CN108599100B - Switch control circuit and load switch - Google Patents
Switch control circuit and load switch Download PDFInfo
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- CN108599100B CN108599100B CN201810750728.4A CN201810750728A CN108599100B CN 108599100 B CN108599100 B CN 108599100B CN 201810750728 A CN201810750728 A CN 201810750728A CN 108599100 B CN108599100 B CN 108599100B
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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
- H02H3/20—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 voltage
- H02H3/22—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 voltage of short duration, e.g. lightning
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Abstract
The application discloses a switch control circuit and a load switch, wherein the switch control circuit comprises a signal input end, a power supply voltage input end, a first voltage control output end, a first capacitor, a first switching tube, a first current source and a second switching tube; the first capacitor has a high-pass characteristic, namely, the current passing through the capacitor and the voltage change rate of the two ends of the capacitor are in a direct proportional relation, because the capacitor releases or absorbs charges when the voltage of the two ends of the first capacitor changes. The current is coupled to the first end of the first switching tube, namely the control end of the second switching tube through the first capacitor, so that the current passing through the second switching tube becomes large, the voltage of the first voltage control output end is pulled down in a short time, and therefore the main switch in the load switch is controlled, and the purpose of quick turn-off is achieved. The switch control circuit provided by the invention has a simple structure, does not increase more power consumption, and can perform quick response under the condition of quicker voltage change.
Description
Technical Field
The present invention relates to the field of analog circuits, and in particular, to a switch control circuit and a load switch.
Background
In higher-end electronic devices, such as mobile phones, an external power supply charger and other power supply devices are often connected through a load switch, and the input power supply voltage is often changed rapidly and greatly due to instability of a power grid and the external devices, so that an OVP (Over Voltage Protection ) function is usually added to the load switch, that is, when the input voltage exceeds a set voltage value, the load switch is turned off, so that an internal circuit is protected from external high voltage impact.
The closing time Toff of the load switch is an important index, and the faster the closing speed, the smaller the amplitude of the internal voltage rise, the more stable and reliable the system.
In the prior art, a plurality of manufacturers provide improved load switches, and compared with a common load switch, the improved load switch has faster closing speed, but the closing time of the load switch in the prior art is about 50ns-200ns, if an overvoltage event occurs within the range of 50ns, the closing time of the existing load switch is longer, the response is slower, namely the Toff performance of the load switch in the prior art is poor, and the reliability and the safety of a system comprising the load switch are reduced.
In the prior art, the other method capable of improving the response speed of the load switch has the problems of larger power consumption and higher cost.
Disclosure of Invention
In view of this, the present invention provides a switch control circuit and a load switch, so as to solve the problems of low system reliability and safety, high power consumption and high cost caused by the fact that the load switch cannot respond in time when a fast overvoltage event occurs in the prior art.
In order to achieve the above purpose, the present invention provides the following technical solutions:
a switch control circuit for use with a load switch, the switch control circuit comprising:
the power supply comprises a signal input end, a power supply voltage input end, a first voltage control output end, a first capacitor, a first switching tube, a first current source and a second switching tube;
one end of the first capacitor is connected with the signal input end;
the other end of the first capacitor is connected with the output end of the first current source and the first end of the first switching tube;
the input end of the current source is used as a power supply voltage input end of the switch control circuit and is used for receiving the input of power supply voltage;
the control end of the first switching tube is connected with the first end of the first switching tube and the control end of the second switching tube;
the second end of the first switching tube is connected with the second end of the second switching tube and grounded;
the first end of the second switching tube is used as the first voltage control output end and used for controlling the opening and closing of the load switch.
Preferably, the first resistor and the second capacitor are further included;
one end of the first resistor is connected with the second end of the first switch tube, and the other end of the first resistor is connected with the signal input end;
one end of the second capacitor is connected with the second end of the first switch tube, and the other end of the second capacitor is grounded.
The invention also provides a load switch comprising: the switching control circuit, the main switching tube and the driving module;
wherein the switch control circuit is the switch control circuit;
the control end of the main switching tube is connected with the driving module and the first voltage control output end of the switching control circuit, and the driving module is used for providing driving voltage for the main switching tube and switching on or off the main switching tube;
the first end of the main switch tube is connected with the signal input end of the switch control circuit;
the second end of the main switch tube is used as a signal output end of the load switch.
Preferably, the driving module includes: a second current source and a zener diode;
the input end of the second current source is connected with the power supply voltage input end;
the output end of the second current source is connected with the control end of the main switching tube;
the positive electrode of the Zener diode is connected with the second end of the main switching tube;
and the cathode of the zener diode is connected with the control end of the main switching tube.
Preferably, the device further comprises an overpressure treatment module;
the input end of the overvoltage processing module is connected with the signal input end;
the output end of the overvoltage processing module is connected with the control end of the main switching tube;
when the voltage signal change speed of the signal input end is higher than or equal to a first preset threshold value, the switch control circuit controls the main switch tube to be turned off;
and when the voltage signal change speed of the signal input end is lower than the first preset threshold value, the overvoltage processing module controls the main switching tube to be switched off. Preferably, the first preset threshold value ranges from 1V100ns to 10V/100ns, including the end point value.
Preferably, the overpressure treatment module comprises:
the device comprises an input voltage dividing module, a comparison module and a closing module;
the input voltage dividing module includes: the input end, the input end and the grounding end;
the comparison module comprises a first input end, a second input end and an output end;
the closing module comprises a first end, a second end and a control end;
the input end of the input voltage dividing module is connected with the signal input end;
the output end of the input voltage dividing module is connected with the first input end of the comparison module;
the second input end of the comparison module is connected with a reference voltage source and receives the input of a reference voltage;
the output end of the comparison module is connected with the control end of the closing module;
the first end of the closing module is connected with the control end of the main switching tube;
the second end of the closing module is grounded.
Preferably, the closing module comprises a third switching tube;
the first end of the third switching tube is used as the first end of the closing module;
the second end of the third switch tube is used as the second end of the closing module;
and the control end of the third switching tube is used as the control end of the closing module.
Preferably, the input voltage dividing module comprises a second resistor and a third resistor which are sequentially connected in series;
one end of the second resistor, which is far away from the third resistor, is connected with the signal input end;
one end of the third resistor far away from the second resistor is grounded;
the common end of the second resistor and the third resistor is used as the output end of the input voltage dividing module;
the comparison module comprises an operational amplifier;
the non-inverting input end of the operational amplifier is used as a first input end of the comparison module;
the inverting input of the operational amplifier serves as the second input of the comparison module.
Preferably, the first switching tube, the second switching tube and the third switching tube are all NMOS tubes.
As can be seen from the above technical solution, the switch control circuit provided by the present invention includes: the power supply comprises a signal input end, a power supply voltage input end, a first voltage control output end, a first capacitor, a first switching tube, a first current source and a second switching tube; the first capacitor has a high-pass characteristic, namely, the current passing through the capacitor and the voltage change rate of the two ends of the capacitor are in a direct proportional relation, because the capacitor releases or absorbs charges when the voltage of the two ends of the first capacitor changes. The current of the capacitor is coupled to the first end of the first switching tube, namely the control end of the second switching tube through the first capacitor, so that the current passing through the second switching tube becomes large, the voltage of the first voltage control output end is pulled down in a short time, and therefore the main switch in the load switch is controlled, and the purpose of quick turn-off is achieved.
The switch control circuit provided by the invention has a simple circuit structure, does not increase more power consumption, and can perform quick response under the condition of quicker voltage change. That is, in the case where the increase in power consumption is small, the response speed of the switch control circuit is improved.
The invention also provides a load switch which comprises the switch control circuit, a main switch tube and a driving module, wherein the switch control circuit is connected with the control end of the main switch tube and can rapidly control the disconnection or the connection of the main switch tube. Because the switch control circuit has the characteristics of small power consumption and high response speed, the power consumption of the load switch is lower, and the response speed is higher.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required to be used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only embodiments of the present invention, and that other drawings can be obtained according to the provided drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic diagram of an input voltage dividing module of a load switch according to the prior art;
fig. 2 is a schematic diagram of a switch control circuit according to an embodiment of the present invention;
fig. 3 is a schematic diagram of a load switch according to an embodiment of the present invention;
fig. 4 is a schematic diagram of a load switch structure according to an embodiment of the present invention;
fig. 5 is a schematic diagram of another load switch structure according to an embodiment of the present invention;
FIG. 6 is a schematic diagram of a load switch according to an embodiment of the present invention;
fig. 7 is a graph showing response speed comparison in various cases according to an embodiment of the present invention.
Detailed Description
Term interpretation:
vgs: the difference between the voltages of the Gate (Gate) end and the Source end (Source) of the MOS tube;
OVP: overvoltage protection (Over Voltage Protection);
toff: the time between the start of the overvoltage event and the closing of the switch, the closing time;
OPA: operational amplifier (operational amplifier), abbreviated as OP in the present invention;
BGR: bandgap voltage reference a bandgap voltage reference, a module that utilizes semiconductor characteristics to generate a standard voltage. Its composition takes many forms but its function is to generate an accurate voltage. In the present invention, BG is abbreviated, and BGR is also written in the article.
As described in the background section, the load switch in the prior art has a longer turn-off time and a slower response, and even if the load switch in the prior art has a faster response, the power consumption is larger and the cost is higher.
The inventor finds that the reason for the phenomenon is that when overvoltage occurs in a load switch with an OVP function in the prior art, three processes of detection, comparison and closing are adopted, and the processing mode has good processing effect when overvoltage with medium speed (50 ns-200 ns) occurs, but when a rapid overvoltage event (less than 50 ns) occurs at an input end, the response speed of the three functional modules is limited by the detection, comparison and closing, so that the closing time cannot be further reduced, and the output end of the load switch is high-voltage.
In the prior art, a load switch is provided, as shown in fig. 1, fig. 1 is a schematic diagram of an input voltage dividing module of the load switch provided in the prior art; the input voltage dividing module comprises a dividing unit 01, a selection switch unit 02, a first capacitor C01, a second capacitor C02 and a third capacitor C03. The first capacitor and the second capacitor are added as feedforward capacitors to be connected into the input voltage dividing module on the basis of the traditional voltage dividing unit, so that the rising rate of the external input voltage of the output voltage of the input voltage dividing module is improved, and the purpose of reducing the response time of the input voltage dividing module is achieved. Although the structure shown in fig. 1 effectively solves the response time of input voltage detection caused by resistor voltage division, and accelerates the response of the detection module, the response time of the comparison module and the closing module, which is used for coping with a faster input overvoltage event, is still limited by the response time of the comparison module and the closing module, so that when the fast overvoltage event occurs, the closing time of the load switch is longer, and the response is slower.
The inventor finds that the closing module is usually an MOS tube, the response speed of the closing module reaches the current limit due to the limitation of the manufacturing process of the current MOS tube, and the comparing module usually comprises an operational amplifier, so that the response speed of the operational amplifier can be further improved by improving the power consumption of the operational amplifier; but the increase in operational amplifier response speed is typically done at the expense of greater power consumption and higher cost. This causes a problem that the load switch has a high cost and a high power consumption.
Based on this, the present invention provides a switch control circuit applied to a load switch, the switch control circuit comprising:
the power supply comprises a signal input end, a power supply voltage input end, a first voltage control output end, a first capacitor, a first switching tube, a first current source and a second switching tube;
one end of the first capacitor is connected with the signal input end;
the other end of the first capacitor is connected with the output end of the first current source and the first end of the first switching tube;
the input end of the current source is used as a power supply voltage input end of the switch control circuit and is used for receiving the input of power supply voltage;
the control end of the first switching tube is connected with the first end of the first switching tube and the control end of the second switching tube;
the second end of the first switching tube is connected with the second end of the second switching tube and grounded;
the first end of the second switching tube is used as the first voltage control output end and used for controlling the opening and closing of the load switch.
The switch control circuit provided by the invention comprises: the power supply comprises a signal input end, a power supply voltage input end, a first voltage control output end, a first capacitor, a first switching tube, a first current source and a second switching tube; the first capacitor has a high-pass characteristic, namely, the current passing through the capacitor and the voltage change rate of the two ends of the capacitor are in a direct proportional relation, because the capacitor releases or absorbs charges when the voltage of the two ends of the first capacitor changes. The current on the capacitor is coupled to the first end of the first switching tube, namely the control end of the second switching tube through the first capacitor, so that the current passing through the second switching tube becomes large, the voltage of the first voltage control output end is pulled down in a short time, and therefore the main switch in the load switch is controlled, and the purpose of quick turn-off is achieved.
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Referring to fig. 2, fig. 2 is a schematic diagram of a switch control circuit according to an embodiment of the present invention; the switch control circuit is applied to a load switch, and the switch control circuit 10 includes: a signal input terminal Vin, a power supply voltage input terminal Vcc, a first voltage control output terminal Vout', a first capacitor C1, a first switching tube M1, a first current source IB1, and a second switching tube M2; one end of the first capacitor C1 is connected with the signal input end Vin; the other end of the first capacitor C1 is connected with the output end of the first current source IB1 and the first end of the first switching tube M1; the input end of the current source IB1 is used as a power supply voltage input end Vcc of the switch control circuit and is used for receiving the input of the power supply voltage Vcc; the control end of the first switching tube M1 is connected with the first end of the first switching tube M1 and the control end of the second switching tube M2; the second end of the first switching tube M1 is connected with the second end of the second switching tube M2 and grounded; the first end of the second switching tube M2 serves as a first voltage control output terminal Vout' for controlling the opening and closing of the load switch.
Specifically, in the embodiment, if the voltage of the signal input terminal Vin changes slowly, the charge generated by the first capacitor C1 is absorbed by the first switch tube M1, and the absorbed charge can be supplemented by the first current source IB 1; however, if the voltage of the signal input terminal Vin changes too fast, the charge generated by the first capacitor at the node VC1 cannot be absorbed by the first switch tube M1 or the charge absorbed by the first capacitor C1 in time, and the first current source IB1 is not replenished in time, so that when the voltage change speed of the signal input terminal is greater than the processing speeds of the first current source IB1 and the first switch tube M1 according to the capacitance characteristics, the voltage of the node VC1 has the same change as the voltage change direction of the signal input terminal, and the change speed and the change amplitude of the node VC1 are positively correlated with the voltage change speed and the change amplitude of the signal input terminal.
The second end of the first switching tube M1 is grounded, which causes the Vgs (voltage difference between the gate and the source) of the first switching tube M1 to be instantaneously increased, so that the current passing through the second switching tube M2 is increased, the first voltage control output end is pulled down, and the main switch of the load switch is controlled to be turned off.
In this embodiment, the specific types of the first switching tube M1 and the second switching tube M2 are not limited, and optionally, the first switching tube M1 and the second switching tube M2 may be PMOS tubes or NMOS tubes, and in this embodiment, optionally, the first switching tube M1 and the second switching tube M2 are NMOS tubes.
According to the switch control circuit provided by the invention, as the characteristic of the first capacitor is that the capacitor releases or absorbs charge when the voltage at two ends of the first capacitor changes, the capacitor has the characteristic of high pass, namely, the current passing through the capacitor and the voltage change rate at two ends of the capacitor are in a direct proportion relation. The current on the capacitor is coupled to the first end of the first switching tube, namely the control end of the second switching tube through the first capacitor, so that the current passing through the second switching tube becomes large, the voltage of the first voltage control output end is pulled down in a short time, and therefore the main switch in the load switch is controlled, and the purpose of quick turn-off is achieved.
Referring to fig. 3, fig. 3 is a schematic structural diagram of the load switch according to the embodiment of the present invention; the load switch includes: the switching control circuit 10, the main switching tube 20 and the driving module 30, wherein the switching control circuit 10 is the switching control circuit described in the above embodiment.
In this embodiment, the specific structure of the main switching tube 20 is not limited, alternatively, in this embodiment, the main switching tube 20 is the simplest switching structure, such as the NMOS tube M0, and in other embodiments of the present invention, the main switching tube 20 may also be other switching structures, which is not limited in this embodiment.
The control end of the main switching tube M0 is connected with a driving module and a first voltage control output end Vout' of the switch control circuit 10, and the driving module 30 is used for providing driving voltage for the main switching tube M0 and switching on or off the main switching tube; a first end of the main switching tube M0 is connected with a signal input end Vin of the switch control circuit 10; the second terminal of the main switching tube M0 serves as the signal output terminal Vout of the load switch.
The specific structure of the driving module is not limited in this embodiment, and optionally, the driving module includes: a second current source IB2 and a Zener Diode (Zener Diode); the input end of the second current source IB2 is connected with the power supply voltage input end Vcc; the output end of the second current source IB2 is connected with the control end of the main switching tube M0; the anode of the Zener Diode is connected with the second end of the main switching tube M0; the negative pole of the Zener Diode is connected to the control terminal of the main switching tube M0.
As described in the above embodiments, the working principle of the load switch in this embodiment is as follows: when the voltage change speed of the signal input terminal Vin is faster, the first capacitor C1 of the switch control circuit 10 is turned on, and when the voltage of the node VC1 rises rapidly, the node VC2 cannot rise rapidly, so that the Vgs of the first switching tube M1 is instantaneously increased, and the current through the second switching tube M2 is increased, so that the voltage of the control terminal of the main switching tube M0 is pulled down, and the main switching tube is turned off, so that the signal with the faster voltage change of the signal input terminal Vin cannot be transmitted to the signal output terminal Vout.
In this embodiment, by adjusting the capacitance value of the first capacitor C1, the response speed of the switching control circuit can be determined. For example, the first capacitance C1 is to be left untreated at a 1V/100ns input signal rate of change. This results in (1V/100 ns) c1=ib2-IB 1. That is, at such input change rates, the first capacitor C1 may sink and release or the charge that is being sunk by the first current source IB1. When the first current sources IB1 and IB2 are determined, the capacitance of the first capacitor C1 is increased, so that the switch control circuit can process the input signal with a slower rate change (the rate range of the processed signal is larger), and in practical application, (1V/100 ns) c1=ib2-IB 1 is typically used, and then the capacitance of the first capacitor C1 is reduced, which depends on the response time requirement actually required. That is, by adjusting the capacitance value of the first capacitor C1, the response speed of the switch control circuit in the present embodiment can be adjusted.
Referring to fig. 4, fig. 4 is a schematic structural diagram of the load switch according to the embodiment of the present invention; the load switch according to the previous embodiment, further includes: an overpressure treatment module 40.
As shown in fig. 4, the input terminal of the overvoltage processing module 40 is connected to the signal input terminal Vin;
the output end of the overvoltage processing module 40 is connected with the control end of the main switching tube M0;
when the voltage signal change speed of the signal input end Vin is higher than or equal to a first preset threshold value, the switch control circuit 10 controls the main switch tube to be turned off;
when the voltage signal variation speed of the signal input terminal Vin is lower than the first preset threshold, the overvoltage processing module 40 controls the main switching tube to be turned off.
In this embodiment, the specific range of the first preset threshold is not limited, and may be set according to the response speed of the overvoltage processing module in an actual situation. Optionally, the change speed of the voltage that can be processed by the overvoltage processing module 40, which is the fastest, is set as the first preset threshold. Then, the value of the first capacitor C1 in the switch control circuit is set according to the magnitude of the first preset threshold. Optionally, the first preset threshold ranges from 1V/100ns to 10V/100ns, inclusive. In this embodiment, the first preset threshold may be adjusted according to actual requirements, and in this embodiment, a certain single value is not limited.
The specific structure of the overpressure treatment module 40 is not limited in the present embodiment; alternatively, as shown in fig. 5, the overpressure treatment module 40 includes: an input voltage dividing module 41, a comparing module 42 and a closing module 43; the input voltage dividing module 41 includes: the input end, the input end and the grounding end; the comparison module 42 includes a first input, a second input, and an output; the closing module 43 includes a first end, a second end, and a control end.
Wherein the input end of the input voltage dividing module 41 is connected with the signal input end Vin; the output end of the input voltage dividing module 41 is connected with the first input end of the comparison module; a second input end of the comparison module 42 is connected with a reference voltage source BG and receives input of a reference voltage; the output end of the comparison module 42 is connected with the control end of the closing module; the first end of the closing module 43 is connected with the control end of the main switching tube M0; the second terminal of the closing module 43 is grounded.
In this embodiment, specific structures in the input voltage dividing module 41, the comparing module 42 and the closing module 43 are not limited, as shown in fig. 6, and optionally, in this embodiment, the input voltage dividing module 41 includes a second resistor R2 and a third resistor R3 connected in series in sequence; one end of the second resistor R2 far away from the third resistor R3 is connected with the signal input end Vin; one end of the third resistor R3 far away from the second resistor R2 is grounded; the common terminal of the second resistor R2 and the third resistor R3 serves as the output terminal of the input voltage dividing module 41.
It should be noted that, in the present embodiment, the input voltage dividing module 41 may further include other structures, such as the capacitor C01, the capacitor C02 and the capacitor C03 shown in fig. 1, so as to improve the response speed of the input voltage dividing module 41.
The closing module 43 in this embodiment includes a third switching tube M3; the first end of the third switching tube M3 serves as a first end of the closing module 42; a second end of the third switching tube M3 serves as a second end of the closing module 42; the control terminal of the third switching tube M3 serves as the control terminal of the shutdown module 42. Likewise, the specific structure of the closing module 43 is not limited in this embodiment, and other structures may be added to the closing module 43 according to actual needs, which is not described in detail in this embodiment.
The comparison module 42 in this embodiment may optionally include an operational amplifier OP1; the non-inverting input + of the operational amplifier OP1 is the first input of the comparison module 43; an inverting input of the operational amplifier OP 1-as a second input of the comparison module 43.
It should be noted that, in order to increase the voltage value of the power supply voltage, a charge pump may be optionally further included, where the charge pump is located at the input ends of the first current source IB1 and the second current source IB2, so as to provide a larger voltage to the first current source IB1 and the second current source IB2 of the load switch. In the case where the power supply voltage Vcc is large, the charge pump may be omitted as an alternative in the present embodiment.
It should be noted that, in this embodiment, the load switch includes a switch control circuit 10 and an overvoltage processing module 40, where the switch control circuit 10 and the overvoltage processing module 40 can both control the voltage of the gate of the main switching tube M0, so as to control the opening and closing of the main switching tube M0.
As shown in fig. 6, the switch control circuit 10 in the embodiment of the present invention constitutes a subsystem capable of handling a rapid overvoltage event; and the overpressure treatment module 40 constitutes a subsystem capable of handling medium and low speed overpressure event functions. Specifically, the second resistor R2, the third resistor R3, the operational amplifier OP1, the reference voltage source BG and the third switching tube M3 form a conventional overvoltage processing module; the first capacitor C1, the first current source IB1, the first switching tube M1 and the second switching tube M2 form a fast processing subsystem-a switching control circuit. The second current source IB2 and the Zener Diode constitute a conventional Vgs generating circuit.
It should be noted that, in the embodiment, the medium-low speed overvoltage event and the fast overvoltage event are relative concepts, and are qualitative descriptions, the medium-low speed overvoltage event and the fast overvoltage event are relative to the response speed of the overvoltage processing module, and since the response speeds of the input voltage dividing module, the operational amplifier and the third switching tube in the overvoltage processing module are limited, the signal with too fast voltage change cannot be processed, the voltage change signal which can be processed by the overvoltage processing module is defined as the medium-low speed overvoltage event; the voltage change signal which is not processed by the overvoltage processing module is defined as a rapid overvoltage event.
For example, if the voltage at the signal input end is greater than 6V and is determined to be overvoltage, the signal rises from the normal condition of lower than 6V (for example, the signal is input as direct current voltage 5V in the normal working voltage) with the level of 1V/100ns, so that the operational amplifier can respond within 100ns, and the main switching tube M0 can be closed timely, so as to ensure that the voltage at the signal output end does not generate too high pulse. The voltage change speed is 1V/100ns, which can be defined as a medium-low speed overvoltage event; if the voltage at the signal input is overshot too fast from the normal operating voltage of 5V, for example 10V/100ns, the input signal has reached 15V within 100ns, during which the op amp and the third switching tube M0 cannot handle in time, which results in a high voltage overshoot at the signal output. A voltage change rate of 10V/100ns may be defined as a rapid overvoltage event. When the operational amplifier and the third switching tube M3 cannot be processed in time, the switch control circuit can process in time, and the main switching tube M0 is disconnected in time, so that the voltage overshoot amplitude of the signal output end is reduced.
In this embodiment, by adjusting the size of the first capacitor C1 in the switch control circuit, the response speed of the fast overvoltage event is adjusted, including:
the response speeds of the operational amplifier OP1 and the third switching tube M3 are determined. For example they can handle signal inputs varying at a rate of 1V/100 ns;
then the first capacitance C1 is left untreated at a 1V/100ns input signal rate of change. This results in (1V/100 ns) c1=ib2-IB 1. That is, at such input change rates, the first capacitor C1 may sink and release or the charge that is being sunk by the first current source IB 1;
then, in fact, when the first current source IB1 is determined, the capacitance of the first capacitor C1 is increased, and the switch control circuit is capable of processing the input signal with a slower rate change (the rate range of the processed signal is larger), and in practical application, (1V/100 ns) c1=ib2-IB 1 is typically allowed, and then the capacitance of the first capacitor C1 is reduced, which depends on the response time requirement actually required.
Alternatively, the medium-low speed overvoltage event can be an overvoltage event with a response speed within 50ns-200 ns; the fast overvoltage event is an overvoltage event with a response speed within 50 ns.
The specific operation principle of the load switch provided in this embodiment will be described by taking the load switch structure shown in fig. 7 as an example:
in this embodiment, after the voltage signal is input to the signal input terminal, the signal enters the overvoltage processing module 40 and the switch control circuit 10 at the same time, but only when the signal voltage changes too fast, the processing speed of the overvoltage processing module 40 cannot keep pace, and the main switch tube M0 is turned off mainly by the switch control circuit 10. However, when the input signal changes slowly, the voltage changes faster and then can be turned on due to the capacitance characteristic of the first capacitor, so the switch control circuit 10 will not process the signal. That is, the switch control circuit 10 can only handle rapid signal changes, while the overvoltage processing module 40 can handle conventional speed change input signals.
Namely, 1) when an overvoltage event occurs at a medium or low speed, three modules of the input voltage dividing module, the comparing module and the closing module in the whole block diagram are responsible for detecting and executing the disconnection of the main switching tube M0, and the processing process at the medium or low speed has higher precision and can keep the disconnection precision when the input voltage slowly changes or changes at the medium speed.
2) When the input voltage rises rapidly, the accuracy of disconnection is not a main consideration, but the lower the voltage overshoot of the output port is, the better is ensured, at the moment, the switch control circuit is responsible for processing, the first capacitor C1, the first current source IB1 and the first switching tube M1 detect the sudden change of the input voltage rapidly, and the second switching tube M2 closes the main switching tube M0 rapidly.
Referring to fig. 7, fig. 7 is a graph showing response speed comparison in various cases according to an embodiment of the present invention; as shown in fig. 7, the abscissa is the overpressure event speed and the ordinate is the response speed. Specifically, as shown in fig. 7, when the speed of the overvoltage event is small, that is, the voltage change of the signal input end is slow, the response speed of the overvoltage processing module is fast, and the response speed of the switch control circuit is low; when the overvoltage event speed is high, namely the voltage change of the signal input end is high, the response speed of the overvoltage processing module is high, and the response speed of the switch control circuit is high; when the load switch is provided with the switch control circuit and the overvoltage processing module, the overvoltage processing module mainly responds to the overvoltage event when the speed of the overvoltage event is small, and the switch control circuit mainly responds to the overvoltage event when the speed of the overvoltage event is large, and the comprehensive effect is shown as a dotted line in fig. 7.
It should be noted that, in this embodiment, the main differences between the switch control circuit and the overvoltage processing module are as follows: the overvoltage processing module has better processing capability on medium-low speed input voltage change and can keep higher precision. The switch control circuit can cope with rapid input changes. The combination of the two ensures that the main switching tube M0 can be disconnected relatively quickly under different conditions.
That is, the load switch provided in this embodiment includes a switch control circuit and an overvoltage processing module, which can combine the high-precision control of the overvoltage processing module in the medium-low speed overvoltage event and the fast response characteristic of the switch control circuit in the fast overvoltage event, so that the load switch has a fast response speed.
And the circuit structure of the switch control circuit is simple, so that more power consumption is not increased, and the aim of improving the response speed of the load switch under the condition of not increasing the power consumption as much as possible is fulfilled.
It should be noted that, in the present specification, each embodiment is described in a progressive manner, and each embodiment is mainly described as different from other embodiments, and identical and similar parts between the embodiments are all enough to be referred to each other.
It is further noted that relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that an article or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such article or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in an article or apparatus that comprises such element.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. A switch control circuit for use with a load switch, the switch control circuit comprising:
the power supply comprises a signal input end, a power supply voltage input end, a first voltage control output end, a first capacitor, a first switching tube, a first current source and a second switching tube;
one end of the first capacitor is connected with the signal input end;
the other end of the first capacitor is connected with the output end of the first current source and the first end of the first switching tube;
the input end of the current source is used as a power supply voltage input end of the switch control circuit and is used for receiving the input of power supply voltage;
the control end of the first switching tube is connected with the first end of the first switching tube and the control end of the second switching tube;
the second end of the first switching tube is connected with the second end of the second switching tube and grounded;
the first end of the second switching tube is used as the first voltage control output end and used for controlling the opening and closing of the load switch.
2. The switch control circuit of claim 1, further comprising a first resistor and a second capacitor;
one end of the first resistor is connected with the second end of the first switch tube, and the other end of the first resistor is connected with the signal input end;
one end of the second capacitor is connected with the second end of the first switch tube, and the other end of the second capacitor is grounded.
3. A load switch, comprising:
the switching control circuit, the main switching tube and the driving module;
wherein the switch control circuit is the switch control circuit of claim 1 or 2;
the control end of the main switching tube is connected with the driving module and the first voltage control output end of the switching control circuit, and the driving module is used for providing driving voltage for the main switching tube and switching on or off the main switching tube;
the first end of the main switch tube is connected with the signal input end of the switch control circuit;
the second end of the main switch tube is used as a signal output end of the load switch.
4. A load switch according to claim 3, wherein the drive module comprises: a second current source and a zener diode;
the input end of the second current source is connected with the power supply voltage input end;
the output end of the second current source is connected with the control end of the main switching tube;
the positive electrode of the Zener diode is connected with the second end of the main switching tube;
and the cathode of the zener diode is connected with the control end of the main switching tube.
5. The load switch of claim 4, further comprising an overvoltage processing module;
the input end of the overvoltage processing module is connected with the signal input end;
the output end of the overvoltage processing module is connected with the control end of the main switching tube;
when the voltage signal change speed of the signal input end is higher than or equal to a first preset threshold value, the switch control circuit controls the main switch tube to be turned off;
and when the voltage signal change speed of the signal input end is lower than the first preset threshold value, the overvoltage processing module controls the main switching tube to be switched off.
6. The load switch of claim 5, wherein the first predetermined threshold value ranges from 1V/100ns to 10V/100ns, inclusive.
7. The load switch of claim 5, wherein the overvoltage processing module comprises:
the device comprises an input voltage dividing module, a comparison module and a closing module;
the input voltage dividing module includes: the input end, the input end and the grounding end;
the comparison module comprises a first input end, a second input end and an output end;
the closing module comprises a first end, a second end and a control end;
the input end of the input voltage dividing module is connected with the signal input end;
the output end of the input voltage dividing module is connected with the first input end of the comparison module;
the second input end of the comparison module is connected with a reference voltage source and receives the input of a reference voltage;
the output end of the comparison module is connected with the control end of the closing module;
the first end of the closing module is connected with the control end of the main switching tube;
the second end of the closing module is grounded.
8. The load switch of claim 7, wherein the shutdown module comprises a third switching tube;
the first end of the third switching tube is used as the first end of the closing module;
the second end of the third switch tube is used as the second end of the closing module;
and the control end of the third switching tube is used as the control end of the closing module.
9. The load switch of claim 8, wherein the switch is configured to control the switching of the load,
the input voltage dividing module comprises a second resistor and a third resistor which are sequentially connected in series;
one end of the second resistor, which is far away from the third resistor, is connected with the signal input end;
one end of the third resistor far away from the second resistor is grounded;
the common end of the second resistor and the third resistor is used as the output end of the input voltage dividing module;
the comparison module comprises an operational amplifier;
the non-inverting input end of the operational amplifier is used as a first input end of the comparison module;
the inverting input of the operational amplifier serves as the second input of the comparison module.
10. The load switch of claim 8 or 9, wherein the first switching tube, the second switching tube, and the third switching tube are NMOS tubes.
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| CN201810750728.4A CN108599100B (en) | 2018-07-10 | 2018-07-10 | Switch control circuit and load switch |
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| CN201810750728.4A CN108599100B (en) | 2018-07-10 | 2018-07-10 | Switch control circuit and load switch |
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| CN108599100A CN108599100A (en) | 2018-09-28 |
| CN108599100B true CN108599100B (en) | 2024-02-09 |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN109039315B (en) * | 2018-10-29 | 2023-09-22 | 上海艾为电子技术股份有限公司 | Analog switch circuit for adjusting turn-on time |
| CN109379071B (en) * | 2018-12-20 | 2023-09-19 | 上海艾为电子技术股份有限公司 | Analog switch circuit |
| CN113867303A (en) * | 2021-10-25 | 2021-12-31 | 杭州和利时自动化有限公司 | IO channel circuit and DCS system |
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