Switching

     Modifiers DC-DC power (DC-DC Converter) with the title chopper DC (DC Chopper) is used mainly to supply DC output voltage that varies the amount in accordance with demand on the load. Power input from DC-DC process is derived from the DC power source which typically have a fixed input voltage. Basically, the income of the DC output voltage is to be achieved by regulating the length of time the connection between the output and input side on the same circuit. Components used to perform a liaison function is none other than the transistor. In general there are two functions of the operation of the chopper DC (DC Chopper) that is raising the voltage where the resulting output voltage is higher than the input voltage, and a decrease in voltage where the output voltage is lower than the input voltage.

     To better understand the benefits of this type of transition, can be seen the principle of DC-DC power conversion of linear type as shown in Figure 1.

Figure 1 Modifiers linear type.

 

 

     In the linear type, the output voltage regulation is achieved by adjusting the current in the load depends on the large amount of current on the transistor base:  V₀ = I_L . R_L  

      Thus the linear type, the transistor functions like prisoners who can be changed also quantified as shown in Figure 1. Furthermore, the transistors that are used can only be operated on the linear constraints (linear region) and not exceed the limit cut-off and saturated regions (saturation region). Therefore this type is known as the linear type. Although the linear type is the easiest way to achieve varying output voltage, but less attractive in power applications because of the high power loss (power loss) at the transistor (VCE * IL) resulting in low efficiency. As an alternative, it appears the transition type, which in principle can be seen in Figure 2.

Figure 2. Modifier type transition.

 

      On the type of transition, visible transistor functions as electronic switches that can be opened (off) and closed (on). Assuming that the switches are ideal, if the switch is closed, the output voltage will equal the input voltage, whereas if the switch is opened, the output voltage will be zero. Thus the output voltage pulse generated will be shaped as in Figure5.

Figure 3. Voltage switching.

 

     The amount of the average or DC component of the output voltage can be derived from the following equation: 

 

     From the equation above shows that the DC output voltage can be quantified by adjusting the parameter D. The parameter D is known as the duty ratio is the ratio between the length of time the switch is closed (tons) with period T of the output voltage pulse, with 0 <D <1. Parameter f is the switching frequency (switching frequency) used in operating the switch. Unlike the linear type, the type of transition no power is absorbed in the transistor as a switch. This is possible because the switch is closed when no voltage is dropped on the transistor, while during the switch is opened, there was no electric current flows. This means that all power is absorbed in the load, so power efficiency to 100%. But remember, in practice, no switches are ideal, so it will stay there the slightest power loss in the switch components and the efficiency is very high though, will never reach 100%.