CN101789687B - Average current mode controller based on inductance current self-calibration lossless detection - Google Patents

Abstract

The invention discloses an average current mode controller for inductive current self-calibration non-destructive detection, comprising an inductive DC converter, a power switch, a load connected in series with the average current mode controller, a driver, and a current loop with the function of inductive current self-calibration Control circuit, voltage loop control circuit, slope compensation circuit, duty ratio comparison circuit. The average current mode controller of the present invention has strong adaptability, and is suitable for any converter topology with inductance and various types and series of inductances. Application engineers do not need to measure the resistance value of the inductance in advance, and the resistance value within the calibrated range of the controller value can be applied. Using the controller of the present invention to control the average current does not introduce additional energy-consuming elements in the power stage, especially in the topology of high-power applications, the conversion efficiency is significantly improved. The controller of the present invention has many extended applications, and can calibrate and detect the on-resistance of the power switch.

Description

Average Current Mode Controller Based on Inductor Current Self-Calibration Nondestructive Detection

technical field

The invention relates to the field of power electronics, in particular to an average current mode controller for inductive current self-calibration non-destructive detection in an inductive converter.

Background technique

In inductive converters, basically most of the DC-DC or AC-DC converters need to detect the inductor current as: 1. Current loop control; 2. Overcurrent detection protection; 3. Reverse current detection, To achieve discontinuous current control mode (DCM). Among them, there are many methods for inductor current detection, and each has advantages and disadvantages. The following table lists several commonly used inductor current detection methods and their advantages and disadvantages:

Detection method advantage shortcoming Series resistance High precision High power consumption Switch on-resistance low power consumption low precision mirror switch Low power consumption, can be integrated Low accuracy, matching problems, low bandwidth Detect inductor voltage to calculate inductor current Low power consumption, full cycle detection Need to know the inductance value filter detection Low power consumption, full cycle detection It is necessary to know the inductance value and the resistance and capacitance of the ESR resistance filter are relatively large

Contents of the invention

The invention provides an average current mode controller for inductive current self-calibration and non-destructive detection, which uses the inherent series equivalent resistance (ESR) of the inductance to realize self-calibration of ESR resistors with different resistance values in an inductive DC-DC converter. And the non-destructive detection of the inductor current, and realize the average current control of the inductor current based on this current detection.

An average current mode controller for inductive current self-calibration non-destructive detection, comprising an inductive DC converter, a power switch and a load connected in series with the inductive DC converter, the average current mode controller also includes:

a driver, connected to the power switch, for controlling the closing of the power switch;

A current loop control circuit, connected to the input and output terminals of the inductive DC converter, is used to detect the current flowing through the inductor, and output a stable DC detection signal;

A voltage loop control circuit, connected to the output terminal of the inductive DC converter, for sampling the output voltage, and outputting a reference control signal for the current loop control circuit;

The slope compensation circuit is connected to the output terminal of the current loop control circuit, and is used to superimpose a slope signal to the DC detection signal output by the current loop control circuit;

The duty ratio calibration circuit receives the DC detection signal and the reference control signal output by the voltage loop control circuit, and is used to compare the two signals and output a duty ratio signal to control the operation of the driver.

Wherein, the current loop control circuit includes a low-pass filter, a variable resistor, a capacitor, a power voltage reference source and a low-pass filter DC gain self-calibration circuit, wherein:

The power voltage reference source is connected to the output terminal of the low-pass filter through a parallel variable resistor and capacitor, and is used to provide a DC bias signal for the output of the low-pass filter.

The low-pass filter DC gain self-calibration circuit is used to adjust the resistance of the variable resistor, thereby changing the DC gain of the low-pass filter.

Wherein, the voltage loop control circuit includes an error amplifier, several feedback divider resistors, a first voltage reference source, a compensation resistor and a compensation capacitor;

One input terminal of the error amplifier is connected to the output terminal of the converter through a feedback voltage dividing resistor, and the other input terminal is connected to the first voltage reference source for connecting the feedback signal with the reference voltage provided by the first voltage reference source Do error amplification;

The compensation resistor and the compensation capacitor are connected to the output terminal of the error amplifier, and are used to form an integral hysteresis frequency compensation network of the voltage loop control circuit.

Wherein, the low-pass filter DC gain self-calibration circuit includes a preamplifier, a comparator, a counter and a second voltage reference source;

A preamplifier, connected to the output of the low-pass filter, is used to amplify the detection signal output by the low-pass filter;

a comparator, connected to the output terminal of the preamplifier and the second voltage reference source, for comparing the amplified monitoring signal output by the preamplifier with the reference signal output by the second voltage reference source;

The counter receives the comparison signal output by the comparator, and is used for controlling the resistance value of the variable resistor according to the received comparison signal.

The average current mode controller of the present invention does not need to introduce an additional integrator in the design of the current loop, and there is no complicated compensation problem. In addition, the feedback stage of the current loop is a low-pass filter, and its transfer function has a left-half plane pole. When the current loop control circuit is closed, the pole in the feedback stage transfer function is decomposed into a left-half plane in the closed-loop transfer function Zeros and a high-frequency pole to help increase bandwidth and improve phase margin.

The average current mode controller of the present invention and the average current control method using the controller have the advantages of strong adaptability, applicable to any converter topology with inductance and various types and series of inductances, and application engineers do not need to measure in advance The resistance value of the inductor can be used within the calibrated range of the controller. Using this controller to control the average current does not introduce additional energy-consuming components in the power stage, especially in the topology of high-power applications, the conversion efficiency is significantly improved. The controller of the present invention has many extended applications, and can perform calibration and detection on the on-resistance of the power switch.

Description of drawings

Fig. 1 is the schematic diagram of circuit structure of the present invention;

Figure 2 is a waveform diagram of key signals when the circuit in Figure 1 is working;

Fig. 3 is a schematic structural diagram of the DC gain self-calibration circuit of the low-pass filter of the present invention;

FIG. 4 is a signal waveform diagram of each node in the circuit during the self-calibration process in FIG. 3 .

Detailed ways

Figure 1 is a schematic diagram of the inventive circuit structure, which is illustrated by a step-down buck topology, and other boost-type boost topologies, and the control of the buck-boost buck-boost topology is similar.

An average current mode controller for self-calibrating non-destructive sensing of inductor current comprising:

Inductive DC converter, where L is the inductance with an unknown ESR resistance, resistance R _o and capacitor C _o form the output load;

The power switch is composed of a P-channel power switch MP and an N-channel power switch MN, and controls the output voltage of the inductive DC converter;

The driver is connected to the power switch and controls the closing of the power switch;

Current loop control circuit, including low-pass first-order gm-c filter composed of transconductance operational amplifier gm, variable resistor R _S and capacitor C _S , power voltage reference source DC and low-pass filter DC gain self-calibration circuit, the input end of the low-pass filter is connected to both ends of the inductance L of the inductive DC converter, the current flowing through the inductance L is detected, and a stable DC detection signal V _S is output, and the power voltage reference source DC passes through the parallel variable resistor R _S and capacitor C _S are connected to the output of the low-pass filter. The DC gain self-calibration circuit of the low-pass filter is connected to the output of the low-pass filter, and controls the resistance value of the variable resistor R _S .

The voltage loop control circuit includes an error amplifier EA, two output voltage feedback divider resistors R1 and R2, a first voltage reference source, a compensation resistor R _C and a compensation capacitor C _C , and the voltage loop control circuit is connected to an input terminal of the error amplifier EA The feedback voltage divider resistors R1 and R2 sample to obtain the feedback signal V _FB , wherein the output feedback voltage divider resistors R1 and R2 are connected in parallel with the output load of the inductive DC converter, and the error amplifier EA is composed of the feedback signal V _FB and the reference voltage Do error amplification and output reference control signal V _C for the current loop control circuit.

The compensation resistor R _C and the compensation capacitor C _C are connected to the output terminal of the error amplifier EA to form an integral hysteresis frequency compensation network of the voltage loop control circuit.

The slope compensation circuit RAMP is a slope whose peak-to-peak value is V _M , is connected to the output terminal of the current loop control circuit, and a slope signal is superimposed on the DC detection signal output by the current loop control circuit to obtain a signal V _RAMP ;

The duty ratio comparison circuit PWM receives the signal V _RAMP superimposed on the ramp signal and the reference control signal V _C output by the voltage loop control circuit, compares the two signals and outputs a duty ratio signal to control the work of the driver. A duty ratio signal d is generated.

The low-pass filter in the current loop control circuit is a first-order gm-c filter, which is composed of a transconductance operational amplifier gm, a variable resistor R _S , and a capacitor C _S . Its transfer function is expressed as:

${\mathrm{<span\; class="notranslate">\; G</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; g</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

Among them, g _m is the transconductance value of the transconductance operational amplifier gm, _RS is the resistance value of the variable resistor _RS , _CS is the capacitance value of the capacitor _CS , and s represents a complex variable.

It can be seen from the formula (1) that when the transconductance of the operational amplifier is determined, the DC gain of the low-pass filter can be changed only by changing the resistance value of the variable resistor R _S . When the bandwidth of the low-pass filter is smaller than the operating frequency of the converter, its output signal can accurately represent the average value of the inductor current, and the detected average value of the inductor current V _S is:

$\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; g</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; ESR</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

R _ESR is the resistance value of the inductor ESR resistor, i _L is the current flowing through the inductor

When the current loop is closed, its closed-loop transfer function is:

$\mathrm{<span\; class="notranslate">\; Ai</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; IN</span>}}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; ESR</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; g</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; IN</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; \&CenterDot;</span>\frac{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}<span\; class="notranslate">\; )</span>}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{\mathrm{<span\; class="notranslate">\; L</span>}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; ESR</span>}}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}}{{\mathrm{<span\; class="notranslate">\; g</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; IN</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

V _IN is the input voltage of the converter, V _M is the peak-to-peak value of the slope, and L is the inductance value of the inductor.

It can be seen that its closed-loop transfer function has a low-frequency zero and two high-frequency poles, which help to improve the closed-loop amplitude-frequency characteristics.

The output signal of the current loop control circuit is superimposed with a slope V _RAMP and the reference control signal V _C . Comparing and generating a duty cycle signal d to control the work of the power switch. Due to the particularity of the current loop design, the current loop control circuit itself does not need compensation, and the voltage loop control circuit only needs simple compensation to achieve ideal amplitude-frequency characteristics. Here, a transconductance op amp is used to realize the frequency compensation of the integral type hysteresis.

Pay special attention to the power voltage reference source DC under the gm-c filter. Its function is to provide a suitable DC bias for the output of the filter, that is, the output signal of the filter is superimposed on this power voltage reference source. If the inductor current signal decreases and approaches zero, the output of the filter also decreases and approaches the DC reference value. This ensures that even at very low currents, the output of the filter is within a reasonable range and avoids saturation.

Figure 2 is a waveform diagram of key signals for the normal operation of the system loop. The inductor current I _L is a triangular wave, and the detection signal after passing through the low-pass filter is also a triangular wave, and its high-frequency gain is very small, so the reference control signal V _S can be approximately regarded as a DC signal. After superimposing a ramp, the signal V _RAMP is still a ramp signal. The voltage loop output signal V _C can also be regarded as a DC signal due to the influence of the integral type lagging frequency compensation network. After the V _RAMP and V _C signals pass through the PWM comparator, the duty ratio signal d can be obtained to control the work of the power switch.

Figure 3 is a working principle diagram of the current detection self-calibration circuit.

Wherein, the low-pass filter DC gain self-calibration circuit includes a preamplifier, a comparator, a counter and a second voltage reference source;

A preamplifier, connected to the output of the low-pass filter, amplifies the detection signal V _S output by the low-pass filter;

The comparator is connected to the output terminal of the preamplifier and the second voltage reference source, and compares the amplified monitoring signal V _COMP output by the preamplifier with the reference signal V _REF output by the second voltage reference source;

The counter receives the comparison signal output by the comparator, and is used to control the resistance value of the variable resistor R _S according to the received comparison signal.

The variable resistor R _S is composed of R _mini , R ₀ , 2×R ₀ , 4×R ₀ , 8×R ₀ , 16×R ₀ , 32×R ₀ , 64×R ₀ and 128×R ₀ in series Composition, each of R ₀ , 2×R ₀ , 4×R ₀ , 8×R ₀ , 16×R ₀ , 32×R ₀ , 64×R ₀ and 128×R ₀ is connected in parallel with a switch. The ESR resistance of general inductors ranges from tens of milliohms to several ohms. When 8 is used as the counter, the adjustable range of the variable resistor R _S in the current detection self-calibration circuit is R _mini < _RS <R _mini +255R ₀ . It is suitable for general applications. If the adjustment range needs to be increased, the number of counter bits can be increased. This method is easy to implement in an integrated circuit. In addition, the entire current detection self-calibration circuit can be integrated on-chip without adding additional devices outside the chip.

The working process of the current detection self-calibration circuit is to reasonably control the start-up process of the system, so that the current detection self-calibration circuit can complete the work before the current loop loop and the voltage loop loop start to work. Its working principle: when the system starts, the inductor and the power stage are disconnected, and a small DC detection current is injected, and the voltage at both ends of the inductor is detected by the gm-c filter to obtain V _S . Closed, the variable resistor R _S is set at the minimum resistance value, V _S passes through a preamplifier to get the V _COMP signal, and then inputs it to a comparator, and compares it with a reference signal V _REF , if the V _COMP signal is less than the V _REF signal , the output of the comparator triggers a counter to count one bit, and opens the switch S0 of the lowest bit, so that the resistance value of the variable resistor R _S increases by R ₀ , through this feedback, the DC gain of the gm-c filter also increases, Continue to do the above-mentioned comparison on the increased signal. After the comparison is carried out through the cycle, until the V _COMP signal approaches and exceeds the V _REF signal, the comparator output controls the counter to stop counting and maintain the count value. The current detection self-calibration process is completed, and then The current loop and the voltage loop power loop start to work normally.

Figure 4 is the signal waveform of each node in the circuit during the self-calibration process.

When the detection signal source is direct current, the voltage of each node is direct current within one cycle. When the counter is stopped, the following conclusions are drawn:

V _REF ＝K g _m R _S R _ESR I _S (4)

remember: $a=g_m\&Center\; Dot;R_S\&Center\; Dot;R_{\mathrm{ESR}}=\frac{V_{\mathrm{REF}}}{K\&Center\; Dot;I_S}---\left(5\right)$

Substitute into formula (2): V _S ＝a·i _L (6)

where K is the gain of the preamplifier.

From the analysis of equations (5) and (6), it can be seen that when the system parameters are determined, the value of a after self-calibration is a constant value, that is, the detection ratio of the current detection module is a constant ratio, which meets the needs of the control system design.

Claims (3)

1. the average-current mode controller of inductive current self calibration Non-Destructive Testing comprises inductive type DC converter, power switch and the load of connecting with the inductive type DC converter, and it is characterized in that: described average-current mode controller also comprises:

Driver connects described power switch, is used for the closure of power controlling switch;

The current loop control circuit; The input/output terminal that connects described inductive type DC converter; Be used to detect the electric current of inductance of flowing through, and export stable direct current detection signal, described current loop control circuit comprises low pass filter, variable resistor, capacitor; Power voltage a reference source and low pass filter DC current gain self-calibration circuit, wherein:

Described power voltage a reference source is passed through parallelly connected variable resistor is connected low pass filter with capacitor output, and the output that is used to described low pass filter provides the direct current biasing signal;

Described low pass filter DC current gain self-calibration circuit is used for variable-resistance resistance is regulated, thereby changes the DC current gain of low pass filter;

The Voltage loop control circuit connects the output of described inductive type DC converter, is used for output voltage is sampled, and is current loop control circuit output reference control signal;

Slope compensation circuit, the output of connection current loop control circuit is used for the ramp signal of direct current detection signal stack to the output of current loop control circuit;

The duty ratio comparison circuit receives the benchmark control signal that direct current detection signal and Voltage loop control circuit are exported, and is used for the work of two kinds of signals of comparison and the described driver of output duty cycle signal controlling.

2. average-current mode controller as claimed in claim 1 is characterized in that: described low pass filter DC current gain self-calibration circuit comprises preamplifier, comparator, the counter and second voltage-reference, wherein,

Described preamplifier connects the output of described low pass filter, is used for the detection signal of low pass filter output is amplified;

Described comparator connects the output and described second voltage-reference of described preamplifier, is used for the reference signal of detection signal after the amplification of preamplifier output and the output of second voltage-reference is compared;

Described counter receives the comparison signal that comparator is exported, and is used for controlling described variable-resistance resistance according to the comparison signal that receives.

3. average-current mode controller as claimed in claim 1 is characterized in that: described Voltage loop control circuit comprises error amplifier, some feedback divider resistances, first voltage-reference, compensating resistance and compensation condenser, wherein:

Described error amplifier one input is connected to converter output terminal through the feedback divider resistance, and another input connects first voltage-reference, is used for the reference voltage that feedback signal and described first voltage-reference provide is done the error amplification;

Described compensating resistance is connected the output of error amplifier with compensation condenser, be used to constitute the integral form hysteresis frequency compensation network of Voltage loop control circuit.

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