Mornsun & ON-Semi Develop Solar Inverter Solutions

21st January 2020

Mornsun partners with ON Semiconductor
to put IGBT Drive Circuits at the heart of Solar Power Inverter Design

To support developers of solar power inverters, ON Semiconductor and Mornsun have partnered their QA151 DC-DC Converter with ON Semiconductor’s driver ICs & transistors in an Insulated Gate Bipolar Transistors (IGBT) gate driver demo board.

To meet the increasing demand for renewable energy around the world, the two companies have collaborated on a development board to support design engineers evaluate the effectiveness of an IGBT-based power system.
The primary focus of commercially available alternative energy technology today is solar photovoltaic (PV) power generation, which harnesses the energy of the sun and converts it into usable electricity.

Solar Power Inverter - A Typical Solar PV Power Generation System @ Relec Electronics Ltd
Figure 1: A typical solar PV power generation system

Figure 1 shows a typical solar PV power generation system. Solar PV arrays generate electricity from sunlight, which is converted from direct current (DC) to alternating current (AC) using an inverter. This AC Power then is fed into the grid for home or business use or, when not directly required, is used to charge batteries via a bi-directional energy storage inverter, thus making power available not just during daylight hours.

In centralised or distributed electricity generation system networks, there is always a DC-AC inverter at the heart of solar PV system. The inverter makes use of IGBT full-bridge circuits to convert the DC energy into a useable AC waveform.

Solar Power Inverter - Block diagram of a typical Distributed Inverter @ Relec Electronics Ltd
Figuire 2: Block diagram of a typical Distributed Inverter

Figure 2 is an example of a typical inverter system. A wide input DC-DC converter (Mornsun’s PV60-27D1215) generates stable 12V and 15V rails for the control electronics. The DC bus feeding the converter can come from multiple PV panels with input voltages up to 1100V DC. The DC-DC converters require isolation voltages in excess of 4000V AC in order to maintain appropriate safety levels and to maintain the safe and reliable operation of the control system.

The IGBT Drive Board

The IGBT drive circuit is used to isolate, transmit and amplify control signals which drive the main power transistors. There are specific requirements for a safe and reliable IGBT driver which system design engineers should consider:

  • IGBT operating characteristics dictate that the junction capacitor (Cge) needs to be charged/discharged when the IGBT is turned on or off. Therefore, the gate drive DC/DC power supply needs to have asymmetrical positive and negative output voltages, and meet the requirements of transient charge and discharge current of the junction capacitance, to ensure that the IGBT can be turned on and off quickly.
  • When the high DC voltage is inverted to an AC voltage, the IGBT generates a high frequency and high amplitude interference signals during fast turn-on and turn-off. The drive circuit needs to have high transient immunity to cope with these disturbances, a high isolation voltage, and low isolation capacitance, to ensure reliable operation and avoid common-mode interference signal conduction to the system control board.
  • The high current, high voltage operating environment of the IGBT causes large temperature rises inside the system during inversion. As a result, the gate drive DC/DC power supply needs to have a high operating temperature range.

ON Semiconductor have developed a gate drive demonstration board for system designers developing high power solar inverters featuring the Mornsun QA151 combined DC-DC converter and gate drive.

Development support

Solar Power Inverter - Circuit diagram of the ON Semiconductor driver demo board, with Mornsun’s QA151 power module @ Relec Electronics Ltd
Figure 3: Circuit diagram of the ON Semiconductor driver demo board, with Mornsun’s QA151 power module.

The Mornsun QA151 is a DC-DC Converter specifically designed for IGBT drivers. It has 2 asymmetric outputs (+15/-8.0V DC) with very low input to output capacitance, making it the ideal DC DC Converter to power ON Semiconductor’s FOD3120SD driver IC and 2SC5569 and 2SA2016 transistors.

The QA151 also has a wide operating temperature range from -40 to +105℃ and is supplied in a compact, internally-potted 7-pin SIP case (19.5 x 9.8 x 12.5mm, saving valuable board real estate on space-constrained solar inverter designs.).

A high-quality isolation transformer provides up to 3000Vac. The QA151’s isolation capacitance is only 6pF, ensuring excellent interference immunity for the demo board. Additionally, with an output current up to 120mA and the ability to drive 200uF capacitive loads, meets the general power requirements for power IGBT bridge circuits

The Mornsun QA151 DC-DC Converter is available now from Relec Electronics. The specialist in power conversion and display products supplies standard products from the industry’s leading manufacturers but can also go beyond this function. Its team of skilled engineers can apply expert understanding of customers’ applications and specifications to source the most appropriate products or to customise a product or feature for application-specific solutions.

Solar Power Inverter - Mornsun's QA151 Series
Mornsun’s QA151 Series DC DC Inverter

Relec Electronics has worked closely with our key suppliers for over 40 years, specialising in many industries; automotive, industrial, defence & now Solar Power Inverters.
We have a team of dedicated engineers ready to support you throughout the design process. We also carry stock of all standard modules and accessories for next day delivery.

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