ECRI Microelectronics


What is the Low Line ?

The lowest steady-state input voltage that can maintain the output voltage of the converter undetermined.

What is the Soft Line ?

Soft Line: AC power supply with large impedance. As the load increases, the input voltage to the power supply will drop significantly.

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What is Pulse Width Modulation-PWM?
Pulse width modulation is a modulation control method commonly used in switching power supplies. Its characteristic is keeping the switching frequency constant, namely not changing the switching cycle but change the pulse width, which makes the change of the output voltage of the switching power supply least when the voltage and load of the electrical network change.
What is Duty Cycle Ratio?
The duty cycle ratio refers to the proportion of transistor conduction time toN in a period T. The  duty cycle ratio D=toN/T.
What is Hard Switching?
When the voltage or current on the transistor has not yet been zero, the switch tube is forced to turn on or off. At this time, the switch tube voltage drops or rises and the current rises or falls with an overlapping process. Therefore, the tube has a loss during the switching. This way of switching is Hard Switching.
What is Soft Switching?
The transistor switch is turned on when its voltage is zero, or it is turned off when the current is zero, so that the tube loss is close to zero during the switching process. This switching mode is called soft switching.
What is Resonance?
Resonance is a physical phenomenon in AC circuits. In the ideal (no parasitic resistance) inductance and capacitance series circuit input, plus a sinusoidal voltage source, when the frequency of the power supply is a certain frequency, the capacitive reactance is equal to the inductive reactance, the circuit impedance is zero, and the current can reach infinity. The phenomenon is called series resonance. Similarly, when an ideal LC parallel circuit adds a sinusoidal current source, the total admittance of the circuit is zero, and the voltage on the element is infinite, which is called parallel resonance.
What is center tap?
The center tap refers to the electrical connector that is tapped at the midpoint of the transformer's inductor.
What is Quasi-Resonance?
For a LC series circuit with a switch, when the current oscillates at the resonant frequency, if the switch acts, the current sinusoidal oscillation occurs only in part time of one cycle, and the current assumes a quasi-sinusoidal, a phenomenon known as quasi-resonance. Similarly, in an LC parallel circuit, quasi-resonance can also be obtained by means of a switching action.
What is zero voltage switching?
Using the resonance phenomenon, when the device voltage oscillates to zero according to a sine law in the switching converter, the device is turned on, which is called zero voltage switching.
What is zero-current switching?
When the device current of the switching converter oscillates to zero according to a sine law, the device is turned off, which is called zero-current switching.
What is PWM switching converter?
The PWM switching converter refers to a switching converter that controls the switching of the transistors through pulse width modulation. It belongs to the constant-frequency controlled hard switch type.
What is off-line switching converter?
The off-line switching converter is an AC/DC converter whose input rectifier and flat-wave capacitor are directly connected to the AC network.
What is resonant converter?
Using the resonance phenomenon, the voltage or current on the device in the switching converter is changed in a sinusoidal manner, thereby creating a condition of ZVS or ZCS, called a resonant converter. Split two series and parallel resonant converters. Connect the LC network in series at the output end of the bridge converter bridge, and then connect the transformer and rectifier to obtain a series resonant DC/DC converter; connect the load (including transformer and rectifier) in parallel across the capacitor of the series LC network of the bridge converter. , available DC/DC parallel resonant converter.
What is quasi-resonant converter?
Using the quasi-resonant phenomenon, the voltage or current on the device in the switching converter is changed by a quasi-sinusoidal law, thus creating a condition of ZVS or ZCS, which is called a quasi-resonant converter. In a single-ended, half-bridge or full-bridge converter, a quasi-resonant converter can be obtained using parasitic inductance and capacitance or externally coupled resonant inductance and capacitance. The resonance parameters can be more than two, for example three or more, which is also referred to as a multi-resonant converter. In order to keep the output voltage almost constant, both the resonant and quasi-resonant converters must use variable frequency control.
What is the use of a transformer in a DC DC converter circuit?
There are three main roles:
1) Power transfer: The transformer transfers the input side energy to the output side.
2) Voltage conversion: By setting the transformer turns ratio, the given input voltage is converted into the required output voltage.
3) Insulation isolation: Insulation isolation between the input side circuit and the output side circuit.
Why are MOSFETs mostly preferred than IGBTs in DC DC converters?
The design of DC DC converter generally requires small size and high operating frequency. Compared with IGBTs, MOSFETs have the characteristics of small size and high switching frequency (up to several hundred KHZ ~ several MHZ), so they are preferred in DC DC design. Use MOSFETs as power switches. At the same time, MOSFETs are mainly used in several watts to hundreds of watts, and IGBTs are mainly used in several hundred watts to several kW.
What is Zero-Switching Converter?
In the quasi-resonant converter, an auxiliary switch is added to control the operation of the resonant network to make the converter work for a part of the time according to the ZCS or ZVS quasi-resonant converter, and the other part of the time is operated by the PWM converter, called ZCS- PWM or ZVS-PWM converter. It combines the features of ZCS (or ZVS) soft switching and PWM constant frequency control. The inductance in the resonant network is then in series with the main switch.
What is Zero-Transition Converter?
If the resonant network is connected in parallel with the main switch and still controlled by the auxiliary switch, the same characteristics as the ZCS-PWM or ZVS-PWM converter can be obtained, which are respectively called ZCS-PWM or ZVS-PWM converter. It is essentially still a ZCS or ZVS soft-switch-PWM converter.
What is Phase-Shift FB ZVS-PWM Converter?
In a full-bridge switching converter, a resonant and phase-shifted full-bridge ZVS-Pwm converter utilizing a switching junction capacitance and a transformer leakage inductance (plus a resonant element if necessary) is utilized. It is also a soft-switching-PWM converter for high power, low voltage output.
What is continueous conducting mode?
Continuous conduction mode means that the inductor current (or the capacitance voltage of the transmitted energy) is always greater than zero during the period.
What is single-ended converter?
The most simple circuit type DC DC converter with isolation transformer is characterized in that the core of the high-frequency transformer is excited by the unidirectional pulsating current, and the magnetic flux in the core changes only on the hysteresis loop in one cycle, so the magnetic properties of the core Can you make full use of it? According to the excitation direction in a week, there are forward and flyback converters. There are also Cuk converters with isolation. There can be multiple outputs.
What is Forward Converter?
The single-tube forward converter is a simple-ended single-ended converter, which is essentially a Buck converter with an isolation transformer. The secondary side output terminal is connected with a freewheeling diode in addition to a diode in series. The characteristic is that when the switch tube is turned on, the energy is transmitted from the primary side to the secondary side; when the switch tube is turned off, the secondary side relies on the inductor to continue to flow. However, in both cases, the core is subjected to the same excitation direction. Therefore, a "reset" action must be taken to return the flux to the original position at the beginning of the cycle at the end of the cycle. The single-tube forward converter is suitable for low power, and the voltage of the switch tube is calculated according to 2Vi. Vi is the input voltage.
What is Two-transistor forward converter?
In the forward converter, two switching tubes are connected in series with the primary winding of the transformer, and are turned on or off at the same time. The primary side of the transformer is connected like a bridge, and the opposite sides of the bridge arm are two switching tubes and two diodes. The output of the bridge is connected to the primary side of the transformer, and the secondary side circuit is the same as the single-tube forward. Its operating mode is completely different from that of a bridge converter. Since the demagnetization current passes through the diode and the primary winding during Toff, there is no need to separately provide a demagnetization winding. The two-switch forward converter can be used for medium power, and each tube is subjected to a voltage of approximately Vi. Two sets of identical double-switch forward converters are connected in parallel, and the input is connected in series or in parallel. After being connected to the AC/DC rectifier, it can be used for high-power output and input terminal to the rectified output of AC400V or 220 grid.
What is Flyback Converter?
The flyback converter is one of the simplest single-ended converters. Unlike the forward circuit, the secondary side of the transformer is connected to the reverse diode. In the Toff, the magnetic current flows in the secondary winding of the transformer, and there is no need to separately provide a demagnetizing winding. The flyback converter is essentially an isolated Buck-Boost converter, and its transformer acts as a transmitting energy element. Therefore, the transformer core should have a large air gap, making the magnetic performance utilization less. It is suitable for low power. The switch tube is subjected to the same voltage as the single-switch forward circuit.
What is Push-Pull Converter?
The two symmetric forward circuits are connected in a push-pull form to form a square wave inverter. The power transformer is connected to the push-pull rectifier and the LC filter circuit to form a Buck-type push-pull converter, but the output does not require an additional freewheeling diode. The main advantage is that the design is simple, the transformer core is fully utilized, and no additional magnetic winding is required. Each tube withstands voltage greater than 2Vi. The disadvantage is that the two tubes may be electrically conductive at the same time. Can be used for medium power and when multiple outputs are required. When the inductor is connected to the input, it is called a Boost push-pull converter.
Why can't we use a DC DC converter as a DC transformer in HVDC transmission?
At present, the DC/DC converters that can be supplied can be used in the high-voltage DC bus system. The output power of the thick film hybrid integrated process product is not more than 120W, and the output power of the PCB surface mount technology product is not more than 1000W. However, in high-voltage input applications, it is limited by the withstand voltage capability of the Si power device inside the DC/DC converter. Considering the device selection and internal insulation design requirements, the maximum input voltage of the DC/DC converter does not exceed 400V, including Thick film hybrid integration process and PCB surface mount process DC/DC converter.
Why do boost DC DC converters have low efficiency at low load currents?
Not only BOOST type DC/DC converters, other types of DC/DC converters, such as BUCK type DC/DC converters, BUCK-BOOST type DC/DC converters, flyback and forward DC/DC converters, etc. Efficiency is lower at low load currents. Generally, below the 1/5 low load condition, as the output power of the DC/DC converter decreases, the proportion of the internal loss of the DC/DC converter in the total power increases, causing the efficiency of the DC/DC converter to decrease.
Why does a DC DC converter have a bleeder resistor at its output?
At the output of the conventional DC/DC converter, there is an output voltage sampling resistor inside, and its main function is to sample and output the output voltage to the feedback circuit, which can function as a certain bleeder resistor; part of the DC/DC converter According to the user's needs, a pure resistive load will be added to the input to ensure the output of the DC/DC converter is stable. The pure resistive load can be used as a bleeder resistor.
What is Half-Bridge Converter?
The half-bridge converter consists of two power transistors and two capacitors, which are bridge-type square wave inverters. The two capacitors are connected in series with the input voltage, and the secondary side of the transformer is connected to the push-pull or bridge rectifier filter circuit, which is suitable for medium power.
What is full-bridge converter?
The full-bridge converter consists of four power transistors and is suitable for high power. The advantage of the half-bridge and full-bridge converters is that the voltage of each tube is subjected to Vi and the magnetic properties of the transformer can be fully utilized. The disadvantage is that symmetry is a concern, and it is dangerous when the transistors of both arms are turned on in one branch. The filter inductor can be connected to the power input or the rectified output, respectively called Boost or Buck bridge converter.
What is AC-OK signal?
This signal is used to indicate the turn-on and turn-off of the 220VAC power input voltage.
What is apparent power?
The power value is the product of the voltage rms value in the circuit and the current rms value, which does not take into account the power factor.
What is bandwidth?
The frequency band that must be considered when determining a parameter of the power supply is the bandwidth.
What is baseplate?
The aluminum substrate for power module installation is the substrate
What is bleeder resistor?
Leakage resistance refers to the insertion of a leakage resistor in the circuit to discharge a capacitor to generate a small leakage current.
What is bobbin?
The coil bobbin refers to a bracket of a wire transformer or an inductive coil, and the bobbin can also function as an insulation between the coil and the core.
What is breakdown voltage?
The breakdown voltage refers to the electrical insulation being destroyed by the voltage. In a power system, the breakdown voltage is the highest current or DC voltage applied to the input and output or between the input and output to the backplane.
What is burn-in?
Aging refers to the power product before leaving the factory. In order to eliminate the initial failure of the component and other potential effects, it should normally run for a period of time under the rated load. This process is called product aging....
What is common mode noise?
Common mode noise refers to the fact that two conductors have equal noise to a certain punctual point, usually referring to the noise of the AC power line and the neutral line to ground.
What is crest factor?
The crest factor refers to the ratio of the peak value of the waveform to the effective value (RMS) in an AC circuit. Under the condition that the transmission power is constant, as the peak value increases, the effective value (RMS) also increases. Therefore, the power consumption also increases. The crest factor is sometimes used to account for the stress of the current in the AC power line.
What is cross regulation?
Cross adjustment refers to the adjustment of the load change of one output to the output load of the other.
What is crowbar?
The lever circuit is a protection method that, after detecting an overvoltage or overcurrent fault, can quickly short the power supply output to ground in order to protect the load.
What is current mode?
The current type refers to a control method of the switching converter. When the current type control is used, the converter passes the double loop control circuit to adjust the pulse width according to the detected output current and the output voltage to stabilize the output voltage.
What is current monitor?
A current monitor is an analog current signal whose output signal is proportional to the output current.
What is DC-OK Signal?
The DC power good signal is a signal that monitors the DC output status.
What is Derating?
Derating refers to reducing operational requirements in order to improve the reliability of power supply operation. In a power system, when the ambient temperature is high, in order to make the power supply work safely, the use of output power is usually reduced.
What is defferential mode noise?
Differential mode noise is the noise of the power line to the common reference point measured between the two power lines after the common mode noise is removed. The test result is the difference between the noise components of the two power lines. Noise is typically tested at the DC output and DC return in power systems.
What is drift?
Drift refers to the change of output voltage with time after the warm-up process, when the parameters such as power supply voltage, load and operating temperature remain unchanged.
What is dropout?
The drop voltage is the lower limit of the AC input. After the input voltage is lower than this value, the output voltage cannot be stabilized. In a linear power supply, the drop voltage is primarily dependent on the power supply input voltage. In most switching power supplies, the drop voltage is primarily dependent on the load and has little to do with the input voltage.
What is dynamic load regulation?
The dynamic load regulation of the power supply is the change in the output voltage when the input current changes rapidly.
What is electronic load?
Electronic load refers to an electronic device used as a power output load that can be dynamically adjusted and controlled by a computer.
What is floating output?
The floating output is the voltage at one output of the power supply and is not based on any other output. Non-suspended output power, each group output has a common ground.
What is foldback current limiting?
This waveform has the same characteristics as a sine wave, but it is a sine wave portion superimposed on other waveforms, which is the input current waveform of a typical off-line power supply.
What is holdup capacitor?
The stored energy of the capacitor maintains the output voltage for a period of time after the input voltage is interrupted.
What is holdup time?
After the AC input power fails, the power supply can keep the output voltage constant.
Basic form of switching power supply

Modern switching power supplies are divided into two types: DC switching power supply and AC switching power supply. The former outputs high-quality direct current, and the latter outputs high-quality alternating current. The core of the switching power supply is the AC-DC converter. The converter is a device that uses power electronics to convert one type of electrical energy into another or multiple forms of electrical energy. According to the type of converted electrical energy, it can be divided into four types: 1. DC a DC converter, which is a converter that converts one DC power into another or a plurality of DC power, is a main component of a DC switching power supply; 2. An inverter is a power exchanger that converts DC power into AC power. It is the main component of the AC switching power supply and the uninterruptible power supply UPS; 3. The rectifier is the electric energy converter that converts the alternating current into the direct current; 4. The crossover is the direct conversion of one frequency of alternating current to another constant frequency. Or variable frequency AC, or a power converter that converts variable frequency AC directly into constant frequency AC. These four types of converters can be either single-row or bidirectional. The unidirectional power converter can only say that the electric energy is input from one direction and converted from the other direction; the bidirectional electric energy converter can realize the bidirectional flow of electric energy.

Classification of PWM DC Converters

1. According to whether there is electrical isolation between input and output: non-isolated DC converter with isolated DC converter.

2. Non-isolated DC converters are classified according to the number of active power switching devices: single tube, double tube and four tube.

There are six types of single-tube DC converters, namely, a buck converter, a boost converter, a buck-boost converter, a Cuk converter, a Zeta converter, and a Sepic transform. And so on. Among the six single-tube converters, buck and boost converters are the most basic, and the other four are derived from them.

The dual-tube DC converter has a double-tube series-connected Buck/Boost converter.

Four-tube DC converter such as Full-bridge converter

3. Isolated DC converters can be classified by the number of active power switching devices. There are two types of single tubes: Forward and Flydack.

The double tube has four types of double tube forward, double tube flyback, push pull and half bridge. Four-tube DC converter timely full-bridge DC converter.

The isolated converter can realize the electrical isolation between the input and the output. Usually, the transformer is used for isolation. The transformer itself has the function of voltage transformation, which is beneficial to expand the application range of the converter. The application of the transformer also facilitates the output of multiple voltages.

When the voltage and current rating of the power switch tube are the same, the output power of the converter is usually proportional to the number of switches used, so the output power of the four-tube converter is the largest, and the output power of the single-tube converter is the smallest.

No single converter can be combined with an isolated converter to obtain characteristics that are not available in a single converter.

4. According to the energy transfer, the DC converter has one-way and two-way. The charger with bidirectional function charges the battery when the power is normal. Once the power is interrupted, it can return the battery power to the grid and supply power to the grid for a short period of time. The DC motor control converter is also bidirectional. When the motor is working, the electric energy is transmitted from the power source to the motor, and the motor power is fed back to the power source during braking.

5. DC converters are also divided into self-excited and other controlled. The converter that realizes the self-sustaining periodic switching of the switch by means of the positive feedback signal of the converter itself is called a self-excited converter, and the Loyer converter is a typical push-pull self-excited converter. The switching device control signal in his controlled DC converter is generated by a special control circuit.

What is the Hot Swap ?

Plug or unplug the power supply in a powered system

What is the Inrush Current ?

The peak current flowing into the power supply device when the power is turned on. Since the input filter capacitor is quickly charged, this peak current is much larger than the steady state input current.

What is the Line Regulation ?

The rate of change of the output voltage when the AC input voltage is programmed from the lowest value.

What is the Off Line ?

The input power of the power supply unit is directly supplied by the AC power supply. Rectification and Filtering Circuits Previously, 50HZ/60HZ power transformers were not required. This type of power supply is called an off-line power supply.

What is the Oring Diodes?

A diode that isolates one power supply from another during a fault condition.

What is the Parallel Operation ?

 In order to output a larger current, the outputs of two or more power supplies can be connected together. When operating in parallel, each power supply must have a load sharing function.

What is the PARD ?

PARD: periodic and random offset, usually refers to the power supply output contains 20HZ ~ 20MHZ frequency components.

What is the Post Regulator ?

Post Regulator: Secondary stabilization circuit for the power auxiliary output.

What is the Preload ?

Preload: In order to make the power supply work stably, a load can be preset in the power supply. Usually the current supplied by the power supply to the load is small.

What is Stiff line ?

Stiff Line: AC power with low impedance. When the load changes, the input voltage of the power supply device will not change significantly.

What is the Topology ?

Topology: The type of circuit structure of the converter. Common converter circuit structures include flyback, forward, half bridge, full bridge, resonant and zero switching converters.