Overcurrent protection trigger circuit and method for inverter

Abstract

The invention discloses an inverter overcurrent protection trigger circuit and method, the circuit comprises a detection circuit, an operational amplifier circuit and a judgment circuit, the output end of the detection circuit is connected to the input end of the judgment circuit through the operational amplifier circuit; the judgment circuit comprises a positive half-cycle judgment unit and a negative half-cycle judgment unit, and is used for outputting an overcurrent signal when the positive half-cycle current signal and the negative half-cycle current signal are confirmed to be in an overcurrent state; and the judgment circuit outputs the over-current signal to an interruption pin of the control chip so as to enable the inverter to stop working after triggering interruption. According to the invention, the overcurrent state can be judged and protected only by constructing a hardware protection circuit without depending on a complex instruction algorithm of a microprocessor, the code writing amount and the computing resource consumption are effectively reduced, the hardware circuit protection logic is clear, and the execution delay value of the protection logic can be effectively reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of switching power supplies, and in particular to an inverter overcurrent protection trigger circuit and method. Technical Background

[0002] An inverter, also known as an inverter power supply, is a power electronic device that converts direct current (DC) into alternating current (AC) according to specific algorithms, instructions and logic. It often converts direct current stored in energy storage devices such as lithium batteries and lead-acid batteries into alternating current required by various electrical appliances. Therefore, inverters are widely used in modern society. Especially in recent years, with the rapid development of industries such as photovoltaics and new energy vehicles, the market demand for inverters has shown exponential growth.

[0003] In actual applications of inverters, it is difficult to avoid overcurrent or short circuit at the load end. If these two conditions are not protected, the inverter may easily fail during use.

[0004] Although existing invention patents use embedded microprocessors to detect the inverter's operating current in real time to achieve overcurrent protection and short-circuit protection, such technical solutions also have the following shortcomings: (1) The protection logic is too complex, requiring the microprocessor to monitor the inverter load current in real time, which involves the amount of microprocessor calculations and thus occupies the microprocessor's limited computing resources; (2) In software protection mode, there is a problem of internal clock delay. The signal can only become an instruction that the microprocessor can recognize after analog sampling and digital-to-analog conversion, and the delay value depends on the main frequency of the microprocessor (the specification of the microprocessor), but the analog circuit constructed by hardware has much less limitations in this regard. Summary of the invention

[0005] In view of this, an object of the present invention is to provide an inverter overcurrent protection triggering circuit and method that does not rely on microprocessor detection and has low delay.

[0006] The specific technical solutions of the present invention are as follows:

[0007] In a first aspect, the present invention application proposes an inverter overcurrent protection trigger circuit, the inverter overcurrent protection trigger circuit comprises a detection circuit, an operational amplifier circuit and a judgment circuit, the output end of the detection circuit is connected to the input end of the judgment circuit through the operational amplifier circuit;

[0008] The judgment circuit comprises a positive half-cycle judgment unit and a negative half-cycle judgment unit, and the input end of the positive half-cycle judgment unit and the input end of the negative half-cycle judgment unit are both connected to the output end of the operational amplifier circuit;

[0009] The positive half-cycle judgment unit is used to output an overcurrent signal when confirming that the positive half-cycle current signal is in an overcurrent state;

[0010] The negative half-cycle judgment unit is used to output an overcurrent signal when confirming that the negative half-cycle current signal is in an overcurrent state;

[0011] The judgment circuit outputs the overcurrent signal to the interrupt pin of the control chip to trigger an interrupt to stop the inverter from working.

[0012] Optionally, the judgment circuit also includes an OR gate circuit, a first input end of the OR gate circuit is connected to the output end of the positive half-cycle judgment unit, a second input end of the OR gate circuit is connected to the output end of the negative half-cycle judgment unit, and the output end of the OR gate circuit serves as the output end of the judgment circuit.

[0013] Optionally, the OR gate circuit includes a first diode and a second diode, the anode of the first diode is connected to the output end of the positive half-cycle judgment unit, the anode of the second diode is connected to the output end of the negative half-cycle judgment unit, the cathode of the first diode is connected to the cathode of the second diode, and the cathode of the first diode serves as the output end of the judgment circuit.

[0014] Optionally, the positive half-cycle circuit includes a first voltage comparator, a non-inverting input terminal of the first voltage comparator is connected to the output terminal of the operational amplifier circuit, and an inverting input terminal of the first voltage comparator is connected to a first reference voltage.

[0015] Optionally, the negative half-cycle circuit includes a second voltage comparator, a non-inverting input terminal of the second voltage comparator is connected to a second reference voltage, and an inverting input terminal of the second voltage comparator is connected to an output terminal of the operational amplifier circuit.

[0016] Optionally, the operational amplifier circuit includes a first operational amplifier, a first resistor and a second resistor, the inverting input terminal of the first operational amplifier is connected to the output terminal of the detection circuit through the first resistor, the non-inverting input terminal of the first operational amplifier is connected to the ground, the positive power supply terminal of the first operational amplifier is connected to the positive power supply, and the negative power supply terminal of the first operational amplifier is connected to the negative power supply.

[0017] Optionally, the amplification factor of the operational amplifier circuit is determined by the ratio of the first resistor to the second resistor.

[0018] Optionally, the detection circuit includes a sampling resistor or a current transformer.

[0019] In a second aspect, the present invention also provides an inverter overcurrent protection trigger circuit method, the inverter overcurrent protection trigger circuit method comprising:

[0020] According to the sampling current of the inverter, peak values ​​of the positive half-cycle current signal and the negative half-cycle current signal of the sampling current are judged respectively, and an overcurrent signal is output when it is confirmed that the positive half-cycle current signal or the negative half-cycle current signal is in an overcurrent state;

[0021] The overcurrent signal is output to the interrupt pin of the control chip to trigger an interrupt to stop the inverter from working.

[0022] Optionally, the amplitude of the sampling current is in microvolt level or millivolt level.

[0023] The beneficial effects of the present invention are as follows:

[0024] The present invention uses an operational amplifier circuit, a positive half-cycle judgment unit and a negative half-cycle judgment unit to implement a complex instruction algorithm without relying on a microprocessor. It only needs to build a hardware protection circuit to judge and protect the overcurrent state, which effectively reduces the amount of code writing and computing resource consumption. The hardware circuit protection logic is clear and can effectively reduce the protection logic execution delay value. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A circuit schematic diagram of an inverter overcurrent protection trigger circuit of the present invention;

[0026] Figure 2 It is a simulation waveform diagram of an inverter overcurrent protection trigger circuit when overcurrent occurs in the present invention;

[0027] Figure 3 The present invention is a simulation waveform diagram of an inverter overcurrent protection trigger circuit in steady state. DETAILED DESCRIPTION

[0028] In order to enable those skilled in the art to better understand the present invention, the content of the present invention will be further explained through specific embodiments below. It should be noted that this embodiment is only one of the embodiments of the present invention. The embodiments obtained by relevant technical personnel without making other creative work all belong to the scope of protection of the present invention.

[0029] refer to Figure 1 , an embodiment of the present invention provides an inverter overcurrent protection trigger circuit, the inverter overcurrent protection trigger circuit comprises a detection circuit 100, an operational amplifier circuit 200 and a judgment circuit 300, the output end of the detection circuit 100 is connected to the input end of the judgment circuit 300 through the operational amplifier circuit 200;

[0030] The judgment circuit 300 includes a positive half-cycle judgment unit 310 and a negative half-cycle judgment unit 320, and the input end of the positive half-cycle judgment unit 310 and the input end of the negative half-cycle judgment unit 320 are both connected to the output end of the operational amplifier circuit 200;

[0031] The positive half-cycle judgment unit 310 is used to output an overcurrent signal when confirming that the positive half-cycle current signal is in an overcurrent state;

[0032] The negative half-cycle judgment unit 320 is used to output an overcurrent signal when confirming that the negative half-cycle current signal is in an overcurrent state;

[0033] The judgment circuit 300 outputs the over-current signal to the interrupt pin of the control chip to trigger an interrupt to stop the inverter from working.

[0034] The detection circuit 100 may be a sampling resistor, or other circuit structures or devices that can implement current sampling, such as a current transformer. In this embodiment, the detection circuit 100 is composed of a sampling resistor R3, that is, the sampling resistor R3 is directly connected in series with the load resistor R4, and then connected to the load end of the inverter.

[0035] The inverter in this embodiment is a unidirectional inverter power supply based on a half-bridge structure, wherein the effective value of the inverter output voltage is 230V, the frequency is 50Hz, and the rated output power of the inverter is 352W.

[0036] The sampling resistor R3 detects the load signal Vcs of the inverter in real time. When the load is small, the voltage drop on the corresponding sampling resistor R3 is small. Similarly, when the load current is too large or short-circuited, the voltage drop on the corresponding sampling resistor R3 increases. In this embodiment, the resistance of the sampling resistor is 20mΩ. When the load resistor R4 is rated for 150Ω, the peak voltage Vcs of the corresponding sampling resistor is 43mV, and the corresponding voltage peak of V3 is 2.1V (steady state). Figure 3 shown.

[0037] When the inverter load is overloaded, for example, load R3 is 100Ω and the load current is 1.5 times the rated load, the corresponding power P is:

[0038]

[0039] The corresponding sampling resistor peak voltage Vcs is 64.5mV, and the corresponding voltage peak of V3 is 3.24V (overcurrent). Figure 2 shown.

[0040] In this embodiment, the judgment circuit 300 is composed of a positive half-cycle judgment unit 310 and a negative half-cycle judgment unit 320. The positive half-cycle circuit includes a first voltage comparator U1, the non-inverting input terminal of the first voltage comparator U1 is connected to the output terminal of the operational amplifier circuit 200, and the inverting input terminal of the first voltage comparator U1 is connected to the first reference voltage +VREF. The negative half-cycle circuit includes a second voltage comparator U2, the non-inverting input terminal of the second voltage comparator U2 is connected to the second reference voltage -VREF, and the inverting input terminal of the second voltage comparator U2 is connected to the output terminal of the operational amplifier circuit 200. Among them, the reference voltages +VREF and -VREF of the first voltage comparator U1 and the second voltage comparator U2 have opposite polarities and equal absolute values, which serve as reference values ​​for the peak currents of the positive and negative cycles.

[0041] It should be noted that the voltage comparators in the positive half-cycle judgment unit 310 and the negative half-cycle judgment unit 320 can be composed of operational amplifiers or diodes and transistors. Any circuit that can compare two signals and realize conduction and shutdown meets the requirements.

[0042] In particular, the judgment circuit 300 includes a reference signal inside, which can be output by a linear regulator or a voltage regulator tube as the reference signal. Any method that can provide a reference signal meets the requirements.

[0043] The judgment circuit 300 of the present invention independently judges the signal. When the inverter is operating in overcurrent or short circuit, the positive half-cycle signal judgment circuit 300 will respond; the negative half-cycle signal judgment circuit 300 will respond. When the inverter is operating normally, the overcurrent protection and short circuit protection will not be triggered.

[0044] In particular, the output signal of the judgment circuit 300 of the present invention is a weak signal and does not directly act on the main power stage circuit of the inverter. The output signal of the judgment circuit 300 ultimately needs to pass through the interrupt pin of the embedded microprocessor, and the inverter will stop working after the interrupt is triggered.

[0045] In this embodiment, when it is necessary to judge overcurrent, +VREF is set to +2.5V, -VREF is set to -2.5V, and the operational amplifier circuit 200 outputs a signal. When the amplitude of the positive half-cycle signal is greater than +VREF (+2.5V), the first voltage comparator U1 is reversed to a high level. Figure 2 As shown in waveform 2#; when the amplitude of the negative half-cycle signal exceeds -VREF (-2.5V), the second voltage comparator U2 reverses to a high level, such as Figure 2 As shown in waveform 1#.

[0046] Therefore, when any positive half cycle or negative half cycle detection and judgment circuit 300 is triggered, the V-OCP port will flip to a high level. The control chip only needs to identify the V-OCP terminal level to realize the identification and judgment processing of whether the inverter load current is in a normal, overcurrent or short circuit state.

[0047] In one embodiment, the judgment circuit 300 also includes an OR gate circuit 330, the first input end of the OR gate circuit 330 is connected to the output end of the positive half-cycle judgment unit 310, the second input end of the OR gate circuit 330 is connected to the output end of the negative half-cycle judgment unit 320, and the output end of the OR gate circuit 330 serves as the output end of the judgment circuit 300.

[0048] In one embodiment, the OR gate circuit 330 includes a first diode D1 and a second diode D2, the anode of the first diode D1 is connected to the output end of the positive half-cycle judgment unit 310, the anode of the second diode D2 is connected to the output end of the negative half-cycle judgment unit 320, the cathode of the first diode D1 is connected to the cathode of the second diode D2, and the cathode of the first diode D1 serves as the output end of the judgment circuit 300.

[0049] In this embodiment, the OR gate circuit calculates the overcurrent signal waveforms 3# and 4# output by the positive half-cycle judgment unit 310 and the negative half-cycle judgment unit 320 through the first diode D1, the second diode D2 or the operational amplifier to obtain the overcurrent and short-circuit protection signals, such as Figure 2 As shown in waveform 2#.

[0050] It should be noted that the operational amplifier circuit 200 includes but is not limited to components such as triodes, MOS tubes, operational amplifiers, and other methods of constructing amplifier circuits meet the requirements.

[0051] In one embodiment, the operational amplifier circuit 200 is implemented by an operational amplifier, and the operational amplifier circuit 200 includes a first operational amplifier X1, a first resistor R1 and a second resistor R2, the inverting input terminal of the first operational amplifier X1 is connected to the output terminal of the detection circuit 100 through the first resistor R1, the non-inverting input terminal of the first operational amplifier X1 is connected to the ground, the positive power supply terminal of the first operational amplifier X1 is connected to the positive power supply, and the negative power supply terminal of the first operational amplifier X1 is connected to the negative power supply.

[0052] In one embodiment, the amplification factor of the operational amplifier circuit 200 is determined by the ratio of the first resistor R1 to the second resistor R2.

[0053] In this example, the amplifier circuit is composed of a first operational amplifier X1, a first resistor R1, and a second resistor R2 to form an operational amplifier circuit 200, wherein the amplification factor M1 is determined by the ratio of the second resistor R2 to the first resistor R1, that is:

[0054]

[0055] In this embodiment, the amplification factor M1 is selected as 50 times, and the corresponding ratio of the resistor R2 to R1 is 50. The load signal Vcs is connected to the inverting terminal of the operational amplifier, and the non-inverting terminal of the operational amplifier is grounded. The output terminal of the operational amplifier is the load amplified signal V3, wherein the amplitude of the load amplified signal V3 is equal to the amplification factor M1 multiplied by the load signal, that is:

[0056] V3=M1×Vcs(1.2)

[0057] The voltage peak value corresponding to V3 is 2.1V, and the simulation waveform is as follows Figure 2 shown.

[0058] It should be noted that expression (1.2) refers to the amplitude relationship between signals, and the amplitude of V3 will not exceed the amplitude of the power supply of the operational amplifier.

[0059] In addition, an embodiment of the present invention further provides an inverter overcurrent protection trigger circuit method, the inverter overcurrent protection trigger circuit method comprising:

[0060] According to the sampling current of the inverter, peak values ​​of the positive half-cycle current signal and the negative half-cycle current signal of the sampling current are judged respectively, and an overcurrent signal is output when it is confirmed that the positive half-cycle current signal or the negative half-cycle current signal is in an overcurrent state;

[0061] The overcurrent signal is output to the interrupt pin of the control chip to trigger an interrupt to stop the inverter from working.

[0062] In one embodiment, the amplitude of the sampled current is in the millivolt level, and the purpose is to obtain the load current of the inverter in real time. In order to reduce losses, the amplitude of the signal obtained by sampling is relatively small. Generally, the detection of load current includes but is not limited to resistance sampling, current transformer sampling, etc., and any method that can achieve current sampling meets the requirements.

[0063] It can be seen from the above content that the present invention realizes overcurrent and short-circuit state judgment protection of the inverter by constructing the detection circuit 100, the operational amplifier circuit 200 and the judgment circuit 300.

[0064] The significant advantages of this invention patent:

[0065] (1) The circuit structure is simple, with one operational amplifier and two voltage comparators, and the protection logic is clear;

[0066] (2) Hardware protection circuit, small protection logic execution delay value;

[0067] (3) No need to rely on the complex instruction algorithms of the microprocessor, reducing the amount of code writing and computing resource consumption.

[0068] (4) The judgment circuit 300 described in the present invention judges the signal and is composed of an overload protection judgment unit and a short circuit protection judgment unit. The function of the judgment circuit 300 is to judge whether an overload or short circuit occurs.

[0069] The above-mentioned embodiments of the present invention are merely examples for explaining the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes and modifications can be made based on the above description. It is impossible to list all the embodiments here. Any obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. An inverter overcurrent protection trigger circuit, characterized in that: The inverter overcurrent protection trigger circuit comprises a detection circuit, an operational amplifier circuit and a judgment circuit, wherein the output end of the detection circuit is connected to the input end of the judgment circuit through the operational amplifier circuit; The judgment circuit comprises a positive half-cycle judgment unit and a negative half-cycle judgment unit, and the input end of the positive half-cycle judgment unit and the input end of the negative half-cycle judgment unit are both connected to the output end of the operational amplifier circuit; The positive half-cycle judgment unit is used to output an overcurrent signal when confirming that the positive half-cycle current signal is in an overcurrent state; The negative half-cycle judgment unit is used to output an overcurrent signal when confirming that the negative half-cycle current signal is in an overcurrent state; The judgment circuit outputs the overcurrent signal to the interrupt pin of the control chip to trigger an interrupt to stop the inverter from working.

2. The inverter overcurrent protection trigger circuit according to claim 1, characterized in that: The judgment circuit also includes an OR gate circuit, a first input end of the OR gate circuit is connected to the output end of the positive half-cycle judgment unit, a second input end of the OR gate circuit is connected to the output end of the negative half-cycle judgment unit, and the output end of the OR gate circuit serves as the output end of the judgment circuit.

3. The inverter overcurrent protection trigger circuit according to claim 2, characterized in that: The OR gate circuit includes a first diode and a second diode, the anode of the first diode is connected to the output end of the positive half-cycle judgment unit, the anode of the second diode is connected to the output end of the negative half-cycle judgment unit, the cathode of the first diode is connected to the cathode of the second diode, and the cathode of the first diode serves as the output end of the judgment circuit.

4. The inverter overcurrent protection trigger circuit according to claim 1, characterized in that: The positive half-cycle circuit includes a first voltage comparator, a non-inverting input terminal of the first voltage comparator is connected to the output terminal of the operational amplifier circuit, an inverting input terminal of the first voltage comparator is connected to a first reference voltage, and an output terminal of the first voltage comparator outputs the overcurrent signal.

5. The inverter overcurrent protection trigger circuit according to claim 1, characterized in that: The negative half-cycle circuit includes a second voltage comparator, a non-inverting input terminal of the second voltage comparator is connected to a second reference voltage, an inverting input terminal of the second voltage comparator is connected to the output terminal of the operational amplifier circuit, and an output terminal of the second voltage comparator outputs the overcurrent signal.

6. The inverter overcurrent protection trigger circuit according to claim 1, characterized in that: The operational amplifier circuit includes a first operational amplifier, a first resistor and a second resistor, the inverting input terminal of the first operational amplifier is connected to the output terminal of the detection circuit through the first resistor, the non-inverting input terminal of the first operational amplifier is connected to the ground, the positive power supply terminal of the first operational amplifier is connected to the positive power supply, and the negative power supply terminal of the first operational amplifier is connected to the negative power supply.

7. The inverter overcurrent protection trigger circuit according to claim 6, characterized in that: The amplification factor of the operational amplifier circuit is determined by the ratio of the first resistor to the second resistor.

8. The inverter overcurrent protection trigger circuit according to claim 1, characterized in that: The detection circuit includes a sampling resistor or a current transformer.

9. An inverter overcurrent protection trigger circuit method, characterized in that: The inverter overcurrent protection trigger circuit method comprises: According to the sampling current of the inverter, peak values ​​of the positive half-cycle current signal and the negative half-cycle current signal of the sampling current are judged respectively, and an overcurrent signal is output when it is confirmed that the positive half-cycle current signal or the negative half-cycle current signal is in an overcurrent state; The overcurrent signal is output to the interrupt pin of the control chip to trigger an interrupt to stop the inverter from working.

10. The inverter overcurrent protection trigger circuit method according to claim 9, characterized in that: The amplitude of the sampling current is in the microvolt level or millivolt level.

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