Step-down DC / DC switching power supply circuit with protection function and battery charging circuit

Abstract

According to the step-down DC / DC switching power supply circuit with the protection function and the battery charging circuit, a signal input end of a switching regulator chip U1 is connected with an output port of a charger, a signal output end of the switching regulator chip U1 is connected with a negative electrode of a fly-wheel diode D2 and one end of an inductor L1, and the other end of the inductor L1 is connected with one end of a capacitor C4, a positive electrode of a capacitor C5 and a voltage output end; the anode of D2, the other end of the capacitor C4 and the cathode of the capacitor C5 are connected with the system ground; a feedback end of the U1 is connected with one end of a resistor R6 and one end of a resistor R7, the other end of the resistor R6 is connected with a voltage output end, and the other end of the resistor R7 is connected with a system ground; a switch end of the U1 is connected with one end of a resistor R8 and a collector electrode of a triode Q2, the other end of the resistor R8 is connected with a signal input end of the U1, a base electrode of the Q2 is connected with one end of a resistor R10, the other end of the resistor R10 is connected with a positive electrode of a capacitor C6, one end of a resistor R9, a first battery voltage end and a second battery voltage end, and a negative electrode of the capacitor C6, the other end of the resistor R9 and an emitter electrode of the triode Q2 are connected with a system ground. And the output voltage is adjustable.

Description

Technical Field

[0001] The utility model relates to the field of DC / DC switching power supplies, in particular to a step-down DC / DC switching power supply circuit with protection functions and a battery charging circuit. Background Art

[0002] Switching power supplies have been widely used in many fields due to their high efficiency and reliability, such as industrial automation, medical equipment, computers and peripheral equipment, etc. Different circuits require different voltages to work properly.

[0003] A step-down DC / DC switching power supply is an electronic circuit that converts high DC voltage into low DC voltage. In most cases, the high voltage is converted to low voltage and the voltage is directly output. In the absence of load, the DC voltage is always output. If it encounters conductive objects, safety accidents are likely to occur. Utility Model Content

[0004] In view of the problems existing in the prior art, the utility model provides a step-down DC / DC switching power supply circuit and a battery charging circuit with protection function. When there is no load, no DC voltage is output, and the output voltage is adjustable. It can be used as a front-stage protection circuit of the charging circuit. When the charging object is not connected, no voltage is output. Only when charging, the voltage is output for charging.

[0005] The utility model is realized by the following technical solutions:

[0006] A step-down DC / DC switching power supply circuit with a protection function, comprising a switching regulator chip U1, a freewheeling diode D2, an inductor L1, a capacitor C5 and a transistor Q2;

[0007] The signal input end of the switching regulator chip U1 is connected to the output port of the charger, the signal output end of the switching regulator chip U1 is respectively connected to the cathode of the freewheeling diode D2 and one end of the inductor L1, the other end of the inductor L1 is respectively connected to one end of the capacitor C4, the anode of the capacitor C5 and the voltage output end, the anode of the freewheeling diode D2, the other end of the capacitor C4 and the cathode of the capacitor C5 are connected to the system ground;

[0008] The feedback end of the switching regulator chip U1 is connected to one end of the resistor R6 and one end of the resistor R7 respectively, the other end of the resistor R6 is connected to the voltage output end, and the other end of the resistor R7 is connected to the system ground;

[0009] The switch end of the switching regulator chip U1 is respectively connected to one end of the resistor R8 and the collector of the transistor Q2, the other end of the resistor R8 is connected to the signal input end of the switching regulator chip U1, the base of the transistor Q2 is connected to one end of the resistor R10, the other end of the resistor R10 is respectively connected to the positive electrode of the capacitor C6, one end of the resistor R9, the first battery voltage end and the second battery voltage end, the negative electrode of the capacitor C6, the other end of the resistor R9, and the emitter of the transistor Q2 are connected to the system ground.

[0010] Preferably, it also includes a resistor R1 and a light emitting diode LED1;

[0011] One end of the resistor R1 is connected to the output port of the charger, the other end of the resistor R1 is connected to one end of the light emitting diode LED1, and the other end of the LED1 is connected to the system ground.

[0012] Furthermore, it also includes a fuse F1, a voltage regulator D1, and a thyristor Q1;

[0013] One end of the fuse F1 is connected to the output port of the charger, and the other end of the fuse F1 is respectively connected to the negative electrode of the voltage regulator D1, the anode of the thyristor Q1 and the signal input end of the switching regulator chip U1, the positive electrode of the voltage regulator D1 and the control electrode of the thyristor Q1 are connected through the resistor R3, the positive electrode of the voltage regulator D1 is connected to one end of the resistor R2, and the other end of the resistor R2 and the cathode of the thyristor Q1 are connected to the system ground.

[0014] Preferably, it also includes capacitor C1, capacitor C2 and capacitor C3;

[0015] The positive electrode of the capacitor C1, one end of the capacitor C2, and one end of the capacitor C3 are all connected to the other end of the fuse F1, the positive electrode of the capacitor C1, one end of the capacitor C2, and one end of the capacitor C3 are all connected to the signal input end of the switching regulator chip U1, and the negative electrode of the capacitor C1, the other end of the capacitor C2, and the other end of the capacitor C3 are connected to the system ground.

[0016] Preferably, the heat dissipation terminal and the grounding terminal of the switching regulator chip U1 are both connected to the system ground.

[0017] Preferably, it also includes a common anode blue-green dual-color lamp LED2, a resistor R4 and a resistor R5;

[0018] The common anode end of the common anode blue-green bicolor light LED2 is connected to the voltage output end, the green end of the common anode blue-green bicolor light LED2 is connected to one end of the resistor R5, the blue end of the common anode blue-green bicolor light LED2 is connected to one end of the resistor R4, the other end of the resistor R5 is connected to the charging end indication port, and the other end of the resistor R4 is connected to the charging status indication port.

[0019] Preferably, the charger has five output ports, one of which is a voltage output port, and the others are ground ports. The voltage output port is connected to the signal input terminal of the switching regulator chip U1.

[0020] Preferably, the model of the switching regulator chip U1 is LM2596S-ADJ.

[0021] A battery charging circuit, based on any of the above-mentioned buck DC / DC switching power supply circuits with protection function, comprising an anti-reverse connection diode D3, a charging chip U2, a PMOS tube Q3, a freewheeling diode D6, a power inductor L2, an output filter capacitor C10 and an output filter capacitor C11;

[0022] One end of the anti-reverse connection diode D3 is connected to the voltage output end, and the other end of the anti-reverse connection diode D3 is connected to one end of the input filter capacitor C7, one end of the input filter capacitor C8, one end of the capacitor C9, the positive input end of the external power supply of the charging chip U2, and the source of the PMOS tube Q3 through the fuse F2, and the other end of the capacitor C9 is connected to the internal voltage modulator output end of the charging chip U2;

[0023] The gate of the PMOS tube Q3 is connected to the gate driving end of the charging chip U2, the drain of the PMOS tube Q3 is connected to the positive electrode of the blocking diode D5, the negative electrode of the blocking diode D5 is respectively connected to the negative electrode of the freewheeling diode D6 and one end of the power inductor L2, the other end of the power inductor L2 is respectively connected to one end of the resistor R13 and the charging current detection positive input end of the charging chip U2, the other end of the resistor R13 is connected to the positive electrode of the battery to be charged, and one end of the output filter capacitor C10 and one end of the output filter capacitor C11 are both connected to the positive electrode of the battery to be charged.

[0024] Preferably, the charging status indication terminal of the charging chip U2 is connected to the charging status indication port, and the charging end indication terminal of the charging chip U2 is connected to the charging end indication port.

[0025] Compared with the prior art, the utility model has the following beneficial technical effects:

[0026] The utility model is a step-down DC / DC switching power supply circuit with protection function, with the switching regulator chip U1 as the core, the freewheeling diode D2, the inductor L1 and the capacitor C5 having the voltage stabilization function, which can stabilize the voltage within a certain range. When the switch tube inside the switching regulator chip U1 is turned on, the output voltage charges the inductor L1 and the capacitor C5, and outputs the voltage at the same time; when the switch tube inside the switching regulator chip U1 is turned off, due to the self-inductance of the inductor L1, the magnetic field will generate voltage, converting the electromagnetic energy into electric energy, forming a loop through the capacitor C5 and the freewheeling diode D2, the capacitor C5 and the freewheeling diode D2 are powered at the same time, and the charging stability of the switching power supply circuit after being connected to the charging circuit is ensured in the later stage. After the resistor R6, the resistor R7 and the feedback end of the switching regulator chip U1 cooperate, the other end of the resistor R6 is connected to the voltage output end, and the output voltage of the voltage output end can be adjusted. When there is no charging object, the first battery voltage terminal is at a low level, the transistor Q2 is not turned on, the switch terminal of the switching regulator chip U1 is at a high level, and the switching regulator chip U1 has no output at this time, so no voltage is output when there is no charging object. When a charging object is inserted, the first battery voltage terminal is at a high level, the transistor Q2 is turned on, the switch terminal of the switching regulator chip U1 is at a low level, and the switching regulator chip U1 outputs a voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of a step-down DC / DC switching power supply circuit with a protection function of the utility model;

[0028] Figure 2 This is a schematic diagram of a battery charging circuit of the utility model.

[0029] Figure 3 This is a schematic diagram of the interface P3 described in the present utility model. DETAILED DESCRIPTION

[0030] In order to enable those skilled in the art to better understand the solution of the utility model, the technical solution in the embodiment of the utility model will be clearly and completely described below in conjunction with the drawings in the embodiment of the utility model. Obviously, the described embodiment is only a part of the embodiment of the utility model, not all of the embodiments. Based on the embodiment of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the utility model.

[0031] The utility model discloses a step-down DC / DC switching power supply circuit with protection function, such as Figure 1, with the LM2596S-ADJ switching regulator chip U1 as the core, the switching regulator has a signal input terminal (VIN, pin 1), a signal output terminal (OUT, pin 2), a ground terminal (GND, pin 3), a feedback terminal (FEED BACK, pin 4), a switch terminal (ON / OFF, pin 5), and a heat dissipation terminal (TAB). It also involves an input voltage and current limiting protection module, an input filtering module, an output voltage stabilization module, a charging indicator light module, an output voltage regulation module, and an output protection module.

[0032] The output port of the charger is used as the input interface P1. P1 has 5 ports, port 1 is the voltage input port, and ports 2 to 5 are ground ports. One end of the resistor R1 is connected to port 1, and the other end is connected to one end of the white light-emitting diode LED1. The other end of LED1 is connected to the system ground. When a charger is plugged in, LED1 lights up. Port 1 is also connected to one end of the fuse F1, and then connected to the negative electrode of the voltage regulator D1, the anode (pin 1) of the thyristor Q1, the positive electrode of the capacitor C1, one end of the capacitor C2, one end of the capacitor C3 and the pin 1 (VIN) of the switching regulator chip U1 through the fuse F1. The positive electrode of the voltage regulator D1 and the control electrode (pin 2) of the thyristor Q1 are connected together through the resistor R3. The positive electrode of the voltage regulator D1 is connected to one end of the resistor R2, and the other end of the resistor R2 is connected to the system ground. The positive electrode of capacitor C1, one end of capacitor C2, and one end of capacitor C3 are connected to pin 1 of switching regulator chip U1, and the negative electrode of capacitor C1, the other end of capacitor C2, the cathode (pin 3) of thyristor Q1, and the other end of capacitor C3 are connected to the system ground. Capacitor C1, capacitor C2, and capacitor C3 form an input filter module.

[0033] Fuse F1, voltage regulator D1, thyristor Q1, resistor R2, and resistor R3 form an input voltage-limiting and current-limiting protection module, which plays a role in voltage-limiting and current-limiting protection. The specific principle is: the rated current of fuse F1 is 600mA. When the current flowing through is greater than 600mA, fuse F1 melts and plays a role in current protection. When the input voltage is 12V, select voltage regulator D1 with a starting voltage of 13.1V. When the charger is inserted and the voltage fluctuates greater than 13.1V, voltage regulator D1 is turned on, thyristor Q1 is triggered and turned on, a short circuit occurs, and fuse F1 melts, which plays a role in voltage-limiting protection.

[0034] Pin 2 (OUT) of the switching regulator chip U1 is connected to the cathode of the freewheeling diode D2 and one end of the inductor L1, and then connected to one end of the capacitor C4, the anode of the capacitor C5, and the port 3 (voltage output end) of the output interface P2 through the inductor L1. The anode of the freewheeling diode D2, the other end of the capacitor C4, the cathode of the capacitor C5, pin 6 and pin 3 of the switching regulator chip U1, and the ports 2, 4, and 8 of the output interface P2 are connected to the system ground. The freewheeling diode D2, the inductor L1, and the capacitor C5 form an output voltage stabilization module. When the switch tube inside the switching regulator chip U1 is turned on, the output voltage charges the inductor L1 and the capacitor C5, and the output voltage is also given to the back-end charging circuit; when the switch tube inside the switching regulator chip U1 is turned off, due to the self-inductance of the inductor L1, the magnetic field will generate voltage, converting the electromagnetic energy into electrical energy, and forming a loop through the capacitor C5 and the freewheeling diode D2. The capacitor C5 and the freewheeling diode D2 simultaneously provide input voltage to the back-end charging circuit.

[0035] Pin 4 (FEEDBACK) of the switching regulator chip U1 is connected to one end of resistor R6 and one end of resistor R7, the other end of resistor R6 is connected to port 3 of output interface P2, and the other end of resistor R7 is connected to system ground. Pin 1 (common anode) of LED2 is connected to port 3 of output interface P2, pin 2 (green end) of LED2 is connected to one end of resistor R5, pin 3 (blue end) of LED2 is connected to one end of resistor R4, the other end of resistor R5 is connected to port 6 of output interface P2, and the other end of resistor R4 is connected to port 5 of output interface P2. The common anode blue-green bicolor light LED2, resistor R4, and resistor R5 form a charging indicator light module. When a charging object is connected, port 5 of P2 (connected through interface P3) Figure 2 Pin 3 of the charging chip U2 is low level, port 6 (connected through interface P3) Figure 2 When the pin 4 of the charging chip U2 is high, the LED light emits blue light; when fully charged, the port 5 of P2 is high, the port 6 is low, and the LED light emits green light. Resistors R6 and R7 form an output voltage adjustment module, and the adjustable output voltage is V out =1.23×(1+R6 / R7).

[0036] Pin 5 (ON / OFF) of the switching regulator chip U1 is connected to one end of the resistor R8 and the collector (pin 3) of the transistor Q2, and the other end of the resistor R8 is connected to pin 1 (VIN) of the switching regulator chip U1. The base (pin 1) of the transistor Q2 is connected to one end of the resistor R10, and the other end of the resistor R10 is connected to the positive electrode of the capacitor C6, one end of the resistor R9, port 1 (first battery voltage end) and port 7 (second battery voltage end) of the output interface P2, and the negative electrode of the capacitor C6, the emitter (pin 2) of the transistor Q2, and the other end of the resistor R9 are connected to the system ground. Capacitor C6, resistor R9, resistor R10, transistor Q2 and resistor R8 form an output protection module. When there is no charging object, port 1 of the interface P2 is low level, transistor Q2 is not conducting, and pin 5 of the switching regulator chip U1 is high level. At this time, the switching regulator chip U1 has no output. When a charging object is inserted, port 1 of interface P2 is at a high level, transistor Q2 is turned on, pin 5 of switching regulator chip U1 is at a low level, and switching regulator chip U1 outputs a voltage (POWER+).

[0037] The above-mentioned step-down DC / DC switching power supply circuit can be used to charge a specific battery. The utility model provides a specific embodiment, which is a charging circuit for a single lithium battery, such as Figure 2 The output POWER+ (port 3 of output interface P2) / GND (port 2, port 4 and port 8 of output interface P2) of the step-down DC / DC switching power supply circuit is used as the input signal of the charging circuit. The input signal POWER+ passes through the anti-reverse connection diode D3 and the fuse F2 and then enters the charging chip U2 of model CN3761. The charging chip U2 independently manages the charging of a single lithium battery and has trickle current, constant current and constant voltage charging modes. It is a single-cell lithium battery charging management integrated circuit using PWM step-down mode, which is very suitable for lithium battery charging management.

[0038] The input signal POWER+ is connected to one end of the input filter capacitor C7, one end of the input filter capacitor C8, one end of the capacitor C9, pin 9 of the charging chip U2 (the positive input end of the external power supply), and the source (pin 2) of the PMOS tube Q3 after the anti-reverse connection diode D3 and the fuse F2. The other end of the capacitor C9 is connected to pin 1 (the output end of the internal voltage modulator) of the charging chip U2. The gate (pin 1) of the PMOS tube Q3 is connected to pin 10 (the gate drive end) of the charging chip U2. The drain (pin 3) of the PMOS tube Q3 is connected to the positive electrode of the blocking diode D5. The negative electrode of the blocking diode D5 is connected to the negative electrode of the freewheeling diode D6 and one end of the power inductor L2. The blocking diode D5 can block the current coming from the battery end. The positive electrode of the freewheeling diode D6 is grounded. The other end of the power inductor L2 is connected to one end of the resistor R13 and pin 8 (the positive input end of the charging current detection) of the charging chip U2. The other end of the resistor R13 is connected to the positive electrode of the battery (pin 2, i.e., V bat ), the resistor R13 plays the role of maintaining the constant current charging current, the constant current charging current = 120mV / R13, the output filter capacitor C10 / C11 is connected to the positive electrode of the battery at one end and to GND at the other end.

[0039] Pin 5 (loop compensation input terminal) of the charging chip U2 is connected to GND through resistor R14 and capacitor C12, pin 2 of the charging chip U2 is connected to GND, pin 6 (battery voltage detection input terminal) and pin 7 (battery positive connection terminal and charging current detection negative input terminal) of the charging chip U2 are connected to the positive electrode (pin 2) of the battery, and the negative electrode of the battery is connected to GND. Pin 3 (charging status indication terminal) of the charging chip U2 and Figure 3 The port 5 of the interface P3 shown in the figure is connected, the pin 4 of the charging chip U2 (charging end indication terminal) is connected to the port 6 of the interface P3, the number of interfaces and the corresponding functions of the interface P3 are the same as those of the output interface P2, the output interface P2 and the interface P3 can be male and female plugs to each other, and the connection port on P3 is connected to Figure 1 The corresponding ports of P2 in the figure are connected, and the port 1 (first battery voltage terminal) and port 7 (second battery voltage terminal) on P3 are connected to Figure 2 V bat connect.

[0040] In the charging state, pin 3 of the charging chip U2 is at a low level and pin 4 is at a high level. After the charging state is completed, pin 3 is at a high level and pin 4 is at a low level. The PMOS tube Q3, the freewheeling diode D6, the power inductor L2 and the charging chip U2 realize the conversion of the input voltage to the battery charging voltage.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the utility model rather than to limit it. Although the utility model is described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that any modification or equivalent substitution that does not depart from the spirit and scope of the utility model should be included in the scope of protection of the claims of the utility model.

Claims

1. A step-down DC / DC switching power supply circuit with protection function, characterized in that: It includes a switching regulator chip U1, a freewheeling diode D2, an inductor L1, a capacitor C5 and a transistor Q2; The signal input end of the switching regulator chip U1 is connected to the output port of the charger, the signal output end of the switching regulator chip U1 is respectively connected to the cathode of the freewheeling diode D2 and one end of the inductor L1, the other end of the inductor L1 is respectively connected to one end of the capacitor C4, the anode of the capacitor C5 and the voltage output end, the anode of the freewheeling diode D2, the other end of the capacitor C4 and the cathode of the capacitor C5 are connected to the system ground; The feedback end of the switching regulator chip U1 is connected to one end of the resistor R6 and one end of the resistor R7 respectively, the other end of the resistor R6 is connected to the voltage output end, and the other end of the resistor R7 is connected to the system ground; The switch end of the switching regulator chip U1 is respectively connected to one end of the resistor R8 and the collector of the transistor Q2, the other end of the resistor R8 is connected to the signal input end of the switching regulator chip U1, the base of the transistor Q2 is connected to one end of the resistor R10, the other end of the resistor R10 is respectively connected to the positive electrode of the capacitor C6, one end of the resistor R9, the first battery voltage end and the second battery voltage end, the negative electrode of the capacitor C6, the other end of the resistor R9, and the emitter of the transistor Q2 are connected to the system ground.

2. The step-down DC / DC switching power supply circuit with protection function according to claim 1, characterized in that: It also includes a resistor R1 and a light emitting diode LED1; One end of the resistor R1 is connected to the output port of the charger, the other end of the resistor R1 is connected to one end of the light emitting diode LED1, and the other end of the LED1 is connected to the system ground.

3. The step-down DC / DC switching power supply circuit with protection function according to claim 2, characterized in that: It also includes fuse F1, voltage regulator D1, and thyristor Q1; One end of the fuse F1 is connected to the output port of the charger, and the other end of the fuse F1 is respectively connected to the negative electrode of the voltage regulator D1, the anode of the thyristor Q1 and the signal input end of the switching regulator chip U1, the positive electrode of the voltage regulator D1 and the control electrode of the thyristor Q1 are connected through the resistor R3, the positive electrode of the voltage regulator D1 is connected to one end of the resistor R2, and the other end of the resistor R2 and the cathode of the thyristor Q1 are connected to the system ground.

4. The step-down DC / DC switching power supply circuit with protection function according to claim 2, characterized in that: Also includes capacitor C1, capacitor C2 and capacitor C3; The positive electrode of the capacitor C1, one end of the capacitor C2, and one end of the capacitor C3 are all connected to the other end of the fuse F1, the positive electrode of the capacitor C1, one end of the capacitor C2, and one end of the capacitor C3 are all connected to the signal input end of the switching regulator chip U1, and the negative electrode of the capacitor C1, the other end of the capacitor C2, and the other end of the capacitor C3 are connected to the system ground.

5. The step-down DC / DC switching power supply circuit with protection function according to claim 1, characterized in that: The heat dissipation end and the grounding end of the switching regulator chip U1 are both connected to the system ground.

6. The step-down DC / DC switching power supply circuit with protection function according to claim 1, characterized in that: It also includes a common anode blue-green bicolor lamp LED2, a resistor R4 and a resistor R5; The common anode end of the common anode blue-green bicolor light LED2 is connected to the voltage output end, the green end of the common anode blue-green bicolor light LED2 is connected to one end of the resistor R5, the blue end of the common anode blue-green bicolor light LED2 is connected to one end of the resistor R4, the other end of the resistor R5 is connected to the charging end indication port, and the other end of the resistor R4 is connected to the charging status indication port.

7. The step-down DC / DC switching power supply circuit with protection function according to claim 1, characterized in that: The charger has five output ports, one of which is a voltage output port, and the others are ground ports. The voltage output port is connected to the signal input terminal of the switching regulator chip U1.

8. The step-down DC / DC switching power supply circuit with protection function according to claim 1, characterized in that: The model of the switching regulator chip U1 is LM2596S-ADJ.

9. A battery charging circuit, characterized in that: A step-down DC / DC switching power supply circuit with protection function according to any one of claims 1 to 8, comprising an anti-reverse connection diode D3, a charging chip U2, a PMOS tube Q3, a freewheeling diode D6, a power inductor L2, an output filter capacitor C10 and an output filter capacitor C11; One end of the anti-reverse connection diode D3 is connected to the voltage output end, and the other end of the anti-reverse connection diode D3 is connected to one end of the input filter capacitor C7, one end of the input filter capacitor C8, one end of the capacitor C9, the positive input end of the external power supply of the charging chip U2, and the source of the PMOS tube Q3 through the fuse F2, and the other end of the capacitor C9 is connected to the internal voltage modulator output end of the charging chip U2; The gate of the PMOS tube Q3 is connected to the gate driving end of the charging chip U2, the drain of the PMOS tube Q3 is connected to the positive electrode of the blocking diode D5, the negative electrode of the blocking diode D5 is respectively connected to the negative electrode of the freewheeling diode D6 and one end of the power inductor L2, the other end of the power inductor L2 is respectively connected to one end of the resistor R13 and the charging current detection positive input end of the charging chip U2, the other end of the resistor R13 is connected to the positive electrode of the battery to be charged, and one end of the output filter capacitor C10 and one end of the output filter capacitor C11 are both connected to the positive electrode of the battery to be charged.

10. The battery charging circuit according to claim 9, characterized in that: The charging state indication terminal of the charging chip U2 is connected to the charging state indication port, and the charging end indication terminal of the charging chip U2 is connected to the charging end indication port.

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