JP2006166580A - Switching power supply unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To release a latch state of a switching power supply unit in a short time in such a state that the switching power supply unit is in a shutdown latch state. <P>SOLUTION: An error memory capacitor is not connected to a discharge resistor in such a state that a main power supply switch is turned on. When the shutdown is performed by power failure so that the switching power supply is in the latch state and the main power supply switch is turned off by a user, a discharging circuit switch is turned on so that the error memory capacitor may be connected to the discharge resistor. Thus, an electric charge in the error memory capacitor is instantaneously discharged through the discharge resistor, so that an ERR terminal voltage is instantaneously a specified value or lower necessary for releasing the latch to release the latch state in the short time. The main power switch is turned on again to normally operate the switching power supply. Consequently, the latch state can be released immediately after the main power supply is turned off, thus attaining high usability. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a switching power supply device in which a primary DC power supply circuit having a control circuit with a protective latch function and a secondary DC power supply circuit connected to a load are coupled and connected via a transformer.

  In a switching power supply that generates a predetermined voltage by rectifying, smoothing, and switching a commercial power supply voltage, for example, as in Patent Document 1, when a current flowing through a switching element is detected and the value exceeds a specified value, An overcurrent protection circuit for stopping the switching power supply has been devised.

  A conventional switching power supply will be described with reference to FIG.

  The primary power supply circuit connected to the commercial power supply 1 and the secondary power supply circuit connected to the load 17 are coupled and connected via a transformer (transformer) 18. The primary power supply circuit includes a rectifier 3, a primary smoothing capacitor 4, a switching element 8, an error memory capacitor 5, a control circuit 7 for controlling the switching element 8 and the error memory capacitor 5, a current detection resistor 9, and a primary main winding of a transformer 18. It consists of a wire 10 and an auxiliary winding 11. The secondary power supply circuit includes a secondary winding 12 of a transformer 18, a rectifier diode 13, a secondary smoothing capacitor 14, and an output voltage detection circuit unit 16.

  The AC voltage supplied from the commercial power source 1 when the main power switch 2 is turned on is rectified and smoothed through the rectifier 3 and the primary smoothing capacitor 4 to have a constant voltage value. This voltage is supplied to the switching element 8 through the primary main winding 10. When the switching element 8 is switched, a pulse voltage is induced in the secondary winding. The voltage induced in the secondary power supply circuit is rectified and smoothed by the rectifier diode 13 and the secondary smoothing capacitor 14 to become a DC voltage Vout and supplied to the load 17.

  The output voltage detector 16 monitors the output voltage Vout and outputs a feedback signal fs to the feedback terminal (FB terminal) of the control circuit 7 on the primary side via the photocoupler 15. The control circuit 7 generates a control signal fg based on this feedback signal, and controls on / off of the switching element 8.

  When the output voltage Vout becomes equal to or higher than the specified voltage value, the PWM comparator (not shown here) in the control circuit 7 shortens the ON period of the gate drive pulse of the switching element (eg, FET) 8 and changes from the primary side to the secondary side. Control is performed to reduce the supply of power energy to the output voltage Vout.

  When the output voltage Vout becomes equal to or lower than the specified voltage value, the PWM comparator in the control circuit 7 increases the ON period of the gate drive pulse of the switching element 8 and increases the supply of power energy from the primary side to the secondary side. The output voltage Vout is controlled to be increased.

  As described above, the output voltage Vout can be controlled to a substantially constant voltage value by controlling the amount of power energy supplied from the primary side to the secondary side.

  Further, the control circuit 7 has a latch function capable of continuously outputting the control signal fg for holding the switching element 8 in the OFF state based on the terminal voltage of the error memory capacitor 5.

  The overcurrent protection operation of the switching power supply will be described with reference to FIG.

  The drain current Id of the switching element (eg, FET) 8 is converted into a voltage value by the current detection resistor 9 and input to the current detection terminal (CS terminal) of the control circuit 7. When the drain current Id increases due to a decrease in the voltage value of the commercial power supply 1 or an increase in the load 17 and the CS terminal voltage of the control circuit 7 exceeds the specified value Vmax (= Imax × R9), the control circuit 7 A constant current is output from (ERR terminal). An error memory capacitor 5 is connected to the ERR terminal, and the current output from the ERR terminal is charged in the error memory capacitor 5.

  When the terminal voltage of the error memory capacitor 5 exceeds the specified value Vea, the control circuit 7 turns off the gate drive pulse of the FET 8 and stops the switching operation (shutdown).

Once the switching operation is terminated by the operation as described above, the control circuit 7 continues the gate drive pulse of the FET 8 in the OFF state until the terminal voltage of the error memory capacitor 5 becomes equal to or lower than the specified value Vei (latch state). ). This state is released when the terminal voltage of the error memory capacitor 5 becomes equal to or lower than the specified value Vei.
Japanese Patent Laid-Open No. 2001-211638

  However, in the above conventional example, since the discharge path of the error memory capacitor 5 is only in the control circuit 7, even if an abnormal state such as a decrease in the voltage value of the commercial power supply 1 or an increase in the load 17 is removed, the voltage A certain amount of time is required for the value to become equal to or less than the specified value Vei, and during this period, it becomes impossible to use a device equipped with this power supply.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a switching power supply device that shortens the period until the latch state of the control circuit is released and enables rapid restart by turning on and off the main power supply. It is usability improvement by providing.

  In order to achieve the above object, the present invention has the following features.

[1]: a rectifier circuit for rectifying an AC power supply voltage;
A circuit breaker for cutting off the AC power supply voltage to the rectifier circuit;
A transformer provided with a control coil on the primary side connected to the subsequent stage of the rectifier circuit;
A smoothing capacitor connected to the latter stage of the rectifier circuit;
A switching element whose main terminal is connected to the control coil of the transformer;
A rectifying and smoothing circuit connected to the secondary side of the transformer;
Among the rectifier circuit, smoothing capacitor, transformer, and switching element,
A current detection circuit for detecting a current flowing in at least one;
An error memory capacitor that is charged based on a detection result of the current detection circuit;
A control circuit for controlling charging to the switching element and the error memory capacitor;
In the switching power supply device having a discharge circuit for discharging the error memory capacitor in the subsequent stage of the rectifier circuit,
A switching power supply device comprising: detecting a voltage value at a subsequent stage of the rectifier circuit, and discharging the error memory capacitor through the discharge circuit when the voltage value is equal to or lower than a preset value.

[2]: a rectifier circuit for rectifying the AC power supply voltage;
A circuit breaker for cutting off the AC power supply voltage to the rectifier circuit;
A transformer provided with a control coil on the primary side connected to the subsequent stage of the rectifier circuit;
A smoothing capacitor connected to the latter stage of the rectifier circuit;
A switching element whose main terminal is connected to the control coil of the transformer;
A rectifying and smoothing circuit connected to the secondary side of the transformer;
Among the rectifier circuit, smoothing capacitor, transformer, and switching element,
A current detection circuit for detecting a current flowing in at least one;
An error memory capacitor that is charged based on a detection result of the current detection circuit;
A control circuit for controlling charging to the switching element and the error memory capacitor;
In the switching power supply device having a discharge circuit for discharging the error memory capacitor in the subsequent stage of the rectifier circuit,
A discharge circuit breaker for cutting off the connection of the discharge circuit;
The breaker and the discharge circuit breaker operate in conjunction with each other,
When the connection between the AC power supply voltage and the rectifier circuit is cut off by turning off the circuit breaker,
Turn on the discharge circuit breaker and connect the discharge circuit and the error memory capacitor to discharge the error memory capacitor,
When the AC power supply voltage and the rectifier circuit are connected by turning on the circuit breaker,
A switching power supply unit configured to cut off a connection between the discharge circuit and the error memory capacitor.

As explained above,
According to the first invention of the present invention,
A rectifier circuit for rectifying the AC power supply voltage;
A circuit breaker for cutting off the AC power supply voltage to the rectifier circuit;
A transformer provided with a control coil on the primary side connected to the subsequent stage of the rectifier circuit;
A smoothing capacitor connected to the latter stage of the rectifier circuit;
A switching element whose main terminal is connected to the control coil of the transformer;
A rectifying and smoothing circuit connected to the secondary side of the transformer;
Among the rectifier circuit, smoothing capacitor, transformer, and switching element,
A current detection circuit for detecting a current flowing in at least one;
An error memory capacitor that is charged based on a detection result of the current detection circuit;
A control circuit for controlling charging to the switching element and the error memory capacitor;
In the switching power supply device having a discharge circuit for discharging the error memory capacitor in the subsequent stage of the rectifier circuit,
By detecting the voltage value of the latter stage of the rectifier circuit, and when the voltage value is equal to or lower than a preset value, the error memory capacitor is discharged through the discharge circuit,
Since the latching state of the switching power supply can be released in a short period of time, the waiting time by the user until the return can be greatly reduced compared to the conventional case. Therefore, it is possible to restart by rapid power-on, which improves usability.

According to the second invention of the present invention,
A rectifier circuit for rectifying the AC power supply voltage;
A circuit breaker for cutting off the AC power supply voltage to the rectifier circuit;
A transformer provided with a control coil on the primary side connected to the subsequent stage of the rectifier circuit;
A smoothing capacitor connected to the latter stage of the rectifier circuit;
A switching element whose main terminal is connected to the control coil of the transformer;
A rectifying and smoothing circuit connected to the secondary side of the transformer;
Among the rectifier circuit, smoothing capacitor, transformer, and switching element,
A current detection circuit for detecting a current flowing in at least one;
An error memory capacitor that is charged based on a detection result of the current detection circuit;
A control circuit for controlling charging to the switching element and the error memory capacitor;
In the switching power supply device having a discharge circuit for discharging the error memory capacitor in the subsequent stage of the rectifier circuit,
A discharge circuit breaker for cutting off the connection of the discharge circuit;
The breaker and the discharge circuit breaker operate in conjunction with each other,
When the connection between the AC power supply voltage and the rectifier circuit is cut off by turning off the circuit breaker,
Turn on the discharge circuit breaker and connect the discharge circuit and the error memory capacitor to discharge the error memory capacitor,
When the AC power supply voltage and the rectifier circuit are connected by turning on the circuit breaker,
By disconnecting the connection between the discharge circuit and the error memory capacitor,
Since the latching state of the switching power supply can be released in a short period of time, the waiting time by the user until the return can be greatly reduced compared to the conventional case. Therefore, it is possible to restart by rapid power-on, which improves usability.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to examples.

  Hereinafter, description will be given with reference to the accompanying drawings.

  FIG. 1 shows a switching power supply to which a first embodiment of the present invention is applied.

  In FIG. 1, the basic structure is the same as that of the conventional example, but compared to the circuit of the conventional example, a discharge resistor 123 for discharging the error memory capacitor 105, a voltage detector 126 at the subsequent stage of the rectifier circuit 103, a discharge resistor. By adding a switch 122 for turning on / off the connection of 123 to the error memory capacitor 105 to the configuration, the error memory capacitor 105 can be rapidly discharged, so that the power supply can be turned off and on quickly.

  Also, description of the same components as those in the conventional example is simplified or omitted.

  When the drain current Id of the switching element 108 increases due to a decrease in the voltage value of the commercial power supply 101 or an increase in the load 117 and the CS terminal voltage of the control circuit 107 exceeds the specified value Vmax, the control circuit 107 is fixed from the ERR terminal. Output current. An error memory capacitor 105 is connected to the ERR terminal, and the current output from the ERR terminal is charged in the error memory capacitor 105.

  When the terminal voltage of the error memory capacitor 105 exceeds the specified value Vea due to this charging current, the control circuit 107 turns off the gate drive pulse of the FET 108 and shuts down the switching power supply, so that the terminal voltage of the error memory capacitor 105 becomes the specified value. The latched state is maintained until it becomes Vei or less.

  The switching power supply of FIG. 1 includes a discharge resistor 123 for discharging the error memory capacitor 105, a voltage detection circuit 126 after the rectifier circuit 103, and a switch 122 for turning on / off the connection of the discharge resistor 123 with the error memory capacitor 105. ing.

  The voltage detection circuit 126 monitors the voltage Vp at the subsequent stage of the rectifier circuit 103 and turns off the transistor 121 included in the voltage detection circuit 126 when the voltage Vp becomes equal to or less than the specified value Vpl. A normally closed relay 122 is connected to the transistor 121, and the relay 122 is closed when the transistor 121 is turned off, and the charge of the error memory capacitor 105 is discharged through the discharge resistor 123.

  In a state where the main power switch 102 is turned on, the values of the voltage dividing resistors 124 and 125 are determined so that the transistors in the voltage detection unit 126 are kept on (becomes a specified value Vpl or more).

  Each operation in discharging will be described with reference to FIG.

  When the main power switch 102 is turned on, the transistor 121 in the voltage detection unit 126 is on and the relay 122 is open, so that the error memory capacitor 105 is not connected to the discharge resistor 123.

  When the power supply is shut down due to a power failure, the main power switch 102 is turned off by the user, and when the voltage Vp after the rectifier circuit 103 drops to a specified value Vpl or less, the transistor 121 in the voltage detection circuit 126 is turned off, and the relay 122 is closed, and the charge in the error memory capacitor 105 is instantaneously discharged through the discharge resistor 123, so that the ERR terminal voltage instantaneously becomes Vei or less. As a result, the latched state can be released in a short time.

  By turning on the main power switch 102 again, the switching power supply can operate normally.

  With the above configuration, the latched state can be released immediately after the main power is turned off, so that usability can be improved.

  FIG. 3 shows a switching power supply to which the second embodiment of the present invention is applied.

  In FIG. 3, the basic structure is the same as that of the conventional example, but the error memory operates in conjunction with the discharge resistor 223 for discharging the error memory capacitor 205 and the main power switch 202 in comparison with the circuit of the conventional example. By adding a switch 222 for turning on and off the connection between the capacitor 205 and the discharge resistor 223 to the configuration, the error memory capacitor 205 can be rapidly discharged, and the main power supply can be turned off and on.

  Also, description of the same components as those in the conventional example is simplified or omitted.

  When the drain current Id of the switching element 208 increases due to a decrease in the voltage value of the commercial power supply 201 or an increase in the load 217, and the CS terminal voltage of the control circuit 207 exceeds the specified value Vmax, the control circuit 207 is fixed from the ERR terminal. Output current. An error memory capacitor 205 is connected to the ERR terminal, and the current output from the ERR terminal is charged in the error memory capacitor 205.

  When the terminal voltage of the error memory capacitor 205 exceeds the specified value Vea due to this charging current, the control circuit 207 turns off the gate drive pulse of the FET 208 and shuts down the switching power supply, so that the terminal voltage of the error memory capacitor 205 becomes the specified value. The latched state is maintained until it becomes Vei or less.

  3 includes a discharge resistor 223 for discharging the error memory capacitor 205 and a switch 222 that operates in conjunction with the main power switch 202 to turn on and off the connection between the error memory capacitor 205 and the discharge resistor 223. Yes. For example, the main power switch 202 and the switch 222 may be mechanically connected by a rod or the like, and a higher-order switch may be prepared so that one switch can be switched off and on at the same time.

  Each operation in discharging will be described with reference to FIG.

  A switch 222 that turns off the connection between the error memory capacitor 205 and the discharge resistor 223 that operates in conjunction with the main power switch 202 is in an off state when the main power switch 202 is on. The resistor 223 is not connected. However, when the main power switch 202 is turned off, the switch 222 is turned on, the error memory capacitor 205 and the discharge resistor 223 are connected, and the charge of the capacitor 205 is instantaneously discharged through the discharge resistor 223, so that ERR The terminal voltage instantaneously falls below Vei. As a result, the latched state can be released in a short time.

  With the above configuration, the latched state can be released immediately after the main power is turned off, so that usability can be improved.

It is a figure explaining the 1st Example of this invention. It is a figure explaining the 1st Example of this invention. It is a figure explaining the 2nd Example of this invention. It is a figure explaining the 2nd Example of this invention. It is a figure explaining the switching power supply of a prior art example. It is a figure explaining the latched state of a prior art example.

Explanation of symbols

1 AC power supply 2 Main power switch 3 Rectifier circuit (bridge diode)
4 Primary smoothing capacitor 5 Error memory capacitor 6 Start resistor 7 Control circuit unit 8 Switching element 9 Current detection resistor 10 Transformer primary main winding 11 Transformer auxiliary winding 12 Transformer secondary winding 13 Rectifier diode 14 Secondary smoothing capacitor DESCRIPTION OF SYMBOLS 15 Photocoupler 16 Output voltage detection circuit part 17 Load 18 Transformer 121 Transistor 122 Lomal closed relay 123 Discharge resistor 124 Divider resistor 125 Divider resistor 126 Voltage detector circuit 222 Discharge resistor connection switch

Claims (2)

A rectifier circuit for rectifying the AC power supply voltage;
A circuit breaker for cutting off the AC power supply voltage to the rectifier circuit;
A transformer provided with a control coil on the primary side connected to the subsequent stage of the rectifier circuit;
A smoothing capacitor connected to the latter stage of the rectifier circuit;
A switching element whose main terminal is connected to the control coil of the transformer;
A rectifying and smoothing circuit connected to the secondary side of the transformer;
Among the rectifier circuit, smoothing capacitor, transformer, and switching element,
A current detection circuit for detecting a current flowing in at least one;
An error memory capacitor that is charged based on a detection result of the current detection circuit;
A control circuit for controlling charging to the switching element and the error memory capacitor;
In the switching power supply device having a discharge circuit for discharging the error memory capacitor in the subsequent stage of the rectifier circuit,
A switching power supply device comprising: detecting a voltage value at a subsequent stage of the rectifier circuit, and discharging the error memory capacitor through the discharge circuit when the voltage value is equal to or lower than a preset value. A rectifier circuit for rectifying the AC power supply voltage;
A circuit breaker for cutting off the AC power supply voltage to the rectifier circuit;
A transformer provided with a control coil on the primary side connected to the subsequent stage of the rectifier circuit;
A smoothing capacitor connected to the latter stage of the rectifier circuit;
A switching element whose main terminal is connected to the control coil of the transformer;
A rectifying and smoothing circuit connected to the secondary side of the transformer;
Among the rectifier circuit, smoothing capacitor, transformer, and switching element,
A current detection circuit for detecting a current flowing in at least one;
An error memory capacitor that is charged based on a detection result of the current detection circuit;
A control circuit for controlling charging to the switching element and the error memory capacitor;
In the switching power supply device having a discharge circuit for discharging the error memory capacitor in the subsequent stage of the rectifier circuit,
A discharge circuit breaker for cutting off the connection of the discharge circuit;
The breaker and the discharge circuit breaker operate in conjunction with each other,
When the connection between the AC power supply voltage and the rectifier circuit is cut off by turning off the circuit breaker,
Turn on the discharge circuit breaker and connect the discharge circuit and the error memory capacitor to discharge the error memory capacitor,
When the AC power supply voltage and the rectifier circuit are connected by turning on the circuit breaker,
A switching power supply unit configured to cut off a connection between the discharge circuit and the error memory capacitor.

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