Power supply slow start and short circuit protection system for handheld scanner

Abstract

The power supply slow start and short circuit protection system for the handheld scanner comprises a power supply, a power supply slow start module and a short circuit protection module, the power supply is connected with the input end of the power supply slow-start module and used for supplying power to the power supply slow-start module; the output end of the power supply slow-start module is connected with the input end of the short-circuit protection module; the power supply slow start module is used for suppressing surge current after the power supply is turned on to obtain slow start current, and inputting the slow start current to the short circuit protection module; the short-circuit protection module is used for cutting off a power supply loop when the handheld scanner is short-circuited; the system adopts a full-hardware architecture, and effectively solves the problem that a power supply cannot be cut off in a short time when a handheld scanner in the prior art is overlarge in starting instant current and equipment is short-circuited, so that the reliability and the safety protection level of the equipment are comprehensively improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of short-circuit protection, and particularly relates to a power slow start and short-circuit protection system for a handheld scanner. BACKGROUND

[0002] As the core data acquisition equipment in the intelligent building industry and digital twinning, the stability and safety of the power supply system of the handheld scanner directly determine the continuous operation capability of the equipment and the safety of user operation. The handheld scanner integrates a plurality of circuit boards, which work cooperatively at different voltage levels to realize various functions of the scanner. The stability and safety of the power supply are crucial in the power supply system of the handheld scanner. However, the existing power supply system often has a large current impact when starting, which not only affects the service life of the equipment, but also may cause data loss or equipment damage. However, the existing power management system cannot effectively control the gradual increase of the current when starting, resulting in a large current impact on the equipment at the starting moment. In addition, the handheld scanner is prone to short circuit during use due to complex environment. The existing short-circuit protection measures are often not sensitive enough to cut off the power supply within a short time, resulting in equipment damage and even safety accidents. SUMMARY

[0003] To solve the problems of excessive current at the starting moment of the handheld scanner and the inability to cut off the power supply within a short time when the equipment is short-circuited, a power slow start and short-circuit protection system for a handheld scanner is provided.

[0004] A power slow start and short-circuit protection system for a handheld scanner, characterized in that it comprises a power supply, a power slow start module and a short-circuit protection module.

[0005] The power supply is connected to the input end of the power slow start module for supplying power to the power slow start module.

[0006] The output end of the power slow start module is connected to the input end of the short-circuit protection module. The power slow start module is used to suppress the inrush current after the power supply is turned on to obtain a slow start current, and the slow start current is input to the short-circuit protection module. The short-circuit protection module is used to supply power to the handheld scanner according to the received slow start current. The short-circuit protection module is also used to cut off the power supply loop when a short circuit occurs in the circuit of the handheld scanner.

[0007] The power slow start and short-circuit protection system for a handheld scanner of the present application adopts a full hardware architecture and can realize suppression of the inrush current after the power supply is turned on through pure hardware logic control of subtractors, comparators and transistor networks. When a short circuit occurs in the handheld scanner, the power supply loop is cut off within a short time to isolate the short circuit fault, thereby comprehensively improving the reliability and safety protection level of the equipment.

[0008] The power slow start and short circuit protection system for a handheld scanner of the present application can significantly improve the response speed and anti-interference, and the overcurrent protection response time can reach ≤2μs, which is much better than the general ≥50μs level of the prior art, and completely eliminates the software processing delay; since no program code is involved, the risk of software runaway, crash or false triggering is avoided, and the system reliability is improved to 99.99%, the feature of the present application is that discrete components are used in cooperation with a driving chip to realize hardware closed loop of signal detection, logic judgment and power control. BRIEF DESCRIPTION OF DRAWINGS

[0009] Figure 1 A schematic diagram of a power slow start and short circuit protection system for a handheld scanner is one of the specific embodiments of the present application. DETAILED DESCRIPTION

[0010] Specific embodiment one: the present embodiment will be described below in combination with the drawings of the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application: Figure 1

[0011] A power slow start and short circuit protection system for a handheld scanner, comprising: a power supply, a power slow start module and a short circuit protection module;

[0012] The power supply is connected with the input end of the power slow start module for supplying power to the power slow start module.

[0013] The output end of the power slow start module is connected with the input end of the short circuit protection module; the power slow start module is used to suppress the inrush current after the power supply is turned on to obtain a slow start current, and the slow start current is input to the short circuit protection module; the short circuit protection module is used to supply power to the handheld scanner according to the received slow start current, and the short circuit protection module is also used to cut off the power supply loop when a short circuit occurs in the circuit of the handheld scanner.

[0014] Specifically, there is a large current impact when the power supply system is started, which not only affects the service life of the equipment, but also may cause data loss or equipment damage, and the power slow start module can suppress the inrush current to prevent equipment damage and improve the stability of the system; during the use of the handheld scanner, short circuit may occur to cause equipment damage or even safety accidents, and the short circuit protection module can timely detect the short circuit and cut off the main loop of the power supply within a short time to prevent further damage to the equipment.

[0015] Further, the power slow start module comprises: a PMOS transistor Q1, an NMOS transistor Q7, a PNP type triode Q3, resistors R2, R3, R4, R5 and a capacitor C1.

[0016] ​The positive pole VBAT of the power supply is connected with one end of the resistor R2, one end of the resistor R3, the emitter of the PNP triode Q3 and the source of the PMOS transistor Q1; the base of the PNP triode Q3 is connected with the other end of the resistor R3 and one end of the capacitor C1; the collector of the PNP triode Q3 is connected with the other end of the capacitor C1, one end of the resistor R4 and one end of the resistor R5; the gate of the PMOS transistor Q1 is connected with the other end of the resistor R4; the gate of the NMOS transistor Q7 is connected with the other end of the resistor R2; the negative pole PGND of the power supply is connected with the drain of the NMOS transistor Q7; the source of the NMOS transistor Q7 and the other end of the resistor R5 are connected with the negative pole GND respectively; the drain of the PMOS transistor Q1 as the output end of the power supply slow start module is connected with the input end of the short circuit protection module.

[0017] After the power supply is powered, the current passes through the resistor R2 to make the NMOS transistor Q7 enter the saturated conduction state, the PNP triode Q3 is in the saturated conduction state, the PMOS transistor Q1 is in the cut-off state, the current passes through the resistor R3 to charge the capacitor C1, the triode Q3 is changed from the saturated conduction state to the cut-off state during the charging process of the capacitor C1, the transistor Q1 is changed from the cut-off state to the saturated state, and the transistor Q1 outputs the slow start current after being changed to the saturated state.

[0018] After the power supply VBAT input passes through the resistor R2, the transistor Q7 enters the saturated state to conduct PGND and GND, at this time, the PNP triode Q3 is in the saturated state to conduct, the gate voltage of the PMOS transistor Q1 is VBAT, the PMOS transistor Q1 is cut off, the current passes through the resistor R3 to charge the capacitor C1, the base voltage of the PNP triode Q3 gradually rises to VBAT, and the saturated state of the PNP triode Q3 is gradually changed to the cut-off state during the process, until UebUon, the PNP triode Q3 is completely in the cut-off state, wherein Ueb is the voltage difference between the emitter and the base of the PNP triode Q3, and Uon is the turn-on voltage of the PNP triode Q3; and during the process, the gate voltage of the PMOS transistor Q1 is also gradually reduced, and the state of the PMOS transistor Q1 is gradually changed from the cut-off state to the saturated state, until VsgVon, the PMOS transistor Q1 is completely in the saturated state, wherein Vsg is the voltage difference between the source and the gate of the PMOS transistor Q1, and Von is the turn-on voltage of the PMOS transistor Q1.

[0019] During the above process, the power supply is changed from the cut-off state to the saturated state of the PMOS transistor Q1, and the process from complete turn-off to complete turn-on is realized; by adjusting the parameters of the resistor R3 and the capacitor C1, the setting of the slow start time of the power supply can be realized.

[0020] Further, the short-circuit protection module comprises a subtractor D1, a comparator D2, an NMOS transistor Q2, an NPN transistor Q4, an NPN transistor Q5, an NPN transistor Q6, a resistor R1, a resistor R6, a resistor R7, a resistor R8, a resistor R9, a resistor R10, a resistor R11, a capacitor C2, a reference voltage VREF, a direct current voltage VDD and a gate drive chip.

[0021] One end of the resistor R1 and the same direction input end of the subtractor D1 are connected with the drain of the PMOS transistor Q1, and the other end of the resistor R1 is connected with the opposite direction input end of the subtractor D1 and the drain of the NMOS transistor Q2; the output end of the subtractor D1 is connected with the same direction input end of the comparator D2; the opposite direction input end of the comparator D2 is connected with the reference voltage VREF.

[0022] The output end of the comparator D2 is connected with one end of the capacitor C2, the base of the NPN transistor Q4 and one end of the resistor R9; the collector of the NPN transistor Q4 is connected with the base of the NPN transistor Q5 and one end of the resistor R6; the collector of the NPN transistor Q5 is connected with the other end of the resistor R9, one end of the resistor R7 and one end of the resistor R10; the other end of the resistor R10 is connected with the base of the NPN transistor Q6; the collector of the NPN transistor Q6 is connected with one end of the resistor R8 and one end of the resistor R11.

[0023] The direct current voltage VDD is connected with the other end of the resistor R6, the other end of the resistor R7 and the other end of the resistor R8.

[0024] The other end of the resistor R11 is connected with the input end of the gate drive chip; the output end of the gate drive chip is connected with the gate of the NMOS transistor Q2; the source of the NMOS transistor Q2 is connected with the power output end VOUT; the negative pole GND is connected with the other end of the capacitor C2, the emitter of the NPN transistor Q4, the emitter of the NPN transistor Q5 and the emitter of the NPN transistor Q6.

[0025] The subtractor D1 is used for obtaining the voltage drop generated by the current passing through the resistor R1 and amplifying, and inputting the amplified voltage drop to the same direction input end of the comparator D2; the comparator D2 is used for comparing the amplified voltage drop input to the same direction input end and the reference voltage VREF input to the opposite direction input end; when the handheld scanner occurs short circuit, the comparator D2 outputs high level, the input end of the gate drive chip is low level, the gate drive chip cannot work normally, and the power supply loop is disconnected.

[0026] Specifically, the voltage drop generated by the current passing through the current detection resistor R1 is captured by the subtracter D1 and amplified to detect the main loop current, and the output of the subtracter D1 is connected to the same input of the comparator D2 and compared with the reference voltage VREF connected to the opposite input of the comparator D2. In the normal working condition, the voltage at the same input of the comparator D2 is less than VREF, and the output of the comparator D2 outputs low level, at this time, the base voltage of the NPN transistor Q4 is low level, the NPN transistor Q4 is in the off state, the base voltage of the NPN transistor Q5 is high level due to the existence of the pull-up resistor R6, the NPN transistor Q5 is turned on, the base voltage of the NPN transistor Q6 is low level due to the existence of the pull-up resistor R7, the NPN transistor Q6 is turned off, and the input of the gate drive chip is high level due to the existence of the pull-up resistor R8, so that the gate drive chip works normally, and the NMOS transistor Q2 is turned on to make the power supply work normally. When a short circuit occurs, the current is too large, which causes the voltage drop generated on the current detection resistor R1 to be too large, so that the voltage at the same input of the comparator D2 is greater than VREF, and the output of the comparator D2 outputs high level. At this time, the base voltage of the NPN transistor Q4 is high level, the NPN transistor Q4 is turned on, the base voltage of the NPN transistor Q5 is low level due to the existence of the pull-up resistor R6, the NPN transistor Q5 is turned off, the base voltage of the NPN transistor Q6 is high level due to the existence of the pull-up resistor R7, the NPN transistor Q6 is turned on, the input of the gate drive chip is low level due to the existence of the pull-up resistor R8, so that the gate drive chip cannot work normally, the NMOS transistor Q2 is turned off, and the power supply loop is disconnected. At this time, the base voltage of the NPN transistor Q4 is always clamped to high level by the resistor R9, and the NMOS transistor Q2 is always turned off by the above process, until the power is reconnected, and the self-locking mode can effectively avoid the situation that the short circuit is disconnected and then restarted, and the problem is solved before the power is reconnected and started.

[0027] Further, the gate drive chip is an LM5060MM gate drive chip.

[0028] Specifically, since the current of the main power path is large, a power MOS tube can be selected as a switch for control, which can pass through a large current and has a small conduction resistance. However, its conduction characteristic is not suitable for being directly controlled by a small signal, so a gate drive chip LM5060MM needs to be added to ensure the ability to stably drive the MOS tube.

[0029] Further, the power supply is a direct current voltage source with an output of 15V;

[0030] Further, the reference voltage VREF is a direct current voltage of 1.8V, and the direct current voltage VDD is 5V. Specifically, VDD is provided by the power supply, and VBAT is obtained by DCDC voltage reduction.

[0031] While the application has been described with reference to particular embodiments, it is to be understood that the application is not limited to the particulars disclosed. Rather, it is a continuation of the principles and applications of the present application. It is therefore to be understood that numerous modifications, both to the examples described and to the preferred embodiments, can be effected and that the above described embodiments are merely illustrative of the principles and applications of the present application. It is to be understood that the phraseology and terminology employed herein are by way of the use of the Slang and that the limitations are to be construed in the broadest and intended sense to encompass all such modifications. It is to be understood that the use of the singular includes the plural, the use of "or" means "and / or", and all process variables are intended to be controllable automatically or semi-automatically. It is intended that each of the dependent claims be considered separately and independently. It is intended that each element recited in any claim is considered to be optional unless specifically limited to the contrary.

Claims

1. A power soft-start and short-circuit protection system for a handheld scanner, characterized in that, include: Power supply, power soft start module and short circuit protection module; The power supply is connected to the input terminal of the power soft-start module to supply power to the power soft-start module; The output of the power soft-start module is connected to the input of the short-circuit protection module; The power soft-start module is used to suppress the surge current after the power is turned on to obtain a soft-start current, which is then input to the short-circuit protection module. The short-circuit protection module is used to supply power to the handheld scanner based on the received soft-start current. The short-circuit protection module is also used to cut off the power circuit when a short circuit occurs in the handheld scanner circuit.

2. The power soft-start and short-circuit protection system for a handheld scanner according to claim 1, characterized in that: The power soft-start module includes: PMOS transistor Q1, NMOS transistor Q7, PNP transistor Q3, resistors R2, R3, R4, R5 and capacitor C1; The positive terminal VBAT of the power supply is connected to one end of resistor R2, one end of resistor R3, the emitter of PNP transistor Q3, and the source of PMOS transistor Q1. The base of PNP transistor Q3 is connected to the other end of resistor R3 and one end of capacitor C1. The collector of PNP transistor Q3 is connected to the other end of capacitor C1, one end of resistor R4, and one end of resistor R5. The gate of PMOS transistor Q1 is connected to the other end of resistor R4. The gate of NMOS transistor Q7 is connected to the other end of resistor R2. The negative terminal PGND of the power supply is connected to the drain of NMOS transistor Q7. The source of NMOS transistor Q7 and the other end of resistor R5 are connected to the negative terminal GND. The drain of PMOS transistor Q1 is connected as the output terminal of the power supply soft-start module and the input terminal of the short-circuit protection module.

3. The power soft-start and short-circuit protection system for a handheld scanner according to claim 2, characterized in that: The short-circuit protection module includes: subtractor D1, comparator D2, NMOS transistor Q2, NPN transistor Q4, NPN transistor Q5, NPN transistor Q6, resistors R1, R6, R7, R8, R9, R10, R11, capacitor C2, reference voltage VREF, DC voltage VDD, and gate driver chip; One end of resistor R1 and the non-inverting input of subtractor D1 are connected to the drain of PMOS transistor Q1, respectively. The other end of resistor R1 is connected to both the inverting input of subtractor D1 and the drain of NMOS transistor Q2. The output of subtractor D1 is connected to the non-inverting input of comparator D2. The inverting input of comparator D2 is connected to the reference voltage VREF. The output of comparator D2 is connected to one end of capacitor C2, the base of NPN transistor Q4, and one end of resistor R9; the collector of NPN transistor Q4 is connected to the base of NPN transistor Q5 and one end of resistor R6; the collector of NPN transistor Q5 is connected to the other end of resistor R9, one end of resistor R7, and one end of resistor R10; the other end of resistor R10 is connected to the base of NPN transistor Q6; the collector of NPN transistor Q6 is connected to one end of resistor R8 and one end of resistor R11. The DC voltage VDD is simultaneously connected to the other ends of resistors R6, R7, and R8. The other end of resistor R11 is connected to the input terminal of the gate driver chip; the output terminal of the gate driver chip is connected to the gate of NMOS transistor Q2; the source of NMOS transistor Q2 is connected to the power output terminal VOUT; the negative terminal GND is simultaneously connected to the other end of capacitor C2, the emitter of NPN transistor Q4, the emitter of NPN transistor Q5, and the emitter of NPN transistor Q6.

4. A power soft-start and short-circuit protection system for a handheld scanner according to claim 3, characterized in that: The gate driver chip is the LM5060MM gate driver chip.

5. A power soft-start and short-circuit protection system for a handheld scanner according to claim 1, characterized in that: The power supply is a DC voltage source with an output of 15V.

6. A power soft-start and short-circuit protection system for a handheld scanner according to claim 3, characterized in that: The reference voltage VREF is a DC voltage of 1.8V, and the DC voltage VDD is 5V.

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