Flat power supply features, maintenance and replacement of key components (1) - Power Circuit - Circuit Diagram
There are many types of flat-panel power supplies, many types of devices are used, and the probability of failure is high. In flat-panel TVs, power-induced faults account for the vast majority of TV faults. Although there are many types of flat panel power supplies, many of them (such as oscillation, voltage regulation, overvoltage, overcurrent detection, etc.) work the same way as CRT switching power supplies. In contrast, the difference is that a large number of active PFC circuits and rectification and filtering circuits of various structures are added to some circuits. There are many types of flat-panel power supplies because different circuit topology combinations are chosen during design. Different chips and different circuits are matched to form various switching power supplies. These topologies include BOOST boost DC-DC converter circuits, LLC resonant half-bridge topology circuits, push-pull topologies, half-bridge topologies, full-bridge topologies, flyback converters, and more. As long as we master the characteristics and working process of these topological circuits, we basically master the working principle and maintenance of all flat panel TV switching power supplies. From the beginning of this issue, we will introduce the working characteristics, maintenance and device replacement of the common topology power supply of the tablet for maintenance personnel's reference.
Flat panel power supplies are often divided into two types: single power supply and two-in-one power supply. Single power supply refers to a switching power supply that only provides the operating voltage of the main board and backlight module (drive). This type of power supply is usually powered by a secondary power supply (which generates 5VSTB voltage required for the control system to work), and a PFC correction circuit (300V formed by conventional full-bridge rectification). The DC voltage is increased to 380V), and the main power supply (which generates the voltage required for the motherboard and backlight circuit) is composed of three parts. The 2-in-1 power supply adds a backlight driving circuit to the original single-supply circuit.
First, one of the switch topology: BOOST boost DC-DC converter circuit
1. Circuit configuration
See Figure 1. The biggest feature of the BOOST boost DC-DC converter circuit is that the output voltage is always higher than the input voltage, and the input and output share a ground.
2. work process
When the switch tube T is turned on, the current IL flows through the inductor L, the current increases linearly, and the electric energy is stored in the inductor coil in the form of magnetic energy. When the switch tube T is turned off, the magnetic energy in the coil will change the polarity of the voltage VL across the coil L to ensure that the current IL does not abruptly change. Thus, the voltage VL converted by the coil L is connected in series with the power source Vin and supplies power to the capacitor Cout and the load at a voltage higher than the output.
The purpose of designing diode D1 in the circuit is to pre-charge the large capacitor and have anti-surge impact function, so D1 is used to protect PFC boost diode D. The choice of this diode is related to the size of the large capacitor, the level of the AC input voltage, and the impedance of the AC input loop. The commonly used diode is 1 N5408. 01 The N5408 has an IFSM of 200A. In high-power power supplies, two 1N 5408s can be used in series to increase the reliability of the power supply.
3. Circuit application
BOOST boost DC-DC converter circuits are commonly used in PFC correction circuits for switching power supplies. Why should the switching power supply add a PFC circuit? This is a need for energy savings. The state has mandatory requirements: equipment with rated power of 75W or less does not have harmonic current limitation; equipment with rated power greater than 75W needs to limit harmonics, and the circuit must be equipped with PFC circuit. The PFC circuit structure has DCM (discontinuous conduction mode, in the interrupt mode converter, the inductor current is zero at some moments of the cycle), CCM (continuous conduction mode, the inductor should have any time in the cycle) Current flows through) and interleaved modes. When the input power is below 250W, the PFC adopts the DCM circuit structure; when the input power is above 250W, the CCM structure is selected; when the circuit needs to focus on the layout and size, the interleaving mode is adopted.
[3]
Wake up naturally in the morning sun, give you moisturizing company from morning to night, relax at home, and give you inseparable moisturizing. It is a good helper to relieve the pressure of dryness and water shortage, and the secret magic weapon to improve work efficiency.Delicate water particles can reach the bottom of the skin to be delicate and moisturizing, and the deep hydration makes the skin absorb water like a sponge.
Office Humidifier,Office Building Humidifier,Office Humidifier For Desk,Commercial Office Humidifier
Dongguan Yuhua Electronic Plastic Technology Co.,Ltd , https://www.yuhuaportablefan.com