Frequently Asked Questions

Please contact us or one of our distributors for further information on specific products, applications or for sales support or file your request online.

RDFC topology and C2470 products

What is RDFC?
Why is RDFC more energy-efficient than flyback SMPS?
Why does C2470 offer such a good no-load performance?
I need universal input, is RDFC for me?

Why is RDFC claimed to be so safe?
What about system costs?
Why use slow-switching bipolars rather than MOSFETs?
How do I specify the transistor for my application?

What about power factor correction?
What is the maximum frequency that can be used for the power conversion process?
Which functions are digital or analogue?
Why does RDFC offer such low EMI?

Who else offers RDFC?
How does RDFC compare with CCM and DCM?
Do I need specialist design skills to use RDFC?
What power range is covered by CamSemi’s C2470 mixed signal controllers?

Sales and technical support

Does CamSemi offer application reports?
How can I get a design guide or datasheet?
Can I order a demonstrator kit?

PowerBrane technology

Are you still developing PowerBrane?
When will the first PowerBrane products be available?

Quality

Are products RoHS compliant?
Is CamSemi ISO registered?
Are products fully qualified?
Are CamSemi products suitable for medical, military and automotive applications?
How does CamSemi deal with customer complaints?

Q: What is RDFC?
RDFC stands for Resonant Discontinuous Forward Converter – a novel power conversion topology that enables low cost, high efficiency SMPS. The approach is ideal for single rail, high volume consumer applications.

Q: Why is RDFC more energy-efficient than flyback SMPS?
The topology is based on near zero-voltage power switching which minimises the turn-off losses. Efficiencies in excess of 80% and with a no-load consumption of less than 150 mW achievable.

Q: Why does the C2470 offer such a good no-load performance?
CamSemi’s C2470 product family is based on a 3.3 V low power BiCMOS process which ensures that a minimum amount of power is drawn by the RDFC circuit. In addition to this, before going into standby mode, the IC progressively reduces the on-time and increases the off-time to reduce the power consumption and maintain efficiency at low loads.

Q: I need universal input, is RDFC for me?
RDFC offers single rail input making it ideal for products targeted for specific markets or countries. The approach is perfect to replace linear power converters or for manufacturers looking for low cost, single rail SMPS solution for products where universal input is not essential.

Q: Why is RDFC claimed to be so safe?
With no optocoupler or Y cap across the isolation boundary, there is less to fail and cause a problem.

Also the output voltage of the RDFC topology is a ratio of the input voltage determined by the turns ratio of the transformer. As a result, the output cannot rise to damaging or dangerous levels through component failure or a load transient.

As well as the topology being inherently safe, CamSemi C2470 series controller has in-built protection features such as over-temperature, under-voltage and external transistor protection.

Q: What about system costs?
RDFC topology is simpler than flyback, it uses cheaper, bipolar transistor switches compared with MOSFETs and fewer components too: all of which significantly reduces system cost. This enables SMPS performance, that easily meets the needs of ENERGY STAR, EU codes of conduct and other regulatory bodies, but at the price of a linear or less.

Q: Why use slow-switching bipolars rather than MOSFETs?
To save on system costs. System performance does not depend on fast switching, which allows the use of low cost, readily available bipolar transistors rather than MOSFETs.

Q: How do I specify the transistor for my application?
The key parameter is the Vcbo characteristic which is typically 700 V or above for lowline and 1200 V or above for highline applications. CamSemi can provide a list of approved transistors for your application or our applications design team can help further.

Q: What about power factor correction?
RDFC is aimed at applications up to 60 W, whereas power factor correction is only required in most consumer applications at 75 W and above.

Q: What is the maximum frequency that can be used for the power conversion process?
150 kHz but CamSemi recommends operating at 50 to 60 kHz to optimise the system.

Q: Which functions are digital or analogue?
The main control loop is digital, although the bipolar transistor/power switch is controlled via analogue feedback. This loop ensures the transistor is always run with the optimum amount of charge in the base so that it goes off quickly at turn off.

Q: Why does RDFC offer such low EMI?
RDFC is based on a smooth resonant waveform that minimises EMI within the circuit. Whereas with flyback, the hard-switching edges generate voltage transients that cause high levels of EMI – a significant problem that requires additional, costly filtering circuitry for numerous applications.

Q: Who else offers RDFC?
RDFC controller ICs are unique to CamSemi.

Q: How does RDFC compare with CCM and DCM?
CCM and DCM describe how current flows and where energy is stored in the inductor/transformer of a conventional SMPS topology. With RDFC, energy is not intentionally stored in the transformer but it is transferred, just as in a linear transformer. RDFC is a novel approach offering the efficiency, no-load advantages of SMPS but with additional protection features built-in, simpler circuits and at the cost of a linear or less.

Q: Do I need specialist design skills to use RDFC?
CamSemi design guides include easy-to-use look-up tables to speed up the process and power supply designers are amazed at how quickly they can be building their first RDFC solutions.

Compare this with flyback and RCC topologies. Both approaches require more complex power conversion and filtering circuitry, they are time-consuming to design and very specialist skills are needed to optimise circuit performance.

Q: What power range is covered by CamSemi’s C2470 mixed signal controllers?
The first four products in the C2470 family of controllers are aimed at the 1 to 60 W sector. For lowline applications up to 40 W and highline up to 60 W.

Q: Does CamSemi offer application reports?
Yes – application reports are available either from our website or on request.

Q: How can I get a design guide or datasheet?
All design guides and datasheets are available online.

Q: Can I order a demonstrator kit?
Yes – demonstrator kits are available free for qualified recipients only.

Q: Are you still developing PowerBrane?
Yes - CamSemi is actively working on a programme to integrate its innovative controllers with high voltage switches on the same die. To keep updated please register for our news alert service.

Q: When will the first PowerBrane products be available?
CamSemi is worked intensively on integrated products but is unable to release any further information into the wider market on product introduction timescales. Please register for our news alert service to keep updated on our progress.

Q: Are products RoHS compliant?
Yes - all CamSemi products have been independently tested to ensure complete compliance to the latest RoHS directive. Test reports are available here.

Q: Is CamSemi ISO registered?
Yes - CamSemi was certified by BSI to ISO9001:2000 quality standard in March 2006 and to ISO14001:2004 for its environmental management system in March 2008.

Q: Are products fully qualified?
All products are fully tested and qualified in line with JEDEC standards, before being released for production. Qualification reports are available online.

Q: Are CamSemi products suitable for medical, military and automotive applications?
Products are not currently qualified for use in these markets.

Q: How does CamSemi deal with customer complaints?
CamSemi has a defined system to track customer feedback or product returns. The system assigns a Return Materials Authorisation (RMA) number to each issue within 24 hrs and a Quality Engineer is appointed as a focal point during the investigation. Reports are then presented to the customer on completion, and the target is to reply back within 7 days of receiving returned product.