JP2007282368A - Negative voltage discharging circuit, power supply, electrical device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a negative voltage discharging circuit for quickly discharging an output capacitor without degrading efficiency and increasing a scale in a power supply when a negative voltage is inhibited from being outputted. <P>SOLUTION: The negative voltage discharging circuit X comprises: a resistor R1 connected to a negative terminal of the output capacitor Co at one end; a transistor N1 having a source connected to the other end of the resistor R1, and a drain connected to the ground terminal; a transistor N2 having a source connected to the negative terminal of the output capacitor Co, a drain connected to a gate of the transistor N1, and a gate connected to the ground terminal; and a transistor P1 having a source connected to an input terminal of a power supply voltage Vbat, a drain connected to the gate of the transistor N1. and a gate connected to an input terminal of a control signal S1. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a negative voltage discharge circuit that discharges an output capacitor when output of a negative voltage generation circuit is stopped, and a power supply device and an electric device using the same.

  FIG. 4 is a block diagram showing a conventional example of a power supply device including a negative voltage discharge circuit.

  As shown in the figure, a conventional power supply device generally has a negative voltage generation circuit a (for example, a desired negative voltage VM1 (for example, -10.0 [V]) is generated from a power supply voltage Vcc (for example, +3.0 [V]). A switching regulator circuit, a charge pump circuit, etc.), and a negative voltage discharge circuit b for discharging the charge of a capacitor Co (hereinafter referred to as an output capacitor Co) connected to the output when the output of the negative voltage generation circuit a is prohibited; It was set as the structure which has.

  The conventional negative voltage discharge circuit c is a control signal for permitting / prohibiting the output operation of the resistor R1 and the N-channel field effect transistor N1 serving as a discharge path of the output capacitor Co and the negative voltage generation circuit a. An inverter INV1 that inverts and outputs S1 to the gate of the transistor N1, and when the output of the negative voltage generation circuit a is prohibited (when the control signal S1 is at a low level), the transistor N1 is turned on to output a capacitor. While the discharge path of Co is conducted, the transistor N1 is turned off and the discharge path of the output capacitor Co is cut off when the output of the negative voltage generation circuit a is permitted (when the control signal S1 is at a high level). It was.

  Other conventional techniques related to the present invention include Patent Document 1 and Patent Document 2.

  In Patent Document 1, an N-channel MOSFET transistor can be used as a discharge switch, and charging / discharging can be performed with respect to an arbitrary charging voltage without using an insulating buck-boost converter. A circuit is disclosed and proposed.

  In Patent Document 2, the frequency of the oscillation circuit can be increased, and the test time can be shortened by reducing the delay time when detecting overcharge, overdischarge, discharge overcurrent, or charge overcurrent. A charge / discharge protection circuit is disclosed and proposed.

JP-A-7-7859 JP 2002-176730 A

  Certainly, in the above-described conventional power supply device, if the negative voltage VM1 is always supplied, the transistor N1 can be controlled by the inverter INV1 without any problem, but the output operation of the negative voltage generation circuit a is controlled by the control signal S1. In the case of permitting / prohibiting, the negative voltage VM1 is not always supplied, so that the transistor N1 cannot be controlled by the inverter INV1.

  That is, when controlling whether or not the negative voltage generating circuit a can output in accordance with the control signal S1, the negative voltage VM1 to the load must be used as the driving voltage of the negative voltage discharging circuit c. When the output of a is prohibited, the drive voltage of the negative voltage discharge circuit c is stopped, and the output capacitor Co cannot be rapidly discharged. Therefore, when the output of the negative voltage generating circuit a is prohibited, the conventional negative voltage discharging circuit c cannot be used unless a separate negative voltage generating means is provided.

  In addition, the said patent document 1 is only related to the charging / discharging technique of a battery, only the circuit for performing discharge between positive and negative is shown, and is not a rapid discharge technique of negative voltage, Further, since a non-insulated negative voltage converter is used when charging / discharging the battery, the essential configuration is clearly different from the present invention.

  In addition, the above Patent Document 2 seems to be similar to the configuration of the present invention in the circuit configuration shown in FIG. 2 and FIG. 3 at first glance, but the related art only detects abnormal current. Therefore, the essential configuration of the present invention is clearly different from that of the present invention.

  In view of the above problems, the present invention quickly discharges the charge of a capacitor connected to an output of a negative voltage generation circuit when the output of the negative voltage generation circuit is prohibited without causing a reduction in efficiency of the power supply device or an unstable state of circuit operation. An object of the present invention is to provide a negative voltage discharge circuit capable of performing the above, a power supply device using the same, and an electric device.

  In order to achieve the above object, the negative voltage discharge circuit according to the present invention is connected to the output of the negative voltage generation circuit when the output of the negative voltage generation circuit is prohibited according to a control signal for permitting / prohibiting the output operation of the negative voltage generation circuit. A negative voltage discharge circuit for discharging the charge of the capacitor, a resistor having one end connected to the negative electrode end of the capacitor; a first N having a source connected to the other end of the resistor and a drain connected to the ground terminal A channel type field effect transistor; a second N channel type field effect transistor having a source connected to the negative terminal of the capacitor, a drain connected to the gate of the first N channel type field effect transistor, and a gate connected to the ground terminal; The source is connected to the power supply voltage input terminal, the drain is connected to the gate of the first N-channel field effect transistor, and the gate is connected to the control signal input terminal It has a configuration comprising a (first configuration); connection has been P-channel field effect transistor and.

  Further, the power supply device according to the present invention includes a negative voltage generation circuit that permits / inhibits a negative voltage output operation in accordance with a predetermined control signal, and an output of the negative voltage generation circuit in accordance with the control signal when the output is prohibited. A negative voltage discharge circuit that discharges the electric charge of the capacitor connected to the output, wherein the negative voltage discharge circuit includes the negative voltage discharge circuit having the first configuration. Second configuration).

  Further, the power supply device according to the present invention generates a negative voltage from the power supply voltage and permits / inhibits the output operation of the negative voltage according to a control signal, and outputs the negative voltage generation circuit. A regulator circuit that inputs and outputs a predetermined negative voltage; a capacitive element that retains a predetermined negative voltage output from the regulator circuit; and a charge that is charged in the capacitive element when the negative voltage output is prohibited And a negative voltage discharge circuit for discharging the power supply voltage to the power supply voltage (third configuration).

  The power supply device having the third configuration may have a configuration (fourth configuration) having the negative voltage discharge circuit having the first configuration as the negative voltage discharge circuit.

  An electrical device according to the present invention is an electrical device comprising a device power supply, a power supply device that is an output conversion unit of the device power supply, and a load that is driven by receiving power supply from the power supply device. Thus, the power supply device has a power supply device having any one of the second to fourth configurations (fifth configuration).

  In the electric device having the fifth configuration, the load is driven by receiving both positive and negative voltages from the power supply device, and the negative voltage is supplied before the positive voltage supply is stopped. The configuration requires a stop (sixth configuration).

  According to the present invention, a negative voltage discharge circuit capable of rapidly discharging the charge of a capacitor connected to the output when the output of the negative voltage generation circuit is prohibited, without incurring a reduction in efficiency or an increase in scale of the power supply device, and It becomes possible to provide a power supply device and an electric device using the same.

  In the following, the case where the present invention is applied to a system regulator IC that is mounted on a mobile phone terminal and generates a drive voltage for each part of the terminal (particularly a CCD [Charge Coupled Devices] camera) by converting the output voltage of the battery will be described as an example. Give a description.

  FIG. 1 is a block diagram showing an embodiment of a mobile phone terminal according to the present invention (particularly, a power supply system part to a CCD camera). As shown in the figure, the mobile phone terminal of the present embodiment includes a battery 1 as a device power supply, a system regulator IC 2 as output conversion means of the battery 1, and a CCD camera module 3 as image pickup means of the mobile phone terminal. , Comprising. Although not explicitly shown in the figure, the mobile phone terminal of the present embodiment has a transmission / reception circuit unit, a speaker unit, and a microphone unit as means for realizing the essential functions (communication function, etc.) in addition to the above components. Naturally, a display unit, an operation unit, a memory unit, and the like are included.

  The CCD camera module 3 has a plurality of drive voltages (for example, +15.0 [V], etc.) when driving a CCD element or DSP [Digital Signal Processor] constituting the CCD camera module 3 or its I / O [Input / Output] circuit. +3.0 [V], +1.8 [V], −8.0 [V]). Therefore, the system regulator IC2 is a positive voltage generation circuit 2P (a switching regulator circuit or a charge pump) that positively boosts the battery voltage Vbat (for example, +3.0 [V]) to a predetermined positive voltage VP (for example, +18.0 [V]). And a negative voltage generation circuit 2M that negatively boosts the battery voltage Vbat to a predetermined negative voltage VM (for example, −8.0 [V]), as well as a plurality of voltages from the battery voltage Vbat or the positive voltage VP. As means for generating positive voltages VP1 to VPn (for example, +15.0 [V], +3.0 [V], +1.8 [V]), first to nth regulator circuits 21 to 2n (series regulator circuits) Etc.). The positive voltages VP1 to VPn and the negative voltage VM are all supplied to the CCD camera module 3.

  Further, the negative voltage generation circuit 2M of the present embodiment is one in which the output operation of the negative voltage VM is permitted / prohibited in accordance with a predetermined control signal S1, and the control signal S1 is connected to the output terminal thereof. Accordingly, there is provided a negative voltage discharge circuit X (not shown in the figure) for rapidly discharging the output capacitor when the output of the negative voltage generation circuit 2M is stopped.

  FIG. 2 is a circuit diagram (partly including a block diagram) showing a configuration example of the negative voltage generation circuit 2M and the negative voltage discharge circuit X.

  As shown in the figure, the negative voltage generation circuit 2M of the present embodiment includes a P-channel field effect transistor (output transistor) Q1, an inductor L1, a diode D1, an output capacitor Co, a control unit CNT, This is a general negative boost type switching regulator circuit.

  The source of the transistor Q1 is connected to the input terminal of the battery voltage Vbat. The drain of the transistor Q1 is connected to the ground terminal via the inductor L1. The gate of the transistor Q1 is connected to the gate signal output terminal of the control unit CNT. The cathode of the diode D1 is connected to the drain of the transistor Q1. The anode of the diode D1 is connected to the ground terminal via the output capacitor Co. The negative electrode terminal of the output capacitor Co is connected to the negative voltage VM extraction terminal, and is also connected to the output feedback signal input terminal of the control unit CNT.

  In the negative voltage generation circuit 2M having the above-described configuration, the inductor L1 that is an energy storage element is driven according to the switching control of the transistor Q1 by the control unit CNT, and a desired negative voltage VM is drawn from the negative terminal of the output capacitor Co. It is.

  In the negative voltage generation circuit 2M of the present embodiment, the control unit CNT has an output enable / disable function according to the control signal S1. Specifically, the control unit CNT recognizes that the output operation of the negative voltage VM is permitted when the control signal S1 is at a high level, and outputs an output feedback signal (an output voltage feedback signal and / or an output current feedback). On the other hand, when the control signal S1 is at a low level, it recognizes that the output operation of the negative voltage VM is prohibited, and does not depend on the output feedback signal. The switching control of Q1 is stopped and turned off.

  Further, the negative voltage discharge circuit X of the present embodiment has a resistor R1 and a resistor R3, one end of which is connected to the negative electrode end of the output capacitor Co; a source is connected to the other end of the resistor R1, and a drain is connected to the ground terminal. An N-channel field effect transistor N1 having a source connected to the other end of the resistor R3, a drain connected to the gate of the N-channel field-effect transistor N1, and a gate connected to the ground terminal A transistor N2, one end connected to the gate of the N-channel field effect transistor N1, and a source connected to the input of the battery voltage Vbat, a drain connected to the other end of the resistor R2, and a gate a control signal And a P-channel field effect transistor P1 connected to the input terminal of S1.

  The operation of the negative voltage discharge circuit X having the above configuration will be described in detail.

  First, a description will be given of when negative voltage VM output is permitted. When the output of the negative voltage VM is permitted, the transistor N2 is turned on because its gate potential (ground voltage GND) is higher than the source potential (negative voltage VM). As a result, the transistor N1 is turned off because its gate potential is at a low level (almost negative voltage VM), and the discharge path of the output capacitor Co is cut off. At this time, since the transistor P1 is turned off in response to the high-level control signal S1, the power consumption of the negative voltage discharge circuit X is zero when the output of the negative voltage VM is permitted.

  Next, a description will be given of when output of the negative voltage VM is stopped. When the output of the negative voltage VM is stopped, the transistor P1 is turned on in response to the low level control signal S1. As a result, the transistor N1 is turned on, and the discharge path of the output capacitor Co becomes conductive. By such conduction of the discharge path, rapid discharge of the output capacitor Co is realized when the negative voltage VM is stopped. When the output capacitor Co is discharged, the transistor N2 is turned off because its gate potential and source potential are the same potential (ground voltage GND), and the current path from the power supply voltage input terminal to the negative voltage extraction terminal is cut off. Will be in the form. Therefore, after the output capacitor Co is discharged, the power consumption of the negative voltage discharge circuit X becomes zero.

  Thus, with the negative voltage discharge circuit X having the above-described configuration, it is possible to rapidly discharge the output capacitor Co when the output of the negative voltage generation circuit 2M is stopped without requiring a separate negative voltage as a drive voltage. It becomes.

  In particular, in the mobile phone terminal of the present embodiment, the CCD camera module 3 serving as a load is driven by receiving both the positive voltages VP1 to VPn and the negative voltage VM from the system regulator IC2, and the driving is stopped. At this time, the supply of the negative voltage VM needs to be stopped before the supply of the positive voltages VP1 to VPn is stopped (see FIG. 3). Therefore, in the system regulator IC2, in order to achieve both the improvement of the boosting efficiency and the realization of the output sequence, the output voltage of the negative voltage generating circuit 2M is stopped using the negative voltage discharging circuit X of the present embodiment. It is considered necessary to rapidly discharge Co.

  In the above embodiment, the case where the present invention is applied to a system regulator IC that is mounted on a mobile phone terminal and converts the output voltage of the battery to generate the drive voltage of each part of the terminal has been described as an example. However, the application target of the present invention is not limited to this, and can be widely applied to all power supply devices including a negative voltage generation circuit.

  The configuration of the present invention can be variously modified within the scope of the present invention in addition to the above embodiment.

  For example, in the present embodiment, a configuration using a switching regulator circuit as an example of the negative voltage generation circuit 2M is given as an example in order to reduce heat loss and improve efficiency, but the configuration of the negative voltage generation circuit 2M is given here. The present invention is not limited, and a negative output type charge pump circuit or the like may be used if priority is given to reducing switching noise.

  In the above embodiment, the configuration using the diode D1 as an example of the component of the negative voltage generating circuit 2M has been described. However, the configuration of the present invention is not limited to this, and the diode D1 Instead of this, a synchronous rectification transistor may be used.

  In the above-described embodiment, the configuration in which the negative voltage VM is directly supplied to the CCD camera 3 that is the load has been described as an example. However, the configuration of the present invention is not limited to this, and the negative voltage generation is performed. A regulator circuit that regulates the output of the circuit 2M may be inserted.

  The present invention is a technique useful in achieving both improvement in efficiency of a power supply device including a negative voltage generation circuit and speeding up of output stop. For example, the present invention is mounted on a mobile phone terminal and converts the output voltage of a battery. This is a technique suitable for a system regulator IC that generates a drive voltage for a CCD camera module.

These are block diagrams which show one Embodiment of the mobile telephone terminal which concerns on this invention. These are circuit diagrams showing a configuration example of the negative voltage generation circuit 2M and the negative voltage discharge circuit X. These are the output sequence diagrams of system regulator IC2. These are block diagrams which show one prior art example of the power supply device provided with the negative voltage discharge circuit.

Explanation of symbols

1 Battery 2 System regulator IC
2P positive voltage generation circuit (switching regulator circuit)
2M negative voltage generation circuit (switching regulator circuit)
21 to 2n 1st to nth regulator circuits (series regulator circuit)
3 CCD camera module Q1 Output transistor (P-channel field effect transistor)
L1 Inductor D1 Diode C1 Output Capacitor CNT Controller X Negative Voltage Discharge Circuit P1 P-Channel Field Effect Transistor N1-N2 N-Channel Field Effect Transistor R1-R3 Resistance

Claims (6)

  A negative voltage discharge circuit for discharging a charge of a capacitor connected to an output of the negative voltage generation circuit when the output of the negative voltage generation circuit is prohibited in response to a control signal for permitting / prohibiting an output operation of the negative voltage generation circuit; A resistor connected to the negative terminal of the capacitor; a first N-channel field effect transistor having a source connected to the other end of the resistor and a drain connected to a ground terminal; a source connected to the negative terminal of the capacitor A second N-channel field effect transistor having a drain connected to the gate of the first N-channel field effect transistor and a gate connected to the ground terminal; a source connected to the power supply voltage input terminal, and a drain connected to the first N-channel field effect transistor A P-channel field effect transistor connected to the gate of the effect transistor and having the gate connected to the control signal input terminal. Negative voltage discharge circuit, characterized by comprising.   A negative voltage generation circuit in which negative voltage output operation is permitted / prohibited according to a predetermined control signal, and a capacitor connected to the output is discharged when the output of the negative voltage generation circuit is prohibited according to the control signal A power supply apparatus comprising the negative voltage discharge circuit according to claim 1, wherein the negative voltage discharge circuit includes the negative voltage discharge circuit according to claim 1.   A negative voltage generation circuit that generates a negative voltage from the power supply voltage and can permit / inhibit the output operation of the negative voltage according to a control signal, and inputs the output of the negative voltage generation circuit, and outputs a predetermined negative voltage A regulator circuit, a capacitive element for holding a predetermined negative voltage output from the regulator circuit, and a negative charge for discharging the charge charged in the capacitive element to the power supply voltage when the negative voltage output is prohibited. And a voltage discharge circuit.   A power supply apparatus comprising the negative voltage discharge circuit according to claim 1 as the negative voltage discharge circuit.   An electrical apparatus comprising: a device power supply; a power supply device that is an output conversion unit of the device power supply; and a load that is driven by receiving power supply from the power supply device, wherein the power supply device is defined as claim 2. An electric apparatus comprising the power supply device according to claim 4.   The load is driven by receiving supply of both positive and negative voltages from the power supply apparatus, and the supply of the negative voltage is required before the supply of the positive voltage is stopped. 5. The electric device according to 5.

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