JP3496525B2 - Power supply - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] BACKGROUND OF THE INVENTION 1. Field of the Invention
Constant voltage is output by the on / off operation of the switching element.
The present invention relates to a power supply device. [0002] 2. Description of the Related Art Conventionally, as shown in FIG.
Rectified by the rectifier circuit DB
The input DC voltage is converted to a constant voltage and supplied to the load 3.
A power supply device provided with a power supply circuit 2 has been proposed. here
In addition, a low-pass filter is provided between the AC power supply Vs and the rectifier circuit DB.
The filter circuit F is inserted. In addition, the DC power supply circuit 2
Is a reactor connected between the DC output terminals of the rectifier circuit DB.
Series circuit of the channel CH, the switching element Q1, and the resistor R4.
And a series circuit of the switching element Q1 and the resistor R4.
The direct connection between the column-connected diode D1 and the smoothing capacitor C
Controlling ON / OFF of the column circuit and the switching element Q1
And a control circuit 10. This DC power supply circuit
2 is a boost chopper circuit operating in the current boundary mode.
Therefore, the active filter as a harmonic suppression circuit of the input current
Also functions as a filter circuit. The control circuit 10 includes a switching element Q1
The connection point with the resistor R4 is connected to the Is terminal,
The current flowing through the switching element Q1 can be detected, and
A resistor whose one end is connected to the high potential side of the DC output terminal of the circuit DB.
Both resistors R1, R in a series circuit of an anti-R1 and a resistor R2.
Connection point 2 is V_MLConnected to terminal, output of rectifier circuit DB
The voltage can be monitored and the secondary winding of reactor CH
V through the resistor R3_Z0Connected to terminal, reactor CH
To detect the point where the current flowing through
I have. Note that the input is made by a series circuit of the resistor R1 and the resistor R2.
It constitutes a force voltage detection circuit. Next, the operation of the power supply device shown in FIG. 6 will be described.
You. However, below, it flows to the switching element Q1.
Current is I_Q, The current flowing through the diode D1 is represented by I_D, Riak
The current flowing in the torque channel CH is I_L, Reactor CH reactor
And the voltage between the DC output terminals of the rectifier circuit DB (
The input voltage of the DC power supply circuit 2) to e._i, Smooth condensate
The voltage across the terminal C (that is, the output voltage of the DC power supply circuit 2)
To e_oIt will be described as. When the switching element Q1 is turned on, the switch
The switching element Q1 has I_Q= (E_i/ L) × t (however,
t is the time from when the switching element Q1 is turned on.
Current) flows. The control circuit 10 controls the current I_QThe pea
Is proportional to the voltage waveform detected by the input voltage detection circuit.
To turn off the switching element Q1. switch
When the switching element Q1 turns off, it is stored in the reactor CH.
Energy is released via diode D1. Sand
Chi,-(e_o-E_i) A current flows through the diode D1 with a slope of / L.
I_DFlows. After that, the control circuit 10_Z0Terminal
By detecting that the pressure has fallen below a certain voltage.
Current I flowing in actuator CH_LIs zero
Then, the switching element Q1 is turned on. Toes
And operates in the current boundary mode. Repeat the above operation
As a result, the reactor CH is indicated by a solid line in FIG.
Such current I_LFlows (current I_LIs the switching element Q
While I is on, I_QAnd the switching element Q1
Is off while I_D), The switching element Q1
Are turned on and off as shown in FIG. In addition, exchange
A low-pass filter F is connected between the power supply Vs and the rectifier circuit DB.
7A, the input current is indicated by a dashed line in FIG. 7A.
The waveform becomes as shown, and the power factor becomes extremely close to 1. The power supply device shown in FIG. 6 includes a resistor R5 and a resistor R5.
One end of resistor R5 is a diode consisting of a series circuit with R6
The output voltage connected to the connection point between D1 and the smoothing capacitor C
A pressure detection circuit is provided, and the connection point of the two resistors R5 and R6 is
V of control circuit 10_monConnected to terminal. That is,
The output voltage of DC power supply circuit 2 is divided by resistors R5 and R6.
The applied voltage is V of the control circuit 10._monInput to the terminal
Swelling. The control circuit 10_monInput to the terminal
Voltage is the reference voltage V_refTo match, that is,
Output voltage e of DC power supply circuit 2_oSo that the
The duty ratio of the switching element Q1 is controlled. [0007] By the way, in the above power supply device,
The resistance R5 of the output voltage detection circuit
If it becomes_mon= 0, but the control circuit 10_mon
= V _refSo that the DC power supply circuit 2
Output voltage e_oRises and overvoltage is applied to the smoothing capacitor C.
The smoothing capacitor C is destroyed.
(The safety valve may operate.) The occurrence of this kind of malfunction
In order to prevent the output voltage e,_o
Switching element when the voltage rises above the set voltage.
Overvoltage protection circuit 2 for stopping the on / off operation of the child Q1
0 'is provided. The overvoltage protection circuit 20 'outputs
Voltage e_oIs divided by the resistor R7 and the resistor R8.
The comparator CP input to the input terminal and the control circuit 10
Control power supply V_ccAnd V of the control circuit 10_ccWith terminal
Base is connected to the output terminal of comparator CP
Transistor Q2, and both ends of a resistor R8.
When the terminal voltage exceeds the reference voltage VA, the comparator CP
Becomes high level, and the switching element Q2 is turned off.
The V of the control circuit 10_ccThe power supply to the terminal is stopped.
To stop the boost operation. That is, the overvoltage protection circuit 2
By providing 0 ', the resistor R5 is opened.
Can also prevent the smoothing capacitor C from being destroyed.
You can. [0008] By the way, the above-mentioned boosting
Output voltage e of chopper circuit (DC power supply circuit 2)_oFigure 8
As shown by the solid line, the lip at twice the commercial frequency
Output voltage of the boost chopper circuit during normal operation.
Pressure e_oThe maximum value in the fluctuation range of_H, The minimum value is E_L,
Let the withstand voltage of the smoothing capacitor C be E_maxThen, overvoltage protection
Stop circuit 20 'is set to E_HGreater than and E_maxSmaller than
It must be designed to operate at a predetermined voltage. But
Therefore, the minimum value and the maximum value of the reference voltage VA are respectively set to VA
_min, VA_{m ax}And the minimum value and the maximum value of the resistance value of the resistor R7.
Value is R7_min, R7_maxAnd the resistance value of the resistor R8
The minimum value and the maximum value of_min, R8_maxTo be
And the resistance and reference voltage so that the following two equations are satisfied.
Need to be specified. VA_max× (R7_max+ R8_min) / R8_min> E_H VA_min× (R7_min+ R8_max) / R8_max<E_max In short, the overvoltage protection circuit in the above-mentioned conventional power supply device
20 'has a large design constraint on component variations.
In addition, there is a problem that the cost is large. The present invention has been made in view of the above circumstances.
Yes, its purpose is to increase the output voltage abnormally with a simple configuration
To provide a power supply that can reduce
You. [0010] According to the first aspect of the present invention, there is provided
In order to achieve the object, the switching device includes a switching element.
By turning on and off the switching element,
DC power supply circuit that converts voltage to a constant voltage and outputs
Output voltage detection circuit for detecting the output voltage of the
The output voltage is changed to the reference voltage according to the detection output by the detection circuit.
Controls switching element on / off to match pressure
Control means, and the detection voltage by the output voltage detection circuit is
Below the reference voltage set below the reference voltage.
When the switching element is kept in the off state when
Voltage prevention meansWherein the input DC voltage is an AC power supply.
DC power generated by rectification by a rectifier circuit
The circuit is connected to the reactor connected between the output terminals of the rectifier circuit.
A series circuit of a diode and a capacitor,
Between the connection point with the diode and the low potential side end of the rectifier circuit
Flow into the reactor with the inserted switching element
Current detection means for detecting the current flowing through the reactor
Each time the current becomes zero, the switching element is turned on.
And a step-up chopper circuit including
The stopping means has a threshold voltage smaller than the reference voltage and
A voltage proportional to the output voltage is applied to the control electrode
A three-terminal switch element comprising a MOSFET;
The switching when the three-terminal switching element is turned off
The element is turned off, and the output voltage detection circuit
The output voltage is lower than a predetermined value set lower than the reference voltage.
The detection output of the current detection means when the
To turn off the switching element.
To holdThe output voltage detection circuit
Part of the circuit becomes open and the output voltage detection circuit
When the output voltage falls below the predetermined value, overvoltage prevention means
ByThe output of the current detection means is biased
SaidThe switching element is kept off
Output voltage with a simpler configuration than beforeAbnormalRise
Can be prevented. [0011] [0012] [0013] [0014] DESCRIPTION OF THE PREFERRED EMBODIMENTS First, FIG.
It will be described with reference to FIG. The present invention provides a switch for the DC power supply circuit 2.
A control circuit 10 for controlling on / off of the switching element Q1;
Output voltage detection consisting of a series circuit of resistors R5 and R6
The circuit, the potential at the connection point between the resistors R5 and R6 and a predetermined value
Vs and the potential drops below a predetermined value Vs
ON / OFF of the switching element Q1 by the control circuit 10
And an overvoltage prevention circuit 20 for stopping the control.
The same components as those of the conventional configuration are denoted by the same reference numerals.
The description is omitted. (Embodiment 1) The basic configuration of this embodiment is
And the overvoltage protection as shown in FIG.
The difference is that the circuit 20 is provided. That is, this implementation
The overvoltage protection circuit 20 in the embodiment includes the resistor R10 and the MO
A three-terminal switch element Q3 (hereinafter, switch
The switching power supply V is connected in series with the switching element Q3)._cc
And the connection between the resistor R10 and the switching element Q3.
The connection point is the V of the control circuit 10 via the diode D2._Z0Terminal
And the gate of the switching element Q3 is connected to the resistor R5
And the resistor R6. In other words, control
V of circuit 10_monTerminal and gate of switching element Q3
And are connected. The same components as those of the conventional configuration
Are denoted by the same reference numerals, and description thereof is omitted. Now, the resistor R5 of the output voltage detecting circuit is open.
Let's consider the case when it becomes a state. The resistor R5 becomes open
And V of the control circuit 10_monWhen the voltage input to the terminal is zero
If the overvoltage protection circuit 20 is not provided,
Output voltage e of the source circuit 20_oRises and the smoothing capacitor C
There is a risk of destruction. However, in this embodiment,
Since the overvoltage protection circuit 20 is provided, the resistance R5
Is open, the gate voltage of the switching element Q3 is
The voltage drops, the switching element Q3 turns off, and the control power
V_ccIs the control circuit 1 via the resistor R10 and the diode D2.
V of 0_Z0Since it is applied to the terminal, the secondary of the reactor CH
The detection voltage by the winding is biased and V_Z0Terminal insertion
The force voltage does not become zero, and as a result, the DO terminal of the control circuit 10
No ON signal is output from the
The off state of Q1 is maintained, and the DC power supply circuit 20
Pa operation stops. Here, the switch of the overvoltage protection circuit 20 is switched.
Threshold voltage V of gate voltage of switching element Q3_thIs control times
Reference voltage V of road 10_refSmaller than (V_th<V_ref)
Need to be specified. Further, the effective value of the AC power supply Vs is expressed as V_in
When the power is turned on, the DC power supply circuit 20
The following equation must be satisfied so that the operation can be started. V_in × 2^1/2× R6 / (R5 + R6)> V_th In this embodiment, a conventional overvoltage protection circuit 20 '(FIG.
), A resistor R10, a switching element
Simple circuit with only three components, child Q3 and diode D2
When the resistor R5 is short-circuited at low cost with the configuration
Prevent abnormal rise in voltage across smoothing capacitor C
And consequently prevent the load 3 from being adversely affected.
be able to. Also, the conventional overvoltage protection circuit 20 '
Less design constraints on component variations
be able to. [0017](Reference Example 1) In this reference example The basic configuration is substantially the same as that of the first embodiment.
The point that the voltage prevention circuit 20 is configured as shown in FIG.
There is a feature.In this reference exampleThe power supply device is the same as that of the first embodiment.
The three-terminal switching element Q3 (switch) in the voltage prevention circuit 20
As the switching element Q3),
Using an bipolar transistor, the resistor R6 is replaced by a resistor R6a.
And a resistor R6b (may be divided into two or more),
The base of the switching element Q3 and the V of the control circuit 10
_monThe above resistor R6a is inserted between the terminal
You.In this reference exampleSwitch when power is turned on during normal operation.
The resistor R6 is used to make sure that the switching element Q3 can be turned on.
It is necessary to determine the resistance values of a and R6b. In addition,This reference
ExampleSince the basic operation is substantially the same as that of the first embodiment, the description is omitted.
You. [0018](Reference Example 2) by the way,The aboveIn the embodiment, the control is performed in the current boundary mode.
Power supply device with a boost chopper circuit
Is a connection point between the resistors R5 and R6, as shown in FIG.
Is fed back to the control circuit 10 to switch
On and off the smoothing capacitor C
Including a switching power supply circuit 2a for generating a DC voltage
I just need to be. In the example shown in FIG. 3, a resistor R10 and a switch
The connection point with the switching element Q3 is connected to the base and the collector is
Drive output terminal DO of control circuit 10 and switching element
A switching element Q4 connected between the
ing. Thus, the resistor R5 of the output voltage detection circuit is opened.
In the state, the switching element consisting of MOSFET
When the gate voltage of Q3 drops, switching element Q3 turns off.
The switching element Q4 is turned on.
Switching element Q1 of switching power supply circuit 2a to off state
And the voltage across the smoothing capacitor C is different.
It can be prevented from constantly rising. [0019](Reference Example 3) By the way, Embodiment 1 andAnd in Reference Example 1Is the current boundary mode.
Power supply with a boost chopper circuit controlled by
As described above, as shown in FIG.
Feedback to the control circuit 10
On / off control of switching element Q1 for smoothing capacitor
DC-DC converter 2 for generating a DC voltage across C
a 'may be provided. In the example shown in FIG.
10 is V_monSwitch only based on terminal input voltage
And the control power supply V_ccAnd control times
Road 10 V_ccSwitching element inserted between terminals
Connection of the element Q5, the resistor R10 and the switching element Q3
The point is connected to the base and the switching element Q5 is connected to the collector.
Connected to the base and the emitter is connected to ground.
Embodiment 1 and Embodiment 4 are different from Embodiments 1 and 2 in thatAnd reference
Example 1 andDifferent.In this reference exampleIs the resistance of the output voltage detection circuit.
When the anti-R5 is opened, the switching element Q3 is turned off.
Since the switching element Q4 is turned on, the control circuit
Control power V to 10_ccPower supply from the
Since the switching element Q1 is kept off,
Prevents the voltage across capacitor C from rising abnormally.
Can be [0020] Claims of the InventionOneThe invention provides a switching element
By turning the switching element on and off
A DC power supply circuit for converting an input DC voltage to a constant voltage and outputting the same,
Output voltage detection circuit that detects the output voltage of the DC power supply circuit
And the output according to a detection output by an output voltage detection circuit.
Turn off the switching element so that the voltage matches the reference voltage.
Control means for controlling turn-off, and an output voltage detection circuit.
A predetermined value at which the detection voltage is set smaller than the reference voltage
The switching element is turned off when the
Overvoltage prevention meansThe input DC voltage
Is generated by rectifying AC power with a rectifier circuit.
The DC power supply circuit is connected between the output terminals of the rectifier circuit.
A series circuit of a reactor, a diode and a capacitor,
Connection point between reactor and diode and low potential of rectifier circuit
A switching element inserted between the side element and a rear end;
Current detection means for detecting the current flowing in the reactor;
Each time the current flowing through the
A boost chopper circuit having means for turning on the
Therefore, the overvoltage prevention means sets the threshold voltage to be lower than the reference voltage.
And the control electrode has a voltage proportional to the output voltage.
-Terminal switch element consisting of MOSFET to which voltage is applied
When the three-terminal switch element is turned off,
Turn off the switching element and detect the output voltage
The detection voltage by the circuit is set smaller than the reference voltage.
When the current value falls below the specified value,
The switching element by biasing the output
Keeps it off, Part of the output voltage detection circuit
Open state and the detection voltage of the output voltage detection circuit is
If the voltage falls below the specified value, the overvoltage protection meansTelephone
The bias is applied to the detection output by theS
Since the switching element is kept off,
Output voltage with simple configurationAbnormalTo prevent the rise
There is an effect that can be.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram showing a first embodiment. FIG. 2 is a main part circuit diagram of Reference Example 1 . FIG. 3 is a schematic circuit diagram of Reference Example 2 . FIG. 4 is a schematic circuit diagram of Reference Example 3 . FIG. 5 is a basic conceptual diagram of the present invention. FIG. 6 is a circuit diagram showing a conventional example. FIG. 7 is an operation explanatory view of the above. FIG. 8 is an operation explanatory view of the above. [Description of Signs] 2 DC power supply circuit 3 Load C Smoothing capacitor CH Reactor R5 Resistance Vs AC power supply DB Rectifier circuit Q1 Switching element Q3 Three-terminal switch element 10 Control circuit 20 Overvoltage protection circuit

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02M 3/155

Claims (1)

(1) A DC power supply circuit that includes a switching element and converts an input DC voltage into a constant voltage by turning on and off the switching element, and detects an output voltage of the DC power supply circuit. An output voltage detection circuit, control means for controlling on / off of a switching element such that the output voltage matches a reference voltage according to an output detected by the output voltage detection circuit, and a detection voltage by the output voltage detection circuit is higher than the reference voltage. Overvoltage prevention means for holding the switching element in an off state when the input DC voltage falls below a predetermined value which is set to be small.
DC power supply circuit
Reactor and diode connected between the output terminals of the rectifier circuit
Series circuit of the capacitor and the
Between the connection point of the rectifier circuit and the low-potential end of the rectifier circuit.
And the current flowing through the reactor
The current detection means to detect
Means for turning on said switching element every time
A boost chopper circuit comprising:
Means that the threshold voltage is lower than the reference voltage and
MOS in which a voltage proportional to the output voltage is applied to an electrode
A three-terminal switch element comprising an FET;
When the switching element is turned off, the switching element is turned off.
The output voltage is detected by the output voltage detection circuit.
Is lower than a predetermined value set smaller than the reference voltage.
Output, the detection output of the current detection means is biased.
To keep the switching element in the off state.
Power apparatus according to claim Rukoto.