CN105375798A - Self-adaptive sampling circuit, primary side feedback constant voltage system and switching power supply system - Google Patents
Self-adaptive sampling circuit, primary side feedback constant voltage system and switching power supply system Download PDFInfo
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Abstract
The invention discloses a self-adaptive sampling circuit and a primary side feedback constant voltage system using the circuit. The circuit comprises a peak reference voltage generation module, an operation module, a ramp voltage generation module, a comparison module and a pulse generation module. The peak reference voltage generation module is used for generating current peak reference voltage. The operation module is used for performing scale operation on current peak reference voltage and outputting sampling reference voltage. The ramp voltage generation module is used for generating ramp voltage. The comparison module is used for comparing sampling reference voltage and ramp voltage. When ramp voltage is greater than sampling reference voltage, a high-level sampling identification signal is outputted, or a low-level sampling identification signal is outputted. The pulse generation module is used for receiving the sampling identification signal and generating a narrow pulse signal at the rising edge of the sampling identification signal so that sampling time of a switching power supply system using the self-adaptive sampling circuit is enabled to automatically change along with change of the current peak.
Description
Technical field
The present invention relates to electronic applications, particularly relate to adaptively sampled circuit, former limit feedback constant pressing system and switch power supply system.
Background technology
Fig. 1 is a kind of conventional former limit feedback constant pressing system.As shown in the figure, D1 ~ D4 is rectifier bridge, and C1 is input end capacitor, and alternating voltage is filtered into direct voltage (Vbus) after rectifier bridge and electric capacity C1; Rst is starting resistance, and one end is electrically connected to Vbus, and the other end is electrically connected to chip pin VCC; C2 is the electric capacity of the pin VCC being connected to chip IC 1; During startup, the electric current that resistance Rst flows through charges to electric capacity C2, and when the voltage of the pin VCC of chip IC 1 reaches the threshold voltage of chip setting, chip enable, exports a switching signal to drive field effect transistor Q1; IC1 is control chip, Q1 is power switch pipe, T1 is transformer, Rcs is former limit winding current sampling resistor, the electric current that former limit winding flows through flows through starting resistance Rcs, one end of starting resistance Rcs is electrically connected to the CS pin of chip IC 1, other end ground connection, and the voltage proportional of the CS pin of chip IC 1 is in former limit winding current; First resistance R1 and the second resistance R2 is the divider resistance of auxiliary winding voltage, and FB is the feedback pin of chip IC 1, in order to indirectly to reflect output voltage; 5th diode D5, the 4th resistance R4 and the 4th electric capacity C4 are former limit RCD absorbing circuits; 6th diode D6 is auxiliary limit diode, and the 7th diode D7 is secondary side diode, and the 3rd electric capacity C3 is output capacitance.
According to Fig. 1, although the electrical potential energy of feedback pin FB reflects output voltage indirectly, but because this current potential shows as pulse voltage, the FB waveform of discontinuous mode as shown in Figure 2, wherein GATE is the waveform of the GATE pin of chip IC 1, FB is the waveform of the FB pin of chip IC 1, and ip is transformer primary side winding current waveform, and is is transformer secondary winding current waveform.To sum up, FB just reflects output voltage within the demagnetization time (Tdemag) of one-period, so need the voltage signal that sometime gather FB pin on of sample circuit within the demagnetization time.
The constant voltage sample circuit of feedback constant pressing system control chip inside, existing former limit adopts the set time to sample mostly, and timing from former limit power switch pipe turns off, samples to feedback voltage (FB) after the set time.Although realize set time sample circuit than being easier to, but set time sample circuit has certain shortcoming: former limit feedback constant pressing system is in order to realize low noise and no-load power consumption little as far as possible, when different loads, primary current peak value is set to difference by chip internal usually.When heavier loads, primary current peak value is higher; When load is lighter, primary current peak value is lower.As shown in Figure 3: the constant-voltage system that former limit is fed back, be usually operated at discontinuous mode, for different primary current peak values (Ipp), secondary current peak value is equal proportion change (Isp) also, follow following equation: Isp=Nps*Ipp, wherein, Nps is the former secondary turn ratio.If use set time (Tsh) sampling, for different primary current peak value, the electric current that sample point secondary side diode flows through (i.e. secondary current is) is different, causes the pressure drop (V in sample point secondary side diode
d) different, be Δ V
ddifference, this Δ V
dvoltage differences can add on the output voltage, Vo=Vs-V
d, wherein, Vs is transformer secondary voltage (by feedback control loop, Vs keeps constant), and Vo is output voltage, during different loads, and V
dvariant, so output voltage also can be variant, and then export constant voltage precision and will inevitably reduce, especially for the lower system of output voltage, this difference can affect larger.
Therefore, the former limit feedback constant pressing system a kind of new adaptively sampled circuit being provided and adopting this circuit is needed badly, to solve the problem.
Summary of the invention
In order to solve the problem, a kind of adaptively sampled circuit is provided and adopts the former limit feedback constant pressing system of this circuit, it adopts adaptively sampled mode, change down to sampling time automatic follow current peak change, compared with existing set time sample mode, the difference of the voltage drop of sample point secondary side diode when can greatly reduce even to eliminate different loads, thus output voltage precision is improved.
According to an aspect of of the present present invention, a kind of adaptively sampled circuit is provided, comprises: a peak reference voltage generation module, a computing module, a ramp voltage generation module, a comparison module, a pulse generate module; Wherein, described peak reference voltage generation module is for generating a current peak reference voltage; Described computing module is connected with described peak reference voltage generation module, for described current peak reference voltage is carried out scale operation, and exports a sample reference voltage to described comparison module; Described ramp voltage generation module for generation of a ramp voltage, and exports described comparison module to; Described comparison module is used for described sample reference voltage and described ramp voltage to compare, when described ramp voltage is greater than described sample reference voltage, export the sample identification signal of a high level, when described ramp voltage is less than or equal to described sample reference voltage, export a low level sample identification signal; Described pulse generate module for receiving sample identification signal, and at the rising edge of sample identification signal, produces a narrow pulse signal, so that adopt the sampling time automatic follow current peak change of the switch power supply system of adaptively sampled circuit and change.
In one embodiment of this invention, described computing module comprises: an operational amplifier, one first resistance and one second resistance; The first input end of described operational amplifier receives the current peak reference voltage of described peak reference voltage generation module, and the second input of described operational amplifier is electrically connected to one end of the first resistance and one end of the second resistance respectively; The other end of described first resistance is electrically connected to the output of described operational amplifier; The other end ground connection of described second resistance.
In one embodiment of this invention, described current peak reference voltage and described sample reference voltage in proportion amplify relation.
In one embodiment of this invention, described current peak reference voltage and described sample reference voltage in proportion reduce relation.
In one embodiment of this invention, described ramp voltage generation module comprises: one first fixed bias current source, a switch control unit, one first switch, a fixed voltage source and one first electric capacity; Wherein said first fixed bias current source is electrically connected to described fixed voltage source by described first switch, and described first fixed bias current source is electrically connected to one end of described first electric capacity, the other end ground connection of described first electric capacity; Described switch control unit for exporting a switch controlling signal, to control conducting or the shutoff of described first switch; When described first switch is conducting, the voltage of one end of described first electric capacity equals the voltage of described fixed voltage source, when described first switch is for turning off, charging to described first electric capacity in described first fixed bias current source, and is starting point and the ramp voltage risen at the voltage that one end of described first electric capacity generation one is equal with the voltage of described fixed voltage source.
In one embodiment of this invention, when described switch controlling signal is high level, described first switch is conducting; When described switch controlling signal is low level, described first switch is for turning off.
In one embodiment of this invention, described ramp voltage generation module comprises: one first fixed bias current source, a switch control unit, one first switch and one first electric capacity; Wherein said first fixed bias current source to be electrically connected ground connection by described first switch, and described first fixed bias current source is electrically connected to one end of described first electric capacity, the other end ground connection of described first electric capacity; Described switch control unit for exporting a switch controlling signal, to control conducting or the shutoff of described first switch; When described first switch is conducting, the voltage of one end of described first electric capacity equals zero, when described first switch is for turning off, charge to described first electric capacity in described first fixed bias current source, and produce in one end of described first electric capacity a no-voltage be starting point and rise ramp voltage.
In one embodiment of this invention, when described switch controlling signal is high level, described first switch is conducting; When described switch controlling signal is low level, described first switch is for turning off.
In one embodiment of this invention, described comparison module comprises: a comparator, for described sample reference voltage and described ramp voltage being compared, exports the sample identification signal of varying level according to comparative result.
According to another aspect of the present invention, provide a kind of printed circuit board (PCB), described printed circuit board (PCB) comprises above-mentioned adaptively sampled circuit.
According to another aspect of the present invention, there is provided a kind of former limit feedback constant pressing system, it comprises a rectifier bridge, a filtration module, starts supply module, a driver module, a former limit absorption module, a primary current sampling module, a voltage sample module, a voltage changing module, a secondary output module and a load; The input of wherein said rectifier bridge is electrically connected with city, for being direct current by AC rectification, and is sent to described filtration module; Described filtration module is used for carrying out filtering to direct current; Described startup supply module is connected with described filtration module, for making described driver module start, and powers to described driver module; Described driver module is connected with described former limit absorption module, for carrying out Isobarically Control, wherein said driver module comprises an Isobarically Control chip and a field effect transistor, and described Isobarically Control chip comprises adaptively sampled circuit described in any one in claim 1-8 item and loop back control module; Described former limit absorption module is for limiting the ceiling voltage of field effect transistor drain electrode when turning off of described driver module; Described primary current sampling module is connected with described driver module, for obtaining former limit winding current; Described voltage changing module is connected with described former limit absorption module, for the mutual conversion of the electric current and voltage between former limit, secondary, auxiliary limit winding; Described secondary output module is for exporting the voltage of a vice-side winding to described load; Described voltage sample model calling, to described driver module, for obtaining the demagnetization time internal feedback voltage in a cycle, and is sent to the described adaptively sampled circuit of described driver module; Described loop back control module is for receiving the narrow pulse signal of described adaptively sampled circuit, and utilize described narrow pulse signal to carry out sampling to feedback voltage signal to keep and error amplification, control the grid of the field effect transistor of described driver module simultaneously, control with the voltage close loop forming whole loop, and then make the sampling time automatic follow current peak change of described former limit feedback constant pressing system and change.
In one embodiment of this invention, described Isobarically Control chip comprises further: demagnetization detection module, a load current modular converter and a reference voltage generation module; Wherein, described demagnetization detection module is connected to described voltage sample module, in order to obtain the demagnetization time; Described load current modular converter is connected to described demagnetization detection module, in order to the relation according to described demagnetization time and work period, to generate the ratio-voltage being proportional to load current; Described reference voltage generation module is connected to described load current modular converter, for according to ratio-voltage generation current peak reference voltage, and is sent to the peak reference voltage generation module of described adaptively sampled circuit.
In one embodiment of this invention, when load is different, by arranging the resistance value of the current value in the fixed bias current source in described adaptively sampled circuit, the capacitance of the first electric capacity of described ramp voltage generation module and the first resistance of described computing module and the second resistance, to make the difference of the voltage drop of the 7th diode in described secondary output module for zero.
According to another aspect of the present invention, a kind of switch power supply system is provided, described switch power supply system comprises above-mentioned adaptively sampled circuit and a loop back control module, the narrow pulse signal that described loop back control module exports for receiving described adaptively sampled circuit, and utilize described narrow pulse signal to carry out sampling to feedback voltage signal to keep and error amplification, to realize the control of whole loop, and then make the sampling time of described switch power supply system automatic follow current peak change and change.
The invention has the advantages that, by adopting adaptively sampled circuit and adopting the former limit feedback constant pressing system of this circuit, sampling time automatic follow current peak change can be realized and change, compared with existing set time sample mode, the difference of the voltage drop of sample point secondary side diode when can greatly reduce even to eliminate different loads, thus output voltage precision is improved; And from power switch shutdown moment until the time delay between sampled point is realized capacitor charging by current source, whole circuit realiration is simple.
Accompanying drawing explanation
Fig. 1 is a kind of circuit connection diagram of conventional former limit feedback constant pressing system;
Fig. 2 is the waveform schematic diagram of the former limit feedback constant pressing system shown in Fig. 1;
Fig. 3 is the schematic diagram of the primary current peak value of former limit feedback constant pressing system in different loads situation shown in Fig. 1;
The operation principle schematic diagram that Fig. 4 is sampling time of the present invention automatic follow current peak change and changes;
Fig. 5 is the circuit connection diagram of an execution mode of adaptively sampled circuit of the present invention;
Fig. 6 is the respective waveforms figure of the internal signal of the adaptively sampled circuit shown in Fig. 5;
Fig. 7 is the circuit connection diagram of another execution mode of adaptively sampled circuit of the present invention;
Fig. 8 A and Fig. 8 B is the schematic diagram that the present invention adopts the former limit feedback constant pressing system of described adaptively sampled circuit;
Fig. 9 is the structural representation of the loop back control module of former limit of the present invention feedback constant pressing system.
Embodiment
Below in conjunction with accompanying drawing to adaptively sampled circuit provided by the invention and adopt the embodiment of the former limit feedback constant pressing system of this circuit to elaborate.
Fig. 3 is the schematic diagram of the primary current peak value of former limit feedback constant pressing system in different loads situation, and wherein, solid line is the waveform that primary current peak value is less; Dotted line is the waveform that primary current peak value is larger.As shown in Figure 3, for the constant-voltage system that former limit is fed back, be usually operated at discontinuous mode, for different primary current peak values (Ipp), secondary current peak value is equal proportion change (Isp) also, follow following equation: Isp=Nps*Ipp, wherein, Nps is the former secondary turn ratio.If use set time (Tsh) sampling, for different primary current peak value, the electric current that sample point secondary side diode flows through (i.e. secondary current is) is different, causes the pressure drop (V in sample point secondary side diode
d) different, be Δ V
ddifference, this Δ V
dvoltage differences can add on the output voltage, Vo=Vs-V
d, wherein, Vs is transformer secondary voltage (by feedback control loop, Vs keeps constant), and Vo is output voltage, during different loads, and V
dvariant, so output voltage also can be variant, and then export constant voltage precision and will inevitably reduce, especially for the lower system of output voltage, this difference can affect larger.
So the present invention proposes a kind of adaptively sampled circuit, and it is the Lookup protocol sampling time according to primary current peak value, but not is fixedly installed the sampling time, to solve the problem.That is, changed by the sampling time of the system adopting adaptively sampled circuit automatic follow current peak change, greatly reduce even to eliminate when different primary current peak value, the difference of the voltage drop that secondary side diode produces, thus improve output voltage precision.
Sampling time of the present invention shown in Figure 4 automatic follow current peak change and the operation principle schematic diagram changed, wherein ip is primary current waveform, and is is secondary current waveform, V
dfor secondary side diode voltage waveform.Waveform when dotted line and solid line difference correspondence two kinds of different loads, the current peak that the current peak that dotted line waveform is corresponding is more corresponding than solid line waveform is high.Tsh1 is sampling time delay corresponding to solid line waveform, and Tsh2 is the sampling time delay that dotted line waveform is corresponding.
The electric current that sample point flows through secondary side diode is shown below:
Wherein, Is_sh is sample point secondary side diode electric current, and Tdemag is the demagnetization time, and Tsh is the sampling time, and Nps is the former secondary turn ratio, and Ipp is former limit inductive current peak.Wherein the expression formula of Tdemag is as follows:
Ls is secondary inductance sensibility reciprocal, V
ofor output voltage, V
dfor secondary side diode pressure drop.
(2) are substituted into (1) obtain:
For the system that is determined, Nps, V
o, V
dand Ls is fixed value, therefore following equation can be extended from (3):
The sample point secondary side diode current expression that solid line is corresponding is:
The sample point secondary side diode current expression that dotted line is corresponding is:
If eliminate the difference of secondary side diode voltage drop corresponding to different primary current peak value, i.e. V
d1=V
d2=V
d, then the equation below demand fulfillment:
I
s_sh1＝I
s_sh2(4)
Again above-mentioned equation (3-1) and equation (3-2) are substituted into equation (4), can obtain:
If Tsh1 and Tsh2 meets the relation of above-mentioned equation (5), the difference of secondary side diode voltage drop corresponding to different primary current peak value can be eliminated.
Therefore, based on above-mentioned principle, the present invention proposes a kind of adaptively sampled circuit, refer to and hereafter illustrate.
Shown in Figure 5, in one embodiment of the present invention, a kind of adaptively sampled circuit comprises: comprise peak reference voltage generation module 510, computing module 520, ramp voltage generation module 530, comparison module 540, pulse generate module 550; Wherein, described peak reference voltage generation module 510 is for generating a current peak reference voltage Vcs_ref; Described computing module 520 is connected with described peak reference voltage generation module 510, for described current peak reference voltage Vcs_ref is carried out scale operation, and exports a sample reference voltage Vsh_ref to described comparison module 540; Described ramp voltage generation module 530 for generation of a ramp voltage Vramp, and exports described comparison module 540 to; Described comparison module 540 is for comparing described sample reference voltage Vsh_ref and described ramp voltage Vramp, when described ramp voltage Vramp is greater than described sample reference voltage Vsh_ref, export the sample identification signal (i.e. Tsample signal) of a high level, when described ramp voltage Vramp is less than or equal to described sample reference voltage Vsh_ref, export a low level sample identification signal; Described pulse generate module 550 is for receiving sample identification signal, and at the rising edge of sample identification signal, produce a narrow pulse signal (i.e. sampled signal), so that adopt the sampling time automatic follow current peak change of the Switching Power Supply of adaptively sampled circuit and change.Wherein, the concrete structure of described former limit feedback constant pressing system will be described in detail below.
Below by the structural relation of each module or circuit of illustrating adaptively sampled circuit.
Wherein, described computing module 520 comprises: an operational amplifier, one first resistance R1 and one second resistance R2; The first input end of described operational amplifier receives the current peak reference voltage of described peak reference voltage generation module 510, and the second input of described operational amplifier is electrically connected to one end of the first resistance R1 and one end of the second resistance R2 respectively; The other end of described first resistance R1 is electrically connected to the output of described operational amplifier; The other end ground connection of described second resistance R2.
In the present embodiment, described current peak reference voltage Vcs_ref and the proportional amplification relation of described sample reference voltage Vsh_ref.Under normal circumstances, because described current peak reference voltage Vcs_ref is less, be generally hundreds of millivolt, in order to make the sampling time more accurate, preferably, by operational amplifier to obtain the described sample reference voltage Vsh_ref of suitable magnitude.Certainly, in other embodiments, described current peak reference voltage Vcs_ref and described sample reference voltage Vsh_ref also can form scale smaller relation by operational amplifier.
In the present embodiment, preferably, described ramp voltage generation module 530 comprises: one first fixed bias current source Ib, switch control unit 531,1 first switch S 1, fixed voltage source Vsource and one first electric capacity C1; Wherein said first fixed bias current source is electrically connected to described fixed voltage source Vsource by described first switch S 1, and described first fixed bias current source Ib is electrically connected to one end of described first electric capacity C1, the other end ground connection of described first electric capacity C1; Described switch control unit 531 for exporting a switch controlling signal, to control conducting or the shutoff of described first switch S 1; When described first switch S 1 is for conducting, the voltage of one end of described first electric capacity C1 equals the voltage of described fixed voltage source Vsource, when described first switch S 1 is for turning off, described first fixed bias current source Ib charges to described first electric capacity C1, and is starting point and the ramp voltage Vramp risen at the voltage that one end of described first electric capacity C1 generation one is equal with the voltage of described fixed voltage source Vsource.Wherein, when can to arrange described switch controlling signal be high level, described first switch S 1 is conducting; When described switch controlling signal is low level, described first switch S 1 is for turning off.
Described comparison module 540 comprises: a comparator, for being compared by described sample reference voltage Vsh_ref and described ramp voltage Vramp, exports the sample identification signal of varying level according to comparative result.Described pulse generate module 550 is according to the sample identification signal of varying level, and at the rising edge place of sample identification signal, produce corresponding narrow pulse signal (i.e. sampled signal), so that adopt the sampling time automatic follow current peak change of the former limit feedback constant pressing system of adaptively sampled circuit and change.
That is, according to existing known equation Vcs_ref=Ipp*Rcs, known current peak reference voltage Vcs_ref is proportional to primary current peak I pp.In the present embodiment, by current peak reference voltage Vcs_ref is carried out scale amplifying, produce sample reference voltage Vsh_ref; When switch controlling signal Gate_ON is low level, first fixed bias current source Ib charges to the first electric capacity C1, produce a voltage equal with the voltage Vsource of fixed voltage source and be starting point and the ramp voltage Vramp risen, this ramp voltage Vramp and sample reference voltage Vsh_ref compares, produce the sample identification signal of varying level, again through the process of the pulse generation circuit (Timer_OneShot) of pulse generate module 550, obtain corresponding narrow pulse signal (i.e. sampled signal SH).
The respective waveforms figure of the internal signal of adaptively sampled circuit shown in Figure 6.Because current peak reference voltage Vcs_ref and sample reference voltage Vsh_ref is all directly proportional to primary current peak I pp, this ramp voltage Vramp is for starting point with the voltage equal with the voltage of described fixed voltage source, and it is in upward status, until sample reference voltage Vsh_ref, now reach sampled point, and then make Tsh and Ipp in from the first switch S 1 shutdown moment to the time of described sampled point linear.
Circuit diagram according to Fig. 4 obtains following formula:
In adaptively sampled circuit (wherein, described adaptively sampled circuit can be included in an Isobarically Control chip) C1, Vsource, Ib, R1 and R2 is fixed value, for the system determined (such as former limit feedback constant pressing system), Rcs is also fixed value, and the sampling time expression formula that can obtain two different primary current peak values corresponding from (6) formula is as follows:
Corresponding primary current peak I pp1, obtains:
Corresponding primary current peak I pp2, obtains:
Above-mentioned equation (6-2) both sides are deducted equation (6-1) simultaneously, and the relation obtaining Tsh1 and Tsh2 is as follows:
Contrast above-mentioned equation (5) and formula (7), at adaptively sampled circuit, (wherein, described adaptively sampled circuit can be included in an Isobarically Control chip IC 1, as shown in Figure 8 A and 8 B), can C1 be set, Ib, R1 and R2, make:
If adaptively sampled circuit (wherein, described adaptively sampled circuit can be included in an Isobarically Control chip IC 1) in C1, Ib, R1 and R2 arranges satisfied (8) formula, then foregoing circuit just achieves the difference eliminating secondary side diode voltage drop corresponding to different primary current peak value.That is, when load is different, by arranging the resistance value of the current value in the fixed bias current source in described adaptively sampled circuit, the capacitance of the first electric capacity of described ramp voltage generation module and the first resistance of described computing module and the second resistance, to make the difference of the voltage drop of the 7th diode in the secondary output module of the former limit feedback constant pressing system of the described adaptively sampled circuit of employing for zero, the difference of voltage drop is herein zero refer to and equal zero, or is approximately equal to zero.Like this, compared with the set time sample mode adopted with prior art, present embodiment greatly can reduce the difference of sample point secondary side diode voltage drop when even eliminating different loads, thus output voltage precision is improved.
Shown in Figure 7, the present invention also provides another execution mode of a kind of adaptively sampled circuit.In this embodiment, described sampling module 510, described computing module 520, described comparison module 540 and described pulse generate module 550 are identical with the modules structure in the execution mode shown in Fig. 5.Difference is, in the present embodiment, the first switch S 1 of described ramp voltage generation module 530 is ground connection, but not is electrically connected to described fixed voltage source.
Specifically, in the present embodiment, described ramp voltage generation module 530 comprises: one first fixed bias current source Ib, switch control unit 531,1 first switch S 1 and an one first electric capacity C1, can see Fig. 5; Wherein said first fixed bias current source Ib to be electrically connected ground connection by described first switch S 1, and described first fixed bias current source Ib is electrically connected to one end of described first electric capacity C1, the other end ground connection of described first electric capacity C1; Described switch control unit 531 for exporting a switch controlling signal, to control conducting or the shutoff of described first switch S 1; When described first switch S 1 is for conducting, the voltage of one end of described first electric capacity C1 equals zero, when described first switch S 1 is for turning off, described first fixed bias current source Ib charges to described first electric capacity C1, and produce in one end of described first electric capacity C1 a no-voltage be starting point and rise ramp voltage.Wherein, when described switch controlling signal is high level, described first switch S 1 is conducting; When described switch controlling signal is low level, described first switch S 1 is for turning off.
In the present embodiment, because current peak reference voltage Vcs_ref and sample reference voltage Vsh_ref is all directly proportional to primary current peak I pp, ramp voltage Vramp take no-voltage as starting point, and it is in upward status, until sample reference voltage Vsh_ref, now reach sampled point, and then make Tsh and Ipp in from the first switch S 1 shutdown moment to the time of described sampled point linear, so, so also can realize sampled point and automatically follow peak current change, and then greatly can reduce the difference of sample point secondary side diode voltage drop when even eliminating different loads, thus output voltage precision is improved.
Above-mentioned adaptively sampled circuit can be included in an Isobarically Control chip IC 1, and as shown in Figure 8 A and 8 B, and in other embodiments, described adaptively sampled circuit also can adopt individual devices to form, and is not comprised in chip IC 1 inner.
See Fig. 8 A and Fig. 8 B, and composition graphs 4-6, the present invention also provides a kind of former limit feedback constant pressing system, and it adopts above-mentioned adaptively sampled circuit.Described system comprises: rectifier bridge 820, filtration module 830, starts supply module 840, driver module 850, former limit absorption module 860, primary current sampling module 870, voltage sample module 8110, voltage changing module 880, secondary output module 890 and a load 8100.Wherein, the input of described rectifier bridge 820 is electrically connected with city, for being direct current by AC rectification, and is sent to described filtration module 830; Described filtration module 830 is for carrying out filtering to direct current; Described startup supply module 840 is connected with described filtration module 830, for making described driver module 850 start, and powers to described driver module 850; Described driver module 850 is connected with described former limit absorption module 860, for carrying out Isobarically Control, wherein said driver module 850 comprises Isobarically Control chip IC 1 and a field effect transistor Q1, described Isobarically Control chip IC 1 comprises a constant-voltage control circuit 900, and described constant-voltage control circuit 900 comprises above-mentioned adaptively sampled circuit and loop back control module 8120 (see Fig. 8 B); Described former limit absorption module 860 is for limiting the ceiling voltage of field effect transistor (described field effect transistor) drain electrode when turning off of described driver module 850; Described primary current sampling module 870 is connected with described driver module 850, for obtaining former limit winding current; Described voltage changing module 880 is connected with described former limit absorption module 860, for the mutual conversion of the electric current and voltage between former limit, secondary, auxiliary limit winding; Described secondary output module 890 is for exporting the voltage of a vice-side winding to described load 8100; Described voltage sample module 8110 is connected to described driver module 850, for obtaining the demagnetization time internal feedback voltage in a cycle, and is sent to the described adaptively sampled circuit of described driver module 850.
Below by each module of specific descriptions former limit feedback constant pressing system or the structural relation of circuit.
In the present embodiment, described rectifier bridge 820 comprises: the first diode D1, the second diode D2, the 3rd diode D3 and the 4th diode D4; The described first diode D1 of series connection and described 3rd diode D3 is in parallel with the described second diode D2 connected and the 4th diode D4.The negative pole of described first diode D1 is connected with the negative electricity of described second diode D2, the positive pole of described first diode D1 and the positive pole of described second diode D2 are electrically connected to the negative pole of described 3rd diode D3 and the negative pole of described 4th diode D4 respectively, and the positive pole of described 3rd diode D3 and the positive pole of described 4th diode D4 are electrically connected and ground connection.
Described filtration module 830 comprises: one second electric capacity C2, and described second electric capacity C2 is in parallel with the described second diode D2 connected and the 4th diode D4.That is, one end of described second electric capacity C2 is electrically connected to the negative pole of described second diode C2, and the other end of described second electric capacity C2 is electrically connected to the positive pole of described 4th diode D4.
Described startup supply module 840 comprises: a starting resistance Rst, one the 3rd electric capacity C3 and the 6th diode D6; The common connecting point of described starting resistance Rst and described 3rd electric capacity C3 is electrically connected to the negative pole of described driver module 850 and described 6th diode D6 respectively; The other end ground connection of described 3rd electric capacity C3; The other end of described starting resistance Rst is electrically connected to one end of described filtration module 830.The positive pole of described 6th diode D6 is electrically connected to sample coil (not marking in figure).
Described driver module 850 comprises: Isobarically Control chip IC 1 and a field effect transistor Q1.Described Isobarically Control chip IC 1 can comprise constant-voltage control circuit 900, as shown in Figure 8 A.The VCC pin of described Isobarically Control chip IC 1 is electrically connected to the negative pole of the described 6th diode D6 of described startup supply module 840, the GATE pin of described Isobarically Control chip IC 1 is electrically connected to the grid of described field effect transistor Q1, the FB pin of described Isobarically Control chip IC 1 is electrically connected to described voltage sample module 8110, the CS pin of described Isobarically Control chip IC 1 is electrically connected to described primary current sampling module 870, the GND pin ground connection of described Isobarically Control chip IC 1; The source electrode that the drain electrode of described field effect transistor Q1 is electrically connected to described former limit absorption module 860, described field effect transistor Q1 is electrically connected to described primary current sampling module 870.Described constant-voltage control circuit 900 comprises above-mentioned adaptively sampled circuit and loop back control module 8120.Wherein, described loop back control module 8120 is for receiving the narrow pulse signal of described adaptively sampled circuit, and utilize described narrow pulse signal to carry out sampling to feedback voltage signal to keep and error amplification, control the grid of the field effect transistor Q1 of described driver module 850 simultaneously, control with the voltage close loop forming whole loop, and then make the sampling time automatic follow current peak change of described former limit feedback constant pressing system and change.
Described former limit absorption module 860 comprises: one the 4th resistance R4, one the 5th electric capacity C5, one the 5th diode D5; Described 5th electric capacity C5 connects with described 5th diode D5 with after described 4th resistance R4 parallel connection again.One end of described 4th resistance R4 is electrically connected to one end of described starting resistance Rst, and the other end is electrically connected to the negative pole of described 5th diode D5.The positive pole of described 5th diode D5 is electrically connected to the drain electrode of the field effect transistor of described driver module 850.
Described primary current sampling module 870 comprises: a sampling resistor Rcs, for obtaining former limit winding current.One end of described sampling resistor Rcs is electrically connected to the CS pin of the Isobarically Control chip IC 1 of described driver module 850, the other end ground connection of described sampling resistor Rcs.
Described voltage changing module 880 comprises: primary coil, secondary coil, sample coil (not marking in figure) and iron core T1.
Described secondary output module 890 comprises: one the 7th diode D7 and the 4th electric capacity C4; Described 7th diode D7 connects with described 4th electric capacity C4, and described 4th electric capacity C4 is in parallel with described load 8100.That is, the negative electricity of described 7th diode D7 is connected to one end of described 4th electric capacity C4.
Described voltage sample module 8110 comprises: one the 3rd resistance R3 and the 4th resistance R4; The common connecting point of described 3rd resistance R3 and described 4th resistance R4 is electrically connected to the FB pin of the Isobarically Control chip IC 1 of described driver module 850; The other end of described 3rd resistance R3 is electrically connected to described startup supply module 840; The other end ground connection of described 4th resistance R4.
See Fig. 9, described loop back control module 8120 can comprise a second switch S2, one the 6th electric capacity C6, an error amplifier (being called for short EA), a PFM/PWM modulator.Described loop back control module 8120 is after receiving narrow pulse signal, described narrow pulse signal carries out sampling to feedback voltage signal and keeps, amplify after process through error, feed back to the grid (as shown in Figure 8 A) of described field effect transistor Q1, thus form a voltage close loop control, and then make the sampling time automatic follow current peak change of described former limit feedback constant pressing system and change.
In the present embodiment, described constant-voltage control circuit 900 can comprise further: demagnetization detection module 8130, load current modular converter 8140 and a reference voltage generation module 8150; Wherein, described demagnetization detection module 8130 is connected to described voltage sample module 8110, in order to obtain the demagnetization time; Described load current modular converter 8140 is connected to described demagnetization detection module 8130, in order to the relation according to described demagnetization time and work period, to generate the ratio-voltage being proportional to load current; Described reference voltage generation module 8150 is connected to described load current modular converter 8140, for according to ratio-voltage generation current peak reference voltage, and is sent to the peak reference voltage generation module of described adaptively sampled circuit.The input signal of described constant-voltage control circuit 900 is the CS signal of FB signal by the FB pin of described Isobarically Control chip IC 1 and CS pin, and the output signal of described constant-voltage control circuit 900 is the GATE signal of the GATE pin by described Isobarically Control chip IC 1.
In the present embodiment, detect demagnetization by FB pin, obtain demagnetization time Tdemag, then, the ratio-voltage Vload being proportional to load current is produced by the relation of demagnetization time and work period Tsw, then according to ratio-voltage Vload generation current peak reference voltage Vcs_ref.So according to existing known equation Vcs_ref=Ipp*Rcs, known current peak reference voltage Vcs_ref is proportional to primary current peak I pp.
According to mentioned above, ramp voltage Vramp is for starting point with the voltage equal with the voltage of described fixed voltage source, and it is in upward status, until sample reference voltage Vsh_ref, now reach sampled point, and then make Tsh and Ipp in from the first switch S 1 shutdown moment to the time of described sampled point linear, so sampled point also can be achieved automatically follow peak current change, and then greatly can reduce the difference of sample point secondary side diode (D7) voltage drop when even eliminating different loads, thus output voltage precision is improved.
In addition, above-mentioned self adaptation adopts sample circuit except being applied to former limit feedback constant pressing system, and all right application examples is as switch power supply system (not shown).Described switch power supply system can comprise adaptively sampled circuit and a loop back control module, the narrow pulse signal that described loop back control module exports for receiving described adaptively sampled circuit, and utilize described narrow pulse signal to carry out sampling to feedback voltage signal to keep and error amplification, to realize the control of whole loop, and then make the sampling time of described switch power supply system automatic follow current peak change and change.
The above is only the preferred embodiment of the present invention; it should be pointed out that for those skilled in the art, under the premise without departing from the principles of the invention; can also make some improvements and modifications, these improvements and modifications also should be considered as protection scope of the present invention.
Claims (14)
1. an adaptively sampled circuit, is characterized in that, comprising: a peak reference voltage generation module, a computing module, a ramp voltage generation module, a comparison module, a pulse generate module; Wherein,
Described peak reference voltage generation module is for generating a current peak reference voltage;
Described computing module is connected with described peak reference voltage generation module, for described current peak reference voltage is carried out scale operation, and exports a sample reference voltage to described comparison module;
Described ramp voltage generation module for generation of a ramp voltage, and exports described comparison module to;
Described comparison module is used for described sample reference voltage and described ramp voltage to compare, when described ramp voltage is greater than described sample reference voltage, export the sample identification signal of a high level, when described ramp voltage is less than or equal to described sample reference voltage, export a low level sample identification signal;
Described pulse generate module for receiving sample identification signal, and at the rising edge of sample identification signal, produces a narrow pulse signal, so that adopt the sampling time automatic follow current peak change of the switch power supply system of adaptively sampled circuit and change.
2. adaptively sampled circuit according to claim 1, is characterized in that, described computing module comprises: an operational amplifier, one first resistance and one second resistance; The first input end of described operational amplifier receives the current peak reference voltage of described peak reference voltage generation module, and the second input of described operational amplifier is electrically connected to one end of the first resistance and one end of the second resistance respectively; The other end of described first resistance is electrically connected to the output of described operational amplifier; The other end ground connection of described second resistance.
3. adaptively sampled circuit according to claim 1, is characterized in that, described current peak reference voltage and described sample reference voltage in proportion amplify relation.
4. adaptively sampled circuit according to claim 1, is characterized in that, described current peak reference voltage and described sample reference voltage in proportion reduce relation.
5. adaptively sampled circuit according to claim 1, is characterized in that, described ramp voltage generation module comprises: one first fixed bias current source, a switch control unit, one first switch, a fixed voltage source and one first electric capacity; Wherein said first fixed bias current source is electrically connected to described fixed voltage source by described first switch, and described first fixed bias current source is electrically connected to one end of described first electric capacity, the other end ground connection of described first electric capacity; Described switch control unit for exporting a switch controlling signal, to control conducting or the shutoff of described first switch; When described first switch is conducting, the voltage of one end of described first electric capacity equals the voltage of described fixed voltage source, when described first switch is for turning off, charging to described first electric capacity in described first fixed bias current source, and is starting point and the ramp voltage risen at the voltage that one end of described first electric capacity generation one is equal with the voltage of described fixed voltage source.
6. adaptively sampled circuit according to claim 5, is characterized in that, when described switch controlling signal is high level, described first switch is conducting; When described switch controlling signal is low level, described first switch is for turning off.
7. adaptively sampled circuit according to claim 1, is characterized in that, described ramp voltage generation module comprises: one first fixed bias current source, a switch control unit, one first switch and one first electric capacity; Wherein said first fixed bias current source to be electrically connected ground connection by described first switch, and described first fixed bias current source is electrically connected to one end of described first electric capacity, the other end ground connection of described first electric capacity; Described switch control unit for exporting a switch controlling signal, to control conducting or the shutoff of described first switch; When described first switch is conducting, the voltage of one end of described first electric capacity equals zero, when described first switch is for turning off, charge to described first electric capacity in described first fixed bias current source, and produce in one end of described first electric capacity a no-voltage be starting point and rise ramp voltage.
8. adaptively sampled circuit according to claim 7, is characterized in that, when described switch controlling signal is high level, described first switch is conducting; When described switch controlling signal is low level, described first switch is for turning off.
9. adaptively sampled circuit according to claim 1, is characterized in that, described comparison module comprises: a comparator, for described sample reference voltage and described ramp voltage being compared, exports the sample identification signal of varying level according to comparative result.
10. a printed circuit board (PCB), is characterized in that, described printed circuit board (PCB) comprises the adaptively sampled circuit described in any one in claim 1-9 item.
11. 1 kinds of former limit feedback constant pressing systems, it is characterized in that, comprise a rectifier bridge, a filtration module, starts supply module, a driver module, a former limit absorption module, a primary current sampling module, a voltage sample module, a voltage changing module, a secondary output module and a load; Wherein
The input of described rectifier bridge is electrically connected with city, for being direct current by AC rectification, and is sent to described filtration module;
Described filtration module is used for carrying out filtering to direct current;
Described startup supply module is connected with described filtration module, for making described driver module start, and powers to described driver module;
Described driver module is connected with described former limit absorption module, for carrying out Isobarically Control, wherein said driver module comprises an Isobarically Control chip and a field effect transistor, and described Isobarically Control chip comprises adaptively sampled circuit described in any one in claim 1-9 item and loop back control module;
Described former limit absorption module is for limiting the ceiling voltage of field effect transistor drain electrode when turning off of described driver module;
Described primary current sampling module is connected with described driver module, for obtaining former limit winding current;
Described voltage changing module is connected with described former limit absorption module, for the mutual conversion of the electric current and voltage between former limit, secondary, auxiliary limit winding;
Described secondary output module is for exporting the voltage of a vice-side winding to described load;
Described voltage sample model calling, to described driver module, for obtaining the demagnetization time internal feedback voltage in a cycle, and is sent to the described adaptively sampled circuit of described driver module;
Described loop back control module is for receiving the narrow pulse signal of described adaptively sampled circuit, and utilize described narrow pulse signal to carry out sampling to feedback voltage signal to keep and error amplification, control the grid of the field effect transistor of described driver module simultaneously, control with the voltage close loop forming whole loop, and then make the sampling time automatic follow current peak change of described former limit feedback constant pressing system and change.
12. former limit according to claim 11 feedback constant pressing systems, it is characterized in that, described Isobarically Control chip comprises further: demagnetization detection module, a load current modular converter and a reference voltage generation module; Wherein,
Described demagnetization detection module is connected to described voltage sample module, in order to obtain the demagnetization time;
Described load current modular converter is connected to described demagnetization detection module, in order to the relation according to described demagnetization time and work period, to generate the ratio-voltage being proportional to load current;
Described reference voltage generation module is connected to described load current modular converter, for according to ratio-voltage generation current peak reference voltage, and is sent to the peak reference voltage generation module of described adaptively sampled circuit.
13. former limit according to claim 12 feedback constant pressing systems, it is characterized in that, when load is different, by arranging the resistance value of the current value in the fixed bias current source in described adaptively sampled circuit, the capacitance of the first electric capacity of described ramp voltage generation module and the first resistance of described computing module and the second resistance, to make the difference of the voltage drop of the 7th diode in described secondary output module for zero.
14. 1 kinds of switch power supply systems, it is characterized in that, described switch power supply system comprises adaptively sampled circuit described in any one in claim 1-9 and a loop back control module, the narrow pulse signal that described loop back control module exports for receiving described adaptively sampled circuit, and utilize described narrow pulse signal to carry out sampling to feedback voltage signal to keep and error amplification, to realize the control of whole loop, and then make the sampling time of described switch power supply system automatic follow current peak change and change.
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