Inverter power supply

The reverse process of converting direct current into alternating current using a thyristor circuit, which corresponds to rectification, is defined as inversion. For example, in an electric locomotive using thyristors, when going downhill, the DC motor is used as a generator to brake and convert the locomotive's potential energy into electrical energy, which is then sent back to the AC power grid. For example, if a running DC motor needs to brake quickly, it can also be operated as a generator, converting the motor's kinetic energy into electrical energy and sending it back to the power grid.


Principle of inverter power supply

The circuit that converts direct current into alternating current is called an inverter circuit. In specific situations, the same set of thyristor converter circuits can be used for both rectification and inversion.

When the inverter is working in the inverter state, if the AC side of the inverter is connected to the AC power supply, the DC power is inverted into AC power of the same frequency and sent back to the grid, it is called active inverter. If the AC side of the inverter is not connected to the power grid but directly connected to the load, that is, the DC power is inverted into AC power of a certain frequency or adjustable frequency to supply the load, it is called passive inverter. AC variable frequency speed regulation works using this principle. Active inverter is not only used in DC reversible speed control systems, but also in series speed control of AC Rao Line rotor asynchronous motors and high-voltage DC transmission.

Inversion classification

There are also passive inverters for source inverters. For example, when a DC voltage passes through a simple single-phase H-type thyristor bridge, the horizontal axis of H represents the output, and there are four thyristors on the vertical axis of H, numbered 12 above and 34 below. By opening 14 and 23 respectively, positive and negative separated output voltage and current can be obtained.

Application of Pulse Width Modulation Technology in Inverter Power Supply

The basic square wave inverter power supply has a simple circuit, but the harmonic content of the output voltage waveform is too high, and the THD (current harmonic distortion rate) is also too high; The harmonic content of the output voltage waveform of the phase-shifting multi overlap inverter power supply is small, that is, the THD is small, but the circuit is more complex. The PWM pulse width modulation inverter power supply, which has both computer circuits and can output voltage waveforms, has been widely used.

The so-called PWM Pulse Width Modulation (PWM) technology uses a reference wave (usually a sine wave, sometimes a trapezoidal wave or a sine wave or square wave injected with zero sequence harmonics) as the modulating wave, and a triangular wave (sometimes a sawtooth wave) with a frequency N times that of the modulating wave as the carrier wave for waveform comparison. A set of equal amplitudes is generated in the part where the modulating wave is larger than the carrier wave, The rectangular pulse sequence with a width proportional to the modulation wave is used to equivalent the modulation wave, replacing the analog signal with a switching quantity, and converting direct current into alternating current through on/off control of the inverter power supply switching tube. This technology is called pulse width control inverter technology. Due to the linear variation of the amplitude of the carrier triangle wave (or sawtooth wave), this technology is called pulse width control inversion technology. Due to the linear variation of the upper and lower widths of the carrier triangle wave (or sawtooth wave), this modulation method is also linear. When the modulation wave is a sine wave, the pulse width of the output rectangular pulse sequence changes in a sinusoidal pattern. This modulation technique is commonly referred to as sinusoidal pulse width modulation (PWM) technology.

Common problems with inverter power supply

U is affected by external interference

Inverters may be affected by strong electromagnetic waves in their usage, such as nearby motors, power inverters, strong magnetic fields, etc.

Try to stay away from devices similar to those above.

The inverter is not responding

1. The battery and inverter are not properly connected, please reconnect them.
2. The polarity of the battery is reversed and the fuse is blown. Replace the fuse.

U output voltage low

1. Overload, if the load current exceeds the nominal current, turn off some loads and restart.
2. The input voltage is too low. Ensure that the input voltage is within the nominal voltage range.

Low voltage alarm

1. The battery is out of charge and needs to be charged.
2. If the battery voltage is too low or there is poor contact, recharge and check the battery terminals or clean them with a dry cloth.

U inverter has no output

1. The battery voltage is too low. Recharge or replace the battery.
2. The load current is too high. Close some loads and restart the inverter.
3. Inverter over temperature protection. Let the inverter cool down for a period of time and place it in a ventilated area.
4. Inverter failed to start, restart.
5. If the terminals are reversed and the fuse is blown, replace the fuse.

U inverter not working

Check the power switch, fuse, and battery connection wires or the range hood.

Inverter has no DC input

The common cause of such faults is that the battery is not properly connected. The positive and negative poles of the inverter must be correctly connected to the battery, with the positive pole connected to the positive pole and the negative pole connected to the negative pole. After the correct connection, the switch is closed, and this type of fault can be basically solved.

Inverter input/output fuse blown

This type of malfunction is generally evident and can be easily detected by replacing the fuse.

The battery voltage is 20% higher than the rated DC input voltage

The inverter has a working voltage range, generally between+-10% of the rated DC voltage. If the voltage exceeds this range, the battery pack or inverter needs to be replaced to prevent damage to the machine.

The battery voltage is 15% lower than the rated DC input voltage

This type of problem is mainly due to insufficient battery power, and only the battery pack needs to be charged.

Excessive load power

This type of problem is mainly caused by insufficient calculation of load power in the early stage, which requires increasing the power of the inverter or reducing the load power.

Type of inverter power supply

The inverter power supply includes:

●Power specific inverter power supply
●Communication specific inverter power supply
●Power type power frequency inverter power supply
●Industrial sine wave inverter power supply
●Square wave inverter power supply
●The role and characteristics of medical inverter power supply

Most medical equipment in China is powered by 220V mains electricity. Due to the power supply needs of various types of medical equipment, centralized power supply structures are the most commonly used. The output voltage of various voltage levels required is generated by a centralized power converter. Due to its low cost, high efficiency, adjustable output voltage, low output noise, and fast dynamic response, it is very suitable for use in medical equipment and is currently the most commonly used power supply method for medical equipment. The determination of the power supply scheme for medical equipment needs to consider the following issues.

Safety and isolation are a significant difference between ordinary commercial power sources and medical power sources. Usually, except for some experimental and analytical instruments, medical equipment is mostly installed near the hospital bed or operating table, close to people and operators, and the outer shell is often touched. There are various strong and weak electrical components inside medical equipment. If there is a problem with the isolation between strong and weak electrical components or the insulation of the casing material, it can be very dangerous. In terms of safety testing, general medical equipment power supplies must obtain safety certifications such as UL60601-1, C-UL, EN60601-1, etc. The input and output terminals must have an isolation voltage of 4000V or above, and low ground leakage current is required to comply with safety regulations for creepage distance. For strong electrical parts, double insulation is required, especially for parts that may come into contact with the equipment casing, and insulation design should be strengthened.

Electromagnetic compatibility and anti-interference ability

To select or build a good power supply system for medical equipment, attention must be paid to improving the electromagnetic compatibility and anti-interference ability of the power supply. We should mainly consider the following aspects: design. The design and layout of PCBs generally contain high-frequency signals in power supplies. Any printed wire on a PCB can act as an antenna, and the length and width of the printed wire can affect its impedance and inductance, thereby affecting frequency response. Printed wires that pass through DC signals in a timely manner can also couple from adjacent printed wires to RF signals and cause circuit problems. So medical power supplies must choose products from large brands and companies with strong research and development capabilities, which can ensure good quality in design and production processes.

Application of inverter power supply

Inverters are widely used in various fields such as power, communication, industrial equipment, satellite communication equipment, military vehicles, medical ambulances, police cars, ships, solar and wind power generation.

shield
The best way to suppress the radiation generated by switch mode power supplies and eliminate the impact of electromagnetic interference on other electronic devices inside medical equipment is to shield the magnetic field of the power supply, and then connect the entire shielding cover to the casing or ground of the medical equipment. This is a twice the result with half the effort.

authentication
At present, general medical equipment power supplies need to undergo electromagnetic compatibility and anti-interference ability tests such as FCC-B, CISPR22-B, EN55011550226120461000, etc. Choosing products that complete these tests not only ensures that there is no electromagnetic impact on other electronic components inside the device, but also reduces the development cycle of medical devices and the time required for testing before they are launched into the market.

Size and high power density
Medical devices are not only developing towards multifunctionality, high detection and adjustment accuracy, but also towards smaller size and portability. This requires medical equipment power supplies to have higher power output under smaller board area conditions.

Special applications
Most centralized power supply products on the market have standard outputs. Even if some power supply products can be adjusted through external circuits, the adjustment range is not large, and there are also stability issues. How to deal with low voltage, high current, or extremely high DC voltage situations? Of course, customized methods can be used, but the price is quite high. Can customers accept it.

price
Nowadays, due to fierce competition, the prices of medical equipment have gradually become transparent, especially for some small household medical devices, which have become very affordable and popular. So this requires an important component of medical equipment - the power supply - to have a competitive price.

The purpose of inverter power supply

Inverters are widely used in various fields such as power, communication, industrial equipment, satellite communication equipment, military vehicles, medical ambulances, police cars, ships, solar and wind power generation.