CN212278208U

CN212278208U - High-side switch circuit suitable for wide voltage and wide temperature and capable of preventing error protection

Info

Publication number: CN212278208U
Application number: CN202020936421.6U
Authority: CN
Inventors: 阳彩; 阚予平; 纪智勇
Original assignee: Keboda Technology Co ltd
Current assignee: Keboda Technology Co ltd
Priority date: 2020-05-28
Filing date: 2020-05-28
Publication date: 2021-01-01
Anticipated expiration: 2030-05-28

Abstract

A high-side switch circuit suitable for wide voltage and wide temperature and capable of preventing error protection comprises a first switch element, a current sampling circuit, a bypass capacitor, a starting circuit, an overcurrent protection circuit, a protection state latch circuit and a first switch element control circuit. The first switch element is respectively connected with the voltage input end and the voltage output end, and the current sampling circuit is connected between the voltage input end and the first switch element in series. The bypass capacitor is connected in parallel with the current sampling circuit. The input end of the starting circuit is connected with the output end of the current sampling circuit, and the output end of the starting circuit is connected with the control end of the overcurrent protection circuit. The protection state latch circuit is respectively connected with the voltage input end and the overcurrent protection circuit; the first switch element control circuit is respectively connected with the control signal input end of the high-side switch circuit and the output end of the overcurrent protection circuit, and the output end of the first switch element control circuit is connected with the first switch element Q1. The utility model discloses start impulse current and the error protection that the impulse current that external disturbance causes brought when can prevent to connect capacitive load.

Description

High-side switch circuit suitable for wide voltage and wide temperature and capable of preventing error protection

Technical Field

The utility model relates to a protection circuit technique especially relates to high limit switch circuit.

Background

At present, the intelligent high-side switch circuit with the current protection function has the following defects: 1. when the output of the high-side switch circuit is connected with the capacitive load and the high-side switch circuit is started, the impact Current (Inrush Current) can cause the malfunction of the protection circuit; 2. the requirements of wide voltage and wide temperature working environment cannot be met; 3. when short circuit occurs during operation, the maximum current is high and the device is likely to be damaged before the overcurrent protection circuit acts.

Disclosure of Invention

The utility model aims to solve the technical problem that a high limit switch circuit is provided, the mistake protection that the impulse current that start impulse current and external disturbance cause brought in the course of the work when it can prevent to connect capacitive load brought.

The utility model aims to solve another technical problem and provide a high limit switch circuit, it can satisfy wide voltage, wide temperature operational environment's requirement, when the short circuit takes place in the course of the work, before overcurrent protection circuit action, can restrict output maximum current.

The embodiment of the utility model provides a can prevent high limit switch circuit of mistake protection, including voltage input end, voltage output end, control signal input end, first switch element Q1 and current sampling circuit; a first terminal and a second terminal of the first switching element Q1 are connected to the voltage input terminal and the voltage output terminal, respectively, and the current sampling circuit is connected in series between the voltage input terminal and the first terminal of the first switching element Q1 or between the second terminal of the first switching element Q1 and the voltage output terminal; the current sampling circuit is used for sampling the current flowing through the first switching element Q1 and outputting a voltage signal corresponding to the current; the high-side switch circuit also comprises a bypass capacitor C1, a starting circuit, an overcurrent protection circuit, a protection state latch circuit and a first switch element control circuit; the bypass capacitor C1 is connected in parallel with the current sampling circuit; the input end of the starting circuit is connected with the output end of the current sampling circuit, and the output end of the starting circuit is connected with the control end of the overcurrent protection circuit, so that the overcurrent protection circuit is started when the current flowing through the first switching element Q1 exceeds a preset overcurrent threshold; the overcurrent protection circuit is used for outputting a working signal to the protection state latch circuit when the overcurrent protection circuit is started and outputting a turn-off signal to the first switching element control circuit; the protection state latch circuit is respectively connected with the voltage input end of the high-side switch circuit and the overcurrent protection circuit and is used for latching a turn-off signal output by the overcurrent protection circuit when receiving a working signal; the control input end of the first switch element control circuit is respectively connected with the control signal input end of the high-side switch circuit and the output end of the overcurrent protection circuit, the output end of the first switch element control circuit is connected with the control input end of the first switch element Q1, the first switch element control circuit controls the action of the first switch element Q1 according to the control signal input from the control signal input end of the high-side switch circuit when not receiving the turn-off signal, and turns off the first switch element Q1 and enables the first switch element Q1 to maintain the turn-off state when receiving the turn-off signal.

Further, the first switching element Q1 is a transistor.

Further, the starting circuit comprises a third switching element Q3, a first end and a control end of the third switching element Q3 are respectively connected with two ends of the sampling resistor R1, and a second end of the third switching element Q3 is connected with the control end of the overcurrent protection circuit; the third switching element Q3 is a MOS transistor.

The embodiment of the utility model also provides a high side switch circuit suitable for wide voltage operational environment, including voltage input end, voltage output end, control signal input end, first switch element Q1 and current sampling circuit; a first terminal and a second terminal of the first switching element Q1 are connected to a voltage input terminal and the voltage output terminal, respectively, and the current sampling circuit is connected in series between the voltage input terminal and the first terminal of the first switching element Q1 or between the second terminal of the first switching element Q1 and the voltage output terminal; the current sampling circuit is used for sampling the current flowing through the first switching element Q1 and outputting a voltage signal corresponding to the current, and is characterized in that the first switching element Q1 is a triode; the high-side switch circuit also comprises a starting circuit, an overcurrent protection circuit, a protection state latch circuit and a first switch element control circuit; the input end of the starting circuit is connected with the output end of the current sampling circuit, the output end of the starting circuit is connected with the control end of the overcurrent protection circuit, and the overcurrent protection circuit is started when the current flowing through the first switching element Q1 exceeds a preset overcurrent threshold; the overcurrent protection circuit is used for outputting a working signal to the protection state latch circuit when the overcurrent protection circuit is started and outputting a turn-off signal to the first switching element control circuit; the protection state latch circuit is respectively connected with the voltage input end of the high-side switch circuit and the overcurrent protection circuit and is used for latching a turn-off signal output by the overcurrent protection circuit when receiving a working signal; the control input end of the first switch element control circuit is respectively connected with the control signal input end of the high-side switch circuit and the output end of the overcurrent protection circuit, the output end of the first switch element control circuit is connected with the control input end of the first switch element Q1, the first switch element control circuit controls the action of the first switch element Q1 according to the control signal input from the control signal input end of the high-side switch circuit when not receiving the turn-off signal, and turns off the first switch element Q1 and enables the first switch element Q1 to maintain the turn-off state when receiving the turn-off signal.

The embodiment of the utility model also provides a high side switch circuit suitable for wide temperature working environment, including voltage input end, voltage output end, control signal input end, first switch element Q1 and current sampling circuit; the first end and the second end of the first switching element Q1 are respectively connected with a voltage input end and a voltage output end, and the current sampling circuit is connected between the voltage input end and the first end of the first switching element Q1 in series or between the second end of the first switching element Q1 and the voltage output end in series; the current sampling circuit is used for sampling the current flowing through the first switching element Q1 and outputting a voltage signal corresponding to the current, and is characterized in that the high-side switching circuit further comprises a starting circuit, an overcurrent protection circuit, a protection state latch circuit and a first switching element control circuit; the starting circuit comprises a third switching element Q3, a first end and a control end of the third switching element Q3 are connected with an output end of the current sampling circuit, a second end of the third switching element Q3 is connected with a control end of the overcurrent protection circuit, and the starting circuit is used for starting the overcurrent protection circuit when the current flowing through the first switching element Q1 exceeds a preset overcurrent threshold; the third switching element Q3 is a MOS transistor; the overcurrent protection circuit is used for outputting a working signal to the protection state latch circuit when the overcurrent protection circuit is started and outputting a turn-off signal to the first switching element control circuit; the protection state latch circuit is respectively connected with the voltage input end of the high-side switch circuit and the overcurrent protection circuit and is used for latching a turn-off signal output by the overcurrent protection circuit when receiving a working signal; the control input end of the first switch element control circuit is respectively connected with the control signal input end of the high-side switch circuit and the output end of the overcurrent protection circuit, the output end of the first switch element control circuit is connected with the control input end of the first switch element Q1, the first switch element control circuit controls the action of the first switch element Q1 according to the control signal input from the control signal input end of the high-side switch circuit when not receiving the turn-off signal, and turns off the first switch element Q1 and enables the first switch element Q1 to maintain the turn-off state when receiving the turn-off signal.

The utility model discloses at least, following technological effect has:

1. when the high-side switch circuit of the embodiment of the utility model is connected with the capacitive load, the impact current generated at the moment when the first switch element Q1 is opened can be bypassed by the bypass capacitor; in addition, in the working process, the impact current caused by external interference can be bypassed by the bypass capacitor; the overcurrent protection circuit can be prevented from being triggered by impact current;

2. the first switch element Q1 of the high-side switch circuit of the embodiment of the utility model is composed of the triode, the current of the triode can be limited by the base current, if a short circuit occurs in the working process, the maximum current can be limited by the triode before the overcurrent protection circuit acts, the device is prevented from being damaged, and the high-side switch circuit can adapt to the wide voltage range;

3. the third switching element Q3 is a MOS tube, compared with a triode, the temperature of the emitter base bias voltage Vbe of the triode is very large and is close to 0 at high temperature, the current passing through the current sampling circuit is slightly large, the overcurrent protection circuit can perform protection action, and the first switching element Q1 cannot be started, so that the high-side switching circuit can only be unloaded and cannot carry load; and the gate-source voltage threshold Vgs (th) of the MOS tube is far larger than Vbe, and is relatively little influenced by temperature, so that the MOS tube can adapt to wide temperature application environments.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

Fig. 1 shows a schematic circuit diagram of a high-side switching circuit according to a first embodiment of the present invention.

Fig. 2 shows a circuit schematic of a high-side switching circuit according to a second embodiment of the present invention.

Fig. 3 shows a circuit schematic of a high-side switching circuit according to a third embodiment of the present invention.

Fig. 4 shows a circuit schematic of a high-side switching circuit according to a fourth embodiment of the present invention.

Detailed Description

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

Fig. 1 shows a schematic circuit diagram of a high-side switching circuit according to a first embodiment of the present invention. Please refer to fig. 1. According to the utility model discloses a can prevent high limit switch circuit of mistake protection of first embodiment, including voltage input end In, voltage Output end Output, control signal input end s, first switching element Q1, current sampling circuit 1, starting circuit 2, overcurrent protection circuit 3, protection state latch circuit 4, first switching element control circuit 5, reset circuit 6 and bypass electric capacity C1.

The first terminal and the second terminal of the first switching element Q1 are connected to a voltage input terminal In and a voltage Output terminal Output, respectively, the current sampling circuit 1 is connected In series between the voltage input terminal In and the first terminal of the first switching element Q1, and the current sampling circuit 1 is configured to sample a current flowing through the first switching element Q1 and Output a voltage signal corresponding to the current flowing through the first switching element Q1. The bypass capacitor C1 is connected in parallel with the current sampling circuit 1.

The input end of the starting circuit 2 is connected with the output end of the current sampling circuit 1, the output end of the starting circuit 2 is connected with the first control end of the overcurrent protection circuit 3, and the starting circuit 2 starts the overcurrent protection circuit 3 when the current flowing through the first switching element Q1 exceeds a preset overcurrent threshold.

The overcurrent protection circuit 3 is configured to output a working signal to the protection state latch circuit 4 at the time of start-up, and output a shutdown signal to the first switching element control circuit 5.

The protection state latch circuit 4 is respectively connected with the voltage input end In of the high-side switch circuit and the overcurrent protection circuit 3, and is used for latching a turn-off signal output by the overcurrent protection circuit 3 when receiving a working signal.

The control input terminal of the first switching element control circuit 5 is connected to the control signal input terminal s of the high-side switching circuit and the output terminal of the overcurrent protection circuit 3, respectively, the output terminal of the first switching element control circuit 5 is connected to the control input terminal of the first switching element Q1, the first switching element control circuit 5 controls the operation of the first switching element Q1 according to the control signal input from the control signal input terminal s of the high-side switching circuit when the turn-off signal is not received, and turns off the first switching element Q1 and maintains the turn-off state of the first switching element Q1 when the turn-off signal is received.

The reset signal input end r of the reset circuit 6 is used for receiving an externally input reset signal, the power input end of the reset circuit 6 is connected with the voltage input end In of the high-side switch circuit, the output end of the reset circuit 6 is respectively connected with the control end of the overcurrent protection circuit 3 and the protection state latch circuit 4, and the reset circuit 6 is used for releasing the latch of the shutdown signal output by the overcurrent protection circuit 3 by the protection state latch circuit 4, namely resetting the latched protection state.

The first switching element control circuit 5 comprises a second switching element Q2, a base current limiting resistor R9 and a pull-down discharging resistor R12, wherein a control end of the second switching element Q2 is respectively connected with a control signal input end s of the high-side switching circuit and an output end of the overcurrent protection circuit 3, a first end of the second switching element Q2 is connected with a control input end of the first switching element Q1 through a base current limiting resistor R9, and a second end of the second switching element Q2 is grounded; one end of the pull-down discharge resistor R12 is connected to the control terminal of the second switching element, and the other end of the pull-down discharge resistor R12 is connected to the second terminal of the second switching control element Q2 and ground, respectively.

The overcurrent protection circuit 3 includes a fifth switching element Q5 and a diode D2; the protection state latch circuit 4 includes a fourth switching element Q4. A first terminal of the fourth switching element Q4 is connected to the voltage input terminal In of the high-side switching circuit. A control terminal of the fifth switching element Q5 is connected to the output terminal of the start circuit 2 and the second terminal of the fourth switching element Q4, respectively, a first terminal of the fifth switching element Q5 is connected to the control terminal of the fourth switching element Q4 and the cathode of the diode D2, respectively, a second terminal of the fifth switching element Q5 is grounded, and an anode of the diode D2 is connected to the control terminal of the second switching element Q2. When the fifth switching element Q5 is turned on, the fourth switching element Q4 is turned on, the diode D2 is forward biased, the second switching element Q2 is turned off when the diode D2 is forward biased, the first switching element Q1 is further turned off, and when the fourth switching element Q4 is turned on, the control terminal of the fifth switching element Q5 is connected to the voltage input terminal In of the high-side switching circuit, so that the output signal of the fifth switching element Q5 is kept unchanged, and the second switching element Q2 and the first switching element Q1 are further kept In an off state.

The reset circuit 6 includes a sixth switching element Q6 and a seventh switching element Q7. A control terminal of the seventh switching element Q7 is configured to receive an externally input reset signal, a first terminal of the seventh switching element Q7 is connected to the control terminal of the sixth switching element Q6 and the voltage input terminal In of the high-side switching circuit, and a second terminal of the seventh switching element Q7 is grounded. A first terminal of the sixth switching element Q6 is connected to the second terminal of the fourth switching element Q4 and the control terminal of the fifth switching element Q5, respectively, and a second terminal of the sixth switching element Q6 is grounded. The seventh switching element Q7 turns off when receiving an externally input reset signal, turns on the sixth switching element Q6, turns off the fifth switching element Q5 when the sixth switching element Q6 is on, turns off the fourth switching element Q4 when the fifth switching element Q5 is off, and reversely biases the diode D2.

In the present embodiment, the current sampling circuit 1 includes a sampling resistor R1, a sampling resistor R1 is connected In series between the voltage input terminal In and the first terminal of the first switching element Q1, and a bypass capacitor C1 is connected In parallel with the sampling resistor R1. When the high-side switch circuit is connected with the capacitive load, the impact current generated at the moment when the first switch element Q1 is turned on can be bypassed by the bypass capacitor C1, so that the overcurrent protection circuit 3 is prevented from being triggered by the impact current by mistake. In other embodiments, the sampling resistor R1 is connected in series between the second terminal of the first switching element Q1 and the voltage Output terminal Output.

The start circuit 2 includes a third switching element Q3, a first terminal and a control terminal of the third switching element Q3 are connected to both terminals of a sampling resistor R1, respectively, and a second terminal of the third switching element Q3 is connected to a control terminal of a fifth switching element Q5.

In this embodiment, the first switching element Q1 is a PNP transistor Q1, and the base, emitter, and collector of the PNP transistor Q1 form the control terminal, the first terminal, and the second terminal of the first switching element Q1, respectively. The second switching element Q2 is an NMOS transistor Q2, and the gate, the drain and the source of the NMOS transistor Q2 respectively form a control terminal, a first terminal and a second terminal of the second switching element Q2. The third switching element Q3 is a PMOS transistor Q3, and the gate, source and drain of the PMOS transistor Q3 respectively constitute the control terminal, the first terminal and the second terminal of the third switching element Q3. The fourth switching element Q4 is a PNP triode, and the base, emitter, and collector of the PNP triode Q4 form the control terminal, the first terminal, and the second terminal of the fourth switching element Q4, respectively. The fifth switching element Q5 is an NPN transistor, and a base, a collector, and an emitter of the NPN transistor Q5 constitute a control terminal, a first terminal, and a second terminal of the fifth switching element Q5, respectively. The sixth switching element Q6 is an NPN transistor, and a base, a collector, and an emitter of the NPN transistor Q6 respectively form a control terminal, a first terminal, and a second terminal of the sixth switching element Q6. The seventh switching element Q7 is an NPN transistor, and a base, a collector, and an emitter of the NPN transistor Q7 respectively constitute a control terminal, a first terminal, and a second terminal of the seventh switching element Q7.

The collector current of the PNP transistor Q1 can be limited by the base current, and the base current limiting resistor R9 functions to limit the base current of the NPN transistor Q1. If a short circuit occurs in the working process, before the overcurrent protection circuit 3 acts, the maximum current of the high-side switch circuit can be limited by the PNP triode Q1, so that the device is prevented from being damaged, and the high-side switch circuit can adapt to a wide voltage range. Compared with a triode, the third switching element Q3 adopts an MOS tube, the emitter base bias voltage Vbe of the triode has very large temperature drift and is close to 0 at high temperature, so that the first switching element Q1 cannot be started, and the gate-source voltage threshold Vgs (th) of the MOS tube is far larger than the Vbe and is relatively slightly influenced by temperature, so that the MOS tube can adapt to wide temperature application environment.

Further, the high-side switch circuit of this embodiment includes a diode D1, an anode of the diode D1 is connected to a collector of the PNP transistor Q1, a cathode of the diode D1 is connected to an emitter of the PNP transistor Q1, and the diode D1 protects the PNP transistor Q1.

Further, the first switching element control circuit 5 includes a base discharge resistor R8 and a control resistor R11. One end of the base discharge resistor R8 is connected to a first end of the first switching element Q1, and the other end of the base discharge resistor R8 is connected to a control end of the first switching element Q1 and one end of the base current limiting resistor R9, respectively. One end of the control resistor R11 is connected to the output end of the overcurrent protection circuit 3 and the control end of the second switching element Q2, respectively, and the other end of the control resistor R11 is connected to the control signal input end s of the high-side switching circuit.

Further, the protection state latch circuit 4 includes a current limiting resistor R2 and a pull-up resistor R3, and the overcurrent protection circuit 3 includes a pull-up resistor R4 and a resistor R15. One end of a current limiting resistor R2 and one end of a pull-up resistor R3 are respectively connected with a voltage input end In of the high-side switching circuit, the other end of the current limiting resistor R2 is connected with an emitting electrode of a PNP triode Q4, the other end of the pull-up resistor R3 is connected with a base electrode of a PNP triode Q4, and a collector electrode of the PNP triode Q4 is connected with a base electrode of an NPN triode Q5. One end of a pull-up resistor R4 is connected with the output end of the starting circuit 2 (namely the drain electrode of the PMOS tube Q3), the other end of the pull-up resistor R4 is connected with the common joint of the collector of the PNP triode Q4, the base of the NPN triode Q5 and one end of the resistor R15, and the other end of the resistor R15 is grounded. The resistor R15 can bypass part of leakage current at high temperature, so that most of current does not flow through the base of the NPN triode Q5, the error action of the NPN triode Q5 is prevented, and the high-side switching circuit of the embodiment can be more suitable for wide temperature application environment. The collector of the NPN transistor Q5 is connected to the base of the PNP transistor Q4 and the cathode of the diode D2, respectively, and the anode of the diode D2 is connected to the control terminal of the second switching element Q2. The anode of the diode D2 constitutes the output of the overcurrent protection circuit.

Further, the reset circuit 6 includes a pull-up resistor R5, a current limiting resistor R6, and a pull-down discharge resistor R7. One end of a pull-up resistor R5 is connected with a voltage input end In of the high-side switch circuit, and the other end of the pull-up resistor R5 is respectively connected with a base electrode of an NPN triode Q6 and a collector electrode of an NPN triode Q7. One end of the current limiting resistor R6 is used as a reset signal input end R of the reset circuit 6 and is used for receiving an externally input reset signal, the other end of the current limiting resistor R6 is respectively connected with the base of the NPN triode Q7 and one end of the pull-down discharge resistor R7, and the other end of the pull-down discharge resistor R7 is grounded.

The Enable signal input to the control signal input terminal s of the high-side switch circuit corresponds to an Enable signal for enabling the high-side switch circuit to operate when the Enable signal is at a high level, and the Reset signal input to the control terminal r of the Reset circuit corresponds to a Reset signal when the Reset signal is at a low level. According to the utility model discloses high limit switch circuit has four kinds of operating modes:

working condition 1:

the Enable signal is high and no over-current occurs. At this time, the voltage drop across the sampling resistor R1 is smaller than the gate-source voltage threshold Vgs (th) of the PMOS transistor Q3, and the PMOS transistor Q3 is turned off; the base electrode of the NPN triode Q5 floats, and the NPN triode Q5 is cut off; the base electrode of the PNP triode Q4 is pulled up to Vin by a pull-up resistor R3 and is cut off, and Vin is the input voltage of the voltage input end In; the cathode of the diode D2 is pulled up to Vin by a pull-up resistor R3, the diode D2 is reversely biased to be cut off, the grid of the NMOS tube Q2 is controlled to be high by an Enable signal, the NMOS tube Q2 is conducted, the PNP triode Q1 is further controlled to be conducted, and the Enable signal indirectly controls the conduction and the cut-off of the PNP triode Q1 by controlling the conduction and the cut-off of the NMOS tube Q2. At this time, if the Reset signal is at a high level, the NPN transistor Q7 is turned on, the base of the NPN transistor Q6 is pulled to ground, and the NPN transistor Q6 is turned off; if the Reset signal is low, NPN transistor Q7 turns off, the base of NPN transistor Q6 is pulled up to Vin by pull-up resistor R5, and NPN transistor Q6 turns on.

In the operating condition 1, a current input from the voltage input terminal In of the high-side switching circuit flows to the voltage Output terminal Output through the first switching element Q1, and is Output to the load R10.

Working condition 2:

the Enable signal is low. At this time, the gate input signal of the NMOS transistor Q2 is low, the NMOS transistor Q2 is turned off, and the PNP transistor Q1 is also turned off.

Working condition 3:

when the Enable signal is high, an overcurrent occurs.

When the Reset signal is high, NPN transistor Q7 turns on, and NPN transistor Q6 turns off. The base of NPN transistor Q5 is not pulled down to ground by NPN transistor Q6, and the base level of NPN transistor Q5 is controlled by PNP transistor Q3 and PNP transistor Q4.

Due to overcurrent (namely, the current flowing through the first switching element Q1 exceeds a predetermined overcurrent threshold which is related to the resistance of the sampling resistor R1), the voltage across the sampling resistor R1 exceeds the gate-source voltage threshold vgs (th) of the PMOS transistor Q3, the PMOS transistor Q3 is turned on, the voltage at the base of the NPN transistor Q5 is pulled up by the pull-up resistor R4, the NPN transistor Q5 is turned on (namely, the overcurrent protection circuit is started), so that the diode D2 is forward biased, the diode D2 is forward biased, the gate of the NMOS transistor Q2 is pulled to the ground, the NMOS transistor Q2 is turned off, and the PNP transistor Q1 is turned off.

After the base electrode of the PNP triode Q4 is pulled to the ground by the NPN triode Q5, the PNP triode Q4 is conducted, the base electrode of the NPN triode Q5 is pulled to Vin by the current-limiting resistor R2 through the PNP triode Q4, the conducting state of the NPN triode Q5 is latched, and therefore the latching of the overcurrent protection state of the PNP triode Q1 is achieved.

Working condition 4:

and when overcurrent protection occurs, the Reset signal is set to be low, and the Reset signal after the Reset signal is set to be low forms a Reset signal to Reset the overcurrent protection state.

When the Reset signal is set to be low, the NPN triode Q7 is turned off, the NPN triode Q6 is turned on, the base level of the NPN triode Q5 is pulled low, and the NPN triode Q6 is turned off; the potential of the base electrode of the PNP triode Q4 rises, the PNP triode Q4 is turned off, and the diode D2 is reversely biased.

After the overcurrent protection state is reset, if the Enable signal is at a high level, the NMOS transistor Q2 is turned on, and the PNP triode Q1 is also turned on.

Fig. 2 shows a circuit schematic of a high-side switching circuit according to a second embodiment of the present invention. The second embodiment is mainly different from the first embodiment in that, in the second embodiment, the first switching element control circuit 5 includes a diode D3, the anode of the diode D3 is connected to the other end of the pull-down discharge resistor R12 and the second end of the second switching control element Q2, respectively, and the cathode of the diode D3 is grounded. The grid-source voltage threshold Vgs (th) of the small-signal MOS tube is lower, and the grid-source voltage threshold Vgs (th) of the small-signal MOS tube is lower at high temperature. By adding the diode D3, the forward conduction voltage drop of the diode D2 can be counteracted, and the source potential of the NMOS transistor Q2 is raised, so that when the protection is turned off, the gate-source voltage threshold Vgs (th) of the NMOS transistor Q2 is lower, and the MOS transistor is turned off reliably.

Fig. 3 shows a circuit schematic of a high-side switching circuit according to a third embodiment of the present invention. The third embodiment is mainly different from the second embodiment in that in the second embodiment, the control signal input terminal s of the high-side switch circuit and the Reset signal input terminal r of the Reset circuit are independent from each other, and the Enable signal and the Reset signal are separately input, whereas in the third embodiment, the Reset signal input terminal of the Reset circuit and the control signal input terminal of the high-side switch circuit are the same signal input terminal, the low-level signal input from the signal input terminal is the Reset signal Reset for releasing the latch of the protection state, the high-level signal input from the signal input terminal is the Enable signal Enable for enabling the high-side switch circuit to operate.

Fig. 4 shows a circuit schematic of a high-side switching circuit according to a fourth embodiment of the present invention. The main difference between this fourth embodiment and the second embodiment is that the fourth embodiment removes the reset circuit 6 in the second embodiment.

The utility model discloses high limit switch circuit comprises discrete device, therefore, the carrier wave prepaid electric energy meter is low in cost, the resistance through changing sampling resistance can set up this high limit switch circuit's the threshold value that overflows in a flexible way, in case the electric current that flows through first switch element surpasses this threshold value that overflows, overcurrent protection circuit can turn off first switch element Q1 rapidly, protection state latch circuit can latch protection state simultaneously, current-limiting protection has been realized, owing to can latch protection state, therefore the overcurrent protection function of this embodiment compares more reliable and more stable with prior art. In addition, the latch of the protection state can be released through the reset circuit, and the use is very flexible.

It will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims and their equivalents, the present invention is also intended to include such modifications and variations.

Claims

1. A high-side switch circuit capable of preventing error protection comprises a voltage input end, a voltage output end, a control signal input end, a first switch element Q1 and a current sampling circuit; a first terminal and a second terminal of the first switching element Q1 are connected to the voltage input terminal and the voltage output terminal, respectively, and the current sampling circuit is connected in series between the voltage input terminal and the first terminal of the first switching element Q1 or between the second terminal of the first switching element Q1 and the voltage output terminal; the current sampling circuit is used for sampling the current flowing through the first switching element Q1 and outputting a voltage signal corresponding to the current, and is characterized by further comprising a bypass capacitor C1, a starting circuit, an overcurrent protection circuit, a protection state latch circuit and a first switching element control circuit;

a bypass capacitor C1 is connected in parallel with the current sampling circuit;

the input end of the starting circuit is connected with the output end of the current sampling circuit, and the output end of the starting circuit is connected with the control end of the overcurrent protection circuit, so that the overcurrent protection circuit is started when the current flowing through the first switching element Q1 exceeds a preset overcurrent threshold;

the overcurrent protection circuit is used for outputting a working signal to the protection state latch circuit when the overcurrent protection circuit is started, and outputting a turn-off signal to the first switching element control circuit;

the protection state latch circuit is respectively connected with the voltage input end of the high-side switch circuit and the overcurrent protection circuit and is used for latching a turn-off signal output by the overcurrent protection circuit when receiving the working signal;

the control input end of the first switch element control circuit is respectively connected with the control signal input end of the high-side switch circuit and the output end of the overcurrent protection circuit, the output end of the first switch element control circuit is connected with the control input end of a first switch element Q1, the first switch element control circuit controls the action of a first switch element Q1 according to the control signal input from the control signal input end of the high-side switch circuit when not receiving the turn-off signal, and turns off the first switch element Q1 and enables the first switch element Q1 to maintain the turn-off state when receiving the turn-off signal.

2. The error protection prevention high-side switch circuit according to claim 1, wherein the first switch element Q1 is a triode.

3. The high-side switching circuit capable of preventing error protection according to claim 2, wherein the first switching element control circuit comprises a second switching element Q2, a base current limiting resistor R9 and a pull-down discharging resistor R12, a control terminal of the second switching element Q2 is connected to the control signal input terminal of the high-side switching circuit and the output terminal of the over-current protection circuit, respectively, a first terminal of the second switching element Q2 is connected to the control input terminal of the first switching element Q1 through a base current limiting resistor R9, and a second terminal of the second switching element Q2 is grounded; one end of the pull-down discharge resistor R12 is connected to the control terminal of the second switching element, and the other end of the pull-down discharge resistor R12 is connected to the second terminal of the second switching control element Q2 and ground, respectively.

4. The error protection preventing high-side switch circuit as claimed in claim 3, wherein the first switch element Q1 is a PNP transistor Q1, and the base, emitter and collector of the PNP transistor Q1 constitute the control terminal, the first terminal and the second terminal of the first switch element Q1, respectively; the second switching element Q2 is an NMOS transistor Q2, and the gate, the drain and the source of the NMOS transistor Q2 respectively form a control terminal, a first terminal and a second terminal of the second switching element Q2;

the first switching element control circuit includes a base discharge resistor R8; one end of the base discharge resistor R8 is connected to a first end of the first switching element Q1, and the other end of the base discharge resistor R8 is connected to a control end of the first switching element Q1 and one end of the base current limiting resistor R9, respectively.

5. The high-side switch circuit capable of preventing error protection according to claim 4, wherein the first switch element control circuit comprises a control resistor R11, one end of the control resistor R11 is connected to the output terminal of the over-current protection circuit and the control terminal of the second switch element Q2, and the other end of the control resistor R11 is connected to the control signal input terminal of the high-side switch circuit.

6. The error protection preventing high-side switch circuit according to claim 4, wherein the error protection preventing high-side switch circuit comprises a diode D1, an anode of a diode D1 is connected to a collector of a PNP transistor Q1, and a cathode of a diode D1 is connected to an emitter of a PNP transistor Q1.

7. The high-side switch circuit capable of preventing error protection according to claim 2, wherein the current sampling circuit comprises a sampling resistor R1, and the bypass capacitor C1 is connected in parallel with the sampling resistor R1;

the starting circuit comprises a third switching element Q3, a first end and a control end of a third switching element Q3 are respectively connected with two ends of a sampling resistor R1, and a second end of a third switching element Q3 is connected with the control end of the overcurrent protection circuit; the third switching element Q3 is a MOS transistor.

8. The error protection preventing high-side switch circuit as claimed in claim 7, wherein the third switch element Q3 is a PMOS transistor Q3; the gate, source and drain of the PMOS transistor Q3 constitute a control terminal, a first terminal and a second terminal of the third switching element Q3, respectively.

9. The high-side switch circuit capable of preventing error protection according to any one of claims 3 to 8, wherein the over-current protection circuit comprises a fifth switch element Q5 and a diode D2; the protection state latch circuit comprises a fourth switching element Q4;

a control end of the fifth switching element Q5 is respectively connected with the output end of the starting circuit and a second end of the fourth switching element Q4, a first end of the fifth switching element Q5 is respectively connected with a control end of the fourth switching element Q4 and a cathode of the diode D2, a second end of the fifth switching element Q5 is grounded, and an anode of the diode D2 is connected with a control end of the second switching element Q2;

a first end of a fourth switching element Q4 is connected with a voltage input end of the high-side switching circuit;

when the fifth switching element Q5 is turned on, the fourth switching element Q4 is turned on, the diode D2 is forward biased, the second switching element Q2 is turned off when the diode D2 is forward biased, the first switching element Q1 is further turned off, and when the fourth switching element Q4 is turned on, the control terminal of the fifth switching element Q5 is connected to the voltage input terminal of the high-side switching circuit, so that the output signal of the fifth switching element Q5 is kept unchanged.

10. The high-side switching circuit capable of preventing error protection according to claim 9, wherein the fourth switching element Q4 is a PNP transistor Q4, and the base, emitter and collector of the PNP transistor Q4 respectively form the control terminal, the first terminal and the second terminal of the fourth switching element Q4; the fifth switching element Q5 is an NPN transistor Q5, and a base, a collector, and an emitter of the NPN transistor Q5 respectively constitute a control terminal, a first terminal, and a second terminal of the fifth switching element Q5;

the protection state latch circuit comprises a current limiting resistor R2 and a pull-up resistor R3, and the over-current protection circuit comprises a pull-up resistor R4 and a resistor R15; one end of a current limiting resistor R2 and one end of a pull-up resistor R3 are respectively connected with the voltage input end of the high-side switch circuit, the other end of the current limiting resistor R2 is connected with the emitting electrode of a PNP triode Q4, the other end of the pull-up resistor R3 is connected with the base electrode of a PNP triode Q4, and the collector electrode of the PNP triode Q4 is connected with the base electrode of an NPN triode Q5; one end of a pull-up resistor R4 is connected with the output end of the starting circuit, the other end of the pull-up resistor R4 is connected with a common joint of the collector of the PNP triode Q4, the base of the NPN triode Q5 and one end of a resistor R15, and the other end of the resistor R15 is grounded;

the collector of the NPN transistor Q5 is connected to the base of the PNP transistor Q4 and the cathode of the diode D2, respectively, and the anode of the diode D2 is connected to the control terminal of the second switching element Q2.

11. The high-side switch circuit capable of preventing error protection according to claim 9, wherein the first switch element control circuit comprises a diode D3, an anode of the diode D3 is connected to the other end of the pull-down discharge resistor R12 and the second end of the second switch control element Q2, and a cathode of the diode D3 is grounded.

12. The high-side switch circuit capable of preventing the error protection according to any one of claims 1 to 8, wherein the high-side switch circuit comprises a reset circuit, a reset signal input end of the reset circuit is configured to receive an externally input reset signal, a power input end of the reset circuit is connected to a voltage input end of the high-side switch circuit, an output end of the reset circuit is respectively connected to the control end of the over-current protection circuit and the protection state latch circuit, and the reset circuit is configured to release latching of the protection state latch circuit on the off signal output by the over-current protection circuit.

13. The mis-protection preventive high-side switching circuit as claimed in claim 9, wherein the high-side switching circuit includes a reset circuit including a sixth switching element Q6 and a seventh switching element Q7;

a control terminal of the seventh switching element Q7 is configured to receive an externally input reset signal, a first terminal of the seventh switching element Q7 is connected to the control terminal of the sixth switching element Q6 and the voltage input terminal of the high-side switching circuit, and a second terminal of the seventh switching element Q7 is grounded; a first terminal of the sixth switching element Q6 is connected to the second terminal of the fourth switching element Q4 and the control terminal of the fifth switching element Q5, respectively, and a second terminal of the sixth switching element Q6 is grounded;

the seventh switching element Q7 turns off when receiving an externally input reset signal, turns on the sixth switching element Q6, turns off the fifth switching element Q5 when the sixth switching element Q6 is on, turns off the fourth switching element Q4 when the fifth switching element Q5 is off, and reversely biases the diode D2.

14. The error protection preventing high-side switch circuit as claimed in claim 13, wherein the sixth switch element Q6 is an NPN transistor Q6, and a base, a collector and an emitter of the NPN transistor Q6 respectively constitute a control terminal, a first terminal and a second terminal of the sixth switch element Q6; the seventh switching element Q7 is an NPN transistor Q7, and a base, a collector, and an emitter of the NPN transistor Q7 respectively form a control end, a first end, and a second end of the seventh switching element Q7;

the reset circuit comprises a pull-up resistor R5, a current-limiting resistor R6 and a pull-down discharge resistor R7; one end of a pull-up resistor R5 is connected with the voltage input end of the high-side switch circuit, and the other end of the pull-up resistor R5 is respectively connected with the base electrode of an NPN triode Q6 and the collector electrode of an NPN triode Q7; one end of the current-limiting resistor R6 is used for receiving an externally input reset signal, the other end of the current-limiting resistor R6 is respectively connected with the base of the NPN triode Q7 and one end of the pull-down discharge resistor R7, and the other end of the pull-down discharge resistor R7 is grounded.

15. The high-side switch circuit capable of preventing false protection according to claim 12, wherein the reset signal input terminal of the reset circuit and the control signal input terminal of the high-side switch circuit are the same signal input terminal.

16. A high-side switch circuit suitable for a wide-voltage working environment comprises a voltage input end, a voltage output end, a control signal input end, a first switch element Q1 and a current sampling circuit; a first terminal and a second terminal of the first switching element Q1 are connected to the voltage input terminal and the voltage output terminal, respectively, and the current sampling circuit is connected in series between the voltage input terminal and the first terminal of the first switching element Q1 or between the second terminal of the first switching element Q1 and the voltage output terminal; the current sampling circuit is used for sampling the current flowing through the first switching element Q1 and outputting a voltage signal corresponding to the current, and is characterized in that the first switching element Q1 is a triode;

the high-side switch circuit also comprises a starting circuit, an overcurrent protection circuit, a protection state latch circuit and a first switch element control circuit;

17. A high-side switch circuit suitable for wide-temperature working environment comprises a voltage input end, a voltage output end, a control signal input end, a first switch element Q1 and a current sampling circuit; a first terminal and a second terminal of the first switching element Q1 are connected to the voltage input terminal and the voltage output terminal, respectively, and the current sampling circuit is connected in series between the voltage input terminal and the first terminal of the first switching element Q1 or between the second terminal of the first switching element Q1 and the voltage output terminal; the current sampling circuit is used for sampling the current flowing through the first switching element Q1 and outputting a voltage signal corresponding to the current, and is characterized by further comprising a starting circuit, an overcurrent protection circuit, a protection state latch circuit and a first switching element control circuit;

the starting circuit comprises a third switching element Q3, a first end and a control end of a third switching element Q3 are connected with the output end of the current sampling circuit, a second end of a third switching element Q3 is connected with the control end of the overcurrent protection circuit, and the starting circuit is used for starting the overcurrent protection circuit when the current flowing through the first switching element Q1 exceeds a preset overcurrent threshold; the third switching element Q3 is a MOS transistor;