JP2008092779A - Switching power supply control system and mobile terminal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means for avoiding unstable outputs, in a power supply control system, capable of stepping up and stepping down of the input voltage. <P>SOLUTION: In an error output monitor 13, a comparator compares the output of an error amplifier 9 with Duty detection level at step-up operation. The comparator compares the output of the error amplifier 9 with Duty detection level at stepping-down operation. Each of the comparator outputs is outputted, after reaching a stable condition by way of a chattering removal circuit. If the output of the error amplifier 9 is higher than the duty detection level at step-up operation, a power supply control determining means 14 turns off a step-down DC-DC block 5. If the output of the error amplifier 9 is lower than the duty detection level at step-down operation, the power supply control determining means 14 turns off a step-up DC-DC block 6. The power supply control determining means 14 issues a command to a clamp circuit 15 to control supplying of triangular waves to the step-down DC-DC block 5 and step-up DC-DC block 6. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a switching power supply control system that switches between a step-up operation and a step-down operation, and a portable terminal that includes a switching power supply circuit.

  In mobile devices such as mobile phones that perform wireless communication, high performance and multi-function are progressing. However, in order to provide a mobile device with many functions, functional devices corresponding to the functions are required, and power supply voltages corresponding to the respective functional devices are also required. In particular, regarding a power source of a power amplifier (hereinafter referred to as a power amplifier), an output voltage and an output current corresponding to the transmission power are required.

  In recent years, the maximum transmission power of mobile devices has been increasing in response to higher communication speeds. In addition, the power supply voltage of the battery may decrease, and in order to obtain the required power, the voltage corresponding to the transmission power must be provided to the power amplifier dynamically and efficiently regardless of the voltage of the battery. Don't be.

  In addition, the battery voltage has a long life and high performance. For example, the voltage range of a conventional lithium ion battery was 3.2 to 4.2 V, but recently it has become a wide range of 2.7 to 4.5 V. Even when a 3V functional device is used, it is necessary to step down when the battery voltage is high and to step up when the battery voltage is low. In such a case, for example, a switching power supply is a power supply useful for efficiently generating an arbitrary voltage.

  If the power supply voltage to be used is smaller or larger than the voltage range of a lithium ion battery or the like, the switching power supply can be realized by, for example, a regulator or a single-function power supply configuration. However, when the power supply voltage used is within the range of the battery power supply, or when it is necessary to dynamically change the voltage including the battery voltage range, such as a power amplifier, a complex power supply is required. . In such a case, a step-up / step-down DC-DC converter is used as one means (see Patent Document 1).

  For example, Patent Document 1 describes a step-up / step-down DC-DC converter configured so as not to cause a malfunction due to output voltage fluctuation when switching between a step-up mode and a step-down mode. The step-up / step-down DC-DC converter is configured so that the input voltage at which the operation mode switches is different between when the input voltage is lowered and when the input voltage is raised. With such a configuration, the step-up / step-down DC-DC converter can avoid malfunctions such as repeating two operation modes due to output voltage fluctuations when the operation modes are switched.

Japanese Patent Laying-Open No. 2005-059443 (paragraph 0038, FIG. 2)

  However, the step-up / step-down DC-DC converter causes the step-up / step-down operation to occur simultaneously or continuously when the output voltage suddenly fluctuates between the step-down operation region and the step-up operation region due to a steep load change or the like. End up. In such a case, for example, in the step-up / step-down DC-DC converter described in Patent Document 1, the boost converter or the step-down converter temporarily operates, and overshoot or undershoot occurs in the output voltage. As a result, the output voltage may become unstable.

  A configuration of a general synchronous rectification step-up / step-down DC-DC converter will be described. FIG. 8 is a system configuration diagram showing a simplified configuration of a conventional synchronous rectification step-up / step-down DC-DC converter. As shown in FIG. 8, the step-up / step-down DC-DC converter includes a step-down DC-DC block 5 and a step-up DC-DC block 6. Specifically, the step-up / step-down DC-DC converter includes an input power source (for example, a lithium ion battery) 1 of the step-up / step-down DC-DC converter, an input-side capacitor 2 for stabilizing the input potential, A coil 3 for executing discharge, an output-side capacitor 4 for stabilizing the output voltage, a step-down DC-DC block 5 for stepping down the input voltage, a step-up DC-DC block 6 for stepping up the input voltage, An oscillation circuit (OSC) 7 for performing PWM control, a control block 8 for performing offset and phase control on a clock dedicated to the booster side of OSC 7, a voltage divided from the output voltage Vout, and a reference of the reference voltage source 10 It includes an error amplifier 9 that amplifies the difference from the voltage, bleeder resistors 11 and 12 that divide the output voltage Vout, and an output terminal 20. Hereinafter, it is assumed that the output voltage Vout at the output terminal 20 is within the voltage range of the input power supply 1 and has a constant output voltage.

  The step-down DC-DC block 5 compares the switching elements 51 and 52, the drive circuits 53 and 54 for driving the switching elements, the triangular wave generated by the OSC 7 and the output of the error amplifier 9 to generate a PWM signal. (Hereinafter referred to as a comparator) 55. The step-down DC-DC block 5 has a function of stepping down the voltage of the input power supply 1.

  For example, an npn transistor is used as the switching element 51. The emitter of the switching element 51 is connected to the input power source 1, the collector is connected to the coil 3, and the base is connected to the drive circuit 53.

  As the switching element 52, for example, a pnp transistor is used. The emitter of the switching element 52 is grounded, the collector is connected to the coil 3, and the base is connected to the drive circuit 54.

  The comparator 55 outputs a pulse signal (PWM signal). The switching elements 51 and 52 are controlled by the output of the comparator 55. A signal from the error amplifier 9 is input to the non-inverting input terminal of the comparator 55, and a triangular wave from the OSC 7 is input to the inverting input terminal.

  The step-up DC-DC block 6 includes switching elements 61 and 62, drive circuits 63 and 64 for driving the respective switching elements, a comparator that generates a PWM signal from the triangular wave generated by the OSC 7 and the output of the error amplifier 9. 65. The step-up DC-DC block 6 has a function of stepping up the voltage of the input power supply 1.

  For example, an npn transistor is used as the switching element 61. The switching element 61 has an emitter connected to the output terminal 20, a collector connected to the coil 3, and a base connected to the drive circuit 63.

  As the switching element 62, for example, a pnp transistor is used. The emitter of the switching element 62 is grounded, the collector is connected between the coil 3 and the collector of the switching element 61, and the base is connected to the drive circuit 64.

  The comparator 65 outputs a pulse signal (PWM signal). The switching elements 61 and 62 are controlled by the output of the comparator 65. Specifically, the comparator 65 receives a signal from the error amplifier 9 at a non-inverting input terminal, and receives an offset and phase-controlled triangular wave from the OSC 7 at an inverting input terminal.

  In the configuration shown in FIG. 8, the triangular wave offset and phase control are performed on the step-up DC-DC block 6 side, but the triangular wave offset and phase control may be performed on the step-down DC-DC block 5 side. The types of the input-side capacitor 2 and the output-side capacitor 3 are not particularly specified. It is determined appropriately according to the system in which the step-up / step-down DC-DC converter is used.

  FIG. 9 is a chart showing the operation of the step-up / step-down DC-DC converter shown in FIG. FIG. 9 shows the relationship between the triangular wave output from the OSC 7 and the output signal output from the error amplifier 9 (hereinafter referred to as the error amplifier output 21). As shown in FIG. 9, the triangular wave potential in the step-up operation (step-up DC-DC block) is set higher than the triangular wave potential in the step-down operation (step-down DC-DC block). Further, the upper limit voltage of the triangular wave for the step-down operation (hereinafter referred to as the step-down side triangular wave 23) and the lower limit voltage of the triangular wave for the step-up operation (hereinafter referred to as the step-up side triangular wave 22) do not overlap each other and are too far apart. It is assumed that there is not.

  Hereinafter, a region where the error amplifier output 21 is within the range of the step-down triangular wave 23 is referred to as a step-down operation region. A region where the error amplifier output 21 exists within the range of the step-up side triangular wave 22 is referred to as a step-up operation region. A portion where the step-down operation region and the step-up operation region overlap as shown in FIG. 9 is referred to as a step-up / step-down operation region.

  When the output voltage Vout is lower than the input voltage, that is, in the step-down operation region, the output of the error amplifier 9 is in the range of the lower triangular wave (step-down triangular wave 23). In such a case, the comparison result between the error amplifier output 21 by the comparator 55 and the triangular wave output from the OSC 7 is supplied to the switching elements 51 and 52 as a step-down switching signal. That is, the step-down DC-DC block 5 performs PWM control. When the error amplifier output 21 is smaller than the step-down triangular wave 23 in the step-down operation region, the step-down PWM output 24 (that is, the gate signals of the switching elements 51 and 52) becomes “H”.

  In the step-down operation region, the step-up triangular wave 22 is always at a higher level than the error amplifier output 21. In such a case, the step-up PWM output 25 (that is, the gate signals of the switching elements 61 and 62) is always “L”. Therefore, in the step-up DC-DC block 6, the switching element 61 is fixed to “ON” and the switching element 62 is fixed to “OFF”, and the output on the step-down side is output as Vout as it is.

  On the other hand, when the output voltage Vout is higher than the input voltage, that is, in the boosting operation region, the output of the error amplifier 9 is within the upper triangular wave (boost-side triangular wave 22). In such a case, the comparison result between the error amplifier output 21 by the comparator 65 and the triangular wave output from the OSC 7 is supplied to the switching elements 61 and 62 as a boosting switching signal. That is, the step-up DC-DC block 6 performs PWM control. When the error amplifier output 21 is smaller than the boost side triangular wave 22 in the boost operation region, the boost PWM output 25 (that is, the gate signals of the switching elements 61 and 62) becomes “L”.

  In the step-up operation region, the step-down triangular wave 23 is always at a lower level than the error amplifier output 21. In such a case, the step-down PWM output 24 is always “L”. Therefore, in the step-down DC-DC block 5, the switching element 51 is fixed to “ON” and the switching element 52 is fixed to “OFF”. The step-up / step-down DC-DC converter directly inputs the input voltage to the coil 3 and boosts the voltage by the boost DC-DC block 6.

  As described above, the step-up / step-down DC-DC converter performs an operation as shown in FIG. 9 in an ideal state.

  Next, a case where the output voltage Vout temporarily varies due to load variation or the like will be described. FIG. 10 is an explanatory diagram showing an example of an unstable operation that occurs when the output voltage Vout drops due to a load variation or the like during the step-down operation.

  When the output voltage Vout drops, the output voltage Vout is first input to the error amplifier 9 through the bleeder resistor. Since the output voltage 30 is shifted downward (low voltage side) with respect to a certain reference, the output level of the error amplifier output 21 is increased in order to increase the output voltage. In this case, the level (error amplifier output 21) at this time is applied to the boost side triangular wave, and as shown by B in FIG. 10, the boost operation temporarily occurs. As a result, the temporarily dropped output voltage 30 exceeds a specified voltage by the boosting operation, and overshoots.

  The temporary boost operation during the step-down operation makes the output voltage unstable and charges are temporarily discarded to the GND (ground) level for boosting. Is also disadvantageous.

  Therefore, the present invention can stabilize the output voltage even when the output voltage suddenly fluctuates between the step-down operation region and the step-up operation region due to a steep load change or the like, and can reduce power consumption. An object is to provide a switching power supply control system and a portable terminal.

  A switching power supply control system according to the present invention is a switching power supply control system comprising an error voltage value output means for comparing an output voltage value with a reference voltage value and outputting an error voltage value, and a step-down means for stepping down an input voltage. A boosting means for boosting the input voltage, a boosting operation reference value (for example, corresponding to the duty detection level 19 in the step-down operation in FIG. 4) and a step-down as an error voltage reference for determining whether or not to operate the boosting means. Error voltage value comparison means for comparing with a step-down operation reference value (for example, corresponding to the duty detection level 18 at the time of step-up operation in FIG. 4) as a reference for operating the means and outputting a signal indicating the comparison result A signal stabilization means for inputting a signal output from the error voltage value comparison means and outputting a correction signal from which a vibration component included in the signal is removed, and a signal stabilization method. There Based on the output correction signal, characterized by comprising an operation control means for controlling the respective operations of the step-up means and the step-down unit.

  Preferably, the signal stabilization means outputs a correction signal of that level when the level of the signal output from the error voltage value comparison means is the same output level over a predetermined time. In that case, the signal stabilization means includes a plurality of stages of flip-flops, the first stage flip-flops input the signal output by the error voltage value comparison means, and the flip-flops subsequent to the first stage output the outputs of the preceding flip-flops. May be input.

  The error voltage value comparison unit includes a step-up operation reference value generation unit (for example, a step-down operation duty detection level generation unit 138 in FIG. 2) that generates a step-up operation reference value that serves as a reference for determining whether or not to operate the step-up unit. Step-down operation reference value generation means (for example, step-up operation duty detection level generation unit 137 in FIG. 2) that generates a step-down operation reference value that serves as a reference for determining whether or not to operate the step-down means is provided to generate a step-up operation reference value. The means is preferably generated so that the step-up operation reference value is smaller than the step-down operation reference value generated by the step-down operation reference value generation means.

  The operation control means turns off the boosting means when the signal output from the signal stabilization means changes when the error voltage value is equal to or lower than the boosting operation reference value, and signals when the error voltage value exceeds the boosting operation reference value. When the signal outputted from the stabilizing means changes, it is preferable to turn on the boosting means.

  The operation control means turns on the step-down means when the signal output from the signal stabilization means changes when the error voltage value is equal to or lower than the step-down operation reference value, and the error voltage value exceeds the step-down operation reference value. When the signal output from the signal stabilization means changes, the step-down means is preferably turned off.

  The switching power supply control system according to the present invention is a switching power supply control system including a triangular wave generating means for generating a triangular wave to be supplied to the boosting means and the stepping down means, wherein the operation control means outputs the triangular wave output from the triangular wave generating means. A triangular wave supply control means for controlling supply; the triangular wave supply control means stops the supply of the triangular wave to the boosting means when the boosting means is off, and the triangular wave supply to the stepping down means when the boosting means is off. It is preferable to stop the supply.

  The switching power supply control system according to a preferred embodiment of the present invention detects a certain duty level of switching of the step-down and step-up DC-DC converters at a certain time, thereby allowing step-down DC-DC operation, step-up DC- Switching between DC operation and step-up / step-down DC-DC operation. When a certain on-duty level during the step-down DC-DC operation (for example, the duty detection level 19 during the step-down operation in FIG. 4) is exceeded, the boost DC-DC block is turned on and the oscillator (for example, OSC 7 in FIG. 1). A triangular wave is supplied from Furthermore, when a certain duty level (for example, the duty detection level 18 in the boosting operation in FIG. 4) is secured in the step-up DC-DC operation, the power of the step-down DC-DC operation block is turned off, and the triangular wave from the oscillator is generated. Stop supplying.

  This eliminates the need to always operate both the step-up DC-DC converter block and the step-down DC-DC converter block. As a result, the step-down and step-up, that is, the step-up / step-down DC-DC converter does not operate unless the input voltage and the output voltage are close to each other or much larger than the consumption current of the DC-DC converter. As a result, this converter can provide an efficient voltage and can suppress fluctuations in the output voltage caused by changes in the load as much as possible.

  A portable terminal according to the present invention is a portable terminal provided with error voltage value output means for comparing an output voltage value with a reference voltage value and outputting an error voltage value, a step-down means for stepping down the input voltage, and an input voltage And a step-up operation reference value for determining whether to operate the step-up means and a step-down operation reference value for determining whether to operate the step-down means. Error voltage value comparison means for outputting a signal indicating the result, signal stabilization means for inputting the signal output from the error voltage value comparison means, and outputting a correction signal from which the vibration component included in the signal has been removed, and signal stabilization And a switching power supply circuit including an operation control means for controlling the operation of each of the boosting means and the step-down means based on the correction signal output by the means.

  According to the present invention, it is possible to suppress fluctuations in the output voltage such as going down and boosting, and to stabilize the output voltage.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a system configuration diagram showing an example of a switching power supply control system according to the present invention. As shown in FIG. 1, the step-up / step-down DC-DC converter (switching power supply circuit) according to the present invention includes components of the above-described general step-up / step-down DC-DC converter, and further outputs the error amplifier 9. The error amplifier output monitor 13 for comparing the specified duty level (hereinafter referred to as the duty detection level) and the output signal indicating the determination result by the error amplifier output monitor 13 in response to each of the DC-DC converter blocks Power control determination means 14 for controlling the power supply and the triangular wave, switches 16 and 17 for switching circuits upon receiving a signal from the power supply control determination means 14, and each DC when the triangular wave from the OSC 7 is not input A clamp circuit 15 for maintaining the potential of the DC block;

  The duty detection level refers to each reference voltage value for determining whether or not to operate each DC-DC block. For example, when the output signal of the error amplifier 9 exceeds the duty detection level during the boosting operation described later, the power supply control determination unit turns off the operation of the step-down DC-DC block 5.

  FIG. 2 is a block diagram showing a configuration example of the error amplifier output monitor 13 and the power supply control determination unit 14. As shown in FIG. 2, the error amplifier output monitor 13 includes a comparator 131 that compares the output level of the output of the error amplifier 9 and the output of the step-down operation duty detection level generation unit 138 and the output of the comparator 131. The output levels of the chattering removal circuit 132 for outputting after a stable state, the buffer output unit 133 of the chattering removal circuit 132, the output of the error amplifier 9 and the output of the duty detection level generation unit 137 during the boosting operation are set. The comparator 134 to be compared, the chattering removal circuit 135 for outputting after the output of the comparator 134 becomes stable, and the buffer output unit 136 of the chattering removal circuit 135 are provided.

  Note that the output of the step-up operation duty detection level generation unit 137 is input to the non-inverting input terminal of the comparator 134, and the output of the step-down operation duty detection level generation unit 138 is input to the non-inverting input terminal of the comparator 131. . The output of the error amplifier 9 is input to the inverting input terminals of the comparators 131 and 134, respectively.

  The chattering removal circuits 132 and 135 have a function of outputting the output signal of the comparator after it becomes stable. The chattering removal circuits 132 and 135 operate when the output voltage Vout is instantaneously operated due to a load change or the like (for example, an oscillation operation in which the outputs of the comparators 131 and 134 repeat “H” and “L” in a short cycle). Prevent malfunction. That is, the output signals of the comparators 131 and 134 are corrected and a correction signal is output. Note that as the chattering removal circuits 132 and 135, an analog delay circuit using a capacitor or the like may be used, or a digital circuit using a flip-flop or the like may be used.

  The step-up operation duty detection level generation unit 137 and the step-down operation duty detection level generation unit 138 generate a certain duty level (duty detection level) during step-down and step-up. Each comparator compares the output from the error amplifier 9 with each Duty detection level. Then, based on the comparison result, the power control determination unit 14 determines whether or not to operate each DC-DC block. Note that the duty detection level during the boosting operation is always set to a level higher than the duty detection level during the step-down operation.

  The power supply control determination unit 14 includes a decoder 141 that receives and decodes the output from the error amplifier output monitor 13, and a power supply control circuit 142 that controls each DC-DC block and a triangular wave based on the decoding result.

  FIG. 3 is a block diagram illustrating a configuration example of the chattering removal circuit 132 or the chattering removal circuit 135. The chattering removal circuit monitors the signal change of the comparator by flip-flops 1321 to 1323. Specifically, the chattering removal circuit receives the outputs of the respective flip-flops 1321 to 1323 by the logic circuit 1325, and sends a rising signal to the clock line of the flip-flop 1325 if the clock sections are all the same logic. That is, the chattering removal circuit has a circuit configuration that latches the output.

  Note that the clocks input to the flip-flops 1321 to 1323 may be taken in from the outside in order to obtain timing, or a triangular wave from the OSC 7 may be used. 3 shows a three-stage flip-flop, the chattering removal circuit may further include a plurality of flip-flops. The chattering removal time (a constant stabilization time described later, for example, see FIG. 4) may be controlled by the number of flip-flop stages.

  Next, the operation of the step-up / step-down DC-DC converter according to the present invention will be described. FIG. 4 is an explanatory diagram illustrating an example of the operation of the step-up / step-down DC-DC converter. FIG. 4 shows the step-up operation duty detection level 18 generated by the step-up operation duty detection level generation unit 137 and the step-down operation duty detection level 19 generated by the step-down operation duty detection level generation unit 138. Yes. The step-up operation duty detection level 18 is a reference level for determining whether or not to perform the step-down operation. The step-down operation duty detection level 19 is a reference level for determining whether or not to perform a step-up operation.

  As shown in FIG. 4, when the step-down operation is a certain duty or less (that is, the level of the error amplifier output 21 is the duty detection level 19 or less during the step-down operation), the step-up / step-down DC-DC converter is step-up DC- The DC block 6 is stopped. Specifically, the step-up / step-down DC-DC converter stops providing the triangular wave to the boost side by the clamp circuit 15 and sets the gate signals of the switching elements 61 and 62 to “L” to be in a conductive state. By doing so, the boost DC-DC block 6 can be turned off when the error amplifier output 21 is equal to or lower than the duty detection level 19 during the step-down operation. As a result, the current consumption of the triangular wave generation circuit and the step-up DC-DC block 6 can be suppressed.

  In the above-described state, when the input power supply voltage (for example, battery voltage) decreases or when the output voltage Vout increases, the level of the error amplifier output 21 increases and the duty of the step-down PWM operation decreases. When the error amplifier output 21 exceeds the duty detection level 19 during the step-down operation, the comparator 131 reacts (point 4a in FIG. 4), but no signal is output until a certain time elapses by the chattering removal circuit 132. In other words, the output of the comparator 131 is output when the state is stable for a certain period of time (point 4b in FIG. 4). Note that the “certain time” in the chattering removal circuit 132 is specifically determined by the number of flip-flop stages.

  The power supply control determination unit 14 turns on the boost DC-DC block 6 based on the signal output from the chattering removal circuit 132 and inputs the boost-side triangular wave to the comparator 65 of the boost DC-DC block 6 to perform the boost operation. Set to be able to migrate to.

  When the input power supply voltage further decreases or when the output voltage Vout is increased, the level of the error amplifier output 21 becomes high, and the comparator 134 reacts when the duty detection level 18 is exceeded during the boosting operation (4c in FIG. 4). point). However, no signal is output until a certain period of time has elapsed by the chattering removal circuit 136. That is, the output of the comparator 134 is output when the state is stable for a certain period of time (point 4d in FIG. 4). The power supply control determination unit 14 turns off the step-down DC-DC block 5 based on the signal output from the chattering removal circuit 132 and stops the triangular wave on the step-down side by the clamp circuit 15.

  FIG. 5 is an explanatory diagram showing an example of another operation by the step-up / step-down DC-DC converter. FIG. 5 shows a case where the output voltage Vout is lowered, contrary to the case of FIG. As shown in FIG. 5, when the boost operation is a certain duty or higher (that is, the level of the error amplifier output 21 is the duty detection level 18 or higher during the boost operation), the step-up / step-down DC-DC converter is a step-down DC- The DC block 6 is stopped. Specifically, the step-up / step-down DC-DC converter stops providing the triangular wave to the step-down side by the clamp circuit 15 and makes the gate signal of the switching element 51 “L” to be in a conductive state. By doing so, the step-down DC-DC block 5 can be turned off when the level of the error amplifier output 21 is equal to or higher than the duty detection level 18 during the step-up operation. Further, the supply of the triangular wave to the step-down DC-DC block 5 is stopped to save power.

  When the input power supply voltage (for example, battery voltage) rises from the above state or when the output voltage Vout is lowered, the level of the error amplifier output is lowered, so that the boost PWM duty is lowered. When the level of the error amplifier output 21 falls below the duty detection level 18 during the boost operation, the comparator 134 reacts (point 5a in FIG. 5). In that case, the output of the comparator 134 changes from “H” to “L”.

  The step-up / step-down DC-DC converter turns on the step-down DC-DC block 5 (point 5b in FIG. 5) when the chattering removal circuit 135 becomes constant in a certain stable time, and converts the step-down triangular wave into the step-down DC-DC block. 5 is supplied. Specifically, the step-up / step-down DC-DC converter supplies a triangular wave to the step-down DC-DC block 5 by the clamp circuit 15. By doing so, the step-up / step-down DC-DC converter is set so as to shift to the step-down operation.

  Further, when the input power supply voltage rises or the output voltage is lowered, the level of the error amplifier output 21 becomes low, and the comparator 131 reacts when the duty detection level 19 is exceeded (below) during the step-down operation (in FIG. 5). 5c point). Specifically, the output of the comparator 131 changes from “H” to “L” at a point 5c in FIG. The step-up / step-down DC-DC converter is a chattering removal circuit 132 that turns off the boost DC-DC block 6 (point 5d in FIG. 5) when it becomes constant within a certain stable time, and supplies a triangular wave to the boost side as a clamp circuit. 15 and the switching element 61 is turned on.

  As described above, the step-up / step-down DC-DC converter controls the operation of the step-up DC-DC block 6 based on the output 27 of the chattering removal circuit 132. The step-up / step-down DC-DC converter controls the operation of the step-down DC-DC block 5 based on the output 29 of the chattering removal circuit 135.

  Next, the operation of the step-up / step-down DC-DC converter during unstable operation will be described. FIG. 6 is an explanatory diagram showing the operation of the step-up / step-down DC-DC converter in the case where the output voltage Vout temporarily drops due to load fluctuation during the step-down operation. As described above, when the output voltage 30 temporarily decreases due to a load variation or the like (see A in FIG. 6), in a general step-up / step-down DCDC converter, a boost converter (step-up DC-DC block) temporarily. Operates and overshoot occurs in the output voltage Vout (see B in FIG. 10). However, the step-up / step-down DC-DC converter according to the present invention does not execute the step-up operation because the step-up DC-DC block is turned off during the step-down operation. For this reason, the overshoot of the output voltage Vout is reduced.

  Even if the output voltage Vout drops temporarily with the step-up DC-DC block 6 turned on, the step-up / step-down DC-DC converter avoids switching to the step-up operation by the chattering removal circuit. Can do. In other words, by providing the chattering removal circuit, the step-up / step-down DC-DC converter can avoid an unstable operation such as a step-down operation and a step-up operation instantaneously.

  FIG. 7 is an explanatory diagram collectively showing the series of operations described above. The step-down level detection represents the output of the chattering removal circuit 132, and the step-up level detection represents the output of the chattering removal circuit 135. The state change between the step-down operation, the step-up operation, and the step-up operation + step-down operation is switched between the duty detection level 18 during the step-up operation and the duty detection level 19 during the step-down operation.

  For example, when the step-down detection level (the output 27 of the chattering removal circuit 132) is L → H, the step-up / step-down DC-DC converter turns on the step-up DC-DC block 6. Specifically, this corresponds to the step-up / step-down DC-DC converter turning on the step-up DC-DC block 6 at a point 4b in FIG.

  As described above, when the step-up / step-down DC-DC converter is completely in step-down operation or step-up operation, the other is turned off to save power and avoid unstable operation due to fluctuations in the output voltage Vout. Can do. By doing so, the buck-boost DC-DC converter controls to turn off the other when there is a difference between the voltage on the input side and the voltage on the output side and only one of the DC-DC converters is used. To realize a power-saving circuit.

  Further, the conventional step-up / step-down DC-DC converter always operates the circuit by inputting a triangular wave to the step-down / step-up / step-up circuit, whereas the step-up / step-down DC-DC converter of the present embodiment clearly has one side. When only this converter operates, the clock supply to the other circuit is stopped. By doing so, it is possible to prevent the buck-boost DC-DC converter from malfunctioning. Further, in this embodiment, when only one converter operates, it is possible to realize a power saving circuit that does not cause excessive current consumption by turning off the other converter.

  It can be applied to a power supply control system that can step up and down the input voltage.

It is a system configuration figure showing an example of a switching power supply control system. FIG. 3 is a block diagram showing a configuration example of an error amplifier output monitor 13 and a power supply control determination unit 14. It is a block diagram which shows one structural example of a chattering removal circuit. It is explanatory drawing which shows an example of operation | movement of a step-up / step-down DC-DC converter. It is explanatory drawing which shows an example of operation | movement of a step-up / step-down DC-DC converter. It is explanatory drawing which shows operation | movement of the step-up / step-down DC-DC converter when the output voltage Vout falls temporarily by load fluctuation | variation at the time of step-down operation. It is explanatory drawing which shows a series of operation | movement collectively. It is a system block diagram which shows the structure of a general step-up / step-down DC-DC converter. It is a chart which shows operation | movement of a step-up / step-down DC-DC converter. It is explanatory drawing which shows an example of the unstable operation | movement which generate | occur | produces when the output voltage Vout falls.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Input power supply 2, 4 Capacitor 3 Coil 5 Step-down DC-DC block 6 Step-up DC-DC block 7 Oscillation circuit OSC
8 Control block 9 Error amplifier 10 Reference voltage source 11, 12 Bleeder resistance 13 Error amplifier output monitor 131, 134, 55, 65 Comparator 132, 135 Chattering removal circuit 133, 136 Buffer output unit 137 Boost detection duty detection level generation unit 138 Step-down operation duty detection level generator 1321, 1322, 1323 Flip-flop 1325 Logic circuit 14 Power supply control determination means 141 Decoder 142 Power supply control circuit 15 Clamp circuit 16, 17 Switch 18 Duty detection level Duty detection level 19 Step-down operation duty detection level 20 Output Terminal 21 Error Amplifier Output 22 Boost Side Triangular Wave 23 Step Down Side Triangle Wave 24 Step Down PWM Output 25 Step Up PWM Output 26 Output of Comparator 131 27 Chattering Removal Circuit 13 Output 30 output voltage Vout of the output 29 chattering filter circuit 135 of the output 28 comparator 134
51, 52, 61, 62 Switching element 53, 54, 63, 64 Drive circuit

Claims (8)

In the switching power supply control system provided with the error voltage value output means for comparing the output voltage value and the reference voltage value and outputting the error voltage value,
Step-down means for stepping down the input voltage;
Boosting means for boosting the input voltage;
A signal indicating a comparison result by comparing the error voltage value with a boosting operation reference value serving as a reference for whether or not to operate the boosting means and a step-down operation reference value serving as a reference for determining whether or not to operate the step-down means, respectively. Error voltage value comparison means for outputting
A signal stabilization unit that inputs the signal output from the error voltage value comparison unit and outputs a correction signal from which a vibration component included in the signal is removed;
A switching power supply control system comprising: an operation control unit that controls the operation of each of the step-up unit and the step-down unit based on a correction signal output from the signal stabilization unit. The switching power supply control system according to claim 1, wherein the signal stabilization means outputs a correction signal of the level when the level of the signal output from the error voltage value comparison means is the same output level over a predetermined time. The signal stabilization means includes a plurality of flip-flops,
The first stage flip-flop inputs the signal output by the error voltage value comparison means,
The switching power supply control system according to claim 2, wherein the flip-flop at the stage subsequent to the first stage inputs the output of the flip-flop at the previous stage. The error voltage value comparison means is
A step-up operation reference value generating unit that generates a step-up operation reference value that serves as a reference for operating the step-up unit;
A step-down operation reference value generating unit that generates a step-down operation reference value that is a reference for determining whether or not to operate the step-down unit;
4. The boost operation reference value generation unit generates the boost operation reference value to be smaller than the step-down operation reference value generated by the step-down operation reference value generation unit. 5. The switching power supply control system according to item 1. The operation control means is
When the signal output from the signal stabilizing means changes when the error voltage value is equal to or lower than the boosting operation reference value, the boosting means is turned off,
5. The boosting unit is turned on when the signal output from the signal stabilization unit changes when the error voltage value exceeds the boosting operation reference value. 5. The switching power supply control system described. The operation control means is
When the error voltage value is equal to or lower than the step-down operation reference value and the signal output from the signal stabilization unit changes, the step-down unit is turned on,
The step-down unit is turned off when the signal output from the signal stabilization unit changes when the error voltage value exceeds the step-down operation reference value. The switching power supply control system described. A switching power supply control system comprising a triangular wave generating means for generating a triangular wave to be supplied to the boosting means and the step-down means,
The operation control means includes a triangular wave supply control means for controlling supply of the triangular wave output from the triangular wave generation means,
The triangular wave supply control means includes:
When the booster is off, supply of the triangular wave to the booster is stopped,
The switching power supply control system according to any one of claims 1 to 6, wherein when the step-down unit is off, the supply of the triangular wave to the step-down unit is stopped. In a portable terminal having an error voltage value output means for outputting an error voltage value by comparing an output voltage value and a reference voltage value,
Step-down means for stepping down the input voltage;
Boosting means for boosting the input voltage;
A signal indicating a comparison result by comparing the error voltage value with a boosting operation reference value serving as a reference for whether or not to operate the boosting means and a step-down operation reference value serving as a reference for determining whether or not to operate the step-down means, respectively. Error voltage value comparison means for outputting
A signal stabilization unit that inputs the signal output from the error voltage value comparison unit and outputs a correction signal from which a vibration component included in the signal is removed;
A portable terminal comprising: a switching power supply circuit including an operation control unit that controls the operation of each of the step-up unit and the step-down unit based on the correction signal output from the signal stabilization unit.

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