HA17524P Просмотр технического описания (PDF) - Hitachi -> Renesas Electronics

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HA17524P

Switching Regulator Controller

Hitachi -> Renesas Electronics 

HA17524P/FP

Functional Description

Principals of HA17524 Operation

The HA17524 switching regulator circuit, using pulse width modulation (PWM), is constructed as shown

in figure 1.

Timing resistances RT and timing capacitance CT control the oscillation frequency. CT is charged by a

constant current generated by RT. Ramp signals (saw-tooth waves) at the CT terminal generated by this

oscillator is available for reference input signal to comparator which control the pulse width.

VREF

VCC 15

RT 6

CT 7

(Ramp)

Ref.

Volt.

+5 V

Osc.

+5V

16

+5 V to internal circuitry

OSC Out

+5V

Q

3

Flip Flop

NOR

Q

+5V

—

Comparator

NOR

+

+5V

INV. Input 1

NON-INV. Input 2

GND 8

— Error Amp.

+

1kΩ

10

9 COMP

+

C.L.

—

4 CL(+)

5 CL(—)

Current Limiter

SHUT 10kΩ

DOWN

12 C1

Q1

11 E1

13 C2

Q2

14 E2

Figure 1 HA17524 Block Diagram

The reference voltage connects to the non-inverted or inverted input terminal of the error amplifier via

resistance divider (figure 2).

The output voltage from the error amplifier is compared with the ramp signal capacitance CT (figure 1).

The comparator can provide a signal with modulated pulse width.

This signal, then, controls output transistors Q1 and Q2, making an open loop to stabilize output voltage.

Outputs form the error amplifier the current limiter, and the shut-down circuit are connected together at the

comparator, so that an input signal from any one of these circuits can break the output stage.

2

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