JP2019047655A - Semiconductor device for power supply control, power supply device, discharge method of x capacitor, and switch control method - Google Patents

Abstract

To provide a semiconductor device for control structuring an insulation type DC power supply device, capable of reducing a low power consumption in a standby mode while securing a minimal operation of a circuit.SOLUTION: A semiconductor device for control, comprises: a high voltage input monitoring circuit that monitors a voltage of a high voltage input start terminal to which an AC voltage before rectification is input; a second power supply terminal to which a reception element which can receive a command signal from an external part is connected; a command input terminal to which current-voltage conversion means that is connected to the reception element in series and converts a current flowing through the reception element is converted to a voltage is connected; a first power supply line provided between the high voltage input start terminal and a first power supply terminal and first switching means provided onto the first power supply line; a second power supply line provided between the high voltage input start terminal and a second power supply terminal and second switching means provided onto the second power supply line; a zener diode connected between the second power supply line and a ground point; and a detection circuit that compares the voltage of a command input terminal with a predetermined voltage value, and detects the presence of the input.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a power supply control semiconductor device, and more particularly to a technique effective for use in a primary side control semiconductor device constituting an insulated DC power supply device including a voltage conversion transformer.

  The DC power supply device includes an insulated AC circuit composed of a diode bridge circuit that rectifies an AC power supply, and a DC-DC converter that steps down the DC voltage rectified by the circuit and converts it into a DC voltage having a desired potential. -There is a DC converter. As such an AC-DC converter, for example, a switching element connected in series with a primary winding of a voltage conversion transformer is turned on / off by a PWM (pulse width modulation) control method, a PFM (pulse frequency modulation) control method, or the like. Thus, a switching power supply device is known in which the current induced in the primary winding is controlled to control the voltage induced in the secondary winding.

  In addition, a switching control type AC-DC converter uses a transformer with an auxiliary winding to rectify and smooth the voltage induced in the auxiliary winding when an electric current is intermittently passed through the primary winding. Is supplied as a power supply voltage to the power supply control circuit (primary side control IC), and the control IC is configured to include an internal power supply circuit (regulator) that generates an operating voltage of a level suitable for the internal circuit. (See Patent Document 1). Such AC-DC converters are widely used in peripheral equipment for personal computers and household electric appliances.

JP 2014-082831 A Japanese Patent Laid-Open No. 2006-158399 International Publication No. 2014/006838 International Publication No. 2014/129126

  For personal computer peripherals such as printers and household electrical appliances, turn on the power switch only when using it, and turn off the power switch with the AC plug connected to the outlet after use. There is something to do. Since an AC-DC converter as a power supply device built in such an electronic device continues a certain operation as long as the AC plug is connected to an outlet, how can the power consumption be reduced during standby? How is the issue? It is known that the standby power consumption of the AC-DC converter accounts for a very high proportion of the current consumption of the primary control IC.

  Therefore, the present inventor has two internal power supply circuits (regulators) built in, and one internal power supply circuit of the two internal power supply circuits is always in an operating state, and the other internal power supply circuit has a feedback voltage monitor. An invention relating to a primary control IC having a standby mode configured to be able to stop operation in accordance with a stop control signal output from a circuit has been filed earlier (see Patent Document 2). In addition, the power supply control circuit is configured to perform an operation called a burst mode in which the operation of the internal circuit is temporarily stopped at a light load and the switching control signal output from the driver is fixed at a low level. There is.

  However, in the primary side control IC described in Patent Document 2, in the standby mode, in addition to the one internal power supply circuit, a circuit for starting the IC, a circuit for controlling the start, and normal mode noise Since the discharge circuit of the X capacitor, the reference voltage circuit, and the bias circuit connected between the AC terminals are operated in order to attenuate the noise, there is a problem that the power consumption during standby is not sufficiently reduced.

As an invention relating to a switching power supply device having a function of shifting to an off mode in response to an external command and a switching power supply device having an off mode delay circuit that delays the transition to the off mode during standby (standby), for example, a patent Some are described in documents 3 and 4. However, these patent documents do not disclose circuits operated in the off mode and how to supply power to those circuits.
The present invention has been made paying attention to the above-described problems, and in the control semiconductor device constituting the isolated DC power supply device, the power consumption during standby is greatly increased while guaranteeing the operation of the minimum necessary circuit. The purpose is to reduce it.

In order to achieve the above object, the present invention
A switching element for passing a current intermittently through the primary winding of the transformer for voltage conversion, a voltage proportional to the current flowing through the primary winding of the transformer, and an output voltage detection from the secondary side of the transformer A power supply control semiconductor device that generates and outputs a drive pulse for on / off control when a signal is input,
An AC input AC voltage or a high voltage input start terminal to which a voltage after rectification by a diode bridge is input;
A first power supply terminal to which a voltage induced in the auxiliary winding of the transformer is input;
A second power supply terminal to which a receiving element capable of receiving an external command signal is connected;
A command input terminal connected in series with the receiving element and connected to a current-voltage converting means for converting a current flowing through the receiving element into a voltage;
A first power supply line provided between the high-voltage input activation terminal and the first power supply terminal, and first switch means provided on the first power supply line;
A second power supply line provided between the high-voltage input activation terminal and the second power supply terminal, and second switch means provided on the second power supply line;
A zener diode connected between the second power line and a ground point;
A bias circuit connected to the second power supply line;
A detection circuit connected to the bias circuit for detecting the presence or absence of an input by comparing a voltage of the command input terminal with a predetermined voltage value;
Is provided.
Then, when the detection circuit detects that the voltage of the command input terminal is below a predetermined voltage value under a predetermined condition, the first switch means is turned on and the second switch means is turned off. And when the detection circuit detects that the voltage at the command input terminal exceeds a predetermined voltage value, the first switch means is turned off and the second switch means is turned on. .

  According to the configuration described above, the second power supply terminal to which the receiving element capable of receiving a command signal from the outside is connected, the second power supply line provided between the high-voltage input activation terminal and the second power supply terminal, Two switch means, and a Zener diode connected between the second power supply line and the ground point, and the first circuit when the detection circuit detects that the voltage of the command input terminal exceeds a predetermined voltage value. Since the switch means is turned off and the second switch means is turned on, the internal power supply circuit is stopped in response to an external command signal, and the zener diode functions as the power supply means, and the bias connected to the second power supply line Since the circuit and the detection circuit can be operated, it is possible to shift to an off mode in which only a necessary minimum circuit operates, and power consumption during standby can be greatly reduced.

Here, preferably, an internal power supply circuit connected to the first power supply line;
Third switch means provided between the Zener diode and the second power supply terminal (on the second power supply line);
A fourth switch means for supplying an internal voltage generated by the internal power supply circuit to the second power supply line;
The third switch means is turned off, the fourth switch means is turned on when the detection circuit detects that the voltage of the command input terminal is lower than a predetermined voltage value, and the command input terminal The third switch means is turned on and the fourth switch means is turned off when it is detected that the above voltage exceeds a predetermined voltage value.

  According to this configuration, since the bias circuit and the detection circuit are operated by the power supply voltage generated by the Zener diode in the off mode, the reference voltage circuit for operating all the circuit blocks required in the normal operation mode is operated. The internal power supply circuit, the bias circuit, etc. can all be stopped, and the power consumption in the off mode can be greatly reduced.

Preferably, when the detection circuit detects that the voltage at the command input terminal exceeds a predetermined voltage value, the operation of the internal power supply circuit is stopped based on the output signal of the detection circuit. Configure as follows.
With such a configuration, the operation of the internal power supply circuit can be quickly stopped in the off mode, thereby reducing wasteful power consumption.

Further, preferably, the fourth switch means is formed of a field effect transistor, and corresponding to the fourth switch means, when the Zener voltage is higher than the internal voltage, a second power supply terminal in the third power supply line. A back gate control circuit is provided for preventing a current from flowing backward to the internal power supply circuit.
Thereby, it is possible to prevent a reverse current from flowing through the parasitic diode of the field effect transistor as the fourth switch means, thereby reducing useless power consumption.

Preferably, the discharging means connected between the high-voltage input starting terminal and a ground point,
A high-voltage input monitoring circuit for monitoring that an AC voltage is input to the high-voltage input starting terminal and a discharge control circuit having a time measuring means;
The discharge control circuit is operable with a bias current from the bias circuit, and the discharge when the AC voltage input to the high-voltage input start-up terminal is not detected for a predetermined time by the high-voltage input monitoring circuit. The means is configured to conduct.

  According to such a configuration, when the AC plug is pulled out from the outlet in the off mode and the AC input is interrupted, the discharging means can be made conductive and the residual charge of the X capacitor can be discharged quickly. Since there is no need to connect a discharging resistor in parallel with the X capacitor, power consumption in the normal operation mode can be reduced.

  According to the present invention, in a control semiconductor device (primary-side control IC) that constitutes an insulation type DC power supply device that includes a transformer for voltage conversion and controls the output by turning on and off the current flowing through the primary-side winding. Power consumption during standby can be greatly reduced. Further, according to the present invention, there is an effect that it is possible to provide a power supply control semiconductor device that has an off mode that consumes very little power during standby and has a function of shifting to the off mode by an external command. is there.

It is a circuit block diagram which shows one Embodiment of the AC-DC converter as an insulation type DC power supply device which concerns on this invention. FIG. 2 is a block diagram illustrating a configuration example of a primary switching power supply control circuit (power supply control IC) of a transformer in the AC-DC converter of FIG. 1. It is a wave form diagram which shows the mode of the change of the voltage of each part in IC for power supply control of embodiment. FIG. 6 is a characteristic diagram showing a relationship between a switching frequency and a feedback voltage VFB in the power supply control IC of the embodiment. It is a circuit block diagram which shows the structural example of the off mode control circuit and discharge circuit in power supply control IC of embodiment.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings.
FIG. 1 is a circuit configuration diagram showing an embodiment of an AC-DC converter as an insulated DC power supply device to which the present invention is applied.

  The AC-DC converter according to this embodiment includes an X capacitor Cx connected between AC terminals to attenuate normal mode noise, a noise blocking filter 11 including a common mode coil, and an AC voltage (AC). A diode bridge circuit 12 that rectifies and converts to a DC voltage, a smoothing capacitor C1 that smoothes the rectified voltage, a primary winding Np, a secondary winding Ns, and an auxiliary winding Nb. A transformer T1, a switching transistor SW composed of an N-channel MOSFET connected in series with the primary side winding Np of the transformer T1, and a power supply control circuit 13 for driving the switching transistor SW. In this embodiment, the power supply control circuit 13 is formed as a semiconductor integrated circuit (hereinafter referred to as a power supply control IC) on a single semiconductor chip such as single crystal silicon.

  The secondary side of the transformer T1 is connected between the rectifying diode D2 connected in series with the secondary side winding Ns and between the cathode terminal of the diode D2 and the other terminal of the secondary side winding Ns. The smoothing capacitor C2 is provided, and the primary winding Np is rectified and smoothed by rectifying and smoothing the AC voltage induced in the secondary winding Ns by intermittently passing a current through the primary winding Np. And DC voltage Vout corresponding to the winding ratio of the secondary winding Ns.

  Further, the secondary side of the transformer T1 is provided with a coil L3 and a capacitor C3 which constitute a filter for cutting off switching ripple, noise, etc. generated by the switching operation on the primary side, and detects the output voltage Vout. And a photodiode 15a as a light emitting side element of a photocoupler connected to the detection circuit 14 and transmitting a signal corresponding to the detection voltage to the power supply control IC 13 is provided. On the primary side, a phototransistor 15b is provided as a light receiving side element that is connected between the feedback terminal FB of the power supply control IC 13 and the ground point and receives a signal from the detection circuit 14.

The primary side of the AC-DC converter of this embodiment is connected between the rectifying diode D0 connected in series with the auxiliary winding Nb and between the cathode terminal of the diode D0 and the ground point GND. A rectifying / smoothing circuit including a smoothing capacitor C0 is provided, and a voltage rectified and smoothed by the rectifying / smoothing circuit is applied to the power supply terminal VDD1 of the power supply control IC13.
On the other hand, the power supply control IC 13 is provided with a high voltage input starting terminal HV to which a voltage before being rectified by the diode bridge circuit 12 is applied via the diodes D11 and D12 and the resistor R1. Immediately after the plug is inserted into the outlet), the power supply control IC 13 can be operated before the voltage is induced in the auxiliary winding Nb at the time of power supply start-up by the voltage from the high-voltage input start-up terminal HV. Has been.

  Further, in the present embodiment, a current detection resistor Rs is connected between the source terminal of the switching transistor SW and the ground point GND, and a connection node N1 between the switching transistor SW and the current detection resistor Rs A resistor R2 is connected between the power detection IC 13 and the current detection terminal CS. Further, a capacitor C4 is connected between the current detection terminal CS of the power supply control IC 13 and the ground point, and a low-pass filter is configured by the resistor R2 and the capacitor C4.

Next, a specific configuration example of the power supply control IC 13 will be described with reference to FIG.
As shown in FIG. 2, the power supply control IC 13 of this embodiment includes an oscillation circuit (VCO) 31 that oscillates at a frequency corresponding to the voltage VFB of the feedback terminal FB, and an oscillation signal φc generated by the oscillation circuit 31. A clock generation circuit 32 composed of a circuit such as a one-shot pulse generation circuit for generating a clock signal CK that gives a timing to turn on the primary side switching transistor SW based on the RS flip-flop 33 set by the clock signal CK, A driver (drive circuit) 34 that generates a drive pulse GATE of the switching transistor SW according to the output of the flip-flop 33 is provided.

  The power supply control IC 13 also amplifies the voltage Vcs input to the current detection terminal CS, and the potential Vcs ′ amplified by the amplifier 35 and a comparison voltage (threshold for monitoring an overcurrent state). A comparator 36a as a voltage comparison circuit for comparing the hold voltage (Vocp), a waveform generation circuit 37 for generating a voltage RAMP having a predetermined waveform as shown in FIG. 3 (A) based on the voltage VFB of the feedback terminal FB, A comparator 36b for comparing the waveform potential Vcs ′ amplified by the amplifier 35 and the waveform RAMP generated by the waveform generation circuit 37 as shown in FIG. 3B, and the logical sum of the outputs of the comparators 36a and 36b. OR gate G1 is provided. In the power supply control IC 13 of this embodiment, the voltage RAMP in FIG. 3A is generated so that the voltage decreases with a certain slope from the FB voltage VFB.

  The output RS of the OR gate G1 (see FIG. 3C) is input to the reset terminal of the flip-flop 33 via the OR gate G2, thereby giving a timing for turning off the switching transistor SW. Yes. A pull-up resistor or a constant current source is provided between the feedback terminal FB and the internal power supply voltage terminal, and a current flowing through the phototransistor 15b is converted into a voltage by the resistor. The waveform generation circuit 37 is provided to prevent subharmonic oscillation, and the voltage VFB may be directly or level-shifted and input to the comparator 36b. Furthermore, when the power is turned on when no significant voltages VFB and Vcs are generated at the feedback terminal FB and the current detection terminal CS, the flip-flop is used to gradually increase the primary side current so that excessive current does not flow through the primary side winding. A soft start circuit for generating a signal for resetting the group 33 may be provided.

  Further, the power supply control IC 13 of this embodiment includes a frequency control circuit 38 that changes the oscillation frequency of the oscillation circuit 31, that is, the switching frequency, according to the characteristics shown in FIG. 4 according to the voltage VFB of the feedback terminal FB. The frequency f1 in FIG. 4 is set to a value such as 22 kHz, and f2 is set to an arbitrary value in a range such as 66 kHz to 100 kHz. The frequency control circuit 38 clamps a buffer such as a voltage follower and a voltage VFB of the feedback terminal FB to 0.7 V when the voltage VFB is 1.8 V or lower, and 2.1 V when the voltage VFB is 2.1 V or higher, for example. And a clamp circuit. Although not shown, the oscillation circuit 31 includes a current source that supplies a current according to the voltage from the frequency control circuit 38, and can be configured by an oscillator whose oscillation frequency changes depending on the magnitude of the current that the current source flows.

  Further, in the power supply control IC 13 of the present embodiment, based on the clock signal CK output from the clock generation circuit 32, the duty (Ton / Tcycle) of the drive pulse GATE is a predetermined maximum value (for example, 85%). A duty limiting circuit 39 for generating a maximum duty reset signal for limiting so as not to exceed (90%) is provided. Then, the maximum duty reset signal output from the duty limiting circuit 39 is supplied to the flip-flop 33 through the OR gate G2, and when the pulse reaches the maximum duty, the switching transistor SW is reset at that time. Is immediately turned off.

  Further, the power supply control IC 13 of the present embodiment includes a switch S0 composed of a high voltage MOS transistor (field effect transistor) provided on the power supply line VDL1 between the high voltage input start terminal HV and the power supply terminal VDD1, When a voltage is input to the high-voltage input start-up terminal HV, the switch S0 is turned on to start the IC, and the voltage at the high-voltage input start-up terminal HV is monitored. A discharge circuit 40 is provided for detecting whether or not the plug of the AC power source is disconnected from the outlet and determining that it is disconnected, for discharging the X capacitor Cx. Whether or not the plug is disconnected is determined, for example, by detecting that the AC input voltage has not fallen below a predetermined value (for example, 75% of the peak value) within a certain period of time (for example, 30 milliseconds). Can do.

  The switch S0 is turned on immediately after an AC voltage is input to the high-voltage input start-up terminal HV, and a current flows from the high-voltage input start-up terminal HV to the capacitor C0 connected to the power-supply terminal VDD1, thereby causing the voltage of the power-supply terminal VDD1. And the power supply terminal VDD1 is turned off when the voltage reaches a predetermined value (for example, 21V) or more. Further, an internal power supply circuit (regulator) 71 is connected to the power supply line L1, and when the switch S0 is turned on, the voltage of the power supply terminal VDD1 gradually rises, so that the internal power supply circuit 71 starts operation. An internal power supply voltage is supplied to the internal circuit. Further, when the power supply terminal VDD1 becomes equal to or higher than a predetermined value (for example, 21V), the internal circuit starts to operate and a drive pulse GATE is generated. Thereafter, a voltage is supplied from the auxiliary winding Nb to the power supply terminal VDD1. It becomes like this.

  The power control IC 13 includes a terminal OFF to which a phototransistor 15c that receives a command signal for shifting to an off mode from a microcomputer or the like (not shown), an off mode control circuit 60 connected to the terminal OFF, Zener diode ZD for generating a power supply voltage to be supplied to a circuit that operates in a mode (a bias circuit for passing a current to the comparator in discharge circuit 40 and off-mode control circuit 60), and the power supply voltage generated by Zener diode ZD to the discharge circuit A power supply line VDL2 to be supplied to 40, a switch S2 provided on the power supply line VDL2, and an off-time power supply terminal VDD2 to which one end of the power supply line VDL2 is connected are provided.

  A capacitor C5 for stabilizing the power supply voltage generated by the Zener diode ZD is connected to the off-time power supply terminal VDD2, and the collector terminal of the phototransistor 15c is connected to the emitter terminal of the phototransistor 15c. Series resistors R11 and R12 are connected to the ground point GND. The connection node between the resistors R11 and R12 is connected to the terminal OFF. When the phototransistor 15c receives a command signal for shifting to the off mode from a microcomputer or the like not shown in the drawing, a current flows through the resistors R11 and R12. The potential of the connection node of the resistors R11 and R12 rises, and this is detected by the off mode control circuit 60 to stop the operation of an internal power supply circuit 71 described later, and the switch S1 on the power supply line VDL1 is turned off. Has been.

FIG. 5 shows a configuration example of the discharge circuit 40 and the off-mode control circuit 60 in the power supply control IC of the embodiment of FIG.
As shown in FIG. 5, the discharge circuit 40 includes a discharge means 44 comprising a resistor Rd and a switch Sd connected in series with the switch S0 and the switch S1 between the high voltage input starting terminal HV and the ground point. A discharge control circuit 42 having a comparator (voltage comparison circuit) to detect the AC input potential to the high-voltage input starting terminal HV and controlling the discharge switch Sd on and off, and a reference used by the discharge control circuit 42 And a resistance voltage dividing circuit 43 that generates the voltage Vref1. The resistance voltage dividing circuit 43 also generates a reference voltage Vref0 used by the off mode control circuit 60.

The off-mode control circuit 60 compares the reference voltage Vref0 generated by the resistance voltage dividing circuit 43 with the voltage at the terminal OFF, and detects whether or not a power-off command signal is input to the phototransistor 15c from a microcomputer or the like. An off-detection comparator 61, and a bias circuit 62 that generates a current Ibias1 for operating the comparator 61. The bias circuit 62 also generates an operating current Ibias2 for the comparator in the discharge control circuit 42.
Specifically, the bias circuit 62 includes a constant voltage circuit that generates a constant voltage that does not have temperature characteristics, and a constant current source (constant current transistor) that supplies a current proportional to the constant voltage from the constant voltage circuit. The constant current transistor of the bias circuit 62 and the current transistor of the comparator in the discharge circuit 40 and the off detection comparator 61 are connected in a current mirror so that an operating current flows through each comparator. Yes.

  Further, as shown in FIG. 5, a power supply line VDL1 is connected between the high voltage input startup terminal HV and the power supply terminal VDD1, and a high voltage MOS transistor controlled by the startup circuit 50 is connected to the power supply line VDL1. A switch S0 composed of a (field effect transistor) is provided. The switch S0 is turned on immediately after an AC voltage is input to the high-voltage input start-up terminal HV, and the power supply terminal VDD1 has a voltage equal to or higher than a predetermined value (for example, 21 V). When turned off. Further, an internal power supply circuit (regulator) 71 is connected to the power supply line L1, and when the switch S0 is turned on, the internal power supply circuit 71 starts operation and supplies the internal power supply voltage REG to the internal circuit. Then, the internal circuit operates to generate the drive pulse GATE, and then the voltage from the auxiliary winding is supplied to the power supply terminal VDD1, and the internal circuit is supplied from the power supply terminal VDD1 with the switch S0 turned off. Operates with voltage.

  The gate terminal as the control terminal of the switch S0 is provided in parallel with the resistors R7 and R8 and the enhancement type MOS transistor Q1 connected in series between the source terminal of the switch S0 and the ground point, and the Q1. A switch control circuit 51 comprising a Zener diode D3 for clamping is connected. By turning on Q1, the gate terminal of the switch S0, which is a depletion type MOS transistor, is sufficient for the source voltage (high voltage switch By applying a negative voltage (above the threshold voltage of S0), the channel can be made non-conductive (a state where no drain current flows). When Q1 is turned off, S0 is turned on by the voltage level of the power supply terminal VDD1.

  A signal from the start control circuit 52 is applied to the gate terminal of the MOS transistor Q1, and the MOS transistor as the power supply switch S0 is turned on by turning off Q1. The start control circuit 52 has a built-in voltage comparator, which turns on the switch S0 when the voltage of the power supply terminal VDD1 is 6.5 V or less, for example, and turns off the switch S0 when the voltage of the power supply terminal VDD1 becomes 21 V or more, for example. To work. In the present specification, a combination of the switch control circuit 51 and the start control circuit 52 corresponds to the activation circuit 50.

  Further, as shown in FIG. 5, a switch S1 is provided in series with the switch S0 on the power supply line VDL1 between the high-voltage input activation terminal HV and the power supply terminal VDD1, and the connection between S0 and S1 is provided. On the power supply line VDL2 connecting the node and the power supply terminal VDD2, MOS transistors S2 and S3 as switch elements are provided in series. The discharge control circuit 42, the resistance voltage dividing circuit 43, and the bias circuit 62 are connected to the power supply line VDL2. Further, a resistance element Rt for limiting a current flowing from the high voltage input starting terminal HV is connected between the MOS transistors S2 and S3 on the power supply line VDL2, and a power supply terminal is connected between the power supply line VDL2 and the ground point. A Zener diode ZD having a function of clamping the voltage of VDD2 is connected.

  Furthermore, the power supply line VDL2 is connected to a power supply line VDL3 that supplies the internal power supply voltage REG from the internal power supply circuit 71, and a MOS transistor S4 is provided as a switch element on the power supply line VDL3. The MOS transistor S4 and the switch S1 on the power supply line VDL1 are turned on by the output signal of the AND gate G6 that takes the logical product of the output of the off detection comparator 61 and the signal ST output from the start control circuit 52. The MOS transistors S2 and S3 on the power supply line VDL2 are controlled to be turned on and off by a signal obtained by inverting the output of the AND gate G6 by the inverter INV2.

The signal ST output from the start control circuit 52 is a signal for setting all the circuits in the IC to an operating state by being set to a high level when the voltage of the power supply terminal VDD1 reaches, for example, 21V. By switching on and off the switches S1 to S4 as described above by a signal obtained by ANDing the signal ST and the output of the off detection comparator 61 (output of the AND gate G6), an external command input terminal is obtained. Regardless of the terminal OFF state, the IC can be activated when AC plug-in is performed. Specifically, immediately after the plug is removed and the AC input to the high voltage input activation terminal HV is not plugged in, the phototransistor 15c malfunctions due to an off signal from a secondary microcomputer or the like for some reason. Even if the command input terminal (terminal OFF) changes from a low level to a high level due to the influence of noise or the like, and the output of the off detection comparator 61 changes to a high level, the switch S1 is turned off and S2 is turned on to enter the off mode. There is no transition, and the switch S1 is turned on when AC plug-in is performed, so that the IC can be reliably activated.
Furthermore, in this embodiment, in preparation for the case where the potential of the power supply terminal VDD2 becomes higher than the internal power supply voltage REG, the source, drain and semiconductor of the transistor S4 are arranged in parallel with the MOS transistor S4 on the power supply line VDL3. A back gate control circuit 72 is provided for preventing a reverse current from flowing through a parasitic diode with the substrate.

Next, the operation of the off mode control circuit 60 will be described.
In the power-off mode, the current needs to be reduced to the minimum. As in the prior art, the current in the off mode cannot be reduced by moving various circuits using the power supply terminal VDD1 as a power supply. On the other hand, even if the power supply terminal VDD1 becomes 0V, it is necessary to operate the minimum necessary circuit (X capacitor discharge circuit). For this purpose, a power supply (VDD2) dedicated for power off for operating the circuit is necessary. This VDD2 is also one of the points of the present invention, and this embodiment is realized by a fairly simple method in which only a current flows from the HV terminal to the Zener.

In order to reduce power consumption, the AC input detection circuit (X capacitor discharge circuit), the off detection circuit (off detection comparator), and the minimum necessary circuit for operating the bias circuit and the reference circuit are operated. Each of the constituent circuits (for example, comparators) constituting each of these blocks is also reduced in consumption. In the present embodiment, since the AC input detection circuit uses VDD2 as the power supply, VDD2 is supplied with the voltage REG from the internal power supply circuit 71 instead of the zener in a mode other than the off mode.
In the power supply control IC of this embodiment, during normal operation, the output of the off detection comparator 61 that operates in response to the internal power supply voltage from the internal power supply circuit 71 is set to a low level, and the MOS transistor S2 on the power supply line VDL2 The S3 is off and the MOS transistor S4 on the power supply line VDL3 is on. The discharge control circuit 42, the resistance voltage dividing circuit 43, and the off detection comparator 61 operate with the internal power supply voltage REG from the internal power supply circuit 71. ing.

At this time, when the plug at the end of the power cord is removed from the outlet, the AC input to the high-voltage input activation terminal HV disappears, and when a predetermined time (for example, 30 milliseconds) elapses, the discharge control circuit 42 sets the discharge switch Sd. When turned on, the X capacitor Cx can be discharged.
In this way, by quickly discharging the residual charge of the X capacitor Cx (see FIG. 1) when the plug is pulled out, there is no need to provide a discharging resistor connected in parallel with the X capacitor Cx. It is possible to avoid an increase in standby power at the time of no load or standby in the industrial resistor.

  On the other hand, when the phototransistor 15c receives an off signal from the secondary side microcomputer or the like, the output of the off detection comparator 61 changes to a high level to enter the off mode, the operation of the internal power supply circuit 71 is stopped, and the power supply line MOS transistors S2 and S3 on VDL2 are turned on. Then, a current flows from the high voltage input starting terminal HV to the Zener diode ZD via S2 and S3, and the power supply line VDL2 is clamped to the Zener voltage, and this bias circuit is a circuit that performs the minimum necessary operation during standby by this power supply. 62, the operation of the off-detection comparator 61 and the discharge circuit 40 of the X capacitor are guaranteed.

Then, the operation of the circuits other than these circuits is stopped by stopping the operation of the internal power supply circuit 71, so that the power consumption of the IC can be reduced. Specifically, the power consumption at the time of AC100V input in this off mode can be suppressed to about 3 mW.
Further, since the operation of the discharge circuit 40 is guaranteed by supplying the bias current Ibias2 from the bias circuit 62 and the power supply of the power supply terminal VDD2 to the discharge circuit 40, the plug at the end of the power cord is connected to the outlet during the off mode. Even when the power is off, the AC switch to the high-voltage input start-up terminal HV disappears, and when 30 milliseconds elapses, the discharge switch Sd is turned on to discharge the X capacitor.

  When the off signal is not supplied to the phototransistor 15c, the output of the off detection comparator 61 changes to a low level, the operation of the internal power supply circuit 71 is released, and the MOS transistors S2 and S3 on the power supply line VDL2 are released. Is turned off and the switch S1 on the power supply line VDL1 is turned on (at this time, the operation of the IC is stopped, so that VDD1 becomes 6.5 V or less and S0 is turned on by the activation circuit 50). Therefore, a current flows from the high voltage input activation terminal HV to the capacitor C0 of the power supply terminal VDD1, the potential of the power supply line VDL1 rises, the internal power supply circuit 71 starts operating, and the internal circuit operates to start switching control. . When the off signal is not supplied, the MOS transistor S4 on the power supply line VDL3 is turned on, the internal power supply voltage LEG from the internal power supply circuit 71 is supplied to the bias circuit 62 and the resistance voltage dividing circuit 43, and the off detection comparator. 61 and the comparator in the discharge control circuit 42 are operated by the internal power supply voltage.

  The power supply control IC is provided with an input voltage dividing circuit 41 composed of resistors R3 and R4 connected in series between the high voltage input activation terminal HV and the ground point. In addition, the discharge control circuit 42 includes, for example, a voltage comparison circuit (comparator) that compares the voltage divided by the input voltage dividing circuit 41 with the reference voltage Vref1 generated by the resistance voltage dividing circuit 43, and a timer circuit. And comparing the potentials Vn2 and Vref1 of the connection node N2 of the resistors R3 and R4 to determine whether or not Vn2 is lower than Vref1, and measuring the time when Vn2 is not lower than Vref1 by the timer circuit. When it is determined that the measured time has exceeded, for example, 30 milliseconds, a signal for turning on the discharge switch Sd is output.

If the plug at the end of the power cord is pulled out from the outlet and no AC voltage is input to the high-voltage input start-up terminal HV, the potential Vn2 of the connection node N2 of the resistors R3 and R4 will not fall below Vref1. It is possible to detect that the plug has been removed from the outlet by measuring the time in the circuit. The resistors R3 and R4 are set to a resistance ratio (for example, 140: 1) that drops the voltage at the high-voltage input starting terminal HV to a voltage (for example, 6V) that is equal to or lower than the withstand voltage of the elements constituting the discharge circuit 40. The
The discharge control circuit 42 may be composed of a peak hold circuit, a voltage comparison circuit, and a timer circuit as described in Patent Document 2 described above.

(Modification)
The power supply control IC of the above embodiment is configured to maintain the off mode by continuously receiving the off mode signal from the secondary microcomputer or the like by the phototransistor 15c. A toggle flip-flop (T-FF) that reverses the output every time a pulse is input is provided, and a one-shot off-mode signal pulse is received from a secondary side microcomputer, etc. It may be configured to return from the off mode to the normal mode.

  Further, when the Zener voltage of the Zener diode ZD has a potential different from the internal power supply voltage generated by the internal power supply circuit 71, the off-detection comparator 61 generated by the resistance voltage dividing circuit 43 when shifting to the off mode. Since the reference voltage of the comparator in the discharge control circuit 42 is deviated from the potential in the normal mode, a switch element is provided in parallel with any of the resistors constituting the resistance voltage dividing circuit 43, and this switch is selected depending on the mode. The reference voltage generated by the resistance voltage dividing circuit 43 may be substantially the same by switching the on / off state of the element.

Although the invention made by the present inventor has been specifically described based on the embodiment, the present invention is not limited to the embodiment. For example, in the above-described embodiment, the switching transistor SW that intermittently passes a current through the primary winding of the transformer is an element separate from the power supply control IC 13. However, the switching transistor SW is incorporated into the power supply control IC 13. You may comprise as one semiconductor integrated circuit.
Furthermore, although the case where the present invention is applied to the power supply control IC constituting the flyback type AC-DC converter has been described in the above embodiment, the present invention is for power supply control constituting the forward type AC-DC converter. It can also be applied to ICs.

11 Line filter 12 Diode bridge circuit (rectifier circuit)
13 Power control circuit (Power control IC)
14 Secondary side detection circuit (IC for detection)
15a Photocoupler light-emitting diode 15b Photocoupler light-receiving transistor 15c Command signal receiving phototransistor 31 Oscillator 32 Clock generator 34 Driver (drive circuit)
36a Overcurrent detection comparator (overcurrent detection circuit)
36b Voltage / current control comparator (voltage / current control circuit)
37 Waveform generation circuit 38 Frequency control circuit 39 Duty limit circuit 40 Discharge circuit 41 Input voltage divider circuit 42 Discharge control circuit 43 Resistance voltage divider circuit 50 Start-up circuit 60 Off-mode control circuit 71 Internal power supply circuit HV High-voltage input start-up terminal VDD1 Power supply terminal Sd Discharge switch (Discharge means)

Claims (9)

A switching element for passing a current intermittently through the primary winding of the transformer for voltage conversion, a voltage proportional to the current flowing through the primary winding of the transformer, and an output voltage detection from the secondary side of the transformer A power supply control semiconductor device that generates and outputs a drive pulse for on / off control when a signal is input,
An AC input AC voltage or a high voltage input start terminal to which a voltage after rectification by a diode bridge is input;
A first power supply terminal to which a voltage induced in the auxiliary winding of the transformer is input;
A second power supply terminal to which a receiving element capable of receiving an external command signal is connected;
A command input terminal connected in series with the receiving element and connected to a current-voltage converting means for converting a current flowing through the receiving element into a voltage;
A first power supply line provided between the high-voltage input activation terminal and the first power supply terminal, and first switch means provided on the first power supply line;
A second power supply line provided between the high-voltage input activation terminal and the second power supply terminal, and second switch means provided on the second power supply line;
A zener diode connected between the second power line and a ground point;
A bias circuit connected to the second power supply line;
A detection circuit connected to the bias circuit for detecting the presence or absence of an input by comparing a voltage of the command input terminal with a predetermined voltage value;
A semiconductor device for power control, comprising:   When the detection circuit detects that the voltage of the command input terminal is below a predetermined voltage value under a predetermined condition, the first switch means is turned on, and the second switch means is turned off, When the detection circuit detects that the voltage of the command input terminal exceeds a predetermined voltage value, the first switch means is turned off and the second switch means is turned on. The power supply control semiconductor device according to claim 1. An internal power supply circuit connected to the first power supply line;
Third switch means provided between the Zener diode and the second power supply terminal;
A fourth switch means for supplying an internal voltage generated by the internal power supply circuit to the second power supply line;
The third switch means is turned off, the fourth switch means is turned on when the detection circuit detects that the voltage of the command input terminal is lower than a predetermined voltage value, and the command input terminal 3. The configuration according to claim 2, wherein the third switch means is turned on and the fourth switch means is turned off when it is detected that the voltage of the first voltage exceeds a predetermined voltage value. 4. Power control semiconductor device.   When the detection circuit detects that the voltage of the input terminal exceeds a predetermined voltage value, the operation of the internal power supply circuit is stopped based on the output signal of the detection circuit. The semiconductor device for power supply control according to claim 3.   The fourth switch means is formed by a field effect transistor, and corresponding to the fourth switch means, when the Zener voltage is higher than the internal voltage, the second power supply terminal to the internal power supply circuit in the third power supply line. 5. The power control semiconductor device according to claim 3, further comprising a back gate control circuit for preventing a current from flowing backward. Discharging means connected between the high-voltage input starting terminal and a ground point;
A high-voltage input monitoring circuit for monitoring that an AC voltage is input to the high-voltage input starting terminal and a discharge control circuit having a time measuring means;
The discharge control circuit is operable with a bias current from the bias circuit, and the discharge when the AC voltage input to the high-voltage input start-up terminal is not detected for a predetermined time by the high-voltage input monitoring circuit. 6. The power supply control semiconductor device according to claim 1, wherein the means is made conductive. A semiconductor device for power supply control according to any one of claims 1 to 6, a transformer for voltage conversion in which an AC input AC voltage or a voltage rectified by a diode bridge is input to a primary side, and the transformer A switching element connected to a primary side winding and controlled by the semiconductor device for power control, and a rectifier circuit provided on the secondary side of the transformer for voltage conversion,
When an X capacitor is connected between the input terminals of the AC input, and a rectifying element is connected between the terminal of the X capacitor and the high voltage input starting terminal, and the discharging means is conducted, the rectifying element, A power supply device, characterized in that a discharge current flows through the high-voltage input starting terminal and the high-voltage switch element. A semiconductor device for power supply control according to any one of claims 1 to 6, a transformer for voltage conversion in which an AC input AC voltage or a voltage rectified by a diode bridge is input to a primary side, and the transformer Discharge of the X capacitor in the power supply device comprising: a switching element connected to the primary winding of the power supply and controlled by the power supply control semiconductor device; and a rectifier circuit provided on the secondary side of the transformer for voltage conversion A method,
A first step of comparing a voltage obtained by dividing the voltage supplied through the rectifying element with a predetermined reference voltage;
A second step of starting a timing operation in response to detecting that the divided voltage has fallen below the predetermined reference voltage;
A third step in which, when a predetermined time is counted in the second step, the discharge means is conducted and a discharge current is caused to flow through the rectifying element;
A method for discharging an X capacitor, comprising: An AC input AC voltage or a high voltage input start terminal to which a voltage after rectification by a diode bridge is input;
A first power supply terminal to which a voltage induced in the auxiliary winding of the transformer is input;
A second power supply terminal to which a receiving element capable of receiving an external command signal is connected;
A command input terminal to which an external command signal is input;
A first power supply line provided between the high-voltage input activation terminal and the first power supply terminal, and first switch means provided on the first power supply line;
A second power supply line provided between the high-voltage input activation terminal and the second power supply terminal, and second switch means provided on the second power supply line;
A zener diode connected between the second power line and a ground point;
A switching element for passing a current intermittently through the primary winding of the voltage conversion transformer, a voltage proportional to the current flowing through the primary winding of the transformer and an output from the secondary side of the transformer A switch control method in a power supply control semiconductor device that generates and outputs a drive pulse for on / off control when a voltage detection signal is input,
A first step of detecting whether a command signal is input to the command input terminal;
When it is detected that a command signal is input to the command input terminal under a predetermined condition, the first switch means is turned on, the second switch means is turned off, and the command signal is input to the command input terminal. A second step of turning off the first switch means and turning on the second switch means when it has been detected that
A switch control method in a power supply control semiconductor device, comprising:

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