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

Abstract

To provide an input voltage determination circuit capable of determining whether or not an AC input voltage is a low voltage system or a high-voltage system by using an on-pulse width TON at a first time without using the AC input voltage as a determination voltage.SOLUTION: An input voltage determination circuit 17 that determines whether or not an AC input voltage supplied to a flyback type switching power supply device for controlling an on-pulse width TON of a switching element Q1 on the basis of a feedback signal VFB in a current mode, determines as a high-voltage system in the case where the on-pulse width TON at a first time is less than a preset determination period, and determines as a low-voltage system in the case where the on-pulse width TON at the first time is the predetermined period or larger.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] The voltage of commercial AC power varies from country to country and is roughly divided into an AC100V system (low voltage system) of 100V to 120V and an AC200V system (high voltage system) of 200V to 260V. It is desirable for a switching power supply device to operate with high efficiency at any of these AC input voltages. Therefore, a technology has been proposed for a switching power supply device that determines whether the AC input voltage is a low voltage system or a high voltage system and switches the low-frequency gain characteristics depending on the determination result (for example, see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-62930 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the conventional technology, a pulsating voltage obtained by half-wave rectifying an AC input voltage is used 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 to which the judgment voltage is input. Furthermore, since the elements of the circuit that judges the AC input voltage are generally composed of low-voltage withstand elements, a voltage divider circuit (input detection resistor) is also needed to generate the judgment voltage.

[0005] The present invention has been made in consideration of the above problems, and an object of the present invention is to provide an input voltage determination circuit that can determine 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. [Means for solving the problem]

[0006] In order to achieve the above object, the input voltage determination circuit and the switching power supply device according to the present invention are configured as follows. The input voltage determination circuit of the present invention is an input voltage determination circuit that determines whether an AC input voltage supplied to a flyback type switching power supply device that controls the on-pulse width of a switching element based on a feedback signal in a current mode is a low-voltage system or a high-voltage system, and is characterized in that it determines the system to be the high-voltage system when the initial on-pulse width is less than a predetermined determination period, and determines the system to be the low-voltage system when the initial on-pulse width is equal to or greater than the determination period. Further, the switching power supply device according to the present invention is a flyback type switching power supply device which controls the on-pulse width of a switching element based on a feedback signal in a current mode, and is characterized in that it includes an input voltage judgment circuit which judges that the AC input voltage is a high voltage system when the initial on-pulse width is less than a predetermined judgment period, and judges that the AC input voltage is a low voltage system when the initial on-pulse width is equal to or greater than the judgment period. Effect of the Invention

[0007] 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]

[0008] [Figure 1] 1 is a diagram showing an example of the configuration of a switching power supply device according to the present invention; [Diagram 2] 2 is a diagram illustrating an example of the configuration of a controller 1 illustrated in FIG. [Diagram 3] 3 is a waveform diagram showing a determination operation of the input voltage determination circuit shown in FIG. 2. [Figure 4] 3 is a graph showing a change in gain characteristic due to a switching operation of the filter circuit shown in FIG. 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

[0010] The switching power supply device of this embodiment is of a flyback type, and referring to FIG. 1, it includes a rectifier circuit DB, smoothing capacitors C1, C2, and C3, a transformer T, a controller 1, rectifier diodes D1 and D2, an error amplifier (E / A) 2, a light-emitting diode PC1 and a light-receiving transistor PC2 that constitute a photocoupler, and a current detection resistor R ID and resistors R1 and R2.

[0011] A commercial AC power supply AC is connected to AC input terminals ACin1 and ACin2 of a rectifier circuit DB in which diodes are configured in a bridge configuration. The rectifier circuit DB full-wave rectifies the input AC voltage from the commercial AC power supply AC and outputs it. The rectifier circuit DB has a rectified output positive terminal and a rectified output negative terminal. A smoothing capacitor C1 is connected between the rectified output positive terminal and the rectified output negative terminal. The rectified output negative terminal of the rectifier circuit DB is connected to a ground terminal. As a result, the commercial AC power supply AC is rectified and smoothed by the rectifier circuit DB and the smoothing capacitor C1, and a DC power supply is obtained.

[0012] The controller 1 has a switching element such as a power MOSFET (Metal Oxide Semiconductor Field Effect Transistor) and a control circuit for controlling the switching of the switching element built in. 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.

[0013] The transformer T, which 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 rectified output positive terminal 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 a current detection resistor R IDThe controller 1 is connected to a ground terminal via a terminal D. The switching element built into the controller 1 is connected between the terminal D and the terminal S. Thus, by controlling the switching element on and off, the power given 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.

[0014] Current detection resistor R ID The current ID flowing through the switching element Q1 built into the controller 1 is expressed as the current detection signal V ID The controller 1 detects the current as a current detection signal V ID It operates in the current mode based on

[0015] A smoothing capacitor C2 is connected between both terminals of the secondary winding Ns of the transformer T via a rectifier diode D1. The voltage induced in the secondary winding Ns of the transformer T is rectified and smoothed by the rectifier 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 the output voltage Vo. The line connected to the positive terminal of the smoothing capacitor C2 is the power supply line, and the line connected to the negative terminal of the smoothing capacitor C2 is the GND line connected to the ground terminal.

[0016] An error amplifier 2 is connected in series between the power supply line and the GND line. The error amplifier 2 is connected between the power supply 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. The FB / OLP terminal of the controller 1 is also connected to the ground terminal via the light-emitting diode PC1 and capacitor C4 connected in parallel. As a result, a feedback (FB) signal according 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 indicating the load state, and the feedback signal V FB The controller 1 is controlled by the feedback signal V FBBased on this, the on-pulse width (duty ratio) of the switching element is controlled, thereby controlling the amount of power supplied to the secondary side.

[0017] In addition, a smoothing capacitor C3 is connected between both terminals of the auxiliary winding Nd of the transformer T via a rectifier diode D2, and the connection point between the rectifier diode D2 and the smoothing capacitor C3 is connected to the Vcc terminal of the controller 1. As a result, the voltage generated in the auxiliary winding Nd is rectified and smoothed by the rectifier diode D2 and the smoothing capacitor C3, and is supplied to the Vcc terminal of the controller 1 as the IC power supply voltage Vcc.

[0018] Next, the circuit configuration of the controller 1 shown in FIG. 1 will be described with reference to FIG. The controller 1 can be configured as a semiconductor device such as an IC formed by sealing a semiconductor integrated circuit in a package made of resin. Referring to Fig. 2, the controller 1 includes a switching element Q1 formed of an N-channel type power MOSFET or the like, 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 flip-flop FF1.

[0019] The switching element Q1 has a drain terminal connected to the D terminal, a source terminal connected to the S terminal, and a gate terminal connected to the output terminal of the drive circuit 11. The drive circuit 11 outputs a drive signal V gs to control the on / off of the switching element Q1.

[0020] The control power supply circuit 10 includes 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 a variable voltage VR1. The comparator COMP1 has a non-inverting input terminal connected to the Vcc terminal and an inverting input terminal connected to the variable voltage VR1. The output signal from the comparator COMP1 is input to the variable voltage VR1, and the variable voltage VR1 is set to a first reference voltage Von (e.g., 15 V) when the output signal from the comparator COMP1 is at a Low level, and to a second reference voltage Voff (e.g., 10 V) lower than the first reference voltage Von when the output signal from the comparator COMP1 is at a Hi level. As a result, the output signal of the comparator COMP1 has a hysteresis characteristic, and when the smoothing capacitor C3 shown in FIG. 1 is charged by a start-up circuit (not shown), the output signal becomes Hi level when the power supply voltage Vcc for the IC exceeds the first reference voltage Von, and becomes Low level when the power supply voltage Vcc for the IC falls below the second reference voltage Voff.

[0021] The output terminal of the comparator COMP1 is connected to the regulator 101. The regulator 101 receives power from the Vcc terminal, operates when the output signal of the comparator COMP1 is at Hi level, and supplies a power supply voltage (regulator voltage V Reg etc.) are supplied to the controller 1. That is, the output signal of the comparator COMP1 is a signal that controls the on / off of the controller 1, and during steady operation of the controller 1 (when the switching operation is on), the output signal of the comparator COMP1 is at 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.

[0022] The drive circuit 11 generates a drive signal V based on the inverted output of the OR circuit OR1. gsThe OR circuit OR1 receives the output of the OR circuit OR2 at one input terminal and the output of the OVP12 at the other input terminal. When OVP12 detects an overvoltage on the secondary side based on the IC power supply voltage Vcc at the Vcc terminal, it outputs a Hi level.

[0023] The OR circuit OR2 has the output of OSC13 at one input and the inverted output Q of the flip-flop FF1 at the other. - The output of the OR circuit OR3 is input to the other input terminal. In the flip-flop FF1, the output of OSC13 is input to the set terminal S, and the output of the OR circuit OR3 is input to the reset terminal R. OSC13 outputs a clock signal whose pulse width is set to be less than the minimum on-time width of the switching element Q1. The flip-flop FF1 functions as a PWM latch circuit. As a result, when the output signal of OSC13 is at a low level (a state in which a clock signal is not being output) and the flip-flop FF1 is set, the inverted output terminal Q - When the output signal of the OR circuit OR1 is at a low level, a high-level output signal is input from the OR circuit OR1 to the drive circuit 11, and the switching element Q1 is turned on.

[0024] OSC13 is the feedback signal V FB The OSC13 is the feedback signal V FB By reducing the oscillation frequency (switching frequency) of the clock signal output in response to the load at low to medium loads, the loss in the switching element Q1 is reduced, thereby improving efficiency.

[0025] Current detection signal V input from S terminal ID is input to the OCP 14 and also 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. The OCP 14 outputs the current detection signal V ID is the preset OCP threshold V ocpIf the output of OCP14 exceeds the threshold, it detects an overcurrent and outputs a Hi level. The output of OCP14 is input to one input terminal of the OR circuit OR3. Therefore, when the output of OCP14 transitions to a Hi level, the flip-flop FF1 is reset and the switching element Q1 is turned off.

[0026] 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 and outputs a feedback signal V FB is input to the non-inverting input terminal of the comparator COMP1. The comparator COMP1 receives the feedback signal V FB The comparator COMP1 is a current sense converter for performing feedback control to control the duty ratio of the switching element Q1 based on the feedback signal V FB and a current detection signal V input to the inverting input terminal via a filter circuit 15. ID The output of the comparator COMP1 is compared with the current detection signal V ID is the feedback signal V FB When it exceeds this level, it transitions to the Low level.

[0027] The output of the comparator COMP1 is input to the other inverting input terminal of the OR circuit OR3. Therefore, when the output of the comparator COMP1 transitions to a low level, the flip-flop FF1 is reset and the switching element Q1 is turned off. As a result, the feedback signal V FB A feedback control is performed to control the duty ratio of the switching element Q1 based on this.

[0028] The filter circuit 15 is an RC filter including resistors R3, R4, and 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 the common potential.

[0029] The filter circuit 15 includes a constant current source CC2 and switching elements Q2 and Q3. The switching element Q2 is configured with an N-channel type power MOSFET or the like, and is connected in parallel with a resistor R3.

[0030] The switch element Q3 is composed of an N-channel type power MOSFET or the like. An input voltage judgment signal X from an input voltage judgment circuit 17 is input to the gate of the switch element Q3 via a NOT circuit NOT. The switch element Q3 is controlled so that it is on when the input voltage judgment signal X is at a low level and off when the input voltage judgment signal X is at a high level. The on / off state of the switch element Q3 is controlled by the input voltage judgment signal X. A constant current source CC2 and a resistor R5 are connected to a regulator voltage V Reg and the common potential, and a switch element Q3 is connected in parallel to the resistor R5. The connection point between the constant current source CC2 and the resistor R5 (switch element Q3) is connected to the gate of the switch element Q2.

[0031] 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 the common potential. The switch SW1 is in the on state at the time of start-up. The capacitor C5 is connected to the drive signal V gs At the first on-pulse (first Hi level after startup) in the C5 increases.

[0032] The comparator COMP2 has a non-inverting input terminal connected to the connection point between the constant current source CC3 and the capacitor C5, and an input terminal connected to the judgment threshold voltage V th The output of the comparator COMP2 is the input voltage judgment signal X, and the charging potential V C5 is the judgment threshold voltage V th If it exceeds this level, it becomes Hi level.

[0033] The latch circuit 171 receives the drive signal V gsWhen the falling edge of the signal is detected, the switch SW1, which was in the ON state at the time of startup, is transitioned to the OFF state, and thereafter the switch SW1 is maintained in the OFF state.

[0034] 3(a) shows the determination operation of the input voltage determination circuit 17 in the case of an AC200V system (high voltage system) with an input AC voltage of 200V to 260V. When the input AC voltage is connected and the input voltage Vin rectified and smoothed by the rectifier circuit DB and the smoothing capacitor C1 rises, the controller 1 starts up and at time t1, the drive signal V gs Output (drive signal V gs The drive signal V gs When the switching element Q1 becomes high level, the current detection signal V ID The current detection signal V ID is the OCP threshold V ocp At time t2, when the drive signal V gs At the time of start-up, since there is no output voltage Vo, the OCP 14 detects an overcurrent and turns off the switching element Q1.

[0035] Since the switch SW1 is in the on state at the time of start-up, the capacitor C5 is connected to the drive signal V gs The initial on-pulse width T ON Period T 200 The constant current of the constant current source CC3 is used to charge the capacitor. th is the period T 200 In charging, the charging potential V C5 Therefore, the input voltage judgment signal X, which is the output of the comparator COMP2, is at a low level. In other words, the constant current of the constant current source CC3 is used for charging, and the charging potential V C5 is the judgment threshold voltage V th The time it takes to reach the judgment period T th The input voltage determination circuit 17 determines the initial on-pulse width T ON is the judgment period T th If it is less than this, the input AC voltage is determined to be an AC200V system (high voltage system).

[0036] 3(b) shows the determination operation of the input voltage determination circuit 17 when the input AC voltage is an AC100V system (low voltage system) of 100V to 120V. When the input AC voltage is connected and the input voltage Vin rectified and smoothed by the rectifier circuit DB and the smoothing capacitor C1 rises, the controller 1 starts up and at time t1, the drive signal V gs Output (drive signal V gs The drive signal V gs When the switching element Q1 becomes high level, the current detection signal V ID The current detection signal V ID is the OCP threshold V ocp At time t3, when the drive signal V gs At the time of start-up, since there is no output voltage Vo, the OCP 14 detects an overcurrent and turns off the switching element Q1.

[0037] Since the switch SW1 is in the on state at the time of start-up, the capacitor C5 is connected to the drive signal V gs The initial on-pulse width T ON Period T 100 The constant current from the constant current source CC3 is used to charge the battery. In the case of an AC100V system, the current detection signal V ID However, the rising angle is gentler than that of the AC200 series. Therefore, in the period T 100 is the period T from time t1 to t2. 200 The threshold voltage V th is the period T 100 Charging potential V C5 Therefore, the input voltage judgment signal X, which is the output of the comparator COMP2, is set to a Hi level. In other words, the input voltage judgment circuit 17 is set to a value at which the first on-pulse width T ON is the judgment period T th If it is equal to or higher, the input AC voltage is determined to be AC100V system (low voltage system).

[0038] That is, the input voltage determination circuit 17 determines whether the first on-pulse width T ONIf it is determined to be a high voltage system, a low level input voltage determination signal X is output, and if it is determined to be a low voltage system, a high level input voltage determination signal X is output.

[0039] When the input voltage determination signal X is at a low level (AC 200 V system), the filter circuit 15 has the switch element Q3 turned on and the switch element Q2 turned off, and the filter constant is set based on the resistors R3, R4 and the capacitor C4.When the input voltage determination signal X is at a high level (AC 100 V system), the filter circuit 15 has the switch element Q3 turned off and the switch element Q2 turned on, and the filter constant is set based on the resistor R4 and the capacitor C4.

[0040] That is, the filter constant of the filter circuit 15 is switched to a larger value for the AC 200 V system compared to the AC 100 V system according to the judgment result of the input voltage judgment circuit 17. By switching the filter constant, the delay time of the filter circuit 15 becomes slower for the AC 200 V system compared to the AC 100 V system. As a result, in the case of the AC 200 V system, the current ID (current detection signal V ID ) peak is about to increase, so the feedback signal V FB As a result, the feedback signal V FB This decrease also decreases the oscillation frequency (switching frequency) of the clock signal output by OSC13. Therefore, as shown in Figure 4, the oscillation frequency characteristics for an AC200V system are set slightly lower than for an AC100V system, and the starting point of the frequency reduction function can also be switched.

[0041] As described above, in this embodiment, the feedback signal V FB Based on this, the on-pulse width T of the switching element Q1 ON The input voltage determination circuit 17 determines whether the AC input voltage supplied to the flyback type switching power supply device that controls the switching power supply is a low voltage system or a high voltage system, and the first ON pulse width T ONis less than the preset judgment period, it is judged to be a high-voltage system, and the first on-pulse width T ON is equal to or longer than the judgment period, it is judged to be a low pressure system. With this configuration, the initial on-pulse width T ON Using this, it is possible to determine whether the AC input voltage is a low-voltage or high-voltage system. Since there is no need to provide an input voltage determination terminal or a voltage divider circuit (input detection resistor), costs can be reduced.

[0042] Furthermore, the switching power supply device of this embodiment receives the current detection signal V via the filter circuit 15. ID and the feedback signal V FB By comparing with the ON pulse width T ON The filter circuit 15 switches the filter constant according to the result of the determination by the input voltage determination circuit 17. This configuration allows the frequency reduction function to be optimized according to the input voltage.

[0043] It is clear that the present invention is not limited to the above-described embodiments, and each embodiment can be appropriately modified within the scope of the technical concept of the present invention. Furthermore, the number, position, shape, etc. of the above-described components are not limited to the above-described embodiments, and the number, position, shape, etc. can be set to be suitable for implementing the present invention. The same components are denoted by the same reference numerals in each drawing. [Explanation of symbols]

[0044] 1 Controller 10 Control power circuit 11 Drive circuit 12 OVP (Overvoltage Protection Circuit) 13 OSC (internal oscillator) 14 OCP (Overcurrent Detection Circuit) 15 Filter Circuits 16 Feedback Circuit 17 Input voltage judgment circuit

Claims

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

2. A flyback switching power supply device that controls an on-pulse width of a switching element based on a feedback signal in a current mode, a first on-pulse width being shorter than a predetermined judgment period, and determining that the AC input voltage is a low voltage system when the first on-pulse width is equal to or longer than the judgment period.

3. a feedback circuit that controls the on-pulse width of the switching element by comparing a current detection signal that has passed through a filter circuit with the feedback signal; 3. The switching power supply device according to claim 2, wherein the filter circuit switches a filter constant in response to a result of the determination by the input voltage determination circuit.

4. 10. A semiconductor device comprising: an input voltage determination circuit according to claim 1 integrated on a substrate.

Images