The voltage regulator is composed of a voltage regulating circuit, a control circuit, and a servo motor. This is the basic structure of the voltage regulator. In order to enhance the understanding of the regulator, this paper will introduce the effect of linear regulator and the characteristics of linear regulator. If you are interested in regulators and linear regulators, you may wish to continue reading.

1. linear regulator

A linear regulator uses a transistor or FET operating in its linear region to subtract the excess voltage from the applied input voltage to generate the output voltage through scheduling. The so-called drop voltage refers to the minimum value of the difference between the input voltage and the output voltage required by the regulator to adhere to the output voltage within 100mV above and below its additional value. A positive output voltage LDO (low dropout) regulator typically employs a power transistor (also known as a pass device) as the PNP. This transistor allows fullness, so the regulator can have a very low drop voltage, generally 200mV distribution; in contrast, the use of NPN composite power transistor of the traditional linear regulator voltage drop of 2V distribution. Negative output LDO using NPN as its transfer device, the operation method and the positive output LDO PNP device is similar.

2. linear regulator effect

The excellent interest of the linear regulator is the lowest cost, the lowest noise and the lowest quiescent current. Its peripheral equipment is also very few, generally only one or two bypass capacitors. The new linear regulator can reach the following policies: 30μV output noise, 60dB PSRR, 6μA quiescent current and 100mV differential pressure. Linear regulator can complete these characteristics of the first element is the internal adjustment tube selected P-channel FET, rather than the PNP transistor in the general linear regulator. P-channel FET does not require base current drive, so the current of the equipment itself is greatly reduced. On the other hand, in the structure of PNP tube, in order to prevent PNP transistor from entering a full state and reducing output talent, it is necessary to ensure a large input and output voltage difference. The voltage difference of the P-channel FET is approximately equal to the product of the output current and its on-resistance, and the very small on-resistance makes the voltage difference very low. When the system input voltage and output voltage near, linear regulator is the best choice, can reach a very high power. So in the lithium-ion battery voltage change to 3V voltage in the use of most of the use of linear regulator, although the battery eventually discharge energy of ten percent is not used, but the linear regulator can still be in the low noise structure in the supply of longer battery life.

3. Linear Regulator Characteristics

The so-called anti-short-circuit talent request, refers to the short-circuit conditions in the relevant information, the regulator is not damaged. The anti-short-circuit talent of the voltage regulator includes two aspects: the heat-resistant talent of accepting short circuit and the dynamic stability talent of accepting short circuit.

After the voltage difference and grounding current value are determined, the type of equipment applicable to the voltage stabilizer can be determined. Each of the five major dry-current linear regulators has divergent bypass elements (passelement and function together, voltage difference and grounding current value are mainly determined by the bypass elements of the linear regulator (passelement. The use of different types of equipment is suitable for separation.

Even if there is no output capacitor, it is suitable for equipment with higher voltage difference. The interest of standard NPN regulator is to have a stable ground current approximately equal to the base current of PNP transistor. However, the high pressure difference makes this regulator unsuitable for many embedded devices.

NPN bypass transistor regulator is a good choice, on the embedded application, because it is small, simple use. However, this regulator is still not suitable for battery-powered equipment with very low differential pressure requirements, because it is not low differential pressure. The high gain NPN bypass tube can make the ground current stable in a few mA, and its common emitter structure has a very low output impedance.

4. why the regulator input can not be equipped with leakage protector

When using a voltage regulator, never use a leakage protector at the input of the voltage regulator. This is a major principle used by regulators.

Some users in the use of voltage regulator, the regulator selected the corresponding leakage protector or leakage switch. The end result is that when the voltage regulator starts, the leakage protector is protected and the voltage regulator cannot be used at all.

Why?

The principle of leakage protector is that the zero line current is zero. When using a voltage regulator, the current of the zero line cannot be zero.

There are isolation transformer and voltage regulating transformer inside the voltage regulator. 20kw voltage regulator, the transformer is equivalent to the capacitance effect when starting up. When starting up, the transformer and voltage regulator are instantly charged, resulting in zero line with current, forming a current loop. If a leakage protector is used at the incoming end, it will act, cutting off the input power supply and causing the voltage regulator to be unusable.

Therefore, please do not use the leakage protector at the input of the voltage regulator. If the customer insists on using the leakage protector at the output of the voltage regulator to ensure the safe use of the voltage regulator, the voltage regulator must be grounded.