PSR is the abbreviation of English Primary Side Regulator, which means the primary side feedback control or primary adjustment, that is, the error amplifier is placed inside the IC, and the voltage regulator circuit composed of common three-terminal precision voltage regulator TL431 and optocoupler PC817 is omitted. .
Advantages, disadvantages and classification of a PSR
The PSR architecture has a simple circuit, no optocoupler, CC/CV advantages, and low cost, and is very popular in low-power chargers and LED constant-current drive circuits.
In the high-power power supply, the current PSR control IC constant current effect is far less than the secondary feedback control accuracy, and the price is similar to the secondary feedback, so there is no market advantage.
The PSR IC can be roughly classified into the following three aspects: (1) whether there is a built-in high-voltage MOSFET, such as: CR6238T built-in high-voltage MOSFET, and OB2520D does not have a built-in MOSFET; (2) whether the control mode is digital or analog, for example : IW3620 is digitally controlled, ACT361 is analog control; (3) is working in CCM or DCM mode, for example: LNK406 belongs to CCM mode, and FSEZ1317 belongs to DCM mode.
Second, the working principle analysis Although the different types of PSR circuits are different, but the working principle is roughly the same, but some parameters are not the same definition, the following FSEZ1317 as an example, such as its typical application circuit shown in Figure 1.
In CV mode, most PSR chips directly sample the voltage on the auxiliary coil. Due to the leakage inductance, after the MOSFET is turned off, that is, the secondary diode DR turns on, a spike will be generated, which will affect the voltage sampling. To open this spike, most chips use a time-delay sampling method, that is, the voltage on the sampling coil is turned off after the MOSFET is turned off for a period of time, thereby avoiding leakage inductance spikes. The FSEZ1317 is sampled after the switch is turned off for 4.5 μs, as shown in Figure 2. In fact, many power supply chip overvoltage protection circuits also use the above-mentioned delayed sampling methods, such as OB2203, UCC28600, NCP1377, etc., because this can get higher precision sampling values.
In addition, the snubber circuit generally consists of a diode 1N4007 with a recovery time of about 2 μs, and a resistor with a resistance of 100 Ω in series, which reduces the ringing of the leakage inductance and reduces the sampling error. Some PSR chips use a small capacitor in parallel with the downsampling resistor to achieve delayed sampling.
According to the working principle of the transformer, Np xIpk=Ns xlpks can be obtained (the transformer secondary has only one winding Ns), and Np, lpk, Ns, and Ipks represent the primary coil turns, the primary peak current, the secondary coil turns, and the secondary peak current, respectively. .
When operating in DCM mode, the primary and secondary current waveforms of the switching transformer are shown in Figure 3. The output current lo is the average value of the secondary current in one duty cycle, ie Io = (Td / T) x Ipsk / 2, where T is Working period. Since Ipks = Np x lpk / Ns, then lo = (Td / T) x (Np x Ipk / Ns) / 2. It can be seen that Np and Ns are constants, and a fixed current output can be obtained by fixing the Ipk and Td/T values, that is, achieving a constant current output.
The way many ICs fix Ipk on the market is to limit the peak voltage on the MOSFET's sampling resistor. At the same time, in order to avoid the current spike generated when the parasitic capacitance is turned on, a blanking time is added. The Td/T value is fixed internally by the IC, such as the OB series IC having a Td/T value of 0.5.
In CC mode, under different output voltage conditions, working in PFM mode to ensure a fixed Td / T to achieve a stable output current, which is the basic principle of achieving constant current. As long as the accuracy of the Td/T value of the IC and the current limit accuracy of the primary peak current are ensured, a higher output current accuracy can be obtained. These two parts basically depend on the IC itself.
A lithium-ion battery or Li-ion battery (abbreviated as LIB) is a type of rechargeable battery. Lithium-ion batteries are commonly used for portable electronics and electric vehicles and are growing in popularity for military and aerospace applications.Lithium batteries feature primary cell construction. This means that they are single-use-or non-rechargeable. Ion batteries, on the other hand, feature secondary cell construction. This means that they can be recharged and used over and over again.Li-ion batteries are able to be recharged hundreds of times and are more stable. They tend to have a higher energy density, voltage capacity and lower self-discharge rate than other rechargeable batteries. This makes for better power efficiency as a single cell has longer charge retention than other battery types.The li-ion battery disadvantages include: Protection required: Lithium ion cells and batteries are not as robust as some other rechargeable technologies. They require protection from being over charged and discharged too far. In addition to this, they need to have the current maintained within safe limits.The typical estimated life of a Lithium-Ion battery is about two to three years or 300 to 500 charge cycles, whichever occurs first. One charge cycle is a period of use from fully charged, to fully discharged, and fully recharged again.
Lithium Ion Battery Charger,Lifepo4 Lithium Ion Battery,Lithium Ion Battery 18650,Lithium Ion Battery 100Ah
Shenzhen Glida Electronics Co., Ltd. , https://www.szglida.com