JP4433151B2 - Boost DC / DC converter and driving method thereof - Google Patents

Description

  The present invention relates to a step-up DC / DC converter, and more particularly to a method for driving a step-up DC / DC converter.

  As is well known in this technical field, a DC / DC converter refers to a power converter that converts a DC voltage (DC input voltage) at a certain voltage level into a DC voltage (DC output voltage) at another voltage level. . The DC / DC converter is also called a switching regulator. Here, a DC / DC converter in which the voltage level of the DC output voltage is higher than the voltage level of the DC input voltage is called a step-up DC / DC converter, and the voltage level of the DC output voltage is lower than the voltage level of the DC input voltage. The DC / DC converter is called a step-down DC / DC converter. The present invention relates to a step-up DC / DC converter.

  In a step-up DC / DC converter, a transistor is used as a switch, which is switched, and a DC input voltage is once changed to an AC voltage. After the voltage is boosted by a transformer, the voltage is rectified and converted to a DC output voltage.

  As this step-up DC / DC converter, there is a step-up synchronous rectification DC / DC converter.

FIG. 1 shows an external appearance of the step-up synchronous rectification DC / DC converter 10. The step-up synchronous rectification DC / DC converter 10 shown in the figure is used for a backlight of a liquid crystal display device. The step-up synchronous rectification DC / DC converter 10 has a power input terminal VDD, a switch terminal SW, a power output terminal VOUT, a feedback terminal FB, a ground terminal GND, and a control terminal CNTRL. The ground terminal GND is held at the ground potential. The power supply input terminal VDD is connected to a power supply terminal VBATT of an input power supply (not shown). As a result, the power supply input voltage V _DD is applied from the input power supply between the ground terminal GND and the power supply input terminal VDD. An input capacitor Cin is connected between the ground terminal GND and the power input terminal VDD.

  An inductor L is connected between the power input terminal VDD and the switch terminal SW. That is, one end of the inductor L is connected to the power input terminal VDD, and the other end of the inductor L is connected to the switch terminal SW.

An output capacitor Cout is connected between the power supply output terminal VOUT and the ground terminal GND. A DC output voltage Vout higher than the DC input voltage V _DD is generated between both ends of the output capacitor Cout.

  Between the power output terminal VOUT and the feedback terminal FB, the first to fourth light emitting diodes LED1, LED2, LED3, LED4 used as a backlight of the liquid crystal display device are connected in series. A resistor R is connected between the feedback terminal FB and the ground terminal GND. That is, in this example, the first to fourth light emitting diodes LED1 to LED4 and the resistor R are provided as loads.

In this example, the power supply input voltage V _DD of the input power supply is 3.7V. In addition, in order to cause the first to fourth light emitting diodes LED1 to LED4 to emit light, it is necessary to apply a voltage of 3.3 V to each light emitting diode, and a voltage of 0.5 V is applied to both ends of the resistor R. Need to be done. Therefore, the DC output voltage Vout generated across the output capacitor Cout is 13.7V. Since this example shows an example in which the number of light emitting diodes is four, the DC output voltage Vout is 13.7 V. However, when the number of light emitting diodes is three, the direct current output The voltage Vout is 10.4V.

  FIG. 2 shows a block diagram of the step-up synchronous rectification DC / DC converter 10 shown in FIG.

  The step-up synchronous rectification DC / DC converter 10 includes a first transistor Q1 connected between the switch terminal SW and the power supply output terminal VOUT, and a second transistor connected between the switch terminal SW and the ground terminal GND. A transistor Q2. The first transistor Q1 is called a rectifying transistor, and the second transistor Q2 is called a switching transistor. The first transistor Q1 has first and second main electrode terminals and a first control terminal. The second transistor Q2 has third and fourth main electrode terminals and a second control terminal.

  More specifically, the illustrated first transistor Q1 is a P-channel field effect transistor having a drain, a source, and a gate as a first main electrode terminal, a second main electrode terminal, and a first control terminal, respectively. It is composed of The illustrated second transistor Q2 is composed of an N-channel field effect transistor having a drain, a source, and a gate as a third main electrode terminal, a fourth main electrode terminal, and a second control terminal, respectively. Has been. In the P-channel field effect transistor Q1, its drain is connected to the switch terminal SW (the other end of the inductor L), and its source is connected to the power supply output terminal VOUT. In the N-channel field effect transistor Q2, its drain is connected to the switch terminal SW (the other end of the inductor L), and its source is connected to the ground terminal GND through the resistor R1.

  Instead of the P-channel field effect transistor, the first transistor Q1 has a collector, an emitter, and a base as a first main electrode terminal, a second main electrode terminal, and a first control terminal, respectively. You may comprise from a pnp-type bipolar transistor. Instead of the N-channel field effect transistor, the second transistor Q2 is an npn type having a collector, an emitter, and a base as a third main electrode terminal, a fourth main electrode terminal, and a second control terminal, respectively. You may comprise from a bipolar transistor.

  These P-channel field effect transistor Q1 and N-channel field effect transistor Q2 are driven by a drive circuit described later.

  More specifically, the drive circuit includes a reference voltage generation circuit 11, an error amplifier 12, a pulse width modulation (PWM) comparator 13, a current mode comparator 14, an oscillator 15, an adder 16, and a drive control circuit. 17.

  The reference voltage generation circuit 11 is connected between the power input terminal VDD and the ground terminal, and generates a reference voltage Vref. The output terminal of the reference voltage generation circuit 11 is grounded via resistors R2 and R3 connected in series. The connection point between the resistors R2 and R3 is connected to the non-inverting input terminal + of the error amplifier 12. The inverting input terminal − of the error amplifier 12 is connected to the feedback terminal FB. The output terminal of the error amplifier 12 is grounded through a resistor Rc and a capacitor Cc. The output terminal of the error amplifier 12 is connected to the input terminal − of the PWM comparator 13.

  A resistor R 1 is connected between the non-inverting input terminal + and the inverting input terminal − of the current mode comparator 14. The oscillator 15 oscillates a sawtooth wave. The output terminal of the oscillator 15 and the output terminal of the current mode comparator 14 are connected to the adder 16. The adder 16 adds the output signal of the current mode comparator 14 and the output signal of the oscillator 15 and outputs the added signal. The output terminal of the adder 16 is connected to the non-inverting input terminal + of the PWM comparator 13. The PWM comparator 13 outputs a pulse width modulation signal. The output terminal of the PWM comparator 13 is connected to the drive control circuit 17. Based on the pulse width modulation signal supplied from the PWM comparator 13, the drive control circuit 17 prevents the P-channel field effect transistor Q1 and the N-channel field effect transistor Q2 from being turned on at the same time. Controls the driving of the channel field effect transistor Q2.

  In any case, the driving circuit drives the P-channel field effect transistor Q1 and the N-channel field effect transistor Q2 so that the P-channel field effect transistor Q1 and the N-channel field effect transistor Q2 are not turned on at the same time.

  On the other hand, an ON / OFF signal is supplied to the control terminal CNTRL. The control terminal CNTRL is grounded via resistors R4 and R5. The connection point of the resistors R4 and R5 is connected to the gate of the N-channel field effect transistor Q3. The drain of the N-channel field effect transistor Q3 is connected to the power supply input terminal via the current source 18, and the source is grounded.

  A soft start circuit 19 is connected to the output terminal of the reference voltage generation circuit 11, and an open circuit protection circuit 20 is connected to the power supply output terminal VOUT.

  FIG. 3 shows a conventional step-up synchronous rectification DC / DC converter shown together with the output stage of the conventional drive control circuit 17. In FIG. 3, reference numeral 25 is an input power source.

  The drive control circuit 17 has a first comparator 171 and a second comparator 172 at its output stage. The first comparator 171 is for supplying a first control voltage to the gate of the P-channel field effect transistor Q1. The second comparator 172 is for supplying a second control voltage to the gate of the N-channel field effect transistor Q2.

  The first comparator 171 functions as first control voltage generation means for generating a voltage swung between the power supply output voltage Vout and the ground potential as the first control voltage. Similarly, the second comparator 172 functions as second control voltage generation means for generating a voltage swung between the power supply output voltage Vout and the ground potential as the second control voltage.

In general, in the step-up type synchronous rectification DC / DC converter, the parasitic capacitances of the P-channel field effect transistor Q1 and the N-channel field effect transistor Q2 which are power transistors are large. That, P channel field effect transistor Q1, as a parasitic capacitance, the gate - drain capacitance _{C 11} and the gate - with the source capacitance _{C 12.} Similarly, the N-channel field effect transistor Q2, as a parasitic capacitance, the gate - drain capacitance C ₂₁ and the gate - with the source capacitance C _22.

  As described above, in the conventional step-up synchronous rectification DC / DC converter, in order to drive the P-channel field effect transistor Q1, the first comparator 171 uses the power supply output voltage Vout as the first control voltage. In order to generate the voltage swung between the ground potential and the N-channel field effect transistor Q2, the second comparator 171 uses the power supply output voltage Vout and the ground potential as the second control voltage. Generated a voltage that was swung between.

In this case, the charge (Q = CV) for driving the parasitic capacitances C _{11 to} C ₂₂ is large, and the power loss at the time of switching the P-channel field effect transistor Q1 and the N-channel field effect transistor Q2 becomes so large that it cannot be ignored.

  Accordingly, an object of the present invention is to provide a step-up DC / DC converter and a driving method thereof that can reduce power loss during switching.

  A step-up DC / DC converter to which the present invention is applied has a ground terminal (GND) having a ground potential and a power input terminal (VDD), and a DC input voltage (VDD) is applied between the ground terminal and the power input terminal. An input power supply (25) to be applied, an inductor (L) having one end connected to the power input terminal, a first main electrode terminal connected to the other end of the inductor, and a second main electrode terminal serving as a power output terminal And a first transistor (Q1) having a first control terminal to which a first control voltage is supplied, a third main electrode terminal connected to the other end of the inductor, and a fourth main electrode terminal Is connected between the power supply output terminal and the ground terminal, and is connected between both ends of the second transistor (Q2) having the second control terminal to which the second control voltage is supplied. DC output voltage (Vout) higher than DC input voltage Driving circuits (11, 12, 13, 14, 15, 16, 17A to drive the first and second transistors so that the generated output capacitor (Cout) and the first and second transistors are not turned on simultaneously. 17E).

According to the step-up DC / DC converter according to the first aspect of the present invention, the drive circuit (17A) has a direct current output voltage (Vout) and a direct current input voltage (V _DD ) as the first control voltage. The first control voltage generating means (171A) for generating the voltage swung in (1).

According to the step-up DC / DC converter according to the second aspect of the present invention, the drive circuit (17B) is swung between the ground potential and the DC input voltage (V _DD ) as the second control voltage. Second control voltage generating means (172A) for generating a voltage is included.

According to the step-up DC / DC converter according to the third aspect of the present invention, the drive circuit (17C) has a direct current output voltage (Vout) and a direct current input voltage (V _DD ) as the first control voltage. The first control voltage generation means (171A) that generates the voltage swung in step 171 and the second control voltage that generates a voltage swung between the ground potential and the DC input voltage (V _DD ) as the second control voltage. Control voltage generating means (172A).

According to the step-up DC / DC converter according to the fourth aspect of the present invention, the drive circuit (17D) uses the first transistor (DC output voltage (Vout)) higher than the DC output voltage (Vout) and the ground potential as the first control voltage. First control voltage generating means (171B) for generating a voltage swung between the first set voltage (V _GS1 ) sufficient to turn on Q1) and a ground potential as a second control voltage And a second control voltage generating means for generating a voltage swung between the second set voltage (V _GS2 ) lower than the DC output voltage (Vout) and sufficient to turn on the second transistor (Q2). 172B). The first set voltage and the second set voltage may be equal (V _GS ). Further, the first and second set voltages (VGS) may be equal to half the DC output voltage (Vout).

  In the step-up DC / DC converter, the first transistor (Q1) includes, for example, a drain, a source, and a gate as a first main electrode terminal, a second main electrode terminal, and a first control terminal, respectively. The second transistor (Q2) includes, for example, a drain, a source, a third main electrode terminal, a fourth main electrode terminal, and a second control terminal, respectively. And an N-channel field effect transistor having a gate. Instead, the first transistor is composed of a pnp bipolar transistor having a collector, an emitter, and a base as the first main electrode terminal, the second main electrode terminal, and the first control terminal, respectively. The second transistor may be composed of an npn bipolar transistor having a collector, an emitter, and a base as a third main electrode terminal, a fourth main electrode terminal, and a second control terminal, respectively.

Further, the driving method of the step-up DC / DC converter to which the present invention is applied has a ground terminal (GND) having a ground potential and a power input terminal (VDD), and a DC input is provided between the ground terminal and the power input terminal. An input power supply (25) for applying a voltage (V _DD ), an inductor (L) having one end connected to the power supply input terminal, a first main electrode terminal connected to the other end of the inductor, and a second main electrode A first transistor (Q1) having a first control terminal to which the electrode terminal is connected to a power supply output terminal and supplied with a first control voltage; and a third main electrode terminal is connected to the other end of the inductor; The fourth main electrode terminal is connected to the ground terminal, and the second transistor (Q2) having the second control terminal to which the second control voltage is supplied is connected between the power output terminal and the ground terminal. DC output higher than the DC input voltage across In a step-up DC / DC converter having an output capacitor (Cout) for generating a voltage (Vout), the first and second transistors are driven so that the first and second transistors are not turned on simultaneously. .

The step-up DC / DC converter driving method according to the first aspect of the present invention uses a voltage swung between a DC output voltage (Vout) and a DC input voltage (V _DD ) as the first control voltage. It is characterized by that.

The step-up DC / DC converter driving method according to the second aspect of the present invention is characterized in that a voltage swung between a ground potential and a DC input voltage (V _DD ) is used as the second control voltage. To do.

The step-up DC / DC converter driving method according to the third aspect of the present invention uses a voltage swung between the DC output voltage (Vout) and the DC input voltage (V _DD ) as the first control voltage. As the second control voltage, a voltage swung between the ground potential and the DC input voltage (V _DD ) is used.

The step-up DC / DC converter driving method according to the fourth aspect of the present invention is used to turn on the first transistor (Q1) which is higher than the DC output voltage (Vout) and the ground voltage as the first control voltage. A voltage swung between the first set voltage (V _GS1 ) and a sufficient first set voltage (V _GS1 ) is used, and the second control voltage is lower than the ground potential and the DC output voltage (Vout) and the second transistor (Q 2) is turned on. It is characterized in that a voltage swung between the second set voltage (V _GS2 ) which is sufficient for the _purpose is used. The first set voltage and the second set voltage may be equal (V _GS ). Further, the first and second set voltages (V _GS ) may be equal to half the voltage of the DC output voltage (Vout).

  In addition, the code | symbol in the said parenthesis is attached | subjected in order to make an understanding of this invention easy, and it is only an example, and of course is not limited to these.

  In the present invention, since the first and second transistors are driven by a control voltage that swings in a narrower range than the range between the ground potential and the power supply output voltage, power loss during switching can be reduced. There is an effect.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  With reference to FIG. 4, a step-up synchronous rectification DC / DC converter according to a first embodiment of the present invention will be described. The illustrated step-up synchronous rectification DC / DC converter has the same configuration as that of the conventional step-up synchronous rectification DC / DC converter illustrated in FIG. 3 except that the configuration of the drive control circuit is changed as will be described later. Have the same operation. Therefore, the reference numeral 17A is attached to the drive control circuit. Also, components having the same functions as those shown in FIG. 3 are denoted by the same reference numerals, and description thereof is omitted for the sake of simplicity.

  The drive control circuit 17A has the same configuration as the drive control circuit 17 shown in FIG. 3 and operates similarly except that the configuration of the first comparator is changed. Therefore, the reference numeral 171A is assigned to the first comparator.

The first comparator 171A generates a voltage swung between the DC output voltage Vout and the DC input voltage V _DD as the first control voltage.

As a result, when driving the P-channel field effect transistor Q1, the charge to drive the parasitic capacitance _{C 11, C 12,} less the _{C (11, 12)} Vout to _{C (11,12) (Vout-V} DD) It is possible to reduce power loss during switching.

  With reference to FIG. 5, a step-up synchronous rectification DC / DC converter according to a second embodiment of the present invention will be described. The illustrated step-up synchronous rectification DC / DC converter has the same configuration as the conventional step-up synchronous rectification DC / DC converter shown in FIG. 3 except that the configuration of the drive control circuit is changed as will be described later. Have the same operation. Therefore, the reference numeral 17B is given to the drive control circuit. Also, components having the same functions as those shown in FIG. 3 are denoted by the same reference numerals, and description thereof is omitted for the sake of simplicity.

  The drive control circuit 17B has the same configuration as the drive control circuit 17 shown in FIG. 3 and operates similarly except that the configuration of the second comparator is changed. Therefore, the reference numeral 172A is attached to the second comparator.

The second comparator 172A generates a voltage swung between the ground potential and the DC input voltage V _DD as the second control voltage.

As a result, when driving the N-channel field effect transistor Q2, the charge for driving the parasitic capacitors C ₂₁ and C ₂₂ can be reduced from C _{(21, 22)} Vout to C _{(21, 22)} V _DD. The power loss at the time of switching can be reduced.

  With reference to FIG. 6, a step-up synchronous rectification DC / DC converter according to a third embodiment of the present invention will be described. The illustrated step-up synchronous rectification DC / DC converter has the same configuration as that of the conventional step-up synchronous rectification DC / DC converter illustrated in FIG. 3 except that the configuration of the drive control circuit is changed as will be described later. Have the same operation. Therefore, the reference numeral 17C is attached to the drive control circuit. Also, components having the same functions as those shown in FIG. 3 are denoted by the same reference numerals, and description thereof is omitted for the sake of simplicity.

  The drive control circuit 17C includes a first comparator 171A and a second comparator 172A instead of the first comparator 171 and the second comparator 172.

As a result, when driving the P-channel field effect transistor Q1, the charge to drive the parasitic capacitance _{C 11, C 12,} less the _{C (11, 12)} Vout to _{C (11,12) (Vout-V} DD) The power loss during switching can be reduced, and when driving the N-channel field effect transistor Q2, the charges for driving the parasitic capacitances C ₂₁ and C ₂₂ are changed to C _{(21, 22)} Vout. Can be reduced from C _{(21, 22)} V _DD to reduce power loss during switching.

  A step-up synchronous rectification DC / DC converter according to a fourth embodiment of the present invention will be described with reference to FIG. The illustrated step-up synchronous rectification DC / DC converter has the same configuration as the conventional step-up synchronous rectification DC / DC converter shown in FIG. 3 except that the configuration of the drive control circuit is changed as will be described later. Have the same operation. Therefore, the reference numeral 17D is attached to the drive control circuit. Also, components having the same functions as those shown in FIG. 3 are denoted by the same reference numerals, and description thereof is omitted for the sake of simplicity.

  The drive control circuit 17D has the same configuration as that of the drive control circuit 17 shown in FIG. 3 and operates similarly except that the configurations of the first and second comparators are changed. Accordingly, reference numerals 171B and 172B are assigned to the first comparator and the second comparator, respectively.

The first comparator 171B swings between the DC output voltage Vout and the first set voltage V _GS1 higher than the ground potential and sufficient to turn on the P-channel field effect transistor Q1 as the first control voltage. Generate the voltage. The second comparator 172B swung between the second set voltage V _GS2 which is lower than the ground potential and the DC output voltage Vout and is sufficient to turn on the N-channel field effect transistor Q2 as the second control voltage. Generate voltage.

In other words, the control of the P-channel field effect transistor Q1 and the N-channel voltage effect transistor Q2 is performed so that the gate-source voltage V _{G-S (min)} can be suppressed so that the on-resistance r _on is kept low. And the voltage range of the second comparators 171B and 172B.

FIG. 8 illustrates the relationship between the gate-source voltage V _GS and the on-resistance r _on in the P-channel field effect transistor Q1 and the N-channel field effect transistor Q2. 8, the ON resistance r _on the gate - a maximum when the source voltage V _G-S is zero, the gate - becomes abruptly smaller as the source voltage V _G-S is increased from zero, a certain voltage It turns out that it becomes small only gradually above.

Therefore, for the P-channel field effect transistor Q1, the differential voltage (Vout−V _GS1 ) between the power supply output voltage Vout and the first set voltage V _GS1 is set to a voltage that reduces the on-resistance r _on. For the channel field effect transistor Q2, the second set voltage V _GS2 is set to a voltage at which the on-resistance r _on becomes small. FIG. 8 shows an example in which the difference voltage (Vout−V _GS1 ) is equal to the second set voltage V _GS2 .

Conventionally, the first and second control voltage, the gate - a had been swung in the range of source voltage V _G-S is zero and Vout (the range indicated by A in FIG. 8), the present embodiment Then, the swing is performed in a narrower range (a range indicated by B0 in FIG. 8).

As a result, when driving the P-channel field effect transistor Q1, the charge to drive the parasitic capacitance _{C 11, C 12,} less the _{C (11, 12)} Vout to _{C (11,12) (Vout-V} GS1) The power loss during switching can be reduced, and when driving the N-channel field effect transistor Q2, the charges for driving the parasitic capacitances C ₂₁ and C ₂₂ are changed to C _{(21, 22)} Vout. To C _{(21, 22)} V _GS2 , and power loss during switching can be reduced.

  With reference to FIG. 9, a step-up synchronous rectification DC / DC converter according to a fifth embodiment of the present invention will be described. The boosting synchronous rectification DC / DC converter shown in the figure has the same configuration as that of the boosting synchronous rectification DC / DC converter shown in FIG. 7 except that the configuration of the drive control circuit is changed as will be described later. , Do the same. Therefore, the reference numeral 17E is attached to the drive control circuit.

The drive control circuit 17E includes the drive control circuit 17D shown in FIG. 7 except that the first set voltage for the first comparator is equal to the second set voltage for the second comparator. It has the same configuration and performs the same operation. Accordingly, reference numerals 171C and 172C are assigned to the first comparator and the second comparator, respectively, and equal (common) set voltages are indicated by V _GS .

  That is, the step-up synchronous rectification DC / DC converter according to the fifth embodiment of the present invention is a special example of the step-up synchronous rectification DC / DC converter according to the fourth embodiment shown in FIG. Example).

FIG. 10 illustrates the relationship between the gate-source voltage V _GS and the on-resistance r _on in the P-channel field effect transistor Q1 and the N-channel field effect transistor Q2 similar to FIG. In this example, the set voltage V _GS is set to a half voltage of the DC output voltage Vout (V _GS = Vout / 2).

Conventionally, the first and second control voltage, the gate - a had been swung in the range of source voltage V _G-S is zero and Vout (the range indicated by A in FIG. 10), the present embodiment Then, the swing is performed in a narrower range (a range indicated by B1 in FIG. 10).

  Next, the power loss during switching between the conventional step-up synchronous rectification DC / DC converter (FIG. 3) and the step-up synchronous rectification DC / DC converter (FIG. 9) according to the fifth embodiment of the present invention is compared. To do.

In the conventional step-up synchronous rectification DC / DC converter, the charge Q ₁ that drives the parasitic capacitances C _{11 to} C ₂₂ at the time of switching is represented by Q ₁ = C _{(11 to 22)} × Vout. On the other hand, in the step-up synchronous rectification DC / DC converter according to the fifth embodiment of the present invention, the charge Q ₂ that drives the parasitic capacitors C _{11 to} C ₂₂ during switching is Q ₂ = C _{(11 to 11 22)} It is represented by × _VGS . Therefore, the charge component ΔQ of the power loss that can be reduced is ΔQ = Q ₁ −Q ₂ = C _(11-22) × (Vout−V _GS ) = C _(11-22) × ΔV _GS .

For example, if the power supply output voltage Vout is Vout = 10V and the set voltage _VGS is _VGS = 5V, the charge loss ΔQ of the power loss that can be reduced is ΔQ = 5 × C _(11-22) (C). Become. That is, the power loss can be reduced by 50% compared to the conventional case.

In the step-up type synchronous rectification DC / DC converter shown in FIG. 9, the set voltage V _GS equal to the power supply input voltage V _DD is the step-up type synchronous synthesizer according to the third embodiment of the present invention shown in FIG. It is a rectification DC / DC converter.

FIG. 11 shows an example of a circuit for generating the first set voltage V _GS1 necessary for the first comparator 171B shown in FIG. The circuit for generating the first set voltage V _GS1 shown in the figure is a clamp circuit.

  The clamp circuit includes a clamp transistor Q3, a Zener diode D1, and a resistor R6. The clamp transistor Q3 is composed of a P-channel field effect transistor. The substrate of the clamp transistor Q3 is connected to the power output terminal VOUT. The drain of the clamp transistor Q3 is connected to the gate of the first transistor Q1, and is connected to the power supply output terminal VOUT via the P-channel field effect transistor Q4. The source of the clamp transistor Q3 is connected to the ground terminal GND via the N-channel field effect transistor Q5.

  The gate of the P-channel field effect transistor Q4 is connected to the output terminal of the inverter INV1. The gate of the N-channel field effect transistor Q5 is also connected to the output terminal of the inverter INV1.

  The gate of the clamp transistor Q3 is connected to the power supply output terminal VOUT through the Zener diode D1, and is connected to the ground terminal GND through the resistor R6.

When the gate voltage of the first transistor Q1 becomes equal to or less than Vout−V _Z + V _T (V _Z : Zener voltage of the Zener diode D1, V _T : Gate-source voltage of the clamp transistor Q3), the clamp transistor Q3 is turned off. For this reason, the gate voltage of the first transistor Q1 does not drop below Vout−V _Z + V _T.

FIG. 12 shows an example of a circuit for generating the second set voltage V _GS2 necessary for the second comparator 172B shown in FIG. The circuit for generating the second set voltage V _GS2 shown in the figure is composed of a regulator.

  The illustrated regulator includes a pnp bipolar transistor Tr, a comparator 27, bleeder resistors R7 and R8, and a capacitor C1.

  The emitter of the pnp bipolar transistor Tr is connected to the power supply output terminal VOUT, and the collector is connected to the regulator output terminal 30. Bleeder resistors R7 and R8 are connected in series between the regulator output terminal 30 and the ground terminal GND. A capacitor C1 is connected between the regulator output terminal 30 and the ground terminal GND. The connection point between the bleeder resistors R7 and R8 is connected to the inverting input terminal − of the comparator 27. The non-inverting input terminal + of the comparator 27 is connected to the ground terminal GND through the Zener diode D2. The output terminal of the comparator 27 is connected to the base of the pnp bipolar transistor Tr.

According to such a configuration, the second set voltage V _GS2 is held between both ends of the capacitor C1.

  In the example shown in FIG. 12, the emitter of the pnp bipolar transistor Tr is connected to the power supply output terminal VOUT, but may be connected to the power supply input terminal VDD.

  Although the present invention has been described above with reference to preferred embodiments, it is needless to say that the present invention is not limited to the above-described embodiments. For example, in the above-described embodiment, only the case where the first and second transistors are configured by field effect transistors has been described, but the first and second transistors may be configured by bipolar transistors. .

It is a block diagram which shows the external appearance of the pressure | voltage rise type synchronous rectification DC / DC converter to which this invention is applied. FIG. 2 is a block diagram of the step-up type synchronous rectification DC / DC converter illustrated in FIG. 1. It is a block diagram which shows the structure of the conventional step-up type synchronous rectification DC / DC converter. It is a block diagram which shows the structure of the step-up type synchronous rectification DC / DC converter by the 1st Embodiment of this invention. It is a block diagram which shows the structure of the step-up type synchronous rectification DC / DC converter by the 2nd Embodiment of this invention. It is a block diagram which shows the structure of the step-up type synchronous rectification DC / DC converter by the 3rd Embodiment of this invention. It is a block diagram which shows the structure of the step-up type synchronous rectification DC / DC converter by the 4th Embodiment of this invention. It is a figure which shows the relationship between the gate-source voltage and on-resistance in a field effect transistor. It is a block diagram which shows the structure of the step-up type synchronous rectification DC / DC converter by the 5th Embodiment of this invention. It is a figure which shows the relationship between the gate-source voltage and on-resistance in a field effect transistor. FIG. 8 is a circuit diagram illustrating an example of a circuit for generating a first set voltage necessary for the first comparator illustrated in FIG. 7. FIG. 8 is a circuit diagram illustrating an example of a circuit for generating a second set voltage necessary for the second comparator illustrated in FIG. 7.

Explanation of symbols

Q1 first transistor (P-channel field effect transistor)
Q2 Second transistor (N-channel field effect transistor)
L inductor 25 input power source Cout output capacitor V _DD power source input voltage Vout power source output voltage C ₁₁ , C ₁₂ , C ₂₁ , C ₂₂ parasitic capacitance 17A to 17E drive control circuit 171A to 171C first comparator 172A to 172C second Comparator

Claims (16)

An input power source having a ground terminal of a ground potential and a power input terminal, and applying a DC input voltage between the ground terminal and the power input terminal;
An inductor having one end connected to the power input terminal;
A first transistor having a first control terminal to which the first main electrode terminal is connected to the other end of the inductor, a second main electrode terminal is connected to the power supply output terminal, and a first control voltage is supplied. When,
A second transistor having a second control terminal connected to the other end of the inductor, a third main electrode terminal connected to the ground terminal, and a fourth control electrode supplied with a second control voltage. When,
An output capacitor connected between the power supply output terminal and the ground terminal and generating a DC output voltage higher than the DC input voltage between both ends;
In a step-up DC / DC converter provided with a drive circuit for driving the first and second transistors so that the first and second transistors are not turned on simultaneously,
The drive circuit includes first control voltage generation means for generating a voltage swung between the DC output voltage and the DC input voltage as the first control voltage. / DC converter. An input power source having a ground terminal of a ground potential and a power input terminal, and applying a DC input voltage between the ground terminal and the power input terminal;
An inductor having one end connected to the power input terminal;
A first transistor having a first control terminal to which the first main electrode terminal is connected to the other end of the inductor, a second main electrode terminal is connected to the power supply output terminal, and a first control voltage is supplied. When,
A second transistor having a second control terminal to which the third main electrode terminal is connected to the other end of the inductor, a fourth main electrode terminal is connected to the ground terminal, and a second control voltage is supplied. When,
An output capacitor connected between the power supply output terminal and the ground terminal and generating a DC output voltage higher than the DC input voltage between both ends;
In a step-up DC / DC converter provided with a drive circuit for driving the first and second transistors so that the first and second transistors are not turned on simultaneously,
The drive circuit includes second control voltage generation means for generating a voltage swung between the ground potential and the DC input voltage as the second control voltage. DC converter. An input power source having a ground terminal of a ground potential and a power input terminal, and applying a DC input voltage between the ground terminal and the power input terminal;
An inductor having one end connected to the power input terminal;
A first transistor having a first control terminal to which the first main electrode terminal is connected to the other end of the inductor, a second main electrode terminal is connected to the power supply output terminal, and a first control voltage is supplied. When,
A second transistor having a second control terminal to which the third main electrode terminal is connected to the other end of the inductor, a fourth main electrode terminal is connected to the ground terminal, and a second control voltage is supplied. When,
An output capacitor connected between the power supply output terminal and the ground terminal and generating a DC output voltage higher than the DC input voltage between both ends;
In a step-up DC / DC converter provided with a drive circuit for driving the first and second transistors so that the first and second transistors are not turned on simultaneously,
The drive circuit includes, as the first control voltage, first control voltage generation means that generates a voltage swung between the DC output voltage and the DC input voltage, and the second control voltage, A step-up DC / DC converter comprising second control voltage generation means for generating a voltage swung between the ground potential and the DC input voltage. An input power source having a ground terminal of a ground potential and a power input terminal, and applying a DC input voltage between the ground terminal and the power input terminal;
An inductor having one end connected to the power input terminal;
A first transistor having a first control terminal to which the first main electrode terminal is connected to the other end of the inductor, a second main electrode terminal is connected to the power supply output terminal, and a first control voltage is supplied. When,
A second transistor having a second control terminal connected to the other end of the inductor, a third main electrode terminal connected to the ground terminal, and a fourth control electrode supplied with a second control voltage. When,
An output capacitor connected between the power supply output terminal and the ground terminal and generating a DC output voltage higher than the DC input voltage between both ends;
In a step-up DC / DC converter provided with a drive circuit for driving the first and second transistors so that the first and second transistors are not turned on simultaneously,
The first transistor comprises a P-channel field effect transistor having a drain, a source, and a gate as the first main electrode terminal, the second main electrode terminal, and the first control terminal,
The second transistor is composed of an N-channel field effect transistor having a drain, a source, and a gate as the third main electrode terminal, the fourth main electrode terminal, and the second control terminal,
The drive circuit swings, as the first control voltage, a voltage swung between the DC output voltage and a first set voltage higher than the ground potential and sufficient to turn on the first transistor. Swing between the first control voltage generating means to generate and the second control voltage as the second control voltage between the ground potential and a second set voltage lower than the DC output voltage and sufficient to turn on the second transistor A step-up DC / DC converter comprising: a second control voltage generation unit configured to generate the generated voltage. An input power source having a ground terminal of a ground potential and a power input terminal, and applying a DC input voltage between the ground terminal and the power input terminal;
An inductor having one end connected to the power input terminal;
A first transistor having a first control terminal to which the first main electrode terminal is connected to the other end of the inductor, a second main electrode terminal is connected to the power supply output terminal, and a first control voltage is supplied. When,
A second transistor having a second control terminal connected to the other end of the inductor, a third main electrode terminal connected to the ground terminal, and a fourth control electrode supplied with a second control voltage. When,
An output capacitor connected between the power supply output terminal and the ground terminal and generating a DC output voltage higher than the DC input voltage between both ends;
In a step-up DC / DC converter provided with a drive circuit for driving the first and second transistors so that the first and second transistors are not turned on simultaneously,
The first transistor includes a pnp bipolar transistor having a collector, an emitter, and a base as the first main electrode terminal, the second main electrode terminal, and the first control terminal,
The second transistor is composed of an npn bipolar transistor having a collector, an emitter, and a base as the third main electrode terminal, the fourth main electrode terminal, and the second control terminal,
The drive circuit swings, as the first control voltage, a voltage swung between the DC output voltage and a first set voltage higher than the ground potential and sufficient to turn on the first transistor. Swing between the first control voltage generation means to generate and the second control voltage as the second control voltage between the ground potential and a second set voltage lower than the DC output voltage and sufficient to turn on the second transistor A step-up DC / DC converter comprising: a second control voltage generation unit configured to generate the generated voltage. 6. The step-up DC / DC converter according to claim 4, wherein the first set voltage and the second set voltage are equal. An input power source having a ground terminal of a ground potential and a power input terminal, and applying a DC input voltage between the ground terminal and the power input terminal;
An inductor having one end connected to the power input terminal;
A first transistor having a first control terminal to which the first main electrode terminal is connected to the other end of the inductor, a second main electrode terminal is connected to the power supply output terminal, and a first control voltage is supplied. When,
A second transistor having a second control terminal connected to the other end of the inductor, a third main electrode terminal connected to the ground terminal, and a fourth control electrode supplied with a second control voltage. When,
An output capacitor connected between the power supply output terminal and the ground terminal and generating a DC output voltage higher than the DC input voltage between both ends;
In a step-up DC / DC converter provided with a drive circuit for driving the first and second transistors so that the first and second transistors are not turned on simultaneously,
The drive circuit swings, as the first control voltage, a voltage swung between the DC output voltage and a first set voltage higher than the ground potential and sufficient to turn on the first transistor. Swing between the first control voltage generating means to generate and the second control voltage as the second control voltage between the ground potential and a second set voltage lower than the DC output voltage and sufficient to turn on the second transistor Second control voltage generation means for generating the generated voltage,
The first set voltage and the second set voltage are equal,
It said first and said second temperature pressure-type DC / DC converter you wherein the setting voltage is equal to half the voltage of the DC output voltage. The first transistor comprises a P-channel field effect transistor having a drain, a source, and a gate as the first main electrode terminal, the second main electrode terminal, and the first control terminal,
The second transistor is an N-channel field effect transistor having a drain, a source, and a gate as the third main electrode terminal, the fourth main electrode terminal, and the second control terminal, respectively. The step-up DC / DC converter according to any one of claims 1 to 3 . The first transistor includes a pnp bipolar transistor having a collector, an emitter, and a base as the first main electrode terminal, the second main electrode terminal, and the first control terminal,
Said second transistor, said third main electrode terminal, the fourth main electrode terminal, and a second control terminal, respectively, and the collector, emitter, and the npn type bipolar transistor having a base, wherein Item 4. The step-up DC / DC converter according to any one of Items 1 to 3 . An input power source having a ground terminal of a ground potential and a power input terminal, and applying a DC input voltage between the ground terminal and the power input terminal, an inductor having one end connected to the power input terminal, and the inductor A first transistor having a first control terminal connected to a first main electrode terminal, a second main electrode terminal connected to a power supply output terminal, and a first control voltage supplied thereto; A second transistor having a second control terminal connected to the other end of the inductor, a third main electrode terminal connected to the ground terminal, and a fourth control electrode supplied with a second control voltage. And a step-up DC / DC converter having an output capacitor connected between the power supply output terminal and the ground terminal and generating a DC output voltage higher than the DC input voltage between both ends. And said Transistors so as not to turn on at the same time, a method of driving the first and the second transistor,
A method of driving a step-up DC / DC converter, wherein a voltage swung between the DC output voltage and the DC input voltage is used as the first control voltage. An input power source having a ground terminal of a ground potential and a power input terminal, and applying a DC input voltage between the ground terminal and the power input terminal, an inductor having one end connected to the power input terminal, and the inductor A first transistor having a first control terminal connected to a first main electrode terminal, a second main electrode terminal connected to a power supply output terminal, and a first control voltage supplied thereto; A second transistor having a second control terminal connected to the other end of the inductor, a third main electrode terminal connected to the ground terminal, and a fourth control electrode supplied with a second control voltage. And a step-up DC / DC converter having an output capacitor connected between the power supply output terminal and the ground terminal and generating a DC output voltage higher than the DC input voltage between both ends. And said Transistors so as not to turn on at the same time, a method of driving the first and the second transistor,
A method of driving a step-up DC / DC converter, wherein a voltage swung between the ground potential and the DC input voltage is used as the second control voltage. An input power source having a ground terminal of a ground potential and a power input terminal, and applying a DC input voltage between the ground terminal and the power input terminal, an inductor having one end connected to the power input terminal, and the inductor A first transistor having a first control terminal connected to a first main electrode terminal, a second main electrode terminal connected to a power supply output terminal, and a first control voltage supplied thereto; A second transistor having a second control terminal connected to the other end of the inductor, a third main electrode terminal connected to the ground terminal, and a fourth control electrode supplied with a second control voltage. And a step-up DC / DC converter having an output capacitor connected between the power supply output terminal and the ground terminal and generating a DC output voltage higher than the DC input voltage between both ends. And said Transistors so as not to turn on at the same time, a method of driving the first and the second transistor,
A voltage swung between the DC output voltage and the DC input voltage is used as the first control voltage, and a swing is performed between the ground potential and the DC input voltage as the second control voltage. A method of driving a step-up DC / DC converter, characterized by using a different voltage. An input power source having a ground terminal of a ground potential and a power input terminal, and applying a DC input voltage between the ground terminal and the power input terminal, an inductor having one end connected to the power input terminal, and the inductor A first transistor having a first control terminal connected to a first main electrode terminal, a second main electrode terminal connected to a power supply output terminal, and a first control voltage supplied thereto; A second transistor having a second control terminal connected to the other end of the inductor, a third main electrode terminal connected to the ground terminal, and a fourth control electrode supplied with a second control voltage. And a step-up DC / DC converter having an output capacitor connected between the power supply output terminal and the ground terminal and generating a DC output voltage higher than the DC input voltage between both ends. And said Transistors so as not to turn on at the same time, a method of driving the first and the second transistor,
The first transistor comprises a P-channel field effect transistor having a drain, a source, and a gate as the first main electrode terminal, the second main electrode terminal, and the first control terminal,
The second transistor is composed of an N-channel field effect transistor having a drain, a source, and a gate as the third main electrode terminal, the fourth main electrode terminal, and the second control terminal,
As the first control voltage, a voltage swung between the DC output voltage and a first set voltage that is higher than the ground voltage and sufficient to turn on the first transistor is used. As the control voltage, a voltage that is swung between the ground potential and a second set voltage that is lower than the DC output voltage and sufficient to turn on the second transistor is used. DC converter drive method. An input power source having a ground terminal of a ground potential and a power input terminal, and applying a DC input voltage between the ground terminal and the power input terminal, an inductor having one end connected to the power input terminal, and the inductor A first transistor having a first control terminal connected to a first main electrode terminal, a second main electrode terminal connected to a power supply output terminal, and a first control voltage supplied thereto; A second transistor having a second control terminal connected to the other end of the inductor, a third main electrode terminal connected to the ground terminal, and a fourth control electrode supplied with a second control voltage. And a step-up DC / DC converter having an output capacitor connected between the power supply output terminal and the ground terminal and generating a DC output voltage higher than the DC input voltage between both ends. And said Transistors so as not to turn on at the same time, a method of driving the first and the second transistor,
The first transistor includes a pnp bipolar transistor having a collector, an emitter, and a base as the first main electrode terminal, the second main electrode terminal, and the first control terminal,
The second transistor is composed of an npn bipolar transistor having a collector, an emitter, and a base as the third main electrode terminal, the fourth main electrode terminal, and the second control terminal,
As the first control voltage, a voltage swung between the DC output voltage and a first set voltage that is higher than the ground voltage and sufficient to turn on the first transistor is used. As the control voltage, a voltage that is swung between the ground potential and a second set voltage that is lower than the DC output voltage and sufficient to turn on the second transistor is used. DC converter drive method. The method of driving a step-up DC / DC converter according to claim 13 or 14 , wherein the first set voltage is equal to the second set voltage. An input power source having a ground terminal of a ground potential and a power input terminal, and applying a DC input voltage between the ground terminal and the power input terminal, an inductor having one end connected to the power input terminal, and the inductor A first transistor having a first control terminal connected to a first main electrode terminal, a second main electrode terminal connected to a power supply output terminal, and a first control voltage supplied thereto; A second transistor having a second control terminal connected to the other end of the inductor, a third main electrode terminal connected to the ground terminal, and a fourth control electrode supplied with a second control voltage. And a step-up DC / DC converter having an output capacitor connected between the power supply output terminal and the ground terminal and generating a DC output voltage higher than the DC input voltage between both ends. And said Transistors so as not to turn on at the same time, a method of driving the first and the second transistor,
As the first control voltage, a voltage swung between the DC output voltage and a first set voltage that is higher than the ground voltage and sufficient to turn on the first transistor is used. As a control voltage, a voltage swung between the ground potential and a second set voltage lower than the DC output voltage and sufficient to turn on the second transistor is used.
The first set voltage and the second set voltage are equal,
Wherein the first and elevated pressure type DC / DC converter driving way to, characterized in that equal the second setting voltage is half the voltage of the DC output voltage.

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