Auxiliary control method and circuit for improving load adaptability of EG8015 inverter circuit

Abstract

The invention discloses an auxiliary control method and circuit for improving load adaptability of an EG8015 inverter circuit, and the method comprises the following steps: collecting the current during the operation of a load through a current sampling unit, transmitting the current to an MCU (Microprogrammed Control Unit) U5, judging whether the current collected by the current sampling unit exceeds a preset current threshold value or not through the MCU U5, and if yes, judging whether the current collected by the current sampling unit exceeds the preset current threshold value; if not, a voltage effective value is calculated according to the sampling voltage, voltage zero-crossing phase locking is carried out, after phase locking is completed, a PWM overcurrent protection value is set according to a sine wave period, and then sine wave SPWM pulses are adjusted by the EG8015 control unit; the voltage effective value is calculated according to the sampling voltage output by the voltage sampling unit, whether the voltage effective value exceeds a preset voltage threshold value or not is judged, if yes, the SPWM is turned off after the set time is delayed, and meanwhile the SPWMEN end of the EG8015 control unit is set to be low. According to the method, the load carrying capacity of the inverter can be higher, the load adaptability is better, different load types can be considered, and the inverter can be protected when an inductive load is handled.

Description

Technical Field

[0001] The invention relates to an inverter control circuit, and in particular to an auxiliary control method and circuit for improving the load adaptability of an EG8015 inverter circuit. Background Art

[0002] In the prior art, the EG8015 is often used to design and control the inverter circuit. The EG8015 uses the peak current method to sample the output current. The circuit structure is as follows: Figure 8 As shown in the figure: the current on RS1 is filtered by R21 and C20, and then sent to the current feedback and protection circuit inside the 6-pin (IFB) for processing. The maximum current limit current set by IFB is: Imax=128mV / Rs, Rs is Rs1 in the figure, which is the current sampling resistor. When Rs is selected as 0.02Ω, the maximum current limit current can be obtained as Imax=128mV / 0.02Ω=6.4A, which is more suitable for 1KW inverter applications. For different power applications, you can refer to the above formula for calculation, select sampling resistor values ​​of different resistance values ​​or adjust the amplification factor of the op amp. When applied, the IFB pin cannot be suspended, otherwise abnormal phenomena will occur. If some occasions, such as when the startup current is relatively large and the time is relatively long, it is not suitable for the application of this function, and the IFB pin can be grounded.

[0003] In actual applications, the current limiting protection value is set according to the requirements of the technical specification: using a fixed resistor divider, the setting value is fixed and cannot be adjusted at any time according to the characteristics of the load current. Therefore, for rectifier loads or loads with low power factors, due to the high peak current and short current conduction time, if the current limiting current value is set low, the load adaptability is poor and the corresponding load cannot be carried well; at the same time, if the current limiting value is increased in order to adapt to more loads and improve load adaptability, the overload protection is also improved. For general loads, the overload current limiting protection current is larger and the protection is slower, so it is easy to cause damage to the inverter and the reliability is poor; in addition, the EG8015 chip is not designed with bus overvoltage protection, and there is a lack of effective protection mechanism for the increase of bus voltage caused by inductive loads, which makes it easy to cause the bus voltage to be too high and damage the inverter when carrying such loads. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide an auxiliary control method and circuit that can make the inverter have stronger load capacity, better load adaptability, take into account different load types, and protect the inverter when dealing with inductive loads, in view of the shortcomings of the existing technology.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions.

[0006] An auxiliary control method for improving the load adaptability of an EG8015 inverter circuit is implemented based on an MCU controller U5, a current sampling unit, a voltage sampling unit and an EG8015 control unit. The method includes the following processes: using the current sampling unit to collect the current when the load is running and transmitting it to the MCU controller U5, the MCU controller U5 determines whether the current collected by the current sampling unit exceeds a preset current threshold value, if not, calculating the voltage effective value according to the sampled voltage and performing voltage zero-crossing phase locking, setting the PWM overcurrent protection value according to the sine wave cycle after the phase locking is completed, and then adjusting the sine wave SPWM pulse by the EG8015 control unit; calculating the voltage effective value according to the sampled voltage output by the voltage sampling unit, determining whether the voltage effective value exceeds the preset voltage threshold value, if so, turning off the SPWM after a delay setting time, and setting the SPWM_EN terminal of the EG8015 control unit to a low level.

[0007] Preferably, the voltage sampling unit is a BUS voltage sampling unit.

[0008] Preferably, if the MCU controller U5 determines that the current collected by the current sampling unit exceeds a preset current threshold, the SPWM is turned off after a set delay time, and the SPWM_EN terminal of the EG8015 control unit is set low.

[0009] Preferably, the following process is also included: judging whether the SD terminal signal of the EG8015 control unit is at a high level, if so, stopping PWM increase after a high level delay of 1S, turning off SPWM after a high level delay of 2S, and setting the SPWM_EN terminal of the EG8015 control unit to a low level.

[0010] Preferably, when it is determined that the voltage effective value exceeds a preset voltage threshold, the SPWM is turned off after a delay of 20 ms.

[0011] Preferably, when it is determined that the current collected by the current sampling unit exceeds a preset current threshold, the SPWM is turned off after a delay of 20 ms.

[0012] An auxiliary control circuit for improving the load adaptability of an EG8015 inverter circuit, the circuit comprises an MCU controller U5, a current sampling unit, a voltage sampling unit and an EG8015 control unit, and the circuit is used to implement the above-mentioned method.

[0013] In the auxiliary control method for improving the load adaptability of the EG8015 inverter circuit disclosed in the present invention, the sine wave current limit line is dynamically adjusted so that the inverter limits the current value according to the characteristics of the load current under safe conditions, so that the inverter has a stronger load capacity and better load adaptability; at the same time, the present invention adds a protection mechanism for the bus BUS voltage, which can well protect the inverter when dealing with inductive loads; furthermore, the present invention adds an adjustment function for overcurrent protection, adjusts the protection current value according to the sine angle of the sine wave, takes into account different load types, improves the load adaptability, and the present invention can better adapt to rectifying loads. Since the current conduction time of the rectifying load is short, the device increases the limit of the conduction current, thereby increasing the load current, and can adapt to higher-power rectifying loads. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is the schematic diagram of the EG8015 control circuit;

[0015] Figure 2 This is the schematic diagram of the internal comparator of EG8015;

[0016] Figure 3 This is the schematic diagram of the auxiliary control circuit;

[0017] Figure 4 This is the normal operating load current curve after adopting auxiliary control;

[0018] Figure 5 This is the linear load overpower current curve after auxiliary control is adopted;

[0019] Figure 6 This is the rectifier load current curve after auxiliary control is adopted;

[0020] Figure 7 This is the short-circuit protection circuit schematic of the EG8015 control unit;

[0021] Figure 8 This is the schematic diagram of the peak current sampling circuit of the EG8015 control unit;

[0022] Fig. 9 A flowchart of the auxiliary control method. DETAILED DESCRIPTION

[0023] The present invention is described in more detail below with reference to the accompanying drawings and embodiments.

[0024] The present invention discloses an auxiliary control method for improving the load adaptability of the EG8015 inverter circuit. Fig. 9 The method is implemented based on the MCU controller U5, the current sampling unit, the voltage sampling unit and the EG8015 control unit. The method includes the following process:

[0025] The current sampling unit is used to collect the current when the load is running and transmit it to the MCU controller U5. The MCU controller U5 determines whether the current collected by the current sampling unit exceeds the preset current threshold. If not, the voltage effective value is calculated according to the sampled voltage and the voltage zero-crossing phase is locked. When the phase lock is completed, the PWM overcurrent protection value is set according to the sine wave cycle, and then the EG8015 control unit adjusts the sine wave SPWM pulse;

[0026] The voltage effective value is calculated according to the sampled voltage output by the voltage sampling unit to determine whether the voltage effective value exceeds the preset voltage threshold. If so, the SPWM is turned off after a delay setting time, and the SPWM_EN terminal of the EG8015 control unit is set low.

[0027] In the above method, by dynamically adjusting the sine wave current limit line, the inverter is able to limit the current value according to the characteristics of the load current under safe conditions, so that the inverter has a stronger load carrying capacity and better load adaptability; at the same time, the present invention adds a protection mechanism for the bus voltage BUS, which can well protect the inverter when dealing with inductive loads; furthermore, the present invention adds an adjustment function for overcurrent protection, adjusts the protection current value according to the sine angle of the sine wave, takes into account different load types, and improves the load adaptability. Specifically, after using auxiliary control, the normal operating load current (AC voltage, current limit line, load current) curve is as follows: Figure 4 As shown, the linear load overpower-operating load current (AC voltage, current limit line, load current) curve is as follows Figure 5 As shown, the rectifier load-operating current (AC voltage, current limit line, load current) curve is as follows Figure 6 As shown, the present invention can better adapt to rectifying loads. Since the current conduction time of the rectifying load is short, the device increases the limit of the conduction current, thereby increasing the load current, and can adapt to rectifying loads with higher power.

[0028] As a preferred embodiment, the voltage sampling unit is a BUS voltage sampling unit.

[0029] See also Fig. 9 In this embodiment, if the MCU controller U5 determines that the current collected by the current sampling unit exceeds the preset current threshold, the SPWM is turned off after a delay of a set time, and the SPWM_EN terminal of the EG8015 control unit is set low. Further, when it is determined that the current collected by the current sampling unit exceeds the preset current threshold, the SPWM is turned off after a delay of 20ms.

[0030] In a preferred embodiment of the present invention, the above method also includes the following process: determine whether the SD terminal signal of the EG8015 control unit is at a high level. If so, stop PWM increase after a high level delay of 1S, turn off SPWM after a high level delay of 2S, and set the SPWM_EN terminal of the EG8015 control unit to a low level.

[0031] As a preferred manner, when it is determined that the voltage effective value exceeds a preset voltage threshold, the SPWM is turned off after a delay of 20ms.

[0032] On this basis, the present invention also discloses an auxiliary control circuit for improving the load adaptability of the EG8015 inverter circuit, such as Figures 1 to 3 As shown, the circuit includes an MCU controller U5, a current sampling unit, a voltage sampling unit and an EG8015 control unit, and the circuit is used to implement the method described above.

[0033] Specifically, the EG8015 control unit of this embodiment has an output short-circuit protection function, and the short-circuit protection time is less than 10mS. When an output short circuit occurs, EG8015 turns off all power MOSFETs to make the output voltage reach a low level. Once entering the short-circuit protection, EG8015 will release and reopen the power MOSFET tube after 10S to judge the short-circuit protection situation. If the short-circuit protection event still exists, EG8015 will turn off all power MOSFETs to make the output voltage reach a low level and wait for 10S to release again. If the continuous release times accumulate to 5 times and there is still abnormal operation, EG8015 will completely shut down the output of the SPWM module, and the system needs to be powered on again or reset to release.

[0034] In practical applications, the short-circuit protection circuit structure of EG8015 is as follows: Figure 7 As shown, when setting the short-circuit current protection value, the following calculation formula is provided for reference design:

[0035] The first step is to calculate the short-circuit protection reference voltage value:

[0036]

[0037] Step 2: Calculate the short-circuit protection current:

[0038]

[0039] The auxiliary control method and circuit disclosed in the present invention for improving the load adaptability of the EG8015 inverter circuit are compared with the prior art. After using the auxiliary control, the load current signal is as follows: Figures 4 to 6As shown, the present invention dynamically adjusts the sinusoidal current limit line so that the inverter limits the current value according to the characteristics of the load current under safe conditions, thereby making the inverter have stronger load carrying capacity and better load adaptability, thereby better meeting application requirements.

[0040] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the technical scope of the present invention should be included in the scope of protection of the present invention.

Claims

1. An auxiliary control method for improving the load adaptability of the EG8015 inverter circuit, characterized in that: The method is implemented based on the MCU controller U5, the current sampling unit, the voltage sampling unit and the EG8015 control unit, and the method includes the following processes: The current sampling unit is used to collect the current when the load is running and transmit it to the MCU controller U5. The MCU controller U5 determines whether the current collected by the current sampling unit exceeds the preset current threshold. If not, the voltage effective value is calculated according to the sampled voltage and the voltage zero-crossing phase is locked. When the phase lock is completed, the PWM overcurrent protection value is set according to the sine wave cycle, and then the EG8015 control unit adjusts the sine wave SPWM pulse; The voltage effective value is calculated according to the sampled voltage output by the voltage sampling unit to determine whether the voltage effective value exceeds the preset voltage threshold. If so, the SPWM is turned off after a delay setting time, and the SPWM_EN terminal of the EG8015 control unit is set low.

2. The auxiliary control method for improving the load adaptability of the EG8015 inverter circuit as claimed in claim 1, characterized in that: The voltage sampling unit is a BUS voltage sampling unit.

3. The auxiliary control method for improving the load adaptability of the EG8015 inverter circuit as claimed in claim 1, characterized in that: If the MCU controller U5 determines that the current collected by the current sampling unit exceeds the preset current threshold, the SPWM is turned off after a set delay time, and the SPWM_EN terminal of the EG8015 control unit is set low.

4. The auxiliary control method for improving the load adaptability of the EG8015 inverter circuit as claimed in claim 1, characterized in that: It also includes the following process: judging whether the SD terminal signal of the EG8015 control unit is at a high level, if so, stopping PWM increase after a high level delay of 1S, turning off SPWM after a high level delay of 2S, and setting the SPWM_EN terminal of the EG8015 control unit to a low level.

5. The auxiliary control method for improving the load adaptability of the EG8015 inverter circuit as claimed in claim 1, characterized in that: When it is determined that the voltage effective value exceeds the preset voltage threshold, the SPWM is turned off after a delay of 20ms.

6. The auxiliary control method for improving the load adaptability of the EG8015 inverter circuit as claimed in claim 3, characterized in that: When it is determined that the current collected by the current sampling unit exceeds the preset current threshold, the SPWM is turned off after a delay of 20ms.

7. An auxiliary control circuit for improving the load adaptability of the EG8015 inverter circuit, characterized in that: The circuit includes an MCU controller U5, a current sampling unit, a voltage sampling unit and an EG8015 control unit, and the circuit is used to implement the method described in any one of claims 1-6.

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