TWI404316B - Dc-dc converters having improved current sensing and related methods - Google Patents

Abstract

A DC-DC converter includes a chip including an error amplifier and a pulse width modulator (PWM) having an input connected to an output of the error amplifier, and an inductor driven by said PWM in series with an output node (VOUT) of the converter, wherein a load current flows through the inductor. VOUT is fed back through a network including a feedback resistor (RFB) to an inverting input of the error amplifier. A circuit for sensing the load current includes a first operational amplifier, a sense resistor on the chip having resistance RSENSE coupled to an inverting input of the first amplifier; wherein a sense current related to the load current flows through the sense resistor, a dependent current source provides an output current to supply the sense current. A reference resistor is disposed on the chip having a resistance RREFERENCE which is a fixed multiple of RSENSE. A set resistor is provided having a resistance RSET. Tracking circuitry sets a voltage across the reference resistor to be equal to a voltage across the set resistor. A function block is coupled to receive a current through the set resistor and a current through the reference resistor to find their ratio. A current multiplier is provided, wherein an output of the function block is coupled to the current multiplier. The current multiplier provides a measurement current which is proportional to the load current divided by RSET.

Description

DC to DC converter with improved current sensing and related methods [Related application cross-reference]

The present application claims the benefit of the method of the present application Serial No. 60/808,197, filed on May 24, 2006, which is incorporated herein by reference.

The present invention relates to accurate measurement of inductor current, particularly in voltage regulators and associated power supply circuits for controlling switching.

In order to achieve control of various devices, including current motors, DC to DC converter circuits, and voltage regulator circuits, the load current must be accurately measured. Figure 1 (a) is a known circuit 100 for measuring load current by an inductor current in a DC to DC converter. The right side of the vertical line of the circuit 100 between the pins I _{S E N S E} - and I _{S E N S E +} is typically inside the IC chip, and typically the portion outside the IC chip includes the inductor. The low pass filter of L 110 and C _{F I L T E R} (output capacitor) is the left side of the dashed line between I _{S E N S E -} and I _{S E N S E +} . The external inductor L 110 with DC resistance DCR and inductance L, and C _{F I L T E R} form part of a low-pass filter network, which is provided by a pulse width modulator (PWM, not shown) The pulse width modulation input signal is converted to a steady state voltage output V _{O U T} on the load R _{L O A D} . A portion of the voltage drop across L 110 is due to its DC resistance and is expressed in DCR. Resistor R _{I N D} series capacitor C _{I N D} , in parallel with inductor 110, the time constant provided by R _{I N D} /C _{I N D} closely matches the time constant of L/DCR.

Display (a) in FIG. 1, the voltage V _IND C _IND DCR corresponding to the voltage drop across, and thus the inductor current I _IND is a good indicator. The operational amplifier A1 in circuit 100 drives the gate of NMOS transistor Q1, the source of which is coupled back to the inverting input of A1 on pin I _SENSE+ . The sense resistor R _SENSE 120 is located between pin I _SENSE+ and V _OUT .

The A1 non-inverting input on pin I _SENSE- is connected to the junction between R _IND and C _IND . In this structure, a high gain A1 driving voltage I _{SENSE +} pin, making it equal to the voltage of pin I _SENSE-, so that the voltage on the capacitor V _IND C _IND will appear on R _SENSE. Therefore, Q1 will carry a current equivalent to V _IND /R _SENSE or I _IND *DCR/R _SENSE . This current I _{SENSE is available} on the drain of Q1 and can be processed accordingly and can be used for overcurrent trip or set regulation output impedance, among other uses.

Although Q1 is an NMOS transistor in FIG. 1, in another embodiment, it may be a combination of NMOS and PMOS, and the drain current together constitutes bidirectional current sensing. It can also be a single NMOS or PMOS, with a bias current applied to I _SENSE+ and reduced at I _OUT to provide bidirectional current sensing.

The R _SENSE resistor and the I _SENSE- pin can also be connected to the synchronous rectifier FET. In this case, the RDS _ON of the FET becomes the current sensing element instead of the inductor DCR. Figure 1 (b) illustrates that in circuit 140, when the PWM drives the synchronous rectifier, the load current is sensed by sampling the voltage across the lower MOSFET r _DS(ON) . The PWM 150 drives a gate driver 152 that drives the upper and lower NMOS FET's 156 and 157 (synchronous rectifiers) to sequentially drive the inductor 160. Amplifier A1 reaches the ground reference by connecting the ISEN-input to the source of MOSFET 157. The inductor current I _L flows from the Vin through the FET 156 when the FET 156 is turned on, and flows from the ground point when the lower FET 157 is turned on. The inductor current (I _L ) thus causes a voltage drop across the FET 157 that is equal to the product of the RDSon and inductor currents, which is related to the resistance of the sense resistor 170 multiplied by the sense current (I _{S E N} ). In particular, the resulting current flowing into the ISEN+ pin is proportional to the channel current I _L . As known in the art, the ISEN current is then sampled and maintained after a sufficient settling time. Sampling current can be used in applications including channel current balancing, line load regulation, and overcurrent protection.

R _{S E N S E} in circuits 100 and 140 are disposed off-wafer because R _{S E N S E} must be adjustable to combine the different DCRs and I _{I N D} in circuit 100 to obtain the desired I _{O U T} value. For example, I _{O U T is} compared with a fixed current value inside the integrated circuit (IC) to generate an overcurrent trip, and the inductor DCR and the desired I _{I N D} current trip point are based on system constraints. To set, then the R _{S E N S E} value must be adjusted to achieve the desired I _{O U T} at the desired I _{I N D} . Because of the need for adjustability, R _{S E N S E is} therefore usually arranged outside the IC, as shown in Figure 1. The second reason why R _{S E N S E} is usually placed outside the IC is that most integrated circuit processes do not support accurate and stable internal resistors.

Another problem with the external R _{S E N S E} is that as shown in Figures 1(a) and 1(b), when the noise is coupled through the parasitic capacitor 130, the I _{S E N S E +} pin is picked up by the noise. Sensitivity. Referring again to Figure 1(a), the noise current is capacitively coupled to the pin I _{S E N S E +} , presenting a Q1 drain current containing the noise component, labeled I _{O U T + N o} in Figure 1. _{i s e} . Such noise is known to have a negative impact on performance and requires a careful printed circuit board layout to reduce the capacitive coupling at the pin I _{S E N S E +} . It is generally not possible to properly bypass I _{S E N S E +} as this will add a pole to the feedback path of amplifier A1, which may make A1 unstable.

A DC to DC converter includes a chip including an error amplifier and a pulse width modulator (PWM) having an input coupled to an output of the error amplifier, and an inductor driven by the PWM, and an output of the converter A node (V _{O U T} ) is connected in series, wherein a load current flows through the inductor. V _{O U T is} fed back to the inverting input of the error amplifier through a network containing a feedback resistor (RFB). The circuit for sensing the load current includes a first operational amplifier, a sense resistor having a resistance R _{S E N S E} on the wafer, coupled to the inverting input of the first amplifier; wherein, related to the load current The sense current flows through the sense resistor, and the dependent current source provides an output current to supply the sense current. The reference resistor disposed on the wafer has a resistance R _{R E F E R E N C E} which is a fixed multiple of R _{S E N S E} . The set resistor provided has a resistance R _{S E T} . The tracking circuit adjusts the voltage across the reference resistor to be equal to the voltage across the set resistor. And combined with a function block to receive the current through the set resistor and the current through the reference resistor to find the ratio. A current multiplier is provided wherein the output of the functional block is coupled to the current multiplier. The current multiplier provides a measure of current proportional to the load current divided by R _{S E T} .

The present invention can utilize a variety of circuit combinations for sensing load current. In one embodiment, inductor DCR sensing is utilized, wherein the converter further includes a resistor in series with the capacitor and configured in parallel with the inductor, the time constant of which is designed to be in time with the inductor and its associated DC resistance (DCR) The constants match. In another embodiment, MOSFET r _{D S ( O N )} sensing is utilized, wherein the converter further includes a synchronous rectifier coupled between the PWM output and the inductor.

Preferably, the sensing resistor and the reference resistor should be made of the same material. In one embodiment, the converter includes a current mirror having an output coupled to the inverting input of the error amplifier, the input of which is used to sense the current, and the current mirror is configured to measure the current as a source current flowing through the RFB to The measured current is increased to increase the inverting input potential of the error amplifier to control the output impedance. In another embodiment, a structure for comparing the measured current to the fixed reference current is further included and a reset signal is generated for PWM for protecting the PWM under overcurrent conditions. In this embodiment, the comparator includes an inverter coupled to the reset pin of the converter, wherein the PWM is disabled if the measured current is greater than the reference current.

A current sensing method in a DC to DC converter, comprising the steps of providing a DC to DC converter chip, comprising an error amplifier coupled to a pulse width modulator (PWM), a driver and an output node of the converter (V) _{O U T} ) An inductor in series that is suitable for ground reference through a load through which the load current flows. V _{O U T is} fed back to the inverting input of the error amplifier through a network containing a feedback resistor (RFB). A circuit for sensing load current is included on the wafer and has a resistance (R _{S E N S E} ) sense resistor for generating a sense current associated with the load current. A dependent current source provides an output current (I _{O U T} ) to supply the sense current. The reference resistor disposed on the wafer has a resistance R _{R E F E R E N C E} which is a fixed multiple of R _{S E N S E} . A set resistor having a resistance R _{S E T} is provided while providing a tracking circuit for setting the voltage on the reference resistor to be equal to the voltage across the set resistor.

It is determined by setting the ratio of the current of the resistor to the current through the reference resistor. This ratio is then used to determine the measured current independent of the actual value of R _{S E N S E} , which is proportional to the load current divided by R _{S E T} .

A circuit for sensing load current executable inductor DCR sensing, in another embodiment, for sensing a load current circuit performs MOSFET r _{D S (O N)} sense.

The method further includes the step of using a measurement current to provide a fixed output impedance. In this embodiment, the step of using includes converting the measured current into a source current and flowing the source current through the feedback resistor to increase the voltage of the inverting input relative to V _{O U T} as the inductor current increases.

In another embodiment of the invention, the method further includes the step of using the measurement current to disable the PWM if the load current exceeds a predetermined amount to protect the PWM under overcurrent conditions. In this embodiment, the step of using includes comparing the measured current to a predetermined reference current, and disabling the power supply of the PWM if the measured current is greater than the reference current. In one embodiment, both the measurement current and the reference current are inputs to the inverter, and the output of the inverter is coupled to a reset pin of the regulator, wherein if the measurement current is greater than the reference current, then PWM is disabled.

2 shows a circuit having internal sense resistors for load current sensing in a DC to DC converter, or other switching regulator circuits that perform inductor DCR sensing, in accordance with an embodiment of the present invention. The circuit 200 includes the same circuit elements in the circuit 100 of FIG. 1(a), but adds an additional circuit 250 (shown within the dashed line) that includes a reference and tracking circuit that enables the inductor current through the inductor 110 to be independent of R. The actual value of _SENSE 120 is measured. Like circuit 100, circuit 200 includes a portion that is typically within the IC, and typically a portion external to the IC (inductors L110 and C _FILTER are typically external to the IC). However, unlike circuit 100 in Figure 1, R _SENSE is external to the IC.

Circuit 200 includes a current multiplier 215 in the I _OUT path to form an output current I _OUT2 , which is a multiple of I _OUT , which is equivalent to M*I _OUT . The circuit 200 configures a second resistor R _REFERENCE 220 inside the IC. R _REFERENCE 220 as arranged on the wafer 120 at a position close to the R _SENSE, and the ratio of the resistor R _SENSE to produce the same conductive material, you can have precise control of the R _SENSE 120 K. That is, R _REFERENCE = K*R _SENSE . K can be independent of process variation or temperature variation and can be any constant greater or less than one. Circuit 200 also includes an external resistor R _SET 235. The voltage of R _SET 235 on the high potential side is coupled to Vcc, while the low potential side of R _SET 235 is driven by any reference voltage. As shown in FIG. 2, any reference voltage of the R _SET 235 on the low potential side is set by an example circuit that includes a voltage source V1 coupled to the gate of the PMOS source tracker Q2.

As is known to those skilled in the art, the source and drain of the MOS transistor are interchangeable during operation of the transistor. Therefore, the terms 〝 source and 〝汲 〞 使用 使用 〞 〞 〞 〞 〞 〞 〞 NMOS NMOS NMOS NMOS NMOS NMOS NMOS NMOS NMOS NMOS NMOS NMOS NMOS NMOS NMOS NMOS NMOS NMOS NMOS NMOS NMOS NMOS NMOS NMOS NMOS NMOS NMOS NMOS NMOS NMOS NMOS NMOS drain, and functions to limit the current carrying electrodes is performed, the operational amplifier a ₂ 250 coupled with the PMOS Q3 255, R _REFERENCE 220 to drive the low potential side of the R _REFERENCE 220 R _SET 235 has the same voltage. The R _REFERENCE 220 can be driven by other circuits, such as the NPN/PNP synthesis tracker, but these methods may be excluded in some applications due to system accuracy requirements. The current of R _REFERENCE 220 and the current of R _SET 235 are fed to function block F ₁ 260. F ₁ can generate a multiplication factor M, which is equivalent to the ratio of R _SET current to R _REFERENCE current, by well-known analog or digital circuits. Since the current through the resistors having the same potential is proportional to the reciprocal of the respective resistance values, M is equal to R _REFERENCE /R _SET . Since R _REFERENCE is equal to K*R _SENSE , M=K*R _SENSE /R _SET .

As previously described with respect to circuit 100 in Figure 1, the output current I _OUT is equal to I _IND *DCR/R _SENSE . I _OUT2 =M* I _OUT =M*I _IND *DCR/R _SENSE . Substituting M for K*R _SENSE /R _SET gives: I _OUT2 =K* I _IND *DCR/R _SET (1)

It is worth noting that there is no R _SENSE term in equation (1), and I _OUT2 is only related to external circuit component values (L and R _SET , and L DC resistance (DCR)). Therefore, R _SENSE does not need to be precise. R _SENSE 120 only needs to have a fixed ratio K to R _REFERENCE 220. The fixed ratio is usually determined by the circuit design. Therefore, due to the resistance ratio, the variation of the resistivity of the conductive material used for R _SENSE and R _REFERENCE in the process (or temperature) does not affect the accuracy of the current measurement provided by the circuit 200.

The PMOS trackers (Q2 and Q3) drive R _SET 235 and R _REFERENCE 220, and R _SET and R _REFERENCE terminate at positive supply VCC. Although the PMOS tracker is depicted, the driver can be replaced by an NMOS or a bipolar transistor of either polarity, and the termination point can be ground or other power source. If implemented with an NMOS drive transistor, the reference voltage V1 driving the Q2 gate will change polarity and termination point as appropriate.

Although not depicted in FIG. 2, R _REFERENCE 220 can be driven by reference voltage V1 and tracker Q2, and R _SET can be driven in an active manner by A2 and Q3. This is generally undesirable because the parasitic capacitance at R _SET will create a pole on the feedback path of the A2 250, which may destabilize A2.

Circuitry 200 can be used to provide improved switching regulator circuitry that benefits from accurately measuring inductor currents, such as DC to DC converters, motor controller circuits, and the like.

Figures 3 and 4 show an example application of the induced current I _OUT2 for a pulse width modulated DC to DC converter. Figure 3 illustrates the output impedance of the control converter, while Figure 4 illustrates the protection of the PWM supply with an overcurrent trip action. However, it must be emphasized that the invention is not limited to use with pulse width modulated DC to DC converters, but can be used with other related components as well. Furthermore, as previously emphasized, a load current sensing circuit other than the inductor DCR as the sensing base circuit can also be used in the present invention. For example, a configuration in which MOSFET r _DS(ON) sensing is performed in FIG. 1(b) can also be used instead, wherein the sensing contacts (ISENSE- and ISENSE+) are connected to the source of the lower FET (which is grounded) and Its bungee jumping. Other suitable load current sensing circuits can also be used with the present invention.

Referring now to Figure 3, which is a diagram of an exemplary PWM DC to DC converter 300, including a circuit 310 for measuring inductor current in accordance with the present invention, an inductor 110 between _pins I _SENSE- and I _SENSE+ Together with the capacitor CF, the load RL constitutes a low pass filter. Converter 300 includes an error amplifier 350 that compares the applied reference voltage V _{R E F} with the regulated output voltage V _{O U T} . Through the resistor RFB, V _{O U T is} fed back to the inverting input of amplifier 350, node FB. Other compensating elements RC1 and CC1 are coupled between output node COMP of error amplifier 350 and node FB to provide an appropriate system response. The node COMP drives the pulse width modulator PWM 360 to provide a relationship between its COMP voltage input and the duty cycle output. The basic oscillator used to provide a clock signal (eg, sawtooth) to the input of the PWM 360 is not depicted here. The PWM output signal PWM _{O U T} is low-pass filtered by the inductor LF 110 and the capacitor CF to become the output voltage V _{O U T} . A typical requirement for a DC to DC converter is that the regulator has a specific output impedance. That is, V _{O U T} must be reduced at a fixed ratio relative to increasing the load current ILOAD to provide a fixed specific output impedance.

A circuit 310 for measuring the inductor current is used in the converter 300 of FIG. 3 to sense the current through the LF 110, which, as previously described, actually has the same average current as the current through the load RL. The circuit 310 for measuring current can be implemented by circuit 200, which includes R _{I N D} and C _{I N D} in parallel with LF 110, and R on the wafer between V _{O U T} and I _{S E N S E +} pin _{S E N S E} , and other example circuits are connected to the right side of the pins I _{S E N S E -} and I _{S E N S E +} , together with R _{S E T} are shown in circuit 200.

The current generated by circuit 310 for measuring the inductor current, I _{O U T 2} , is added using the current mirror 330 with the appropriate polarity. The output of current mirror 330 is the source current, represented by I _{O U T 2} , which flows through RFB, thus increasing the voltage of node FB relative to V _{O U T} as ILOAD increases. The error amplifier 350 then pulls down the V _{O U T} voltage, maintaining the node FB equal to V _{R E F} , in this way providing the desired fixed output impedance.

4 is a second exemplary application of an inductor current sensing circuit in accordance with the present invention. 4 shows an example PWM DC to DC converter 400 comprising a circuit 310 for measuring inductor current in accordance with the present invention that protects the PWM supply with an overcurrent trip action. As described in FIG. 3, the circuit 310 for measuring current can be implemented with the example measurement circuit of FIG.

When the circuit is in operation, if the load current ILOAD rises above a predetermined current level, the circuit 310 for measuring the inductor current in accordance with the present invention will disable the power supply to the PWM 360. In an embodiment, inverter 435 is coupled to the reset pin of PWM 360. I _{O U T 2 is} compared to the fixed reference current I _{R E F provided} . When the converter is in normal operation, the reset pin must be high. If I _{O U T 2 is} greater than I _{R E F} , the input of inverter 435 is pulled down, causing the inverter to rise and send the reset signal to PWM 360. The PWM 360 is disabled to protect the PWM 360 under overcurrent conditions.

The present invention provides several significant advantages. The first advantage is that R _{S E N S E} is on the wafer such that the inverting input to A1 becomes an internal node and thus is not capacitively coupled to the noise. The I _{S E N S E +} and I _{S E N S E -} nodes in circuit 200 are low impedance and therefore insensitive to noise pickup. Another advantage is the input from the external resistor R _{S E T} , which can be DC or low frequency, since it does not affect the bandwidth from the I _{S E N S E} to the I _{O U T 2} path. Therefore, R _{S E T} can be bypassed to prevent noise pickup.

A further advantage is that R _{S E T} can be used to control several channels of I _{S E N S E} to I _{O U T 2} . This approach saves components compared to using a separate external R _{S E T for} each channel. Another advantage is that the thermistor can be used to vary the R _{S E T} value depending on the temperature, and the I _{O U T 2} gain is adjusted to match the temperature coefficient of the inductor DCR. A positive temperature coefficient thermistor (PTC) or PTC-resistor network can be used to replace R _{S E T} . The PTC or PTC-resistor network can optionally have the same temperature coefficient as the inductor's DCR, which creates thermal tracking of the inductor. When the inductor and its DCR value rise with temperature, the resistance of the PTC or PTC-resistor network also rises, reducing the multiplication gain of the inductive circuit, so that the induced current has a fixed ratio to the actual inductor current. The thermistor can be bypassed close to the IC to avoid noise pickup.

It is to be understood that the invention has been shown Other aspects, advantages, and modifications in the scope of the invention will be apparent to those skilled in the art.

100‧‧‧ circuits

110‧‧‧Inductors

120‧‧‧Sensor resistance

130‧‧‧Parasitic capacitors

140‧‧‧ Circuitry

150‧‧‧ Pulse width modulator

152‧‧‧ gate driver

156‧‧‧NMOS FET

157‧‧‧NMOS FET

160‧‧‧Inductors

170‧‧‧Sensor Resistors

200‧‧‧ circuit

220‧‧‧second resistor

215‧‧‧current multiplier

235‧‧‧External resistance

250‧‧‧Operational Amplifier

255‧‧‧ PMOS

260‧‧‧Compute multiplier

300‧‧‧ converter

310‧‧‧Circuit for measuring inductor current

330‧‧‧current mirror

350‧‧‧Error amplifier

360‧‧‧ Pulse width modulator

400‧‧‧ converter

435‧‧‧Inverter

The invention, its features and advantages are more fully understood from the detailed description and drawings.

Figure 1 (a) shows a known load current sensing that performs inductor DCR sensing in a DC to DC converter.

FIG 1 (b) shows the DC-DC converter, when the PWM driving synchronous rectifier, perform a r _{D S (O N)} known in the sensed load current sensing circuit.

2 shows a circuit having an internal sense resistor for measuring inductor current in a DC to DC converter, in accordance with an embodiment of the present invention.

3 shows an example diagram of a DC to DC converter including a circuit for measuring load current using an inductor DCR sensing, which is used to control the output impedance of the converter, in accordance with another embodiment of the present invention.

4 shows an exemplary diagram of a DC to DC converter including a circuit for measuring load current again using an inductor DCR induction, in accordance with another embodiment of the present invention, for overcurrent tripping, Protect the PWM supply of the converter.

110‧‧‧Inductors

120‧‧‧Sensor resistance

200‧‧‧ circuit

215‧‧‧current multiplier

220‧‧‧second resistor

235‧‧‧External resistance

250‧‧‧Operational Amplifier

255‧‧‧ PMOS

260‧‧‧Compute multiplier

Claims (35)

A power converter comprising: an error amplifier configured to compare a reference voltage with a regulated output voltage; a pulse width modulator (PWM) having an input coupled to an output of the error amplifier and configured to be based on the error Comparing the amplifier to modify the adjusted output voltage; a current sensing component coupled to the pulse width modulator and configured to sense a first current; a set resistor having a resistance R _SET ; a circuit coupled to the current sensing component and the set resistor, wherein the integrated circuit includes: a sensing resistor having a resistor R _SENSE coupled to one of the input of the integrated circuit Passing a second current about the first sensed current through the sense resistor; a dependent current source coupled to the sense resistor and configured to provide a first output current; a reference resistor having a a resistor R _REFERENCE , which is a fixed multiple of the R _SENSE ; and a circuit configured to generate a second output current such that the second output current value is proportional to R _SFT and between R _SRNSE and R _{REF a} fixed ratio of one of the _ERENCEs ; wherein the circuit in the integrated circuit includes: a tracking circuit configured to drive the reference resistor such that a voltage system across the reference resistor is substantially equal to a voltage across the set resistor a function block configured to determine a second ratio of current through one of the current through the set resistor; and a current multiplier coupled to the functional block and one of the dependent current sources The current multiplier is configured to combine the first output current with the second ratio to generate the second output current. A power converter as claimed in claim 1, wherein the current sensing element comprises an inductor to perform inductor DC resistance (DCR) sensing. The power converter of claim 1, wherein the current sensing element further comprises a metal oxide semiconductor field effect transistor (MOSFET) to perform r _{DS (ON)} sensing. The power converter of claim 1, wherein the sensing resistor and the reference resistor are composed of the same conductive material. The power converter of claim 1, further comprising a current mirror coupled between the output of the integrated circuit and one of the input of the error amplifier, wherein the current mirror increases the error based on the output current The voltage at the input of the amplifier causes the power converter to provide a fixed output impedance. The power converter of claim 1, further comprising an inverter, wherein one of the inverter outputs is coupled to one of the pulse width modulator reset pins, wherein the output current is greater than A reference current then the inverter transmits a reset signal to the PWM. The power converter of claim 1, wherein the tracking circuit comprises: The source follower is coupled to one of the low potential sides of the reference resistor; and the operational amplifier has an output coupled to one of the gates of the source follower. The power converter of claim 1, wherein the set resistor is a thermistor. A method for measuring a load current, the method comprising: generating a first output current related to the load current from a first current via a first resistor, the first resistor having a first resistance; a current through a second resistor to a ratio of current through a third resistor, the second resistor coupled to the integrated circuit and having a second resistor, wherein the third resistor is located And having a third resistor in the integrated circuit, which is a fixed multiple of the first resistor; combining the first output current with the determined ratio to generate a second output current indicating the load current, which is independent of the a first resistor; and outputting the second output current. The method of claim 9, further comprising setting, by a tracking circuit, the voltage across the third resistor to be substantially equal to the voltage across the second resistor. The method of claim 9, further comprising modifying the second resistor with a thermistor to adjust a gain of the second measurement current. A device for measuring a load current, the device comprising: an integrated circuit coupled to an external circuit component and a resistor having a resistor R _SET , wherein the integrated circuit comprises: a sensing resistor, Having a resistor R _SENSE coupled to one of the input terminals of the integrated circuit such that a first current flows through the sense resistor via one of the current circuit components; the reference resistor has a a resistor R _REFERENCE , which is a fixed multiple of R _SENSE ; and a circuit configured to generate a current indicative of one of the load currents such that the measured current value is proportional to R _SET and a phase between R _SENSE and R _REFERENCE Fixed ratio. The device of claim 12, wherein the external circuit component comprises an inductor to perform inductor DC resistance (DCR) sensing. The device of claim 12, wherein the circuit in the integrated circuit includes a tracking circuit configured to drive the reference resistor such that the voltage across the reference resistor is substantially equal to across the set resistor This voltage. The device of claim 14, wherein the tracking circuit comprises: a source follower coupled to one of the low potential sides of the reference resistor; and an operational amplifier having an output coupled to the source follower A gate. The device of claim 12, wherein the set resistor is a thermistor. The device of claim 12, wherein the reference resistor and the sense resistor are comprised of the same electrically conductive material. The device of claim 12, wherein the external circuit component comprises a metal oxide semiconductor field effect transistor (MOSFET) to perform r _{DS (ON)} sensing. The device of claim of 12 patentable scope, wherein the circuit lines of the integrated circuit are arranged to determine, via a proportional current R _REFERENCE of and binding to the current of the current R _SET of via the current R _SET of the through via R _REFERENCE of The ratio is coupled to a first output current to produce the measured current. An integrated circuit includes: a first input configuration coupled to a current sensing element; a second input configuration coupled to a one of a first resistor setting resistor; a sensing resistor having a second resistor The sensing resistor is coupled to the first input such that a voltage is placed across the sensing resistor to generate a first output current based on the second resistor; the reference resistor has a third resistor, The third resistor is a fixed multiple of the second resistor; and the current multiplier is configured to generate a second output current by combining the first output current, which is indicative of a load current and is independent of the second resistor, There is a ratio of the current at the second input to the current through the reference resistor. The integrated circuit of claim 20, further comprising: a transistor having a gate, a source and a drain; and an operational amplifier having an input coupled to the sense resistor and a The output is coupled to the gate of the transistor; wherein the drain of the transistor is coupled to the current multiplier to provide the first measured current to the current multiplier. The integrated circuit of claim 20, further comprising a tracking circuit configured to drive the reference resistor such that a voltage across the reference resistor is substantially equal to a voltage across the set resistor; wherein the tracking The circuit includes a source follower coupled to one of the low potential sides of the reference resistor, and an operational amplifier having an output coupled to one of the gates of the source follower. a power converter having a plurality of channels, the power converter comprising: a set resistor having a resistor R _SET ; and each of the plurality of channels includes: an error amplifier configured to compare a reference voltage with an adjusted output a voltage; a pulse width modulator coupled to the error amplifier and configured to modify the adjusted output voltage based on the comparison at the error amplifier; and a current sensing element coupled to the pulse width modulator and Configuring to sense a first current; the sensing resistor has a resistor R _SENSE coupled to the current sensing element such that the first sensed current flows through the sensing resistor; a resistor having a resistance R _REFERENCE which is a fixed multiple of R _SENSE ; and a circuit coupled to the set resistor, the reference resistor, and the sense resistor, the circuit configured to generate an output current having a proportional ratio a value of R _SET and a fixed ratio between R _SENSE and R _REFERENCE , wherein the circuit is coupled to the error amplifier to provide the output current to the error amplifier . A power converter as claimed in claim 23, wherein, for each of the plurality of channels, the circuit includes a tracking circuit configuration to drive the reference resistor such that the voltage system across the reference resistor is substantially equal to This voltage across the set resistor. A power converter as claimed in claim 24, wherein, for each of the plurality of channels, the circuit is configured to determine a ratio of current through R _SET to current through the individual R _REFERENCE and in combination The ratio is determined by a first measured current to produce the output current. The power converter of claim 23, wherein the set resistor comprises a plurality of resistors including one or more thermistors. The power converter of claim 23, wherein the reference resistor and the sense resistor are composed of the same type of material. The power converter of claim 23, further comprising an inverter coupled to the reset pin of the pulse width modulator, wherein if the output current of the individual channel is greater than a reference Current, the inverter transmits a reset signal to the pulse width modulator. The power converter of claim 23, further comprising: for each of the plurality of channels, a current mirror coupled to the integrated body Between the output of the circuit and one of the inputs of the error amplifier, wherein the current mirror increases the voltage at the input of the error amplifier based on the output current such that the power converter provides a fixed output impedance. A device for measuring a load current of each of a plurality of channels, the device comprising: a set resistor having a resistor R _SET ; and an integrated circuit coupled to the set resistor; wherein Each of the plurality of channels, the integrated circuit includes: a sensing resistor having a resistor R _SENSE coupled to one of the other current sensing elements such that the other first sensed a current flowing from the current sensing element through the sense resistor; a reference resistor having a fixed ratio of a resistor R _{REFERENCE of} the system R _SENSE ; and coupled to the set resistor, the reference resistor, and the sensing A circuit of a resistor configured to generate an output current having a proportional ratio to one of R _SET and a fixed ratio of one of R _SENSE and R _REFERENCE . The device of claim 30, wherein, for each of the plurality of channels, the circuit in the integrated circuit includes a tracking circuit configured to drive the reference resistor such that the reference resistor is crossed The voltage system is substantially equal to the voltage across the set resistor. The device of claim 31, wherein, for each of the plurality of channels, the circuit in the integrated circuit is configured to determine a ratio of current through the R _{SET to} the current through the R _REFERENCE , and The ratio of the current through the R _REFERENCE is combined with a current through R _SET to a first measured current to produce the output current. The device of claim 30, wherein, for each of the plurality of channels, the sensing resistor is coupled to a current sensing element comprising a metal oxide semiconductor field effect transistor (MOSFET) To implement r _{DS (ON)} sensing. A method of measuring load current for one of the plurality of channels, the method comprising: for each of the plurality of channels: receiving an additional sensed current; via having one of the first resistors Passing the sensed current through the individual first resistor; generating a different first measured current from the individual sensed current based on the first resistance; indicating the load current; setting across another second resistor One of the voltages is substantially equal to one voltage across a third resistor, the third resistor has a third resistance, wherein the same third resistor is used for each of the plurality of channels; a ratio of the current of the individual second resistors to the current through the third resistor, wherein each of the individual second resistors has a second resistance that is a fixed multiple of one of the individual first resistors; Individual first measurement currents and the determined ratio to generate a second second measurement current representing the load current, the individual second measurement currents being independent of the individual first resistance; The respective second measurement current. The method of claim 34, further comprising modifying the individual second resistor to adjust a gain of the individual second measurement current.