Multi-channel DC voltage stabilization output circuit
Technical field
The present invention relates to a kind of multi-channel DC voltage stabilization output circuit.
Background technology
At present, multi-channel DC voltage stabilization output circuit has been widely used in the various electronic products such as LCD, computer motherboard, notebook computer as driving power.For example, general LCD all adopts five tunnel DC voltage-stabilizing output circuit as driving power.
Seeing also Fig. 1, is a kind of multi-channel DC voltage stabilization output circuit of prior art.This multi-channel DC voltage stabilization output circuit 1 comprises a transformer 11, a main power control chip 12, a feedback circuit 10, a first via output 14, one the second road output 13, one first half-wave rectifying circuit 15, one second half-wave rectifying circuit 16, one first filter circuit 17 and one second filter circuit 18.
This transformer 11 provides voltage by this first half-wave rectifying circuit 15 and this first filter circuit 17 for this first via output 14, and provides voltage by this second half-wave rectifying circuit 16 and this second filter circuit 18 for this second road output 13.This first via output 14 is used to export low pressure.This second road output 13 is used to export high pressure.This feedback circuit 10 is used for the variation of the mixed signal of this first via output 14 and the second road output 13 is fed back to this main power control chip 12.This main power control chip 12 is adjusted and is exported the pulse duration of this transformer 11 to by the mixed signal of these feedback circuit 10 feedbacks, thereby adjusts this transformer 11 outputs.
This feedback circuit 10 comprises an optical coupler (Optical Coupler) 140, one adjustable accurate shunt regulator (Adjustable Precision Shunt Regulator) 150,1 first resistance 110, one second resistance 120 and one the 3rd resistance 130.
This optical coupler 140 comprises photosensitive three polar bodys 145 and a light-emitting diode 141.The base stage of these photosensitive three polar bodys 145 (not indicating) suspension joint (Floating), emitter-base bandgap grading (not indicating) is connected to this main power control chip 12, and the collection utmost point (not indicating) is connected to a power supply (not indicating) through a current-limiting resistance (not indicating).The anode of this light-emitting diode 141 is connected between this second half-wave rectifying circuit 16 and this second filter circuit 18 through this first resistance 110, and negative electrode is connected to the negative electrode of this adjustable accurate shunt regulator 150.When these light-emitting diode 141 conductings, its emission light is to the surface of these photosensitive three polar bodys 145, and these photosensitive three polar bodys 145 are accepted conducting behind the light, and produce electric current, and the size of this electric current is directly proportional with the size of the electric current that flows through this light-emitting diode 141.
Anode 153 ground connection of this adjustable accurate shunt regulator 150 are connected to this second road output 13 and first via output 14 through this second resistance 120 and the 3rd resistance 130 respectively with reference to the utmost point 151.
During LCD incoming transport power supply that this multi-channel DC voltage stabilization output circuit 1 is used, this LCD is in holding state, this moment, this first via output 14 was with underloads, these the second road output, 13 bands are unloaded, the voltage of this first via output 14 can be reduced moment, the voltage of this second road output 13 is constant, cause the reference utmost point 151 voltages of the adjustable accurate shunt regulator 150 of this feedback circuit 10 to reduce, the conducting electric current of this adjustable accurate shunt regulator 150 is reduced, the electric current that flows through this light-emitting diode 141 is reduced, thereby the electric current that makes these photosensitive three polar bodys 145 export this main power control chip 12 to reduces, and then make this main power control chip 12 increase the pulse duty factor (Duty Ratio) that exports this transformer 11 to, cause the voltage of this second road output 13 and this first via output 14 to increase.
For this first via output 14, because its voltage reduces before, thereby its voltage increases and can accept now.Yet, for this second road output 13, because its voltage does not become before, thereby its voltage increase now can cause its voltage to raise, thereby the assembly that receives these the second road output, 13 voltages is caused harmful effect, thereby the reliability of this multi-channel DC voltage stabilization output circuit 1 is lower.
Summary of the invention
In order to solve the lower problem of prior art multi-channel DC voltage stabilization output circuit reliability, be necessary the multi-channel DC voltage stabilization output circuit that provides a kind of reliability higher.
A kind of multi-channel DC voltage stabilization output circuit, it comprises a high-pressure side, a first via output, a transformer, one first half-wave rectifying circuit, one first filter circuit, one second half-wave rectifying circuit, one second filter circuit, a main power control chip, a feedback circuit and a control circuit.This transformer provides voltage by this second half-wave rectifying circuit and this second filter circuit for this high-pressure side for this first via output provides voltage, this transformer by this first half-wave rectifying circuit and this first filter circuit.This first via output is used to export low pressure.This feedback circuit is used for the variation of the mixed signal of this high-pressure side and this first via output is fed back to this main power control chip.This main power control chip is adjusted the pulse duration that exports this transformer pulse to by the mixed signal of this feedback circuit feedback.This control circuit is used for the voltage of high-pressure side input is controlled, and export normal high pressure, it comprises one first resistance, one second resistance, one the 3rd resistance, one the second road output, a diode, a RC parallel circuits, one first an adjustable accurate shunt regulator and a n channel metal oxide semiconductor field effect transistor.This second road output is used to export high pressure.The reference utmost point of this first adjustable accurate shunt regulator is connected to this second road output through this second resistance, also passes through the 3rd grounding through resistance, and negative electrode is connected to this transformer, plus earth through this first resistance, the negative electrode of this diode, anode in regular turn.One end of this RC parallel circuits is connected between this diode and this first resistance, other end ground connection.The grid of this n channel metal oxide semiconductor field effect transistor is connected to the negative electrode of this first adjustable accurate shunt regulator, and source electrode is connected to this second road output, and drain electrode is connected to this high-pressure side.
Compared to prior art, this multi-channel DC voltage stabilization output circuit further comprises this control circuit, and when the voltage of this high-pressure side and this second road output raise, the transistorized internal resistance meeting of this control circuit increased, thereby reduces the voltage of this second road output.Thereby the reliability of this multi-channel DC voltage stabilization output circuit is higher.
Description of drawings
Fig. 1 is a kind of circuit diagram of prior art multi-channel DC voltage stabilization output circuit.
Fig. 2 is the circuit diagram of multi-channel DC voltage stabilization output circuit one better embodiment of the present invention.
Embodiment
Seeing also Fig. 2, is the circuit diagram of multi-channel DC voltage stabilization output circuit one better embodiment of the present invention.Only be output as example with two the tunnel among the figure, the principle of other multichannel output is identical therewith, thereby no longer further gives an example.
This multi-channel DC voltage stabilization output circuit 2 comprises a transformer 21, a main power control chip 22, a control circuit 26, a feedback circuit 20, a high-pressure side 23, a first via output 24, one first half-wave rectifying circuit 25, one second half-wave rectifying circuit 27, one first filter circuit 28 and one second filter circuit 29.
This transformer 21 provides voltage by this first half-wave rectifying circuit 25 and this first filter circuit 28 for this first via output 24, and provides voltage by this second half-wave rectifying circuit 27 and this second filter circuit 29 for this high-pressure side 23.This first via output 24 is used to export low pressure.This high-pressure side 23 is used for input voltage to this control circuit 26.This control circuit 26 is used to adjust its internal resistance, thereby the voltage of high-pressure side 23 inputs is controlled, and exports normal high pressure.This feedback circuit 20 is used for the variation of the mixed signal of this high-pressure side 23 and this first via output 24 is fed back to this main power control chip 22.This main power control chip 22 is adjusted and is exported the pulse duration of this transformer 21 to, thereby adjust the output of this transformer 21 by the mixed signal of these feedback circuit 20 feedbacks.
This control circuit 26 comprises a rectifier diode 261, a RC parallel circuits 262, one first adjustable accurate shunt regulator 270, a transistor 280, one the second road output 266, one first resistance 263, one second resistance 264 and one the 3rd resistance 265.This rectifier diode 261 is used for the voltage of transformer 21 outputs is carried out halfwave rectifier.This RC parallel circuits 262 is used for the voltage of this transformer 21 outputs is carried out smothing filtering.This second road output 266 is used to export high pressure.
This first adjustable accurate shunt regulator 270 can be TL431, and it comprises one with reference to the utmost point 271, a negative electrode 272 and an anode 273.Negative electrode (not label), anode (not label) that this negative electrode 272 passes through this first resistance 263, this rectifier diode 261 in regular turn are connected to this transformer 21, these anode 273 ground connection, this is connected to this second road output 266 with reference to the utmost point 271 through this second resistance 264, also passes through the 3rd resistance 265 ground connection.
This transistor 280 is a N channel enhancement mos field effect transistor (N-Channel Enhancement Mode Metal-Oxide-SemiconductorField-Effect Transistor, N-MOSFET), its grid 281 is connected to the negative electrode 272 of this first adjustable accurate shunt regulator 270, source electrode 282 is connected to this second road output 266, and drain electrode 283 is connected to this high-pressure side 23.
One end of this RC parallel circuits 262 is connected between this rectifier diode 261 and this first resistance 263, other end ground connection.This rectifier diode 261 can be germanium diode, silicon diode or gallium arsenide diode.
This feedback circuit 20 comprises an optical coupler 240, one second adjustable accurate shunt regulator 250, one the 4th resistance 210, one the 5th resistance 220 and one the 6th resistance 230.
This optical coupler 240 comprises photosensitive three polar bodys 245 and a light-emitting diode 241.The base stage of these photosensitive three polar bodys 245 (not indicating) suspension joint, emitter-base bandgap grading (not indicating) is connected to this main power control chip 22, and the collection utmost point (not indicating) is connected to a power supply (not indicating) through a current-limiting resistance (not indicating).The anode of this light-emitting diode 241 is connected between this second half-wave rectifying circuit 27 and this second filter circuit 29 through the 4th resistance 210, and negative electrode is connected to the negative electrode 252 of this second adjustable accurate shunt regulator 250.When these light-emitting diode 241 conductings, its emission light is to the surface of these photosensitive three polar bodys 245, and these photosensitive three polar bodys 245 are accepted conducting behind the light, and produce electric current, and the size of this electric current is directly proportional with the size of the electric current that flows through this light-emitting diode 241.
This second adjustable accurate shunt regulator 250 can be TL431, and its anode 253 ground connection are connected to this high-pressure side 23 and first via output 24 through the 5th resistance 220 and the 6th resistance 230 respectively with reference to the utmost point 251.
During LCD incoming transport power supply that this multi-channel DC voltage stabilization output circuit 2 is used, this LCD is in holding state, this moment, this first via output 24 was with underloads, these the second road output, 266 bands are unloaded, the voltage of this first via output 24 can be reduced moment, and the voltage of this second road output 266 is constant.In this multi-channel DC voltage stabilization output circuit 2, the number of turn of the secondary coil by adjusting this transformer 21 (figure does not show), the grid 281 that can make this transistor 280 and the voltage difference of source electrode 282 be greater than cut-in voltage, thereby make this transistor 280 keep conducting states.Thereby, the voltage of this high-pressure side 23 is also constant, cause the reference utmost point 251 voltages of the adjustable accurate shunt regulator 250 of this feedback circuit 20 to reduce, the conducting electric current of this adjustable accurate shunt regulator 250 is reduced, the electric current that flows through this light-emitting diode 241 is reduced, thereby the electric current that makes these photosensitive three polar bodys 245 export this main power control chip 22 to reduces, and then make this main power control chip 22 increase the pulse duty factor that exports this transformer 21 to, the voltage of this high-pressure side 23 and this first via output 24 is increased.Because this transistor 280 keeps conducting states, thereby the voltage of this second road output 266 also increases, thereby causes its voltage to raise.
The voltage of this second road output 266 raises, and the reference utmost point 271 voltages of the first adjustable accurate shunt regulator 270 of this control circuit 26 are increased, thereby the conducting electric current of this first adjustable accurate shunt regulator 270 is increased.Because this conducting electric current is also for flowing through the electric current of this first resistance 263, thereby the voltage of the grid 281 of this transistor 280 reduces, the grid 281 of this transistor 280 and the voltage difference of source electrode 282 reduce, the conducting channel of this transistor 280 is narrowed down, internal resistance increases, thereby the voltage of this second road output 266 is reduced.
Compared to prior art, this multi-channel DC voltage stabilization output circuit 2 further comprises this control circuit 26, when the voltage of this high-pressure side 23 and this second road output 266 raise, the internal resistance meeting of the transistor 280 of this control circuit 26 increased, thereby reduced the voltage of this second road output 266.Thereby the reliability of this multi-channel DC voltage stabilization output circuit 2 is higher.
It is described that multi-channel DC voltage stabilization output circuit 2 of the present invention is not limited to above execution mode, can further comprise a Third Road output, one the four road output and one the five road output as this multi-channel DC voltage stabilization output circuit 2, the output end voltage that 26 pairs of voltages of this control circuit raise is controlled; The transistor 280 of this control circuit 26 can be N channel depletion type mos field effect transistor.