How to calculate a resonant switching power supply. Resonant power supply. Andreev's resonant choke on an W-shaped core from a transformer. How to turn a choke into an electricity generator

This high voltage source was made a long time ago, but I found it on the shelf and decided to describe it. This is practically an ordinary half-bridge (in their network huge pile) on IR2153 with the exception of a few points.

Firstly, the line transformer here operates at a resonant frequency, which means it produces a very high voltage. To prevent the liner from breaking through, it must not be turned on without a load! I think we need to make a protective arrester.

Secondly, “heavy” transistors (stw29nk50, there were such ones) that are quite unusual for such circuits are used at a fairly high frequency - about 120 kHz. In order to enable the IR2153 to control them, buffers are introduced. And in general, IR2153 is unloaded as much as possible. Voltage stabilization is external, buffers are also external. Mikruha's life has turned into a fairy tale)

Thirdly, the IR2153 powers itself after startup. The heating of resistor R4 is greatly reduced, and it can output more current to the gates. Another advantage of this approach is that if the source outputs are short-circuited for a long time, the power supply to ir2153 drops below the UVLO response threshold, it turns off, and is periodically turned on by the network resistor. Thus, the probability of removal from the short circuit is approximately zero.

Scheme (clickable)

The number of turns in the primary is 45, in the IR power supply winding – 4.

The transistors are placed on top of the radiator.

Assembled circuit

The liner himself didn’t want to fit into the body, so I had to file the body a little, and to make it look nice, I made a red cap with a big exclamation mark; I didn’t have enough talent to draw a lightning bolt))

Power consumption – 120W, short circuit. It can withstand loads without problems.

Video

My brother seems to have gotten used to the fact that I take away his camera in order to take pictures of my crafts. Therefore, here it is:

Why is the arc so dead? When it appears, the half-bridge goes out of resonance, and, because of this, the output power decreases. Power can always be increased by lowering the operating frequency and reducing the number of turns. Fortunately, transistors allow you to do this.

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The mains power supply is one of the most critical components in the structure of electronic equipment. The most important parameters of a network converter are: operating range of input voltage, power consumption in standby mode, overall dimensions, reliability, electromagnetic compatibility and cost. The vast majority of modern mains-powered equipment uses switching power supplies.

Introduction

The problems of energy saving and energy efficiency are among the most pressing in the global energy sector. One of the most important ways to increase the efficiency of a device is to increase the efficiency of switching power supply converters. Increasing efficiency and power density are the dominant factors in the design of AC/DC converters.

A feature of computer power supplies, as well as other power supplies of consumer electronic equipment, is that consumption varies within a wide range depending on the operating mode and activity of different system modules. A personal computer implements a power management mode by lowering the clock frequency, turning off power to the display, hard drive, or putting the PC into standby or sleep mode. The consumption range is from several watts (standby mode) to several hundred watts. In LCD TVs with dynamic LED backlighting or plasma panels, the current consumption is determined by the brightness of the current image on the screen. Ensuring high conversion efficiency for all modes is not an easy task.

Energy efficient electronics

Over the past ten years, a number of government organizations and initiative associations have developed criteria for assessing the efficiency of power supplies for electronic equipment. The main goal of the requirements is to control and significantly reduce the level of consumption of modern consumer electronic equipment. Equipment manufacturers must certify their products in accordance with these requirements.

Energy Star Program

Energy Star is a joint program of the US Environmental Protection Agency (EPA) and the Department of Energy. The goal of the program is to ensure the efficient use of generated electrical energy and reduce the harmful impact on the environment. One of the areas of the Energy Star program is the development of basic requirements for certification of consumption of consumer electronic equipment, in particular, computers, monitors, fax machines, copiers, televisions, audio systems, air conditioning systems, refrigerators and other household appliances. The development of new threshold requirements for the consumption of consumer electronic devices has forced manufacturers to use new energy-saving solutions, which has led to the emergence of a new class of electronic devices with reduced power consumption. For example, already in 2002, thanks to the active implementation of Energy Star standards, more than 100 billion kWh of electricity was saved in the United States alone.

Energy Star documents regulating energy efficiency requirements for electronic equipment:

• Energy Star v5.0 Desktop Computers and Workstations (with 80 PLUS certified power supplies);
• Energy Star v1.0 Datacenter Servers (with 80 PLUS certified power supplies);
• Energy Star v5.0 LCD Monitors.

80 PLUS - new standards for power supply efficiency

Previously, the efficiency of most system unit power supplies was about 80%. Thanks to the work of the 80 PLUS Committee initiative group, a new unified system of efficiency standards for power supply manufacturers was adopted. These companies were forced to improve their performance indicators in order to obtain certification to enter the markets of leading countries.

The documents define the desired levels of conversion efficiency for three different converter load conditions (20, 50 and 100%) (table). In accordance with these levels, four classes of appliance efficiency are defined: bronze, silver, gold and platinum:

• 80 PLUS E-Star 4.0 - 80% efficiency at all power supply load levels.
• 80 PLUS Bronze - 82% efficiency at light (20%) and heavy (100%) power supply load and 85% efficiency at medium (50%) power supply load.
• 80 PLUS Silver - 85% efficiency at light and heavy load on the power supply and 88% efficiency at average load on the power supply.
• 80 PLUS Gold - 87% efficiency at light and heavy load on the power supply and 90% efficiency at average load on the power supply.

Table. 80 PLUS performance certification levels

In 2006, Energy Star included 80 PLUS requirements in its Energy Star 4.0 computer specifications. Already in November 2006 and February 2007, HP and Dell certified their computer power supplies to meet 80 PLUS requirements.

Switching Power Supply Architecture

A typical network computer ATX switching mode power supply (SMPS) should provide an output voltage of 12 V and a current of 20 A.

The main area of ​​application is the power supply for computer equipment (PC system unit), other computer devices, telecommunications equipment, LCD TVs, plasma panels, LED lamps and chargers. The main goal is efficient conversion, reduction in size, EMI level, as well as power loss and heat generation.

Initial data

The universal input voltage range is from 90 to 265 V AC at a frequency of 47-63 Hz. This means that the source will be able to operate in any country with any mains voltage rating, as well as with deviations from the nominal voltage and frequency. Output voltage and current - 12 V/20 A. Mains consumption - 50 mA in off mode; 100 mA in sleep mode; 5 A in active mode.

The proposed architecture shown in Fig. 1, has a three-stage structure:

1. Power factor corrector.
2. Controller of pulse voltage converter.
3. Synchronous rectifier of the secondary circuit source.

Rice. 1. Block diagram of a 240 W switching power supply

The chosen architecture is based on the use of three efficient energy conversion stages. The first stage is a universal input active power factor corrector with an output voltage of 385 V on the NCP1397B controller. The second stage is a half-bridge resonant LLC converter. The +12 V secondary circuit of this source uses a synchronous rectification circuit built on the NCP4303 ON Semiconductor controller chip.

The architecture chosen for this project optimizes system resources to ensure maximum power conversion efficiency and meet the original power supply requirements. The architecture also allows to reduce the price, reduce the complexity of the device and increase its reliability.

First stage. Power factor corrector

The use of power factor correction (PFC) technology is one of the key aspects in the development of efficient and powerful network power supplies. The overwhelming number of household and industrial consumers of electricity currently use pulsed network converters and AC/DC converters. The typical structure of a network converter contains a diode bridge, a capacitive filter, and output stabilized voltage converters. If necessary, AC/DC converters can also contain galvanic isolation from the network.

The conversion efficiency is determined by the efficiency of the basic units - a rectifier with a filter and DC/DC converters. The “diode bridge - capacitor” link is weak in terms of energy transmission efficiency. The capacitance is charged and, therefore, energy consumption from the network occurs only in short phases during the “peaks” of the sinusoids of the network voltage. And the transfer of energy from the storage tank to the load may occur unevenly over time.

To provide the required current load, the capacitance of the capacitor must be quite large. As the converter power increases, the problem becomes critical. When charging a large storage capacity, current surges occur in the network in a short period of time. And at the initial moment the source is connected to the network, current surges can reach hundreds of amperes. This leads to distortion of the mains voltage waveform. The inclusion of non-linear loads in the network, for example, lamps with gas-discharge lamps, controlled electric motors, power supplies with a capacitive filter, etc., leads to the fact that the current consumed by these devices is pulsed in nature with a high percentage of high harmonics, due to which Electromagnetic compatibility problems may arise when operating various equipment.

Power Factor Corrector and Standards

The main task of the PFC is to reduce to zero the lag of the consumed current from the network voltage while maintaining the sinusoidal shape of the current. To do this, it is necessary to take current from the network not at short intervals, but throughout the entire period of operation. The power taken from the source must remain constant even if the network voltage changes. This means that when the network voltage decreases, the load current must be increased, and vice versa. From the network side, the power supply will look like a purely active resistance. The power factor corrector is a voltage converter with an inductive storage and energy transfer in reverse. The PFC stage in the structure of a powerful AC/DC converter is an intermediate source of stabilized voltage, from which other voltage converters are powered.

Active power factor correction is widely used in all modern high-power power supplies. The use of a power factor correction stage can increase conversion efficiency and reduce the level of network interference. The need for a power factor corrector (PFC) in powerful network sources of secondary power supply is regulated by the electromagnetic compatibility requirements of GOST R 51317-2000. The standards for harmonic components of current consumption and power factor for power supply systems with a power of more than 50 W and all types of lighting equipment are determined by the IEC standard IEC 1000-3-2. For power supply devices for communication equipment, since March 2001, the Ministry of Communications of the Russian Federation introduced OST 45.188-20-01, which states that the power factor of power supply equipment must be at least 0.95 for devices with power correction.

Structure of the power corrector module

The power factor corrector module (Fig. 2) contains a PFC controller chip, an inductor, a powerful MOSFET switch, a rectifier diode, feedback sensor circuits and an output capacitance.

Rice. 2. Structure of power factor corrector

Regulation and stabilization of the output voltage is carried out by a PWM signal. The diagram does not show the power supply circuits, control modes and protection thresholds. The circuit is practically no different from the classic circuits of pulsed voltage converters. Just a few features are worth noting. To meet the requirements of electromagnetic compatibility standards, the conversion in the correctors is always carried out at a constant frequency. Typically above 200 W, most PFCs are designed as booster converters operating in continuous conduction mode (CCM) or Continuous Current Mode (CCM).

NCP1605 - power factor correction controller

NCP1605 is a power factor correction controller chip. It operates at a fixed conversion frequency and in the Critical Conduction Mode control mode. For 240 W output power, the most efficient Frequency Clamped Critical Conduction Mode (FCCrM) is selected because it provides not only high conversion efficiency, but also low EMI levels. The NCP1605 controller operates in this mode. The circuit also has built-in protection, both against current overload and for load-off mode.

Second stage. Half-bridge resonant LLC converter

The SMPS switching power supply stage uses a half-bridge LLC resonant topology, which significantly improves conversion efficiency and allows for reduced EMI levels and improved isolation transformer utilization compared to traditional topologies (Figure 3). LLC uses two inductances (LL) connected in series - inductor + primary winding of the transformer, and one capacitance (C).

Rice. 3. Structure of a half-bridge resonant LLC converter

The half-bridge resonant converter has an LLC topology and belongs to the subtype of series resonant converters (SRC). It is widely used in applications where high power density is required.

The half-bridge resonant LLC converter circuit is an excellent alternative to the traditional Half Bridge (HB) topology for several reasons:

• Switching occurs when the voltage crosses zero (Zero Voltage Switching, ZVS) over a wide range of loads. Since switching occurs at low switch drain voltage, switching losses are minimized. This also allows for a significant reduction in EMI levels compared to the HB (half bridge) topology, which requires switching under more severe conditions.
• Low current during switching. The switch closes at low throughput current, resulting in low energy loss compared to that of an HB topology.
• Low turn-off current on the secondary circuit diodes: when the converter operates in high output current mode, the output rectifier goes into the off state under the condition of low current flow, which reduces the EMI level.
• The circuit topology does not increase the number of components. The total number of components remains the same as in the classic half-bridge topology.

In Fig. Figure 4 shows a block diagram of a half-bridge resonant converter. Half-bridge switches operate with a duty cycle of 50% and provide the formation of high-voltage rectangular pulses with an amplitude from 0 to the input voltage V IN, which enters the resonant circuit. By adjusting the frequency via a voltage controlled oscillator (VCO), tracking feedback is provided. The frequency varies depending on the load size.

Rice. 4. Block diagram of a half-bridge resonant voltage converter

NCP1397 - LLC converter controller

The heart of the half-bridge resonant LLC converter is the NCP1397 controller chip. Featuring proprietary high-voltage technology, this controller contains a MOSFET driver for a half-bridge output circuit. The supply voltage of the half-bridge circuit is up to 600 V.

The controller has multi-level built-in protection, including blocking the output in the event of a loss of input voltage, loss of a feedback signal from an optocoupler, etc. This allows you to improve the reliability of the stage without complicating the design and additional components.

Secondary circuit of the power supply. Synchronous rectifier

Why is synchronous rectification needed? The use of a synchronous rectification circuit makes it possible to reduce rectification losses at high current and load values. When using a conventional diode circuit, even with Schottky diodes, at high currents the voltage drop increases significantly and, accordingly, losses increase.

In Fig. Figure 5 shows the advantages of using synchronous rectifier at high output current compared to a conventional diode rectifier circuit.

Rice. 5. Comparison of losses on a synchronous rectifier and a conventional diode rectifier (losses on Schottky diodes will be greater at higher currents than on the open channel of a MOSFET transistor)

However, it can be noted that the synchronous rectification mode becomes ineffective in the zone of low currents in the load. To maintain efficiency over a wide load range, the synchronous rectifier module automatically turns off at low currents. In Fig. Figure 6 shows the control circuit for NCP4303 synchronous rectifiers with a shutdown circuit for low load currents.

I usually adhere to the principle that the fewer parts in a circuit, the simpler it is, the more reliable it is. But this case is an exception. Those who have designed and assembled circuits for powerful step-up voltage converters from 12/24 volts to 300 (for example), know that classical approaches do not work well here. The currents in low voltage circuits are too high. The use of PWM circuits leads to switching losses, which instantly overheat and damage the power transistors. The internal resistance of power switches is a serious obstacle to the use of circuits with design limitation of switching losses, such as bridge and half-bridge circuits.

The above circuit is based on separating the function of increasing the voltage and stabilizing it in different stages. With this approach, we get the opportunity to force the most problematic unit - the inverter - to work in resonant mode with minimal losses on the power switches and the rectifier bridge in the high-voltage part of the circuit. And the output voltage is stabilized in the block ST, which is assembled using a simple boosting topology. Now its diagram is not given; there will be a separate article about it. A stable required voltage is removed from its output.

Schematic diagram of a resonant voltage converter

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