JP2008035656A - Power supply circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a power supply circuit and a device as a load of the power supply circuit from being damaged by detecting an abnormality in a digital control unit, before a switching element starts operation in the power supply device that executes step-up operation or step-down operation and generates an AC voltage by switching operation. <P>SOLUTION: The power supply circuit is provided with a power block which includes the switching element applied with a driving signal, so as to execute the switching operation and a drive circuit generating the driving signal on the basis of a control signal; at least one detection circuit which detects a voltage or a current at a prescribed part in the power block so as to output a detection signal; a control block which executes digital signal processing on the basis of the detection signal so as to generate the control signal; and a diagnosis circuit that determines whether the control block is excellently operated or not after a power supply is turned on, so as to allow the driving signal to be applied to the switching element after determining that the control block is well operated. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention generally relates to a power supply circuit used in an electronic device, and more particularly to a switching power supply circuit that performs step-up or step-down by a switching operation, or an inverter that generates an AC voltage by a switching operation.

  In recent years, with the reduction in size and weight of electronic devices, switching power supplies that step up or step down by switching operations and inverters that generate AC voltage by switching operations are widely used as power sources that are small and light and can efficiently extract power. in use. In a power supply that performs such a switching operation, high-speed and high-precision control is required for the switching element, and control using a digital circuit is being considered instead of control using a conventional analog circuit.

  By using a digital circuit, there is a demerit that the frequency band of the control signal is limited or a quantization error is generated, but the control circuit can be easily downsized by integrating the circuit. Also, since the control circuit can be generalized by generalizing the control algorithm, the same control circuit can be combined with a plurality of types of switching elements having different capabilities according to various requirements for the power supply circuit. It becomes easy. Furthermore, future development is expected in the digital control technology.

  As a related technique, the following Patent Document 1 discloses using a digital signal processor (DSP) for performing digital control in a switching power supply device. According to this switching power supply device, when an overcurrent state occurs, the drive pulse of the switching element can be limited for each switching period. For example, the device is abnormal as when the output terminal is accidentally short-circuited. Even if a situation occurs, it is possible to quickly and accurately perform control. However, the DSP may perform an unexpected operation due to external noise or the like, and it is necessary to prevent damage to the switching power supply device or a device serving as a load by detecting such a DSP runaway at an early stage. Arise.

Patent Document 2 below discloses a switching power supply capable of preventing device destruction due to DSP runaway. This switching power supply includes a current value detection circuit arranged on the primary side of a transformer that detects a current flowing through the switching element that drives the transformer, a digital control unit that drives the switching element, and a digital signal based on the current value detection signal. And a digital control unit abnormality detection circuit for detecting a control unit abnormality, wherein the digital control unit turns off the switching element based on the digital control unit abnormality detection signal. However, if an abnormality of the digital control unit is detected after the switching element has started to operate, there is a risk of damaging the switching power supply device or its load device before the abnormality is detected.
Japanese Patent Laid-Open No. 2000-14144 (pages 2, 7 and 1) JP 2003-264980 A (2nd, 4th page, FIG. 1)

  Therefore, in view of the above points, in the power supply circuit that performs step-up or step-down by the switching operation of the switching element or generates an AC voltage, the present invention can detect an abnormality of the digital control unit before the switching element starts operating. By detecting, it aims at preventing damaging a power supply circuit and the apparatus used as the load.

  In order to solve the above-described problem, a power supply circuit according to one aspect of the present invention includes at least one switching element that performs a switching operation when a drive signal is applied, and at least one that generates a drive signal based on the control signal. A power block that includes a driving circuit and performs step-up or step-down operation or generates an alternating voltage by a switching operation of at least one switching element; and at least one that outputs a detection signal by detecting a voltage or current at a predetermined location of the power block Two detection circuits, a control block for generating a control signal to be supplied to at least one drive circuit by performing digital signal processing based on a detection signal output from the at least one detection circuit, and after power-on, Based on the change in the potential of the control signal, the control block works well Determines whether Luke, after determining that the control block is operating satisfactorily, comprising a diagnostic circuit to ensure that the drive signal is applied to the switching element.

  According to the present invention, a power supply circuit and its load are provided by providing a diagnostic circuit that applies a drive signal to the switching element after determining that the control block is operating well after power-on. It is possible to prevent the apparatus from being damaged.

The best mode for carrying out the present invention will be described below in detail with reference to the drawings. In addition, the same reference number is attached | subjected to the same component and description is abbreviate | omitted.
FIG. 1 is a diagram showing a configuration of a power supply circuit according to the first embodiment of the present invention. In the first embodiment, a switching power supply circuit using a transformer will be described as an example. This switching power supply circuit boosts the AC voltage applied to the primary winding 21 and the rectifying and smoothing circuit 10 that generates a DC voltage by rectifying and smoothing the AC power supply voltage supplied to the input terminals 1 and 2. Alternatively, the switching element 30 is connected in series to the transformer 20 that steps down and outputs from the secondary winding 22 and the primary winding 21 of the transformer, and flows current to the primary winding 21 in accordance with a pulsed drive signal. And a drive circuit 40 that generates a drive signal for driving the switching element 30 and a primary-side current detection circuit 50 that detects a current flowing in the primary winding 21 of the transformer.

  Further, this switching power supply circuit includes a rectifying / smoothing circuit 60 including a diode 61 for half-wave rectifying the voltage generated in the secondary winding 22 of the transformer and a capacitor 62 for smoothing the rectified voltage, and a smoothing voltage at both ends of the capacitor 62. Based on the detection results of the various detection circuits, the secondary voltage detection circuit 70 for detecting current, the secondary current detection circuit 80 for detecting the current output from the rectifying and smoothing circuit 60 via the output terminals 3 and 4 A control block 90 that generates a control signal for controlling the switching element 30, a diagnostic circuit 100 for diagnosing an operation at the time of activation of the control block 90, and isolators 111 and 112 are included.

  The rectifying / smoothing circuit 10 includes, for example, a diode bridge and a capacitor. The AC voltage applied between the input terminal 1 and the input terminal 2 is full-wave rectified by the diode bridge and smoothed by the capacitor.

  The transformer 20 includes a magnetic core 23, a primary side winding 21 wound around the core 23, a secondary side winding 22, and two auxiliary windings (not shown). . Assuming that the number of turns of the primary winding 21 is N1 and the number of turns of the secondary winding 22 is N2, when there is no loss, the step-up ratio between the primary side and the secondary side is N2 / N1. A dot symbol attached to the transformer 20 indicates the polarity of the winding. The two auxiliary windings are used to supply a power supply voltage to the primary side circuit and the secondary side circuit.

  Generally, in a switching power supply, as a power transmission method from the primary side to the secondary side of the transformer, a forward method in which power is transmitted from the primary side to the secondary side when the switching element is turned on, and the switching element is turned off. Sometimes there is a flyback system that transmits power from the primary side to the secondary side. In the present embodiment, a flyback system that can extract a large number of high-voltage outputs on the secondary side is employed.

  In the flyback type switching power supply as shown in FIG. 1, the primary side winding 21 and the secondary side winding 22 of the transformer have a reverse polarity relationship, and the switching element 30 is on. Although the primary side current of the transformer 20 increases, the secondary side current does not flow because the secondary side of the transformer 20 is reverse-biased by a diode. The transformer 20 stores energy in the core 23 when the switching element 30 is on.

  Next, when the switching element 30 is turned off, the magnetic field tries to maintain current, so that the voltage polarity of the transformer 20 is reversed, and current flows on the secondary side of the transformer 20. The secondary current of the transformer 20 is charged to the capacitor 62 via the diode 61 connected in series to the secondary winding 22 of the transformer, so that a DC output voltage is generated between the output terminal 3 and the output terminal 4. Is generated. As the switching element 30, for example, a MOSFET (metal oxide semiconductor-field effect transistor) is used.

  An internal power supply voltage obtained by rectifying and smoothing an AC voltage generated by the two auxiliary windings of the transformer 20 is supplied to the primary side circuit and the secondary side circuit of the transformer 20, respectively. Since the output terminal 4 is connected to the ground potential (ground potential), the reference potential of the secondary side circuit is the ground potential, but the reference potential of the primary side circuit is isolated from the ground potential. In FIG. 1, a drive circuit 40, a primary current detection circuit 50, a control block 90, and a diagnostic circuit 100 correspond to the primary side circuit, and a secondary side voltage detection circuit 70 corresponds to the secondary side circuit. And the secondary side current detection circuit 80 corresponds.

  Therefore, the isolator 111 is connected between the secondary side voltage detection circuit 70 and the A / D converter 92, and the isolator 112 is connected between the secondary side current detection circuit 80 and the A / D converter 93. Is connected. As the isolators 111 and 112, for example, a photocoupler or the like having a transmission unit that converts an electrical signal into an optical signal and transmits it, and a reception unit that receives the optical signal transmitted by the transmission unit and converts it into an electrical signal The optical signal transmission element is used. When the secondary current detection circuit 80 is a detection circuit of a type that detects the output current in a non-contact manner in the current path, such as a current probe, a detection signal isolated from the ground potential is generated. Therefore, the isolator 112 can be omitted.

  The control block 90 includes A / D converters 91 to 93 and a DSP (digital signal processor) 94 in which the control functions of the switching power supply circuit are integrated. The A / D converter 91 converts the analog detection signal output from the primary-side current detection circuit 50 into a digital detection signal (detection data) and outputs it to the DSP 94. The A / D converter 92 converts the analog detection signal output from the isolator 111 into detection data and outputs the detection data to the DSP 94. The A / D converter 93 includes the isolator 112 or the secondary current detection circuit 80. The analog detection signal output from is converted to detection data and output to the DSP 94.

  The DSP 94 includes a nonvolatile memory such as an EEPROM in which software (control program) for causing the CPU to operate is stored, and a memory such as a DRAM and SRAM for temporarily storing various data. ing. The DSP 94 performs control of the switching element 30 by pulse modulation (PWM) by performing digital signal processing based on detection data output from at least one of the A / D converters 91 to 93. A signal (PWM signal) is generated. Note that the types and number of detection circuits and A / D converters can be changed as appropriate.

  For example, the DSP 94 may generate the control signal based only on the detection result of the secondary side voltage detection circuit 70. The DSP 94 may generate a control signal based on the detection result of the secondary side voltage detection circuit 70 and the detection result of the secondary side current detection circuit 80. In general, the output control in the conventional analog power supply circuit is performed based on the output voltage or the output current. However, by using digital signal processing, the output control is performed based on the output power. Control can also be performed.

  Alternatively, the DSP 94 may generate a control signal based on the detection result of the primary side current detection circuit 50 and the detection result of the secondary side voltage detection circuit 70. The DSP 94 generates a control signal based on the detection result of the primary side current detection circuit 50, the detection result of the secondary side voltage detection circuit 70, and the detection result of the secondary side current detection circuit 80. May be.

  Although it is necessary to keep the time required to generate the drive signal by performing the calculation for pulse modulation after taking the A / D converted detection data, in the control block 90 The switching element can be switched at a high frequency of about 10 kHz to 120 kHz by using a DSP whose operation processing speed is faster than that of a general-purpose microcomputer. For this purpose, the DSP 94 operates by receiving a clock signal having a frequency of about 40 MHz to 150 MHz.

  The diagnostic circuit 100 determines whether or not the DSP 94 of the control block 90 is operating satisfactorily after turning on the power, based on a change in the potential of the control signal, and after determining that the DSP 94 is operating properly. A drive signal is applied to the switching element 30.

  FIG. 2 is a diagram showing a first specific example of a diagnostic circuit in the switching power supply circuit of FIG. In this example, the diagnostic circuit 100 delays a counter 101 that counts the number of pulses included in a control signal generated by the DSP 94 and a system reset signal that is activated for a certain period when the power is turned on for a predetermined period. And determining whether the number of pulses counted by the counter 101 in a predetermined period after power-on is within a predetermined range, and determining that the number of pulses is within the predetermined range Sometimes, a determination circuit 103 that activates an enable signal for applying a drive signal to the switching element 30 and an AND circuit 104 that calculates a logical product of the control signal and the output signal of the determination circuit 103 are included. It is out.

  Since the system reset signal is supplied to the reset terminal of the counter 101, the counter 101 is reset when the power is turned on. Thereafter, the counter 101 increments the count value in synchronization with the rising edge of the pulse included in the control signal generated by the DSP 94. The count value output from the counter 101 is input to the determination circuit 103.

  The determination circuit 103 latches the count value output from the counter 101 in synchronization with the rising edge of the system reset signal delayed by the delay circuit 102. Further, the determination circuit 103 determines whether or not the latched count value is within a predetermined range, and activates the enable signal when it is determined that the latched count value is within the predetermined range. . Here, the predetermined range may have only a lower limit value, or may have a lower limit value and an upper limit value.

  The AND circuit 104 gates the control signal by obtaining a logical product of the control signal generated by the DSP 94 and the enable signal output from the determination circuit 103, and sends the gated control signal to the drive circuit 40 (FIG. 1). Supply. In this way, when the control signal generated by the DSP 94 is fixed at the high level, it is determined that the latched count value is outside the predetermined range, and the control signal becomes the low level. Thus, the drive signal is also at a low level, and the switching element 30 is not turned on.

FIG. 3 is a diagram showing a second specific example of the diagnostic circuit in the switching power supply circuit of FIG. In this example, the diagnostic circuit 100 has a low-pass filter (LPF) 105 that extracts a low-frequency component of the control signal, and a comparator that compares the potential of the signal output from the low-pass filter 105 with the first reference potential V _REF 1. 106, a comparator 107 that compares the potential of the signal output from the low-pass filter 105 with the second reference potential V _REF 2, and an AND circuit 108 that calculates a logical product of the output signal of the comparator 106 and the output signal of the comparator 107 A delay circuit 102 that delays a system reset signal that is activated for a predetermined period when the power is turned on for a predetermined period, a D flip-flop 109 that latches an output signal of the AND circuit 108 at a predetermined timing after the power is turned on, and a control signal And the output signal of D flip-flop 109 And an AND circuit 104.

The comparator 106 activates the output signal to a high level when the potential of the signal output from the low-pass filter 105 is smaller than the first reference potential V _REF 1, and the comparator 107 outputs the signal output from the low-pass filter 105. When the potential is higher than the second reference potential V _REF 2, the output signal is activated to a high level. Therefore, if the potential V _{LPF of the} signal output from the low-pass filter 105 is within a predetermined range (V _REF 2 <V _LPF <V _REF 1), the AND circuit 108 outputs a high level signal.

  The output signal of the AND circuit 108 is input to the data input terminal D of the flip-flop 109, the system reset signal delayed by the delay circuit 102 is input to the clock signal input terminal C, and the system signal is input to the reset terminal R. A reset signal is supplied. The D flip-flop 109 is reset when the power is turned on, and then latches the output signal of the AND circuit 108 in synchronization with the rising edge of the system reset signal delayed by the delay circuit 102 and outputs it as an enable signal.

  Therefore, the determination circuit configured by the comparator 106 to the D flip-flop 109 determines whether or not the potential of the signal output from the low-pass filter 105 is within a predetermined range at a predetermined timing after power-on. When it is determined that the potential of the signal is within a predetermined range, an enable signal for activating the drive signal to the switching element 30 is activated.

  The AND circuit 104 gates the control signal by obtaining a logical product of the control signal generated by the DSP 94 and the enable signal output from the D flip-flop 109, and the gated control signal is driven to the drive circuit 40 (FIG. 1). To supply. In this way, when the control signal generated by the DSP 94 is fixed at a high level, it is determined that the potential of the signal output from the low-pass filter 105 is outside the predetermined range, and the control signal Becomes low level and the drive signal also becomes low level, and the switching element 30 is not turned on.

  Alternatively, in FIG. 2 and FIG. 3, the diagnostic circuit 100 may output the input control signal as it is and supply the enable signal to the drive circuit 40 (FIG. 1). In that case, the drive circuit 40 supplies the drive signal to the switching element 30 when the enable signal is activated, and fixes the drive signal at a low level when the enable signal is deactivated. An example of such a drive circuit 40 is shown in FIG.

  The drive circuit 40 shown in FIG. 4 includes a level shifter 41 that shifts the level of a supplied control signal, two inversion circuits (inverters) 42 and 43 that buffer the output signal of the level shifter 41, and these inversion circuits 42 and 43. And a switch circuit 44 connected to the power supply line.

The level shifter 41 is supplied with power supply potentials V _DD and V _SS and a high power supply potential V _H used for driving the switching element 30. The level shifter 41 converts the voltage range of the control signal from the range of the power supply voltage (V _DD −V _SS ) to the range of the power supply voltage (V _H −V _SS ). Here, for example, the power supply voltage (V _DD −V _SS ) is 5V, and the power supply voltage (V _H −V _SS ) is 15V.

The inverting circuits 42 and 43 operate by being supplied with the power supply potentials V _H and V _SS . Here, the switch circuit 44 turns on / off the supply of power supply potential V _H accordance with the enable signal. For example, the switch circuit 44 includes a P-channel transistor connected between the power supply potential _VH and the power supply lines of the inverting circuits 42 and 43, and an N-channel transistor that controls the gate potential of the P-channel transistor. . The drain of the N-channel transistor is connected to the gate of the P-channel transistor, the source is connected to the power supply potential _VSS , and an enable signal is supplied to the gate.

When the enable signal is inactivated to the low level, the switch circuit 44 is turned off and the power supply potential _VH is not supplied to the inverting circuits 42 and 43, so that the drive signal output from the inverting circuit 43 is at the low level. . Therefore, the switching element 30 maintains the off state. When the enable signal is activated to a high level, the switch circuit 44 is turned on and the power supply potential _VH is supplied to the inverting circuits 42 and 43, so that a pulsed drive signal is generated from the inverting circuit 43 based on the control signal. Is output. The switching element 30 shown in FIG. 1 performs a switching operation when a drive signal is applied from the drive circuit 40.

Next, a second embodiment of the present invention will be described.
FIG. 5 is a diagram showing a configuration of a power supply circuit according to the second embodiment of the present invention. In the second embodiment, a chopper boost type switching power supply circuit using a choke coil will be described as an example.

  This switching power supply circuit includes a rectifying / smoothing circuit 10 connected to AC voltage input terminals 1 and 2, and a choke coil having one end connected to the rectifying / smoothing circuit 10 and storing magnetic energy generated by a current flowing in the winding in a core. 120, a switching element 30 that is connected to the other end of the choke coil 120 and passes a current through the choke coil 120 according to a pulsed drive signal, and a switching current detection circuit 130 that detects a current flowing through the switching element 30 Yes. Here, when the primary winding of the transformer is used as the choke coil 120, the secondary winding of the transformer can be used for generating an internal power source.

  Further, this switching power supply circuit detects a smoothing voltage at both ends of the capacitor 62 and a rectifying / smoothing circuit 60 including a diode 61 for half-wave rectifying the voltage generated at the other end of the choke coil 120 and a capacitor 62 for smoothing the rectified voltage. The output voltage detection circuit 140 for detecting the current output from the rectifying / smoothing circuit 60 via the output terminals 3 and 4, and the switching element 30 based on the detection results of the various detection circuits. A control block 90 that generates a control signal to perform, and a diagnostic circuit 100 for diagnosing the operation of the control block 90 when it is started up are included.

  The choke coil 120 stores energy in the core when the switching element 30 is on. Next, when the switching element 30 is turned off, the magnetic field tries to maintain the current, so that the current of the choke coil 120 flows to the capacitor 62 via the diode 61, and the capacitor 62 is charged. A DC output voltage is generated between the terminals 4.

  The A / D converter 91 converts the analog detection signal output from the switching current detection circuit 130 into a digital detection signal (detection data) and outputs the digital detection signal to the DSP 94. The A / D converter 92 converts the analog detection signal output from the output voltage detection circuit 140 into detection data and outputs it to the DSP 94, and the A / D converter 93 outputs from the output current detection circuit 150. The analog detection signal is converted into detection data and output to the DSP 94.

  The DSP 94 performs control of the switching element 30 by pulse modulation (PWM) by performing digital signal processing based on detection data output from at least one of the A / D converters 91 to 93. A signal (PWM signal) is generated. Note that the types and number of detection circuits and A / D converters can be changed as appropriate.

  For example, the DSP 94 may generate the control signal based only on the detection result of the output voltage detection circuit 140. The DSP 94 may generate a control signal based on the detection result of the output voltage detection circuit 140 and the detection result of the output current detection circuit 150.

  Alternatively, the DSP 94 may generate a control signal based on the detection result of the switching current detection circuit 130 and the detection result of the output voltage detection circuit 140. The DSP 94 may generate a control signal based on the detection result of the switching current detection circuit 130, the detection result of the output voltage detection circuit 140, and the detection result of the output current detection circuit 150.

  The diagnostic circuit 100 determines whether or not the DSP 94 of the control block 90 is operating satisfactorily after turning on the power, based on a change in the potential of the control signal, and after determining that the DSP 94 is operating properly. A drive signal is applied to the switching element 30.

Next, a third embodiment of the present invention will be described.
FIG. 6 is a diagram showing a configuration of a power supply circuit according to the third embodiment of the present invention. In the third embodiment, a motor / inverter that generates a three-phase AC voltage for driving a motor using a DC voltage obtained by rectifying and smoothing an AC voltage will be described as an example.

  This motor / inverter is connected to an input filter 11 for cutting a noise component contained in an input AC voltage (AV100V), a rectifier circuit 12 for rectifying the AC voltage, and one end connected to the rectifier circuit 12. A choke coil 120 that stores magnetic energy generated by the current flowing through the windings in the core, a switching element 30 that allows current to flow through the choke coil 120 in accordance with a pulsed drive signal, and a voltage that is generated at the other end of the choke coil 120 is a half-wave. A rectifying / smoothing circuit 60 including a diode 61 for rectification and a capacitor 62 for smoothing the rectified voltage is provided. These constitute a PFC (power factor controller) circuit that improves the power factor by matching the waveform and phase of the voltage and current when the input voltage is converted to a DC voltage.

  Further, the motor / inverter includes a switching current detection circuit 130 that detects a current flowing through the switching element 30, a DC voltage detection circuit 160 that detects a DC voltage output from the PFC circuit, and an output terminal 3 from the rectifying / smoothing circuit 60. 4 and 4, a DC current detection circuit 170 that detects a DC current output via 4, an inverter 180 that outputs a three-phase AC voltage by performing a switching operation based on the DC voltage output from the PFC circuit, and various detections A control block 90 that generates a plurality of control signals for controlling the switching element 30 and the inverter 180 based on the detection result of the circuit, and diagnosis circuits 100 and 100a for diagnosing the operation of the control block 90 when starting up. 100f. The configurations of the diagnostic circuits 100a to 100f are the same as the configuration of the diagnostic circuit 100.

  FIG. 7 is a diagram illustrating a principle configuration example of the inverter in FIG. 6. As shown in FIG. 7, the inverter 180 includes switching elements Q21 and Q22 such as IGBT (Insulated Gate Bipolar Transistor) connected to the U-phase output terminal, and switching elements Q23 and Q24 connected to the V-phase output terminal. Switching elements Q25 and Q26 connected to the W-phase output terminal, diodes D21 to D26 connected in parallel to the switching elements Q21 to Q26, respectively, and switching elements Q21 to Q26 based on a plurality of control signals Drive circuits 40a to 40f for driving each of these. The configuration of the drive circuits 40 a to 40 f is the same as the configuration of the drive circuit 40. The switching elements Q21 to Q26 perform a switching operation between the DC voltage output from the PFC circuit and the U-phase to W-phase output terminals according to the drive signals output from the drive circuits 40a to 40f. Outputs AC voltage.

  Referring to FIG. 6 again, the A / D converter 91 converts the analog detection signal output from the switching current detection circuit 130 into a digital detection signal (detection data) and outputs the digital detection signal to the DSP 94. The A / D converter 92 converts the analog detection signal output from the DC voltage detection circuit 160 into detection data and outputs it to the DSP 94, and the A / D converter 93 outputs from the DC current detection circuit 170. The analog detection signal is converted into detection data and output to the DSP 94.

  The DSP 94 performs control of the switching element 30 by pulse modulation (PWM) by performing digital signal processing based on detection data output from at least one of the A / D converters 91 to 93. A plurality of control signals for controlling the inverter 180 are generated by generating a signal (PWM signal) and performing digital signal processing based on detection data output from the A / D converter 93. Note that the types and number of detection circuits and A / D converters can be changed as appropriate.

  For example, the DSP 94 may generate a control signal for controlling the switching element 30 based only on the detection result of the DC voltage detection circuit 160. The DSP 94 may generate a control signal for controlling the switching element 30 based on the detection result of the DC voltage detection circuit 160 and the detection result of the DC current detection circuit 170.

  Alternatively, the DSP 94 may generate a control signal for controlling the switching element 30 based on the detection result of the switching current detection circuit 130 and the detection result of the DC voltage detection circuit 160. The DSP 94 generates a control signal for controlling the switching element 30 based on the detection result of the switching current detection circuit 130, the detection result of the DC voltage detection circuit 160, and the detection result of the DC current detection circuit 170. You may do it.

  At the same time, the DSP 94 generates a plurality of control signals for controlling the plurality of switching elements in the inverter 180 based on the input current of the inverter 180 represented by the detection signal output from the DC current detection circuit 170.

  The diagnostic circuits 100 and 100a to 100f determine whether or not the DSP 94 of the control block 90 is operating properly based on the change in potential of each control signal after the power is turned on. After determining that the drive signals are present, the drive signals are applied to the switching elements 30 and the plurality of switching elements in the inverter 180.

  The present invention can be used in a power supply circuit used in an electronic device.

It is a figure which shows the structure of the power supply circuit which concerns on the 1st Embodiment of this invention. FIG. 2 is a diagram illustrating a first specific example of a diagnostic circuit in the switching power supply circuit of FIG. 1. FIG. 4 is a diagram showing a second specific example of a diagnostic circuit in the switching power supply circuit of FIG. 1. It is a figure which shows the specific example of the drive circuit in the switching power supply circuit of FIG. It is a figure which shows the structure of the power supply circuit which concerns on the 2nd Embodiment of this invention. It is a figure which shows the structure of the power supply circuit which concerns on the 3rd Embodiment of this invention. It is a figure which shows the example of a fundamental structure of the inverter in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 Input terminal 3, 4 Output terminal 10 Rectifier smoothing circuit 11 Input filter 12 Rectifier circuit 20 Transformer 21 Primary side winding 22 Secondary side winding 23 Core 30 Switching element 40, 40a-40f Drive circuit 41 Level shifter 42, DESCRIPTION OF SYMBOLS 43 Inversion circuit 44 Switch circuit 50 Primary side current detection circuit 60 Rectification smoothing circuit 61 Diode 62 Capacitor 70 Secondary side voltage detection circuit 80 Secondary side current detection circuit 90 Control block 91-93 A / D converter 94 DSP
100, 100a to 100f Diagnostic circuit 101 Counter 102 Delay circuit 103 Judgment circuit 104 AND circuit 105 LPF
106, 107 Comparator 108 AND circuit 109 D flip-flop 111, 112 Isolator 120 Choke coil 130 Switching current detection circuit 140 Output voltage detection circuit 150 Output current detection circuit 160 DC voltage detection circuit 170 DC current detection circuit 180 Inverter

Claims (11)

Including at least one switching element that performs a switching operation when a driving signal is applied, and at least one driving circuit that generates a driving signal based on a control signal, and performs step-up or step-down by the switching operation of the at least one switching element. A power block that performs or generates an alternating voltage; and
At least one detection circuit for detecting a voltage or current at a predetermined location of the power block and outputting a detection signal;
A control block for generating a control signal to be supplied to the at least one drive circuit by performing digital signal processing based on a detection signal output from the at least one detection circuit;
After the power is turned on, based on the change in the potential of the control signal, it is determined whether or not the control block is operating properly. After determining that the control block is operating well, the switching element is driven. A diagnostic circuit that allows a signal to be applied;
A power supply circuit comprising: The diagnostic circuit comprises:
A counter that counts the number of pulses included in the control signal generated by the control block;
It is determined whether or not the number of pulses counted by the counter in a predetermined period after power-on is within a predetermined range, and when it is determined that the number of pulses is within the predetermined range, the switching A determination circuit for activating an enable signal for applying a drive signal to the element;
The power supply circuit according to claim 1, comprising: The diagnostic circuit comprises:
A low pass filter for extracting a low frequency component of a control signal generated by the control block;
It is determined whether or not the potential of the signal output from the low-pass filter is within a predetermined range at a predetermined timing after turning on the power, and when it is determined that the potential of the signal is within the predetermined range, A determination circuit that activates an enable signal for applying a drive signal to the switching element;
The power supply circuit according to claim 1, comprising:   The diagnostic circuit gates a control signal by obtaining a logical product of a control signal generated by the control block and an enable signal output from the determination circuit, and supplies the gated control signal to the drive circuit. The power supply circuit according to claim 2, further comprising a logic circuit. The drive circuit is
A drive signal generation circuit for generating a drive signal based on a control signal supplied from the control block;
A switch circuit for switching whether to supply a power supply voltage to at least a part of the drive signal generation circuit according to an enable signal output from the determination circuit;
The power supply circuit according to claim 2, comprising: The power block is
A transformer having a core and a primary winding and a secondary winding wound around the core;
A switching element connected in series to the primary winding of the transformer, and for passing a current through the primary winding of the transformer according to a drive signal;
A primary current detection circuit for detecting a current flowing in the primary winding of the transformer;
A rectifying / smoothing circuit that generates an output voltage by rectifying and smoothing a voltage generated in the secondary winding of the transformer;
A secondary side voltage detection circuit for detecting an output voltage generated by the rectifying and smoothing circuit;
The power supply circuit according to claim 1, comprising: The control block is
A first A / D converter for A / D converting a detection signal output from the primary side current detection circuit and outputting detection data;
A second A / D converter for A / D converting a detection signal output from the secondary side voltage detection circuit and outputting detection data;
A digital signal processor that generates a control signal by performing pulse modulation based on at least detection data output from the first and second A / D converters;
The power supply circuit according to claim 6, comprising: The power block is
A choke coil having a winding to which a DC voltage is applied at one end;
A switching element connected to the other end of the choke coil winding and for passing a current through the choke coil according to a drive signal;
A switching current detection circuit for detecting a current flowing through the switching element;
A rectifying and smoothing circuit that generates an output voltage by rectifying and smoothing a voltage generated at the other end of the choke coil;
An output voltage detection circuit for detecting an output voltage generated by the rectifying and smoothing circuit;
The power supply circuit according to claim 1, comprising: The control block is
A first A / D converter for A / D converting a detection signal output from the switching current detection circuit and outputting detection data;
A second A / D converter for A / D converting a detection signal output from the output voltage detection circuit and outputting detection data;
A digital signal processor that generates a control signal by performing pulse modulation based on at least detection data output from the first and second A / D converters;
The power supply circuit according to claim 8, comprising: The power block is
A choke coil having a winding to which a rectified voltage is applied at one end;
A switching element connected to the other end of the choke coil winding and for passing a current through the choke coil according to a drive signal;
A switching current detection circuit for detecting a current flowing through the switching element;
A rectifying and smoothing circuit that generates a DC voltage by rectifying and smoothing a voltage generated at the other end of the choke coil;
A DC voltage detection circuit for detecting a DC voltage generated by the rectifying and smoothing circuit;
An inverter including a plurality of switching elements that are supplied with a DC voltage generated by the rectifying and smoothing circuit and generate an AC voltage according to a plurality of drive signals;
A direct current detection circuit for detecting a direct current supplied from the rectifying and smoothing circuit to the inverter;
The power supply circuit according to claim 1, comprising: The control block is
A first A / D converter for A / D converting a detection signal output from the switching current detection circuit and outputting detection data;
A second A / D converter for A / D converting a detection signal output from the DC voltage detection circuit and outputting detection data;
A third A / D converter for A / D converting a detection signal output from the DC current detection circuit and outputting detection data;
A digital signal processor that generates a plurality of control signals based on detection data output from the first to third A / D converters;
The power supply circuit according to claim 10, comprising:

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