Diagram of 1200W sine wave inverter example-EEWORLD

Collect

We know that in many inverter situations, low-voltage DC power supplies are converted into high-voltage AC power supplies, so a step-up is required to complete this change. This time, we are still discussing the use of high-frequency methods for inverters. The use of high-frequency methods has many advantages over the industrial frequency methods: high conversion efficiency, extremely low no-load current , light weight, small size, etc. Some people may say that the industrial frequency is tough and impact-resistant, and I agree with this point very much. However, it should be pointed out that if the high-frequency is well done, it will not lose to the industrial frequency at all. This has been confirmed by our company's products and the shipment of TDS2285 . So, let's take a look at the performance of the TDS2285 chip in this system!

DC-DC boost section:

This design uses DC24V input. In order to ensure the output AC220, in this link, the DC-DC boost part needs to at least boost the DC24V to 220VAC*1.414=DC311V, so that a stable AC220V can be output on the basis of 311V . In order to achieve this goal, we use the very familiar push-pull circuit TOP to do the DC-DC conversion. The circuit diagram is as follows:

In the circuit diagram , GR and GL are two push-pull PWM signals, which drive high-current MOSFETs composed of two RU190N08 in parallel . The transformer uses EE55 , and the diode is RHRP1520 . In fact , RHRP860 can be used. I just don't have 860 , so I use 15120. Set the output no-load high voltage to 380V, so the transformer can be wound with 3+3 : 49T. For the specific winding method, please search the old posts in the forum, many of which are very detailed.

Now that we have DC380V , are we still worried that we won’t be able to come up with AC220 ?

Let's talk about the DC-AC part. In this part, the circuit is also very simple. Please see the circuit below:

As can be seen from the figure above, the DC-AC part is composed of an H- bridge circuit, and a pure sine wave is obtained after filtering by L1, L2 and C22 . The output waveform is shown in the figure below :

LS2 forms the output overcurrent detection circuit , and R22 forms the H- bridge short-circuit protection circuit. So far, the power part circuit (including DC-DC, DC-AC ) is fully given. Let's see if it is very simple. Now let's take a look at the small signal circuit that controls the normal operation of these power components.

You can click to enlarge it. I'll keep you in suspense. I'm sure you can understand how this part works. If you have any questions, please ask below. I and the experts in the forum will answer them one by one.

Finally, I will analyze how to debug TDS2285 and some minor problems encountered in it!

Many people can't wait to use a general-purpose board to make a basic circuit after getting the chip . It turns out that this is feasible, but it can also encounter various problems. As follows:

1. After the chip is powered on, the LED on pin 5 flashes, and there is no output on pins 6 and 8 of the chip . This problem is most likely to occur. At this time, the LED flashes, indicating that the chip has entered the protection state, that is, the fault alarm mode. The buzzer connected to pin 9 is synchronized with this state . The LED indication state represents different faults or protection modes. According to the description in the specification book:

LED :

Indicates the working status of the inverter. When the output is always 5V , the LED is always on and the inverter is working normally. When the battery voltage is overvoltage or undervoltage, the indicator light flashes once every 1 second or flashes 3 times every 1S . When the output AC is overcurrent or short-circuited, the indicator light flashes once every 0.5 seconds. When overvoltage protection occurs, the LED flashes 3 times every 1S . When undervoltage protection occurs, the LED flashes once every 1S .

Since the alarm status of the LED pin and the BEL (buzzer) pin are synchronized, the specification has the following description:

BEL :

Fault alarm, a buzzer is driven on this pin, and in conjunction with the status on the LED pin, when the battery voltage input is overvoltage or undervoltage, the buzzer and the LED indicator will alarm once every 1 second or alarm 3 times every 1S . When the output AC is overcurrent or short-circuited, the buzzer and the LED indicator will alarm once every 0.5 seconds. When overvoltage protection occurs, the buzzer will alarm 3 times every 1S . When undervoltage protection occurs, the buzzer will alarm once every 1S .

For this problem, as long as the voltage on pin 13 ( VBAT ) is kept within the range of 0.9V-1.3V , the low voltage and over voltage protection can be prevented from taking effect, and the chip will not enter the over-voltage or under-voltage protection state.

For 12V battery input, as long as the voltage divider resistor is 100K on the upper side and 10K on the lower side, the over-voltage and under-voltage range is 10.5-14.5V. For 24V system, as long as the voltage divider resistor is 100K on the upper side and 4.7K on the lower side , the over-voltage and under-voltage range is 22.5-29.5V, which meets the design requirements very well.

2. If the LED still flashes after following the above solution , it may be in the short circuit protection state, such as flashing once every 0.5S . Please check the voltage on pin 11 ( SD ) in detail. If the voltage is lower than 2.5V , it will enter the protection state. In the case of debugging, you can disconnect the external circuit and connect the pin directly to 5V through a 2.4K resistor . It should be noted that once the protection occurs during the operation of the TDS2285 chip, the chip can only output SPWM after powering off the chip and then powering it on again , because the protection is locked and will not restart automatically!!!

3. After the circuit is completed, it runs normally without load and can output 220V sine wave, but protection occurs when there is load , and the LED flashes once every 0.5S. This problem occurs because the short-circuit protection design is too sensitive. The MOSFET on the H -bridge generally needs to reserve more than 4 times the current capacity, so that the current detection value of the short-circuit protection can be amplified. At this time, careful settings and multiple adjustments are required to ensure that the whole machine can operate reliably under the impact of large loads and will not burn out power devices such as MOSFET .

4. When debugging TDS2285 , do not pass 380V high voltage to the H bridge first, use low voltage power supply first, such as 12V , check the static current, if it exceeds 1MA , then there is a circuit problem, and the places that need to be checked in detail are the optocoupler drive circuit and whether the MOSFET is broken. If only one part is broken, then the optocoupler, MOSFET, and the G- pole resistor of the MOSFET need to be replaced, regardless of whether they are good or bad, so that you will not take detours when debugging, because in many cases, you replace the broken parts, and pass high voltage, and the other parts break inexplicably. Well, I will write here first, it is not yet finalized, and it will be released step by step in the future, and spy photos of the machine in operation, such as the super impact load experiment with air conditioning, will be released.

I would like to thank the Admin for thinking highly of me and encouraging me to post a contest entry. I wrote this article shamelessly. Since I did not write the principle of the signal control part in detail, I hope that those who read this post and have a strong interest in sine wave inverters will participate in the discussion. In this way, everyone who sees this post will be able to experience it and express their feelings! I sincerely hope that all the masters and masters will give us correct opinions and guidance, and we will continue to improve!

Reference address：Diagram of 1200W sine wave inverter example

Previous article：The birth of DIY full-bridge modified sine wave inverter
Next article：How to Select Power Electronics in Solar Inverters

Popular Resources
Popular amplifiers