CN102810899B - Charging circuit with short circuit protecting function and charger - Google Patents

Abstract

A charging circuit with short-circuit protection includes a charging module, a short-circuit protection module and an anti-reverse diode, the short-circuit protection module includes a first operational amplifier, a first protection diode and a second protection diode, and the inverting input of the first operational amplifier The terminal is connected to the positive pole of the first protection diode, the output terminal is connected to the positive pole of the second protection diode, the negative pole of the first protection diode is connected to the output terminal of the charging circuit, and the negative pole of the second protection diode is connected to the input terminal of the control circuit. When the output end of the circuit is short-circuited, the voltage at the inverting input end of the first operational amplifier is pulled down through the first protective diode, so that the output end of the first operational amplifier outputs a high level, and the control circuit outputs under the action of the high level Low level, the switch circuit is cut off through low level control. The short-circuit protection function can be realized by adopting the charging circuit, which is simple and reliable, and saves circuit cost. In addition, a charger of the charging circuit is also provided.

Description

Charging circuit with short circuit protection, charger

【Technical field】

The invention relates to a charging circuit, in particular to a charging circuit with short circuit protection and a charger.

【Background technique】

The output terminals of traditional chargers usually do not have a short-circuit protection function. When the output terminals are accidentally short-circuited, the charging circuit will be damaged, and such damaged chargers are usually irreparable. There is also an application-specific integrated circuit (IC) to perform short-circuit protection on the output terminal of the charger, but the circuit is complicated and the cost is high.

【Content of invention】

Based on this, it is necessary to provide a simple, reliable and cost-saving charging circuit with short-circuit protection.

A charging circuit with short circuit protection, including a charging module, a short circuit protection module and an anti-reverse diode, the charging module includes a transformer rectification circuit, a control circuit, a switch circuit, a constant current circuit and a sampling circuit, the input of the control circuit The terminal is connected to the output terminal of the transformer rectification circuit, the sampling circuit and the short circuit protection module, the output terminal is connected to the input terminal of the switching circuit, and the control circuit controls the switching circuit according to the sampling voltage of the sampling circuit. On and off, the output end of the switch circuit is connected to the output end of the constant current circuit, the output end of the constant current circuit is connected to the rechargeable battery through the anti-reverse diode, and the short circuit protection module includes a first An operational amplifier, a first protection diode and a second protection diode, the inverting input terminal of the first operational amplifier is connected to the anode of the first protection diode, the output terminal is connected to the anode of the second protection diode, and the first protection diode The negative pole of the charging circuit is connected to the output terminal of the charging circuit, the negative pole of the second protection diode is connected to the input terminal of the control circuit, when the output terminal of the charging circuit is short-circuited, the voltage at the inverting input terminal of the first operational amplifier The first protection diode is pulled low, so that the output terminal of the first operational amplifier outputs a high level, and the control circuit outputs a low level under the action of the high level, and is controlled by the low level The switching circuit is turned off.

Preferably, the short circuit protection module further includes a first voltage dividing resistor, a second voltage dividing resistor and a third voltage dividing resistor, the non-inverting input terminal of the first operational amplifier is grounded through the first voltage dividing resistor, and is connected to the ground through the first voltage dividing resistor. The second voltage dividing resistor is connected to the output terminal of the transformer rectifying circuit, and the inverting input terminal of the first operational amplifier is connected to the output terminal of the transformer rectifying circuit through the third voltage dividing resistor.

Preferably, the control circuit includes a protection resistor, a voltage regulator tube, a first adjustable resistor and a second operational amplifier, one end of the protection resistor is connected to the output end of the transformer rectification circuit, and the other end is The pressure tube is grounded, the first adjustable resistor is connected in parallel with the voltage regulator tube, the non-inverting input terminal of the second operational amplifier is connected to the adjustment terminal of the first adjustable resistor, and the inverting input terminal is connected to the first adjustable resistor The cathodes of the two protection diodes are connected, and the output terminals are connected with the input terminals of the switching circuit.

Preferably, the control circuit further includes a first energy storage capacitor and a filter capacitor, one end of the first energy storage capacitor is connected to the output end of the transformer rectification circuit, and the other end is grounded, and the filter capacitor is connected to the first energy storage capacitor Capacitors can be connected in parallel.

Preferably, the switch circuit includes a first triode and a bias resistor, the emitter of the first triode is grounded, the base is connected to the output terminal of the control circuit, and the collector is connected to the constant current circuit The input terminal of the second triode is connected to the ground through the bias resistor.

Preferably, the constant current circuit includes a second triode and a second adjustable resistor, the base of the second triode is connected to the collector of the first triode, and the emitter passes through the first triode The two adjustable resistors are connected to the output end of the transformer rectification circuit, and the collector is connected to the rechargeable battery through the anti-reverse diode.

Preferably, the constant current circuit further includes a light-emitting diode, the anode of the light-emitting diode is connected to the output terminal of the transformation and rectification circuit, and the cathode is connected to the base of the second triode, and the light-emitting diode is Lights on when the light-on circuit is turned on, and turns off when the switch circuit is turned off.

Preferably, the sampling circuit includes a second energy storage capacitor, a sampling resistor, a fourth voltage dividing resistor and an adjusting diode, one end of the sampling resistor is grounded, and the other end is connected in series with the fourth voltage dividing resistor to the second The collector of the triode is connected, and the connection between the sampling resistor and the fourth voltage dividing resistor is connected to the inverting input terminal of the operational amplifier through an adjusting diode, and the second energy storage capacitor is connected to the sampling resistor. , and the fourth voltage dividing resistors are connected in parallel.

Preferably, the transformer and rectifier circuit includes a transformer and a rectifier, the primary coil of the transformer is connected to the mains, the secondary coil is connected to the input end of the rectifier, one end of the output end of the rectifier is grounded, and the charging circuit An isolation diode is also included, the anode of the isolation diode is connected to the direct current, and the cathode is connected to the other end of the output terminal of the rectifier.

In addition, it is necessary to provide a charger including the above-mentioned charging circuit with short-circuit protection.

The charging circuit and charger with short-circuit protection mentioned above, when the output terminal of the charger is short-circuited, the voltage of the inverting input terminal of the first operational amplifier is pulled down through the first protection diode in the short-circuit protection module, and the first operation The voltage of the non-inverting input terminal of the amplifier is greater than the voltage of the inverting input terminal, the first operational amplifier outputs a high level, and under the effect of the high level, the control circuit outputs a low level, thereby controlling the switch circuit to be cut off, and the charger stops charging. Therefore, the charger can be effectively protected when the output end of the charger is accidentally short-circuited, the implementation is simple and reliable, and the circuit cost can be effectively saved.

【Description of drawings】

FIG. 1 is a schematic structural view of a charging circuit with short-circuit protection provided in Embodiment 1;

Fig. 2 is a schematic structural diagram of a charging circuit with short-circuit protection provided in Embodiment 2.

【Detailed ways】

The charging circuit with short-circuit protection provided by the present invention includes a charging module, a short-circuit protection module and an anti-reverse diode. The charging module includes a transformer rectifying circuit, a control circuit, a switch circuit, a constant current circuit and a sampling circuit. The input terminal of the control circuit is connected to the The output end of the transformer rectification circuit is connected with the sampling circuit and the short-circuit protection module, the output end is connected with the input end of the switch circuit, the control circuit controls the conduction and cut-off of the switch circuit according to the sampling voltage of the sampling circuit, the output end of the switch circuit is connected with the constant The output terminal of the current circuit is connected, the output terminal of the constant current circuit is connected with the rechargeable battery through the anti-reverse diode, the short circuit protection module includes the first operational amplifier, the first protection diode and the second protection diode, the inverting input terminal of the first operational amplifier It is connected to the anode of the first protection diode, the output end is connected to the anode of the second protection diode, the cathode of the first protection diode is connected to the output end of the charging circuit, the cathode of the second protection diode is connected to the input end of the control circuit, and the charging circuit When the output terminal of the first operational amplifier is short-circuited, the voltage of the inverting input terminal of the first operational amplifier is pulled down through the first protection diode, so that the output terminal of the first operational amplifier outputs a high level, and the control circuit outputs a low level under the action of the high level , the switch circuit is cut off by controlling the low level.

Embodiment one

As shown in Figure 1, the charging circuit with short circuit protection includes a charging module 10, a short circuit protection module 20 and an anti-reverse diode 30, wherein: the charging module 10 includes a transformer rectifying circuit 11, a control circuit 12, a switch circuit 13, a constant current circuit 14 and sampling circuit 15, wherein:

The input terminal of the transformer rectifier circuit 11 is connected with the mains, the input terminal of the control circuit 12 is connected with the output terminal of the transformer rectifier circuit 11, the sampling circuit 15 and the short circuit protection module 20, and the output terminal of the control circuit 12 is connected with the switch circuit 13. The input terminal is connected, the output terminal of the switch circuit 13 is connected with the input terminal of the constant current circuit 14 , and the output terminal of the constant current circuit 14 is connected with the rechargeable battery through the anti-reverse diode 30 . The control circuit 12 controls the on and off of the switch circuit 13 according to the sampling voltage of the sampling circuit 15. When the switch circuit 13 is on, the charging circuit charges the rechargeable battery, and when the switch circuit 13 is off, the charging circuit stops charging the rechargeable battery. , The anti-reverse diode 30 can prevent the rechargeable battery from discharging to the charging circuit when the power supply is cut off after the charging is completed.

The short-circuit protection module 20 includes a first operational amplifier OP1, a first protective diode D6 and a second protective diode D7, the inverting input terminal of the first operational amplifier OP1 is connected to the anode of the first protective diode D6, and the output terminal is connected to the anode of the second protective diode D6. The anode of D7 is connected, the cathode of the first protection diode D6 is connected with the output terminal of the charging circuit (ie, the input terminal of the rechargeable battery), and the cathode of the second protection diode D7 is connected with the input terminal of the control circuit 12 . When the output terminal of the charging circuit is short-circuited, the voltage Vp of the inverting input terminal of the first operational amplifier OP1 is pulled down through the first protective diode D6, so that the voltage Vk of the non-inverting input terminal of the first operational amplifier OP1 is greater than the voltage Vp of the inverting input terminal of the first operational amplifier OP1, and the second The output terminal of an operational amplifier OP1 outputs a high level, and the control circuit 12 outputs a low level under the action of the high level, and the switching circuit 13 is controlled by the low level to cut off, and the charging circuit stops charging, thereby realizing the short circuit protection function.

Because the short-circuit protection module 20 makes the short-circuit protection module 20 output a low level by pulling down the inverting input terminal voltage Vp of the first operational amplifier OP1, the control module 12 controls the switch circuit 13 to cut off under the high-level input, and the circuit realizes It is simple and reliable, can save circuit cost, and has fast response speed.

In other embodiments, the input end of the control circuit 12 can also be connected to a direct current, such as a vehicle-mounted 12V power supply, so that the rechargeable battery can be charged through the mains or the vehicle-mounted power supply, which is more convenient to use.

Embodiment two

As shown in Figure 2, the charging circuit with short-circuit protection includes a charging module 10, a short-circuit protection module 20 and an anti-reverse diode D2. 14 and sampling circuit 15. in:

The transformer rectification circuit 11 includes a transformer T1 and a rectifier D3, the primary coil of the transformer T1 is connected to the mains, the secondary coil is connected to the input terminals 1 and 3 of the rectifier D3, the output terminal 4 of the rectifier D3 is grounded, and the transformer T1 connects the 220V mains Converted to low voltage, the AC is converted to DC by the rectifier D3. The charging circuit also includes an isolation diode D1. The anode of the isolation diode D1 is connected to the DC power, and the cathode is connected to the output terminal 2 of the rectifier D3. The isolation diode D1 is used to isolate the mutual influence of the AC power and the DC power supply. The charging circuit provided in this embodiment can not only charge the rechargeable battery BT through 220V AC power, but also can charge the rechargeable battery BT through a DC power supply (such as a vehicle-mounted 12V power supply).

As shown in FIG. 2 , the control circuit 12 includes a protection resistor R1, a regulator tube D4, a first adjustable resistor Rw1 and a second operational amplifier OP2. One end of the protection resistor R1 is connected to the output terminal 2 of the rectifier D3, and the other end is connected through a regulator D3 The pressure tube D4 is grounded, and the first adjustable resistor Rw1 is connected in parallel with the voltage regulator tube D4. In this embodiment, a resistor R2 connected in series with the first adjustable resistor Rw1 may also be set. The non-inverting input terminal of the second operational amplifier OP2 is connected to the adjustment terminal of the first adjustable resistor Rw1, the inverting input terminal is connected to the sampling circuit 15 and the short circuit protection module 20, and the output terminal is connected to the input terminal of the switch circuit 13 through the resistor R3.

In this embodiment, the control circuit 12 also includes a first energy storage capacitor C1 and a filter capacitor C3. One end of the first energy storage capacitor C1 is connected to the output terminal 2 of the rectifier D3, and the other end is grounded. The filter capacitor C3 is connected to the first energy storage capacitor C3. Capacitor C1 is connected in parallel.

The switch circuit 13 includes a first triode Q1 and a bias resistor R4, the emitter of the first triode Q1 is grounded, the base is connected to the resistor R3, the collector is connected to the input terminal of the constant current circuit 14, and the first triode The base of the tube Q1 is also grounded through the bias resistor R4.

The constant current circuit 14 includes a second transistor Q2 and a second adjustable resistor Rw2, the base of the second transistor Q2 is connected to the collector of the first transistor Q1 through a resistor R5, and the emitter is connected to the first transistor Q1 through a resistor R6. The two adjustable resistors Rw2 are connected in series, and are connected to the output terminal 2 of the rectifier D3 through the second adjustable resistor Rw2, and the collector of the second triode Q2 is connected to the rechargeable battery BT through the anti-reverse diode D2. In this embodiment, the constant current circuit 14 also includes a light emitting diode D5, the positive pole of the light emitting diode D5 is connected to the output terminal 2 of the rectifier D3, and the negative pole is connected to the base of the second triode Q2. It lights up when it is on, and goes out when the switch circuit 13 is off.

The sampling circuit 15 includes a second energy storage capacitor C2, a sampling resistor R7, a fourth voltage dividing resistor R8 and an adjusting diode D8. One end of the sampling resistor R7 is grounded, and the other end is connected in series with the fourth voltage dividing resistor R8 to connect with the second triode Q2 The collector of the sampling resistor R7 and the fourth voltage dividing resistor R8 are connected to the inverting input terminal of the second operational amplifier OP2 through the regulating diode D8, that is, the sampling voltage of the sampling circuit 15 is stepped down by the regulating diode D8 as Voltage at the inverting input of the second operational amplifier OP2. The second energy storage capacitor C2 is connected in parallel with the sampling resistor R7 and the fourth voltage dividing resistor R8.

The short circuit protection module 20 includes a first operational amplifier OP1, a first protection diode D6, a second protection diode D7, a first voltage dividing resistor R11, a second voltage dividing resistor R10 and a third voltage dividing resistor R9, the first operational amplifier OP1 The non-inverting input terminal is grounded through the first voltage dividing resistor R11, and connected to the output terminal 2 of the rectifier D3 through the second voltage dividing resistor R10, and the inverting input terminal of the first operational amplifier OP1 is connected to the output terminal of the rectifier D3 through the third voltage dividing resistor R9. The output terminal 2 is connected, the inverting input terminal of the first operational amplifier OP1 is also connected with the anode of the first protection diode D6, the negative pole of the first protection diode D6 is connected with the output terminal of the charging circuit, and the output terminal of the first operational amplifier OP1 is connected with the output terminal of the charging circuit. The anode of the second protection diode D7 is connected, and the cathode of the second protection diode D7 is connected to the inverting input terminal of the second operational amplifier OP2.

The charging circuit provided in this embodiment can automatically cut off the charging after it is fully charged, the principle is as follows:

According to the charging circuit provided in this embodiment, the charging voltage is set as VB=VR*(R7+R8)/R7-VD2, and the charging current is set as IQ2c=(VD5-VQ2be)/(Rw2+R6). By adjusting the first adjustable resistor Rw1, during charging, the voltage VR of the non-inverting input terminal of the second operational amplifier OP2 is higher than the voltage of the inverting input terminal (that is, the sampling voltage of the sampling circuit 15 is stepped down by the regulating diode D8), In this way, when charging, the output terminal of the second operational amplifier OP2 outputs a high level, so that the first triode Q1 is turned on, and then the rechargeable battery BT is charged after passing through the constant current circuit 14, and the light-emitting diode D5 lights up at this time. By setting the first voltage dividing resistor R11, the second voltage dividing resistor R10 and the third voltage dividing resistor R9, the voltage Vk of the non-inverting input terminal of the first operational amplifier OP1 is smaller than the voltage Vp of the inverting input terminal of the first operational amplifier OP1. For example, Vk can be set to 2-3V, and Vp can be set to 4-5.5V. In this way, the first operational amplifier OP1 outputs a low level, and the normal operation of the charging circuit will not be affected due to the existence of the second protection diode D7. When the rechargeable battery BT is charged to the set charging voltage VB, the voltage VR of the non-inverting input terminal of the second operational amplifier OP2 is lower than the voltage of the inverting input terminal, and the output terminal of the second operational amplifier OP2 outputs a low level to control the first three The pole tube Q1 is cut off, and the charging circuit stops charging the rechargeable battery BT, so as to realize the automatic cut-off function when fully charged. Since the first triode Q1 is turned off at this time, the light emitting diode D5 is turned off.

The charging circuit provided in this embodiment can realize the short-circuit protection function, and the principle is as follows:

When the output terminal of the charging circuit is short-circuited, the voltage Vp of the inverting input terminal of the first operational amplifier OP1 is rapidly pulled down by the first protection diode D6, and is smaller than the voltage Vk of the non-inverting input terminal. For example, the voltage Vp is quickly pulled down to about 1V by the first protection diode D6, and Vk is set at 2-3V, so the voltage Vp of the inverting input terminal of the first operational amplifier OP1 is lower than the voltage Vk of the non-inverting input terminal of the first operational amplifier OP1. Then output high level. After passing through the second protection diode D7, the voltage of the inverting input terminal of the second operational amplifier OP2 is greater than the voltage Vp of the non-inverting input terminal, and the second operational amplifier OP2 then outputs a low level to control the first triode Q1 to cut off (equivalent to the first The collector of the first triode Q1 is suspended), so the second triode Q2 is also cut off, the constant current circuit 14 cannot work, and the charging circuit is automatically cut off, thereby realizing the short circuit protection function. Since the first triode Q1 is cut off at this time, the light emitting diode D5 is turned off. When the short circuit is eliminated, the voltage Vp of the inverting input terminal of the first operational amplifier OP1 quickly recovers to the voltage when the charging circuit is working, which is higher than the voltage Vk of the non-inverting input terminal, and the first operational amplifier OP1 outputs a low level, making the second operation The voltage of the inverting input terminal of the amplifier OP2 is lower than the voltage VR of its non-inverting input terminal, and the second operational amplifier OP2 outputs a high level, so that the first triode Q1 is turned on, the light-emitting diode D5 lights up, and the constant current circuit 14 works normally. , so the charging circuit automatically resumes charging.

In another embodiment, a charger including the above charging circuit with short circuit protection is also provided.

In the above-mentioned charging circuit and charger with short-circuit protection, when the output end of the charger is short-circuited, the voltage Vp of the inverting input end of the first operational amplifier OP1 is pulled down through the first protection diode D6 in the short-circuit protection module 20, The first operational amplifier OP1 outputs a high level, and under the action of the high level, the second operational amplifier OP2 outputs a low level to control the first triode Q1 to be cut off, and the second triode Q2 to be cut off as well. The flow circuit 14 cannot work normally, and the charger stops charging. Therefore, the charger can be effectively protected when the output terminal of the charger is accidentally short-circuited. The charging circuit with short-circuit protection mentioned above is implemented by a simple short-circuit protection circuit 20 , which is simple and reliable, has a fast response speed, and can effectively save circuit costs. Since the charger can be effectively protected when the output end of the charger is short-circuited, the charger will not be damaged due to the short circuit, the service life of the charger is prolonged, and maintenance costs are saved.

The above-mentioned embodiments only express several implementation modes of the present invention, and the description thereof is relatively specific and detailed, but should not be construed as limiting the patent scope of the present invention. It should be pointed out that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent for the present invention should be based on the appended claims.

Claims (8)

1. A charging circuit with short-circuit protection, characterized in that it includes a charging module, a short-circuit protection module and an anti-reverse diode, and the charging module includes a transformer rectifying circuit, a control circuit, a switch circuit, a constant current circuit and a sampling circuit, The input end of the control circuit is connected to the output end of the transformer rectification circuit, the sampling circuit and the short circuit protection module, the output end is connected to the input end of the switching circuit, and the control circuit is connected to the sampling voltage of the sampling circuit Controlling the on and off of the switch circuit, when the switch circuit is on, the charging circuit charges the rechargeable battery, and when the switch circuit is off, the charging circuit stops charging the rechargeable battery, thereby realizing Automatic cut-off function when fully charged; the output end of the switch circuit is connected to the output end of the constant current circuit, the output end of the constant current circuit is connected to the rechargeable battery through the anti-reverse diode, and the short circuit protection module includes The first operational amplifier, the first protection diode and the second protection diode, the inverting input terminal of the first operational amplifier is connected to the anode of the first protection diode, the output terminal is connected to the anode of the second protection diode, the first The cathode of the protection diode is connected to the output terminal of the charging circuit, the cathode of the second protection diode is connected to the input terminal of the control circuit, when the output terminal of the charging circuit is short-circuited, the inverting input of the first operational amplifier The terminal voltage is pulled low by the first protection diode, so that the output terminal of the first operational amplifier outputs a high level, and the control circuit outputs a low level under the action of the high level, and the low level is passed through the low level Level control the switch circuit cut-off; the control circuit includes a protection resistor, a voltage regulator tube, a first adjustable resistor and a second operational amplifier, one end of the protection resistor is connected to the output end of the transformer rectifier circuit, and the other One end is grounded through the voltage regulator tube, the first adjustable resistor is connected in parallel with the voltage regulator tube, the non-inverting input terminal of the second operational amplifier is connected with the adjustment terminal of the first adjustable resistor, and the reverse input The terminal is connected to the cathode of the second protection diode, and the output terminal is connected to the input terminal of the switch circuit. 2. The charging circuit with short-circuit protection according to claim 1, wherein the short-circuit protection module further comprises a first voltage dividing resistor, a second voltage dividing resistor and a third voltage dividing resistor, and the first calculation The non-inverting input terminal of the amplifier is grounded through the first voltage dividing resistor, and is connected to the output terminal of the transformer rectification circuit through the second voltage dividing resistor, and the inverting input terminal of the first operational amplifier is connected through the said second voltage dividing resistor. The third voltage dividing resistor is connected with the output end of the voltage transformation and rectification circuit. 3. The charging circuit with short-circuit protection according to claim 2, wherein the control circuit also includes a first energy storage capacitor and a filter capacitor, and one end of the first energy storage capacitor is connected to the output of the transformer rectifier circuit The other end is connected to the ground, and the filter capacitor is connected in parallel with the first energy storage capacitor. 4. The charging circuit with short-circuit protection according to any one of claims 1 to 3, wherein the switch circuit comprises a first triode and a bias resistor, and the emitter of the first triode The pole is grounded, the base is connected to the output terminal of the control circuit, the collector is connected to the input terminal of the constant current circuit, and the base of the first triode is also grounded through the bias resistor. 5. The charging circuit with short-circuit protection according to claim 4, wherein the constant current circuit comprises a second triode and a second adjustable resistor, the base of the second triode is connected to the The collector of the first triode is connected, the emitter is connected with the output terminal of the transformer rectification circuit through the second adjustable resistor, and the collector is connected with the rechargeable battery through the anti-reverse diode. 6. The charging circuit with short-circuit protection according to claim 5, wherein the constant current circuit further comprises a light-emitting diode, the anode of the light-emitting diode is connected to the output terminal of the transformer rectifier circuit, and the negative pole is connected to the output terminal of the transformer rectification circuit. The bases of the second triode are connected, and the light-emitting diode is turned on when the switch circuit is turned on, and is turned off when the switch circuit is turned off. 7. The charging circuit with short-circuit protection according to claim 1, wherein the transformer rectifier circuit comprises a transformer and a rectifier, the primary coil of the transformer is connected to the mains, and the secondary coil is connected to the rectifier. The input ends are connected, one end of the output end of the rectifier is grounded, and the charging circuit further includes an isolation diode, the anode of the isolation diode is connected to direct current, and the cathode is connected to the other end of the output end of the rectifier. 8. A charger, characterized in that it comprises the charging circuit with short-circuit protection according to any one of claims 1-7.