Program-controlled power supplies are widely used for testing and measuring various electronic products, and are also being expanded to other industries. Programmable power supplies are used in the traditional electroplating industry, which can greatly improve the quality and automation of electroplating products. Reduce expense. In addition, due to the high efficiency of the programmable power supply, the energy consumption of many traditional industries can be greatly reduced.
Next, we will introduce the working principle of the linear programmable power supply .
The basic design model of the power supply includes a rectifier and load equipment, as well as control components connected in series.
Figure 1 is a simplified circuit diagram of a series rectified power supply. It contains a pre-regulator for phase control (as a circuit breaker) and a variable impedance series element. The phase-controlled pre-regulator minimizes power consumption by maintaining a stable low pressure drop across the series components. The feedback control circuit continuously monitors the output of the power supply and adjusts the series impedance to stabilize the continuous output voltage.
As shown in Figure 1, the series variable resistance device in the power supply is actually composed of one or more power transistors operating in a linear mode, so the power supply using this type of rectifier is usually called a linear power supply. Linear power supplies have many advantages. It has high stability and low noise, and is the simplest and most effective power supply solution on the research and development workbench.
The power supply shown in Figure 1 is a dual-range power supply. When the current is low, the power supply can have a higher voltage; when the voltage is low, the power supply can have a higher current. For a conventional single-range power supply, the output power reaches the maximum value only when the voltage and current output both reach the maximum value. A linear power supply with two parts can provide the maximum output power when the two parts have the maximum voltage and current output. When using a dual-range power supply, there is a tap in the middle of the secondary cable of the main transformer, close to the terminal plug. The switch in front of the pre-regulator can be switched directly between these two outputs, and the back-end output has been determined. High voltage, low current mode or low current-high voltage mode. This technology is very effective in reducing the power consumption of serial devices.
In terms of performance, linear power supplies have excellent power and load characteristics, and can react quickly to changes in the power grid and load. Therefore, the power regulation rate, load regulation rate and transition recovery time are better than most switching power supplies. Linear power supplies have many other advantages, such as extremely low ripple and noise, tolerance to environmental temperature changes, and high reliability.
In the programmable linear power supply, the digital control circuit controls the output control level of the DAC to directly control the programming voltage value of the power supply. The output of the power supply will simultaneously send a voltage to the control circuit to indicate that it has the required output voltage. After the control circuit receives the voltage information from the output terminal, it sends the information to the display. In a similar way, the control circuit also informs other devices of the input and output status of the power supply unit through a PC interface (such as GPIB, RS-232, USB or LAN). These PC interfaces are directly grounded, and optical isolation is used between the control circuit and the power supply.
The linear DC power supply design is very complicated, and the performance is also very good. However, the main problem is the relatively low efficiency. At full output power, the efficiency usually does not reach 60%. If the output voltage is set lower, the efficiency will be further reduced. As the power increases, the volume and weight also increase proportionally. Therefore, switch-mode power supplies are more often used in high-performance power supplies.