How does a linear programmable power supply work? What is the design principle?
Programmable power supplies are widely used in testing and measuring a variety of electronic products and are expanding into other industries as well. Programmable power supply is used in traditional electroplating industry, which can greatly improve the quality and automation of electroplating products. Reduce expense. In addition, due to the high efficiency of programmable power supplies, energy consumption in many traditional industries can be greatly reduced.
Next, we'll describe how a linear programmable power supply works.
The basic design model of a power supply includes rectifier and load devices and control components connected in series.
Simplified circuit diagram of a series rectified power supply. It consists of a pre-regulator (as a circuit breaker) for phase control and a variable impedance series element. A phase-controlled pre-regulator minimizes power dissipation by maintaining a stable low dropout across series elements. A feedback control circuit continuously monitors the output of the power supply and adjusts the series impedance to stabilize the continuous output voltage.
The series variable resistance device in a power supply actually consists of one or more power transistors operating in a linear mode, so a power supply using this type of rectifier is often called a linear power supply. Linear power supplies have many advantages. With its high stability and low noise, it is the easiest and most effective power solution on the R&D bench.
The power supply is a dual-range power supply that can have a higher voltage when the current is lower and a higher current when the voltage is lower. With a conventional single-range power supply, the output power is at its maximum only when both the voltage and current outputs are at their maximum. A linear power supply with two sections can provide maximum output power where the two sections have maximum voltage and current output. When using a dual range power supply, there is a tap in the middle of the secondary cable from the main transformer, near the terminal plug. A switch in front of the pre-regulator can be toggled directly between these two outputs, and the rear output is already determined. High voltage, low current mode or low current-high voltage mode. This technique is very effective in reducing the power consumption of serial devices.
In terms of performance, linear power supplies have excellent source and load characteristics and can respond quickly to grid and load changes. Therefore, line regulation, load regulation 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 ambient temperature changes, and high reliability.
In a programmable linear power supply, a digital control circuit controls the output control level of the DAC to directly control the programmed voltage value of the power supply. The output of the power supply will simultaneously send a voltage to the control circuit to indicate it has the desired output voltage. After the control circuit receives the voltage information from the output terminal, it sends the information to the display. In a similar manner, the control circuit also notifies 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 opto-isolation is used between the control circuitry and the power supply.
Linear DC power supplies are very complex to design and perform very well. However, the main problem is the relatively low efficiency. At full output power, efficiency typically does not reach 60%. If the output voltage is set lower, the efficiency will be further reduced. As power increases, volume and weight also increase proportionally. Therefore, switch-mode power supplies are more often used in high-performance power supplies.
