Reading the excellent article IBA-Based Power Solutions Demand Systems-Level Protection written by Bob Thomas of Cisco made me think that there are, as they say, many ways to skin a cat. While Bob describes the difficulties of working with the widely available standard niPOLs, that do not have the desired and require external components to add such features, there are devices on the market that not only achieve in a single device what is required, but add many additional features as well. Addressing each one of Bob’s concerns:

Over-Voltage & Over-Temperature Protection: The Z-One series of products provides the two functions as standard feature on all the products.

System Overview: Bus Power Protection Besides the sequencing, on/off, v-OK signals The Z-One series POLs have a very sophisticated bus protection feature that not only can be adjusted for the desired over-voltage but protects the output from catastrophic over-voltage conditions.

The YM7000 Series Z-POL Digital Power converters use a standard synchronous conversion topology supplemented by a digital PWM feedback loop, a digital controller and sensing circuitry and an integrated driver that drives the switching of the Q1 upper and Q2 lower FETs. The controller constantly monitors the Z-POL voltage and current adjusting the output within the regulation parameters. If a failure of the upper Q1 FET occurs, the controller sends a signal to the FET driver, directing it to fully turn on the Q2, lower FET. This causes the voltage in front of the inductive filter to go to zero thus preventing over-voltage on the Z-POL output. At the same time a shutdown signal is sent over the Z-One Digital Bus through the Digital Power Manager (DPM) to the isolated DC-DC Converter which turns its’ output from the intermediate voltage down to zero. Additionally, if an optional Silicon Rectifier SCR crowbar is used, an additional signal from the DPM can trigger the SCR crowbar that will pull the IBA down to zero volts. Such triple protection mechanism, incorporated as a standard Z-POL function assures that a high IBA voltage does not damage the expensive semiconductor system circuitry. Over Temperature Protection: Over Temperature Protection is a standard feature on all Z-One niPOLs and a signal can be sent to the main system when each niPOL exceeds the set over temperature. Since each POL has it’s own internal temperature monitor, there is no need for discrete external thermistors. During development, the system can be exercised, monitored and adjusted as needed. Additionally, output voltage and current as well as POL temperature are constantly monitored with values stored in a shift register. In case of system failures the shift register, just like an aircraft “Black Box”, can be accessed for the store temperature, voltage and current values of each niPOL. Besides the sequencing, on/off, v-OK signals The Z-One series POLs have a very sophisticated output over voltage protection feature.

The concerns that this article raises are real and very important to address, when handling circuit board power and these issues were carefully considered during the Z-One system development. The main differences between the discrete and the Z-One solutions, as shown in the table, are the reduction of number of: components, circuit board traces, PCB space, development time and total system cost. For detailed specifications and application notes on the extensive Z-One products check out the Power-One website: http://www.power-one.com

PS. I was unable to attach the block diagram for the Z-POL. Please contact me by e-mail and I can forward it if necessary