With the advancement of electronic technology and the development of electronic products, some systems often require a negative voltage to supply power. For example, in a high-power inverter, a negative voltage is used to provide a shutdown negative voltage for the IGBT; in addition, in the operational amplifier of the system, a positive and negative symmetrical bias voltage is also used to supply power thereto. How to generate a stable and reliable negative voltage has become a key issue for designers.
Negative voltage design has many different solutions according to different load currents. The following are some common negative pressures on the market, which can be used according to different applications.
First, the power frequency transformer output positive and negative voltage
Figure 1 Power frequency transformer positive and negative output power
Do you see that the circuit in Figure 1 has a strong intimacy, can you think of the situation when you are in contact with electronic design at university? The advantages of this classic circuit are obvious, the circuit structure is simple, the interference noise is very low, and the stability is good. At the same time, this circuit has the disadvantages, the input AC power range is narrow (generally 220VAC±5%), and the volume and weight are large; although the disadvantage of this circuit is obvious at present Some applications are designed with this approach. This solution mainly uses a transformer to generate a negative voltage and is regulated by a linear regulator 7905.
Second, the power module output negative voltage
As the electronic component manufacturing process technology is getting better and better, the energy loss is getting lower and lower, which is more and more conducive to the modular development of the power supply. Moreover, it is also possible to achieve miniaturization and light weight design.
1, non-isolated negative voltage output negative voltage
Figure 2 Non-isolated regulated output module
Figure 3 Positive and negative output connections of non-isolated modules
As shown in Figure 3, this power module application is similar to the popular LM7805 and does not require the mounting of heat sinks. As shown above, when we need positive and negative voltages to supply power to the op amp, only two ZY78xxS-500 power supplies are required.
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