Overload protection circuit

Abstract

The utility model discloses an overload protection circuit, which comprises a transduction unit, a comparison circuit, a control unit, a relay driving circuit and a relay used for controlling on-off of a load loop, the transduction unit is used for collecting load electric signals and outputting analog voltage signals and reference voltage signals, and the comparison circuit is used for comparing the analog voltage signals with the reference voltage signals. The transduction unit is provided with a first output end used for outputting an analog voltage signal and a second output end used for outputting a reference voltage signal, a first input end of the comparison circuit is connected with the first output end of the transduction unit, and a second input end of the comparison circuit is connected with the second output end of the transduction unit. The output end of the comparison circuit is connected with the input end of the control unit, the output end of the control unit is connected with the input end of the relay driving circuit, and the output end of the relay driving circuit is connected with the relay. The overload protection circuit provided by the utility model has the advantages of high acquisition precision, strong reliability and simple process design.

Description

Technical Field

[0001] The utility model relates to the field of overload protection, in particular to an overload protection circuit. Background Art

[0002] In a traditional PTC overload protection circuit, an on-board sampling resistor is used to collect electrical signals, and then an operational amplifier and an MCU are used to process the collected electrical signals. Due to the influence of the resistance value error and temperature drift of the resistor itself, the electrical signals collected by the resistor have errors. At this time, after the amplification processing of the operational amplifier, the error signals will be amplified, resulting in signal distortion. At the same time, the traditional PTC uses an IGBT control loop to turn on and off. This form needs to pay special attention to the heat dissipation of the IGBT itself, and has high requirements for product technology, structure, etc.

[0003] Therefore, there is an urgent need for an overload protection circuit with high acquisition accuracy, strong reliability and simple design. Summary of the Utility Model

[0004] The utility model aims to at least solve one of the technical problems existing in the prior art, and provides an overload protection circuit with high acquisition accuracy, strong reliability and simple process design.

[0005] The technical solution of the utility model is realized as follows: The utility model discloses an overload protection circuit, which includes a transducer unit, a comparison circuit, a control unit, a relay driving circuit and a relay for controlling the on-off of a load circuit. The transducer unit is used to collect load electrical signals and output an analog voltage signal and a reference voltage signal. The transducer unit has a first output end for outputting the analog voltage signal and a second output end for outputting the reference voltage signal. The first input end of the comparison circuit is connected to the first output end of the transducer unit, the second input end of the comparison circuit is connected to the second output end of the transducer unit, the output end of the comparison circuit is connected to the input end of the control unit, the output end of the control unit is connected to the input end of the relay driving circuit, and the output end of the relay driving circuit is connected to the relay.

[0006] Further, a filter or / and a follower circuit are provided between the first output end of the transducer unit and the first input end of the comparison circuit.

[0007] Further, the input end of the filter is connected to the first output end of the transducer unit, the output end of the filter is connected to the input end of the follower circuit, and the output end of the follower circuit is connected to the first input end of the comparison circuit.

[0008] Further, the filter includes a resistor R10, a resistor R9, a capacitor C11, and a capacitor C12. One end of the resistor R10 is connected to the input end of the filter, one end of the capacitor C11, and one end of the capacitor C12, and is grounded. The other end of the resistor R10 is connected to one end of the resistor R9 and the other end of the capacitor C11. The other end of the resistor R9 is connected to the output end of the filter and the other end of the capacitor C12.

[0009] Further, the follower circuit includes an operational amplifier IC2B. The non-inverting input terminal of the operational amplifier IC2B is connected to the input end of the follower circuit. The inverting input terminal of the operational amplifier IC2B is connected to the output end of the operational amplifier IC2B. The output end of the operational amplifier IC2B is connected to the output end of the follower circuit.

[0010] Further, the comparison circuit includes an operational amplifier IC2A. The non-inverting input terminal of the operational amplifier IC2A is directly connected or connected to the second input end of the comparison circuit through a resistor R8. The inverting input terminal of the operational amplifier IC2A is directly connected or connected to the first input end of the comparison circuit through a resistor R11. The inverting input terminal of the operational amplifier IC2A is connected to the output end of the operational amplifier IC2A through a resistor R12. The output end of the operational amplifier IC2A is connected to the input end of the control unit.

[0011] Further, the relay drive circuit includes an optocoupler IC12. The first input terminal of the optocoupler IC12 is connected to a first voltage. The second input terminal of the optocoupler IC12 is connected to one end of a resistor R36 and one end of a resistor R38. The other end of the resistor R36 is connected to the first voltage. The other end of the resistor R38 is connected to the output end of the control unit. The first output terminal of the optocoupler IC12 is connected to one end of the coil of the relay and the positive electrode of a diode D3. The negative electrode of the diode D3 is connected to the first voltage. The second output terminal of the optocoupler IC12 is grounded. The other end of the coil of the relay is connected to the first voltage. The first contact and the second contact of the relay are connected in series in the load power supply circuit. When the coil of the relay is energized, the first contact and the second contact of the relay are disconnected, so that the load power supply circuit is disconnected.

[0012] Further, the relay is a magnetic latching relay.

[0013] Further, the transducer unit adopts a transducer based on the Hall effect.

[0014] Further, the control unit adopts an MCU.

[0015] Compared with the prior art, the utility model has the following beneficial effects:

[0016] The overload protection circuit of the present utility model includes a transducer, a comparison circuit, a control unit, a relay drive circuit, and a relay for controlling the on / off of the load circuit. The transducer unit is used to collect the load electrical signal and output an analog voltage signal and a reference voltage signal. The transducer unit has a first output terminal for outputting the analog voltage signal and a second output terminal for outputting the reference voltage signal. The first input terminal of the comparison circuit is connected to the first output terminal of the transducer, the second input terminal of the comparison circuit is connected to the second output terminal of the transducer, the output terminal of the comparison circuit is connected to the input terminal of the control unit, the output terminal of the control unit is connected to the input terminal of the relay drive circuit, and the output terminal of the relay drive circuit is connected to the relay. When the electrical signal to be detected passes through the transducer, the transducer outputs a reference voltage signal (Vref) and an analog voltage signal (Vout1). The Vout1 voltage signal is first subjected to two-stage low-pass filtering and then becomes the voltage signal Vout2 through the operational amplifier follower process. The value of the Vout2 voltage is then compared with the value of the reference voltage signal Vref in real time. When Vout2 > Vref, the comparison circuit outputs a high level (at this time, it is in the overload state); when Vout2 < Vref, the comparison circuit outputs a low level (at this time, it is in the normal state), and the corresponding high and low levels are transmitted to the MCU for judgment processing. When the load (such as PTC) operates normally, the MCU outputs RL1_B as a high level, the coil of the relay loses power, and the first contact and the second contact are conducted. At this time, the load is connected to the circuit for heating; when the load (such as PTC) is overloaded, the MCU outputs RL1_B as a low level, the coil of the relay is energized, and the first contact and the second contact are disconnected. At this time, the circuit is disconnected and the load stops heating.

[0017] The present utility model first uses a transducer and a magnetic latching relay in the PTC design. This transducer based on the Hall effect has the characteristics of high precision, low power consumption, and fast response, and the collected signal is more accurate. At the same time, a magnetic latching relay is used on the heating circuit, which can effectively solve the process and structure problems of traditional IGBT heat dissipation, and also solve the problem of long-term heating of the coil of the conventional relay. Using this solution can effectively reduce the energy consumption of the entire system and simplify the design process flow of the product. Brief Description of the Drawings

[0018] Figure 1 It is a principle block diagram of the overload protection circuit provided by the embodiment of the present utility model;

[0019] Figure 2 It is a circuit diagram of the signal acquisition and comparison circuit provided by an embodiment of the present utility model;

[0020] Figure 3 It is a circuit diagram of the control unit provided by an embodiment of the present utility model;

[0021] Figure 4The circuit diagram of a relay and a relay driving circuit provided by an embodiment of the present utility model. Detailed implementation manners

[0022] To enable those skilled in the art to better understand the technical solutions of the present utility model, the technical solutions in the embodiments of the present utility model will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are part of the embodiments of the present utility model, rather than all of the embodiments. Based on the embodiments in the present utility model, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present utility model.

[0023] See Figures 1 to 4 , an overload protection circuit is disclosed in an embodiment of the present utility model, including a signal acquisition circuit, a comparison circuit, a control unit, a relay driving circuit, and a relay for controlling the on / off of a load loop (the load can be a PTC or other resistive loads). The signal acquisition circuit includes a transducer unit, and the transducer unit is used to acquire load electrical signals (such as a transducer acquires the current signal generated by the load), and outputs an analog voltage signal and a reference voltage signal. The transducer unit has a first output terminal for outputting the analog voltage signal and a second output terminal for outputting the reference voltage signal. The first input terminal of the comparison circuit is connected to the first output terminal of the transducer unit, the second input terminal of the comparison circuit is connected to the second output terminal of the transducer unit, the output terminal of the comparison circuit is connected to the input terminal of the control unit, the output terminal of the control unit is connected to the input terminal of the relay driving circuit, and the output terminal of the relay driving circuit is connected to the relay. The transducer unit is used for the monitoring and conversion of the measured electrical signal. The comparison circuit is used to compare the magnitudes of the reference voltage and the analog output voltage; the control unit is used for system logic signal judgment and signal processing; the relay driving circuit is used to drive the relay to act. The relay (such as a magnetic latching relay) is used to control the on / off of the load loop.

[0024] Further, the transducer unit adopts a transducer based on the Hall effect. The transducer unit is connected in series on the high-voltage bus inside the PTC and is used to detect the current change on the bus. The model of the transducer unit in one embodiment is LESR50-NP.

[0025] Further, the control unit adopts an MCU. For the specific circuit, see Figure 3 as shown.

[0026] Further, the signal acquisition circuit further includes a filter and / or a follower circuit, and the filter and / or the follower circuit is located between the first output terminal of the transducer unit and the first input terminal of the comparison circuit. The filter is used for filtering the voltage signal; the follower circuit is used for signal isolation and buffering.

[0027] Further, the input end of the filter is connected to the first output end of the transducer unit, the output end of the filter is connected to the input end of the follower circuit, and the output end of the follower circuit is connected to the first input end of the comparison circuit.

[0028] Further, referring to Figure 2 , the filter includes a resistor R10, a resistor R9, a capacitor C11, and a capacitor C12. One end of the resistor R10 is connected to the input end of the filter, one end of the capacitor C11, and one end of the capacitor C12, and is grounded. The other end of the resistor R10 is connected to one end of the resistor R9 and the other end of the capacitor C11. The other end of the resistor R9 is connected to the output end of the filter and the other end of the capacitor C12.

[0029] Further, referring to Figure 2 , the follower circuit includes an operational amplifier IC2B. The non-inverting input end of the operational amplifier IC2B is connected to the input end of the follower circuit. The inverting input end of the operational amplifier IC2B is connected to the output end of the operational amplifier IC2B. The output end of the operational amplifier IC2B is connected to the output end of the follower circuit.

[0030] Further, referring to Figure 2 , the comparison circuit includes an operational amplifier IC2A. The non-inverting input end of the operational amplifier IC2A is directly or through a resistor R8 connected to the second input end of the comparison circuit. The inverting input end of the operational amplifier IC2A is directly or through a resistor R11 connected to the first input end of the comparison circuit. The inverting input end of the operational amplifier IC2A is connected to the output end of the operational amplifier IC2A through a resistor R12. The output end of the operational amplifier IC2A is connected to the input end of the control unit.

[0031] Further, the relay is a magnetic latching relay. The relay can be a single-coil relay, a double-coil relay, etc.

[0032] In some embodiments, referring to Figure 4 , the relay driving circuit includes an optocoupler IC12. The first input end of the optocoupler IC12 is connected to a first voltage. The second input end of the optocoupler IC12 is connected to one end of a resistor R36 and one end of a resistor R38. The other end of the resistor R36 is connected to the first voltage. The other end of the resistor R38 is connected to the output end of the control unit. The first output end of the optocoupler IC12 is connected to one end of the coil of the relay and the positive pole of a diode D3. The negative pole of the diode D3 is connected to a second voltage. The second output end of the optocoupler IC12 is grounded. The other end of the coil of the relay is connected to the second voltage. The first contact and the second contact of the relay are connected in series in the load power supply circuit. When the coil of the relay is energized, the first contact and the second contact of the relay are disconnected, so that the load power supply circuit is disconnected.

[0033] In some other embodiments, referring to Figure 4 , the relay driving circuit includes optocoupler IC12 and optocoupler IC10. The first input terminal of optocoupler IC12 is connected to a first voltage. The second input terminal of optocoupler IC12 is respectively connected to one end of resistor R36 and one end of resistor R38. The other end of resistor R36 is connected to the first voltage. The other end of resistor R38 is connected to the first output terminal RL1_B of the control unit. The first output terminal of optocoupler IC12 is respectively connected to one end of the second coil of the relay and the positive electrode of diode D3. The negative electrode of diode D3 is connected to a second voltage. The second output terminal of optocoupler IC12 is grounded. The other end of the second coil of the relay is connected to the second voltage. The fifth contact and the sixth contact controlled by the second coil of the relay are connected in series in the load power supply circuit. When the second coil of the relay is powered on, the fifth contact and the sixth contact of the relay are disconnected, so that the load power supply circuit is disconnected;

[0034] The first input terminal of optocoupler IC10 is connected to a first voltage. The second input terminal of optocoupler IC10 is respectively connected to one end of resistor R32 and one end of resistor R34. The other end of resistor R32 is connected to the first voltage. The other end of resistor R34 is connected to the second output terminal RL1_A of the control unit. The first output terminal of optocoupler IC10 is respectively connected to one end of the first coil of the relay and the positive electrode of diode D1. The negative electrode of diode D1 is connected to a second voltage. The second output terminal of optocoupler IC10 is grounded. The other end of the first coil of the relay is connected to the second voltage. The first coil of the relay is used to control the conduction or disconnection of the third contact and the fourth contact. The third contact and the fourth contact can be used to expand the function of the overload protection circuit, such as for overload alarm and so on.

[0035] The first voltage in this embodiment can be, but is not limited to, 3.3V. The second voltage can be, but is not limited to, 5V.

[0036] The working principle of an embodiment of the present utility model is as follows: When the detected electrical signal passes through the transducer, the transducer outputs a reference voltage signal (Vref) and an analog voltage signal (Vout1). The output Vout1 voltage signal first undergoes two-stage low-pass filtering and then becomes the voltage signal Vout2 through operational amplifier follower processing. The value of the Vout2 voltage is then compared with the value of the reference voltage signal Vref in real time. When Vout2 > Vref, the comparison circuit outputs a high level (at this time, it is in an overload state); when Vout2 < Vref, the comparison circuit outputs a low level (at this time, it is in a normal state), and the corresponding high and low levels are transmitted to the control unit for judgment processing. When the PTC operates normally, the control unit outputs RL1_A as a low level and RL1_B as a high level. The first coil in the relay is energized, and the second coil is de-energized. The fifth and sixth contacts are conducted, and at this time, the load is connected to the circuit for heating; when the PTC is overloaded, the control unit outputs RL1_A as a high level and RL1_B as a low level. The first coil in the relay is de-energized, and the second coil is energized. The fifth and sixth contacts are disconnected, and at this time, the circuit is disconnected, and the load stops heating.

[0037] The present utility model is an overload protection circuit with high acquisition accuracy, strong reliability, and simple process design. The present utility model can be used in the PTC overload protection circuit. The present utility model first uses a transducer and a magnetic latching relay in the PTC design. This transducer based on the Hall effect has the characteristics of high precision, low power consumption, and fast response, making the collected signals more accurate; at the same time, a magnetic latching relay is adopted on the heating circuit, which can effectively solve the process and structure problems of traditional IGBT heat dissipation, and also solve the problem of long-term heating of the coil of a conventional relay. Using this solution can effectively reduce the energy consumption of the entire system and simplify the design process flow of the product.

[0038] It can be understood that the above embodiments are merely exemplary embodiments adopted to illustrate the principle of the present utility model. However, the present utility model is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the present utility model, and these modifications and improvements are also regarded as the protection scope of the present utility model.

Claims

1. An overload protection circuit, characterized in that : It includes a transducer unit, a comparison circuit, a control unit, a relay drive circuit, and a relay for controlling the on / off of a load circuit. The transducer unit is used to collect load electrical signals and output an analog voltage signal and a reference voltage signal. The transducer unit has a first output terminal for outputting the analog voltage signal and a second output terminal for outputting the reference voltage signal. The first input terminal of the comparison circuit is connected to the first output terminal of the transducer unit, the second input terminal of the comparison circuit is connected to the second output terminal of the transducer unit, the output terminal of the comparison circuit is connected to the input terminal of the control unit, the output terminal of the control unit is connected to the input terminal of the relay drive circuit, and the output terminal of the relay drive circuit is connected to the relay.

2. The overload protection circuit according to claim 1, characterized in that: A filter and / or a follower circuit is provided between the first output terminal of the transducer unit and the first input terminal of the comparison circuit.

3. The overload protection circuit according to claim 2, wherein: The input terminal of the filter is connected to the first output terminal of the transducer unit, the output terminal of the filter is connected to the input terminal of the follower circuit, and the output terminal of the follower circuit is connected to the first input terminal of the comparison circuit.

4. The overload protection circuit according to claim 2 or 3, characterized in that: The filter includes a resistor R10, a resistor R9, a capacitor C11, and a capacitor C12. One end of the resistor R10 is connected to the input terminal of the filter, one end of the capacitor C11, and one end of the capacitor C12, and is grounded. The other end of the resistor R10 is connected to one end of the resistor R9 and the other end of the capacitor C11. The other end of the resistor R9 is connected to the output terminal of the filter and the other end of the capacitor C12.

5. The overload protection circuit according to claim 2 or 3, characterized in that: The follower circuit includes an operational amplifier IC2B. The non-inverting input terminal of the operational amplifier IC2B is connected to the input terminal of the follower circuit, the inverting input terminal of the operational amplifier IC2B is connected to the output terminal of the operational amplifier IC2B, and the output terminal of the operational amplifier IC2B is connected to the output terminal of the follower circuit.

6. The overload protection circuit according to any one of claims 1 to 3, characterized in that: The comparison circuit includes an operational amplifier IC2A. The non-inverting input terminal of the operational amplifier IC2A is directly or via a resistor R8 connected to the second input terminal of the comparison circuit. The inverting input terminal of the operational amplifier IC2A is directly or via a resistor R11 connected to the first input terminal of the comparison circuit. The inverting input terminal of the operational amplifier IC2A is connected to the output terminal of the operational amplifier IC2A via a resistor R12. The output terminal of the operational amplifier IC2A is connected to the input terminal of the control unit.

7. The overload protection circuit according to any one of claims 1 to 3, characterized in that: The relay drive circuit includes an optocoupler IC12. The first input terminal of the optocoupler IC12 is connected to a first voltage. The second input terminal of the optocoupler IC12 is connected to one end of a resistor R36 and one end of a resistor R38 respectively. The other end of the resistor R36 is connected to the first voltage. The other end of the resistor R_38 is connected to the output terminal of the control unit. The first output terminal of the optocoupler IC12 is connected to one end of the coil of the relay and the positive electrode of a diode D3 respectively. The negative electrode of the diode D3 is connected to the first voltage. The second output terminal of the optocoupler IC12 is grounded. The other end of the coil of the relay is connected to the first voltage. The first contact and the second contact of the relay are connected in series in the load power supply circuit. When the coil of the relay is energized, the first contact and the second contact of the relay are disconnected, so that the load power supply circuit is disconnected.

8. The overload protection circuit according to claim 1, characterized in that: The relay is a magnetic latching relay.

9. The overload protection circuit according to claim 1, characterized in that: The transducer unit uses a transducer based on the Hall effect.

10. The overload protection circuit according to claim 1, wherein: The control unit uses an MCU.

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