JP2005229744A - Slope building out circuit, switching regulator, and electronic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To generate a nonlinear slope through simple circuitry. <P>SOLUTION: A slope building out circuit generates slope voltage for use in operational stability control on a peak current controlled PWM switching regulator. The slope building out circuit is so constituted that the following is implemented: a linear slope voltage is generated by a capacitor C2 of a slope generation circuit 1a with variable current circuit; the linear slope voltage generated by the capacitor C2 is nonlinearly varied by linearly varying the gate voltage of a transistor M3 of the slope generation circuit 1a with variable current circuit, and utilizing the characteristics of the transistor M3 in saturation region; thus, a nonlinear slope voltage is generated and output. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a switching regulator circuit used in various electronic devices such as a computer device and a cellular phone, and in particular, stable in a peak current control type PWM (Pulse Width Modulation) pulse converter using a slope compensation circuit. The present invention relates to a technique suitable for efficiently obtaining an operation.

  Switching regulators for supplying stable power are used in various electronic devices such as computer devices and mobile phones. In general, in a peak current control type switching regulator, it is known that when the duty exceeds 50%, an oscillation phenomenon occurs due to a current variation from a steady state. Therefore, it is necessary to provide a slope compensation circuit that performs a stable operation by superimposing a stabilizing saw wave.

  FIG. 3 shows a block diagram of a peak current control type switching regulator. The circuit operation of this peak current control type switching regulator is as follows. The voltage detection voltage based on the output voltage of the amplifier circuit 3 that amplifies the difference between the voltage Vfb obtained by dividing the output voltage Vout by the resistors R1 and R2 and the reference voltage 5, and the adder 2 detects the voltage detection voltage with a power switch with a current sensor. The comparator 4 compares the current detection voltage obtained by adding the slope compensation signal from the slope compensation circuit 1 to the peak current detection signal, and the control circuit 6 based on the comparison result output signal of the comparator 4 and the output signal from the oscillation circuit 7. The output voltage is stabilized by varying the ratio of the on / off period of the power switch 8 with the current sensor by controlling the current.

  FIG. 17 shows the relationship between the sawtooth waveform for slope compensation and the coil current waveform of the switching regulator in the step-down switching regulator. Here, as an example of an appropriate slope signal ma, it is known that the value is “−Vout / 2L” given by the output voltage Vout and the inductance L of the coil coil (Texas instruments application note U-111).

  However, since the appropriate slope value varies depending on the output voltage Vout, it is necessary to optimize the slope according to the set voltage. That is, a linear slope signal waveform as shown in FIG. 17 cannot compensate for stable operation when the output voltage Vout changes.

  As a conventional technique for dealing with such a problem, there is a technique described in Patent Document 1, for example. In this technique, a circuit for generating a non-linear slope waveform has been proposed. However, in this technique, since the slope compensation signal is generated using the composite logic, the digital-analog converter, and the synthesizer, the circuit scale increases.

JP 2000-201447 A

  The problem to be solved is that the conventional technique cannot generate a non-linear slope waveform with a small circuit scale.

  The object of the present invention is to generate a non-linear slope with a simple circuit configuration, to set the slope addition at an arbitrary position (for example, Duty 50% or more), and to mix with a linear slope. Further, it is possible to prevent a change in slope due to process variations and a change in slope due to a temperature change.

  In order to achieve the above object, in the present invention, in order to obtain a stable operation in a peak current control type PWM switching regulator, a non-linear slope voltage is generated using characteristics of a saturation region of a transistor. For example, a non-linear slope voltage is generated by linearly changing the gate voltage of a transistor connected to a capacitor that generates a slope voltage using a constant current and a capacitor. Further, for example, a slope is generated after a delay time generated by a constant current inverter and a capacitor. Furthermore, a linear slope voltage and a non-linear slope voltage are output in combination, and, for example, a linear configuration up to a certain delay time and a non-linear configuration after the delay time. That is, the gate voltage is constant until the delay time and linearly changes after the delay time. Alternatively, the gate voltage is linearly changed until the delay time, and is constant after the delay time, so that the gate voltage is non-linear up to a certain delay time and linear after the delay time.

  According to the present invention, a non-linear slope can be generated with a simple circuit configuration, and by adding a certain delay time, the non-linear slope can be set at an arbitrary position (for example, duty 50% or more) and linear. A slope can be mixed, and a slope change due to process variations and a slope change due to a temperature change can be prevented, and a stable operation can be obtained in a peak current control type PWM converter.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a block diagram showing a first configuration example of the slope compensation circuit according to the present invention, FIG. 2 is a circuit diagram showing a detailed configuration example of the slope compensation circuit in FIG. 1, and FIG. 4 is a block diagram showing a configuration example of a peak current control type switching regulator provided with the slope compensation circuit, FIG. 4 is an explanatory diagram showing the temperature characteristic calculation result of the slope compensation circuit in FIG. 1, and FIG. 5 is the slope compensation in FIG. It is explanatory drawing which shows the example of control operation | movement of the peak current control type switching regulator which provided the circuit.

  The current control type switching regulator shown in FIG. 3 is a step-down type, and the amplifier circuit 3 amplifies the difference between the voltage Vfb obtained by dividing the output voltage Vout by the resistors R1 and R2 and the reference voltage 5.

  Further, in the adder 2, the slope compensation signal from the slope compensation circuit 1 is added to the peak current detection signal detected by the power switch with the current sensor, and this added current detection voltage and the voltage by the output voltage of the amplifier circuit 3 are added. The comparator 4 compares the detected voltage.

  Then, the ratio of the on / off period of the power switch 8 with the current sensor is varied by the control of the control circuit 6 based on the comparison result output signal of the comparator 4 and the output signal of the oscillation circuit 7 to stabilize the output voltage. .

  In this example, the slope compensation circuit 1 has the configuration shown in FIGS. 1 and 2 and generates a non-linear slope voltage. In order to generate such a nonlinear slope voltage, the slope compensation circuit 1 shown in FIGS. 1 and 2 includes a slope generation circuit 1a with a variable current circuit, a variable current control circuit 1b, and an initial variable current setting circuit 1c. Have. These circuits are controlled by the power switch control signal 1d.

  As shown in detail in FIG. 2, each of the slope generating circuit 1a with variable current circuit, the variable current control circuit 1b, and the initial variable current setting circuit 1c includes transistors M1 and M3 used as current mirrors. By changing the gate voltage linearly, the current value is changed secondarily, and a corresponding slope voltage (nonlinear slope voltage) is created.

  Hereinafter, individual operations will be described. First, the initial variable voltage setting circuit 1c determines the initial gate voltage VGS0 of the transistor M1 that is saturated with the constant current value I1 set in advance. Here, the current I1 flowing through the transistor M1 is determined by “I1 = Kn / 2 * (VGS0−Vthn) ^ 2.” In this equation, “Kn” represents the NMOS conductivity coefficient, and “Vthn” represents the threshold voltage.

  Since the transistors M1 and M3 are current mirror circuits, the initial variable current setting value from the initial variable current circuit setting circuit 1c to the slope generating circuit with variable current circuit 1a is determined by “VGS0”.

  Next, in the variable current control circuit 1b, after the switching transistor M4 is turned off, the voltage VGS applied to the transistor M3 is determined by a constant determined by the initially set gate voltage VGS0, constant current I2, and capacitor C1. “VGS = VGS0 + I2 / C1 × t” is given. Here, “t” corresponds to the duty ON time Ton.

  In the slope generating circuit 1a with a variable current circuit, the slope to be generated is determined, and the variable current value I3 at that time is defined as “I3 = Kn / 2 × (VGS−), assuming that Kn and Vthn of the transistors M1 and M3 are equal. Vthn) ^ 2 = Kn / 2 * (VGS0 + I2 / C1 * t-Vthn) ^ 2 = Kn / 2 * (√ (2I1 / Kn) + I2 / C1 * t) ^ 2 ".

  In this formula 1, there is no term of the threshold voltage “Vth”, and it can be seen that the variable current value does not depend on the threshold voltage Vth. As a result, it is possible to supply a current that is stable with respect to process variations and that changes secondarily (non-linearly) with Duty (ON time).

  In general, in the step-down switching regulator, the ON duty in the continuous mode is given by “Vout / Vin”. Further, if the input voltage Vin is constant, the slope waveform for obtaining stabilization needs to be increased in proportion to the output voltage Vout.

  In other words, the increase in the slope of the slope due to the increase in the output voltage Vout is proportional to the increase in the ON time, and the change in the slope can be satisfied by making a secondary change in the waveform. The slope current that changes to is effective to obtain stabilization even when the output voltage Vout changes.

  Further, from Equation 1, by selecting an appropriate size in consideration of a temperature characteristic of Kn determined by a transistor, a temperature characteristic of constant currents I1 and I2, and a change in on-time t due to a frequency change, a variable current without a temperature change is selected. It is possible to create a source.

  FIG. 4 shows the calculation result as an example when an optimized transistor is selected. Here, the transistors M1 and M3 have a current mirror configuration that satisfies “I1 = I2”, and “I3” is a current value in Duty at 90%. As is apparent from this, it is possible to create a slope current source with good temperature characteristics.

  The operation state of this configuration is shown in FIG. In the slope compensation circuit of this example, it can be seen that the slope of the slope can be adjusted even when the set voltage rises by adding the stabilization slope signal to the control current and the duty becomes wide. This is important in ensuring stability as described above. The power switch control signal (1d) turns on the power switch when outputting Low.

  FIG. 6 is a block diagram showing a second configuration example of the slope compensation circuit according to the present invention, and FIG. 7 is a circuit diagram showing a detailed configuration example of the slope compensation circuit in FIG.

  The slope compensation circuit 61 shown in FIGS. 6 and 7 has a configuration in which a delay circuit 61e is provided in the slope compensation circuit 1 shown in FIGS. With such a configuration, in the slope compensation circuit 61 of this example, after the signal is output from the initial variable current setting circuit 61c, the delay signal from the delay circuit 61e is sent to the slope generation circuit 61a with variable current circuit and the variable current control circuit 61b, respectively. , The time for starting the current addition can be arbitrarily determined. That is, adding a slope from an arbitrary duty can be realized by setting the delay time to an appropriate value.

  As shown in FIG. 7, the delay circuit 61e has a delay time determined by the current value I4 of the inverter with constant current, the value of the capacitor C3, and the threshold value of the transistor M2 in the variable current control circuit 61b. By turning on, the gate voltage of the transistor M3 in the slope generating circuit 61a with variable current circuit starts to change linearly. Here, by adjusting the threshold value of the inverter connected to the transistor M3 and the threshold value of the transistor M2 to the same extent, a nonlinear slope can be generated as a result after the delay time.

  FIG. 8 is a block diagram showing a third configuration example of the slope compensation circuit according to the present invention, and FIG. 9 is a circuit diagram showing a detailed configuration example of the slope compensation circuit in FIG.

  The slope compensation circuit 81 shown in FIGS. 8 and 9 is provided with a delay circuit 81e in the slope compensation circuit 1 shown in FIGS. 1 and 2, similar to the slope compensation circuit 61 shown in FIGS. The signal from the circuit 81e is input only to the variable current control circuit 81b.

  With the configuration shown in FIG. 9, the slope compensation circuit 81 of this example uses the gate signal provided by the transistor M1 in the initialization variable current setting circuit 81c until the delay time generated by the delay circuit 81e, and the slope with the variable current circuit. The current value of the transistor M3 in the generation circuit 81a is determined, and a linear slope is created by discharging the capacitor C2 in the slope generation circuit 81a with variable current circuit with a constant current.

  Then, after a delay time determined by the delay circuit 81e, the transistor M2 in the variable current control circuit 81b is turned on, and the variable current control circuit 81b operates to linearly change the gate voltage of the transistor M3 in the slope generation circuit 81a with variable current circuit. By changing to, the current I3 changes and a non-linear slope can be created.

  FIG. 10 is a block diagram showing a fourth configuration example of the slope compensation circuit according to the present invention, and FIG. 11 is a circuit diagram showing a detailed configuration example of the slope compensation circuit in FIG.

  The slope compensation circuit 101 shown in FIGS. 10 and 11 is provided with a control circuit 101e with delay in the slope compensation circuit 1 shown in FIGS. 1 and 2, and the signal of the control circuit 101e with delay is sent to the variable current control circuit 101b. Is configured to input.

  With the configuration shown in FIG. 11, the slope compensation circuit 101 of this example linearly changes the gate voltage of the transistor M2 in the variable current control circuit 101b until the delay time generated by the control circuit 101e with delay, and after the delay time, By making the gate voltage constant by turning off the switch of the transistor M2, the change of the current I3 in the slope generating circuit 101a with variable current circuit is combined in a non-linear and linear manner.

  By using the configurations of the examples in FIGS. 10 and 11 and FIGS. 8 and 9 described above, it is possible to mix linear and non-linear slopes only by setting a delay time, and slope compensation that can ensure the stability of the switching regulator. The degree of freedom of the circuit can be increased.

  Although the step-down switching regulator has been described above, the step-up switching regulator will be described below.

  In general, a step-up switching regulator performs current feedback by detecting the current of an NMOS transistor. The operation of slope compensation in such a step-up switching regulator is shown in FIG. An example of the configuration of the slope compensation circuit according to the present invention provided in such a step-up switching regulator is shown in FIGS.

  In a step-up switching regulator, it is well known that current feedback is performed using a GND reference voltage, and the examples shown in FIGS. 13 to 16 are provided in a step-up switching regulator that generates such a GND reference slope. The present invention also relates to a slope compensation circuit according to the present invention.

  FIG. 13 is a circuit diagram showing a detailed example of the fifth configuration of the slope compensation circuit according to the present invention.

  In the slope compensation circuit of this example, the gate signal of the transistor M2 (in the variable current control circuit) is not directly taken from the power switch control signal 1301d, but through two inverters. This is to prevent a change in the gate voltage of the transistor M3 (in the slope generating circuit with a variable current circuit) due to switching by drawing the current I2 after turning off the switch of the transistor M4 (in the initial variable current setting circuit).

  As shown in FIG. 12, the power switch control signal 1301d is output high during the ON time.

  FIG. 14 is a circuit diagram showing a detailed example of the sixth configuration of the slope compensation circuit according to the present invention.

  In the slope compensation circuit shown in FIG. 14, a delay circuit 61e (current I4, capacitance C3, inverter) in the slope compensation circuit 61 in the second configuration example shown in FIGS. 6 and 7 is added to the slope compensation circuit in FIG. By providing the delay circuit in this way, a slope signal can be added from an arbitrary duty.

  At this time, “current I2 = current I5” is set, and the threshold value of the transistor M2 (in the variable current control circuit) is equal to the threshold value of the inverter (in the slope generating circuit with the variable current circuit) having the current I5 as a constant current load. Thus, the operation timings of the variable current control circuit 61b and the slope generating circuit 61a with the variable current circuit in the slope compensation circuit 61 shown in FIGS.

  FIG. 15 is a circuit diagram showing a detailed example of the seventh configuration of the slope compensation circuit according to the present invention.

  The basic operation of the slope compensation circuit shown in FIG. 15 is the same as that of the slope compensation circuit 81 shown in FIGS. 8 and 9, and a linear slope and a non-linear slope can be combined by determining a delay time. .

  FIG. 16 is a circuit diagram showing a detailed example of the eighth configuration of the slope compensation circuit according to the present invention.

  The basic operation of the slope compensation circuit shown in FIG. 16 is the same as that of the slope compensation circuit 101 shown in FIGS. 10 and 11, and a non-linear slope and a linear slope can be combined by determining a delay time. .

  As described above with reference to FIGS. 1 to 16, in this example, as a slope compensation circuit that generates a slope voltage used for stable operation control of the peak current control type PWM switching regulator, a variable having a capacitor C <b> 2 and a transistor M <b> 3. A slope generation circuit (1a) with a current circuit is provided, a linear slope voltage is generated by the capacitor C2, and the linear slope voltage generated by the capacitor C2 is obtained by using the transistor M3 and utilizing the characteristics of the transistor saturation region. It is possible to generate and output a non-linear slope voltage with a simple configuration, with a non-linear change.

  In order to change the gate voltage of the transistor M3 linearly, a variable current control circuit (1b) having a constant current I2, a transistor M2 and a capacitor C1 is provided, and a linear gate voltage is set using the constant current I2 and the capacitor C1. A configuration to generate.

  In addition, an initial variable current setting circuit (1c) that provides an initial gate signal to the transistor M3 is provided.

  Further, a delay circuit (61e) for delaying the generation of the non-linear slope voltage by a predetermined delay time is provided, and this delay circuit (61e) has a constant current inverter (I4 and inverter) and a capacitor (C3). The delay time is generated by the constant current inverter (I4 and inverter) and the capacitor (C3).

  Furthermore, by providing a delay circuit (81e) that generates a delay time by the constant current I4, the inverter, and the capacitor C3, the linear slope voltage and the nonlinear slope voltage are combined and output. At this time, until the delay time controlled by the delay circuit (81e), the gate voltage of the transistor M3 (in the slope generating circuit 81a with variable current circuit) is kept constant, and the linear slope voltage generated by the capacitor C2 is output. By changing the gate voltage of the transistor M3 linearly after the delay time, the slope voltage generated by the capacitor C2 is changed to a non-linear slope voltage and output.

  Alternatively, the slope voltage generated by the capacitor C2 is nonlinearly changed by linearly changing the gate voltage of the transistor M3 (in the slope generation circuit 101a with variable current circuit) until the delay time controlled by the control circuit with delay (101e). After the delay time, the gate voltage of the transistor M3 is kept constant and a linear slope voltage generated by the capacitor C2 is output.

  The peak current control type PWM switching regulator of this example is provided with any one of the slope compensation circuits having such a configuration, and the detection obtained by dividing the output voltage Vout by the resistors R1 and R2 in the amplifier 3. An error signal between the voltage Vfb and the reference voltage 5 is output, and the adder 2 adds the voltage corresponding to the current flowing through the switching element and the slope voltage output from any of the above-described slope compensation circuits and outputs the result. The comparator 4 compares the output voltage of the adder 2 with the output voltage of the amplifier 3, and the control circuit 6 determines the switching transistor in the power switch 8 with a current sensor based on the comparison result of the comparator 4 and the output of the oscillation circuit 7. By switching control, the ratio of the ON / OFF period of the switching transistor can be varied. As the output voltage Vout after adjusting the supplied voltage Vin.

  Further, by using such a peak current control type PWM switching regulator of this example for various electronic devices such as a computer device and a mobile phone, stable operation of these electronic devices can be realized with a simple configuration. .

  In addition, this invention is not limited to the example demonstrated using FIGS. 1-16, and can be variously changed in the range which does not deviate from the summary. For example, in this example, the step-down type peak current control type switching regulator and the step-up type peak current control type switching regulator are shown as examples. However, the inverting type peak current control type switching regulator can be configured in the same way. Is possible.

It is a block diagram which shows the 1st structural example of the slope compensation circuit concerning this invention. It is a circuit diagram which shows the detailed structural example of the slope compensation circuit in FIG. It is a block diagram which shows the structural example of the peak current control type switching regulator provided with the slope compensation circuit concerning this invention. It is explanatory drawing which shows the temperature characteristic calculation result of the slope compensation circuit in FIG. FIG. 2 is an explanatory diagram illustrating an example of a control operation of a peak current control type switching regulator provided with a slope compensation circuit in FIG. 1. It is a block diagram which shows the 2nd structural example of the slope compensation circuit concerning this invention. It is a circuit diagram which shows the detailed structural example of the slope compensation circuit in FIG. It is a block diagram which shows the 3rd structural example of the slope compensation circuit concerning this invention. It is a circuit diagram which shows the detailed structural example of the slope compensation circuit in FIG. It is a block diagram which shows the 4th structural example of the slope compensation circuit concerning this invention. It is a circuit diagram which shows the detailed structural example of the slope compensation circuit in FIG. It is explanatory drawing which shows the operation example of the slope compensation in a step-up type switching regulator. It is a circuit diagram which shows the detailed example of the 5th structure of the slope compensation circuit concerning this invention. It is a circuit diagram which shows the detailed example of the 6th structure of the slope compensation circuit concerning this invention. It is a circuit diagram which shows the detailed example of the 7th structure of the slope compensation circuit concerning this invention. It is a circuit diagram which shows the detailed example of the 8th structure of the slope compensation circuit concerning this invention. It is explanatory drawing which shows the operation example for the slope compensation in a step-down switching regulator.

Explanation of symbols

  1, 61, 81, 101: slope compensation circuit, 2: adder, 3: amplifier, 4: comparator, 5: reference voltage, 6: control circuit, 7: oscillation circuit, 8: power switch with current sensor, 1a , 61a, 81a, 101a: slope generating circuit with variable current circuit, 1b, 61b, 81b, 101b: variable current control circuit, 1c, 61c, 81c, 101c: initial variable current setting circuit, 1d, 61d, 81d, 101d, 1301d, 1401d, 1501d, 1601d: power switch control signal, 61e, 81e: delay circuit, 101e: control circuit with delay.

Claims (16)

A slope compensation circuit for generating a slope voltage used for stable operation control of a peak current control type PWM switching regulator,
A first means for generating a linear slope voltage;
A second means for nonlinearly changing the linear slope voltage generated by the first means by utilizing the characteristics of the saturation region of the transistor provided, and generating and outputting a nonlinear slope voltage; Slope compensation circuit characterized by The slope compensation circuit according to claim 1,
A slope compensation circuit comprising third means for linearly changing a gate voltage of a transistor included in the second means. The slope compensation circuit according to claim 2,
The slope compensation circuit, wherein the third means includes means for generating the linear gate voltage using a constant current and a capacitance. The slope compensation circuit according to any one of claims 1 to 3,
A slope compensation circuit comprising a fourth means for applying an initial gate signal to the transistor included in the second means. The slope compensation circuit according to any one of claims 1 to 4,
A slope compensation circuit comprising: fifth means for delaying generation of the non-linear slope voltage by the second means by a predetermined delay time. The slope compensation circuit according to claim 5,
The fifth means has a means for generating the delay time by a constant current inverter and a capacitor. The slope compensation circuit according to any one of claims 1 to 6,
A slope compensation circuit comprising a sixth means for outputting a combination of the linear slope voltage generated by the first means and the non-linear slope voltage generated by the second means. The slope compensation circuit according to claim 7,
The sixth means has a seventh means for outputting the linear slope voltage until a predetermined delay time, and outputting the nonlinear slope voltage after the delay time. The slope compensation circuit according to claim 8,
The seventh means has means for changing the gate voltage of the transistor included in the second means constant until the delay time and linearly after the delay time. A slope compensation circuit according to claim 8 or 9, wherein
The seventh means has a means for generating the delay time by means of a constant current inverter and a capacitor. The slope compensation circuit according to claim 7,
The sixth means includes an eighth means for outputting the nonlinear slope voltage until a predetermined delay time and outputting the linear slope voltage after the delay time. The slope compensation circuit according to claim 11,
The eighth means has means for linearly changing the gate voltage of the transistor included in the second means until the delay time and making it constant after the delay time. A slope compensation circuit according to claim 11 or claim 12,
The eighth means has means for generating the delay time by means of a constant current inverter and a capacitor.   A switching regulator comprising the slope compensation circuit according to any one of claims 1 to 13. The switching regulator according to claim 14, wherein
Amplifier means for outputting an error signal between the detection voltage obtained by dividing the output voltage and the reference voltage;
Adding means for adding the voltage corresponding to the current flowing through the switching element and the slope voltage output from the slope compensation circuit;
Comparing means for comparing the output voltage of the adding means and the output voltage of the amplifier means;
Control means for controlling the switching of the switching transistor based on the comparison result of the comparison means, wherein the ratio of the on / off period of the switching transistor is varied, and the supplied voltage is adjusted and then output. Switching regulator.   An electronic device using the switching regulator according to claim 14.

Images