CN102810897B - Charging circuit with short-circuit protection and charger - Google Patents

Abstract

A charging circuit with short-circuit protection, including a charging module, a protection diode and an anti-reverse diode, the charging module includes a transformer rectifier 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 transformer rectifier circuit The output end of the circuit is connected with the sampling circuit, 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 input end of the constant current circuit, The output terminal of the constant current circuit is connected to the rechargeable battery through the anti-reverse diode, the anode of the protection diode is connected to the input terminal of the switching circuit, and the negative pole is connected to the output terminal of the charging circuit. When the output terminal of the charging circuit is short-circuited, the voltage at the input terminal of the switching circuit The switch circuit is cut off by pulling low through the protection diode. The charging circuit with short-circuit protection is simple and reliable, and the circuit cost is saved.

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 protection diode 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 terminal of the control circuit connected to the output terminal of the transformer rectifier circuit and the sampling circuit, the output terminal is connected to the input terminal of the switch circuit, and the control circuit controls the on and off of the switch circuit according to the sampling voltage of the sampling circuit, The output end of the switch circuit is connected to the input end of the constant current circuit, the output end of the constant current circuit is connected to the rechargeable battery through an anti-reverse diode, and the anode of the protection diode is connected to the input end of the switch circuit , the negative electrode is connected to the output terminal of the charging circuit, when the output terminal of the charging circuit is short-circuited, the voltage of the input terminal of the switching circuit is pulled down by the protection diode, so that the switching circuit is cut off.

Preferably, the control circuit includes a protection resistor, a voltage regulator tube, a first adjustable resistor and an operational amplifier, one end of the protection resistor is connected to the output end of the transformer rectification circuit, and the other end is grounded through the voltage regulator tube, The first adjustable resistor is connected in parallel with the regulator tube, the non-inverting input terminal of the operational amplifier is connected to the adjusting terminal of the first adjustable resistor, the inverting input terminal is connected to the sampling circuit, and the output terminal is connected to the sampling circuit. The input terminals of the switch circuit are connected.

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 rectifier 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 voltage dividing diode, the emitter of the first triode is grounded, the base is connected to the cathode of the voltage dividing diode, and the collector is connected to the constant current circuit The input terminal of the voltage dividing diode is connected with the output terminal of the control circuit.

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 transformer rectification circuit, and the negative pole is connected to the base of the second triode, and the light emitting diode is Lights up when the switch circuit is turned on, and goes out when the switch circuit is turned off.

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

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, and one end of the output end of the rectifier is grounded.

Preferably, the charging circuit further includes an isolation diode, the anode of the isolation diode is connected to a direct current, and the cathode is connected to the other end of the output terminal of the rectifier.

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

In the charging circuit and charger with short-circuit protection, when the output terminal of the charger is short-circuited, the voltage at the input terminal of the switch circuit is pulled down through the protection diode, so that the switch circuit is cut off and the charger stops charging. Therefore, the charger can be effectively protected when the output terminal of the charger is accidentally short-circuited. The short-circuit protection is realized by a simple protection diode, which is simple and reliable, and can effectively save circuit costs.

【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 protection diode and an anti-reverse diode. The charging module includes a transformer rectifying circuit, a control circuit, a switching circuit, a constant current circuit and a sampling circuit. The output terminal of the above-mentioned transformer and rectifier circuit is connected with the sampling circuit, the output terminal of the control circuit is connected with the input terminal 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 terminal of the switch circuit is connected with the constant The input 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 anode of the protection diode is connected with the input terminal of the switching circuit, and the negative pole is connected with the output terminal of the charging circuit. When the output terminal of the charging circuit is short-circuited , the voltage at the input terminal of the switch circuit is pulled down by the protection diode, so that the switch circuit is cut off.

Embodiment one

As shown in Figure 1, the charging circuit with short circuit protection includes a charging module 10, a protection diode 20 and an anti-reverse diode 30, wherein: the charging module 10 includes a transformer rectifying circuit 11, a control circuit 12, a switching circuit 13, and 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 and the sampling circuit 15, the output terminal of the control circuit 12 is connected with the input terminal of the switch circuit 13, and the switch The output end of the circuit 13 is connected with the input end of the constant current circuit 14 , and the output end 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 anode of the protective diode 20 is connected to the input terminal of the switch circuit 13, and the negative pole is connected to the output terminal of the charging circuit (ie, the input terminal of the rechargeable battery). 20 is pulled low, the switch circuit 13 is cut off, and the charging circuit stops charging, thereby realizing the short circuit protection function. Since the short-circuit protection function can be realized through a protection diode 20, the circuit is simple and reliable, the response speed is fast, and the circuit cost can also be saved.

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 protection diode D6 and an anti-reverse diode D2, wherein: the charging module 10 includes a transformer rectifying circuit 11, a control circuit 12, a switch circuit 13, and a constant current circuit 14 and sampling circuit 15, wherein:

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 Figure 2, the control circuit 12 includes a protection resistor R1, a voltage regulator tube D4, a first adjustable resistor Rw1, and an operational amplifier OP1. One end of the protection resistor R1 is connected to the output terminal 2 of the rectifier D3, and the other end is passed through the voltage regulator tube. D4 is grounded, and the first adjustable resistor Rw1 is connected in parallel with the regulator tube D4. In this embodiment, a resistor R2 connected in series with the first adjustable resistor can also be set. The non-inverting input terminal of the operational amplifier OP1 is connected to the adjustment terminal of the first adjustable resistor Rw1, the inverting input terminal is connected to the junction of the sampling resistor R7 and the voltage dividing resistor R8 in the sampling circuit 15, and the output terminal is connected to the switch circuit through the resistor R3 13 input connected.

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, a first voltage-dividing diode D7 and a second voltage-dividing diode D8, one end of the first voltage-dividing diode D7 is connected to the resistor R3, and the other end is connected to the first voltage-dividing diode D8 through the second voltage-dividing diode D8. The base of the transistor Q1 is connected, the emitter of the first transistor Q1 is connected to the ground, the collector is connected to the input terminal of the constant current circuit 206, and the first transistor Q1 is also connected to the ground through the resistor R4. In other implementation manners, the first voltage-dividing diode D7 and the second voltage-dividing diode D8 can also be realized by using a voltage-dividing diode or a voltage-dividing resistor.

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 and a voltage dividing resistor R8. One end of the sampling resistor R7 is grounded, and the other end is connected in series with the voltage dividing resistor R8 to the collector of the second triode Q2. The sampling resistor R7 The connection with the voltage dividing resistor R8 is connected to the inverting input terminal of the operational amplifier OP1, that is, the sampling voltage of the sampling circuit 15 is used as the voltage of the inverting input terminal of the operational amplifier OP1. The second energy storage capacitor C2 is connected in parallel with the sampling resistor R7 and the voltage dividing resistor R8.

In this embodiment, the anode of the protection diode D6 is connected to the input terminal of the switch circuit 13, and the negative pole is connected to the output terminal of the charging circuit (that is, the input terminal of the rechargeable battery). When the output terminal of the charging circuit is short-circuited, the input terminal of the switch circuit 13 The terminal voltage is pulled down by the protection diode D6, so that the switch circuit 13 is cut off, and the charging circuit stops charging, thereby realizing the short circuit protection function.

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 to be VB=VR*(R7+R8)/R7-VD2, and the charging current is set to be IQ2c=(VD5-VQ2be)/(Rw2+R6). By adjusting the first adjustable resistor Rw1, when charging, the non-inverting input terminal voltage VR of the operational amplifier OP1 is higher than the inverting input terminal voltage (that is, the sampling voltage of the sampling circuit 15), so that the output terminal of the operational amplifier OP1 outputs when charging. High level, because the output terminal of the operational amplifier OP1 outputs a high level, the first triode Q1 is turned on, and then charges the rechargeable battery BT after passing through the constant current circuit 14, at this time, the light emitting diode D5 lights up. When the rechargeable battery BT is charged to the set charging voltage VB, the voltage VR of the non-inverting input terminal of the operational amplifier OP1 is lower than the voltage of the inverting input terminal, the output terminal of the operational amplifier OP1 outputs a low level, and the first transistor Q1 is cut off. 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 cut 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 at the output terminal of the control circuit 12 is quickly pulled down by the protection diode D6, which is much smaller than the voltage Vp when the charging circuit is working. For example, the voltage Vp is quickly pulled down to about 1V by the protection diode D6. The voltage Vp required for the charging circuit to work is about 2.1V. The first voltage-dividing diode D7 and the second voltage-dividing diode D8 are used to increase the conduction voltage of Vp, that is, when the voltage Vp is rapidly pulled down through the protection diode D6, due to the first voltage-dividing diode D7 and the second voltage-dividing diode The voltage division of D8 makes the base voltage of the first triode Q1 lower, which improves the reliability of short-circuit protection. Because Vp is pulled down, the first transistor Q1 is cut off (equivalent to the collector of the first transistor Q1 being suspended), and the second transistor Q2 is also cut off, the constant current circuit 14 cannot work, and the charging circuit is automatically cut off , so as to realize the short-circuit protection function. Since the first triode Q1 is cut off at this time, the light emitting diode D5 is turned off. After the short circuit is eliminated, the output terminal voltage Vp of the control circuit 12 quickly recovers to the voltage when the charging circuit works, so that the first triode Q1 is turned on, the light-emitting diode D5 is lit, and the constant current circuit 14 works normally, so the charging circuit automatically Resume charging.

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

In the charging circuit and charger with short-circuit protection, when the output terminal of the charger is short-circuited, the voltage at the input terminal of the switch circuit 13 is pulled down through the protection diode D6, so that the switch circuit 13 is cut off, and the charger stops charging. Therefore, the charger can be effectively protected when the output terminal of the charger is accidentally short-circuited. The short-circuit protection is realized by the simple protection diode D6, which is simple, reliable and fast in response, and can effectively save circuit cost. 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 (9)

1. the charging circuit with short-circuit protection, it is characterized in that, comprise charging module, protection diode and counnter attack diode, described charging module comprises Transformer Rectifier circuit, control circuit, switching circuit, constant-current circuit and sample circuit, the input of described control circuit is connected with the output of described Transformer Rectifier circuit and sample circuit, the output of described control circuit is connected with the input of described switching circuit, described control circuit controls conducting and the cut-off of described switching circuit according to the sampled voltage of described sample circuit, when described switching circuit conducting, described charging circuit charges to rechargeable battery, when described switching circuit cut-off, described charging circuit stops charging to rechargeable battery, thus function of automatically cutting off when realizing being full of electricity, the output of described switching circuit is connected with the input of described constant-current circuit, the output of described constant-current circuit is connected with rechargeable battery by counnter attack diode, the positive pole of described protection diode is connected with the input of described switching circuit, negative pole is connected with the output of charging circuit, during the output short circuit of described charging circuit, the input terminal voltage of described switching circuit is dragged down by described protection diode, and described switching circuit is ended, described control circuit comprises protective resistance, voltage-stabiliser tube, the first adjustable resistance and operational amplifier, one end of described protective resistance is connected with the output of Transformer Rectifier circuit, the other end is by described voltage-stabiliser tube ground connection, described first adjustable resistance is in parallel with described voltage-stabiliser tube, the in-phase input end of described operational amplifier is connected with the adjustable side of described first adjustable resistance, inverting input is connected with described sample circuit, and output is connected with the input of described switching circuit.

2. the charging circuit of band short-circuit protection according to claim 1; it is characterized in that; described control circuit also comprises the first storage capacitor and filter capacitor; described first storage capacitor one end is connected with the output of Transformer Rectifier circuit; other end ground connection, described filter capacitor is in parallel with described first storage capacitor.

3. the charging circuit of band short-circuit protection according to claim 1; it is characterized in that; described switching circuit comprises the first triode and dividing potential drop diode; the grounded emitter of described first triode; base stage is connected with the negative pole of described dividing potential drop diode; collector electrode is connected with the input of described constant-current circuit, and the positive pole of described dividing potential drop diode is connected with the output of described control circuit.

4. the charging circuit of band short-circuit protection according to claim 3; it is characterized in that; described constant-current circuit comprises the second triode and the second adjustable resistance; the base stage of described second triode is connected with the collector electrode of described first triode; emitter is connected with the output of Transformer Rectifier circuit by described second adjustable resistance, and collector electrode is connected with rechargeable battery by described counnter attack diode.

5. the charging circuit of band short-circuit protection according to claim 4; it is characterized in that; described constant-current circuit also comprises light-emitting diode; the positive pole of described light-emitting diode is connected with the output of Transformer Rectifier circuit; negative pole is connected with the base stage of described second triode; described light-emitting diode is lighted when described switching circuit conducting, extinguishes when described switching circuit cut-off.

6. the charging circuit of the band short-circuit protection according to claim 4 or 5; it is characterized in that; described sample circuit comprises the second storage capacitor, sampling resistor and divider resistance; described sampling resistor one end ground connection; the other end is connected with the collector electrode of described second triode after connecting with described divider resistance; described sampling resistor is connected with the inverting input of described operational amplifier with the junction of described divider resistance, and described second storage capacitor and described sampling resistor, divider resistance are in parallel.

7. the charging circuit of band short-circuit protection according to claim 1; it is characterized in that; described Transformer Rectifier circuit comprises transformer and rectifier; the primary coil of described transformer is connected with civil power; secondary coil is connected with the input of described rectifier, one end ground connection of the output of described rectifier.

8. the charging circuit of band short-circuit protection according to claim 7, is characterized in that, described charging circuit also comprises isolating diode, and the positive pole of described isolating diode is connected with direct current, and negative pole is connected with the other end of the output of described rectifier.

9. a charger, is characterized in that, comprises the charging circuit of the band short-circuit protection in claim 1 to 8 described in any one.