How to control the output power and output voltage of the switching power supply

Controls the output power of the switching power supply.

and output voltage solutions.

Both parameters are adjusted for pulse width.

to finish. In fact, the voltage is constant, such as 12 volts, and when the load is not connected, the pulse width is adjusted to the minimum direction until the output voltage is 12 volts. This is the minimum maintenance pulse width.

When the load is connected, the voltage drops immediately, because the output current becomes larger, and the pulse width needs to be increased to 12 volts.

When the pulse width reaches a certain level, it can no longer be adjusted upward, because no matter how wide the transformer is, the efficiency becomes very low, and even the transformer and power components can be damaged. In this case, the overload protection state is immediately entered. To put it simply, if you adjust the pulse width to the maximum value or can't reach 12 volts, it will be overloaded.

There is also a situation, that is, short-circuit protection, that is, to adjust the pulse width, its voltage does not change, it is always 0 volts, this situation will immediately enter the short-circuit protection.

Because the switching power supply is always adjusted upwards from the minimum pulse width, and as long as it is from a regular business, or the chip used by itself has overload and short circuit protection, it is very safe.

The output power of the switching power supply is controlled by controlling the output current and output voltage.

The constant current source circuit can be used for the control of output current, and the constant voltage source circuit can be used for the control of output voltage.

In the switching power supply, the sampling resistor is connected in series in the output circuit, and when the output current exceeds the rated value, the voltage on the sampling resistor makes the feedback circuit act and closes the first circuit of the switching power supply.

The output voltage is regulated by a negative feedback loop controlling the width of the switching pulse.

The 250W switching power supply is generally 70% without PFC power factor, and 98% with APFC power factorThe efficiency of today's switching power supply is generally more than 85%.

In this way, we can know that the maximum input current of 220VAC should be 250 85% 70% 220 = When selecting the switch, there should be rainfall, that is, the switch of 3A should be selected.

The output current of the switching power supply is determined by the internal current stabilization and current sampling feedback circuit of the power supply.

The maximum rated output current value of the switching power supply is determined by the internal power fiber vertical rate device and the current sampling feedback loop of the power supply.

Constant voltage switching power supply: i u r, u constant. Therefore, its actual output current is determined by the load, but the maximum cannot exceed its rated current.

Switching power supplies are made use of modern power electronics.

Control the switch.

The ratio of turn-on and turn-off time is a power supply that maintains a stable output voltage, and the switching power supply is generally modulated by pulse width.

PWM) control IC and MOSFET configuration. Compared with switching power supplies and linear power supplies, the cost of both increases with the increase of output power, but the growth rate of both is different.

The maximum output power of the switching power supply refers to the maximum power that the switching power supply can output stably under full load conditions. In order to test the maximum output power of switching power supplies, it is possible to test equipment such as electronic loads and power supply loads. Here are some specific steps to test the maximum output power of a switching power supply:

1.Prepare test equipment, including electronic loads, power loaders, digital voltmeters, and digital ammeters. 2.

Connect the power output to the input interface of the electronic load or power supply loader, and connect the output of the load to the input interface of the load. 3.Set the voltage and current parameters of the test equipment to the maximum value under full load as the test target, which needs to be adjusted according to the actual use case and specification requirements.

4.Start the switching power supply, and gradually increase the load current, record the change value of voltage and current, until the power output is unstable or the load does not increase again, then the recorded current and voltage values are the maximum output power of the switching power supply. It should be noted that in the test, it should be avoided to change the current and voltage parameters in a short period of time, and keep the test equipment and equipment synchronous adjustment parameters to avoid equipment damage and inaccurate test results.

First of all, your switching power supply transformer is in accordance with the current design, even if it is changed, it is not recommended to exceed 10% of the range, beyond the range is easy to damage the switch, or can not meet your voltage stabilization needs, change the resistance value of the voltage feedback resistor, is to change the sampling circuit part, but some circuits with chain state cherry overvoltage protection, you also have to change the protection part of the components, specifically according to the actual circuit to make changes.

Voltage, also known as potential difference or potential difference, is a physical quantity that measures the difference in energy between a unit charge in an electrostatic field due to different potentials. Its magnitude is equal to the work done by a unit positive charge to move from point A to point B due to the action of an electric field force, and the direction of the voltage is specified as the direction from the high potential to the low potential.

The SI unit system of voltage is volts (V, referred to as volts), and the commonly used units are microvolts (MV), microvolts (V), kilovolts (kV), etc. This concept is similar to the "water pressure" caused by the high and low water level. It should be pointed out that the term "voltage" is generally only used in electrical circuits, while "potential difference" and "potential difference" are generally applied to all electrical phenomena.

The voltage is controlled by the pulse width duty cycle, and the corresponding current is generated when the load is connected.

The switching power supply is generally constant voltage and current limiting, and it is impossible to achieve constant voltage and constant current at the same time. If both voltage and current are constant, it only means that the load is a constant value (according to Ohm's law r = u i, the same is true for reactant loads). When the output voltage is too high, the duty cycle of PWM is reduced, that is, the high-level on-time is reduced. When the output voltage is too low, increase the duty cycle of PWM.

If the load far exceeds the supply capacity of the switching power supply, then there will inevitably be an overcurrent (maybe the switching power supply increases the output current to the maximum capacity, but the voltage just can't reach the set voltage), then the switching power supply will stop the output in order to protect the switch from being burned, and the switch will be closed. A well-functioning switching power supply may be switched between constant voltage and constant current, but it can only be switched to one of them, that is, it can work in one of the ways.