CN101521462A - Switch power supply circuit - Google Patents
Switch power supply circuit Download PDFInfo
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- CN101521462A CN101521462A CN200810065469A CN200810065469A CN101521462A CN 101521462 A CN101521462 A CN 101521462A CN 200810065469 A CN200810065469 A CN 200810065469A CN 200810065469 A CN200810065469 A CN 200810065469A CN 101521462 A CN101521462 A CN 101521462A
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Abstract
The invention relates to a switch power supply circuit, which comprises a direct voltage input end, a transformer, a switch control circuit, a signal selecting circuit and a direct current/direct current converter chip. The direct voltage input end provides a direct voltage for the transformer which outputs a first direct voltage and a second direct voltage through the control of the switch control circuit; the signal selecting circuit reduces the voltage of the first direct voltage which is then compared with the second direct voltage; and the direct voltage with higher voltage is selected to be output to the direct current/direct current converter chip which is used for converting the direct voltage with higher voltage to a third direct voltage for output.
Description
Technical field
The present invention relates to a kind of switching power circuit.
Background technology
Switching power circuit has characteristics such as loss is little, conversion efficiency is high, linear change is little, working stability, therefore is widely used in display device and other consumption electronic products such as LCD TV, cathode-ray tube TV.
Seeing also Fig. 1, is a kind of schematic diagram of prior art switching power circuit.This switching power circuit 10 comprises one first current rectifying and wave filtering circuit 11, one first transformer 12, one second current rectifying and wave filtering circuit 13, one first dc voltage output end 136, one the 3rd current rectifying and wave filtering circuit 14, one second dc voltage output end 146, one first ON-OFF control circuit 15, one first feedback circuit 161, one second transformer 18, one the 4th current rectifying and wave filtering circuit 17, one the 3rd dc voltage output end 176, a second switch control circuit 19 and one second feedback circuit 162.
This first current rectifying and wave filtering circuit 11 comprises a full bridge rectifier 111, one first filter capacitor 112, two inputs 113,114 and outputs 115.These two inputs 113,114 are used for receiving external communication voltage.It is a direct current voltage that this full bridge rectifier 111 is used for this external communication voltage transitions.One end ground connection of this first filter capacitor 112, the other end is connected to this output 115.
This first transformer 12 is used for receiving this direct voltage and exports one first induced voltage and one second induced voltage, and it comprises one first elementary winding 121 and one first secondary winding 122.This first elementary winding 121 comprises a end and b end, and this a end is connected to the output 115 of this first current rectifying and wave filtering circuit 11, and this b end is via these first ON-OFF control circuit, 15 ground connection.This first secondary winding 122 comprises c end, d end and e end, and this c end is connected to this second current rectifying and wave filtering circuit 13, and this d end is connected to the 3rd current rectifying and wave filtering circuit 14, this e end ground connection.
This first ON-OFF control circuit 15 comprises one first pulse-width modulation chip 151, a first transistor 152 and one first resistance 154.This first pulse-width modulation chip 151 comprises one first voltage sample end 153 and one first control end 155.This first voltage sample end 153 is used for receiving feedback signals.This first control end 155 is used for one first pulse signal is offered the grid of this first transistor 152.The source electrode of this first transistor 152 is via these first resistance, 154 ground connection, and drain electrode is connected to the b end of this first elementary winding 121.This first transistor 152 is N channel enhancement mos field effect transistor.
This second current rectifying and wave filtering circuit 13 is used for exporting one first direct voltage, and it comprises one first inductance 131, one first storage capacitor 132, one second filter capacitor 135, one first rectifier diode 133 and one second rectifier diode 134.The anode of this first rectifier diode 133 and this second rectifier diode 134 all is connected to the c end of this first secondary winding 122, and the negative electrode of this first rectifier diode 133 and this second rectifier diode 134 all is connected to this first dc voltage output end 136.A connect end of this first storage capacitor 132 of one end of this first inductance 131, the other end of this first inductance 131 is connected to the c end of this first secondary winding 122, and the other end of this first storage capacitor 132 is connected to this first dc voltage output end 136.One end of this second filter capacitor 135 is connected to this first dc voltage output end 136, other end ground connection.
The 3rd current rectifying and wave filtering circuit 14 is used for exporting one second direct voltage, and it comprises one second inductance 141, one second storage capacitor 142, one the 3rd filter capacitor 145, one the 3rd rectifier diode 143 and one the 4th rectifier diode 144.The anode of the 3rd rectifier diode 143 and the 4th rectifier diode 144 all is connected to the d end of this first secondary winding 122, and the negative electrode of the 3rd rectifier diode 143 and the 4th rectifier diode 144 all is connected to this second dc voltage output end 146.A connect end of this second storage capacitor 132 of one end of this second inductance 141, the other end of this second inductance 141 is connected to the d end of this first secondary winding 122, and the other end of this second storage capacitor 142 is connected to this second dc voltage output end 146.One end of the 3rd filter capacitor 145 is connected to this second dc voltage output end 146, other end ground connection.
This first feedback circuit 161 is used for receiving this first direct voltage and this second direct voltage and the first corresponding feedback signal of generation, and this first feedback signal is fed back to the first voltage sample end 153 of this first pulse-width modulation chip 151.This first feedback circuit 161 comprises one first feedback input end 163, one second feedback input end 165 and one first feedback output end 167.This first feedback input end 163 is connected to this first dc voltage output end 136, this second feedback input end 165 is connected to this second dc voltage output end 146, and this first voltage output end 167 is connected to the first voltage sample end 153 of this first pulse-width modulation chip 151.
This second transformer 18 is used for receiving this direct voltage and exports one the 3rd induced voltage, and it comprises one second an elementary winding 181 and a second subprime winding 182.This second elementary winding 181 comprises o end and p end, and this o end is connected to the output 115 of this first current rectifying and wave filtering circuit 11, and this p end is via these second switch control circuit 19 ground connection.This second subprime winding 182 comprises r end and s end, and this r end is connected to the 4th current rectifying and wave filtering circuit 17, this s end ground connection.
This second switch control circuit 19 comprises one second pulse-width modulation chip 191, a transistor seconds 192 and one second resistance 194.This second pulse-width modulation chip 191 comprises one second voltage sample end 193 and one second control end 195.This second voltage sample end 193 is used for receiving feedback signals.This second control end 195 is used for one second pulse signal is offered the grid of this transistor seconds 192.The source electrode of this transistor seconds 192 is via these second resistance, 194 ground connection, and drain electrode is connected to the p end of this second elementary winding 181.This transistor seconds 192 is N channel enhancement mos field effect transistor.
The 4th current rectifying and wave filtering circuit 17 is used for exporting one the 3rd direct voltage, and it comprises one the 3rd inductance 171, one the 3rd storage capacitor 172, one the 4th filter capacitor 175, one the 5th rectifier diode 173 and one the 6th rectifier diode 174.The anode of the 5th rectifier diode 173 and the 6th rectifier diode 174 all is connected to the r end of this second subprime winding 182, and the negative electrode of the 5th rectifier diode 173 and the 6th rectifier diode 174 all is connected to the 3rd dc voltage output end 176.A connect end of the 3rd storage capacitor 172 of one end of the 3rd inductance 171, the other end of the 3rd inductance 171 is connected to the r end of this second subprime winding 182, and the other end of the 3rd storage capacitor 172 is connected to the 3rd dc voltage output end 176.One end of the 4th filter capacitor 175 is connected to the 3rd dc voltage output end 176, other end ground connection.
This second feedback circuit 162 is used for receiving the 3rd direct voltage and produces the second corresponding feedback signal, and this second feedback signal is fed back to the second voltage sample end 193 of this second pulse-width modulation chip 191.This second feedback circuit 162 comprises one the 3rd feedback input end 164 and one second feedback output end 166.The 3rd feedback input end 164 is connected to the 3rd dc voltage output end 176, and this second voltage output end 166 is connected to the second voltage sample end 193 of this second pulse-width modulation chip 191.
The operation principle of this switching power circuit 10 is as follows:
External communication voltage is input to two inputs 113,114 of this first current rectifying and wave filtering circuit 11, by being converted to a direct current voltage after these first current rectifying and wave filtering circuit, 11 rectifications, the filtering, and offer first elementary winding 121 of this first transformer 12 and the second elementary winding 181 of this second transformer 18.These first pulse signals of first control end 155 output of this first pulse-width modulation chip 151 are with the conducting of controlling this first transistor 152 or end, thereby control the operating state of this first transformer 12.These second pulse signals of second control end 195 output of this second pulse-width modulation chip 191 are with the conducting of controlling this transistor seconds 192 or end, thereby control the operating state of this second transformer 18.
When these the first transistor 152 conductings, this first filter capacitor 112, this first elementary winding 121, this first transistor 152 constitute a loop with this first resistance 154, and this first elementary winding 152 has the first conducting electric current to flow through.
When this first transistor 152 ended, this first conducting electric current diminished gradually owing to consume, thereby this first elementary winding 121 produces one first induced field.Under the effect of this first induced field, the c of this first secondary winding 122 end produces one first induced voltage, and the d end produces one second induced voltage.
This first induced voltage offers this second current rectifying and wave filtering circuit 13, by being converted to one first direct voltage after these second current rectifying and wave filtering circuit, 13 rectifications, the filtering.This second induced voltage offers the 3rd current rectifying and wave filtering circuit 14, by being converted to one second direct voltage after 14 rectifications of the 3rd current rectifying and wave filtering circuit, the filtering.On the one hand, this first direct voltage and this second direct voltage offer load circuit (figure does not show) via this first dc voltage output end 136 and this second dc voltage output end 146 respectively.On the other hand, this first direct voltage and this second direct voltage all are input to this first feedback circuit 161; This first feedback circuit 161 is exported the one first first voltage sample end that feeds back signal to this first pulse-width modulation chip 151 according to this first direct voltage and this second direct voltage; This first pulse-width modulation chip 151 is regulated this first pulse signal according to this first feedback signal, thereby regulates this first direct voltage and this second direct voltage.Wherein, the magnitude of voltage of this first direct voltage is 24V, and the magnitude of voltage of this second direct voltage is 12V.
In like manner, when these transistor seconds 192 conductings, this first filter capacitor 112, this second elementary winding 181, this transistor seconds 192 constitute a loop with this second resistance 194, and this second elementary winding 181 has the second conducting electric current to flow through.
When this transistor seconds 192 ended, this second conducting electric current diminished gradually owing to consume, thereby this second elementary winding 181 produces one second induced field.This second subprime winding 182 produces one the 3rd induced voltage under the effect of this second induced field.
The 3rd induced voltage offers the 4th current rectifying and wave filtering circuit 17, by being converted to one the 3rd direct voltage after 17 rectifications of the 4th current rectifying and wave filtering circuit, the filtering.On the one hand, the 3rd direct voltage offers load circuit (figure does not show) via the 3rd dc voltage output end 176.On the other hand, the 3rd direct voltage is input to this second feedback circuit 162.This second feedback circuit 162 is exported one second according to the 3rd direct voltage and is fed back signal to this second pulse-width modulation chip 191; This second pulse-width modulation chip 191 is regulated this second pulse signal according to this second feedback signal, thereby regulates the 3rd direct voltage.Wherein, the magnitude of voltage of the 3rd direct voltage is 5V.
From the above, this switching power circuit 10 is to control these two transformers 12,18 respectively by these two pulse-width modulation chips 151,191 to obtain this first direct voltage, this second direct voltage and the 3rd direct voltage.But these two pulse-width modulation chips 151,152 are chip of the same type, and both easily produce electromagnetic interference, thereby influence the job stability of this switching power circuit 10.In addition, the weight of these two transformers 12,18 is bigger, causes this switching power circuit 10 heavier.In addition, the cost of these two pulse-width modulation chips 151,152 is higher usually, causes the cost of this switching power circuit 10 higher.
Summary of the invention
The big and cost problem of higher of job insecurity, weight for solving the prior art switching power circuit is necessary to provide a kind of working stability, weight is less and lower-cost switching power circuit.
A kind of switching power circuit, it comprises a direct current voltage input end, a transformer, an ON-OFF control circuit, a signal selecting circuit and a DC-DC conversion chip.Wherein, this dc voltage input end provides a direct current voltage to this transformer.This transformer is exported one first direct voltage and one second direct voltage by the control of this ON-OFF control circuit.This signal selecting circuit carries out step-down to this first direct voltage, and with first direct voltage after the step-down and this second direct voltage relatively, selects that a higher direct voltage outputs to this DC/DC conversion chip among both.This DC/DC conversion chip be used for the direct voltage that this is higher be converted to one the 3rd direct voltage and output.
A kind of switching power circuit, it comprises a direct current voltage input end, a transformer, an ON-OFF control circuit, a signal selecting circuit and a DC-DC conversion chip.This signal selecting circuit comprises a reduction voltage circuit and a logical circuit.This dc voltage input end provides a direct current voltage to this transformer.This transformer is exported one first direct voltage to this reduction voltage circuit by the control of this ON-OFF control circuit, also exports one second direct voltage to this logical circuit.This reduction voltage circuit is used for this first direct voltage is carried out step-down, and it comprises a voltage stabilizing didoe, a transistor and a divider resistance.The negative electrode of this voltage stabilizing didoe receives this first direct voltage and is connected to this transistorized first conduction terminal, and anode is connected to this transistorized control end.One end of this divider resistance is connected to this transistorized control end, other end ground connection.First direct voltage behind this transistorized second conduction terminal output buck is to this logical circuit.This logical circuit is used for first direct voltage after the step-down and this second direct voltage relatively and export among both a higher direct voltage.This DC/DC conversion chip be used for the direct voltage that this is higher be converted to one the 3rd direct voltage and output.
Compared to prior art, this switching power circuit is to obtain this first direct voltage, this second direct voltage and the 3rd direct voltage by an ON-OFF control circuit, a signal selecting circuit and a DC-DC conversion chip.The chip that this DC/DC conversion chip and this ON-OFF control circuit comprise is dissimilar chip, and both electromagnetic interference are less, thereby can guarantee the job stability of this switching power circuit.In addition, this switching power circuit saves a transformer, alleviates the weight of this switching power circuit, thereby this switching power circuit is comparatively light.In addition, the cost of this signal selecting circuit and this DC converting circuit is lower, thereby the cost of this switching power circuit is lower.
Description of drawings
Fig. 1 is a kind of schematic diagram of prior art switching power circuit.
Fig. 2 is the electrical block diagram of switching power circuit one better embodiment of the present invention.
Embodiment
Seeing also Fig. 2, is the electrical block diagram of switching power circuit one better embodiment of the present invention.This switching power circuit 20 comprises one first current rectifying and wave filtering circuit 21, a transformer 22, one second rectifying and wave-filtering 23, one first dc voltage output end 236, one the 3rd current rectifying and wave filtering circuit 24, one second dc voltage output end 246, an ON-OFF control circuit 25, a feedback circuit 26, a signal selecting circuit 27, a DC-DC conversion chip 28 and one the 3rd dc voltage output end 283.This first dc voltage output end, 236 outputs, one first direct voltage, this first direct voltage can be 24V.This second dc voltage output end, 246 outputs, one second direct voltage, this second direct voltage can be 12V.The 3rd dc voltage output end 283 outputs one the 3rd direct voltage, the 3rd direct voltage can be 5V.
This first current rectifying and wave filtering circuit 21 comprises a full bridge rectifier 211, one first filter capacitor 212, two inputs 213,214 and outputs 215.These two inputs 213,214 are used for receiving external communication voltage.It is a direct current voltage that this full bridge rectifier 211 is used for this external communication voltage transitions.One end ground connection of this first filter capacitor 212, the other end is connected to this output 215.
This transformer 22 is used for receiving this direct voltage and exports one first induced voltage, and it comprises an elementary winding 221 and a level winding 222.This elementary winding 221 comprises a end and b end, and this a end is connected to the output 215 of this first current rectifying and wave filtering circuit 21, and this b end is via these ON-OFF control circuit 25 ground connection.This secondary winding 222 comprises c end, d end and e end, and this c end is connected to this second current rectifying and wave filtering circuit 23, and this d end is connected to the 3rd rectifying and wave-filtering 24 circuit, this e end ground connection.
This ON-OFF control circuit 25 comprises a pulse-width modulation chip 251, a first transistor 252 and a resistance 254.This pulse-width modulation chip 251 comprises a voltage sample end 253 and a control end 255.This voltage sample end 253 is used for receiving feedback signals.This control end 255 is used for a pulse signal is offered the grid of this first transistor 252.The source electrode of this first transistor 252 is via these resistance 254 ground connection, and drain electrode is connected to the b end of this elementary winding 221.This first transistor 252 is N channel enhancement mos field effect transistor.
This second current rectifying and wave filtering circuit 23 is used for exporting one first direct voltage, and it comprises one first inductance 231, one first storage capacitor 232, one second filter capacitor 235, one first rectifier diode 233 and one second rectifier diode 234.The anode of this first rectifier diode 233 and this second rectifier diode 234 all is connected to the c end of this first secondary winding 222, and the negative electrode of this first rectifier diode 233 and this second rectifier diode 234 all is connected to this first dc voltage output end 236.A connect end of this first storage capacitor 232 of one end of this first inductance 231, the other end of this first inductance 231 is connected to the c end of this first secondary winding 222, and the other end of this first storage capacitor 232 is connected to this first dc voltage output end 236.One end of this second filter capacitor 235 is connected to this first dc voltage output end 236, other end ground connection.
The 3rd current rectifying and wave filtering circuit 24 is used for exporting one second direct voltage, and it comprises one second inductance 241, one second storage capacitor 242, one the 3rd filter capacitor 245, one the 3rd rectifier diode 243 and one the 4th rectifier diode 244.The anode of the 3rd rectifier diode 243 and the 4th rectifier diode 244 all is connected to the d end of this first secondary winding 222, and the negative electrode of the 3rd rectifier diode 243 and the 4th rectifier diode 244 all is connected to this second dc voltage output end 246.A connect end of this second storage capacitor 242 of one end of this second inductance 241, the other end of this second inductance 241 is connected to the d end of this first secondary winding 222, and the other end of this second storage capacitor 242 is connected to this second dc voltage output end 246.One end of the 3rd filter capacitor 245 is connected to this second dc voltage output end 246, other end ground connection.
This feedback circuit 26 is used for receiving this first direct voltage and this second direct voltage and the corresponding feedback signal of generation, and this feedback signal is fed back to the voltage sample end 253 of this pulse-width modulation chip 251.This feedback circuit 26 comprises one first feedback input end 261, one second feedback input end 262 and a feedback output end 263.This first feedback input end 261 is connected to this first dc voltage output end 236, and this second feedback input end 262 is connected to this second dc voltage output end 246, and this feedback output end 263 is connected to the voltage sample end 253 of this pulse-width modulation chip 251.
This signal selecting circuit 27 is used for first direct voltage is carried out step-down, and first direct voltage after the step-down and this second direct voltage are compared selection, one of them direct voltage is offered this DC/DC conversion chip 28 again.This signal selecting circuit 27 comprises one first signal input part 275, a secondary signal input 276, a signal output part 277, a reduction voltage circuit 291 and a logical circuit 292.This reduction voltage circuit 291 comprises a voltage stabilizing didoe 271, a divider resistance 278, a protective resistance 279 and a transistor seconds 272.This logical circuit 292 comprises one first diode 273 and one second diode 274.This first signal input part 275 is connected to first dc voltage output end 236, and this secondary signal input 276 is connected to second dc voltage output end 246.The negative electrode of this voltage stabilizing didoe 271 is connected to this first signal input part 275, and the anode of this voltage stabilizing didoe 271 is via these divider resistance 278 ground connection.This transistor seconds 272 is npn type bipolar transistors, and its collector electrode is connected to this first signal input part 275, and base stage is connected to the anode of this voltage stabilizing didoe 271 via this protective resistance 279, and emitter is connected to the anode of this first diode 273.The negative electrode of this first diode 273 is connected to this signal output part 277.The anode of this second diode 274 is connected to this secondary signal input 276, and negative electrode is connected to this signal output part 277.Wherein, the resistance of this protective resistance 279 is much smaller than the resistance of this divider resistance 278.The base stage of this transistor seconds 272 and the conducting voltage between emitter are 0.7V.The conducting voltage of this voltage stabilizing didoe 271 is the poor of this first direct voltage and this second direct voltage, and when this first direct voltage is 12V, when this second direct voltage was 12V, this conducting voltage was 12V.
This DC/DC conversion chip 28 is used for a direct voltage from these signal selecting circuit 27 outputs is carried out linear voltage decreasing, exports one the 3rd direct voltage.This DC/DC conversion chip 28 comprises one the 3rd signal input part 281 and a secondary signal output 282.The 3rd signal input part 281 is connected to first signal output part 277 of this signal selecting circuit 27.This secondary signal output 282 is connected to the 3rd dc voltage output end 283, the three dc voltage output ends 283 the 3rd direct voltage is offered load circuit.This DC/DC conversion chip can be a series of chips that the 12V direct voltage can be converted to the 5V direct voltage such as AP1501 chip, AP1506 chip, AP1511 chip and LM7805 chip.
The operation principle of this switching power circuit 20 is as follows:
External communication voltage is input to two inputs 213,214 of this first current rectifying and wave filtering circuit 21, by being converted to a direct current voltage after these first current rectifying and wave filtering circuit, 21 rectifications, the filtering, and offers the elementary winding of this transformer 22.These pulse signals of control end 255 output of this pulse-width modulation chip 251 are with the conducting of controlling this first transistor 252 or end, thereby control the operating state of this transformer 22.
When these the first transistor 252 conductings, this first filter capacitor 212, this elementary winding 221, this first transistor 252 constitute a loop with this resistance 254, and this elementary winding 221 has the conducting electric current to flow through.
When this first transistor 252 ended, the conducting electric current of this elementary winding 221 diminished gradually owing to consume, thereby this elementary winding 221 produces an induced field.Under the effect of this induced field, the c of this secondary winding 222 end produces one first induced voltage, and the d end produces one second induced voltage.
This first induced voltage offers this second current rectifying and wave filtering circuit 23, by being converted to one first direct voltage after these second current rectifying and wave filtering circuit, 23 rectifications, the filtering.This second induced voltage offers the 3rd current rectifying and wave filtering circuit 24, by being converted to one second direct voltage after 24 rectifications of the 3rd current rectifying and wave filtering circuit, the filtering.On the one hand, this first direct voltage and this second direct voltage offer load circuit (figure does not show) via this first dc voltage output end 236 and this second dc voltage output end 246 respectively.On the other hand, this first direct voltage and this second direct voltage all are input to this feedback circuit 26; This feedback circuit 26 feeds back signal to the voltage sample end 253 of this pulse-width modulation chip 251 according to this first direct voltage and this second direct voltage output one; This pulse-width modulation chip 251 is regulated this pulse signal according to this feedback signal, thereby regulates this first direct voltage and this second direct voltage.
This first direct voltage and this second direct voltage also offer this signal selecting circuit 27 via this first signal input part 275 and this secondary signal input 276 respectively.If this first direct voltage is V1, this second direct voltage is V2, and the conducting voltage of this voltage stabilizing didoe 271 is Vd, and the base stage of this transistor seconds 272 and the conducting voltage between emitter are Vbe.This second filter capacitor 235, two utmost point pipes 271 of this voltage stabilizing and this divider resistance 278 constitute a loop, so the voltage at these divider resistance 278 two ends is V1-Vd., establish it and be V1 ' again via being approximately V1-Vd-Ve behind this transistor seconds 272 via first direct voltage of these voltage stabilizing didoe 271 step-downs.As V1 '〉during V2, these first diode, 273 conductings, V1 ' is input to this DC converting circuit 28 and is converted to one the 3rd direct voltage by these DC converting circuit 28 step-downs and offers load circuit.When V1 '＜V2, these second diode, 274 conductings, V2 is input to this DC converting circuit 28 and by after these DC converting circuit 28 step-downs one the 3rd direct voltage being offered load circuit.
Compared to prior art, this switching power circuit 20 is to obtain this first direct voltage, this second direct voltage and the 3rd direct voltage by a pulse-width modulation chip 251, a signal selecting circuit 27 and a DC-DC conversion chip 28.This pulse-width modulation chip 251 is dissimilar chips with this DC/DC conversion chip 28, and this pulse-width modulation chip 251 is less with the electromagnetic interference of this DC/DC conversion chip 28, thereby can guarantee the job stability of this switching power circuit 20.
In addition, this switching power circuit 20 saves a transformer 22, alleviates the weight of this switching power circuit 20, thereby this switching power circuit 20 is comparatively light.
In addition, the cost of the circuit of this signal selecting circuit 27 and this DC/DC conversion chip is low than the cost of the second pulse-width modulation chip of prior art switching power circuit 10, save second feedback circuit of prior art switching power circuit 10 simultaneously, thereby the cost of this switching power circuit 20 is lower.
In actual applications, because the influence of the load that is inserted or the influence of input voltage, this first direct voltage V1 and this second direct voltage V2 have-10%～+ 10% voltage drift.In addition, the power output of this transformer 22 is a certain value, and its output voltage hour easily causes the circuit heavy duty.This signal selecting circuit 27 with this first direct voltage via this voltage stabilizing didoe 271 and transistor seconds 272 step-downs after, compare with this second direct voltage by this first diode 273 and this second diode 274 again, the direct voltage of exporting a tool high voltage can avoid this first direct voltage V1 or this second direct voltage V2 voltage to float low and circuit heavy duty problem that cause to this DC converting circuit 28.
It is described that switching power circuit of the present invention is not limited to above-mentioned execution mode, as: in the switching power circuit 20, the transistor seconds 273 of this signal selecting circuit 27 also can be a field-effect transistor.
Claims (10)
1. switching power circuit, it comprises a direct current voltage input end, one transformer, one ON-OFF control circuit, one signal selecting circuit and a DC-DC conversion chip, it is characterized in that: this dc voltage input end provides a direct current voltage to this transformer, this transformer is exported one first direct voltage and one second direct voltage by the control of this ON-OFF control circuit, this signal selecting circuit carries out step-down to this first direct voltage, and first direct voltage after the step-down and this second direct voltage are compared, select that a higher direct voltage outputs to this DC/DC conversion chip among both, this DC/DC conversion chip is used for the direct voltage that this is higher and is converted to one the 3rd direct voltage and output.
2. switching power circuit as claimed in claim 1, it is characterized in that: this signal selecting circuit comprises a reduction voltage circuit and a logical circuit, this reduction voltage circuit is used for this first direct voltage is carried out step-down, this logical circuit is used for first direct voltage after this step-down and this second direct voltage are compared, export these both in a higher direct voltage.
3. switching power circuit as claimed in claim 2, it is characterized in that: this reduction voltage circuit comprises a voltage stabilizing didoe, one transistor and a divider resistance, this logical circuit comprises one first diode and one second diode, the negative electrode of this voltage stabilizing didoe receives this first direct voltage and is connected to this transistorized first conduction terminal, the anode of this voltage stabilizing didoe is connected to this transistorized control end, the conducting voltage of this voltage stabilizing didoe is the poor of this first direct voltage and this second direct voltage, one end of this divider resistance is connected to this transistorized control end, the other end ground connection of this divider resistance, the anode of this first diode is connected to this transistorized second conduction terminal, the anode of this second diode receives this second direct voltage, and the negative electrode of this first diode and this second diode all is connected to this DC/DC conversion chip.
4. switching power circuit as claimed in claim 3; it is characterized in that: this signal selecting circuit further comprises a protective resistance; one end of this protective resistance is connected to this transistorized control end, and the other end of this protective resistance is connected to the anode of this voltage stabilizing didoe.
5. switching power circuit as claimed in claim 3 is characterized in that: this transistor is a bipolar transistor, and its collector electrode is this transistorized first conduction terminal, and base stage is this transistorized control end, and emitter is this transistorized second conduction terminal.
6. switching power circuit as claimed in claim 3 is characterized in that: this transistor is a field-effect transistor, and its source electrode is this transistorized first conduction terminal, and grid is this transistorized control end, and drain electrode is this transistorized second conduction terminal.
7. switching power circuit as claimed in claim 1, it is characterized in that: this switching power circuit further comprises one first current rectifying and wave filtering circuit, one second current rectifying and wave filtering circuit and one the 3rd current rectifying and wave filtering circuit, this first current rectifying and wave filtering circuit is used for the external communication voltage transitions is this direct voltage, and offer this dc voltage input end, this transformer comprises an elementary winding and a level winding, this elementary winding comprises one first end and one second end, this first end is connected to the output of this first current rectifying and wave filtering circuit, this second end is via this ON-OFF control circuit ground connection, this secondary winding comprises one the 3rd end, one the 4th end and a five terminal, the 3rd end is exported this first direct voltage via this second current rectifying and wave filtering circuit, the 4th end is exported this second direct voltage, this five terminal ground connection via the 3rd current rectifying and wave filtering circuit.
8. switching power circuit as claimed in claim 7, it is characterized in that: this switching power circuit also comprises a feedback circuit, this ON-OFF control circuit comprises a pulse-width modulation chip and a transistor seconds, this pulse-width modulation chip comprises that a voltage sample end and is used for the control end of output pulse signal, this transistor seconds is a field-effect transistor, its grid is connected to the control end of this pulse-width modulation chip, source electrode is via a grounding through resistance, drain electrode is connected to second end of this elementary winding, this feedback circuit receives this first direct voltage and this second direct voltage and exports a voltage sample end that feeds back signal to this pulse-width modulation chip, and this pulse-width modulation chip is adjusted the pulse signal of this control end output according to this feedback signal.
9. switching power circuit as claimed in claim 1, it is characterized in that: this first direct voltage is 24V, this second direct voltage is 12V, the conducting voltage of this voltage stabilizing didoe is 12V, and this DC/DC conversion chip is used for the direct voltage step-down of a 12V is converted to the 3rd direct voltage of a 5V.
10. switching power circuit, it comprises a direct current voltage input end, one transformer, one ON-OFF control circuit, one signal selecting circuit and a DC-DC conversion chip, it is characterized in that: this signal selecting circuit comprises a reduction voltage circuit and a logical circuit, this dc voltage input end provides a direct current voltage to this transformer, this transformer is exported one first direct voltage to this reduction voltage circuit by the control of this ON-OFF control circuit, also export one second direct voltage to this logical circuit, this reduction voltage circuit is used for this first direct voltage is carried out step-down, this reduction voltage circuit comprises a voltage stabilizing didoe, one transistor and a divider resistance, the negative electrode of this voltage stabilizing didoe receives this first direct voltage and is connected to this transistorized first conduction terminal, the anode of this voltage stabilizing didoe is connected to this transistorized control end, one end of this divider resistance is connected to this transistorized control end, the other end ground connection of this divider resistance, first direct voltage behind this transistorized second conduction terminal output buck is to this logical circuit, this logical circuit is used for first direct voltage after the step-down and this second direct voltage relatively and export among both a higher direct voltage, and this DC/DC conversion chip is used for the direct voltage that this is higher and is converted to one the 3rd direct voltage and output.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2008100654698A CN101521462B (en) | 2008-02-29 | 2008-02-29 | Switch power supply circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2008100654698A CN101521462B (en) | 2008-02-29 | 2008-02-29 | Switch power supply circuit |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN101521462A true CN101521462A (en) | 2009-09-02 |
| CN101521462B CN101521462B (en) | 2011-06-29 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN2008100654698A Expired - Fee Related CN101521462B (en) | 2008-02-29 | 2008-02-29 | Switch power supply circuit |
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| Country | Link |
|---|---|
| CN (1) | CN101521462B (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102611311A (en) * | 2011-01-20 | 2012-07-25 | 国琏电子（上海）有限公司 | Flyback type power supply system |
| CN103124451A (en) * | 2011-11-18 | 2013-05-29 | 海洋王照明科技股份有限公司 | LED driving circuit and LED taxiway edge light |
| CN111193400A (en) * | 2018-11-14 | 2020-05-22 | 矢崎总业株式会社 | Power supply device |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS61102167A (en) * | 1984-10-23 | 1986-05-20 | Yokogawa Hokushin Electric Corp | Dc/dc converter |
| CN2805207Y (en) * | 2005-06-17 | 2006-08-09 | 天水华天微电子有限公司 | High temp. isolation electric power module |
-
2008
- 2008-02-29 CN CN2008100654698A patent/CN101521462B/en not_active Expired - Fee Related
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102611311A (en) * | 2011-01-20 | 2012-07-25 | 国琏电子（上海）有限公司 | Flyback type power supply system |
| CN103124451A (en) * | 2011-11-18 | 2013-05-29 | 海洋王照明科技股份有限公司 | LED driving circuit and LED taxiway edge light |
| CN103124451B (en) * | 2011-11-18 | 2015-05-13 | 海洋王照明科技股份有限公司 | LED driving circuit and LED taxiway edge light |
| CN111193400A (en) * | 2018-11-14 | 2020-05-22 | 矢崎总业株式会社 | Power supply device |
| CN111193400B (en) * | 2018-11-14 | 2023-08-22 | 矢崎总业株式会社 | Power supply device |
Also Published As
| Publication number | Publication date |
|---|---|
| CN101521462B (en) | 2011-06-29 |
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