Welcome to the training module on VIPerPlus AC-DC Conversion, where we will study the Technology behind the products and their basic operations.
Today, new energy-saving regulations, either voluntary or mandatory, require further improvements in power-supply efficiency. The VIPerPlus family takes on this challenge. ST’s VIPerPlus series of high-voltage converters combine the innovative avalanche-rugged SuperMESH power MOSFET with state-of-the-art PWM circuitry. The VIPerPlus with more functionality supports the most popular SMPS topologies. It also provides improved protection against overload or overheating. The result is truly innovative AC-DC conversion that is efficient, simpler, quicker and with half the component count thus less expensive.
The VIPerPlus family represents the easiest solution that to complies with the Blue Angel and Energy Star eco norms, with extremely low total power consumption from the mains when the system is in standby mode. All VIPerPlus devices include the controller, the start-up circuitry and an 800V avalanche-rugged power MOSFET in the package. New integrated functions and high break-down voltage help to improve the robustness and the reliability of the power supplies, reduce the external component count, and provide both higher efficiency in operating mode and an ultra-low standby power consumption that is less than 50mW at 265V and can be reduced to 30mW with optimized transformer design.
The ViperPlus family can be used as auxiliary power supply in home appliances from coffee makers to washing machines and dishwashers, consumer equipment such as LCD TVs, DVD players and set-top boxes, domestic and architectural lighting, auxiliary supplies for desktop PCs and servers, and chargers for mobile phones, digital cameras, portable audio players, toys and cordless appliances such as shavers.
Here is block diagram of the VIPerPlus devices. The 800V avalanche-rugged power MOSFET is specifically optimized for the VIPerPlus. The fixed-frequency PWM controller with jittering, and the quasi-resonant innovative topology, maximize the efficiency in operating mode while reducing the EMI filter costs. Best-in-class in standby power allows customers to meet the most demanding energy-saving regulations such as Energy Star; 80+ Bronze, Silver and Gold. Protection features include accurate, adjustable over-voltage and overload protection, hysteretic over-temperature protection, two levels of over-current protection and open loop failure disconnection. By integrating a high-voltage startup-current generator as well as essential drain-current control during the converter start-up phase, VIPerPlus eliminates the need for a start-up resistor, reduces stress on the secondary diode and helps to prevent transformer saturation. The embedded SenseFET eliminates external sensing components, allowing a precise drain-current limit. Detection of a fault initiates the devices’ auto-restart function, which prevents damage to the power supply or the load.
This table shows you difference between VIPer and ViperPlus family of device. Viper is a single chip with VIPower technology and it has limited complexity in it’s control section. It’s its B-Vdss is 700V whiles that of VIPerPlus extends to 900V with a standby power-down of 30mW, fully compliant with energy saving regulation. It has a fixed frequency with jittering and quasi-resonant circuit.
The VIPerPlus device uses system in pack technology which include 2 pieces of silicon; the control section and power section. Its control system uses a process as fine as 0.35mm typical of ST’s BCD process. It has dedicated supermesh for the power section which has 800 or 900 V avalanche, has high voltage startup with under voltage lockout thresholds.
Here shows some of the features that is added to its normal family of device (VIPer). It has lower power consumption of lower than 50mW at 265Vac. This family devices can be used as current-mode converters with adjustable drain current limiting set point, and it generates frequency of 60kHz or 115kHz which reduces Electro magnetic interference, it implements Quasi-resonance frequency above 200kHz which reduces the size of transformer without sacrificing efficiency
VIPerPlus family implements many safety and improvement features like Automatic auto-restart after a fault condition, advanced overvoltage and overload protection, non-dissipative short circuit management, thermal shut down with temperature sensor is located in power section where the signal is managed in the control section.
The devices available on today’s market are ViPer15, 16, 17, 25, 27 and 28 series. The Y –axis, shows the power output range and x-axis shows converter topology. The topologies include Quasi resonant with isolated flyback topology, Fixed frequency with jittering along with isolated and non isolated topology.
These are the different topologies that are used by the viperplus family for switch mode power supply application. They include Buck converter used by Viper16 and Viper 26, Buck-Boost converter used by Viper16, and 26. Almost all the ViperPlus devices use Flyback isolated converter, flyback primary regulation converter, and flyback non-isolated converter.
This is a typical application circuit Quasi-Resonant Flyback with Mini-Features. The control core of the VIPER25 is a current-mode PWM controller with a zero current detection circuit designed for quasi-resonant operation, a technique that provides the benefits of minimum turn-on losses, low EMI emission and safe behaviour in case of short circuit.
This is the thermal shutdown graph for the ViperPlus family.
The Brown-out comparator is internally referenced to VBR which is typically 0.45 V. It disables the PWM if the voltage applied at the BR pin is below the internal reference. Under this condition, the power MOSFET is turned off. Until the brown-out condition is present, the VDD voltage, continuously oscillates between the VDD on and the undervoltage lock out thresholds, as shown in the timing diagram. The switching operation is restarted, as the voltage on the pin is above the reference plus the before said voltage hysteresis. The brown-out comparator is also provided with a current hysteresis, IBR hysteresis. With this approach it is possible to set the VIN on threshold and VIN off thresholds separately, by properly choosing the resistors of the divider connect to the BR pin.
This slide discusses the Auto-restart operation. The start-up sequence is not inhibited and will be activated only when the VDD voltage drops down to the VDD restart threshold which is typically 4.5 V. This means that the HV start-up current generator restarts the VDD capacitor, charging only when the VDD voltage drops below VDD restart. The scenario occurs for instance in a power-down because of a fault condition. After a fault condition, the charging current is typically 0.6 mA instead of the typical 3 mA current for a normal start-up converter phase.
This slide shows the overvoltage protection circuit that is implemented in the viperplus family of devices. If the voltage applied to the ZCD pin exceeds the internal voltage reference for four consecutive cycle in a row, the device interpreters this condition like a fault and stops operation. The function is digital filtered and strobed to reduce noise sensitivity and prevent the protection to be erroneously activated. In fact, in order to trip the protection, the ZCD has to sense the overvoltage for four consecutive switching cycles. This special feature uses an internal counter that is reset every time the over voltage protection signal is not triggered. The internal Over voltage protection block senses the ZCD pin voltage for a time interval whose width is of 500ns and starts 2 μs after MOSFET turn off.
Thank you for taking the time to view this presentation on ViperPlus AC-DC Conversion . If you would like to learn more or go on to purchase some of these devices, you may either click on the part list link, or simple call our sales hotline. For more technical information you may either visit the STMicroelectronics site, or if you would prefer to speak to someone live, please call our hotline number, or even use our ‘live chat’ online facility.
Introduction <ul><li>Purpose </li></ul><ul><ul><li>An Overview Study On AC-DC conversion: ViperPlus </li></ul></ul><ul><li>Outline </li></ul><ul><ul><li>Features and application </li></ul></ul><ul><ul><li>Block Diagram </li></ul></ul><ul><ul><li>Difference between Viper and ViperPlus </li></ul></ul><ul><ul><li>Technology of ViperPlus and its function, Product Family </li></ul></ul><ul><ul><li>Typical application circuit, Different Topologies, </li></ul></ul><ul><ul><li>Brownout, Auto-restart operation and Overvoltage protection. </li></ul></ul><ul><li>Content </li></ul><ul><ul><li>17 pages </li></ul></ul>
What is VIPerPlus? <ul><li>High-voltage converter ICs from AC mains to low-voltage DC </li></ul><ul><li>Capable of accepting 115 or 230 volts, as well as unregulated mains </li></ul><ul><li>Smart-power device including control logic and efficient SuperMESH ™ power MOSFET in the same package </li></ul><ul><li>Efficient conversion </li></ul><ul><li>Supports the most popular SMPS topologies </li></ul>
Key Features ■ 800 V avalanche rugged power section. ■ Quasi-resonant (QR) control for valley switching operation. ■ Standby power < 50 mW at 265 Vac. ■ Limiting current with adjustable set point. ■ Adjustable and accurate overvoltage protection. ■ On-board soft-start. ■ Safe auto-restart after a fault condition. ■ Hysteretic thermal shutdown.
Applications <ul><li>Adapters for PDA, camcorders, shavers, cellular phones, cordless phones, videogames. </li></ul><ul><li>Auxiliary power supply for LCD/PDP TV, monitors, audio systems, computer, industrial systems, LED driver, No el-cap LED driver, utility power meter. </li></ul><ul><li>SMPS for set-top boxes, DVD players and recorders, white goods. </li></ul>
Auto-restart operation <ul><li>HV start-up current generator restarts the VDD capacitor charging only when the VDD voltage drops below VDDrestart </li></ul><ul><li>After a fault condition, the charging current is 0.6 mA (typ.) instead of the 3 mA (typ.) of a normal start-up converter phase. </li></ul>
Overvoltage protection (OVP) <ul><li>If the voltage applied to the ZCD pin exceeds the internal voltage reference VOVP, for four consecutive cycle in a row, the device interpreters this condition like a fault and stops operation. </li></ul><ul><li>The auxiliary winding, during transformer demagnetization, tracks converter's output voltage through turn ratio. </li></ul><ul><li>Proper selecting the resistor divider that connect ZCD pin to the auxiliary winding RLIM and ROVP it is possible to set the Overvoltage Protection limit. </li></ul>
Additional Resource <ul><li>For ordering the VIPerPlus, please click the part list or </li></ul><ul><li>Call our sales hotline </li></ul><ul><li>For more product information go to </li></ul><ul><li>www.st.com/viper </li></ul><ul><li>For additional inquires contact our technical service hotline or even use our “Live Technical Chat” online facility </li></ul>