CN1941576A - DC/DC converter with inductor current sensing capability - Google Patents
DC/DC converter with inductor current sensing capability Download PDFInfo
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- CN1941576A CN1941576A CN 200610152327 CN200610152327A CN1941576A CN 1941576 A CN1941576 A CN 1941576A CN 200610152327 CN200610152327 CN 200610152327 CN 200610152327 A CN200610152327 A CN 200610152327A CN 1941576 A CN1941576 A CN 1941576A
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Abstract
A DC/DC converter for converting an input voltage to an output voltage comprises a switch, an inductor, two voltage dividers, a capacitor, and a controller. The switch coupled to the input voltage. The inductor having a parasitic direct current resistance is used for coupling the switch to an output node of the DC/DC converter so as to generate the output voltage at the output node. The first voltage divider is coupled to the output node for generating a divided voltage of the output voltage. The second voltage divider is coupled to the switch and ground. The capacitor coupled to the first voltage divider and the second divider to measure the current through the inductor by sensing a voltage across the capacitor. The controller coupled to the first switch for enabling and disenabling it so as to discontinuously providing power from the input voltage to the inductor.
Description
Related application
The application's priority is based on the U.S. Provisional Patent Application of by name " dividing potential drop inductance DCR current detecting ", sequence number 60/720,754, and registration on September 27th, 2005, its content is fully with reference to being herein incorporated.
Technical field
The present invention system is specially DC to DC converter about the power management of circuit.
Background technology
DC to DC converter is widely used in the stable DC output voltage that a DC input voitage is transformed to a default size (being higher or lower than this input voltage) at electronic applications.This type of circuit or device generally use the semiconductor switch control structure, and efficient is very high, and volume is little, therefore become the important component part of various electronic equipment power sources.DC to DC converter contains a controller, is used to receive feedback signal (as electric current and voltage feedback signal) and output voltage or electric current are adjusted to required size.
Usually in DC to DC converter, obtain current information and it is used as the current feedback signal by the flow through electric current of inductance of detection.The flow through electric current of inductance of detection can have several different methods, wherein a kind ofly detects resistance and connects with outputting inductance and detect size of current for using.Flow through this resistance size of current for this resistance both end voltage divided by its resistance.Use this method to cause unavoidablely and detect ohmically power loss.
For raising the efficiency, the another kind of method that detects electric current is to use inductance series resistance in the inductor as current measuring element, and this resistance also is called D.C. resistance (DCR).This method is used the resistance and the electric capacity of a series connection, and the two is in parallel with inductance.When the time constant coupling of the time constant of resistance and electric capacity and inductance and inductance series resistance, the electric current of the inductance of flowing through can obtain by detected electric capacity both end voltage.
Fig. 1 is the DC to DC converter 100 of current techniques.DC to DC converter 100 is typical buck converter, uses resistance and capacitance network 117 to detect the electric current of the inductance 106 of flowing through.Use a mos field effect transistor (MOSFET) to be connected to inductance 106 and transmit input voltages (Vin), and output voltage is transferred to load 130 to give inductance 106 off and on.Inductance 106 contains the parasitic DCR resistance 108 of an inductance.Be equal in the model at another, inductance 106 is connected with DCR resistance 108, as shown in Figure 1.Voltage divider that comprises resistance 112 and 114 is connected on the output voltage of DC to DC converter 100 to generate branch pressure voltage.Resistance and capacitance network 117 comprise resistance 116 and electric capacity 110, and the two series connection is also in parallel with inductance 106 and DCR resistance 108.As shown in Figure 1, resistance 116 and electric capacity 110 and inductance 106 and parasitic DCR resistance 108 electric currents that detect the inductance 106 of flowing through with formation resistance and capacitance network in parallel of inductance.Connect a MOSFET 104 to MOSFET 102, when MOSFET 102 closed, this MOSFET104 made inductance 106 discharges.DC to DC converter 100 also comprises a controller 120, below is described in detail.
Controller 120 has a HDR pin and a LDR pin, is connected respectively to MOSFET 102 and 104 with these two MOSFET of switch.CSP pin and CSN pin that the two ends of electric capacity 110 are connected to controller 120 make controller 120 can detect or receive the voltage at electric capacity 110 two ends.The FB pin of controller 120 is connected to node between resistance 112 and 114 to receive feedback signal, the i.e. dividing potential drop of output voltage.
It will be understood by those skilled in the art that if the time constant of the time constant of inductance and resistance and capacitance network coupling the voltage at electric capacity 110 two ends promptly equal the to flow through electric current of inductance multiply by the resistance of DCR resistance 108, that is to say that equation (1) is set up:
L/DCR＝R*C………………………………………(1)
L is the inductance value of inductance 106 in the above equation, and DCR is the resistance of inductance DCR resistance 108, and R is the resistance of resistance 116, and C is the capacitance of electric capacity 110.The electric current of inductance 106 of flowing through equals the resistance of electric capacity 110 both end voltage divided by DCR resistance 108.The resistance of DCR resistance 108 is known, and the voltage at electric capacity 110 two ends can detect or measure by the CSP of controller 120 and the input of CSN pin.Like this, controller 120 can detect the electric current of the inductance 106 of flowing through and control MOSFET 102 and 104 according to this current information.
Yet because the voltage on the CSN pin of controller 120 equals the output voltage of DC to DC converter 100, in case output voltage is higher, the output voltage that is transferred to controller 120 by the CSN pin just may damage controller 120.
Therefore, need a kind of DC to DC converter with better inductor current sensing capability, the present invention's purport is provides this kind DC to DC converter.
Summary of the invention
One embodiment of the present of invention provide a kind of DC to DC converter that input voltage is transformed to output voltage.This DC to DC converter comprises a switch, an inductance, two voltage dividers, an electric capacity and a controller.Switch is connected to input voltage.Inductance contains a parasitic D.C. resistance and is used for switch is connected to the output node of DC to DC converter to generate output voltage at output node.First voltage divider is connected to output node to generate the branch pressure voltage of an output voltage.Second voltage divider is connected to switch and ground connection.Electric capacity is connected between first and second voltage dividers, can calculate the size of current of the inductance of flowing through by detecting the electric capacity both end voltage.Controller is connected to switch and controls its folding, makes input voltage power to inductance off and on.
Description of drawings
Like uses similar numeral number in the accompanying drawing, and with reference to the detailed description of respective drawings, characteristic and the advantage of the present invention's embodiment are apparent.
Fig. 1 detects the DC to DC converter of the current techniques of network for using the traditional electrical inducing current.
Fig. 2 is the DC to DC converter of use the present invention's embodiment, has improved inductive current and detects network.
Fig. 3 is a kind of scheme flow chart that DC input voitage is transformed to VD of use the present invention's embodiment.
Embodiment
Below will the present invention's embodiment be described in detail.It will be appreciated that though the description of this invention carries out in conjunction with the embodiments, the present invention is not limited to embodiment in this.On the contrary, in the present invention's that the appended claim book is defined spirit and invention scope, numerous variations, modification and equivalent can be arranged.
Relate to a large amount of details of design so that understand in below describing.Yet those skilled in the art will find that the present invention still can realize when not using this type of details.In addition, for showing the present invention's purport especially, the scheme of knowing, program, element and circuit will repeat no more.
Fig. 2 is for using the DC to DC converter that contains inductive current detection circuit 200 of the embodiment of the invention.DC to DC converter 200 is used for an input voltage is transformed to the output voltage of a preset value size to load 230 power supplies, it comprises switch 202 and 204, inductance 206, electric capacity 222, resistance 212,214,216 and 218, electric capacity 210 and controller 220.Switch 202 is connected to inductance 206 with the input voltage (Vin) of DC to DC converter 200.Switch 204 is connected to switch 202 and inductance 206. Switch 202 and 204 forms a switching circuit to receive input voltage and it is transformed to the output voltage of preset value size.In one embodiment of the invention, switch 202 and 204 is a N type MOS transistor.
Those skilled in the art obviously can understand, and switch 204 can be a diode in one embodiment of the invention.The negative electrode of this diode is connected to switch 202, plus earth.In this embodiment, diode will be opened so that a discharge path to be provided when switch 202 cuts out.In another embodiment of the present invention, switch 202 and 204 is a P type MOS transistor.
One end of inductance 206 is connected to switch 202, and the other end is connected to the output node of DC to DC converter 200.Electric capacity 222 1 ends are connected to the output node of DC to DC converter 200, other end ground connection.Inductance 206 and electric capacity 222 form the output that a low-pass filtering is come smooth direct current/DC converter 200.
First voltage divider comprises resistance 212 and 214, two resistance series connection, and voltage divider is connected to output to generate the branch pressure voltage of output voltage.Second voltage divider comprises resistance 216 and 218, two resistance series connection, and voltage divider is connected to the inductance 206 and first switch 202.Electric capacity 210 is connected between first voltage divider and second voltage divider, and the electric current of the feasible inductance 206 of flowing through can calculate by electric capacity 210, below will describe in detail.
In one embodiment of the invention, controller 220 is an integrated circuit (IC), comprises a HDR pin, a LDR pin, a CSP pin and a CSN/FB pin.The HDR pin of controller 220 is connected to switch 202 to control its conducting state.The average voltage of node will depend on the average ON time of switch 202 between switch 202 and the inductance 206.In one embodiment of the present of invention, a HDR pin transmission pulse-width modulation (PWM) signal that can be by controller 220 is aligned in the preset value size with the output voltage of DC to DC converter 200.The LDR pin of controller 220 is connected to switch 204, when switch 202 is not worked, and these pin control switch 204 work.Similar with it, can give switch 204 by pwm control signal of LDR pin transmission.
In one embodiment of the invention, use one first pwm signal to make switch 202 work or inefficacy, use one second pwm signal to make switch 204 work or inefficacy.First pwm signal and second pwm signal be reverse signal each other, and the two has an of short duration overlapping failure period, works simultaneously to avoid switch 202 and 204.
Among Fig. 2, the CSN/FB pin of controller 220 is connected to the node between resistance 212 and 214.Because resistance 212 and 214 forms first voltage divider and output voltage is connected to ground, the signal on the node between the resistance 212 and 214 is directly proportional with the output voltage of DC to DC converter 200, so can be used as the voltage feedback signal.Voltage signal Vref on the CSN/FB pin of controller 220 can calculate by following equation (2):
Vref＝Vout*R
214/(R
212+R
214)…………………………………(2)
Wherein Vout is the output voltage of DC to DC converter 200, R
212And R
214Be respectively the resistance of resistance 212 and 214.Like this, controller 220 can use a pin to realize two functions, and one is the pressure drop signal that obtains electric capacity 210, and another function is to obtain the dividing potential drop feedback signal.The number of pins of controller 220 is reduced.
In addition, switch 202 switching that between Kai Heguan, circulates, the DC input voitage intermittent action is in inductance 206.On the node between switch 202 and the inductance 206, generate a square-wave voltage.Electric capacity 210 is connected between first voltage divider (resistance 212 and 214) and second voltage divider ( resistance 216 and 218).In one embodiment of the invention, the resistance of resistance 216 is far longer than resistance 212, the resistance of resistance 218 is far longer than resistance 214, can reduce to minimum so that introduce the square-wave voltage of the CSN/FB pin of controller 220 like this, and makes that the signal that receives on the CSN/FB pin is stable as far as possible." be far longer than " and mean more than 100 times.In one embodiment of the invention, the resistance value ratio resistance 212 big hundred times of resistance 216, the resistance value ratio resistance 214 big hundred times of resistance 218.
As above state, electric capacity 210 is connected between first and second voltage dividers.The CSP pin of controller 220 and CSN/FB pin are connected to the two ends of electric capacity 210 respectively.The both end voltage of electric capacity 210 can be detected or be measured by controller 220.For detect and stream of measurements through the electric current of inductance 206, the time constant of inductance 206 and DCR resistance 208 must be mated with the time constant of resistance capacitance (RC) network.The inductance value of inductance 206 is L, and the resistance of resistance 208 is DCR, and then the time constant of inductance 206 should be L/DCR.RC network comprises resistance 212,214,216 and 218 and electric capacity 210, as shown in Figure 2.As above state, resistance 212 and 214 resistance are far smaller than the resistance of resistance 216 and 218 respectively.When calculating the time constant of RC network, resistance 212 and 214 resistance can be ignored.The time constant value of RC network can be calculated according to following equation (3):
T
RC＝R
216/R
218*C＝R
216*R
218/(R
216+R
218)*C……………………(3)
T wherein
RCBe the time constant of RC network, C is the capacitance of electric capacity 210, R
216And R
218Be respectively the resistance of resistance 216 and 218.When the time constant of RC network equals the time constant of inductance 206, i.e. T
RCEqual L/R
DCRThe time, the voltage at DCR resistance 208 two ends promptly equals electric capacity 210 both end voltage, and electric capacity 210 both end voltage can be detected by controller 220.Like this, the flow through size of current of inductance 206 is just mensurable or calculate.
In addition, those skilled in the art obviously understand, and resistance 212,214,216 and 218 resistance satisfy following equation (4):
R
218/(R
216+R
218)＝R
214/(R
212+R
214)………………………(4)
R wherein
212, R
214, R
216And R
218Be respectively the resistance of resistance 212,214,216 and 218.Like this, the dividing potential drop of first voltage divider and second voltage divider is in equal proportions.
Compare with the DC to DC converter 100 of Fig. 1, the voltage scale down on the CSN/FB pin of controller 220 is Vout/ (R1+R2) * R2, but not the original size of output voltage V out.That is to say, the voltage that the CSN/FB of controller 220 pin receives remain on one than low value in, the scope of output voltage can extend to high voltage.And the voltage that receives on the CSN/FB pin of controller 220 is directly proportional with the output voltage of DC to DC converter 200, can be with this voltage signal as the feedback voltage signal.The number of pins of controller 220 is reduced.
Need to prove that the spirit of the present invention can be used for the buck or boost DC to DC converter of any kind, and can be used for the supply convertor of other type.
Fig. 3 is for being transformed to DC input voitage a kind of scheme of the VD of preset value size.As shown in Figure 3, in the step 310, connect one first switch, and connect inductance to the first switch to export the VD of a preset value size at the output of inductance to DC input voitage.
In the step 312, first switch circulates between Kai Heguan and switches so that DC input voitage is transferred to inductance discontinuously.Connect an output capacitance to inductance to reduce the ripple voltage of output.Use a second switch with the first switch ground connection.When first switch was not worked or disconnected, second switch work or conducting were to provide discharge path.In one embodiment of the invention, use one first pwm signal to control first switch, use one second pwm signal control second switch, second pwm signal is the reverse signal of first pwm signal.The pulse duty factor of first pwm signal is variable, to adjust the average voltage of output voltage.
In the step 314, connect one first voltage divider between output and ground, first voltage divider comprises first and second resistance, the series connection of two resistance.Node between first and second resistance generates a voltage signal that is directly proportional with output end voltage as the feedback voltage signal.
In the step 316, connect one second voltage divider between inductance and ground, second voltage divider comprises third and fourth resistance, the series connection of two resistance.Between first and second voltage dividers, connect an electric capacity.One end of electric capacity is connected to first and second resistance, and the other end is connected to third and fourth resistance.Those skilled in the art obviously can understand, and the first and the 3rd resistance is far smaller than third and fourth resistance respectively.Third and fourth resistance is than the resistance value ratio that equals first and second resistance.When the time constant coupling of the time constant of inductance (wherein containing an intrinsic parasitic DCR resistance) and electric capacity and the 3rd and the 4th resistance or when equating, electric capacity both end voltage promptly equal the to flow through electric current of inductance multiply by the resistance of parasitic DCR resistance.Like this, the voltage at electric capacity two ends can detect, and as the current feedback signal.
In the step 318, give first pwm signal with further control first switch voltage feedback signal and current feedback signal feedback, the VD that makes output generate accurately remains on the preset value size.Those skilled in the art obviously understand, and can use a controller to receive voltage feedback signal and current feedback signal and control first and second switches.
More than describe and accompanying drawing only is the present invention's common embodiment, under the prerequisite of the spirit and scope that do not deviate from the principle of the present invention that the appended claim book defined, may exist and multiplely augment, revise and substitute.Those skilled in the art finds, does not deviate under the prerequisite of principle of the present invention, and according to concrete environment and operation requirement, the present invention can revise aspect many to some extent at form, structure, arrangement, ratio, material, key element, element and other.So at this open embodiment is illustrative only, and non-limiting, the present invention's scope is not limited to description before this, and is defined by appended claim and legal equivalents thereof.
Claims (19)
1. a DC to DC converter that is used for input voltage is transformed to the output voltage of preset value size on the output node is characterized in that, comprising:
First switch that is used to receive input voltage;
An inductance, this inductance is connected to the output node of DC to DC converter so that generate output voltage at output node with above-mentioned first switch;
One first voltage divider is connected to output node to generate branch pressure voltage;
One second voltage divider is connected between first voltage divider and the ground;
An electric capacity is connected between first and second voltage dividers, can learn the size of current of the above-mentioned inductance of flowing through by detecting this electric capacity both end voltage;
A controller is connected to above-mentioned first switch with the control switch folding, makes input voltage remain on the preset value size to above-mentioned inductance power supply and with output voltage off and on.
2. DC to DC converter according to claim 1 is characterized in that, described controller can receive the branch pressure voltage of output voltage, and this branch pressure voltage can be used as the feedback signal that described output voltage is given described controller.
3. as the DC to DC converter as described in the claim 2, it is characterized in that described controller can detect the voltage at described electric capacity two ends and learn the size of current of the described inductance of flowing through thus.
4. as the DC to DC converter as described in the claim 3, it is characterized in that described controller can generate a pwm signal and make described switch work or inefficacy.
5. DC to DC converter according to claim 1 is characterized in that, also comprise a second switch with first switch and inductance ground connection so that discharge path to be provided.
6. as the DC to DC converter as described in the claim 5, it is characterized in that, describedly be connected to described second switch and make second switch work or inefficacy.
7. as the DC to DC converter as described in the claim 6, it is characterized in that described controller can generate one second pwm signal with the work of control second switch.
8. DC to DC converter according to claim 1 is characterized in that, described first voltage divider also comprises:
One first resistance is connected to the output node of described DC to DC converter;
One second resistance is with first grounding through resistance.
9. DC to DC converter according to claim 1 is characterized in that, described second voltage divider comprises:
One the 3rd resistance is connected to first resistance, and its resistance is much larger than first resistance;
One the 4th resistance, with the 3rd grounding through resistance, its resistance is much larger than second resistance.
10. as the DC to DC converter as described in the claim 9, it is characterized in that described third and fourth electric resistance partial pressure is than the voltage ratio that equals first and second resistance.
11. DC to DC converter according to claim 1 is characterized in that, also comprises:
An output capacitance is connected to the output node of described DC to DC converter, to reduce the ripple voltage of output node.
12. the scheme of the VD of a preset value size that DC input voitage is transformed to output is characterized in that, may further comprise the steps:
Receive DC input voitage at first switch;
Control first switch and off and on input voltage is offered inductance to generate VD;
Be connected to voltage feedback signal of generation on first voltage divider of output, this voltage feedback signal is directly proportional with output end voltage;
Generate a current feedback signal on the electric capacity in the middle of first and second voltage dividers, described second voltage divider is connected to inductance, and the current feedback signal is directly proportional with the electric current of the inductance of flowing through;
Receive described voltage feedback signal and current feedback signal, make that adjusting VD in the step of described control first switch makes it remain on the preset value size.
13. the scheme as described in the claim 12 is characterized in that, and is further comprising the steps of:
Use an output capacitance that is connected to output to reduce the output ripple voltage.
14. the scheme as described in the claim 12 is characterized in that the step of described control first switch is further comprising the steps of:
Use a pwm signal to control described switch.
15. the scheme as described in the claim 12 is characterized in that, and is further comprising the steps of:
Use a second switch with the first switch ground connection, so that discharge path to be provided.
16. the scheme as described in the claim 12 is characterized in that the time constant of the time constant of described inductance and electric capacity and second voltage divider is complementary.
17. as the scheme as described in the claim 16, it is characterized in that, described first voltage divider comprises first resistance and one second resistance that are connected to output, this second resistance with first grounding through resistance so that the node between first and second resistance generates described voltage feedback signal.
18. as the scheme as described in the claim 17, it is characterized in that, described second voltage divider comprises the 3rd resistance and the 4th resistance with the 3rd grounding through resistance that are connected to inductance, described electric capacity is connected to the above-mentioned first, second, third and the 4th resistance, and described current feedback signal is this electric capacity both end voltage.
19. the scheme as described in the claim 18 is characterized in that the described third and fourth resistance ratio equals the first and second resistance ratios.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US72075405P | 2005-09-27 | 2005-09-27 | |
| US60/720,754 | 2005-09-27 | ||
| US11/524,862 | 2006-09-21 |
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| Publication Number | Publication Date |
|---|---|
| CN1941576A true CN1941576A (en) | 2007-04-04 |
| CN100477460C CN100477460C (en) | 2009-04-08 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNB2006101523276A Active CN100477460C (en) | 2005-09-27 | 2006-09-26 | DC/DC converter with inductor current sensing capability |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102495294A (en) * | 2011-11-30 | 2012-06-13 | 台达电子企业管理（上海）有限公司 | System and method for testing parasitic inductance |
| CN102967755A (en) * | 2011-09-01 | 2013-03-13 | 鸿富锦精密工业（深圳）有限公司 | Inductive current detecting circuit |
| CN103675404A (en) * | 2012-09-05 | 2014-03-26 | 快捷半导体(苏州)有限公司 | Method, device, and system for sensing and regulating inductor current in inductor |
-
2006
- 2006-09-26 CN CNB2006101523276A patent/CN100477460C/en active Active
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102967755A (en) * | 2011-09-01 | 2013-03-13 | 鸿富锦精密工业（深圳）有限公司 | Inductive current detecting circuit |
| CN102495294A (en) * | 2011-11-30 | 2012-06-13 | 台达电子企业管理（上海）有限公司 | System and method for testing parasitic inductance |
| CN102495294B (en) * | 2011-11-30 | 2014-11-26 | 台达电子企业管理（上海）有限公司 | System and method for testing parasitic inductance |
| CN103675404A (en) * | 2012-09-05 | 2014-03-26 | 快捷半导体(苏州)有限公司 | Method, device, and system for sensing and regulating inductor current in inductor |
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| Publication number | Publication date |
|---|---|
| CN100477460C (en) | 2009-04-08 |
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