JP2000102244A - Dc-to-dc converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To supply the larger of either an input DC voltage or an output DC voltage to a boosting circuit and to reduce the minimum operating voltage by supplying the power supply voltage of the power supply line of the boosting circuit form an input DC voltage before boosting of operation, and taking a power supply voltage from the output DC voltage after boosting of operation. SOLUTION: An input DC voltage Vin and an output DC voltage Vout, after starting a boosting circuit 20, are compared. Then, before a boosting operation, where the input DC voltage Vin on comparison is larger than the output DC voltage Vout, the input DC voltage Vin is supplied to a power supply line L for supplying the operating power of a circuit in a DC/DC converter 10, including the boosting circuit 20, thus activating the circuit of the DC/DC converter 10. Furthermore, after the boosting operation, the output DC voltage Vout is supplied to the power supply line L, instead of the input DC voltage Vin, and the boosting operation of the boosting circuit and that of the circuit of the DC/DC converter 10 are allowed made to continue, thus expanding the margin at the constant-voltage side of the input DC voltage Vin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device, and more particularly, to a step-up DC / DC having a step-up circuit for stepping up an input DC voltage and outputting a predetermined DC voltage.
About converter.

[0002]

2. Description of the Related Art Conventionally, as this type of DC / DC converter (switching power supply circuit), for example,
Japanese Unexamined Patent Application Publication No. 60291/1990 (see FIG. 4).

That is, in a switching power supply circuit,
Input terminal 1 and switching element Q ₁Control times to drive
Power supply input terminal V of path 3_ccCapacitor C between_ThreeIs connected
When the switching power supply is started,
From the DC input supplied to the power supply circuit to the control circuit 3.
Densa C_ThreePower is supplied via the. Also external DC
Capacitor C between input terminal 1 connected to the power supply and ground
₁And the input terminal 1 is connected to the primary of the transformer T.
Winding N₁Is connected to one end. Primary winding of transformer T
Line N₁The other end is a MOSFET type switching transistor.
Star Q₁Connected to ground via drain and source terminals
Have been. Switching transistor Q₁The gate is
It is connected to the output terminal of the control circuit 3. Control circuit 3
Voltage power supply V_ccCapacitor C between terminal and input terminal 1_ThreeAnd da
Iod D_TwoAre connected in parallel, and the GND of the control circuit 3
Terminal is connected to earth. At this time, the diode D
_TwoIs an anode on the input terminal 1 side and a cathode on the control circuit 3 side.
And One end of the secondary winding N2 of the transformer T is
Iod D₁And the other end is connected to ground.
Has been continued. Diode D₁Output terminal 2
Is connected to Output terminal 2 (output voltage V_O) And ar
Smoothing capacitor C_TwoIs connected, and the smoothing
Densa C_TwoResistance R in parallel with₁, R_TwoSeries circuit
Has been continued. Resistance R₁, Resistance R_TwoIs the control circuit 3
To the resistor R₁, R_TwoThe output voltage divided by
It is input to the control circuit 3. Tertiary winding N of transformer T
_ThreeIs connected to the ground, and the other end is a diode D_ThreeNo
Connected to the node. At this time, the primary winding of the transformer T
Line N₁Switching transistor Q₁The drain side of the
Diode D of secondary winding N2₁The anode side of
ing. Diode D_ThreeIs the voltage of the control circuit 3
Power supply V_ccConnected to terminal. Switching power supply circuit
Then, the control power supply V_ccIs supplied. S
When starting the switching power supply,
Input voltage V_INIs applied to the input terminal 1 at that moment.
Input terminal 1, capacitor C_Three, Control circuit 3, ground
Current i_c3Flows and the capacitor C_ThreeCharge. Con
Due to the nature of the capacitor, the input voltage V_INUnfilled immediately after
In the charged state, the capacitor C_ThreePotential difference between both ends is zero
And the charging current i_c3Creates a potential difference over time
And it gets higher. That is, the input voltage V_INThrow
Immediately after turning on, the power input terminal V of the control circuit 3_ccEnter the
Voltage V_INIs supplied almost as is. This input voltage V_IN
The control circuit 3 is activated by the_INWith amplitude of
Pulse voltage is the switching transistor Q₁Game
And the switching transistor Q₁Is activated,
The switching power supply starts operating. Therefore, the switch
Input voltage V at which the switching power supply can start_INThe voltage value of
Almost switching transistor Q₁Threshold voltage (V
_TH) Can be in the vicinity, and compared to conventional circuits,
Low input voltage V_INVoltage can be set low
It is described. On the other hand, the switching power supply
At the beginning, a voltage is induced in the secondary winding N2 of the transformer T.
To supply DC power to the load,_ThreeAlso
Voltage V_ThreeOccurs. Diode D_TwoThe forward drop voltage of
V_F2, Diode D_ThreeIs the forward drop voltage of V_F3And
Pressure V_ThreeIs (V_Three-V_F3)> (V_IN-V_F2)
Tertiary winding N_ThreeVoltage V_ThreeIs Daio
Do D_Three(Forward voltage drop V_F3Rectified by
Capacitor C_Three, Capacitor C₁Smoothed and complemented
The power supply of the control circuit 3 is turned on as the output voltage VS of the auxiliary power supply circuit 4.
Force terminal V_cc(= V_Three-V_F3). This
The control circuit 3 supplies power from the auxiliary power supply circuit 4 (supply voltage =
V_Three-V_F3), And the voltage value of the voltage VS
Is the input voltage V_INAt a higher voltage than at startup.
Switching transistor Q₁Are driven. So
Therefore, the switching transistor Q₁On resistance
Lower than during operation, switching in steady operation after startup
Transistor Q₁Power loss. On the other hand,
Pressure V_INBecomes higher, and (V_IN-V_F2)> (V_Three-V_F3)When
The control circuit 3 is connected to an external DC power supply.
Input voltage V_INPower supply from
Input voltage V_INThe power supply for driving the control circuit 3 depends on the magnitude of
Will automatically select the higher voltage
Has been described.

[0004]

SUMMARY OF THE INVENTION Such a conventional switch is
In the switching power supply circuit, the voltage V_ThreeIs (V_Three-V_F3)> (V
_IN-V_F2), The tertiary winding N_ThreeTo
Generated voltage V_ThreeIs the diode D_ThreeRectified by
And capacitor C_Three, Capacitor C₁Smoothed by
The output voltage Vs of the auxiliary power supply circuit 4 is V_Three-V_F3The size of
Is the power input terminal V of the control circuit 3._ccEntered in
You. Also, (V_IN-V_F2)> (V_Three-V_F3) Relationship
Before the boost operation in (V)_IN-V_F2)> (V_Three−
V_F3), The external DC power supply
Input voltage V_INTo V_IN-V_F2V_F2Only V_INThan
Is supplied to the control circuit 3. I
However, in the switching power supply circuit, the power supply voltage
Of the power supply input terminal V_ccOf supply voltage to
V_F2The minimum operating voltage of the control circuit 3 is also low in accordance with the drop due to
Although it is necessary to use a MOS transistor constituting the control circuit 3,
Since the minimum operable voltage of the transistor is limited,
The minimum operating voltage of the circuit 3 cannot be reduced without limit.
No. Therefore, when lowering the power supply voltage,
Omit the voltage drop due to the forward voltage of the ion as much as possible.
However, in conventional switching power supply circuits,
Omit the voltage drop due to the forward voltage of the
There was a technical challenge that was difficult.

An object of the present invention is to solve such a conventional problem. In particular, an output DC voltage (power supply voltage of a booster circuit) before a boost operation is applied to an output terminal of a DC / DC converter. Is connected to supply the load current to the load, the load current also flows to the external diode, so that the output DC voltage drops by the forward voltage of the diode and the output DC voltage (ie, It is an object of the present invention to avoid the case where the power supply voltage of the circuit becomes (input DC voltage−forward voltage) and supply the booster circuit with a larger voltage of the input DC voltage or the output DC voltage. Another object of the present invention is to reduce the boosting operation start voltage by avoiding the case where the power supply voltage of the booster circuit before the boosting operation drops by the forward voltage of the diode. And

[0006]

Means for Solving the Problems The invention according to claim 1 has been made to solve the above problems (see FIGS. 2 and 1).
Is a DC / DC converter (1) provided with a booster circuit for boosting an input DC voltage and outputting it as a predetermined DC voltage.
0), the voltage values of the input DC voltage and the output DC voltage after the start-up of the booster circuit are compared, and the operating power of the booster circuit is increased before the boosting operation in which the input DC voltage is larger than the output DC voltage. The input DC voltage is supplied to the power supply line to be supplied to start the booster circuit, and after the boosting operation in which the output DC voltage is equal to or higher than the input DC voltage, the power supply line of the booster circuit is replaced with the input DC voltage. A DC / DC converter having a power supply switching means (12) for supplying an output DC voltage and continuing the boosting operation of the booster circuit.

According to the first aspect of the invention, the power supply voltage of the power supply line of the booster circuit is supplied from the input DC voltage before the boosting operation, and the power supply voltage is obtained from the output DC voltage after the boosting operation. Will be able to As a result, even when the output DC voltage (power supply voltage of the booster circuit) before the boosting operation is supplied to the load by connecting the load to the output terminal of the DC / DC converter, the load current is supplied to the external device. A case where the output DC voltage drops by the forward voltage of the diode because the current also flows through the diode, and the output DC voltage (that is, the power supply voltage of the booster circuit) becomes (input DC voltage−forward voltage). Can be avoided, and a larger voltage of the input DC voltage and the output DC voltage can be supplied to the booster circuit.

As a result, the DC / DC converter can be operated even with an input DC voltage lower by the forward voltage of the diode. As a result, the constant voltage side margin of the input DC voltage can be increased. The minimum operating voltage can be reduced.

The invention according to claim 2 (see FIG. 1)
Is a DC / DC converter according to claim 1,
A voltage comparison unit configured to compare a voltage value between the input DC voltage and the output DC voltage after the start-up of the booster circuit to generate a switching signal; A power supply voltage switch (16) for supplying a higher voltage of the input DC voltage or the output DC voltage to a power supply line for supplying operating power of the booster circuit based on a signal to execute a boosting operation of the booster circuit And a DC / DC converter having a configuration including:

According to the second aspect of the present invention, the first aspect is provided.
In addition to the effects described in the above, the power supply voltage switch supplies a larger voltage of the input DC voltage or the output DC voltage to the power supply line that supplies the operating power of the booster circuit, based on the switching signal, so that the booster circuit Before the boosting operation, the power supply voltage of the power supply line can be supplied from the input DC voltage, and after the boosting operation, the power supply voltage can be obtained from the output DC voltage. As a result, even when the output DC voltage (power supply voltage of the booster circuit) before the boosting operation is supplied to the load by connecting the load to the output terminal of the DC / DC converter, the load current is supplied to the external device. Since the output DC voltage drops by the forward voltage of the diode because the current also flows through the diode, the case where the power supply voltage of the booster circuit becomes (input DC voltage−forward voltage) can be avoided. A higher voltage of the input DC voltage or the output DC voltage can be supplied to the booster circuit.

The invention according to claim 3 (see FIG. 1).
Is a DC / DC converter according to claim 2,
The power supply voltage switch (16) supplies the input DC voltage to the power supply line when activated and cuts off the supply of the input DC voltage to the power supply line when inactive. ) And supplying the output DC voltage to the power supply line when activated and interrupting the supply of the output DC voltage to the power supply line when inactive.
A second MOSFET (162) of a conductivity type;
A DC / DC converter having a back gate bias circuit (164) for applying a larger voltage of the input DC voltage and the output DC voltage to a back gate of an OSFET and a back gate of the second MOSFET.

According to the invention described in claim 3, according to claim 2,
In addition to the effects described in the above, the back gate bias circuit,
Backgate of first MOSFET and second MOSFET
Of the input DC voltage or the output DC voltage, whichever is greater, is applied to the back gate of the first MOS.
When the FET is active, the input DC voltage is supplied to the power supply line, and when the FET is inactive, the supply of the input DC voltage to the power supply line is cut off.
At the same time, the second MOSFET supplies the output DC voltage to the power supply line when activated, and cuts off the supply of the output DC voltage to the power supply line when inactive. Thus, the power supply voltage of the power supply line of the booster circuit can be supplied from the input DC voltage before the boosting operation, and can be obtained from the output DC voltage after the boosting operation. As a result, even when the output DC voltage (power supply voltage of the booster circuit) before the boosting operation is supplied to the load by connecting the load to the output terminal of the DC / DC converter, the load current is supplied to the external device. A case where the output DC voltage drops by the forward voltage of the diode because the current also flows through the diode, and the output DC voltage (that is, the power supply voltage of the booster circuit) becomes (input DC voltage−forward voltage). Can be avoided, and a larger voltage of the input DC voltage and the output DC voltage can be supplied to the booster circuit.

The invention according to claim 4 (see FIG. 1).
Is the DC / DC converter according to claim 3,
The back gate bias circuit (164) is provided with the first gate circuit.
The back gate of the MOSFET (161) and the second M
A first diode (1641) having a cathode connected to the back gate of the OSFET (162) and an anode connected to the input DC voltage;
ET (161) back gate and the second MOSFE
A second diode (1642) having a cathode connected to the back gate of T (162) and an anode connected to the output DC voltage, wherein the input DC voltage is greater than the output DC voltage; , The first diode (1641) is activated, and the second diode (1642) is inactivated.
Back gate of T (161) and said second MOSFET
When the input DC voltage is applied to the back gate of (162) and the output DC voltage is higher than the input DC voltage, the second diode (1642) is activated and the first diode (1641) Are inactivated, and the DC / DC converter is configured to apply the output DC voltage to the back gate of the first MOSFET (161) and the back gate of the second MOSFET (162).

According to the invention described in claim 4, according to claim 3,
In addition to the effects described in the above, when the input DC voltage is higher than the output DC voltage, the first diode is activated, the second diode is deactivated, and the first MOSFET is deactivated.
When an input DC voltage is applied to the back gate of the second MOSFET and the back gate of the second MOSFET, and the output DC voltage is higher than the input DC voltage, the second diode is activated and the first diode is inactivated, 1st MOSF
Since the output DC voltage is applied to the back gate of the ET and the back gate of the second MOSFET, the larger voltage of the input DC voltage or the output DC voltage is applied to the back gate of the first MOSFET and the back gate of the second MOSFET. When the first MOSFET is activated, the input DC voltage is supplied to the power supply line. When the first MOSFET is inactive, the supply of the input DC voltage to the power supply line is cut off.
The ET can supply the output DC voltage to the power supply line when activated and cut off the supply of the output DC voltage to the power supply line when inactive.

Thus, the power supply voltage of the power supply line of the booster circuit is supplied from the input DC voltage before the boosting operation,
After the boosting operation, the power supply voltage can be obtained from the output DC voltage. As a result, the output DC voltage (power supply voltage of the boosting circuit) before the boosting operation becomes DC
Even when a load is connected to the output terminal of the / DC converter and a load current is supplied to the load, the output DC voltage drops by the forward voltage of the diode because the load current also flows to the external diode. As a result, it is possible to avoid the case where the output DC voltage (that is, the power supply voltage of the booster circuit) becomes (input DC voltage−forward voltage), and the larger of the input DC voltage and the output DC voltage is reduced. The voltage can be supplied to the booster circuit.

The invention according to claim 5 (see FIG. 1).
Is a DC / DC according to any one of claims 2 to 4.
In the converter, when the input DC voltage is higher than the output DC voltage, the voltage comparison unit (14) uses a first gate signal having a signal level that activates the first MOSFET (161) as the switching signal. A voltage is applied to the gate of the first MOSFET and the second
A second gate signal having a signal level for inactivating the MOSFET (162) is used as the switching signal as the second gate signal.
Applied to the gate of the MOSFET, and when the output DC voltage is larger than the input DC voltage,
The second gate signal having a signal level for activating the SFET (162) is used as the switching signal and the second M
The first MOS is applied to the gate of the OSFET.
A first gate signal having a signal level for inactivating the FET (161) is used as the switching signal as the first MOS transistor.
This is a DC / DC converter having a configuration having a logic circuit (142) applied to the gate of the FET.

According to the invention set forth in claim 5, according to claim 2,
In addition to the effects described in any one of (4) to (4), when the input DC voltage is higher than the output DC voltage, the logic circuit uses a first gate signal of a signal level that activates the first MOSFET as a switching signal. The second diode is applied to the gate of the first MOSFET, and a second gate signal having a signal level for inactivating the second MOSFET is applied to the gate of the second MOSFET as a switching signal, so that the first diode is activated and the second diode is activated. The diode is deactivated and the back gate of the first MOSFET and the second MO
An input DC voltage can be applied to the back gate of the SFET.

When the output DC voltage is higher than the input DC voltage, the logic circuit applies a second gate signal having a signal level for activating the second MOSFET to the gate of the second MOSFET as a switching signal, and 1
Since a first gate signal having a signal level for inactivating the MOSFET is applied to the gate of the first MOSFET as a switching signal, the second diode is activated, the first diode is inactivated, and the first MOSFET is activated.
The output DC voltage can be applied to the back gate of the second MOSFET and the back gate of the second MOSFET.

As a result, the input DC voltage or the output DC voltage, whichever is larger, is applied to the back gate of the first MOSFET and the back gate of the second MOSFET, and accordingly, when the first MOSFET is activated, the input DC voltage is applied to the power supply line. When the power supply is inactive, the supply of the input DC voltage to the power supply line is cut off. At the same time, the second MOSFET can supply the output DC voltage to the power supply line when activated, and can cut off the supply of the output DC voltage to the power supply line when inactive. Become like

Thus, the power supply voltage of the power supply line of the booster circuit is supplied from the input DC voltage before the boosting operation,
After the boosting operation, the power supply voltage can be obtained from the output DC voltage.

[0021]

DC / DC converter 10 [OF THE PREFERRED EMBODIMENTS OF THE INVENTION] The present embodiment is an embodiment of a power supply IC, and boosts the DC voltage input from an external power source such as a battery (the input DC voltage V _in) Step-up DC / DC provided with a step-up circuit 20 that outputs a predetermined DC voltage (output DC voltage V _out )
A converter, compares the voltage value of the input DC voltage V _in and the output DC voltage V _out after the startup of the booster circuit 20, the input DC voltage V _in of the comparison is the output DC voltage V _out of the comparison boosting operation before is large, the step-up circuit 20 within the DC / DC converter 10, including a step-up circuit 20 supplies the input DC voltage V _in the power supply line L for supplying operating power of the circuit in the DC / DC converter 10 including Has the function of activating the circuit.

Furthermore Additionally DC / DC converter 10 of the present embodiment compares the voltage value of the input DC voltage V _in and the output DC voltage V _out after the startup of the booster circuit 20, the output DC voltage V _out is after boosting operation as an input DC voltage V _in above, supplied in place of the input DC voltage V _in the output DC voltage V _out to the power supply line L for supplying operating power of the circuit in the DC / DC converter 10 including a boost circuit 20 Booster circuit 2
It has a function of continuing the step-up operation of 0 and the operation of the circuit in the DC / DC converter 10.

FIG. 1 shows a power supply switching means 1 according to the present invention.
FIG. 4 is a circuit diagram for explaining one embodiment of the present invention.

The power supply switching means 12 for realizing such a function is integrated in the DC / DC converter 10,
As shown in FIG. 1, the hardware configuration is centered on a voltage comparison unit 14 and a power supply voltage switch 16.

The voltage comparator 14 is integrated in the DC / DC converter 10, a switching signal 12a by comparing the voltage value of the input DC voltage V _in when starting subsequent booster circuit 20 and the output DC voltage V _out It has a function of generating, as shown in FIG. 1, a comparator 143, resistance elements R ₁ , R ₂ ,
The hardware configuration is centered on R ₃ , R ₄ and the logic circuit 142.

Resistance element R₁, R_TwoIs a DC / DC converter
Integrated in the data 10 and connected in series
Voltage V_inConnected between the ground potential GND. Resistance element
Child R ₁And resistance element R_TwoVoltage (= V_in・ R
_Two/ (R₁+ R_Two) Is the minus of the comparator 143
(-) Connected to input terminal.

The resistance elements R ₃ and R ₄ are integrated in the DC / DC converter 10 and connected between the output DC voltage V _out and the ground potential GND in a state of being connected in series. The divided voltage (= V _{out) at} the connection point between the resistance elements R ₃ and R ₄
(R ₄ / (R ₃ + R ₄ )) is connected to the plus (+) input terminal of the comparator 143. In the present embodiment, the ratio (= R ₁ / R ₂ ) between the resistance element R ₁ and the resistance element R ₂ is equal to the ratio (= R ₃ / R ₄ ) between the L resistance element R ₃ and the resistance element R ₄ ( That is, R ₁ / R ₂ = R ₃ / R ₄ ) is set.

The comparator 143 is integrated in the DC / DC converter 10, is supplied with operating power from a power supply line L, and receives a divided voltage (= V _in · R ₂ /) input to a minus (-) input terminal. (R ₁ + R ₂ )) and plus (+)
The divided voltage (= V _out · R ₄ / (R ₃
+ R ₄ )), and outputs the comparison result as a comparison logical value signal.

[0029] More specifically, the minus (-) the divided voltage input to the input terminal _{(= V in · R 2 /} (R 1 + R 2)) is,
The divided voltage (= V _out ) input to the plus (+) input terminal
When it is larger than R ₄ / (R ₃ + R ₄ )), the logical value L is output as a comparison logical value signal, while the divided voltage (= V _out · R ₄ /) input to the plus (+) input terminal is output. (R ₃ +
R ₄ )) is larger than the divided voltage (= V _in · R ₂ / (R ₁ + R ₂ )) input to the minus (−) input terminal, the logic value H is output as a comparison logic value signal. .

The logic circuit 142 is a DC / DC converter
10 and the input DC voltage V _inIs the output DC voltage V
_outIs larger than the first p-channel MOS described later.
The first gate having a signal level for activating the FET 161
Signal 142a as the switching signal 12a in the first p channel.
To the gate of the MOSFET 161 and
Inactivates the second p-channel MOSFET 162 described below.
Switch the second gate signal 142b at a signal level such as
The second p-channel MOSFET 162
And the output DC voltage V_outIs directly input
Current voltage V_inLarger than the second p-channel MOSF
Second gate of signal level to activate ET162
The signal 142b is used as the switching signal 12a in the second p-channel.
To the gate of the MOSFET 162 and the first
A signal that inactivates the p-channel MOSFET 161
The first gate signal 142a at the signal level
a as the gate of the first p-channel MOSFET 161
And a power supply line L as shown in FIG.
Logic elements NOT1 to which operating power is supplied from
421 and 1422 are the hardware configuration.
ing.

The logic element NOT1421 is integrated in the DC / DC converter 10, generates a second gate signal 142b by logically inverting the comparison logical value signal, and uses the second gate signal 142b as the switching signal 12a. 2p
Applied to the gate of the channel MOSFET 162. In the following description, the second gate signal 142b will be referred to as a second gate logic signal 142b.

The logic element NOT 1422 is integrated in the DC / DC converter 10 and has a second gate logic signal 142
b is logically inverted to generate a first gate signal 142a, and the first gate signal 142a is applied to the gate of the first p-channel MOSFET 161 as the switching signal 12a. In the following description, the first gate signal 142a will be referred to as a first gate logic signal 142a.

[0033] Thus, the logic circuit 142 when the input DC voltage V _in is greater than the output DC voltage V _out, first
The first gate logic signal 142a having a signal level for activating the p-channel MOSFET 161 is switched to the switching signal 1
2a is applied to the gate of the first p-channel MOSFET 161 and the second p-channel MOSFET 162
Of the second p-channel M as a switching signal 12a using a second gate logic signal 142b having a signal level that inactivates
Since the voltage is applied to the gate of the OSFET 162, a first Schottky diode 1641 described later is activated, and a second Schottky diode 1642 described later is deactivated, so that the back gate of the first p-channel MOSFET 161 and the second p-channel MOSFET 162 It will be able to apply the input DC voltage V _in to the back gate.

The logic circuit 142 outputs the output DC voltage V
If _out is greater than the input DC voltage V _in, and applies to the gate of the 2p channel MOSFET162 the first 2p channel MOSFET162 as a second gate logic signal 142b switching signal 12a of the signal level so as to activate the 1p channel A first gate logic signal 142 having a signal level for inactivating the MOSFET 161
a as the switching signal 12a, the first p-channel MOSF
Since the voltage is applied to the gate of the ET 161, the second Schottky diode 1642 is activated, the first Schottky diode 1641 is inactivated, and the output is applied to the back gate of the first p-channel MOSFET 161 and the back gate of the second p-channel MOSFET 162. DC voltage _Vout can be applied.

As a result, the first p-channel MOSFET 1
61 back gate and second p-channel MOSFET 1
Any large voltage input DC voltage V _in and the output DC voltage V _out 62 of the back gate is applied, in response to this, the 1p channel MOSFET161 supplies the input DC voltage V _in when the active power line L not cut off the supply of the power supply line L of the input DC voltage V _in the active time, at the same time the power supply line of the 2p channel MOSFET162 is, to provide an output DC voltage V _out to the power line L to the active during inactive time on the output DC voltage V _out The supply to L can be cut off. Here, the voltage of the back gate of the first 1p channel MOSFET161 the 2p channel MOSFET162 must provide a voltage of higher either V _in or V _out. If taken the first 1p channel MOSFET161 each source potential of the back gate of the 2p channel MOSFET 162, when V _out voltage is higher than V _{i n} voltage p-channel MOSFET 162 is turned ON. At this time, the current, as shown in FIG. 5, connect with V _dd from V _out terminal through a p-channel MOSFET, V _dd is because it leads the V _in via the parasitic diode 1, thereby a current flows in the route . In other words, if the step-up to V _out is higher than V _in voltage causes an invalid current is generated in this pathway. Conversely, V _in voltage becomes V _out
If the voltage is higher than the voltage, the p-channel MOSFET 161
The state becomes the N state. At this time, the current leads and V _dd via a p-channel MOSFET from V _in terminal, since V _dd is thus a current flows in this path for leading V _out through the parasitic diode 2, the internal V by a current value There is a possibility that the voltage of _dd drops by the ON resistance of the p-channel MOSFET. By connecting the back gates of the p-channel MOSFETs 161 and 162 via diodes in order to prevent such a phenomenon, it is possible to eliminate the occurrence of the parasitic diodes 1 and 2 and to block the flow of the above-mentioned invalid current. be able to. Here, the diode that gives the back gate potential can be manufactured by using a Schottky barrier diode that makes a metal come into contact with N-WELL as shown in FIG. 6, for example.

Thus, the DC / D including the boosting circuit 20
Before boosting operation of the power supply voltage V _dd of the power supply line L for supplying the operating power of the circuit C converter 10 is supplied from the input DC voltage V _in, take the supply voltage from the output DC voltage V _out is after boosting operation Will be able to do so.

On the other hand, the power supply voltage switch 16 has a DC / D
Integrated into C converter 10, based on the switching signal 12a, the input DC voltage V _in and the output DC voltage V _out
Out of the DC voltage including the booster circuit 20
The voltage is supplied to a power supply line L that supplies operating power of a circuit in the DC / DC converter 10 and the boosting operation of the boosting circuit 20 and the DC / DC
It has a function to execute the operation of the circuit in the DC converter 10. That is, when the input DC voltage V _in is greater than the output DC voltage V _out is supplied to the power supply line L for supplying operating power of the circuit in the DC / DC converter 10, including a step-up circuit 20 the input DC voltage V _{i n} Booster circuit 20
To execute the operation of the circuit of the step-up operation or DC / DC converter 10 in a similar spirit, when the output DC voltage V _out is greater than the input DC voltage V _in, the output DC voltage V _out
Is supplied to a power supply line L that supplies operating power of a circuit in the DC / DC converter 10 including the booster circuit 20 to execute the boosting operation of the booster circuit 20 and the operation of the circuit in the DC / DC converter 10.

As shown in FIG. 1, the power supply voltage switch 16 for realizing such a function is a first conductive type first MOS.
FET 161, first conductivity type second MOSFET 162,
It has a hardware configuration centered on the back gate bias circuit 164. In the present embodiment, the first conductive type first MOSFET 161 and the first conductive type second MOSF
ET162 is connected to a p-channel MOSF as shown in FIG.
It consists of ET. In the following description, the first conductive type first MOSFET 161 is referred to as the first p-channel MOSFET 1
61, the second MOSFET 162 is replaced by a second p-channel MOS
Let us call it FET162.

The first p-channel MOSFET 161 has a D
Integrated in the C / DC converter 10 and activated (ON
Provides an input DC voltage V _in the power line L in time), also has a function of cutting off the supply to the power line L of the input DC voltage V _in during inactive (during OFF), as shown in FIG. 1 To
Source connected to the input DC voltage V _in, drain is connected to the power line L, a gate, a first logic circuit 142
It is connected to the output terminal of the gate logic signal 142a.

The second p-channel MOSFET 162 has a D
Integrated into C / DC converter 10, and supplies the output DC voltage V _out to the power line L to the active time, also has the function of cutting off the supply to the power supply line L of the output DC voltage V _out when inactive, FIG. 1, the source is connected to the output DC voltage _Vout , the drain is connected to the power supply line L, and the gate is connected to the second gate logic signal 1 of the logic circuit 142.
42b is connected to the output terminal.

The back gate bias circuit 164 has the first
The back gate of the p-channel MOSFET 161 and the second
the back gate of p-channel MOSFET162 has a function of applying either large voltage input DC voltage V _in and the output DC voltage V _out, as shown in FIG. 1, a central first diode 1641, the second diode 1642 Hardware configuration.

The first diode 1641 is integrated in the DC / DC converter 10, and as shown in FIG. 1, the cathode of the first diode 1641 is connected to the back gate of the first p-channel MOSFET 161 and the back gate of the second p-channel MOSFET 162. There are connected, and further addition, connected to the anode of the first diode 1641 is input DC voltage V _in. In the present embodiment, a Schottky diode is used as the first diode 1641. In the following description, the first diode 1641 will be referred to as a first Schottky diode 1641.

The second diode 1642 is integrated in the DC / DC converter 10 and has a first p-channel MOSFET.
Back gate of T161 and second p-channel MOSFE
The cathode of the second diode 1642 is connected to the back gate of T162, and in addition, the second diode 164
2 are connected to the output DC voltage _Vout .
In the present embodiment, a Schottky diode is used as the second diode 1642.

[0044] In the back gate bias circuit 164 of the configuration of such a circuit, the input DC voltage when V _in is greater than the output DC voltage V _out at the same time when the first Schottky diode 1641 is activated second Schottky diode 1642 is inactivated. As a result, the input DC voltage V _in is applied to the back gate of the back gate and the 2p channel MOSFET162 of the 1p channel MOSFET 161. In response to this, the supply to the first 1p channel MOSFET161 is activated to supply the input DC voltage V _in the power line L, at the same time the power supply line L of the 2p channel MOSFET162 is inactivated by the output DC voltage V _out Cut off.

For the same purpose, the output DC voltage V_outIs input
DC voltage V_inIf greater than the second Schottky
The first shot is activated at the same time when the diode 1642 is activated.
The toky diode 1641 is deactivated. This
And the back gate of the first p-channel MOSFET 161
And back gate of second p-channel MOSFET 162
Output DC voltage V_outIs applied. to this
Accordingly, second p-channel MOSFET 162 is activated.
Output DC voltage V_outTo the power line L,
First, the first p-channel MOSFET 161 is inactivated.
Input DC voltage V _inOf the power supply line L is shut off.

Thus, the DC / D including the boosting circuit 20
Before boosting operation of the power supply voltage V _dd of the power supply line L for supplying the operating power of the circuit C converter 10 is supplied from the input DC voltage V _in, take the supply voltage from the output DC voltage V _out is after boosting operation Will be able to do so. As a result, the output DC voltage V before the boost operation is performed.
_Even when the load (the power supply voltage of the booster circuit 20) is connected to the output terminal of the DC / DC converter 10 and the load current is supplied to the load, the load current flows to the external diode. forward voltage of only the output DC voltage V _out is lowered to cause the output DC voltage V _out (i.e., the power supply voltage of the booster circuit 20) (input DC voltage V _in -
Will be able to avoid cases like becomes forward voltage), the input DC voltage V _in and the output DC voltage V
Any voltage larger than _out can be supplied to the booster circuit 20.

FIG. 2 shows the power supply switching means 12 of FIG.
FIG. 2 is a circuit diagram for explaining a DC / DC converter 10 including a circuit and an external circuit.

The DC / DC converter 10 is externally provided with a diode D for rectification, a capacitor C _ext for smoothing, a reactance L _ext for boosting, an external power supply 30 and the like.

[0049] The input DC voltage V _in to input terminal L _x, the external power source 30 through a reactance L _ext boosting
Positive terminal is connected.

[0050] In the diode D for rectification, the anode is connected to the terminal L _x, the cathode is connected to the terminal of the output DC voltage V _out.

Terminal of output DC voltage _Vout- ground potential GN
A smoothing capacitor C _ext and a load RL are connected between the terminals of D. The GND terminal is connected to the ground potential GND.

[0052] to the terminal L _x, of the reactance L _ext the other end,
Anode of diode D for rectification, reactance L _ext
A driving power MOSFET Q ₁ (integrated in the DC / DC converter 10) is connected. Driver element Q ₂ is connected to the gate of the power MOSFET Q ₁ of the reactance L _ext drive.

As the external power supply 30, a lithium ion battery, a nickel cadmium battery or the like can be used.

FIG. 3 shows the DC / DC converter 10 of FIG.
4 is a graph for explaining a transient characteristic of the output DC voltage _Vout of FIG.

The above-described DC / DC converter 10 is similar to that shown in FIG.
As shown in, it compares the voltage value of the input DC voltage V _in and the output DC voltage V _out of _the startup and subsequent step-up circuit 20 (t> 0), output when the input DC voltage V _in of the comparison is compared Before the boosting operation larger than the DC voltage _Vout (0 <t <t ₁ ),
Input DC operating power of the circuit in the DC / DC converter 10 including a boost circuit 20 to the power line L to supply voltage V _in
DC / DC converter 1 including booster circuit 20
Start the circuit in 0.

[0056] step-up operation before (0 <t <t _1, the external power source 3 power MOSFET Q ₁ of the reactance L _{e xt} drive that is connected to the power line L to the period during which the ON control
The energy supplied from 0 is converted into a reactance L for boosting.
accumulated in _ext, power for driving the reactance L _ext MOS
By charging (charging current i) in the capacitor C _ext for smoothing the energy through the diode D of the rectifying the FETs Q ₁ in the period being OFF control is accumulated in the boosting reactance L _ext, the external power source 30 Can be generated on the terminal side of the output DC voltage _Vout . The load RL would energy charged in the capacitor C _ext for smoothing (output DC voltage V _{o ut,} current i _out is supplied.

In addition, the DC / DC converter 10
Input DC voltage V after start-up of booster circuit 20 (t> 0)
comparing the voltage value of the _in the output DC voltage V _out, after boosting operation in which the output DC voltage V _out is input DC voltage V _in more _{(t> t 1), DC} / DC converter 10 including a boost circuit 20 the output DC voltage V _out to the power supply line L for supplying operating power of the circuit of the inner input DC voltage is supplied in place of the V _in boost operation or DC / DC converter 10 of the booster circuit 20
The operation of the circuit inside is continued.

After the boost operation (t> t)₁), Output DC voltage V
_outReactance L connected to _extPower for driving
MOSFET Q₁External power supply 3 during the ON control of
The energy supplied from 0 is converted into a reactance L for boosting.
_extAnd reactance L_extPower MOS for driving
FETQ₁Reactor for boosting during the period when OFF is controlled
Lance_extDie for rectifying the energy stored in the
Capacitor C for smoothing via diode D_extCharge (charge)
Current i), the voltage of the external power supply 30 is boosted.
Output voltage to output DC voltage V_outGenerated on the terminal side of
Can be. The load RL includes a smoothing capacitor C_extTo
Energy being charged (output DC voltage V_{o ut}, Current
i_outWill be supplied.

As described above, according to the present embodiment, the power supply voltage V _dd of the power supply line L that supplies the operating power of the circuits in the DC / DC converter 10 including the booster circuit 20.
The in the previous step-up operation is supplied from the input DC voltage V _in,
After the boost operation, the power supply voltage can be obtained from the output DC voltage _Vout . as a result,
Even if the output DC voltage V _out (power supply voltage of the booster circuit 20) before the boosting operation supplies the load current to the load by connecting the load to the output terminal of the DC / DC converter 10, the load current becomes The output DC voltage V _out drops by the forward voltage of the diode because it also flows through the attached diode, and the output DC voltage V _out (that is, the booster circuit 20
Power supply voltage) (the input DC voltage V _in - forward voltage) and the case now to be avoided as it becomes, the input DC voltage V _in, or any greater voltage boosting circuits output DC voltage V _out 20 Can be supplied to

[0060] As a result, the forward voltage of only low input DC voltage V _in any DC / DC converter 10 of the diode
Will be able to operate, as a result, it is possible to widen the margin of the constant voltage side of the input DC voltage V _in, it is possible to lower the minimum operating voltage.

[0061]

According to the DC / DC converter according to the present invention, the power supply voltage of the power supply line of the booster circuit is supplied from the input DC voltage before the boosting operation, and the power supply voltage is converted from the output DC voltage after the boosting operation. You will be able to take. As a result, even when the output DC voltage (power supply voltage of the booster circuit) before the boosting operation is supplied to the load by connecting the load to the output terminal of the DC / DC converter, the load current is supplied to the external device. A case where the output DC voltage drops by the forward voltage of the diode because the current also flows through the diode, and the output DC voltage (that is, the power supply voltage of the booster circuit) becomes (input DC voltage−forward voltage). Can be avoided, and a larger voltage of the input DC voltage and the output DC voltage can be supplied to the booster circuit.

As a result, the DC / DC converter can be operated even with the input DC voltage lower by the forward voltage of the diode, and as a result, the constant voltage side margin of the input DC voltage can be expanded. The minimum operating voltage can be reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram for explaining an embodiment of a power supply switching means of the present invention.

FIG. 2 is a DC / D having the power supply switching means of FIG. 1;
FIG. 3 is a circuit diagram for explaining a C converter and an external circuit.

FIG. 3 is a graph for explaining a transient characteristic of an output DC voltage of the DC / DC converter of FIG. 2;

FIG. 4 is a circuit diagram for explaining a conventional DC / DC converter (switching power supply circuit).

FIG. 5 is a diagram showing a first power supply switching means of the present invention;
Channel MOSFET 161 and second p-channel MOSF
It is a figure for explaining the electric current course of ET162 (the 1).

FIG. 6 is a diagram illustrating a first power supply switching unit according to the present invention;
Channel MOSFET 161 and second p-channel MOSF
It is a figure for explaining the electric current course of ET162 (the 2).

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... DC / DC converter 12 ... Supply power switching means 12a ... Switching signal 14 ... Voltage comparison part 142 ... Logic circuit 142a ... First gate signal 142b ... Second gate signal 16 ... Power supply voltage switch 161 ... First MOSFET (P-channel MOSFET) 162: second MOSFET (P-channel MOSFET) 164: back gate bias circuit 1641: first diode (first Schottky diode) 1642: second diode (second Schottky diode) 20: booster circuit L: power supply line V _dd ... Power line voltage V _in ... Input DC voltage V _out ... Output DC voltage

Claims (5)

[Claims] 1. A DC / DC converter including a booster circuit for boosting an input DC voltage and outputting the boosted DC voltage as a predetermined DC voltage, wherein a voltage between an input DC voltage and an output DC voltage after the start of the booster circuit. Compare the values, supply the input DC voltage to a power supply line that supplies operating power of the booster circuit before the boosting operation in which the input DC voltage is greater than the output DC voltage, start the booster circuit, and A power supply switching means for supplying the output DC voltage instead of the input DC voltage to the power supply line of the boosting circuit after the boosting operation in which the DC voltage is equal to or higher than the input DC voltage to continue the boosting operation of the boosting circuit. A DC / DC converter characterized by the above-mentioned. 2. The power supply switching unit, comprising: a voltage comparison unit configured to compare a voltage value between the input DC voltage and the output DC voltage after the start-up of the booster circuit to generate a switching signal; And a power supply voltage switch that supplies a larger voltage of the input DC voltage or the output DC voltage to a power supply line that supplies operating power of the booster circuit to perform the boosting operation of the booster circuit based on The DC / DC converter according to claim 1, wherein: 3. The first MOSFET of a first conductivity type that supplies the input DC voltage to the power supply line when activated and cuts off the supply of the input DC voltage to the power supply line when inactive. A second MOSFET of the first conductivity type that supplies the output DC voltage to the power supply line when activated and cuts off the supply of the output DC voltage to the power supply line when inactive; a back gate of the first MOSFET And the second MO
3. A back gate bias circuit for applying a larger voltage of the input DC voltage and the output DC voltage to a back gate of the SFET.
4. The DC / DC converter according to 1. 4. The back gate bias circuit comprises: a back gate of the first MOSFET;
A first diode having a cathode connected to the back gate of the SFET and an anode connected to the input DC voltage; a back gate of the first MOSFET and the second MOSFET;
A second diode having a cathode connected to the back gate of the SFET and an anode connected to the output DC voltage, wherein when the input DC voltage is higher than the output DC voltage, the first diode is When activated, the second diode is deactivated, and the input DC voltage is applied to the back gate of the first MOSFET and the back gate of the second MOSFET, and the output DC voltage is higher than the input DC voltage. In this case, the second diode is activated, the first diode is deactivated, and the output DC voltage is applied to a back gate of the first MOSFET and a back gate of the second MOSFET. Item 3. The DC / DC converter according to Item 3. 5. The voltage comparison section, wherein when the input DC voltage is higher than the output DC voltage, a first gate signal having a signal level for activating the first MOSFET is used as the switching signal.
The voltage is applied to the gate of the MOSFET and the second MO
A second gate signal having a signal level for inactivating an SFET is applied to the gate of the second MOSFET as the switching signal, and when the output DC voltage is higher than the input DC voltage, the second MOSFET is activated. The second gate signal having such a signal level as to be applied is applied to the gate of the second MOSFET as the switching signal, and the first gate signal having a signal level for inactivating the first MOSFET is used as the switching signal. 5. The DC / DC converter according to claim 2, further comprising a logic circuit for applying a voltage to the gate of the first MOSFET.