JP2012010512A - Power source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power source device capable of improving a protection function of a switching element without a complicated circuit.SOLUTION: A power source device 10 has: a main switching element 15 having one end connected to a power source terminal, and the other end connected to an output terminal; a rectifier element having a cathode terminal connected to the other end of the main switching element, and a grounded anode terminal; a level shift circuit that converts the voltage level of a control signal for controlling the main switching element, and outputs the converted control signal; a driver circuit; a bootstrap circuit that supplies a power source to the level shift circuit and the driver circuit; and a regulator that converts a voltage from the power source into a predetermined voltage, and supplies the converted power source to the bootstrap circuit. The power source device 10 also has regulator power source supply blocking means 23 that blocks the power source supply from the regulator to the bootstrap circuit during a period in which the control signal that turns the main switching element on is inputted.

Description

  The present invention relates to a power supply device, and more particularly to a power supply device having an improved protection function of a switching element.

  2. Description of the Related Art Conventionally, a power supply device that outputs a rectangular wave voltage having a predetermined duty ratio by PWM driving a switching element such as a MOSFET has been used (see, for example, Patent Document 1). In such a power supply device, when an N-channel MOSFET is used as a high-side switch, it is necessary to boost the gate electrode to a power supply voltage or higher. For this reason, the conventional power supply device uses a bootstrap circuit in which a capacitor is connected between the source electrode and the control power supply terminal of the gate control circuit.

  In Patent Document 1, a capacitor that is charged when the source electrode of the high-side MOSFET becomes the ground potential is provided as a booster circuit, a potential detection circuit that monitors the gate-source voltage Vgs of the high-side MOSFET is provided, and Vgs When the voltage drops below a predetermined value, the gate control circuit lowers the potential of the gate electrode by the signal from the potential detection circuit to turn off the high-side MOSFET.

Japanese Patent Laid-Open No. 5-38134

  However, Patent Document 1 has a problem that the circuit becomes complicated because a floating voltage called the gate-source voltage Vgs of the high-side MOSFET that is a switching element has to be monitored. Further, in order to stop driving the high-side MOSFET after detecting the decrease in the gate-source voltage Vgs of the high-side MOSFET, the decrease in the gate-source voltage Vgs of the high-side MOSFET is detected before detecting the decrease in the high-side MOSFET. There is a problem that there is a possibility of a malfunction that a delay time always occurs before the drive is stopped and the high-side MOSFET is turned on during the delay time.

  In view of the above-described problems, an object of the present invention is to provide a power supply device that is not complicated in circuit, can prevent malfunction of a switching element, and can improve a protection function.

The power supply device according to the present invention is configured as follows in order to achieve the above object.
The first power supply device (corresponding to claim 1) has a main switching element having one end connected to the power supply terminal and the other end connected to the output terminal, a cathode terminal connected to the other end of the main switching element, and an anode A rectifying element whose terminal is grounded, a level shift circuit that converts and outputs a control signal for controlling the main switching element, a driver circuit that supplies the control signal output from the level shift circuit to the main switching element, A power supply device including a bootstrap circuit that supplies power to a level shift circuit and a driver circuit, and a regulator that converts a voltage from the power supply into a predetermined voltage and supplies power to the bootstrap circuit, the main switching element being turned on During the period when the control signal to be input is input, the power supply from the regulator to the bootstrap circuit is shut off. Characterized in that a regulator power supply interrupting means.
In the above configuration, the second power supply device (corresponding to claim 2) is preferably configured such that the regulator includes a transistor and a drive element including a current source that drives the transistor, and the regulator power supply cutoff unit includes one end Is connected to a current source and the other end is grounded, and is configured to include a second switching element that is turned on in response to a control signal for turning on the main switching element and draws the current of the current source to the ground side.
In the above configuration, the third power supply device (corresponding to claim 3) is preferably configured such that the regulator power supply cutoff means is provided between the connection of the regulator and the bootstrap circuit, and controls the main switching element. And a third switching element that is turned off in response to the light.
In a fourth power supply device (corresponding to claim 4), in the above configuration, preferably, the rectifier element whose cathode terminal is connected to the other end of the main switching element and whose anode terminal is grounded is the fourth switching element. It is characterized by comprising.

  ADVANTAGE OF THE INVENTION According to this invention, the circuit is not complicated, the malfunctioning of a switching element can be prevented, and the power supply device which can improve a protection function can be provided.

It is a conceptual diagram which shows the power supply device which concerns on the 1st Embodiment of this invention. 1 is a circuit diagram showing a power supply device according to a first embodiment of the present invention. It is a figure which shows the waveform of each part of the power supply device which concerns on the 1st Embodiment of this invention. It is a conceptual diagram which shows the power supply device which concerns on the 2nd Embodiment of this invention. It is a figure which shows the waveform of each part of the power supply device which concerns on the 2nd Embodiment of this invention. It is a figure which shows the Example of a synchronous rectification DC-DC converter.

  DESCRIPTION OF EMBODIMENTS Preferred embodiments (examples) of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a conceptual diagram showing a power supply device according to the first embodiment of the present invention. FIG. 2 is a circuit diagram showing the power supply device according to the first embodiment of the present invention. The power supply device 10 outputs a rectangular wave voltage having a desired duty ratio from the terminal M1. The power supply device 10 can be used as a power supply device for driving a motor by connecting a motor or the like as a load to the terminal M1. As shown in FIGS. 1 and 2, the power supply device 10 connects a smoothing circuit 40 including an inductor L and a capacitor C to a terminal M1, and connects a connection point J1 between the inductor L and the capacitor C to an output terminal VOUT30. Thus, the DC-DC converter 10c can be configured. In this embodiment, a load R30 is connected to the output terminal VOUT30 as a load of the DC-DC converter 10c. Hereinafter, the DC-DC converter 10c will be described as an example.

  In this power supply device 10, a drain terminal 11 is connected to a power supply (input power supply voltage PVDD) terminal 12, a main switching element 15 in which a source terminal 13 is connected to a terminal 14, a cathode terminal 16 is connected to the terminal 14, and an anode And a rectifying element 18 having a terminal 17 grounded. In addition, the power supply apparatus 10 outputs a level shift circuit 19 that converts a voltage level of a control signal for controlling on / off of the main switching element 15 that is input from a control unit (not shown) through a terminal SIN, and outputs the control signal. And a driver circuit unit 20 for supplying the control signal to the gate 15g of the main switching element 15. Further, the power supply device 10 includes a bootstrap circuit 21 that supplies power to the level shift circuit 19 and the driver circuit unit 20, and a regulator 22 that converts the voltage from the power supply terminal 12 into a predetermined voltage and supplies power to the bootstrap circuit 21. And. The power supply device 10 supplies power from the regulator 22 to the bootstrap circuit 21 during a period in which a control signal (high side ON signal) for turning on the main switching element 15 is input to the terminal SIN from a control unit (not shown). A regulator power supply shut-off unit 23 is provided to shut off the power.

  As the main switching element 15, for example, an N-channel MOSFET (a field effect transistor made of a metal oxide semiconductor, hereinafter simply referred to as NMOS) is used.

  As shown in FIG. 2, the regulator 22 includes, for example, a current source 22a for driving a bipolar transistor, a resistor R1, a constant voltage element ZD, and a bipolar transistor 22b.

  1 and 2, the power supply voltage VDD from the regulator 22 is supplied to the bootstrap circuit 21 in a magnitude different from the input power supply voltage (PVDD), and the DC-DC converter 10c The voltage (PVDD) is converted, and a desired output voltage is output from the output terminal VOUT30 via the smoothing circuit unit 40.

  The driver circuit unit 20 includes a driver circuit 20a (hereinafter referred to as a high side driver) for driving the main switching element 15. The output terminal 20b of the high side driver 20a is connected to the gate terminal 15g of the main switching element 15, and performs on / off control of the main switching element 15. As a result, a rectangular wave voltage having a desired duty ratio appears at the terminal M1 through the connection point (terminal) 14 between the main switching element 15 and the rectifying element 18.

  The smoothing circuit unit 40 is configured by a series circuit of an inductor L and a capacitor C, and a connection point J1 thereof is connected to the output terminal VOUT30. Here, one end of the inductor L is connected to the terminal M1 of the power supply device 10, the other end of the inductor L and one end of the capacitor C are connected at a connection point J1, and the other end of the capacitor C is grounded. In the smoothing circuit unit 40, the rectangular wave voltage input from the terminal M1 of the power supply device 10 is smoothed by the inductor L and the capacitor C, and a DC output voltage is output from the output terminal VOUT30. Here, in order to set the DC output voltage to a desired voltage, a control circuit (not shown) compares the output voltage with a predetermined reference voltage, and feedback-controls the error voltage to the high-side ON signal. As a result, the duty ratio of the high-side ON signal changes and the output voltage is controlled to a desired voltage.

  The bootstrap circuit 21 generates a voltage (Vbst) higher than the input power supply voltage (PVDD) by the capacitor Cbst and the diode Dbst. The bootstrap circuit is provided in the power supply device 10 because the main switching element 15 is an NMOS, so that the gate voltage for driving the main switching element 15 is set to a voltage higher than the input power supply voltage (PVDD). It is necessary to do.

  In the bootstrap circuit 21, when the main switching element 15 is in an OFF state and when the regenerative current of the inductor L of the smoothing circuit unit 40 flows through the rectifier element 18, the inductor L, and the capacitor C, the terminal of the capacitor Cbst Since the potential on the 14 side is the ground potential (the forward voltage of the rectifier 18 is ignored), a charging current flows into the capacitor Cbst from the output terminal of the regulator 22 via the diode Dbst, and the capacitor Cbst has a voltage value ( (The forward voltage of the diode Dbst is ignored). Next, when the main switching element 15 is turned on, the voltage value (Vm) of the terminal 14 connected to the terminal 13 of the main switching element 15 rises to the input power supply voltage (PVDD). Therefore, the voltage value (Vbst) at the connection point M2 (the power supply terminal of the high side driver 20a) between the capacitor Cbst and the diode Dbst is the sum of the input power supply voltage (PVDD) and the charge voltage value (VDD) of the capacitor Cbst, that is, (PVDD + VDD), and a voltage value higher than the input power supply voltage (PVDD) is supplied to the power supply terminal of the high-side driver 20a.

  In this way, the high side driver 20a operates with the inter-terminal voltage (Vbst−Vm) generated by the capacitor Cbst of the bootstrap circuit 21, and the gate 15g of the main switching element 15 is driven by the input power supply voltage (PVDD). It can be driven at a high voltage.

  The level shift circuit 19 converts the voltage level of the signal input from the terminal SIN into the voltage level of the control signal supplied to the gate 15g of the main switching element 15. This is because the high side driver 20a operates between the voltages of Vbst-Vm, and therefore it is necessary to provide the level shift circuit 19 in the preceding stage of the high side driver 20a to convert the voltage level of the control signal.

  The regulator power supply cut-off unit 23 cuts off power supply from the regulator 22 during a period in which a control signal for turning on the main switching element 15 is input to the terminal SIN from a control unit (not shown). As shown in FIG. 2, the regulator power supply cutoff unit 23 has a drain terminal 23d connected to the bias current source 22a of the regulator 22, a source terminal 23s grounded, and a control signal from the terminal SIN sent from the terminal M4 to the gate 23g. A second switching element 23b made of supplied N-channel MOSFET is used. The second switching element 23b is turned on in response to a control signal for turning on the main switching element 15.

  In the present embodiment, the regulator power supply shut-off unit 23 detects “abnormality that corresponds to the detection of an abnormality, that is, an abnormality in which a certain abnormality occurs in the capacitor Cbst and the voltage value of the power supply terminal M2 of the high-side driver 20a decreases. Instead of “stopping the main switching element 15”, it can be configured to “become a circuit operation that does not cause a problem even if an abnormality occurs”. That is, the regulator power supply shut-off unit 23 ensures that the regulator (when the control signal for turning on the main switching element 15 is input from the terminal SIN regardless of the voltage level of the power supply terminal M2 of the high side driver 20a. REG) 22, the circuit operation for turning off the output voltage VDD is introduced.

  Next, the operation of the power supply apparatus 10 according to this embodiment of the present invention will be described with reference to the operation timing chart of FIG. 3A shows a control signal (high-side ON signal) for turning on / off the main switching element 15 input to the terminal SIN from a control unit (not shown), and FIG. 3B shows a voltage waveform of the terminal 14. FIG. 3C shows the regulator output voltage VDD.

  The normal operation is as follows. When the high-side ON signal is at the LOW level, the second switching element 23b is turned off, so that the current from the current source 22a flows between the base and emitter of the transistor 22b and the constant voltage element ZD. Outputs a voltage VDD obtained by subtracting the base-emitter voltage from the voltage value of the constant voltage element ZD.

  When the high-side ON signal becomes a high level (arrow A), the second switching element 23b described above is turned on, and the second switching element 23b draws the bias current from the current source 22a of the regulator 22, so that the terminal 22f The potential becomes the GND potential, the transistor 22b is turned off, and the regulator output voltage VDD drops to the GND potential (arrow B). As a result, voltage supply from the regulator 22 to the bootstrap circuit 21 is cut off during a period in which a control signal for turning on the main switching element 15 is input to the terminal SIN from a control unit (not shown).

  When the high-side ON signal becomes LOW level (arrow C), the second switching element 23b is turned OFF, so that a bias current is supplied to the regulator output transistor 22b again, and the regulator output voltage VDD is equal to the voltage value of the constant voltage element ZD. Rapidly rises to a voltage obtained by subtracting the base-emitter voltage of the transistor 22b (arrow D), and charges the capacitor Cbst.

  As described above, the second switching element 23b that is turned on in response to the high-side ON signal is provided, and the drain terminal 23d is connected to the base terminal of the transistor 22b of the regulator 22 (the bipolar transistor in FIG. 2) and the bias current source 23a. The target function is realized with a simple configuration connected to the connected terminal 22f.

  In the prior art, even when the capacitor Cbst is disconnected due to some abnormality, if the high side ON signal is input from the terminal SIN, the main switching element 15 is forcibly driven from the output terminal of the regulator 22. Therefore, even if a decrease in the gate-source voltage Vgs is detected in a conventional device provided with a potential detection circuit for monitoring the gate-source voltage Vgs of the main switching element 15, the decrease in the voltage value Vgs is detected. During the delay time that occurs from the time point until the main switching element is turned off, the main switching element may not be driven with a sufficient gate voltage, but may be turned on instantaneously with a high on-resistance, leading to deterioration or destruction of the product. was there.

  On the other hand, in the present embodiment, the output voltage of the regulator 22 is off even when the high-side ON signal is input from the terminal SIN in a state where the connection of the capacitor Cbst is disconnected due to some abnormality, so that the main switching element 15 There is no bias source for charging the gate 15g. Therefore, the main switching element 15 can be reliably protected without being turned on.

  FIG. 4 is a conceptual diagram showing a power supply device 50 according to the second embodiment of the present invention. The regulator power supply cutoff unit 51 according to the second embodiment is provided between the regulator 22 and the bootstrap circuit 21, and receives a control signal (high side ON signal) input from the control unit (not shown) to the terminal SIN from the terminal M5. The third switching element 52 is received and controlled. The third switching element 52 is turned off when a control signal for turning on the main switching element 15 is inputted from the terminal SIN, and is turned off when a control signal for turning off the main switching element 15 is inputted from the terminal SIN. Turn on. Since other configurations are the same as those of the first embodiment, the same reference numerals are given and description thereof is omitted.

  Also in the second embodiment, as in the first embodiment, “corresponding after detecting an abnormality, that is, detecting an abnormality in which a certain abnormality occurs in the capacitor Cbst and the voltage value of the power supply terminal M2 of the high-side driver 20a decreases. Instead of “stopping the main switching element 15”, it can be configured to “become a circuit operation that does not cause a problem even if an abnormality occurs”. That is, the regulator power supply cut-off unit 23 ensures that the regulator 22 is always in the period when the control signal for turning on the main switching element 15 is input from the terminal SIN regardless of the voltage level of the power supply terminal M2 of the high-side driver 20a. Introduces circuit operation to disconnect the connection.

  Next, the operation of the power supply apparatus 50 according to this embodiment of the present invention will be described with reference to the operation timing chart of FIG. FIG. 5A shows a control signal (high-side ON signal) for turning on and off the main switching element 15 input to the terminal SIN from a control unit (not shown), and FIG. 5B shows a voltage waveform of the terminal 14. FIG. 5C shows the voltage input to the bootstrap circuit 21.

  The normal operation is as follows. When the high-side ON signal is at the LOW level, the third switching element 52 is turned on, so that the voltage from the regulator 22 is supplied to the bootstrap circuit 21 and charges the capacitor Cbst.

  When the high-side ON signal becomes High level (arrow E), the third switching element 52 described above is turned off, and the voltage supply from the regulator 22 to the bootstrap circuit 21 is cut off. As a result, the voltage supply from the regulator 22 is cut off during the ON period of the main switching element 15 (arrow F).

  When the high-side ON signal again becomes the LOW level (arrow G), the switch 52 is turned on, so that the output from the REG is supplied again to the bootstrap circuit 21 (arrow H) and charges the capacitor Cbst.

  As described above, the target function is realized with a simple configuration provided with the third switching element 52 that is turned off in response to the high-side ON signal.

  In the prior art, even when the capacitor Cbst is disconnected due to some abnormality, if the high side ON signal is input from the terminal SIN, the main switching element 15 is forcibly driven from the output terminal of the regulator 22. Therefore, even if a decrease in the gate-source voltage Vgs is detected in a conventional device provided with a potential detection circuit for monitoring the gate-source voltage Vgs of the main switching element 15, the decrease in the voltage value Vgs is detected. During the delay time that occurs from the time point until the main switching element is turned off, the main switching element may not be driven with a sufficient gate voltage, but may be turned on instantaneously with a high on-resistance, leading to deterioration or destruction of the product. was there.

  On the other hand, in the present embodiment, in the state where the connection of the capacitor Cbst is disconnected due to some abnormality, the voltage from the regulator 22 is not supplied even if the high-side ON signal is input from the terminal SIN. I can't charge 15g. Therefore, the main switching element 15 can be reliably protected without being turned on.

  In the present embodiment, the regulator output transistor is described as bipolar, but the output transistor of the regulator 22 may not be bipolar. Even if the output transistor is a MOSFET and its gate terminal is short-circuited to GND by a switch, the same effect can be obtained. In addition, even if it is not a combination of the switch and the output transistor of the regulator, the same effect can be obtained as long as the output of the regulator can be cut off during the high side ON period.

  Further, the rectifying element 18 may be replaced with an N-channel MOSFET to form a synchronous rectification DC-DC converter. FIG. 6 shows an embodiment of a synchronous rectification DC-DC converter.

  Furthermore, in the present embodiment, the DC-DC converter provided with a smoothing circuit in the output unit has been described as an example. However, a load such as a motor can be directly connected to the output terminal M1 of the power supply device.

  The configurations, shapes, sizes, and arrangement relationships described in the above embodiments are merely schematically shown to the extent that the present invention can be understood and implemented, and the numerical values and the compositions (materials) of the respective components Is just an example. Therefore, the present invention is not limited to the described embodiments, and can be modified in various forms without departing from the scope of the technical idea shown in the claims.

  The power supply device according to the present invention is used as a power supply device for driving a DC-DC converter, a motor, or the like.

DESCRIPTION OF SYMBOLS 10 Power supply device 10c DC-DC converter 11 Drain terminal 12 Power supply (input power supply voltage) terminal 13 Source terminal 14 Terminal 15 Main switching element 16 Cathode terminal 17 Anode terminal 18 Rectifier 19 Level shift circuit 20 Driver circuit part 21 Bootstrap circuit 22 Regulator 23 Regulator power supply cutoff section L Inductor C Capacitor Cbst Capacitor Dbst Diode M1 Output terminal

Claims (4)

A main switching element having one end connected to the power supply terminal and the other end connected to the output terminal;
A rectifying element having a cathode terminal connected to the other end of the main switching element and an anode terminal grounded;
A level shift circuit that converts a voltage level of a control signal for controlling the main switching element and outputs the signal;
A driver circuit for supplying the control signal output from the level shift circuit to the main switching element;
A bootstrap circuit for supplying power to the level shift circuit and the driver circuit;
A power supply device comprising a regulator that converts a voltage from a power source into a predetermined voltage and supplies power to the bootstrap circuit,
A power supply apparatus comprising a regulator power supply cutoff means for cutting off power supply from the regulator to the bootstrap circuit during a period when the control signal for turning on the main switching element is input. The regulator is composed of a driving element including a transistor and a current source for driving the transistor, and the like.
The regulator power supply cutoff means has a second end connected to the current source and the other end grounded, and is turned on in response to the control signal for turning on the main switching element to draw the current of the current source to the ground side. The power supply device according to claim 1, comprising:   The regulator power supply shut-off means is a third switching element that is provided between the regulator and the bootstrap circuit and is turned off in response to the control signal for turning on the main switching element. The power supply device according to claim 1.   2. The power supply apparatus according to claim 1, wherein the rectifying element having the cathode terminal connected to the other end of the main switching element and the anode terminal grounded is constituted by a fourth switching element.

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