JPH1169801A - Power control circuit - Google Patents

Abstract

(57) [Problem] To provide a power supply circuit with a primary side P
Provided is a power supply control circuit that stops the operation of the secondary-side PWM circuit at the same time as the stop of the operation of the WM circuit. SOLUTION: When an abnormality occurs on the primary side of a transformer T2, a protection circuit on the primary side of the transformer T2 operates to generate a reset signal, and the reset signal controls the power supply circuit on the secondary side of the transformer T2. Operation of the main PWM1 circuit 3 of the CPU for the
Secondary synchronous main PWM circuit 5, main PWM
The operations of the two circuits 4 and the sub-PWM2 circuit 7 are simultaneously stopped. When the protection operation is performed by the protection circuits provided corresponding to the main PWM2 circuit 4, the sub-PWM2 circuit 7, etc., the operation is stopped independently.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply control circuit for controlling a power supply circuit used in a copying machine, a printer or the like.

[0002]

2. Description of the Related Art FIG. 1 is a diagram showing a schematic configuration of a conventional power supply circuit, and FIG. 2 is a block diagram showing a configuration of a power supply circuit control CPU (central processing unit) which is a conventional power supply control circuit. Hereinafter, the operation of the conventional power supply circuit and power supply control circuit will be described with reference to FIGS.

The power supply circuit control CPU shown in FIG. 2 has a main PWM (pulse width modulation) circuit 1 and a sub PWM circuit 2. As shown in FIG. 1, the main PWM 1 circuit 1 compares the output voltage of the power supply circuit with a reference voltage in order to make the output voltage of the power supply circuit constant, and based on the result of the comparison, determines the output voltage of the transformer T1 of the power supply circuit. Pulse width modulation (PWM) for changing the pulse width of the voltage generated on the next side is performed.

In the main PWM 1 circuit 1, for example, a low-voltage output (usually, generated on the secondary side of the transformer T1 by controlling on / off of a switching element SW1 of a transistor provided on the primary side of the transformer T1. 24
V) is A / D (analog / digital) converted. A /
The voltage value obtained by the D conversion is used for the power supply circuit control CPU.
It is compared with a preset reference voltage value using a comparator (not shown) provided inside. Based on this comparison result, the pulse width of the voltage generated on the primary side of the transformer T1 is changed by pulse width modulation. As a result, feedback control is performed so that the low-voltage output generated on the secondary side of the transformer T1 becomes constant.

In the sub PWM circuit 2, the power supply circuit control C
The output voltage value of the power supply circuit, which has been A / D converted using the comparator inside the PU, is compared with a preset reference voltage value, and high / low (high / lo) is determined according to the comparison result.
w) The signal (ON / OFF signal) is output to the switching element SW2 of the transistor. Although this is not strictly pulse width modulation, it appears that the pulse width has been changed by the output of the on / off signal.
It is called an M circuit.

For example, when controlling so that the high-voltage output of the power supply circuit is maintained constant, a voltage divided from the high-voltage output is read from an A / D port (not shown) of the CPU for controlling the power supply circuit. The read voltage value is used for the power circuit control C
A comparator in the PU compares the voltage with a preset reference voltage value. As a result of the comparison, if the read voltage value is larger than the preset reference voltage value, a low signal (OFF signal) is output from the sub-PWM circuit 2 and the read voltage value is set to the preset reference voltage value. When the voltage is smaller than the voltage value, a high signal (ON signal) is output from the sub PWM circuit 2. In this way, a pulse signal for controlling the high voltage output to be kept constant is output from the sub PWM circuit 2. Switching element SW according to this pulse signal
2 is turned on / off to keep the high voltage output of the power supply circuit constant. The comparison logic can be set in reverse. That is, as a result of the comparison, if the read voltage value is larger than the preset reference voltage value, the sub PW
When a high signal is output from M circuit 2 and the read voltage value is smaller than a preset reference voltage value, sub-PW
The M circuit 2 outputs a low signal.

In the conventional power supply control circuit, when a reset signal (PROTECT signal) is input to the main PWM 1 circuit 1 from a protection circuit (not shown) provided on the primary side of the transformer T 1, the primary circuit of the transformer T 1 The operation of the main PWM1 circuit 1 for controlling the voltage generated on the side is stopped by hardware, and then the stop of the operation of the main PWM1 circuit 1 is detected by software, and the transformer T
Thus, the output of the voltage generated on the secondary side of No. 1 is stopped.

[0008]

However, in the conventional power supply control circuit, for example, when the output voltage of the power supply circuit is lower than a preset reference voltage, the sub-PWM circuit 2 continuously outputs the high output voltage of the power supply circuit. It was configured to supply. Therefore, after the PROTECT signal generated by the protection circuit provided on the primary side of the transformer T1 is input, the operation of the main PWM1 circuit 1 is stopped, and then the operation of the main PWM1 circuit 1 is stopped. In a short period of time before the operation is performed to stop the supply of the output voltage generated on the secondary side of the transformer T1 and detected on the secondary side of the transformer T1, the voltage is generated on the secondary side of the transformer T1 by the residual voltage of a capacitor (not shown). The output voltage is supplied from the output terminal of the power supply circuit.

In the conventional power supply control circuit, the main P
Since only one WM1 circuit 1 is provided, it is complicated to accurately and stably supply the output voltage of the power supply circuit by performing feedback control on the voltage generated on the secondary side of the transformer T1. It was necessary to construct a simple circuit.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to improve the safety in the event of an abnormality in a power supply circuit, prevent malfunction of the power supply circuit, and improve the versatility of the power supply. It is to provide a control circuit.

[0011]

According to a first aspect of the present invention, there is provided a power supply control circuit for switching a voltage generated on a primary side of a transformer by switching a voltage generated on a primary side of the transformer.
In a power supply control circuit that performs pulse width modulation control on a power supply circuit by feeding back an output voltage generated on a secondary side, a voltage generated on a primary side of a transformer is controlled, and a protection circuit provided on the primary side of the transformer is provided. Operation is stopped by the input of the reset signal generated in
And a second pulse width modulation circuit that controls the voltage generated on the secondary side of the transformer and stops operation when the reset signal is input.

Preferably, in the second aspect, the second
Can be independently stopped by the input of the reset signal generated by the protection circuit provided on the secondary side of the transformer.

Preferably, in claim 3, the operations of the first pulse width modulation circuit and the second pulse width modulation circuit can be started and stopped independently of each other,
If the operation of the first pulse width modulation circuit is stopped by inputting a reset signal generated by a protection circuit provided on the primary side of the transformer, the first pulse width modulation circuit After the operation starts, the operation of the second pulse width modulation circuit can start.

Preferably, according to claim 4, it is possible to select whether to stop the operation of the second pulse width modulation circuit by a reset signal generated by a protection circuit provided on the primary side of the transformer. It is.

Preferably, the output port is set to an initial state by a reset signal generated by a protection circuit provided on the primary side of the transformer.

Preferably, the output port is set to an initial state by a reset signal generated by a protection circuit provided on a primary side of the transformer or a state before the reset signal is input. Can be selected.

Therefore, when a reset signal is input from the protection circuit provided on the primary side of the transformer, not only the operation of the main PWM1 circuit on the primary side of the transformer is stopped in hardware, but also The operation of the main synchronous sub-PWM circuit synchronized with the main PWM1 circuit and the operation of the main PWM2 circuit for controlling the output voltage generated on the secondary side of the transformer or another power supply circuit are simultaneously stopped.

In addition to the input of the reset signal for stopping the operation of the main PWM1 circuit provided on the primary side of the transformer, only the operation of the main PWM2 circuit provided on the secondary side of the transformer is controlled. Enables input of a reset signal for stopping independently.

The operation of the main synchronous sub-PWM circuit and the main PWM2 circuit is started after the operation of the main PWM1 circuit is started or after the start permission flag of the main PWM1 circuit is enabled.

The operation of the sub-PWM1 circuit for controlling the output voltage generated on the secondary side of the transformer is stopped by the input of a reset signal generated by a protection circuit provided on the primary side of the transformer.

In addition to the reset signal generated by the protection circuit provided on the primary side of the transformer, the sub PWM
A reset signal for stopping only one circuit independently can be input.

Further, the sub-PW is generated by inputting a reset signal generated by a protection circuit provided on the primary side of the transformer.
Whether the operation of the M1 circuit is stopped or not can be selected.

Also, the reset signal generated by the protection circuit provided on the primary side of the transformer receives an input of a reset signal.
Whether the operation of the WM2 circuit is stopped or not can be selected.

When a reset signal generated by a protection circuit provided on the primary side of the transformer is input, each PW
In addition to stopping the operation of the M circuit, the output port is reset to an initial state in order to stop the load on the power supply circuit.

Further, when a reset signal generated by a protection circuit provided on the primary side of the transformer is input, it is possible to select whether to return the output port to the initial state or to maintain the state before the input of the reset signal.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a power supply control circuit according to an embodiment of the present invention will be described in detail with reference to the drawings.

(Embodiment 1) FIG. 3 is a diagram showing a configuration of a power supply circuit according to a first embodiment of the present invention, and FIG. 4 is a power supply control circuit according to the first embodiment of the present invention. FIG. 2 is a block diagram illustrating a configuration of a power supply circuit control CPU (central processing unit).

The power supply circuit control CPU according to the first embodiment of the present invention shown in FIG. 4 has a main PWM (pulse width modulation).
1 circuit 3, main PWM 2 circuit 4, main synchronous sub PW
M circuit 5, sub PWM1 circuit 6, sub PWM2 circuit 7,
It is composed of OR circuits 8 and 9 and a flip-flop 10.

The PROTECT signal is a reset signal generated by a protection circuit (not shown) provided on the primary side of the transformer T2. The PROTECT signal is directly input to the main PWM1 circuit 3 and the main synchronous sub-PWM circuit 5, and is output from the main PWM2 circuit. OR circuit 8 for circuit 4 and sub-PWM2 circuit 7
Or 9 respectively. The RST signal is a reset signal generated by a protection circuit provided on the secondary side of the transformer T2 or a protection circuit of another power supply circuit.
Is input to Further, the SUBRST signal is a reset signal generated by a protection circuit that is different from the protection circuit that generates the RST signal in the protection circuit provided on the secondary side of the transformer T2.
Input to the circuit 7.

Next, the operation of the power supply circuit control CPU, which is the power supply control circuit according to the first embodiment of the present invention, will be described.

When an abnormality such as an overcurrent occurs on the primary side of the transformer T2, a protection circuit provided on the primary side of the transformer T2 operates to generate a PROTECT signal. The PROTECT signal generated by the protection circuit is input to the power supply circuit control CPU. This PROTE
The power supply circuit control CPU is controlled by the main PWM in accordance with the CT signal.
The operation of one circuit 3 is stopped. Thereby, the transformer T
Since the generation of the voltage stops on the primary side of the transformer T2, no voltage is output on the secondary side of the transformer T2. At this time, the fluorescent lamp 20 provided on the secondary side of the transformer T2 is used.
, The main synchronous sub-PWM circuit 5 that controls the voltage applied to the sub-clock is reset at the same time, and the operation is stopped.

Further, the main PWM2 circuit 4 and the sub PWM2 circuit for controlling the output of the voltage on the secondary side of the transformer T2 are provided.
The circuit 7 and the like are configured such that when a protection operation is performed by a protection circuit provided correspondingly, the operation can be independently stopped. That is, the input of the RST signal resets the main PWM2 circuit 4, and the input of the SUBRST signal causes the sub PWM
The M2 circuit 7 is reset.

Further, if the main PWM2 circuit 4, the main synchronous sub-PWM circuit 5, and the sub-PWM2 circuit 7 are reset by the PROTECT signal which is a reset signal and the operation is stopped and then the PROTECT signal is released, the main PWM2 circuit 4. Main synchronization sub PW
The main PWM2 circuit 4, the main synchronous sub-PWM circuit 5, and the sub-PWM2 are provided after a predetermined delay time has elapsed after the operation of the main PWM1 circuit 3 is started with the M circuit 5 and the sub-PWM2 circuit 7 having a delay in advance. The circuits 7 are each configured to start operation.

With such a configuration, when the protection operation is performed by each protection circuit provided on the secondary side of the transformer T2 during the operation of the power supply circuit, the main PWM2 circuit 4 and the main synchronous sub-PWM circuit 5 , And sub-PWM2
The operations of the circuits 7 are individually stopped, and the transformer T2
An abnormality occurs on the primary side of the main PWM1 circuit 3
When the operation is stopped, the main PWM2 circuit 4, the main synchronous sub-PWM circuit 5, and the sub-PWM2 circuit for output voltage control are provided on the secondary side of the transformer T2 which is no longer synchronized with the main PWM1 circuit 3. 7 can be stopped immediately. Further, after the main PWM1 circuit 3 starts operating or after the start permission flag of the main PWM1 circuit 3 is enabled, the main PWM1 circuit 3 is activated.
2 circuits 4, main synchronous sub-PWM circuit 5, and sub-P
Since the WM2 circuit 7 is configured to operate, synchronization with the main PWM1 circuit 3 cannot be achieved, and the main PWM2 circuit 4, the main synchronous sub-PWM circuit 5, and the sub-PWM2 circuit 7 are in an uncontrolled state. Can be prevented. Therefore, each PWM at the time of occurrence of an abnormality in the power supply circuit
PW when circuit operation stops and power supply circuit returns
Malfunction of the M circuit can be prevented.

(Embodiment 2) FIG. 5 is a diagram showing a configuration of a power supply circuit control CPU which is a power supply control circuit according to a second embodiment of the present invention. The basic operation of the power supply circuit control CPU according to the second embodiment of the present invention is substantially the same as that of the power supply circuit control CPU according to the first embodiment of the present invention. The power supply circuit control CPU according to the embodiment is configured to be able to input a reset signal for resetting the sub-PWM 1 circuit 6. That is, the OR circuit 11 connected to the sub-PWM1 circuit 6 is further provided in the power supply circuit control CPU according to the first embodiment of the present invention,
A PROTECT signal which is a reset signal generated by a protection circuit provided on the primary side of the transformer T2, or SUBRST1 which is a reset signal of the sub-PWM1 circuit 6.
The sub-PWM 1 circuit 6 is configured to be reset when one of the signals is input.

In a conventional power supply circuit control CPU, the PR generated by a protection circuit provided on the primary side of the transformer is used.
The configuration is such that the sub PWM circuit 2 is stopped by determining by software that the operation of the main PWM 1 circuit 1 has been stopped by the input of the OTECT signal to the main PWM 1 circuit 1. Therefore, during a short period from when the main PWM1 circuit 1 is stopped to when the output of each voltage generated on the secondary side of the transformer by software is stopped by the port operation, each of the circuits provided on the secondary side of the transformer is provided. The output voltage was slightly supplied by the residual voltage of the capacitor of the voltage output circuit.

However, the power supply circuit control CPU according to the second embodiment of the present invention can stop the operation of the main PWM 1 circuit 3 and also stop the operation of the sub PWM 1 circuit 6 simultaneously. Sometimes, the output of the voltage on the secondary side of the transformer T2 can be immediately stopped. Further, since the SUBRST1 signal, which is a reset signal for resetting the sub-PWM1 circuit 6, can be input, the operation of the sub-PWM1 circuit 6 can be performed when the protection circuit provided on the secondary side of the transformer operates. Since the power supply circuit is stopped and the output of the voltage in the power supply circuit is immediately stopped, safety when an abnormality occurs in the power supply circuit can be improved.

(Embodiment 3) FIG. 6 is a diagram showing a configuration of a power supply circuit control CPU which is a power supply control circuit according to a third embodiment of the present invention. In the power supply circuit control CPU according to the third embodiment of the present invention, the AND circuit 12 is further provided in the power supply circuit control CPU according to the second embodiment of the present invention. As a result, a reset signal PROTE generated by a protection circuit provided on the primary side of the transformer T2 is generated.
When the CT signal is input to the sub PWM 1 circuit 6, the sub P
Whether or not the WM1 circuit 6 is reset can be selected by the selection signal A.

Accordingly, due to the configuration of the power supply circuit, the P generated by the protection circuit provided on the primary side of the transformer T2 is generated.
When the sub-PWM1 circuit 6 is used to control a circuit or the like that needs to continue operating even when the ROTECT signal is input, the sub-PWM1 circuit 6 is generated by a protection circuit provided on the primary side of the transformer T2 by the selection signal A. Since the PROTECT signal can be invalidated, the versatility of the power supply circuit control CPU serving as the power supply control circuit can be improved.

(Embodiment 4) FIG. 7 is a diagram showing a configuration of a power supply circuit control CPU according to a fourth embodiment of the present invention. Power supply circuit control CPU according to a fourth embodiment of the present invention
The power supply circuit control CP according to the third embodiment of the present invention will now be described.
U, an AND circuit 13 is further provided, and the transformer T2
Generated by the protection circuit provided on the primary side of the
Whether or not the main PWM2 circuit 4 is reset by the TECT signal can be selected by the selection signal B.

With such a configuration, when a power supply circuit different from the power supply circuit driven and controlled by the main PWM 1 circuit 3 is driven and controlled by the main PWM 2 circuit 4, the power supply circuit driven and controlled by the main PWM 1 circuit 3 When the operation of another power supply circuit is not stopped even if the operation of
Generated by the protection circuit provided on the primary side
Since the OTECT signal can be invalidated, the versatility of the power supply circuit control CPU serving as the power supply control circuit can be further improved.

(Embodiment 5) FIG. 8 is a diagram showing a part of a configuration of a power supply circuit control CPU which is a power supply control circuit according to a fifth embodiment of the present invention. In the power supply circuit control CPU according to the fifth embodiment of the present invention, the output port is reset by the PROTECT signal generated by the protection circuit provided on the primary side of the transformer T2 so as to be in the initial state. ing. Here, for example, P
The gate circuit 14 is controlled by the ROTECT signal. With such a configuration, the P generated by the protection circuit provided on the primary side of the transformer T2 is generated.
The output port is set to the initial state by the ROTECT signal, and each load controlled by the output port is turned off, so that a malfunction or the like at the time of restarting the power supply circuit can be prevented.

(Embodiment 6) FIG. 9 is a diagram showing a part of the configuration of a power supply circuit control CPU which is a power supply control circuit according to a sixth embodiment of the present invention. In the power supply circuit controlling CPU according to the sixth embodiment of the present invention, the AND circuit 15 is further provided in the power supply circuit controlling CPU according to the fifth embodiment of the present invention. Whether the output port is reset or not can be selected by a selection signal C according to a PROTECT signal generated by a protection circuit provided on the side.

With such a configuration, one of the transformers T2
PROTE generated by the protection circuit provided on the next side
An output port for controlling a circuit that needs to hold the state before resetting even after the output of the voltage generated on the secondary side of the transformer T2 is stopped by the operation of the main PWM1 circuit 3 being stopped by the input of the CT signal. Can make the PROTECT signal generated by the protection circuit provided on the primary side of the transformer T2 invalid by the selection signal C, so that the versatility as a power supply circuit control CPU as a power supply control circuit is further improved. Can be improved.

[0045]

As described above, according to the present invention, the safety of the power supply circuit in the event of an abnormality is improved, the malfunction of the power supply circuit is prevented, and the versatility of the power supply circuit control CPU as the power supply control circuit is improved. Can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a conventional power supply circuit.

FIG. 2 shows a power supply circuit control CP which is a conventional power supply control circuit.
FIG. 3 is a block diagram showing a configuration of U.

FIG. 3 is a diagram illustrating a configuration of a power supply circuit according to the first embodiment of the present invention.

FIG. 4 is a diagram illustrating a configuration of a power supply circuit control CPU that is a power supply control circuit according to the first embodiment of the present invention.

FIG. 5 is a diagram illustrating a configuration of a power supply circuit control CPU that is a power supply control circuit according to a second embodiment of this invention.

FIG. 6 is a diagram illustrating a configuration of a power supply circuit control CPU that is a power supply control circuit according to a third embodiment of the present invention.

FIG. 7 is a diagram illustrating a configuration of a power supply circuit control CPU that is a power supply control circuit according to a fourth embodiment of the present invention.

FIG. 8 is a diagram illustrating a part of a configuration of a power supply circuit control CPU that is a power supply control circuit according to a fifth embodiment of the present invention.

FIG. 9 is a diagram illustrating a part of a configuration of a power supply circuit control CPU that is a power supply control circuit according to a sixth embodiment of the present invention.

[Explanation of symbols]

 1, 3 Main PWM (pulse width modulation) 1 circuit 2 Sub PWM circuit 4 Main PWM 2 circuit 5 Main synchronous sub PWM circuit 6 Sub PWM 1 circuit 7 Sub PWM 2 circuit 8, 9, 11 OR circuit 10 Flip flop 12, 13, 15 AND Circuit 14 Gate circuit 20 Fluorescent lamp T1, T2 Transformer SW1, SW2 Switching element

Claims (6)

[Claims] A power supply control circuit for switching a voltage generated on a primary side of a transformer and feeding back an output voltage generated on a secondary side of the transformer to perform pulse width modulation control of a power supply circuit. A first pulse width modulation circuit that controls a voltage generated on the primary side and stops operation when a reset signal generated by a protection circuit provided on the primary side of the transformer is input; A second pulse width modulation circuit that controls a voltage generated on the side of the power supply and stops operation when the reset signal is input. 2. The operation of the second pulse width modulation circuit can be independently stopped by the input of a reset signal generated by a protection circuit provided on a secondary side of a transformer. The power supply control circuit according to claim 1. 3. The first pulse width modulation circuit and a second pulse width modulation circuit.
Of the pulse width modulation circuit can be started and stopped independently of each other, and the first pulse width modulation circuit can be started by receiving a reset signal generated by a protection circuit provided on the primary side of the transformer. 2. The power supply according to claim 1, wherein when the operation of the second pulse width modulation circuit is stopped, the operation of the second pulse width modulation circuit can be started after the operation of the first pulse width modulation circuit is started. Control circuit. 4. A method according to claim 1, wherein an operation of said second pulse width modulation circuit is stopped or not by an input of a reset signal generated by a protection circuit provided on a primary side of said transformer. The power supply control circuit according to claim 1. 5. The power supply control circuit according to claim 1, wherein an output port is set to an initial state by a reset signal generated by a protection circuit provided on a primary side of the transformer. 6. A reset signal generated by a protection circuit provided on a primary side of a transformer can select whether to set an output port to an initial state or to maintain a state before a reset signal is input. The power supply control circuit according to claim 1, wherein: