JPS62286757A - Power source circuit of dot matrix printer - Google Patents

Abstract

PURPOSE:To minimize the heat planning of a power source circuit, by performing the control of load while monitoring a primary side current increasing with heavy load by a current detection circuit. CONSTITUTION:When a primary side current I1 increases, the voltage between both terminals of the current detection resistor R1 of a current detection circuit 1 also becomes high and, when the value of said voltage reaches a certain value, a transistor Q1 is turned ON and a transistor Q2 is also turned ON. The collector current I0 of the transistor Q2 charges the resistor R2 and capacitor C1 of an integrating circuit for monitoring a time. The voltage between both terminals of said capacitor C1 appears in a secondary side resistor R3 through a photocoupler 2. MPU3 monitors the voltage between both terminals of the resistor R3 through an analogue port AP to make it possible to know the state of the primary side current I1 and control secondary side load 4 on the basis of the voltage level thereof.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a power supply circuit for a dot matrix printer, particularly to thermal design.

[Conventional technology]

In dot matrix printers, the output load of the power supply has a considerable difference in printed dot density, so even if the conventional power supply is in continuous operation at maximum load, the rated power is still low. [Problems to be solved by the invention] Regarding the output capacity that can be supplied and heat dissipation [problems to be solved by the invention] As mentioned above, the conventional power supply fully demonstrates its ability when printing high dot density such as graphics, but when printing alphanumeric characters etc. For normal printing, a capacity of 175 to 8 will suffice. As a general usage method, it is rare to print only graphics etc. continuously, and there is a runner-up that results in redundant design.

[Interactive means to solve problems]

The power supply circuit of the present invention outputs a temporary heavy load or maximum load, but when continuous heavy load or maximum load is required, the power supply circuit monitors the primary side current value and time of the power supply circuit and outputs the load side. The purpose is to control the heat generation associated with the increase in current and to minimize the thermal design of the power supply circuit.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 shows one embodiment of the present invention and is a simplified circuit of a dropper power supply. In this embodiment, as the negative side current generator 1 increases, the current detection resistance ratio of the current detection circuit 1! The voltage across the transistor also increases, and when this voltage reaches a certain value, the transistor Q1 turns on, and accordingly, the transistor Q2 also turns on. The collector current o of the transistor Q2 is charged by the resistance ratio 2 of the time monitoring integrating circuit and the capacitor Ct k of the capacitor C1.
The voltage across the photocoupler 2 is the resistance ratio of the secondary side, which is 3.
By monitoring the voltage across this resistance ratio 3 of the MPU 3fl, which appears on the analog board AP, the primary side electric current is used! The MPU 3 controls the secondary side load 4 based on this voltage level. By appropriately selecting the ratings of each part, - next-side electrical work! control 1
? l! ! The heat generation of the circuit can be controlled.

〔Effect of the invention〕

As explained above, the present invention has the effect of minimizing the thermal design of the source circuit by monitoring the primary side RL current, which increases with heavy loads, in the current detection circuit and performing load control. be.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram of an embodiment of the present invention. R1...Current detection resistor R1-Q+eQz°゛transistor, R3...Resistor, C1...Capacitor, 1...Current detection circuit, 2...Photocoupler, 3.
...MPU, 4...Secondary side load.

Claims (1)

[Claims] A power supply circuit for a dot matrix printer, characterized in that a limit is imposed on a secondary side load in response to a primary side current of the circuit.