Input voltage determination circuit, switching power supply device, and semiconductor device

Abstract

The invention relates to an input voltage determination circuit, a switching power supply device, and a semiconductor device. Provided is an input voltage determination circuit capable of determining whether an AC input voltage is a low-voltage system or a high-voltage system using an initial ON pulse width without using the AC input voltage as a determination voltage. An input voltage determination circuit (17) that determines whether an AC input voltage to be supplied to a flyback switching power supply device that controls the ON pulse width (TON) of a switching element (Q1) in a current mode on the basis of a feedback signal (VFB) is a low-voltage system or a high-voltage system. And an input voltage determination circuit (17) that determines that the input voltage system is a high-voltage system when the first conduction pulse width (TON) is less than a predetermined determination period, and that determines that the input voltage system is a low-voltage system when the first conduction pulse width (TON) is equal to or greater than the determination period.

Description

Technical Field

[0001] The present invention relates to an input voltage determination circuit for determining an input voltage. Background Art

[0002] The voltage of commercial AC power varies depending on the country, and is roughly divided into 100V to 120V AC100V system (low voltage system) and 200V to 260V AC200V system (high voltage system). It is hoped that the switching power supply device can operate with high efficiency under any of these AC input voltages. Therefore, the following technology is proposed: in the switching power supply device, it is determined whether the AC input voltage is a low voltage system or a high voltage system, and the low-frequency gain characteristics are switched according to the determination result (for example, refer to Patent Document 1).

[0003] Patent Document 1: Japanese Patent Application Publication No. 2013-62930

[0004] However, the prior art uses the pulsating voltage after half-wave rectification of the AC input voltage as a judgment voltage to judge whether the AC input voltage is a low voltage system or a high voltage system. Therefore, the control circuit needs to have an input voltage judgment terminal for inputting the judgment voltage. In addition, the components of the circuit for judging the AC input voltage are generally composed of low-voltage components, so a voltage divider circuit (input detection resistor) for generating the judgment voltage is also required. Summary of the invention

[0005] The present invention has been made in view of such a problem, and an object of the present invention is to provide an input voltage determination circuit capable of determining whether an AC input voltage is a low voltage system or a high voltage system without using the AC input voltage as a determination voltage.

[0006] In order to achieve the above-mentioned object, the input voltage determination circuit and the switching power supply device of the present invention are constructed as follows.

[0007] The input voltage determination circuit of the present invention determines whether the AC input voltage supplied to the flyback switching power supply device is a low voltage system or a high voltage system. The flyback switching power supply device controls the on-pulse width of the switching element according to the feedback signal in the current mode. The input voltage determination circuit is characterized in that when the initial on-pulse width is less than a predetermined determination period, the input voltage determination circuit determines that it is the high voltage system, and when the initial on-pulse width is greater than the determination period, the input voltage determination circuit determines that it is the low voltage system.

[0008] In addition, the switching power supply device of the present invention is a flyback switching power supply device that controls the on-pulse width of the switching element according to a feedback signal in the current mode, and is characterized in that the switching power supply device has an input voltage judgment circuit. When the initial on-pulse width is less than a predetermined judgment period, the input voltage judgment circuit judges that the AC input voltage is a high voltage system, and when the initial on-pulse width is greater than the judgment period, the input voltage judgment circuit judges that the AC input voltage is a low voltage system.

[0009] The input voltage determination circuit of the present invention can determine whether the AC input voltage is a low voltage system or a high voltage system by using the initial on pulse width without using the AC input voltage as a determination voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a diagram showing a configuration example of a switching power supply device according to the present invention.

[0011] Figure 2 It is shown Figure 1 A diagram showing an example of the configuration of the controller 1 is shown.

[0012] Figure 3 It is shown Figure 2 The waveform diagram of the determination operation of the input voltage determination circuit shown.

[0013] Figure 4 It is shown based on Figure 2 Graph showing changes in gain characteristics caused by switching operation of the filter circuit shown.

[0014] Description of symbols

[0015] 1: controller; 10: control power supply circuit; 11: drive circuit; 12: OVP (overvoltage protection circuit); 13: OSC (internal oscillator); 14: OCP (overcurrent detection circuit); 15: filter circuit; 16: feedback circuit; 17: input voltage determination circuit. DETAILED DESCRIPTION

[0016] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

[0017] The switching power supply device of this embodiment is a flyback type. Figure 1 , having a rectifier circuit DB, smoothing capacitors C1, C2, C3, a transformer T, a controller 1, rectifier diodes D1, D2, an error amplifier (E / A) 2, a light emitting diode PC1 and a light receiving transistor PC2 constituting a photocoupler, and a current detection resistor R ID , resistors R1, R2.

[0018] A commercial AC power source AC is connected to the AC input terminals ACin1 and ACin2 of a rectifier circuit DB formed by a diode bridge. The rectifier circuit DB performs full-wave rectification on the input AC voltage from the commercial AC power source AC and outputs it. The rectifier circuit DB has a rectifier output positive terminal and a rectifier output negative terminal. The smoothing capacitor C1 is connected between the rectifier output positive terminal and the rectifier output negative terminal. The rectifier output negative terminal of the rectifier circuit DB is connected to the ground terminal. Thus, the commercial AC power source AC is rectified and smoothed by the rectifier circuit DB and the smoothing capacitor C1 to obtain a DC power source.

[0019] The controller 1 has built-in switching elements such as power MOSFET (Metal Oxide Semiconductor Field Effect Transistor) and a control circuit for switching the switching elements. The controller 1 has a D terminal, an S terminal, a Vcc terminal, an FB terminal, and a GND terminal connected to a common potential.

[0020] The transformer T that supplies power from the primary side (input side) to the secondary side (load side) is composed of a primary winding Np, an auxiliary winding Nd, and a secondary winding Ns. The positive terminal of the rectifier output of the rectifier circuit DB is connected to one end of the primary winding Np of the transformer T, and the other end of the primary winding Np is connected to the D terminal of the controller 1. The S terminal of the controller 1 is connected to the current detection resistor R ID The switch element built into the controller 1 is connected between the D terminal and the S terminal. Thus, by controlling the on / off of the switch element, the power supplied to the primary winding P of the transformer T is transmitted to the secondary winding Ns of the transformer T, and a pulsating current is generated in the secondary winding Ns of the transformer T.

[0021] Current detection resistor R ID This is to detect the current ID flowing through the switch element Q1 built into the controller 1 as a current detection signal V ID The controller 1 detects the current according to the current detection signal V ID , operating in current mode.

[0022] A smoothing capacitor C2 is connected between two terminals of the secondary winding Ns of the transformer T via a rectifying diode D1. The voltage induced in the secondary winding Ns of the transformer T is rectified and smoothed by the rectifying diode D1 and the smoothing capacitor C2, and the voltage between the terminals of the smoothing capacitor C2 is output from the output terminal as an output voltage Vo. In addition, the line connected to the positive terminal of the smoothing capacitor C2 becomes a power line, and the line connected to the negative terminal of the smoothing capacitor C2 becomes a GND line connected to the ground terminal.

[0023] An error amplifier 2 is connected in series between the power line and the GND line. The error amplifier 2 is connected between the power line and the GND line, and controls the current flowing through the light emitting diode PC1 of the photocoupler according to the difference between the output voltage Vo and the steady-state voltage. In addition, the FB / OLP terminal of the controller 1 is connected to the ground terminal via the light emitting diode PC1 and the capacitor C4 connected in parallel. As a result, a feedback (FB) signal corresponding to the output voltage Vo is sent from the light emitting diode PC1 on the secondary side to the light receiving transistor PC2 on the primary side as a signal notifying the load state, and is used as a feedback signal V FB Input to the FB / OLP terminal of controller 1. Controller 1 responds to the feedback signal V input to the FB terminal. FB , controls the conduction pulse width (duty cycle) of the switching element and controls the amount of power supplied to the secondary side.

[0024] Furthermore, a smoothing capacitor C3 is connected between two terminals of the auxiliary winding Nd of the transformer T via a rectifying diode D2, and a connection point between the rectifying diode D2 and the smoothing capacitor C3 is connected to the Vcc terminal of the controller 1. Thus, the voltage generated in the auxiliary winding Nd is rectified and smoothed by the rectifying diode D2 and the smoothing capacitor C3, and is supplied to the Vcc terminal of the controller 1 as an IC power supply voltage Vcc.

[0025] Next, refer to Figure 2 ,right Figure 1 The circuit structure of the controller 1 shown will be described.

[0026] The controller 1 can be configured as a semiconductor device such as an IC formed by encapsulating a semiconductor integrated circuit in a package made of resin. Figure 2 The controller 1 has a switching element Q1 composed of an N-channel power MOSFET, a control power supply circuit 10, a drive circuit 11, an OVP (overvoltage protection circuit) 12, an OSC (internal oscillator) 13, an OCP (overcurrent detection circuit) 14, a filter circuit 15, a feedback circuit 16, an input voltage determination circuit 17, OR circuits OR1, OR2, OR3 and a trigger FF1.

[0027] The drain terminal of the switch element Q1 is connected to the D terminal, the source terminal is connected to the S terminal, and the gate terminal is connected to the output terminal of the drive circuit 11. The drive circuit 11 outputs a drive signal V gs , controlling the on / off of the switching element Q1.

[0028] The control power supply circuit 10 has a comparator COMP1 and a regulator 101. The comparator COMP1 is a comparison circuit that compares the IC power supply voltage Vcc at the Vcc terminal with the variable voltage VR1. The non-inverting input terminal of the comparator COMP1 is connected to the Vcc terminal, and the inverting input terminal is connected to the variable voltage VR1. The output signal from the comparator COMP1 is input to the variable voltage VR1. When the output signal from the comparator COMP1 is at a Low level, the variable voltage VR1 is set to a first reference voltage Von (for example, 15V). When the output signal from the comparator COMP1 is at a Hi level, the variable voltage VR1 is set to a second reference voltage Voff (for example, 10V) lower than the first reference voltage Von. As a result, the output signal of the comparator COMP1 has a hysteresis characteristic, which is controlled by a startup circuit (not shown). Figure 1 The smoothing capacitor C3 shown is charged and becomes a Hi level when the IC power supply voltage Vcc exceeds the first reference voltage Von, and becomes a Low level when the IC power supply voltage Vcc is equal to or lower than the second reference voltage Voff.

[0029] In addition, the output terminal of the comparator COMP1 is connected to the regulator 101. The regulator 101 receives power supply from the Vcc terminal, and operates when the output signal of the comparator COMP1 is at the Hi level, and supplies power supply voltage (regulator voltage V Reg In other words, the output signal of the comparator COMP1 is a signal for controlling the on / off of the controller 1. When the controller 1 is in stable operation (when the switch operation is turned on), the output signal of the comparator COMP1 becomes a Hi level. Therefore, the first reference voltage Von of the variable voltage VR1 is the operation start voltage of the controller 1, and the second reference voltage Voff of the variable voltage VR1 is the operation stop voltage of the controller 1.

[0030] The driving circuit 11 generates a driving signal V according to the inverted output of the OR circuit OR1. gs The output of the OR circuit OR2 is input to one input terminal of the OR circuit OR1, and the output of the OVP 12 is input to the other input terminal. When an overvoltage on the secondary side is detected from the IC power supply voltage Vcc at the Vcc terminal, the OVP 12 outputs a Hi level.

[0031] The output of OSC13 is input to one input terminal of the OR circuit OR2, and the inverting output terminal Q of the flip-flop FF1 is input to the other input terminal. -The output of the flip-flop FF1 is input to the set terminal S of the flip-flop FF1, and the output of the OR circuit OR3 is input to the reset terminal R. The OSC 13 outputs a clock signal, and the pulse width of the clock signal is set to be smaller than the minimum on-time width of the switch element Q1. The flip-flop FF1 functions as a PWM latch circuit. Thus, when the output signal of the OSC 13 is at a Low level (a state where the clock signal is not output) and the flip-flop FF1 is set, the inverted output terminal Q - When the output signal of is at a Low level, the output signal of a Hi level is input from the OR circuit OR1 to the drive circuit 11, and the switch element Q1 is turned on.

[0032] The feedback signal V of the FB terminal is input to OSC 13. FB The OSC 13 has the following frequency reduction function: it makes the feedback signal V FB The oscillation frequency (switching frequency) of the output clock signal is reduced at low or medium loads, thereby reducing the loss in the switching element Q1 and improving efficiency.

[0033] The current detection signal V input from the S terminal ID The current detection signal V is input to the OCP 14 and is input to the feedback circuit 16 via the filter circuit 15. The output of the OCP 14 is connected to one input terminal of the OR circuit OR3. ID Exceeds the preset OCP threshold V ocp When the overcurrent is detected, OCP 14 outputs Hi level. The output of OCP 14 is input to one input terminal of OR circuit OR3. Therefore, the output of OCP 14 changes to Hi level, thereby resetting flip-flop FF1 and turning off switch element Q1.

[0034] The feedback circuit 16 includes a constant current source CC1 and a comparator COMP1. The constant current source CC1 supplies a constant current to the FB terminal. The feedback signal V FB The comparator COMP1 is used to perform a feedback signal V according to the FB terminal. FB The current sensing converter of the feedback control controls the duty cycle of the switching element Q1. The comparator COMP1 responds to the feedback signal V FB The current detection signal V input to the inverting input terminal via the filter circuit 15 ID When the current detection signal V ID Exceeds the feedback signal V FB When , the output of comparator COMP1 changes to Low level.

[0035] The output of the comparator COMP1 is input to the other inverting input terminal of the OR circuit OR3. Therefore, the output of the comparator COMP1 changes to a Low level, thereby resetting the flip-flop FF1 and turning off the switch element Q1. Thus, the following feedback control is performed: in the current mode, the feedback signal V FB , controls the duty cycle of the switching element Q1.

[0036] The filter circuit 15 is an RC filter having resistors R3, R4, R5 and a capacitor C4. The resistors R3 and R4 are connected in series between the S terminal and the inverting input terminal of the comparator COMP1. The capacitor C4 is connected between the inverting input terminal of the comparator COMP1 and a common potential.

[0037] The filter circuit 15 includes a constant current source CC2 and switching elements Q2 and Q3. The switching element Q2 is composed of an N-channel power MOSFET or the like, and is connected in parallel with the resistor R3.

[0038] The switch element Q3 is composed of an N-channel power MOSFET and the like. The input voltage determination signal X from the input voltage determination circuit 17 is input to the gate of the switch element Q3 via a NOT circuit. The switch element Q3 is controlled to be turned on when the input voltage determination signal X is at a Low level, and is controlled to be turned off when the input voltage determination signal X is at a Hi level. The on / off is controlled by the input voltage determination signal X. The constant current source CC2 and the resistor R5 are connected in series at the regulator voltage V Reg The switching element Q3 and the resistor R5 are connected in parallel between the common potential and the switching element Q2. The connection point between the constant current source CC2 and the resistor R5 (switching element Q3) is connected to the gate of the switching element Q2.

[0039] The input voltage determination circuit 17 includes a switch SW1, a constant current source CC3, a capacitor C5, a latch circuit 171, and a comparator COMP2. The switch SW1, the constant current source CC3, and the capacitor C5 are connected in series between the drive circuit 11 and a common potential.

[0040] The switch SW1 is in the on state when it is started. The capacitor C5 is driven by the signal V gs The first on pulse (the first Hi level after startup) is charged by the constant current source CC3, and the charging potential V at the connection point between the constant current source CC3 and the capacitor C5 is C5 rise.

[0041] The non-inverting input terminal of the comparator COMP2 is connected to the connection point of the constant current source CC3 and the capacitor C5, and the input terminal is connected to the judgment threshold voltage V th The output of comparator COMP2 becomes the input voltage determination signal X. When the charging potential V C5 Exceeds the judgment threshold voltage Vth , becomes Hi level.

[0042] The latch circuit 171 detects the driving signal V gs When the voltage drops, the switch SW1 which is in the on state at the start-up is turned into the off state, and then maintained in the off state.

[0043] Figure 3 (a) shows the judgment operation of the input voltage judgment circuit 17 when the input AC voltage is 200V to 260V AC200V system (high voltage system). When the input AC voltage is connected and the input voltage Vin obtained by rectification and smoothing by the rectifier circuit DB and the smoothing capacitor C1 rises, the controller 1 starts and starts driving the signal V at time t1. gs The output (drive signal V gs is Hi level). The driving signal V gs becomes Hi level, thereby turning on the switch element Q1 and the current detection signal V ID The current detection signal V ID Exceeding the OCP threshold V ocp At time t2, the driving signal V gs In addition, at the time of startup, there is no output voltage Vo, so the OCP 14 detects an overcurrent and turns off the switching element Q1.

[0044] The switch SW1 is in the on state when it is started, so the capacitor C5 is gs The initial conduction pulse width T ON The period T 200 , charged with the constant current of constant current source CC3. Determine the threshold voltage V th It is set to be during the period T 200 The charging potential V C5 Therefore, the input voltage determination signal X, which is the output of the comparator COMP2, becomes a Low level. In other words, the constant current of the constant current source CC3 is used to charge the battery until the charging potential V C5 Reaching the judgment threshold voltage V th The period until is the determination period T th During the initial conduction pulse width T ON Less than the judgment period T th In this case, the input voltage determination circuit 17 determines that the input AC voltage is AC200V system (high voltage system).

[0045] Figure 3(b) shows the judgment operation of the input voltage judgment circuit 17 when the input AC voltage is 100V to 120V AC100V system (low voltage system). When the input AC voltage is connected and the input voltage Vin obtained by rectification and smoothing by the rectifier circuit DB and the smoothing capacitor C1 rises, the controller 1 starts and starts driving the signal V at time t1. gs The output (drive signal V gs is Hi level). The driving signal V gs becomes Hi level, thereby turning on the switch element Q1 and the current detection signal V ID The current detection signal V ID Exceeding the OCP threshold V ocp At time t3, the driving signal V gs In addition, at the time of startup, there is no output voltage Vo, so the OCP 14 detects an overcurrent and turns off the switching element Q1.

[0046] The switch SW1 is in the on state when it is started, so the capacitor C5 is gs The initial conduction pulse width T ON The period T 100 , the constant current source CC3 is used for charging. In the case of AC100V, the current detection signal V ID Therefore, during the period T from time t1 to t3, 100 The period T between time t1 and t2 200 Long. Judgment threshold voltage V th It is set to be during the period T 100 The charging potential V C5 Therefore, the input voltage determination signal X, which is the output of the comparator COMP2, becomes Hi level. In other words, at the initial on pulse width T ON The determination period T th In the above case, the input voltage determination circuit 17 determines that the input AC voltage is of the AC 100 V system (low voltage system).

[0047] That is, the input voltage determination circuit 17 determines the initial on pulse width T ON , determine whether the AC input voltage is a high voltage system or a low voltage system. When it is determined to be a high voltage system, a Low level input voltage determination signal X is output. When it is determined to be a low voltage system, a Hi level input voltage determination signal X is output.

[0048] When the input voltage determination signal X is at a Low level (AC200V), the switch element Q3 of the filter circuit 15 is turned on, the switch element Q2 is turned off, and the filter constant is set by the resistors R3, R4, and the capacitor C4. When the input voltage determination signal X is at a Hi level (AC100V), the switch element Q3 of the filter circuit 15 is turned off, the switch element Q2 is turned on, and the filter constant is set by the resistor R4 and the capacitor C4.

[0049] That is, regarding the filter constant of the filter circuit 15, the filter constant is switched to be larger in the case of the AC200V system than in the case of the AC100V system according to the determination result of the input voltage determination circuit 17. By switching the filter constant, the delay time of the filter circuit 15 is slower in the case of the AC200V system than in the case of the AC100V system. Therefore, in the case of the AC200V system, the current ID (current detection signal V ID ) is to increase, so as a result, the feedback signal V FB The oscillation frequency (switching frequency) of the clock signal output by OSC 13 is also affected by the feedback signal V FB Therefore, if Figure 4 As shown, the oscillation frequency characteristics in the case of the AC200V system are set slightly lower than those in the case of the AC100V system, and the starting point of the frequency reduction function is also switched.

[0050] As described above, the present embodiment is an input voltage determination circuit 17 that determines whether the AC input voltage supplied to the flyback switching power supply device is a low voltage system or a high voltage system. The flyback switching power supply device is in the current mode according to the feedback signal V FB , controls the conduction pulse width T of the switch element Q1 ON , where the initial conduction pulse width T ON If the pulse width is less than the preset judgment period, it is judged as a high voltage system, and the first conduction pulse width T ON If the period is longer than the above determination period, it is determined to be a low pressure system.

[0051] According to this configuration, it is possible to use the initial on pulse width T without using the AC input voltage as the determination voltage. ON , to determine whether the AC input voltage is a low voltage system or a high voltage system. Since there is no need to have an input voltage determination terminal or a voltage divider circuit (input detection resistor), it is possible to achieve low costs.

[0052] Furthermore, the switching power supply device of the present embodiment includes a feedback circuit 16 for generating a feedback signal V of the current detection signal V after passing through the filter circuit 15. IDand the feedback signal V FB By comparing the switching element Q1, the on-pulse width T is controlled. ON The filter circuit 15 switches the filter constant according to the determination result of the input voltage determination circuit 17.

[0053] According to this configuration, the frequency reduction function can be optimized according to the input voltage.

[0054] In addition, the present invention is not limited to the above-mentioned embodiments, and it is known that within the scope of the technical concept of the present invention, the embodiments can be appropriately changed. In addition, the number, position, shape, etc. of the above-mentioned structural components are not limited to the above-mentioned embodiments, and can be the number, position, shape, etc. suitable for implementing the present invention. In addition, in each of the drawings, the same reference numerals are marked on the same structural elements.

Claims

1. An input voltage determination circuit for determining whether an AC input voltage supplied to a flyback switching power supply device is a low voltage system or a high voltage system, wherein the flyback switching power supply device controls a conduction pulse width of a switching element according to a feedback signal in a current mode, characterized in that: When the first on-pulse width is less than a preset determination period, the input voltage determination circuit determines that it is the high voltage system, and when the first on-pulse width is greater than the determination period, the input voltage determination circuit determines that it is the low voltage system.

2. A switching power supply device, which is a flyback switching power supply device, which controls the conduction pulse width of the switching element according to the feedback signal in the current mode, characterized in that: The switching power supply device has an input voltage determination circuit. When the initial on-pulse width is less than a predetermined determination period, the input voltage determination circuit determines that the AC input voltage is a high voltage system. When the initial on-pulse width is greater than the determination period, the input voltage determination circuit determines that the AC input voltage is a low voltage system.

3. The switching power supply device according to claim 2, characterized in that: The switching power supply device includes a feedback circuit that compares the current detection signal that has passed through the filter circuit with the feedback signal to control the on-pulse width of the switching element. The filter circuit switches a filter constant according to a determination result of the input voltage determination circuit.

4. A semiconductor device, characterized in that: The input voltage determination circuit according to claim 1 is integrated on a substrate.

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