JP2010186336A - Power supply circuit of electric apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the occurrence of control error by properly detecting an instantaneous outage/instantaneous stop of power and transferring a controlling microcomputer to a reset state in proper timing, in a power supply circuit of an electric apparatus. <P>SOLUTION: This power supply circuit of the electric apparatus includes: the control microcomputer 4; a reset IC 6 for output of a reset signal 5 when a voltage V2 on a secondary side is lower than a prescribed threshold; and a power control microcomputer 7 for transferring the control microcomputer 4 to an operation state from the reset state when powered on, based on the reset signal 5, and performing rising processing. The power supply circuit of the electric apparatus also includes, on a primary side of a DC/DC converter 2, a voltage drop detection circuit 9 for output of a voltage drop signal 8 when a voltage V1 on the primary side drops as compared to a reference voltage Vr. The power control microcomputer 7 transfers the control microcomputer 4 to the reset state from the operation state when receiving a voltage drop signal 8 from the voltage drop detection circuit 9, to prevent the control error. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a power supply circuit of an electric device, and more specifically, a control error does not occur by accurately detecting a momentary power interruption / shutdown and shifting a control microcomputer of the electric device to a reset state at an appropriate timing. It is related with the power supply circuit of the electric equipment which can be made.

  A control microcomputer mounted on an electric device such as a disk player has a minimum voltage (hereinafter referred to as a minimum voltage) necessary for normal operation, and is under a supply voltage lower than the minimum voltage. Control error occurs when operating with. For this reason, the control microcomputer is reset until the supply voltage reaches the lowest voltage in the process of gradually increasing the voltage supplied from zero when the power is turned on. When the supply voltage reaches the minimum voltage, the reset state of the control microcomputer is released.

  Conventionally, the above-described control outputs a reset signal when the power supply control microcomputer connected to the control microcomputer and the supply voltage to the control microcomputer are lower than a predetermined threshold. This is executed by a power supply circuit including a voltage detection circuit.

  The conventional power supply circuit will be described with reference to FIGS. As shown in FIG. 3, the power supply circuit 101 converts a primary side DC voltage V1 generated by converting an AC power source (not shown) into a lower DC voltage V2 and outputs it to the secondary side. DC / DC converter 102, control microcomputer 104 for controlling various loads 103 of the electrical equipment connected to the secondary side, and output of reset signal 105 when the secondary side voltage V2 is detected and lower than a predetermined threshold value A reset IC (voltage detection circuit) 106 that controls the state of the control microcomputer 104 by transmitting and receiving control signals 107 and 108 to and from the control microcomputer 104 based on the reset signal 105.

  Here, for example, when the primary side DC voltage V1 is 5 volts, the secondary side DC voltage V2 is 3.3 volts, and the threshold value of the reset IC 106 is set to 2.8 volts, the reset IC 106 Outputs a reset signal 105 until the secondary voltage V2 reaches 2.8 volts after the power is turned on. The power supply control microcomputer 109 maintains the control microcomputer 104 in the reset state while receiving the reset signal 105, and releases the control microcomputer 104 from the reset state when the reset signal 105 is not received.

  On the secondary side of the DC / DC converter 102, an LC circuit 110 serving as a low-pass filter for removing a noise component generated by the oscillation type voltage conversion action of the DC / DC converter 102 is inserted. Further, the power control microcomputer 109 is connected to various power switches 111 of the electric equipment, and can transmit / receive a power switch signal 112 to control various power switches 111 on and off.

  With reference to FIG. 4, description will be given of the operation when the power supply circuit 101 has an instantaneous power interruption or instantaneous interruption during the operation of the electric device. FIG. 4 shows the primary side voltage V1, the secondary side voltage V2, the reset signal 105, and the power switch signal 112 in order from the top. The power switch signal 112 changes from high to low to cause the various power switches 111 to shift from on to off.

  When a power interruption / shutdown occurs (t1), when the primary side voltage V1 and the secondary side voltage V2 drop in a substantially V shape and the secondary side voltage V2 falls below the threshold T (t2) ), The reset signal 105 is output from the reset IC 106. The power supply control microcomputer 109 that has received the reset signal 105 changes the power switch signal 112 from high to low to turn off the power supply of the entire electrical equipment and stop its operation. Thereby, it is possible to prevent the electric device from malfunctioning when the power supply is momentarily interrupted or stopped.

  On the other hand, a capacitor is connected to the ground side of the power supply terminal to the microcomputer, and a comparator for comparing the voltage on the side to which the capacitor is connected (hereinafter referred to as capacitor terminal voltage) with a reference voltage is provided. A reset circuit that resets a microcomputer in response to an output reset signal is known (see, for example, Patent Document 1). In this reset circuit, by appropriately setting the constants of the time constant circuit including the capacitor, a reset signal can be output from the comparator when the power supply is momentarily interrupted or momentarily stopped. Can be reset.

JP-A-9-26835

  By the way, in the conventional power supply circuit 101 shown in FIGS. 3 and 4, since the DC / DC converter 102 and the LC circuit 110 have capacitance components, the voltage fluctuation on the secondary side when an instantaneous interruption or instantaneous interruption occurs. As a result, the reset IC 106 cannot accurately detect the drop in the supply voltage to the control microcomputer 104 in a timely manner, so that a control error of the control microcomputer 104 cannot be reliably prevented.

  Specifically, as shown in FIG. 4, the primary side voltage V1 changes sharply in a large V shape when a momentary interruption or instantaneous interruption occurs (t1). V2 changes to a blunt V-shape inclined in the time axis direction. As a result, the time point t2 at which the secondary side voltage V2 drops below a threshold T (for example, 2.8 volts) is delayed from the time point t1 at which the instantaneous interruption / instantaneous interruption actually occurs, and the output of the reset signal 105 is delayed. Furthermore, the timing at which the power switch signal 112 changes from high to low is delayed, and the power-off timing of the entire electrical equipment is delayed, so that malfunctions cannot be reliably prevented. In addition, when the degree of voltage drop at the momentary interruption / interruption is small (indicated by a two-dot chain line), the value at which the secondary side voltage V2 is most reduced does not reach the threshold T, and Stop cannot be detected.

  In order to solve the above problem, it is conceivable to set the threshold value T to a larger value. However, for example, when the threshold value T is set to 3 volts, the reset IC 106 can detect noise that is normally included in the secondary side voltage V2. Another problem is that the operation of the electric device is stopped more frequently than necessary.

  Therefore, the present invention solves the above-mentioned problem, and in an electric device, a control error is detected by accurately detecting a momentary power interruption or momentary interruption and causing the control microcomputer to shift to a reset state at an appropriate timing. An object of the present invention is to provide a power supply circuit for an electrical device that can be prevented from occurring.

  In order to solve the above problems, the invention of claim 1 is directed to a DC / DC converter that converts a primary side voltage to a lower voltage with respect to a power source and supplies the converted voltage to the secondary side, and the DC / DC converter. A control microcomputer that controls a load driven by a secondary side voltage of the power supply; a voltage detection circuit that detects a secondary side voltage of the DC / DC converter and outputs a reset signal when the voltage is lower than a predetermined threshold; Based on the output form of the reset signal from the voltage detection circuit, the power supply control microcomputer performs the start-up process by shifting the control microcomputer from the reset state to the operating state when the power is changed from the state with the reset signal output to the state without the reset signal output. In a power supply circuit for an electrical device comprising: a voltage drop signal to the primary side of the DC / DC converter when the primary side voltage drops below a reference voltage. Comprising a voltage reduction detection circuit that outputs, the power supply control microcomputer is characterized by shifting the control microcomputer from the operating state to the reset state when it receives the voltage drop signal from the voltage drop detection circuit.

  According to a second aspect of the invention, in the first aspect of the invention, the power supply control microcomputer, after receiving the voltage drop signal from the voltage drop detection circuit, causes the control microcomputer to shift from the operating state to the reset state. The power supply of the entire electric device is forcibly turned off.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the voltage drop detection circuit includes a comparator that compares a voltage on the primary side of the DC / DC converter with a reference voltage. To do.

  According to the first aspect of the present invention, the voltage drop detection circuit detects a voltage drop based on the primary side voltage that is not affected by the dull action due to the capacitance component of the DC / DC converter, and the power supply control microcomputer detects from the voltage drop detection circuit. When the voltage drop signal is received, the control microcomputer is shifted from the operation state to the reset state, so that a control error does not occur, and thus malfunction of the electric device can be prevented.

  According to the invention of claim 2, after the power supply control microcomputer receives the voltage drop signal from the voltage drop detection circuit, the control microcomputer is shifted from the operating state to the reset state, and then the power supply of the entire electric device is forced. Therefore, the malfunction of the electric device can be surely prevented.

  According to the invention of claim 3, since the voltage drop detection circuit includes a comparator that compares the voltage on the primary side of the DC / DC converter with the reference voltage, the voltage drop surely occurs when an instantaneous interruption or instantaneous interruption occurs. A signal can be output.

The block diagram of the power supply circuit of the electric equipment which concerns on one Embodiment of this invention. The figure which shows the mode of the voltage and signal of each part in the power supply circuit. The block diagram of the conventional power supply circuit. The figure which shows the aspect of the voltage and signal of each part in the conventional power supply circuit.

  Hereinafter, a power supply circuit for an electric apparatus according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2. The power supply circuit 1 of this embodiment is built in, for example, a disc player. As shown in FIG. 1, the primary side DC voltage V1 (+5 volts) is changed to a lower DC voltage V2 (+3.3). DC / DC converter 2 that is converted to (volts) and supplied to the secondary side, control microcomputer 4 that controls load 3 such as a motor driven by secondary side voltage V2, and secondary side voltage V2 is detected. A reset IC (voltage detection circuit) 6 that outputs a reset signal 5 when it is lower than a predetermined threshold, and a control microcomputer 4 is shifted from the reset state to the operating state when the power is turned on based on the output mode of the reset signal 5. And a power supply control microcomputer 7 for performing a power-up process, and a voltage drop signal is sent to the primary side of the DC / DC converter 2 when the voltage V1 on the primary side drops below the reference voltage. Voltage drop to output 8 Further comprising a latch circuit 9. The DC voltage V1 on the primary side is generated from an AC power source through a power transformer, a rectifier circuit, etc. (not shown).

  On the secondary side of the DC / DC converter 2, an LC circuit 11 is inserted as a low-pass filter for removing noise components generated by the oscillation type voltage conversion action of the DC / DC converter 2. The threshold value of the reset IC 6 is a value that is equal to or higher than the minimum voltage required for the control microcomputer 4 to shift to a state in which the control microcomputer 4 operates normally when the power is turned on, and does not detect noise normally included in the secondary side voltage (for example, 2.8 volts).

  The power supply control microcomputer 7 transmits and receives control signals 12 and 13 to and from the control microcomputer 4, and keeps the control microcomputer 4 in the reset state while receiving the reset signal 5 when the power is turned on, and the reset signal 5 stops. At that time, the control microcomputer 4 is released from the reset state. When receiving the voltage drop signal 8, the power supply control microcomputer 7 transmits an error signal 12a to the control microcomputer 4 to reset the control microcomputer 4 to a reset state. Further, the power control microcomputer 7 is connected to various power switches 14 of the electric device, and controls the various power switches 14 to be turned on / off by transmitting a power switch signal 15.

  The voltage drop detection circuit 9 includes a comparator 16 that compares the voltage V1 on the primary side of the DC / DC converter 2 with a reference voltage Vr that is not affected by instantaneous interruption or instantaneous interruption. When the voltage V1 on the primary side of the converter 2 falls below the reference voltage Vr, a voltage drop signal 8 is output. The reference voltage Vr is a +5 volt power supply 17 generated as a stabilized power supply by a voltage generation circuit (not shown) of a system different from the primary-side voltage V1. .2 volts). The +5 volt power source 17 as a stabilizing power source can be generated by connecting a large capacity capacitor to a +5 volt voltage generated from an AC power source through a power transformer or the like, and is always charged by the AC power source. A battery may be used.

  Next, the operation of each unit when a momentary power interruption / shutdown occurs will be described with reference to the timing chart of FIG. FIG. 2 shows a primary side voltage V1, a secondary side voltage V2, a voltage drop signal 8, an error signal 12a, and a power switch signal 15 in order from the top. The power switch signal 15 changes from high to low, thereby shifting the various power switches 14 from on to off.

  When power supply interruption or interruption occurs (t1), the primary side voltage V1 changes sharply in a large V shape, and the secondary side voltage V2 changes between the DC / DC converter 2 and the LC circuit 11. Due to the capacitance component, it changes into a substantially V shape that is slanted in the time axis direction. It is assumed that the degree of voltage drop at the time of instantaneous interruption / interruption shown here is relatively small, and the value when the secondary side voltage V2 is most reduced does not reach the threshold value T.

  Since the primary side voltage V1 does not become dull in the time axis direction, it drops below the reference voltage Vr almost simultaneously with the occurrence of instantaneous interruption and instantaneous interruption, and the comparator 16 outputs the voltage drop signal 8 at the timing of t1. When the power supply control microcomputer 7 receives the voltage drop signal 8, it transmits an error signal 12a to the control microcomputer 4, and the control microcomputer 4 immediately shifts to the reset state. Thereby, it is possible to prevent the control microcomputer 4 from causing a control error due to the influence of a momentary interruption / interruption.

  Further, since the power control microcomputer 7 forcibly turns off the various power switches 14 by changing the power switch signal 15 from high to low at the timing of t2, the operation of each part of the electrical equipment is stopped and the malfunction is surely prevented. be able to.

  As described above, in the power supply circuit 1, the voltage drop detection circuit 9 detects the voltage drop based on the primary side voltage V 1 that is not affected by the waveform change (dullness) by the DC / DC converter 2. Even when the voltage drop at the time of disconnection / instantaneous power failure is small and the reset IC 6 cannot detect it, the control microcomputer 4 can be accurately transferred to the reset state by detecting the instantaneous disconnection / instantaneous power failure. An error can be prevented. Further, since it is not necessary to forcibly set the threshold T of the reset IC 6 to a value close to the secondary side voltage V2 in order to allow the reset IC 6 to detect a momentary interruption or instantaneous interruption, the reset IC 6 has a secondary side voltage V2. The noise that normally occurs is not erroneously detected as a momentary interruption / instantaneous interruption, and the electric equipment does not stop operating more frequently than necessary.

  In the power supply circuit 1, the power supply control microcomputer 7 outputs an error signal 12 a to the control microcomputer 4 based on the reception of the voltage drop signal 8, and subsequently changes the power switch signal 15 from high to low, Although the control for forcibly turning off the various power switches 14 to stop the operation of the entire electrical equipment was performed, in other embodiments, the power control microcomputer 7 sends an error signal to the control microcomputer 4 based on the voltage drop signal 8. 12a may be output and control may be performed until the control microcomputer 4 is shifted to the reset state. In that case, the power supply control microcomputer 7 is controlled to change the power switch signal 15 from high to low when the reset signal 5 from the reset IC 6 is received.

1 Power supply circuit 2 DC / DC converter 3 Load 4 Control microcomputer 5 Reset signal 6 Reset IC (voltage detection circuit)
7 Power Control Microcomputer 8 Voltage Drop Signal 9 Voltage Drop Detection Circuit 16 Comparator T Threshold Vr Reference Voltage

Claims (3)

A DC / DC converter that converts the voltage on the primary side to a lower voltage and supplies it to the secondary side,
A control microcomputer for controlling a load driven by a secondary side voltage of the DC / DC converter;
A voltage detection circuit for detecting a secondary voltage of the DC / DC converter and outputting a reset signal when the voltage is lower than a predetermined threshold;
Based on the output mode of the reset signal from the voltage detection circuit, when the power is changed from the state where the reset signal output is present to the state where the reset signal is output, the control microcomputer is shifted from the reset state to the operating state to perform start-up processing. In a power circuit of an electric device equipped with a microcomputer,
The primary side of the DC / DC converter includes a voltage drop detection circuit that outputs a voltage drop signal to the power supply control microcomputer when the primary voltage drops below a reference voltage,
The power supply control microcomputer shifts the control microcomputer from an operation state to a reset state when receiving a voltage drop signal from the voltage drop detection circuit.   The power supply control microcomputer forcibly turns off the power supply of the entire electric device after the control microcomputer is shifted from the operating state to the reset state when a voltage drop signal is received from the voltage drop detection circuit. The power supply circuit for an electric device according to claim 1, wherein   The power supply circuit for an electric device according to claim 1, wherein the voltage drop detection circuit includes a comparator that compares a voltage on a primary side of the DC / DC converter with a reference voltage.

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