time t of the output voltage when the high-side switch circuit is switched on according to the application requirementriseThat is, the rise time t of the output voltage of the MOS transistor Q3rise_Q3；trise_Q3The calculation formula is as follows:
wherein: t is trise_Q3Is output of MOS transistor Q3The rise time of the voltage; vQ3_ThIs the threshold voltage of the MOS transistor Q3; vbatIs the supply voltage; rQ3The gate input resistance of the MOS transistor Q3; cQ3Is the input capacitance of the MOS transistor Q3.
4) Designing the protection current I of the short circuit of the high-side switch circuit to the ground according to the application requirementssc；IscThe calculation formula is as follows:
VD3_Br＞Vout_sc
wherein: i isscA protection current for short-circuiting the high-side switching circuit to ground; rsys_inThe system input impedance; rQ3ds_onIs the on-resistance of the MOS transistor Q3; r issc_outShort-circuit impedance to ground for the high-side switching circuit; vout_scThe output voltage is the output voltage when the high-side switch circuit is short-circuited to the ground; vD3_BrThe breakdown threshold voltage V of the voltage regulator tube D3 is the breakdown threshold voltage of the voltage regulator tube D3D3_BrRequiring an output voltage V higher than that in the case of a short circuit to groundout_sc。
5) Designing the over-current protection current I of the high-side switch circuit according to the application requirementsoc；IocThe calculation formula is as follows:
wherein: i isocThe current value of the overcurrent protection; t is a unit ofj_MOS_maxThe highest allowable junction temperature of the MOS transistor Q3; t isambIs ambient temperature; rQ3ds_onIs the on-resistance of the MOS transistor Q3; rthja_MOSIs the thermal resistance of the MOS transistor Q3.
6) Designing a voltage dividing resistor R8 for overheat protection of the high-side switching circuit according to application requirements; the resistance value of the resistor R8 is calculated as follows:
wherein: t is a unit ofshutIs a set thermal shutdown temperature; delta T is the junction temperature and the resistance R of the MOS transistor Q3NTCThe temperature difference of (a); t isj_MOS_maxThe highest allowable junction temperature of the MOS transistor Q3; rNTC.shutIs a resistance RNTCResistance at turn-off; r isT25Is a resistance RNTCResistance at a temperature of 25 ℃; b isNTCIs a resistance RNTCB value of (2); t is25At a temperature of 25 ℃; r8_ act is the resistance value of the resistor R8 obtained from the thermal shutdown temperature; vD3_BrIs the breakdown threshold voltage of the stabilivolt D3; vQ2_shutThe threshold voltage is turned off for the MOS transistor Q2.
7) Designing the standby current I of the high-side switch circuit according to the application requirementstandby；IstandbyThe calculation formula is as follows:
wherein: i isstandbyIs the standby current of the high-side switch circuit; vD2Breakdown voltage of the voltage regulator tube D2; vD3Breakdown voltage of the voltage regulator tube D3; rQ3The gate input resistance of the MOS transistor Q3; rNTCIs a resistance RNTCThe resistance value of (1); r8_ act is the resistance value of the resistor R8 obtained from the thermal shutdown temperature.
The working process of the high-side switching circuit through the design is as follows:
when the ON signal and the OFF signal are invalid, the triode Q1, the MOS transistor Q2 and the MOS transistor Q3 are all in an OFF state, and at the moment, the resistor R3 pulls down the voltage of the base of the triode Q1, so that the triode Q1 is in an OFF state; the resistor R4 pulls down the voltage of the gate G of the MOS transistor Q2, so that the MOS transistor Q2 is in a turn-off state, the capacitor Cin can improve the anti-interference performance of the MOS transistor Q2, and the high-side switching circuit is kept in a stable state under a strong interference condition; the resistor R5 pulls the gate G of the MOS transistor Q3 high, so that the MOS transistor Q3 is in an off state.
After the ON signal is enabled, the ON signal controls the conduction of the MOS tube Q2 through the resistor Rin, and after the MOS tube Q2 is conducted, the MOS tube Q2 is conducted through the resistor RQ3The voltage of the gate G of the MOS transistor Q3 is pulled down, and the MOS transistor Q3 is conducted; the high-side switch circuit starts to enter a conducting state after a period of time ton_delayAfter that, the output voltage starts to rise for a period of time triseThen, the output voltage reaches the power supply voltage VBAT;
after the output voltage rises, the breakdown voltage of a voltage regulator tube D3 is reached, the voltage regulator tube D3 breaks down, and a resistor R8 and a thermistor R are connectedNTCThe voltage of a voltage division point is a feedback signal, the feedback signal controls the conduction of the MOS tube Q2 through the resistor R7, the high-side switch circuit is further maintained to be in a continuous conduction state, at the moment, the ON signal can be removed, namely, the ON signal is a high-level pulse signal, and the pulse width T is equal to the pulse width of the ON signalonDepending on the particular application.
When the high-side switching circuit is in a conducting state, after an OFF signal is turned OFF and enabled, the OFF signal is divided by a resistor R2 and a resistor R3, a triode Q1 is controlled to be conducted, a feedback signal is forcibly pulled down, an MOS transistor Q2 is immediately turned OFF, and therefore the voltage of a gate G of an MOS transistor Q3 is pulled up by a resistor R5, and the MOS transistor Q3 is immediately turned OFF; after the MOS transistor Q3 is turned OFF, the feedback signal responsible for maintaining the conduction of the MOS transistor Q3 disappears, and at this time, the OFF signal can be removed, that is, the OFF signal itself is also a high-level pulse signal, and the pulse width T is equal to the pulse width ToffDepending on the particular application.
When the high-side switch is in a conducting state, if an output ground short circuit fault occurs, the voltage of an output end (namely the voltage of a drain D of the MOS tube Q3) is pulled down, the output current is sharply increased, and after a period of time toff (sc), the maximum short circuit current value is reached, when the output voltage is lower than the breakdown voltage of the voltage regulator tube D3, the voltage regulator tube D3 is converted into a cut-off state from the breakdown conducting state, a feedback signal disappears, the MOS tube Q2 is cut off due to no control signal, so that the MOS tube Q3 is immediately cut off, and the high-side switch circuit enters a stable cut-off state, namely a protection clamping state, and plays a ground short circuit protection clamping function.
When the high-side switch is in the conducting state, if the output current is too large, the MOS transistor Q3 will generate heat due to the overcurrent, because of the thermistor RNTCIs arranged near the MOS transistor Q3, and the thermistor RNTCIs a negative temperature coefficient resistor (thermistor R)NTCThe resistance value of (a) decreases with increasing temperature), when the temperature of the MOS transistor Q3 reaches the designed turn-off temperature TshutIn the meantime, the feedback signal cannot continuously maintain the on-state control of the MOS transistor Q2, and the MOS transistor Q2 is turned off without a control signal, so that the MOS transistor Q3 is immediately turned off, and the high-side switching circuit enters a stable off state, i.e., an overcurrent and overheat clamping state, and thus an overcurrent and overheat protection clamping function is achieved.
In the above embodiment, the MOS transistor Q3 may be any type of P-channel MOSFET, the voltage and current levels are selected according to the specific application, and the MOS transistor Q3 is one or more P-channel MOSFETs connected in parallel, and may be selectively designed according to the application.
In the above embodiment, the MOS transistor Q2 is a small-signal N-channel MOSFET, and as another embodiment, the MOS transistor Q2 may be replaced by a triode, but the standby current of the circuit may be increased, which is not limited in the present invention.
In the above embodiment, the transistor Q1 is a common transistor, and as another embodiment, the transistor Q1 may also be replaced by an N-channel MOSFET, which is not limited in the present invention.
In the above embodiment, the protection circuit may play a role in protection of overcurrent/overtemperature and output short circuit, and as another embodiment, under the condition that the output is reliable, protection of output short circuit is not required, that is, the voltage regulator tube D3 may not be provided.
The invention adds a protection circuit on the basis of the prior art, mainly realizes the protection of over-current/over-temperature and output short circuit of a high-side switch circuit, and devices which play the roles of current limiting, filtering, voltage stabilizing and the like on each switch tube are arranged for improving the stability of the circuit, so the protection circuit is not a necessary device for realizing the protection of the invention and can not be arranged.
The high-side switch circuit provided by the invention does not need an MCU (microprogrammed control Unit) and a driving chip, simplifies the system design, reduces the overall cost, has low standby current (the standby current can be reduced to milliampere level), an integrated protection function and a clamping function, and improves the reliability of the switch circuit. The switch circuit can support any load type, such as resistance, capacitance and inductance, or supply power for other controllers, can be applied to a power supply system of an automobile, can also be integrated in any distribution box, controller or solid-state relay to replace a high-current relay, or replace a high-side switch chip with higher cost and needing MCU control, or a discrete high-side switch circuit, and has wide application range.
Claims (8)
1. A high-side switching circuit, comprising:
the third switching tube Q3 is used for being connected between a power supply end and an output end in series; the drain electrode of the third switching tube Q3 is used for connecting a power supply end;
the driving circuit of the third switching tube Q3 comprises a second switching tube Q2 and a first switching tube Q1, wherein the collector of the first switching tube Q1 is connected with the control end of the second switching tube Q2; the drain electrode of the second switching tube Q2 is connected with the control end of the third switching tube Q3; the emitter of the first switch tube Q1 and the source of the second switch tube Q2 are grounded;
the ON end is connected with the control end of the second switching tube Q2;
an OFF end connected with the control end of the first switching tube Q1;
the circuit is characterized by further comprising a protection circuit and a self-locking circuit for providing a feedback signal to realize continuous conduction of the second switching tube Q2:
the protection circuit comprises a voltage regulator tube D3, a voltage dividing resistor R8 and a thermistor R with negative temperature coefficientNTCThe cathode of a voltage-stabilizing tube D3 is connected with the output end, the anode of a voltage-stabilizing tube D3 is connected with one end of a divider resistor R8, and the other end of the divider resistor R8 is connected with a thermistor RNTCOne end of (1), thermistor RNTCThe other end of the first switch tube is connected with the drain electrode of the second switch tube Q2; the thermistor RNTCThe temperature of the third switching tube Q3 is acquired;
the self-locking circuit is provided with a resistor R7 for limiting the feedback currentOne end of the resistor R7 is connected with the divider resistor R8 and the thermistor RNTCAnd the other end of the voltage division point is connected with the control end of the second switching tube Q2.
2. The high-side switch circuit as claimed in claim 1, wherein a first voltage-dividing branch is provided between the drain of the second switch transistor Q2 and the power source terminal, and a resistor R5 and a resistor R are connected in series to the first voltage-dividing branchQ3The control end of the third switching tube Q3 is connected with a resistor R5 and a resistor RQ3And at the voltage division point, two ends of the resistor R5 are connected in parallel with a voltage regulator tube D2 for performing overvoltage protection on the third switch tube Q3.
3. The high-side switch circuit according to claim 1, wherein a resistor Rin is disposed between the ON terminal and the control terminal of the second switch transistor Q2, and the resistor Rin performs a current limiting protection function ON the second switch transistor Q2.
4. The high-side switch circuit as claimed in claim 1, wherein a resistor R4 is disposed between the control terminal of the second switch transistor Q2 and ground, and is used for providing a stable level for the control terminal of the second switch transistor Q2.
5. The high-side switch circuit according to claim 1, wherein a capacitor Cin is disposed between the control terminal of the second switch transistor Q2 and ground for filtering the input signal.
6. The high-side switching circuit according to claim 1, wherein a voltage regulator D1 is arranged between the control end of the second switching tube Q2 and the ground, the cathode of the voltage regulator D1 is connected to the control end of the second switching tube Q2, and the anode of the voltage regulator D1 is grounded, so as to protect the control end of the second switching tube Q2 and ensure that no overvoltage is generated.
7. The high-side switch circuit according to claim 1, wherein a second voltage-dividing branch is connected in series between the OFF terminal and the ground, and a voltage-dividing point of the second voltage-dividing branch is connected to a control terminal of the first switch tube Q1.
8. The high-side switch circuit according to claim 1, wherein the third switch transistor Q3 is one or more parallel P-type MOS transistors.
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| CN202010767684.3A CN111786356B (en) | 2020-08-03 | 2020-08-03 | High-side switch circuit |
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| CN202010767684.3A CN111786356B (en) | 2020-08-03 | 2020-08-03 | High-side switch circuit |
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| CN201750125U (en) * | 2010-06-24 | 2011-02-16 | 上海航天汽车机电股份有限公司 | Short circuit self-locking protection circuit |
| TWI671982B (en) * | 2017-10-03 | 2019-09-11 | 偉詮電子股份有限公司 | Power converter, power controller, and control methods capable of providing multiple protections |
| CN209389698U (en) * | 2019-03-18 | 2019-09-13 | 上海华测导航技术股份有限公司 | A kind of over-voltage and under-voltage protecting circuit |
| CN210041316U (en) * | 2019-06-26 | 2020-02-07 | 潍坊歌尔电子有限公司 | Over-temperature protection circuit |
| CN111049509A (en) * | 2019-11-27 | 2020-04-21 | 山东航天电子技术研究所 | Self-locking switch circuit and power module |
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