PWM Failure Analysis

Gideon Analytical Laboratories received a Printed Circuit Board (PCB) with contamination on several capacitor sleeves, connector pins, and an oscillator. An electrolytic capacitor is a capacitor whose anode (+) consists of pure aluminum foil with an etched surface, covered with a uniformly very thin barrier layer of insulating aluminum oxide, which operates as a dielectric. The electrolyte, which covers the rough surface of the oxide layer, operates as the second electrode, the cathode (-). E-caps have the largest capacitance values per unit volume compared to the two other main conventional capacitor families, ceramic and plastic film capacitors, but much smaller capacitance than similarly sized supercapacitors. Aluminum electrolytic capacitors are divided into three subfamilies by the type of electrolyte. There are non-solid (liquid, wet) aluminum electrolytic capacitors, solid manganese dioxide aluminum electrolytic capacitors, and solid polymer aluminum electrolytic capacitors. Basic parts to an electrolytic capacitor include anode foil, a dielectric, cathode foil, cathode oxide layer, non-solid electrolyte, paper spacer, conducting polymer, among other materials. An electronic oscillator is an electronic circuit that produces a periodic, oscillating electronic signal, often a sine wave or a square wave. Oscillators convert direct current (DC) from a power supply to an alternating current (AC) signal. They are widely used in many electronic devices. The goal was to identify the contamination on the capacitor sleeves, connector pins, and an oscillator.

Gideon Analytical Laboratories received two valves with failed printed circuit boards (PCBs) and corrosion inside the housing. The goal was to determine what the corrosion was and why the PCB failed. A printed circuit board mechanically supports and electrically connects electronic components using conductive trace lines, pads and other features etched from copper sheets laminated onto a non-conductive substrate. The boards are made from glass reinforced plastic with copper tracks in the place of wires. Components are fixed in position by drilling holes through the board, locating the components and then soldering them in place. The copper tracks link the components together forming a circuit. PCBs are used in all but the simplest electronic products. They are a quintessential part of the electronics industry. With decades of experience working with PCBs and advanced knowledge in electrical engineering and chemistry, this proved to be a case that was easy to solve.

Gideon Analytical Laboratories received 8Murata Ps DC-DC converters (pn 8600118) with suspected MOSFET failures. A DC-DC converter is an electronic circuit or electromechanical device that converts a source of direct current (DC) from one voltage level to another. It is a type of electric power converter. Power levels range from very low (small batteries) to very high (high-voltage power transmission). The DC to DC converters MOSFET is a type of field-effect transistor (FET). It has an insulated gate, whose voltage determines the conductivity of the device. This ability to change conductivity with the amount of applied voltage can be used for amplifying or switching electronic signals. Gideon Analytical Laboratories received 8 totalMurata Ps DC-DC converters (pn 8600118) in two separate batches. The first batch had a different mode of failure than the second batch. The goal was to determine the cause of the failures by focusing specifically on the MOSFETs.

GideonAnalytical Laboratories received several Printed Circuit Boards (PCBs) that were experiencing delamination of the solder masks, specifically on the EMI filter card. A PCB mechanically supports and electrically connects electronic components using conductive tracks, pads and other features etched from copper sheets laminated onto a non-conductive substrate. Components (e.g. capacitors, resistors or active devices) are generally soldered on the PCB. Advanced PCBs may contain components embedded in the substrate. Electromagnetic interference (EMI), also called radio-frequency interference (RFI) when in the radio frequency spectrum, is a disturbance generated by an external source that affects an electrical circuit by electromagnetic induction, electrostatic coupling, or conduction.The disturbance may degrade the performance of the circuit or even stop it from functioning. In the case of a data path, these effects can range from an increase in error rate to a total loss of the data.

The RS2042 is a low startup current, current mode PWM controller with Green-Power & burst-mode power-saving operation. It has integrated functions such as the leading-edge blanking of the current sensing, internal slope compensation, low external component counts, and easily fits in with AC/DC power applications. The Green-Power function provides off-time modulation to linearly decrease the switching frequency under light-load conditions. And under zero-load conditions, the power supply enters burst-mode to further reduce power consumption by shutting off PWM output. When the output of the power supply is short or overloaded, the FB voltage will increase, and if the FB voltage is higher than 5.2V for longer than 56msec, the PWM output will be turned off. Pulse by pulse current limit ensures a constant output current even under short circuit. PWM output will be disabled as long as VDD exceeds a threshold. When an internal latch circuit is used to latch-off the controller, the latch will be reset when the power supply VDD is disabled.

Gideon Analytical Laboratories received pulse width modulators PWM failing in a MuRata Ps DC-DC converter. The PWM was removed from the encapsulation and tested. Several I/O pins were either open or showed no connection to the circuitry of the IC. The PWM CS51022AG is a fixed frequency current mode controller family provides the necessary features for DC−DC primary side control. In addition to low startup current (75A) and high frequency operation capability, the CS51022A includes over-voltage and under-voltage monitoring, externally programmable dual threshold over-current protection, current sense leading edge blanking, current slope compensation, accurate duty cycle control and an externally available 5.0 V reference. The CS51022A has a sleep mode with 100 A maximum IC current consumption. The CS51022A is in a 16 lead narrow body SOIC package.