JP2010140113A - Power source circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To supply a control means with the voltage for operating the control means even if a voltage from a standby power source circuit in a standby condition is equal to or less than the voltage for operating the control means. <P>SOLUTION: This power source circuit 1 includes: a main power source circuit 3 which generates a voltage for operating a microcomputer 5 in a normal operating condition; a standby power source circuit which generates a voltage for operating the microcomputer 5 in a standby condition; a switching circuit 13 which turns the main power source circuit 3 off when turned off and which turns the main power source circuit 3 on when turned on; and a voltage detection circuit 6 which detects whether or not the voltage from the standby power source circuit 2 is not more than a threshold voltage in the standby condition and which if detecting that the voltage from the standby power source circuit 2 is not more than the threshold voltage, controls the switching circuit 13 to turn on, and which if detecting that the voltage from the standby power source circuit 2 is greater than the threshold voltage, controls the switching circuit 13 to turn off. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a power supply circuit including a standby power supply circuit and a main power supply circuit.

  In an electronic device including a microcomputer, a voltage is supplied to the microcomputer from a standby power supply circuit in a standby state, and a voltage is supplied to the microcomputer from a main power supply circuit (and a standby power supply circuit) in a normal operation state. Here, in the standby state, when the input voltage supplied to the standby power supply circuit is a low voltage and the voltage from the standby power supply circuit is a low voltage, the voltage necessary for operating the microcomputer is supplied to the microcomputer. There is a problem that you can not.

JP 2004-328958 A

  The present invention has been made to solve the above-described conventional problems, and the object of the present invention is to control the control means even when the voltage from the standby power supply circuit is equal to or lower than the voltage for operating the control means in the standby state. An object of the present invention is to provide a power supply circuit that can supply a voltage for operation to a control means.

  According to a preferred embodiment of the present invention, a power supply circuit is provided with an input voltage and generates a voltage for operating the control means in a normal operation state, and is supplied with the input voltage and operates the control means in a standby state. A standby power supply circuit that generates a voltage to be turned off, a switching circuit that turns off the main power supply circuit when turned off and turns on the main power supply circuit when turned on, and the standby power supply in the standby state Detecting whether or not the voltage from the power supply circuit is less than or equal to a threshold voltage, and controlling the switching circuit to be on when detecting that the voltage from the standby power supply circuit is less than or equal to the threshold voltage, And a voltage detection circuit that controls the switching circuit to be turned off when it is detected that the voltage from the standby power supply circuit is larger than the threshold voltage.

  In the standby state, when it is detected that the voltage from the standby power supply circuit is equal to or lower than the threshold voltage and is a low voltage, the main power supply circuit is turned on in spite of the standby state. As a result, the voltage from the main power supply circuit is supplied to the control means, and the voltage for operating the control means can be supplied from the main power supply circuit and the standby power supply circuit.

  In a preferred embodiment, the switching circuit includes a relay switch that controls the main power supply circuit to an on state or an off state, and further includes a transistor that controls the relay switch to an on state or an off state, and the voltage detection circuit For comparing the voltage from the standby power supply circuit with the threshold voltage, and when the voltage from the standby power supply circuit is equal to or lower than the threshold voltage, to turn on the relay switch on the control electrode of the transistor And a comparator for supplying a signal for turning off the relay switch to the control electrode of the transistor when the voltage from the standby power supply circuit is larger than the threshold voltage.

  According to another preferred embodiment of the present invention, a power supply circuit is provided with a main power supply circuit for generating a voltage for operating the control means in a normal operation state, and a control circuit in the standby state. In a standby state, a standby power supply circuit that generates a voltage for operating, a switching circuit that turns off the main power supply circuit by turning off, and turns on the main power supply circuit by turning on. Detecting whether or not the voltage from the standby power supply circuit is a low voltage, and controlling the switching circuit to be in an on state when detecting that the voltage from the standby power supply circuit is a low voltage; And a voltage detection circuit that controls the switching circuit to be turned off when it is detected that the voltage from the power supply circuit is not a low voltage.

  In the standby state, even when the voltage from the standby power supply circuit is equal to or lower than the voltage for operating the control means, the voltage for operating the control means can be supplied from the main power supply circuit to the control means.

  Hereinafter, preferred embodiments of the present invention will be specifically described with reference to the drawings. However, the present invention is not limited to these embodiments. FIG. 1 is a schematic circuit diagram showing a power supply circuit 1 according to a preferred embodiment of the present invention. The power supply circuit 1 includes a standby power supply circuit 2, a main power supply circuit 3, a microcomputer power supply circuit 4, a control unit 5, a voltage detection circuit 6, and a reset circuit 7. Note that the microcomputer power supply circuit 4 and the reset circuit 7 are not essential to the present invention.

  The standby power supply circuit 2 mainly supplies voltage to the control means (for example, the microcomputer) 5 and / or peripheral circuits (for example, a remote control signal receiving circuit and a display circuit) of the microcomputer 5 (not shown) in the standby state (standby state). Is a circuit for supplying Standby power supply circuit 2 includes a transformer 8 and a rectifier circuit 9. The transformer 8 has a primary winding connected to a commercial AC power supply (applied with an input AC voltage), and rectifies the input AC voltage by converting the input AC voltage to a predetermined voltage based on the turn ratio of the primary winding and the secondary winding. This is applied to the circuit 9. The rectifier circuit 9 rectifies and smoothes the voltage from the transformer 8 to generate a DC voltage. The rectifier circuit 9 includes a full-wave rectifier circuit D1 and a capacitor C1. The capacitor C1 mainly charges a voltage to be given to the microcomputer 5 in a standby state.

  The main power supply circuit 3 is connected to the microcomputer 5 and the main circuit 10 (a power supply destination circuit, such as an amplifier circuit) connected to the output terminal of the power supply circuit 1 in a normal operation state (power-on state). It is a circuit for supplying a voltage. The main power supply circuit 3 includes a transformer 11 and a rectifier circuit 12. The transformer 11 is connected to a commercial AC power source (given an input AC voltage), and converts the input AC voltage into a predetermined voltage based on the turn ratio of the primary winding and the secondary winding to the rectifier circuit 12. give. The rectifier circuit 12 rectifies and smoothes the voltage from the transformer 11 to generate a DC voltage. Rectifier circuit 12 includes a full-wave rectifier circuit D2 and a capacitor C2. Since the capacitor C2 is charged with a voltage to be supplied to the main circuit 10 and the microcomputer 5, a capacitor having a large capacity is employed.

  A switching circuit 13 is provided on the primary side of the transformer 11. The switching circuit 13 switches between the on state and the off state of the main power supply circuit 3, and typically employs a relay circuit. The relay circuit 13 includes a switch 13A and a winding 13B. The switch 13A has one end connected between the commercial AC power supply and the transformer 8, and the other end connected to the transformer 11. That is, the main power supply circuit 3 is connected to the subsequent stage of the switch 13A, and the standby power supply circuit 2 is connected to the previous stage of the switch 13A. When the switch 13A is turned off, only the main power supply circuit 3 is turned off, and the standby power supply circuit 2 is kept on. One end of the winding 13B is connected to the output end of the rectifier circuit 9, and the other end is connected to the collector of the transistor Q1 for relay drive. The base of the transistor Q1 is connected to the main power supply control terminal 5b of the microcomputer 5 through the diode D7, is connected to the output terminal of the voltage detection circuit 6 through the diode D8, and the emitter is grounded.

  The microcomputer power supply circuit 4 is a circuit that receives a voltage from the standby power supply circuit 2 and / or the main power supply circuit 3 and applies a constant voltage to the microcomputer 5. The microcomputer power supply circuit 4 includes diodes D3 and D4, a capacitor C3, and a stabilization circuit 14. The capacitor C3 is charged with a voltage to be supplied to the microcomputer 5. The stabilization circuit 14 is supplied with the voltage from the capacitor C3 and generates a stabilized DC voltage necessary for the operation of the microcomputer 5. The output terminal of the stabilization circuit 14 is connected to the voltage input terminal 5 a, the voltage detection circuit 6, and the reset circuit 7 of the microcomputer 5.

  The control means 5 controls the entire electronic device to which the power supply voltage is supplied from the power supply circuit 1, and a microcomputer (micro computer) can be typically employed. The microcomputer 5 controls the main power supply circuit 3 to be turned off when an instruction to shift to the standby state by a user operation is input via a remote controller or the like. Specifically, the microcomputer 5 outputs a signal (for example, a low level voltage) for turning off the relay circuit 13. On the other hand, the microcomputer 5 controls the main power supply circuit 3 to be in an ON state when an instruction to shift to the normal operation state is input through a remote controller or the like by a user operation. Specifically, the microcomputer 5 outputs a signal (for example, a high level voltage) for turning on the relay circuit 13.

  The microcomputer 5 includes a voltage input terminal 5a and a main power supply control terminal 5b. The voltage input terminal 5a is a terminal to which a voltage necessary for operating the microcomputer 5 from the microcomputer power supply circuit 4 is applied. The main power supply control terminal 5b is a terminal that outputs a signal for controlling the main power supply circuit 3 to an on state or an off state. The microcomputer 5 outputs a high level signal from the main power supply control terminal 5b when controlling the main power supply circuit 3 to the on state, and from the main power supply control terminal 5b when controlling the main power supply circuit 3 to the off state. Outputs a low level signal.

  The voltage detection circuit 6 detects whether or not the voltage from the standby power supply circuit 2 is a low voltage (whether or not it is equal to or less than a threshold voltage). Is controlled to turn on. Specifically, the voltage detection circuit 6 outputs a high-level signal for turning on the transistor Q1 when detecting a low voltage, and turns off the transistor Q1 when not detecting a low voltage. A high level signal for turning on is not output (that is, a low level signal is output). As a result, when the standby power supply circuit 2 has a low voltage in the standby state, and the voltage necessary for operating the microcomputer 5 cannot be supplied to the microcomputer 5, the main power supply circuit 3 is controlled to be in the on state. Thus, a voltage necessary for operating the microcomputer 5 from the main power supply circuit 3 can be supplied to the microcomputer 5.

  The voltage detection circuit 6 includes diodes D5 and D6, resistors R1 to R6, a capacitor C4, and a comparator 15. Each anode of the diodes D5 and D6 is connected to both ends of the secondary winding of the transformer 8, and each cathode is connected to one end of the capacitor C4 and one end of the resistor R1. The other end of the capacitor C4 is connected to the ground potential, and the other end of the resistor R1 is connected to one end of the resistor R2 and the inverting input terminal of the comparator 15. The other end of the resistor R2 is connected to the ground potential. The non-inverting input terminal of the comparator 15 is connected to the output terminal of the stabilization circuit 14 through the resistor R3, connected to the ground potential through the resistor R4, and output terminal of the stabilization circuit 14 through the resistors R5 and R6. And is connected to the output of the reset circuit 7. The output terminal of the comparator 15 is connected to the connection terminal of the resistors R5 and R6, and is connected to the anode of the diode D8.

  A voltage obtained by dividing the voltage (for example, about 3.3 V) from the microcomputer power supply circuit 4 by the resistors R3 and R4 is supplied to the non-inverting input terminal of the comparator 15 as the threshold voltage VREF. The voltage from the standby power supply circuit 2 is rectified by the diodes D5 and D6 and the capacitor C4, and the voltage whose voltage value is adjusted by the resistors R1 and R2 is supplied to the inverting input terminal of the comparator 15.

  When the voltage input to the inverting input terminal is larger than the threshold voltage VREF input to the non-inverting input terminal, the comparator 15 has a low voltage because the voltage from the standby power supply circuit 2 is larger than the threshold voltage. This is not detected, and a low level voltage is supplied to the base of the transistor Q1 via the diode D8. As a result, the relay switch 13A is controlled to the off state, and the main power supply circuit 3 is controlled to the off state. On the other hand, when the voltage input to the inverting input terminal is equal to or lower than the threshold voltage VREF input to the non-inverting input terminal, the comparator 15 determines that the voltage from the standby power supply circuit 2 is equal to or lower than the threshold voltage. It is detected that the voltage from the circuit 2 is low, and a high level voltage is supplied to the base of the transistor Q1 via the diode D8. As a result, the relay switch 13A is controlled to be on, and the main power supply circuit 3 is controlled to be on.

  The reset circuit 7 stops the operation of the comparator 15 by supplying a low level signal to the non-inverting input terminal of the comparator 15 immediately after the AC plug of the electronic device is inserted into the outlet and the AC power supply is input. Thus, a high level signal is prevented from being output from the comparator 15. Further, the reset circuit 7 does not supply a low level signal to the non-inverting input terminal of the comparator 15 when the output voltage of the stabilization circuit 14 becomes equal to or higher than a predetermined voltage after the input of the AC power supply is started. Become. As a result, the voltage obtained by dividing the voltage from the stabilization circuit 14 by the resistors R3 and R4 is supplied to the non-inverting input terminal of the comparator 15, and the comparator 15 is allowed to output a high level signal. Is done. The input of the reset circuit 7 is connected to the output of the stabilization circuit 14, and the output of the reset circuit 7 is connected to the non-inverting input terminal of the comparator 15.

  The operation of the power supply circuit 1 having the above configuration will be described. FIG. 2 is a time chart showing waveforms at each point of the power supply circuit 1 according to the first embodiment, and each symbol in FIG. 2 indicates a voltage waveform at a point given each symbol in FIG.

  At time t1, when the AC plug of the electronic device is inserted into the outlet, the voltage at the point A of the voltage detection circuit 6 (the input voltage at the inverting input terminal of the comparator 15) is combined with the rise in the voltage of the secondary winding of the transformer 8. Start to rise. From time t1 to time t6, the output of the main power supply control terminal 5b of the microcomputer 5 is at a low level (see point E voltage) and is in a standby state. On the other hand, after time t6, the output of the main power supply control terminal 5b of the microcomputer 5 is at a high level (refer to point E voltage) and is in a normal operation state.

  At time t2, the point A voltage exceeds the threshold voltage VREF. Here, since the output voltage (point B voltage) of the reset circuit 7 is at the low level until time t3, the voltage at the non-inverting input terminal of the comparator 15 is at the low level. As a result, the voltage at the point A is the threshold voltage. Even in the following case, the comparator 15 does not output a high-level signal and remains at a low level (refer to the point C voltage).

  At time t3 (at time t3, for example, the time when the delay time of the reset circuit 7 has elapsed after the output voltage of the stabilization circuit 14 has become equal to or higher than the predetermined voltage), the reset circuit 7 goes to the non-inverting input terminal of the comparator 15. The level voltage is not supplied (refer to point B voltage). As a result, the threshold voltage VREF is supplied to the non-inverting input terminal of the comparator 15.

  At time t3 to t4, the point A voltage is higher than the threshold voltage VREF, so the output voltage of the comparator 15 (see the point C voltage) is kept at the low level. As a result, the transistor Q1 is in an off state because the base voltage maintains a low level (see point D voltage), no current flows through the winding 13B, the switch 13A is in an off state, and the main power supply circuit 3 Is off. Therefore, when the voltage from the standby power supply circuit 2 is not low, the main power supply circuit 3 is turned off in the standby state.

  At time t4 (from time t4 to t5), the point A voltage becomes equal to or lower than the threshold voltage, so the output voltage of the comparator 15 (see point C voltage) becomes high level. As a result, the transistor Q1 is turned on because the base voltage is at a high level (see point D voltage), current flows through the winding 13B, the switch 13A is turned on, and the main power supply circuit 3 is turned on. . Therefore, when the voltage from the standby power supply circuit 2 is a low voltage, the main power supply circuit 3 is turned on even in the standby state, and the voltage from the main power supply circuit 3 passes through the microcomputer power supply circuit 4. It is supplied to the microcomputer 5. Accordingly, a voltage capable of operating the microcomputer 5 from the main power supply circuit 3 can be supplied to the microcomputer 5.

  At time t5 (from time t5 to t6), the point A voltage becomes higher than the threshold voltage VREF, so that the output voltage of the comparator 15 (refer to point C voltage) becomes low level again. As a result, the transistor Q1 is turned off because the base voltage is at a low level (see point D voltage), no current flows through the winding 13B, the switch 13A is turned off, and the main power supply circuit 3 is turned off. become. Therefore, when the voltage from the standby power supply circuit 2 is not low, the main power supply circuit 3 is turned off in the standby state.

  When an instruction to shift from the standby state to the normal operation state is input by a user operation at time t6, the microcomputer 5 outputs a high level signal from the main power supply control terminal 5b. Accordingly, the transistor Q1 is turned on because the base voltage is at a high level (see point D voltage), a current flows through the winding 13B, the switch 13A is turned on, and the main power supply circuit 3 is turned on. .

  FIG. 3 is a time chart showing the waveform at each point of the power supply circuit 1 according to the second embodiment, and each symbol in FIG. 3 shows a voltage waveform at the point given each symbol in FIG.

  At time t11, when the AC plug of the electronic device is inserted into the outlet, the voltage at the point A starts to increase with the increase in the voltage of the secondary winding of the transformer 8. From time t11 to time t13, the output of the main power supply control terminal 5b of the microcomputer 5 is at a low level (see point E voltage) and is in a standby state. On the other hand, after time t13, the output of the main power supply control terminal 5b of the microcomputer 5 is at a high level (refer to point E voltage) and is in a normal operation state.

  At time t12, the reset circuit 7 does not supply a low level voltage to the non-inverting input terminal of the comparator 15, and as a result, the threshold voltage VREF is supplied to the non-inverting input terminal of the comparator 15.

  Further, at time t12 (from time t12 to t13), the point A voltage is equal to or lower than the threshold voltage, and therefore the output voltage of the comparator 15 (see point C voltage) becomes high level. As a result, since the base voltage of the transistor Q1 is at a high level (see point D voltage), the transistor Q1 is turned on, a current flows through the winding 13B, the switch 13A is turned on, and the main power supply circuit 3 is turned on. Become. Therefore, when the voltage from the standby power supply circuit 2 is low, the main power supply circuit 3 is turned on even in the standby state, and the voltage from the main power supply circuit 3 passes through the microcomputer power supply circuit 4. Are supplied to the microcomputer 5. Accordingly, a voltage capable of operating the microcomputer 5 from the main power supply circuit 3 can be supplied to the microcomputer 5.

  When an instruction to shift from the standby state to the normal operation state is input by a user operation at time t13, the microcomputer 5 outputs a high level signal from the main power supply control terminal 5b. Therefore, the base voltage of the transistor Q1 is at a high level (refer to the voltage at the point D), and the transistor Q1 is kept in the on state, the current flows through the winding 13B, the switch 13A is kept on, and the main power supply circuit 3 is turned on. maintain.

  As described above, according to the present embodiment, the voltage detection circuit 6 performs control so that the main power supply circuit 3 is turned on when detecting that the voltage from the standby power supply circuit 2 is low in the standby state. Therefore, an operable voltage can be supplied from the main power supply circuit 3 to the microcomputer 5.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment. Note that since the comparator 15 performs a hysteresis operation with the resistors R5 and R6, the B point voltage is not actually constant. This is to prevent the transistor Q1 from being frequently switched between the on state and the off state in the vicinity of the threshold voltage.

  The present invention can be suitably employed for a power circuit of an audio amplifier, for example.

1 is a circuit diagram showing a power supply circuit 1 according to a preferred embodiment of the present invention. 3 is a time chart showing the operation of the power supply circuit 1. 3 is a time chart showing the operation of the power supply circuit 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Power supply circuit 2 Standby power supply circuit 3 Main power supply circuit 4 Microcomputer power supply circuit 5 Microcomputer 6 Voltage detection circuit 7 Reset circuit 15 Comparator

Claims (3)

A main power supply circuit that is provided with an input voltage and generates a voltage for operating the control means in a normal operation state;
A standby power supply circuit for generating a voltage to which the input voltage is applied and to operate the control means in a standby state;
A switching circuit that turns off the main power supply circuit by turning off, and turns on the main power supply circuit by turning on;
In the standby state, it is detected whether or not the voltage from the standby power supply circuit is lower than the threshold voltage, and the switching circuit is turned on when it is detected that the voltage from the standby power supply circuit is lower than the threshold voltage. And a voltage detection circuit that controls the switching circuit to an off state when it is detected that a voltage from the standby power supply circuit is greater than the threshold voltage. The switching circuit includes a relay switch that controls the main power supply circuit to an on state or an off state,
A transistor for controlling the relay switch to an on state or an off state;
The voltage detection circuit compares the voltage from the standby power supply circuit with the threshold voltage, and turns on the relay switch to the control electrode of the transistor when the voltage from the standby power supply circuit is equal to or lower than the threshold voltage. A comparator for supplying a signal for turning on, and for supplying a signal for turning off the relay switch to a control electrode of the transistor when a voltage from the standby power supply circuit is larger than the threshold voltage; The power supply circuit according to claim 1. A main power supply circuit that is provided with an input voltage and generates a voltage for operating the control means in a normal operation state;
A standby power supply circuit for generating a voltage to which the input voltage is applied and to operate the control means in a standby state;
A switching circuit that turns off the main power supply circuit by turning off, and turns on the main power supply circuit by turning on;
In the standby state, it is detected whether or not the voltage from the standby power supply circuit is a low voltage, and when the voltage from the standby power supply circuit is detected to be low, the switching circuit is controlled to be in an on state. And a voltage detection circuit that controls the switching circuit to be turned off when it is detected that the voltage from the standby power supply circuit is not a low voltage.

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