Q:Electrical Engineering! Why can not directly use a multimeter to measure the power supply of the exchange of ripple?

In general, multimeter AC can only measure the pure AC voltage. The output voltage of the regulated power supply is equivalent to the DC voltage + ripple voltage, and the multimeter exchange file can not be measured normally. In addition, the ripple voltage is not necessarily a sine wave voltage, the regulated power supply itself or by external interference will produce complex ripple voltage, and the general multimeter AC voltage file is measured the average AC voltage. The ripple voltage is not a pure sine wave when the multimeter can not be accurately measured. From the other side, the general linear power supply can only guarantee the output voltage in the lower frequency range of stability, and for more than tens of kHz ripple rejection is very limited. That is, the ripple voltage frequency is generally higher, may have exceeded the multimeter AC file frequency response range, this time the multimeter is still unable to correctly measure.

Q:DC power supply through what way to achieve the purpose of regulation

DC power supply is generally divided into two categories, one is linear regulator, the common is to use a three-tube voltage regulator tube, by changing the transistor base voltage to adjust the output voltage to achieve the regulator output Purpose, generally used in low-voltage regulator circuit, the transistor work loss is great, relatively serious heat, generally need a larger heat sink, due to the transistor limit, the output circuit is generally less than 5A, greater than the current need to adjust the tube in parallel.

Q:What is the solution for a regulated power supply?

AC power supply voltage fluctuations in the main situation of the following two points: (1), the voltage fluctuated, can not be stabilized within the scope of the standard voltage permit; (2), the voltage continues to be high or low. The above two cases for the safety of electricity and electrical safety are a lot of unfavorable factors. With long-term work in such a voltage environment will cause air consumption increases, increased current consumption, reactive power is high, a serious rise in temperature, electrical appliances can not work properly and so on. More serious will burn the electrical, and even cause a fire!

Q:Switching power supply and DC power supply difference

DC linear power supply is relatively heavy, filter capacitor head large, the overall volume. DC linear power supply is to adjust the tube divider to reduce the output voltage, so the burden of regulating the tube is heavy, heat and efficiency is low. But the dynamic response is very good, suitable for changes in load more frequent places, such as audio amplifier. Switching power supply is relatively light weight, smaller size. Switching power supply is through the switch on and off the number of times or time to adjust the output power, efficiency than the linear power supply is higher, relatively small amount of heat, but the dynamic response is poor, suitable for more stable load place. Switching power supply filter capacitor due to the high frequency, so the interference of the power grid is very large.

Q:Half-bridge switching power supply and the commonly used by the three-terminal regulator block compared to the power supply, what are the characteristics

Switching power supply work in the conduction and cut off the two areas, the work of low heat, low power consumption

Q:With the transformer why DC power supply, DC power supply is 220VAC input, output 24VDC; transformer is 220V / 24V. Is this not repeated?

The transformer output is AC, must be rectified into DC to use; In addition, the rectification is only the direction of the DC, the size will change over time, so some of the voltage fluctuations in the case of strict control but also after the rectification Filter circuit and voltage regulator circuit,

Q:Is there a difference between a regulated power supply and a power adapter?

The first is the role of voltage regulator voltage is the second transformer power supply equipment

Q:What is the difference between regulated power supply and steady current power supply?

A steady voltage, a steady current. Stable voltage at rated power, the voltage is adjustable and can be fixed on a value. Does not change as the input changes.

Q:DC power supply technical indicators which

DC power supply specifications can be divided into two categories: one is the characteristics of indicators, reflecting the inherent characteristics of DC power supply, such as input voltage, output voltage, output current, output voltage adjustment range; the other is the quality indicators , Reflecting the advantages and disadvantages of DC power supply, including stability, equivalent resistance (output resistance), ripple voltage and temperature coefficient. 1, the characteristic index (1) output voltage range In line with the DC power supply operating conditions, the normal working output voltage range. The upper limit of this indicator is determined by the maximum input voltage and the minimum input-to-output voltage difference, and its lower limit is determined by the reference voltage inside the DC regulated power supply. (2) Maximum input - output voltage difference This indicator characterizes the voltage difference between the maximum input and output allowed under the normal operating conditions of the DC regulated power supply. The value depends mainly on the voltage regulation of the DC regulated power supply. (3) minimum input - output voltage difference This indicator characterizes the voltage difference between the minimum input and output required to ensure proper operation of the DC power supply. (4) Output load current range The output load current range, also known as the output current range, in this current range, the DC power supply should be able to ensure compliance with the indicators given by the indicators.

Q:Adjustable DC regulated power supply works

(3) filter circuit: the rectifier circuit output voltage in the majority of the AC component to be filtered, resulting in a relatively smooth DC voltage of the filter capacitor C to meet RL-C = (3 ~ 5) T / 2, or T For the input AC signal period, RL is the equivalent load resistance of the rectifier filter circuit. (4) voltage regulator circuit: the function of the regulator circuit is to stabilize the output DC voltage, does not change with the AC grid voltage and load changes. Commonly used integrated voltage regulator has a fixed three-terminal regulator and adjustable three-terminal regulator. Commonly adjustable adjustable positive pressure regulator with CW317 (LM317) series, their output voltage from 1.25V-37V adjustable, the simplest circuit external components only a fixed resistor and a potentiometer. The chip has a transition, overheating and safe working area protection, the maximum output current of 1.5A. The output voltage Uo expression: Uo = 1.25 (1 + R2 / R1) where R1 generally take 120-240 ohms, the output and the adjustment of the end of the output voltage regulator, the output voltage Uo of the expression: Uo = 1.25 (1 + R2 / R1) The differential pressure is the reference voltage of the regulator (typically 1.25V). I uploaded the principle of switching power supply and write the above design.