This is another form of transformerless AC power that can be used in some well-insulated, low-power devices. Our technical commentators believe that Cac should be a Class X security type; and I think it would be better if there was no grounding sign.
The Switch Mode Power Supply (SMPS) circuit can effectively reduce the mains AC power to meet the power supply requirements of the low voltage circuit. However, to achieve this feature, it is necessary to increase the control integrated circuit, switching transistor and inductor components. The figure below shows an easy way to reduce and adjust the AC power to the desired low DC voltage value using more common components. 
Figure: This buck converter achieves a lower DC voltage by lowering the AC supply voltage flowing through the Cac. The VUZ is an optional component and, for safety reasons, a higher wattage can be selected if necessary. The VU is an unregulated output voltage that can be further adjusted using a 7805/12 chip or a simple Zener transistor voltage regulator. Q1 should be chosen according to the power requirements. In essence, Q1 should be able to consume unused current without load. The value/type of the fuse is indicative and can be selected according to its design/need.
The AC voltage is reduced by reducing the unnecessary voltage of the capacitor (resistance Z = 1/C) Cac (with appropriate value and rated voltage). The remaining AC current flows through the diode bridge as a rectified output current. In this way, although the direct current flows through the output circuit of the bridge, the alternating current of the step-down series capacitor Cac flows in other parts of the circuit.
The value of the capacitor determines the current output under buck conditions. When the output current is large, a larger capacitor is required. The bleeder resistor (1MΩ) is connected in parallel with Cac. When the AC power is disconnected, the bleeder resistor can discharge Cac. After rectification and filtering, the DC power is shunted by the Q1 regulation circuit, which is mainly used to maintain the output voltage within a certain range.
There are two LED indicators in the circuit. The red LED indicates whether the AC is being used or is shunted by Q1 as waste. A green LED indicates the ability to add power to the output of the conditioning device.
R1, R2, and RB (R1, R2>>RB) form a voltage divider network that is primarily used to monitor residual rectified AC from the bridge. After setting the values ​​for R1, R2, and RB, when current flows through the load (not shown), Q1 turns off. Since the values ​​set for R1 and R2 are large, almost no current flows through the second bleeder resistor. . The level of buck in RB is not enough to illuminate the red LED. We call the current flowing through R1, R2 and RB at this time a housekeeping current, which can continue to flow without reaching the maximum load current value.
Affected by the R2 step-down voltage, the step-down voltage must be at least 0.6V to start Q1. During normal operation, current will flow through the load, setting the values ​​of R1, R2, and RB so that the step-down voltage is lower than 0.6V. However, if the load is disconnected from the circuit (no output current flows in), the voltage across the diode bridge will increase, causing the step-down voltage in R2 to rise continuously until the transistor turns on and introduces current through RB. At this time, the step-down voltage in R2 will stop rising, and the current flowing through the red LED will increase. A flashing red LED indicates power loss. The green LED will keep flashing when the power at the output is available. Setting a value for RB allows the voltage at the bridge to be within a reasonable range without load, and no higher than the upper limit of any final regulator connected to +VU.
The value of the required capacitor Cac is calculated as follows: 
Among them, IL is the maximum load current, Vrms is the rms AC voltage, and VE (~VU+1.2) is the residual expected voltage at the input of the bridge, which is the sum of Vu and 1.2V voltage in the bridge diode. ΔIL is the internal management current other than the maximum load current. The value of Cac is roughly estimated as: IL / (Vrms) (= 2πfAC), that is, ΔIL and VE in the formula are ignored; compared with IL and Vrms, the values ​​of ΔIL and VE are relatively small.
This circuit provides an alternative solution for large, noisy vibration field/electromagnetic fields/heat generating transformers. But the advantage of a transformer is that it provides isolation for live AC power. The danger of the circuit described in this paper is that Cac will short circuit. Therefore, precautions should be taken to fuse the fuse before the output voltage rises to a dangerous level. When the voltage is increased, the Zener VUZ and the filter capacitor CF provide an additional current path, and more cheap xenon lamps can be added to the bridge input to allow the output regulation circuit and load to function properly.
In a test designed to build a Zener transistor regulated 4.8V supply (current 5mA): a 240V AC line with Cac=0.068μF, R1=10kΩ, R2=470Ω, RB=470Ω, CF=470μF , Q1 = BC549. This power supply can power the 555 oscillator that drives the LEDs. In another test, Cac = 0.22 μF, R1 = 10 kΩ, R2 = 470 Ω, RB = 470 Ω, CF = 470 μF, Q1 = BC549, which can be used to construct a Zener transistor regulated 4.8V supply (current 15mA). The power supply can easily power 555 unsteady circuits, flashing LEDs, and CD4518 counters that can drive eight LEDs.
It should be noted that the reactance of Cac is usually much higher than the reactance of the power receiving circuit, and because of this, the power supply seems to be acting as a constant current source. This type of power supply helps to power low current (approximately 1 mA to 100 mA) circuits.
Vc Whitening Moisturizing Cleanser
Efficacy: complete removal of the skin of dirt, with whitening, Blemish effect, but also increase the skin's luster, make skin feel instantly cool.
Function Type: cleanser, cleanser
Skin: all skin types, has a good antibacterial effect, can effectively clean skin whitening. Cool-cool, so you vitality doubled.
Companies registered capital of 35 million yuan, the end of 2014 the total assets of 48.69 million yuan, including fixed assets of 37.52 million yuan. The company's existing cooperation Orange cultivation base 7043.5 acres, the company production base is located in Jiangxi County Tech Industrial Park Chu Tan industrial area, covers an area of 120 acres, it has built a standard plant 9,000 square meters, Nissan 6000 kg Orange enzymes and other liquid enzyme products. Enzyme, known as enzyme, refers to a polymer substance having biocatalytic functionality. In the catalytic reaction system an enzyme, the reactant molecules are known as substrates, enzyme substrates by catalytic conversion to another molecule. Almost all cellular activity of enzymes involved in the process are required to improve efficiency. Similar to other non-biological catalysts, enzymes chemical reactions by lowering the activation energy to accelerate the rate of the reaction, most of the enzyme catalyzed reaction rate can be increased a million times; in fact, the enzyme is to provide an activation energy needs than another low way, so that more particles to have less than the activation energy of the reaction kinetic energy, thus speeding up the reaction rate. Enzyme as a catalyst, in itself is not consumed during the reaction, it does not affect the chemical equilibrium reactions. Positive enzyme catalysis, but also a negative catalytic effect, not only to accelerate the reaction rate, but also to reduce the reaction rate. And other non-living catalysts is different, having a high degree of specificity of enzyme, only a catalytic reaction or produce a particular specific configuration.
Vc Whitening Moisturizing Cleanser,Remove Skin Dirt Cleanser,Fast Whitening Skin Cleanser,Effective Antimicrobial Blemish Cleanser
Ganzhou Green days Biochemical Technology Co., Ltd. , https://www.cn-gangdao.com