POS charging current limiting circuit and POS machine charging device

Abstract

The utility model discloses a POS (Point Of Sale) charging current limiting circuit and a POS machine charging device, a resistor R1 is used as a sampling resistor to collect charging current, and when the charging current is increased, the voltage at the output end of the sampling resistor is reduced, so that the voltage input to a negative input end interface of a U1A operational amplifier is reduced. The voltage of the negative input end of the operational amplifier U1A becomes lower and lower along with the increase of the current, when the voltage is smaller than that of the positive input end of the operational amplifier U1A, the output of the output end of the operational amplifier U1A is turned over, the G level of the MOS tube Q1 is pulled from a low potential to a high potential, the MOS tube is turned off, and the capacitor C1 supplies power to the MOS tube. When the sampling resistor is switched on, the switching-off current of the Q1 is 0 after passing through the sampling resistor, the negative input end voltage of the U1A is raised, the negative input end voltage of the U1A is higher than the positive input end, the output of the operational amplifier U1A is turned over, the G level of the MOS tube Q1 is pulled from high potential to low potential to open the MOS tube, and the C1 is charged while the power supply supplies power; through the circuit, the POS machine can be charged while the POS machine is used as a base of the charging device to work, and the adapter can stably work in a rated current range.

Description

TECHNICAL FIELD

[0001] The utility model relates to POS machine charging device technical field especially relates to a POS charging current -limiting circuit and POS machine charging device. BACKGROUND

[0002] POS machine as the popular payment equipment of nowadays, along with the need of use scene, POS machine not only has the power supply mode of direct connection external power supply, also has some POS machine and adopts the mode of built -in power supply to supply power, in order to improve the endurance of POS machine, some POS equipment also has relevant charging base to facilitate its charging at any time and placing on the table top, and when the POS machine is charged on the base, it needs to carry out charging current limit, makes the adapter work at the rated current point, to avoid the negative influence on the circuit of POS machine in the charging process, and currently many POS charging devices do not set the module of stable charging current, and also less than the relevant circuit scheme disclosed in the relevant literature. SUMMARY

[0003] Therefore, the utility model discloses the purpose of providing a kind of POS charging current -limiting circuit and POS machine charging device, which is reliable in implementation and stable in work.

[0004] In order to realize the above technical purpose, the technical scheme adopted by the utility model is:

[0005] A kind of POS charging current -limiting circuit, it is applied to POS machine, it includes resistance R1, resistance R2, resistance R3, P-MOS tube Q1, operational amplifier U1A and capacitor C1;

[0006] Wherein, the resistance R1 is set as sampling resistance, one end of the resistance R1 is electrically connected with the adapter power VIN and one end of resistance R2 respectively, the other end of resistance R1 is electrically connected with the inverting input terminal of operational amplifier U1A and the source electrode S of P-MOS tube respectively;

[0007] The other end of the resistance R2 is electrically connected with one end of resistance R3 and the noninverting input terminal of operational amplifier U1A respectively, the other end of resistance R3 is grounded;

[0008] The power supply end pin GND of the operational amplifier U1A is grounded, and the power supply end pin VDD is electrically connected with the adapter power VIN, and the output terminal of operational amplifier U1A is electrically connected with the gate electrode G of P-MOS tube;

[0009] The drain electrode D of the P-MOS tube is electrically connected with one end of capacitor C1 and charging power Vout respectively;The other end of the capacitor C1 is grounded.

[0010] Based on the above, the scheme also provides a POS machine charging device, which comprises the POS charging current limiting circuit.

[0011] With the technical scheme, the utility model discloses the resistor R1 is used as the sampling resistance to gather the charging current, when the charging current becomes big, the sampling resistance output end voltage becomes small, makes the input to U1A operational amplifier negative input end interface voltage drop, with the current becoming big, U1A negative input end voltage is lower and lower, when voltage is less than U1A positive input end, the operational amplifier U1A output end output flips, and the G level of MOS tube Q1 is pulled from low potential to high potential and is closed to MOS tube by the capacitor C1 power supply.Q1 off current through the sampling resistance current is 0, and U1A negative input end voltage is lifted, so that U1A negative input end voltage is higher than the positive input end, and the operational amplifier U1A output flips, and the G level of MOS tube Q1 is pulled from high potential to low potential and is opened to MOS tube, and is powered by power supply while charging C1;Through the circuit, the base of the POS machine as the charging device can be charged while working, and the adapter can be stably worked within the rated current. BRIEF DESCRIPTION OF DRAWINGS

[0012] In order to more clearly illustrate the technical scheme in the embodiments of the utility model or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or the prior art description, and obviously, the drawings in the following description are only some embodiments of the utility model, and all other drawings obtained by the person skilled in the art without creative labor are within the protection scope of the utility model.

[0013] Figure 1 It is the circuit connection drawing of the current limiting circuit of the scheme;In the drawing, each mark refers to: R1: sampling resistance, R2: resistance, R3: resistance, Q1: P-MOS tube, U1: operational amplifier, C1: capacitor, VIN: adapter power supply, Vout: charging power supply. DETAILED DESCRIPTION

[0014] The utility model will be further described in detail in combination with the drawings and embodiments. It is particularly pointed out that the following embodiments are only used for illustrating the utility model, but do not limit the scope of the utility model. Similarly, the following embodiments are only part of the embodiments of the utility model rather than all the embodiments, and all other embodiments obtained by the person skilled in the art without creative labor are within the protection scope of the utility model.

[0015] In combination with Figure 1 As shown in the drawing, the embodiment scheme a kind of POS charging current limiting circuit, it is applied to POS machine, it includes resistance R1, resistance R2, resistance R3, P-MOS tube Q1, operational amplifier U1A and capacitor C1.

[0016] The resistor R1 is set as a sampling resistor, one end of the resistor R1 is electrically connected with the adapter power supply VIN and one end of the resistor R2 respectively, and the other end of the resistor R1 is electrically connected with the inverting input end of the operational amplifier U1A and the source S of the P-MOS tube respectively;

[0017] The other end of the resistor R2 is electrically connected with one end of the resistor R3 and the non-inverting input end of the operational amplifier U1A respectively, and the other end of the resistor R3 is grounded.

[0018] The power supply end pin GND of the operational amplifier U1A is grounded, the power supply end pin VDD is electrically connected with the adapter power supply VIN, and the output end of the operational amplifier U1A is electrically connected with the gate G of the P-MOS tube.

[0019] The drain D of the P-MOS tube is electrically connected with one end of the capacitor C1 and the charging power supply Vout respectively, and the other end of the capacitor C1 is grounded.

[0020] In the embodiment, the resistor R1 is used as a sampling resistor for detecting the adapter output current, so that the voltage at the back end of the resistor R1 changes with the current, and the back end of the resistor R1 is connected to the input negative end (inverting input end) of the operational amplifier U1A. The positive end (non-inverting input end) of the operational amplifier U1A is connected to the stable voltage obtained by the voltage division of the resistor R2 and the resistor R3.

[0021] Correspondingly, the voltages at the negative end and the positive end of the operational amplifier U1A can be represented as follows:

[0022] V_U1+=VIN*(R3 / (R2+R3))

[0023] V_U1-=VIN-(Iin*R1)

[0024] When the current exceeds the set value, that is, V_U1+ is greater than V_U1-, the U1A outputs high level, Q1 is turned off, and C1 is powered. When V_U1+ is less than V_U1-, the operational amplifier U1A outputs low level, Q1 is turned on, and VIN is powered and C1 is charged. In this way, the charging current is limited.

[0025] Based on the characteristics of the circuit, the resistor R1 is used as a sampling resistor for detecting the current through the P-MOS tube Q1, and the current signal is converted into a voltage signal input to the operational amplifier U1A. The operational amplifier U1A controls the gate voltage of the P-MOS tube Q1 according to the input voltage signal, so as to realize the current limiting of the charging current.

[0026] Specifically, the present scheme uses the resistance R1 as a sampling resistance to collect the charging current, when the charging current becomes large, the voltage at the output end of the sampling resistance becomes small, so that the voltage drop at the negative input end interface of the operational amplifier U1A is input. With the increase of the current, the voltage at the negative input end of the operational amplifier U1A becomes lower and lower, when the voltage is less than the voltage at the positive input end of the operational amplifier U1A, the output end of the operational amplifier U1A outputs flip, and the G level of the P-MOS tube Q1 is pulled from low potential to high potential to turn off the MOS tube powered by the capacitor C1. The current flowing through the sampling resistance is 0 when the P-MOS tube Q1 is turned off, the voltage at the negative input end of the operational amplifier U1A is raised, so that the voltage at the negative input end of the operational amplifier U1A is higher than the voltage at the positive input end, the output of the operational amplifier U1A flips, and the G level of the P-MOS tube Q1 is pulled from high potential to low potential to turn on the P-MOS tube, which is powered by the power supply and charges the C1 at the same time. Through the circuit, the POS machine as the base of the charging device can be charged while working, and the adapter can work stably within the rated current.

[0027] Based on the above, the present scheme also provides a POS machine charging device, which comprises the above-mentioned POS charging current limiting circuit.

[0028] The above-mentioned is only part of the embodiments of the present application, and does not limit the protection scope of the present application, any equivalent device or equivalent process transformation based on the content of the present application specification and drawings, or direct or indirect application in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A POS charging current limiting circuit applied to a POS machine, characterized in that, It includes resistance R1, resistance R2, resistance R3, P-MOS tube Q1, operational amplifier U1A and capacitor C1; Wherein, the resistance R1 is set as a sampling resistance, one end of the resistance R1 is electrically connected with the adapter power supply VIN and one end of the resistance R2 respectively, the other end of the resistance R1 is electrically connected with the inverting input terminal of the operational amplifier U1A and the source S of the P-MOS tube respectively; The other end of the resistance R2 is electrically connected with one end of the resistance R3 and the non-inverting input terminal of the operational amplifier U1A respectively, the other end of the resistance R3 is grounded; The power supply end pin GND of the operational amplifier U1A is grounded, the power supply end pin VDD is electrically connected with the adapter power supply VIN, the output end of the operational amplifier U1A is electrically connected with the gate G of the P-MOS tube; The drain D of the P-MOS tube is electrically connected with one end of the capacitor C1 and the charging power supply Vout respectively, the other end of the capacitor C1 is grounded.

2. A POS machine charging device, characterized by: It includes the POS charging current limiting circuit of claim 1.

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