Published:2011/8/23 23:40:00 Author:Robert | Keyword: Power, Conversion, Switching, Regulator
The power conversion circuit of switching regulator power has many types such as push-pull, full-bridge, half-bridge and single-ended flyback and single-ended forward and other types. The picture shows the push-pull type power conversion circuit. The control circuit would control the base electrode of the transistors VT1 and VT2. The VT1 and VT2 would be alternately connected and disconnected with PWM excitation method. Then they would convert the input DC voltage to the high-frequency square-wave AC voltage. When the VT1 is conducted, the input power voltage Ui would be through VT1 and then it is added the high-frequency transformer T1's primary winding N1. Because T1 has two main windings N1 with equal number of turns, so when the VT1 is conducted, it adds twice power voltage 2UI onto the transistor VT2 which is in disconnected mode. (View)
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Published:2011/8/23 23:40:00 Author:Robert | Keyword: Voltage, Regulator, Power, Luoya, Method
The picture shows the Luoya method circuit which is suitable for the 220V input. The picture (b) is suitable for 380V input. For example in the circuit shown in picture (a), the R1 is starting resistance. When the input voltage is connected, as the special difference of VT1 and VT2, if the VT1 is conducted firstly, the transformer T1 would process the field excitation and the VT1 would be conducted rapidly. If T1 is in the magnetic saturation mode, the VT1 would change to be disconnected. So the T1 would generate the opposing electromotive force which would be through the transformer's feedback winding to make VT2's base electrode get the positive bias voltage, so that it would be conducted. This repeated actions would make the transformer T1 magnetic flux have the continuous oscillation. (View)
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Published:2011/8/23 23:40:00 Author:Robert | Keyword: Voltage, Regulated, Power, Chopper, Method
1. Chopper method.The picture shows the chopper method circuit. This is a non-isolated conversion method whose conversion efficiency is beyond 85%. This method contains the buck type, boost type, and polarity inversion type.The picture (a) shows the buck type circuit. When the transistor VT1 is conducted, the U1 would be through VT1 to add onto the choke L1 and capacitance C1, thus it would provides the load power. When the VT1 is disconnected, the energy stored in L1 would be through the freewheeling diode VD1 to supply the load.The picture (b) shows the boost type circuit. When the transistor VT1 is connected, the choke L1 would store energy. (View)
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Published:2011/8/23 23:40:00 Author:Robert | Keyword: DC, Voltage, Power, Regulator, Output
The picture shows the DC voltage regulator power circuit with output of 30V/0.2A. In the circuit it connects the zener diode VS2 to the upside, thus it could make the differencial amplifier VT1 and VT2's collector and base electrode be in low-voltage mode when their output voltage is high. At this time in order to make the VT1 and VT2 still have adequate working point, it could make the differencial amplifier emitter electrode resistance R5's value be bigger. The differencial amplifier's output port is lead out from the VT2's collector electrode. This would make the circuit keep the negative feedback and have the voltage regulation function. (View)
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Published:2011/8/23 23:40:00 Author:Robert | Keyword: Voltage, Regulator, Output
The picture shows the voltage regulator circuit with output of 34V/500mA. This circuit's maximum output voltage is determined by the operational amplifier A1's power voltage. When A1 uses the NJM5532 operational amplifier, its power voltage would be ±22V. So the maximum output voltage could be 44V. If there is some surplus capacity, the maximum output voltage could be about 40V. The VS3 is a zener diode. Its stable voltage could be selected to be about a half of the power voltage (18V). The R7, R8 and RP1 make up the voltage-divider circuit for the output voltage. And it selects the resistance value according to the principle that the divided voltage would be equal to the VS3's stable voltage. (View)
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Published:2011/8/23 23:40:00 Author:Robert | Keyword: DC, Regulator, Power, Short Circuit, Protection
The picture shows the DC regulator power with short circuit protection. The circuit uses the bistable circuit, which composed of VT7 and VT8, as the protection circuit. The R1 is the detecting resistance for the short circuit signal or over load signal. Its resistance value is very small. When it is working normally, there is low voltage drop on the R1, the VT8 is conducted and VT7 is disconnected, The VT3 is also disconnected. The protection circuit would not have action. When there is short circuit or overload, the R1's voltage would increase rapidly to make the VT8's base voltage increased to be disconnected. The VT8's collector voltage reduces and it would add onto the VT7's base electrode through the R15 and R16's voltage divider to make the VT7 conducted. So the VT7's collector voltage would increase to make the VD3 conducted. This would add the short circuit signal or overload signal to the VT3's base electrode to make its voltage increase to be disconnected. Thus it would protect the adjustment tube. (View)
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Published:2011/8/11 7:59:00 Author:Sue | Keyword: Power Supply
The picture shows CHANGHONG N2918 power supply circuit. (View)
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Published:2011/8/11 7:56:00 Author:Sue | Keyword: Power Supply
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Published:2011/8/11 5:50:00 Author:Sue | Keyword: Power Supply
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Published:2011/8/11 5:51:00 Author:Sue | Keyword: Power Supply
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Published:2011/8/11 5:49:00 Author:Sue | Keyword: Power Supply
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Published:2011/8/11 5:48:00 Author:Sue | Keyword: Power Supply
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Published:2011/8/23 22:23:00 Author:Seven | Keyword: DC-DC circuit, power supply, monitor pin
LM138/238/338--the adjustable 3-terminal stabilizer (forward output)This is a 3-terminal stabilizer with adjustable output voltage; its output voltage range is 1.2~32V; its maximum output current is 5A; its input stabilization typical value is 0.005%; its max input-output voltage difference is 35V; it contains the secure working area protection and overheat protection and current limitation circuit.
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Published:2011/8/23 22:23:00 Author:Seven | Keyword: DC-DC circuit, power supply, monitor pin
LM137/237/337--the adjustable 3-terminal stabilizer (output)
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Published:2011/8/11 3:41:00 Author:nelly | Keyword: LCD, switch power supply
AOC LM729 17in LCD switch power supply circuit is made as the core of control chip IC901(56*1), the circuit is shown in the figure.
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Published:2011/8/11 3:37:00 Author:nelly | Keyword: power supply adapter
Most LCDs adopt external power supply adapter, the different power supply adapters have different internal circuits. As shown in the figure, it is a typical power supply adapter circuit.
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Published:2011/8/11 11:08:00 Author:leo | Keyword: Constant current, power supply
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Published:2011/8/11 11:12:00 Author:leo | Keyword: Switch, constant current, power supply
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Published:2011/8/11 11:10:00 Author:leo | Keyword: Low drift, contant current, power supply
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Published:2011/8/6 22:01:00 Author:leo | Keyword: Switch power resource circuit, three-port PWM switch power supply IC
TOP2XX series IC is a kind of three ports switch power supply chip which integrates control circuit and power switch. Its package is TO-220 whose pin names and functions are shown in the picture (a).There are oscillator, PWM comparator, difference amplifier, logic circuit and MOSFET output switch tune and over voltage/over current protection circuit. Picture(b)is the classic applying circuit of TOP204. The features of this power resource are as the followings: Input current is 85 V to 265 V AC; output voltage is 15V±2%; output power is 30 W. (View)
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