Recession, Jobs, and Business Ethics

There used to be a saying: to launch a power supply company you need to have a two-car garage and one car. This is sort of how Todd Products, where I have worked for 11 years, was launched. Paul Todd himself was an engineer and an inventor. It was really nice to work for a company where a president could walk into your cubical and discuss the electronic circuits with you. As an engineer himself he understood that experienced engineers are holders of important expertise and are not commodity-- you get a drop in business, you lay them off; you get more business, you hire some more. Another example of engineer-entrepreneur for whom I had an opportunity to work is Richard Blake -- the founder of Transistors Devices. I feel it is always refreshing to work for a company whose owner could argue about the circuits and not just financial reports. In general, in the past, companies used to be owned by someone -- an entrepreneur, an inventor, an engineer, etc. -- who devoted his/her life to the company and cared about its long term growth. Now most of the companies are owned by shareholders, which means by everyone and by nobody. They are controlled by a board of directors who seem to care only about the bottom line, and who begin what they call “downsizing” as soon as they see a drop in business.

Last week’s issue of The Jewish Press featured an article, “The Media's Madoff Moment” by A.H. Foxman. It describes a story about a 1995 fire in a textile plant, Malden Mills, that employed 2,400 people. The fire destroyed three of the four factory buildings and caused $500 million in damage. Two days later Aaron Feuerstein, an Orthodox Jew who owned the company and who followed Biblical values in his business, announced that all his employees will be paid their full salaries. He also gave $80,000 in gifts to charitable organizations, as he did every holiday season. Feuerstein ended up paying full wages to his idle employees for up to four months while the plant was rebuilt. Whatever became nowadays of business owners with a human face? I was lucky to keep my job during the recession, but during the worst of it, unemployment rates of all engineers exceeded 5% and overall jobless rates were 10%. If the companies who have cash in a bank or enough assets to get loans tried to keep their employees in spite of the losses and let them do some R&D for example, they might wind up getting out of recession sooner and stronger. The people who keep getting their paychecks would keep buying things, which would stimulate the manufacturing and job growth better than unnatural injections in the form of the government’s “stimulus plans.” And the old employees who know your business would contribute more effectively than new ones who need to go through a learning curve.

Power Supply Efficiency and Power Factor: Regulations Update

The U.S. Environmental Protection Agency (EPA) has recently announced that effective December 31, 2010, external adapters will no longer be eligible for the Energy Star label. The main reason for this move is in 2008 a mandatory federal minimum efficiency standard went into effect for adapters, mandating basically the same Energy Star performance level.

Last month the ENERGY STAR also published its Draft 3 revision to the proposed criteria for LED lamps, which can be screw into standard lamp sockets to replace incandescent bulbs. To earn the ENERGY STAR logo the LED lamp should have power factor ≥ 0.70. Of course, Energy Star is a voluntary program. However, chances are their requirements will be eventually incorporated in a federal standard. Also, Europe already requires lighting PF>0.9. These developments will certainly cause LED lamps manufacturers to use active power factor correction (PFC) circuits for LED drive. Given the efficiency and size requirements, it's likely that the SMPS designers would also have to use other techniques such as bridgeless PFC rectifiers and synchronous rectification.

"True" Bridgeless PFC Claims Power Supply Efficiency Increase

I am going to discuss Dr.Slobodan Cuk article entitled “The True Bridgeless PFC Converter Achieves Over 98% Efficiency, 0.999 Power Factor”. It was featured in the July issue of Power Electronics Technology Magazine. The article describes the latest invention of Dr.Cuk aimed at eliminating input bridge rectifier from the offline PFC power supplies and thus increasing their efficiency and power factor.
The bridgeless PFC circuits were known before. The diagram below compares Dr.Cuk’s circuit with a different circuit described in ST’s App Note 1606.

The Dr.Cuk approach is certainly novel and very interesting, just like probably all of his converter circuits. However, I believe the above article contains some exaggerations more suitable for advertising than for a technical paper.

For example, the author says: “This method also leads to a rather unusual converter topology consisting of three switches only: one controllable switch S and two passive current rectifier switches CR1 and CR2”. He also claims: “…The odd number of switches, three, is a distinctive characteristic of this converter with respect to all conventional switching converters…” However, later he admits: “…At present, a single MOSFET implementation is not possible due to built-in body-diode, so that switch S must be implemented by use of the two MOSFET devices connected in series at their sources and driven by a common floating gate drive circuit…” So, in reality, the switch S must consist of two real switches and overall there are still four switches, not three. When the power switch S in ON, the current flows through three switches: S1, S2 and CR1, which is a drawback of this converter. With respect to the conduction losses during the ON time interval, I see no improvement relative to the known circuit of a “bridgeless PFC”, in which ON-state current flows through only two switches, S1 and S2. For the same reason I would say, it is not more "true" bridgeless than the original circuit. I understand, the reduction of conduction losses in Cuk's circuit comes during OFF state of the switch when the current flows through a single switch CR2 while in the known circuit it flows though two switches, such as CR1 and S2. Therefore the main advantage of this circuit would probably be realized when ON time is low and OFF time is high. Since at low input line the duty cycle and ON-time tend to be high, while at high line they tend to be low, the advantage of the Cuk’s proposed converter would be at high input lines where PFC has higher efficiency anyway. The article claims 98% efficiency, but unfortunately it does not state under what input and output conditions it was achieved. I tend to doubt very much it is achieved at low line.

For more information see my review of schematics of various bridgeless PFC.