Structural analysis of high frequency switching power supply circuit

Short switching regulated power supply switching power supply (Switching PowerSupply), adjust the voltage regulator in the power supply control device always switch mode, named after the. It is using modern power electronic technology, by control switch tube pass broken of time ratio to maintained output voltage stability of a power, has volume small, and weight light, and power small, and efficiency high, and sheath boxiaoyao noise low, and intelligent of degree high, and easy expansion, fine characteristics, widely application in such as computer, and color TV, and PABX, and camera, and VCD, and electronic game machine, electronic device Shang. With the development of power electronics technology, especially the rapid development of the technology of high power devices, switching power supply operating frequency up to 150~200 kHz, switch power supply with good stability and high levels of price/performance, therefore switching power supply will increasingly replace linear adjustment of frequency transformer power supply.




Switching power supply circuit, the most critical part is the high-frequency converter and power controller. But as integrated switching power supply controller has general application, its control of the switching elements depending on the structure of high-frequency converter circuit, so the core is a high-frequency switching power supply circuit converter, DC Thill DC  JVC GZ-MS240 Battery Charger  converter. Input-output isolation in the switching power supply, high-frequency converter 5 kinds of basic forms of single-end Flyback single-ended forward Yao, half-bridge, push-pull, and full-bridge. Below displays, analysis of the structure and working principle of high-frequency circuit.

1, forward converter circuit

Structure of the forward converter circuit as shown in Figure 1 (a) below. Because of its energy storage components and load resistance RL series also known as in-line transfer network.

The circuit DC voltage Ui is by workers frequency AC power by power filter device, and rectifier filter Hou conversion get; power switch tube S1 for insulated grid double very type transistor (IGBT) or MOSFET;T for high frequency transformer; l and C1 composition LC filter; diode D1 for half wave rectifier components, D2 for continued flow diode; RL for load resistance; Uo for output stability of DC voltage. S1-driven signal vgs1 circuits for PWM control output of the square wave. Link voltage waveforms in Figure 1 (b) as shown in.

(B) wave

Forward transform circuit

Vgs1 for higher level S1 breakover, transformers have the input voltage is vT1=ui, diode D1 passes D2 due Yuan, power supply transformer coupled to the load energy, get the voltage on the load, filter inductance l energy. S1 deadline when control circuit, switching tubes withstand voltage equal to the input voltage of the S1, vs1=Ui, transformer primary, Vice-side output voltage is zero. At this point, the transformer original side S1 breakover stored energy through the coil and diode D3 N3 anti-returned to power. Deputy because the output voltage of the transformer is zero, so the diode D1 as, inductance l through diode D2 continued to load and release energy, because the filter function of capacitor C1, you get voltage on the load remains the same, the output voltage

Type: n transformation ratio of the transformer;

D is the square wave duty cycle;

N1, N2, for the number of turns of the winding of transformer primary, Vice.

(1) shows that output voltage Uo only by the supply voltage Ui and square wave duty cycle d decisions.

Forward transform circuit structure is simple, easy to implement, can be applied to small and medium-sized power switch power supply.

2, single-end Flyback conversion circuits

Shown as single-ended Flyback conversion circuits, high frequency transformer inductance l t both isolation and flow of Zeugma, because it is energy storage components of l with load RL is parallel, also known as the parallel circuit. Also you can determine, with different forward converter circuit, transformer cores of magnetic hysteresis loop of the other side, it is called a flyback converter circuit.

Figure 2 Flyback conversion circuits

When the power control circuit interrupter S1 breakover, as port of the same name, diode D1 is not on. When S1 deadline, Deputy of Nikon Coolpix 4500 Battery Charger winding of the transformer EMF induced reverse, the D1 leads, to charge the capacitor and voltage on the load RL. In this circuit, control, Deputy winding design of base, are required to follow the principle of Flyback.

Similarly, the switching voltage of the tube S1 and equal to the input voltage of the transformer and power supply input voltage, like the Flyback circuit with the circuit, structure is simple, easy to implement, can be applied to medium and small power switch power supply.

3, the push-pull converter electric circuit

Push-pull converter electric circuit is actually a combination of two single-ended forward converter circuit working in push-pull mode, the circuit as shown in Figure 3, two power switch turn on-the tube S1 and S2. Its work as follows: when S1 breakover, S2 deadline, according to the port with the same name can tell only D2 breakover, Panasonic DMW-BCJ13PP Battery Charger current through l electricity to RL, deadline when S1, S2 breakover, can be awarded, only D1 breakover current continues to flow through the l to the RL-powered, so get the current RL is continuous.

Push-pull converter electric circuit

As can be seen, switching tube voltage and equal to the input voltage of the transformer and power supply input voltage, transformer cores in magnetic hysteresis loop on each side. Push-pull converter electric circuit structure is relatively complex, demands on driving circuit of high output power is greater, applies to medium and high power switching power supply. So, the circuit has been widely applied.