CN103036428A - Peak current gradient synchronous step-down circuit - Google Patents
Peak current gradient synchronous step-down circuit Download PDFInfo
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- CN103036428A CN103036428A CN 201210568102 CN201210568102A CN103036428A CN 103036428 A CN103036428 A CN 103036428A CN 201210568102 CN201210568102 CN 201210568102 CN 201210568102 A CN201210568102 A CN 201210568102A CN 103036428 A CN103036428 A CN 103036428A
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Abstract
The invention provides a peak current gradient synchronous step-down circuit and solves the problem that a synchronous step-down circuit in the prior art is large in inductor current ripple under the state of light load. The peak current gradient synchronous step-down circuit comprises an input port, an output port, an upper power switch, a lower power switch, an output inducer, an output capacitor, a sampling resistor, an operational amplifier, a feedback unit, a voltage comparator, a error amplifier, a clamper, a first logic switch, a second logic switch, a current comparator and a control/drive circuit. The peak current gradient synchronous step-down circuit can reduce the inductor current ripple when the synchronous step-down under the sate of light load.
Description
Technical field
The present invention relates to electronic technology field, particularly a kind of synchronous buck circuit of peak current gradual change.
Background technology
The synchronous buck circuit is applied to usually when the required voltage occasion lower than the voltage of power supply.The representative synchronization reduction voltage circuit comprises upper power switch S1, lower power switch S2, output inductor L and the output capacitor Co that couples as shown in Figure 1.Existing synchronous buck circuit adopts peak-current mode control usually, makes the peak value of the inductive current of synchronous buck circuit be adjusted to a constant peak.Yet use this control mode, no matter the synchronous buck circuit is in heavy condition or light condition, and its inductive current peak all is adjusted to same peak value.So that converter inductive current ripple under light condition is very large.
Summary of the invention
The present invention proposes a kind of synchronous buck circuit of peak current gradual change, has solved existing synchronous buck circuit large problem of ripple under light condition.
Technical scheme of the present invention is achieved in that
A kind of synchronous buck circuit of peak current gradual change comprises: input port receives input voltage; Output port provides output voltage; Upper power switch and lower power switch are coupled in series in input port and with reference between the ground; Output inductor is coupled between the coupled in series node and output port of power switch and lower power switch; Output capacitor is coupled in output port and with reference between the ground; Sampling resistor is with upper power switch coupled in series; Operational amplifier has first input end, the second input terminal and lead-out terminal, and its first input end and the second input terminal are connected across the sampling resistor two ends, and its lead-out terminal produces the inductive current sampled signal; Feedback component is coupled to output port and receives output voltage, and produces the feedback voltage of reflection output voltage; Voltage comparator has in-phase input end, inverting input and lead-out terminal, and its inverting input threshold level voltage, its in-phase input end are coupled to feedback component and receive feedback voltage, and its lead-out terminal produces voltage comparison signal; Error amplifier has in-phase input end, inverting input and lead-out terminal, and its in-phase input end receives reference voltage, and its inverting input is coupled to feedback component and receives feedback voltage, and its lead-out terminal produces error amplification signal; Clamper is coupled in the lead-out terminal of error amplifier and with reference between the ground; The first logic switch has the first terminal, the second terminal and control terminal, and the lead-out terminal that its first terminal is coupled to error amplifier receives error amplification signal, and its control terminal is coupled to the lead-out terminal receiver voltage comparison signal of voltage comparator; The second logic switch has the first terminal, the second terminal and control terminal, and its first terminal couples current peak signal, and its control terminal is coupled to the lead-out terminal receiver voltage comparison signal of voltage comparator; Current comparator, have in-phase input end, inverting input and lead-out terminal, its in-phase input end is coupled to the lead-out terminal received current sampled signal of operational amplifier, its inverting input is coupled to the second terminal of the first logic switch and the second terminal of the second logic switch, its lead-out terminal generation current comparison signal; Control and drive circuit are coupled to the lead-out terminal received current comparison signal of current comparator, and based on the electric current comparison signal, produce double switch and drive signal, to control the break-make of upper power switch and lower power switch.
Alternatively, described feedback component comprises and is coupled in series in output port and with reference to the first resistance between the ground and the second resistance that wherein feedback voltage produces at the coupled in series Nodes of the first resistance and the second resistance.
Alternatively, described the first logic switch is the high level conducting, and the second logic switch is the low level conducting.
Alternatively, described clamper comprises Zener diode.
Alternatively, described synchronous buck circuit further comprises: the first compensation condenser is coupled in the lead-out terminal of operational amplifier and with reference between the ground.
Alternatively, described synchronous buck circuit further comprises: the second compensation condenser is coupled between the lead-out terminal and inverting input of error amplifier.
The invention has the beneficial effects as follows: can reduce the inductive current ripple of synchronous buck circuit under light condition.
Description of drawings
In order to be illustrated more clearly in the embodiment of the invention or technical scheme of the prior art, the below will do to introduce simply to the accompanying drawing of required use in embodiment or the description of the Prior Art, apparently, accompanying drawing in the following describes only is some embodiments of the present invention, for those of ordinary skills, under the prerequisite of not paying creative work, can also obtain according to these accompanying drawings other accompanying drawing.
Fig. 1 is the typical circuit structural representation of existing synchronous buck circuit;
Fig. 2 is the electrical block diagram of the synchronous buck circuit 100 of a kind of peak current gradual change of the present invention.
Embodiment
Below in conjunction with the accompanying drawing in the embodiment of the invention, the technical scheme in the embodiment of the invention is clearly and completely described, obviously, described embodiment only is the present invention's part embodiment, rather than whole embodiment.Based on the embodiment among the present invention, those of ordinary skills belong to the scope of protection of the invention not paying the every other embodiment that obtains under the creative work prerequisite.
As shown in Figure 2, the synchronous buck circuit 100 of peak current gradual change of the present invention comprises: input port 101 receives input voltage vin; Output port 102 provides output voltage V o; Upper power switch 103 and lower power switch 104 are coupled in series in input port 101 and with reference between the ground; Output inductor 105 is coupled between the coupled in series node and output port 102 of power switch 103 and lower power switch 104; Output capacitor 106 is coupled in output port 102 and with reference between the ground; Sampling resistor 107 is with upper power switch 103 coupled in series; Operational amplifier 108 has first input end, the second input terminal and lead-out terminal, and its first input end and the second input terminal are connected across sampling resistor 107 two ends, its lead-out terminal generation current sampled signal Isen; Feedback component 109 is coupled to output port 102 and receives output voltage V o, and produces the feedback voltage Vfb of reflection output voltage V o; Voltage comparator 110 has in-phase input end, inverting input and lead-out terminal, and its inverting input threshold level voltage Vth, its in-phase input end are coupled to feedback component 109 and receive feedback voltage Vfb, and its lead-out terminal produces voltage comparison signal; Error amplifier 111 has in-phase input end, inverting input and lead-out terminal, and its in-phase input end receives reference voltage Vref, and its inverting input is coupled to feedback component 109 and receives feedback voltage Vfb, and its lead-out terminal produces error amplification signal Vc; Clamper 112 is coupled in the lead-out terminal of error amplifier 111 and with reference between the ground; The first logic switch 113, have the first terminal, the second terminal and control terminal, the lead-out terminal that its first terminal is coupled to error amplifier 111 receives error amplification signal Vc, and its control terminal is coupled to the lead-out terminal receiver voltage comparison signal of voltage comparator 110; The second logic switch 114 has the first terminal, the second terminal and control terminal, and its first terminal couples current peak signal Ilim, and its control terminal is coupled to the lead-out terminal receiver voltage comparison signal of voltage comparator 110; Current comparator 115, have in-phase input end, inverting input and lead-out terminal, its in-phase input end is coupled to the lead-out terminal received current sampled signal Isen of operational amplifier 108, its inverting input is coupled to the second terminal of the first logic switch 113 and the second terminal of the second logic switch 114, its lead-out terminal generation current comparison signal; Control and drive circuit 116 are coupled to the lead-out terminal received current comparison signal of current comparator 115, and based on the electric current comparison signal, produce double switch and drive signal, to control the break-make of upper power switch 103 and lower power switch 104.
Preferably, the synchronous buck circuit 100 of described peak current gradual change also comprises: the first compensation condenser 117 is coupled in the lead-out terminal of operational amplifier 108 and with reference between the ground.
Preferably, the synchronous buck circuit 100 of described peak current gradual change also comprises: the second compensation condenser 118 is coupled between the lead-out terminal and inverting input of error amplifier 111.
Preferably, feedback component 109 comprises and is coupled in series in output port 102 and with reference to the first resistance between the ground and the second resistance that wherein feedback voltage Vfb produces at the series connection node place of the first resistance and the second resistance.
Preferably, clamper 112 comprises Zener diode, and has clamping voltage Vz.
Preferably, the first logic switch 113 is the high level conducting, and the second logic switch 114 is the low level conducting.That is to say, when feedback voltage Vfb during greater than threshold voltage Vth, voltage comparison signal is high level, this moment the first logic switch 113 be switched on, the second logic switch 114 is disconnected, and receives error amplification signal Vc so that the inverting input of current comparator 115 receives the lead-out terminal that is coupled to error amplifier 111; When feedback voltage Vfb during less than threshold voltage Vth, voltage comparison signal is low level, this moment the first logic switch 113 be disconnected, the second logic switch 114 is switched on, so that the inverting input received current peak signal Ilim of current comparator 115.
When the synchronous buck circuit 100 normal operation of peak current gradual change, when upper power switch 103 is switched on, lower power switch 104 is disconnected, input voltage vin is transmitted and is converted into output voltage V o via sampling resistor 107, upper power switch 103, output inductor 105 and output capacitor 106.This moment, inductive current was the electric current that flows through sampling resistor 107.This electric current begins to increase.Then the inductive current sampled signal Isen of operational amplifier 108 outputs also begins to increase.When it increases to the signal of current comparator 115 inverting inputs, the electric current comparison signal trigging signal of current comparator 115 outputs.Accordingly, the two-way of control and drive circuit 116 outputs drives the signal trigging signal, so that upper power switch 103 is disconnected, lower power switch 104 is switched on.
When the load of the synchronous buck circuit 100 of peak current gradual change is relatively heavier, output voltage V o less, then also less of feedback voltage Vfb.Feedback voltage Vfb is less than threshold voltage Vth at this moment, and the voltage comparison signal of voltage comparator 110 outputs is low level.Then the first logic switch 113 is disconnected, the second logic switch 114 is switched on, so that the inverting input received current peak signal Ilim of current comparator 115.Namely under heavy condition, when current sampling signal Isen reaches current peak signal Ilim, the electric current comparison signal trigging signal of current comparator 115 output, so via behind control and the drive circuit 116 upper power switch 103 is disconnected, with lower power switch 104 conductings.
When the load of the synchronous buck circuit 100 of peak current gradual change was relatively light, output voltage V o was relatively large, and then feedback voltage Vfb is also relatively large.Feedback voltage Vfb is greater than threshold voltage Vth at this moment, and the voltage comparison signal of voltage comparator 110 outputs is high level.Then the first logic switch 113 is switched on, the second logic switch 114 is disconnected, so that the inverting input of current comparator 115 receives error amplification signal Vc.Namely under light condition, when current sampling signal Isen reaches error amplification signal Vc, the electric current comparison signal trigging signal of current comparator 115 output, so via behind control and the drive circuit 116 upper power switch 103 is disconnected, with lower power switch 104 conductings.And error amplification signal Vc is the integration of feedback voltage Vfb and reference voltage Vref difference.This error amplification signal Vc slowly changes along with the variation of feedback voltage Vfb.When feedback voltage Vfb slowly increases, it is large that error amplification signal Vc also slowly becomes.When it increased to the clamping voltage Vz of clamper 112, error amplification signal Vc was clamped at clamping voltage Vz place.
Therefore, the synchronous buck circuit 100 of peak current gradual change is under light condition, and its inductive current peak slowly changes, and its maximum is clamped at clamping voltage Vz place, thereby has reduced the inductive current ripple under its light condition.
The above only is preferred embodiment of the present invention, and is in order to limit the present invention, within the spirit and principles in the present invention not all, any modification of doing, is equal to replacement, improvement etc., all should be included within protection scope of the present invention.
Claims (6)
1. the synchronous buck circuit of a peak current gradual change is characterized in that, comprising:
Input port receives input voltage;
Output port provides output voltage;
Upper power switch and lower power switch are coupled in series in input port and with reference between the ground;
Output inductor is coupled between the coupled in series node and output port of power switch and lower power switch;
Output capacitor is coupled in output port and with reference between the ground;
Sampling resistor is with upper power switch coupled in series;
Operational amplifier has first input end, the second input terminal and lead-out terminal, and its first input end and the second input terminal are connected across the sampling resistor two ends, and its lead-out terminal produces the inductive current sampled signal;
Feedback component is coupled to output port and receives output voltage, and produces the feedback voltage of reflection output voltage;
Voltage comparator has in-phase input end, inverting input and lead-out terminal, and its inverting input threshold level voltage, its in-phase input end are coupled to feedback component and receive feedback voltage, and its lead-out terminal produces voltage comparison signal;
Error amplifier has in-phase input end, inverting input and lead-out terminal, and its in-phase input end receives reference voltage, and its inverting input is coupled to feedback component and receives feedback voltage, and its lead-out terminal produces error amplification signal;
Clamper is coupled in the lead-out terminal of error amplifier and with reference between the ground;
The first logic switch has the first terminal, the second terminal and control terminal, and the lead-out terminal that its first terminal is coupled to error amplifier receives error amplification signal, and its control terminal is coupled to the lead-out terminal receiver voltage comparison signal of voltage comparator;
The second logic switch has the first terminal, the second terminal and control terminal, and its first terminal couples current peak signal, and its control terminal is coupled to the lead-out terminal receiver voltage comparison signal of voltage comparator;
Current comparator, have in-phase input end, inverting input and lead-out terminal, its in-phase input end is coupled to the lead-out terminal received current sampled signal of operational amplifier, its inverting input is coupled to the second terminal of the first logic switch and the second terminal of the second logic switch, its lead-out terminal generation current comparison signal;
Control and drive circuit are coupled to the lead-out terminal received current comparison signal of current comparator, and based on the electric current comparison signal, produce double switch and drive signal, to control the break-make of upper power switch and lower power switch.
2. the synchronous buck circuit of peak current gradual change as claimed in claim 1 is characterized in that, also comprises:
The first compensation condenser is coupled in the lead-out terminal of operational amplifier and with reference between the ground.
3. the synchronous buck circuit of peak current gradual change as claimed in claim 1 is characterized in that, also comprises: the second compensation condenser is coupled between the lead-out terminal and inverting input of error amplifier.
4. the synchronous buck circuit of peak current gradual change as claimed in claim 1, it is characterized in that, described feedback component comprises and is coupled in series in output port and with reference to the first resistance between the ground and the second resistance that wherein feedback voltage produces at the coupled in series Nodes of the first resistance and the second resistance.
5. the synchronous buck circuit of peak current gradual change as claimed in claim 1 is characterized in that, described clamper comprises Zener diode.
6. the synchronous buck circuit of peak current gradual change as claimed in claim 1 is characterized in that, wherein said the first logic switch is the high level conducting, and the second logic switch is the low level conducting.
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| Application Number | Priority Date | Filing Date | Title |
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| CN 201210568102 CN103036428A (en) | 2012-12-12 | 2012-12-12 | Peak current gradient synchronous step-down circuit |
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| Application Number | Priority Date | Filing Date | Title |
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| CN 201210568102 CN103036428A (en) | 2012-12-12 | 2012-12-12 | Peak current gradient synchronous step-down circuit |
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Application publication date: 20130410 |