Research and Design of Solar Products

-

                                  SOLAR CHARGE CONTROLLERS
 

























Circuit 1  - On/Off                                                                                  
Circuit 2 - PWM



                                                       
Circuit 3 - MPPT
 
While working at Nice Electrical and Electronics Industries Limited as part-time researcher and circuit developer, I have designed Solar Charge Controllers of different capacity (15A to 50A).

The charge controller is controlled by a 16F690 PIC microcontroller. The microcontroller first senses the input voltage from the solar panel. If the voltage is above 12.6V and below 19V, charging takes place.

Circuits 1, 2 and 3 share similar hardware but the control methodology is different.

The MOSFET is configured as a high-side switch. A charge-pump circuit is set up that boosts the input voltage to a voltage between 24V and 36V (depending on input voltage). The microcontroller provides the PWM signal to the boost stage. The boosted voltage (between 24V and 36V) is used to drive the high-side MOSFET.

Circuit 1 is simple on/off type series pass charge controller. When voltage is between 12.6V and below 19V, the microcontroller turns on the MOSFET and the voltage from the panel is provided to the battery via the MOSFET. The battery voltage is monitored and when the voltage is above 14V, the charging is stopped until voltage falls below 13.7V.

Circuit 2 is PWM based. The microcontroller generates the PWM signal depending on input voltage. The MOSFET is driven based on the PWM signal and the battery is charged. When the battery reaches 14V, charging is not stopped. Instead, duty cycle of PWM is reduced. This acts like "trickle" charging, to keep the battery fully charged.

Circuit 3 is MPPT (Maximum Power Point Tracking) based. The microcontroller generates the PWM signal and drives the MOSFET accordingly, while adjusting duty cycle to "search" for the maximum power point to maximize charging current. The circuit currently works and charges the battery although the maximum power point tracking isn't great. I am going to have to further work on this circuit to make it perfect.

_________________________________________________________________________________________________________________________


                        300W 12VDC to 220VAC SMPS-based Solar Inverter


 
























Circuit 1
Circuit 2                         


While working at Nice Electrical and Electronics Industries Limited as part-time researcher and circuit developer, I also designed Solar Inverters of different capacity.

Circuits 1 and 2 are both DC-AC converters. 12V DC is first stepped up to 240VDC using a push-pull converter. SG3525 generates the PWM signal. The high voltage DC is kept regulated.

In Circuit 1, a 50Hz auxiliary transformer is used for output voltage sensing and the voltage output from the 50Hz auxiliary transformer is fed to the SG3525 which uses it to keep the output voltage constant.

In Circuit 2, a voltage feedback loop is designed using TL431 and opto-coupler, eliminating the need for a 50Hz auxiliary transformer.

The high voltage DC is then converted to AC by a full-bridge stage using 4 MOSFETs. The 50Hz signals are generated by the 16F690 microcontroller. The signals are fed into high-low side MOSFET drivers L6385E using opto-couplers so that the low-voltage side (where the microcontroller is) is isolated from the high-voltage side (where the drivers and MOSFETs are). The drivers drive the MOSFETs according to the signals generated by the microcontroller. The output voltage is kept constant as the high-voltage DC bus is regulated by the SG3525.

The microcontroller also senses the battery voltage and shuts off the inverter when battery voltage falls below 10.8V, providing low-voltage protection. The load current is also sensed by the microcontroller to provide over-load protection.

All MOSFETs are mounted on heatsinks for heat dissipation. The transformer, using ETD39 core, was wound by me as tailor-made wound ferrite transformers are not available in Bangladesh.

The entire circuit from concept to design to implementation was done by me as nothing ready-made is available here!

Comments

Post a Comment

Popular posts from this blog

Using the TLP250 Isolated MOSFET Driver - Explanation and Example Circuits

-
Image
I’ve already shown how to drive an N-channel MOSFET (or even an IGBT) in both high-side and low-side configurations in a multitude of ways. I’ve also explained the principles of driving the MOSFETs in these configurations. The dedicated drivers I’ve shown so far are the TC427 and IR2110. Some people have requested me to write up on MOSFET drive using the very popular TLP250. And I’ll explain that here. The TLP250, like any driver, has an input stage, an output stage and a power supply connection. What’s special about the TLP250 is that the TLP250 is an optically isolated driver, meaning that the input and output are “optically isolated”. The isolation is optical – the input stage is an LED and the receiving output stage is light sensitive (think “photodetector”). Before delving any further, let’s look at the pin configuration and the truth table. Fig. 1 - TLP250 Pin Configuration Fig. 2 - TLP250 Truth Table Fig. 1 clearly shows the input LED side and the receiving photodetector as well
Read more

Using the SG3525 PWM Controller - Explanation and Example: Circuit Diagram / Schematic of Push-Pull Converter

-
Image
PWM is used in all sorts of power control and converter circuits. Some common examples include motor control, DC-DC converters, DC-AC inverters and lamp dimmers. There are numerous PWM controllers available that make the use and application of PWM quite easy. One of the most popular of such controllers is the versatile and ubiquitous SG3525 produced by multiple manufacturers – ST Microelectronics, Fairchild Semiconductors, On Semiconductors, to name a few. SG3525 is used extensively in DC-DC converters, DC-AC inverters, home UPS systems, solar inverters, power supplies, battery chargers and numerous other applications. With proper understanding, you can soon start using SG3525 yourself in such applications or any other application really that demands PWM control. Before going on to the description and application, let’s first take a look at the block diagram and the pin layout. Pins 1 (Inverting Input) and 2 (Non Inverting Input) are the inputs to the on-board error amplifier. If you a
Read more

N-Channel MOSFET High-Side Drive: When, Why and How?

-
Image
I had previously shown how to drive N-channel MOSFETs in low-side configuration. You can find the tutorial here: http://electel.blogspot.com/2016/12/low-side-mosfet-drive-circuits-and_23.html I’ve been requested to write a tutorial/article regarding high-side MOSFET drive. So, here I’ll talk about N-channel MOSFET high-side drive. Let’s first look at the common low side configuration.  Fig. 1 - N-channel MOSFET configured as low-side switch Now let’s look at a MOSFET configured as a high-side switch. Fig. 2 - N-channel MOSFET configured as high-side switch You can quite easily see the difference between the high-side configuration and the low-side configuration. In the low-side configuration, the load is connected between the drain and +V, while the source is connected to ground. Thus, the gate drive is referenced to ground. So by applying a voltage of >7V (for Power MOSFETs) or >4V (for Logic Level MOSFETs), the MOSFET can be fully turned on. Now let’s talk about the high-side c
Read more