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STR-W6700 の電気的特性と機能

STR-W6700のメーカーはSankenです、この部品の機能は「(STR-W6700 Series) Quasi-Resonant Switching Regulators」です。


製品の詳細 ( Datasheet PDF )

部品番号 STR-W6700
部品説明 (STR-W6700 Series) Quasi-Resonant Switching Regulators
メーカ Sanken
ロゴ Sanken ロゴ 




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STR-W6700 Datasheet, STR-W6700 PDF,ピン配置, 機能
Product Information
STR-W6700 Series Off-Line
Quasi-Resonant Switching Regulators
Introduction
The Series STR-W6750 devices are hybrid integrated cir-
cuits (HICs) with a built-in power MOSFET and a control
IC designed for quasi-resonant type switch-mode power
supplies (SMPS). In normal operation, the HIC provides
high efficiency and low EMI noise with bottom-skip quasi-
resonant operation during light output loads. Low power
consumption is also achieved by blocking (intermittent)
oscillation during an auto-burst mode and reduced even
further in a manually triggered (clamping an output voltage)
standby mode.
The HIC is supplied in a seven-pin fully-molded TO-220-
style package with pin 2 deleted, which is suitable for down-
sizingand standardizing of an SMPS by reducing external
componentcount and simplifying circuit design.
Features and benefits include the following:
Blocking (or intermittent) oscillation operation by
reducing output voltage in the standby mode.
In addition to the standard quasi-resonant operation, a
bottom-skip function is available for increased efficiency
from light to medium load.
Soft-start operation at start-up.
Reduced switching noise (compared to conventional
PWM hard-switching solution) with a step-drive
function.
Built-in avalanche-energy-guaranteed power MOSFET
(to simplify surge-absorption circuit; no VDSS derating
is required).
Overcurrent protection (OCP), overvoltage protection
(OVP), overload protection (OLP), and maximum
ON-time control circuits are incorporated. OVP and OLP
go into a latched mode.
Able to save SMPS design time with present designs and
evaluation processes.
Figure 1. STR-W6700 series packages are fully molded TO-220
package types. Pin 2 is deleted for greater isolation.
Table 1. Product Line-up
Type #
STR-W6735
MOSFET
VDSS
(V)
500
RDS(on)
(Max)
(Ω)
0.57
VAC
Input
(V)
120
POUT*
(W)
160
STR-W6753
Wide
1.70
230
58
120
STR-W6754
650
Wide
0.96
230
100
160
STR-W6756
Wide
0.73
230
140
240
STR-W6765
800
Wide
1.80
230
50
110
*The listed output power represents thermal ratings, and the peak
output power, POUT , is obtained by 120% to 140% of the thermal
rating value. In case of low output voltage and narrow on-duty
cycle, the POUT (W) becomes lower than the above.
Contents
Introduction
Pin functional descriptions
Operation description
Transformer parameters
General considerations
Design considerations
Package Dimensions, TO-220
Worldwide Contacts
28103.30
1
2
6
10 All performance characteristics given are typical values for
11 circuit or system baseline design only and are at the nominal
13 operating voltage and an ambient temperature of 25°C, un-
14 less otherwise stated.
17
SANKEN ELECTRIC CO., LTD.
http://www.sanken-ele.co.jp/en/
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STR-W6700 pdf, ピン配列
In an actual power supply circuit, the VCC pin voltage might
be changed by the value of secondary output current as shown
in figure 5. C3 is fully charged by the surge voltage generated
instantly after the MOSFET turns off. In order to prevent this, it
is effective to add a resistor (R7) of several ohms to tens of ohms
in series with the diode as shown in figure 5. The optimum value
of the additional resistor is determined in accordance with the
specifications of the transformer because the VCC pin voltage is
determined by construction of the transformer.
Furthermore, the variation ratio of the VCC pin voltage becomes
worse due to a loose coupling between primary and secondary
windings of the transformer (the coupling between the bias wind-
ing and the stabilized output winding for the constant voltage
control). Therefore, when designing a transformer, the winding
position of the bias winding needs to be studied carefully.
Overvoltage protection (OVP) circuit If VCC, referencing
the S/GND pin, exceeds 27.7 V, the OVP circuit of the control
IC starts its operation and the fault mode is latched by the latch
circuit, the control IC stopping its oscillation. Generally, the VCC
pin voltage is supplied from the bias winding of the transformer,
VCC
Without R7
and the voltage is in proportion to the output voltage; thus, the
OVP circuit also operates in the case of overvoltage output of the
secondary side, for example, when the voltage detection circuit
is open. The secondary output voltage for the OVP operation
(VO(OVP)) is obtained from the following formula:
VO(OVP)
=
VO(normal operation)
VCC(normal operation)
27.7 V
(1)
Latch circuit OVP and OLP fault modes latch the oscillation
output low, which stops the power supply circuit operation. The
holding current of the latch circuit is 140 μA (max., TA = 25°C)
when the VCC pin voltage is at the Operation-Stop voltage minus
0.3 V.
In order to prevent malfunction caused by, for instance, noise,
a delay time is programmed into a timer circuit, which prevents
latch circuit operation until the OVP or OLP circuit keeps operat-
ing for more than a programmed time. During the latched mode,
the internal regulator circuit keeps running, the circuit current is
maintained at a high level, and the VCC pin voltage drops.
When the VCC pin voltage drops down to the Operation-Stop
voltage (9.7 V (typ.) ), the voltage starts rising again as the circuit
current becomes less than 140 μA. When the VCC pin voltage
reaches the Operation-Start voltage (18.2 V (typ.) ), the circuit
current increases, and the voltage drops again. Consequently,
the VCC pin voltage is maintained between 9.7 V and 18.2 V in
the latched mode. Figure 7 shows the voltage waveform in the
latched mode. The latched mode is released by decreasing the
VCC pin voltage to below 7.2 V, or in general, by shutting off the
AC input.
With R7
SS/OLP (Pin 5)
Through the SS/OLP pin, soft-start and overload protection is
enabled by connecting a 0.47 to 3.3 μF capacitor to the pin.
IO
Figure 5. VCC versus IO (secondary load)
VCC 4
STR-W6700
S/GND 3
D2
C3
R7
D
Figure 6. VCC versus IO (secondary load)
Figure 7. VCC during latch mode
STRY6700-AN Rev. 2.0
SANKEN ELECTRIC CO., LTD.
3
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STR-W6700 電子部品, 半導体
circuit. The timing chart is shown in figure 13, and the internal
circuit diagram of the constant voltage control circuit is shown in
figure 14.
The constant-voltage-control circuit feeds a control signal (FB
current) from an error amplifier into pin 6 by way of the isolating
photocoupler. The input FB current is transformed into feedback
voltage VFB by the internal resistor (SW1 is turned on during
normal status). The voltage waveform (VOCPM) from the drain
current waveform is input to the inverting input terminal of the
FB comparator.
Figure 13 shows the FB current is decreased to nearly zero in an
overload, when the drain current is restricted to below the current
value set by the overcurrent protection circuit. In the period from
normal load to light load in figure 13, the drain current decreases
because the FB current increases and VFB rises. When VFB
exceeds the FB pin threshold voltage (VFB(OFF), 1.45 V) at light
load, the oscillation stops so as not to raise the secondary-side
output voltage.
OCP/BD (Pin 7)
The OCP/BD pin functions in overcurrent detection, bottom-skip,
and quasi-resonant-operation control. Bottom-skip and quasi-res-
onant features are described in the Operation Description section.
Negative-detection type OCP circuit The OCP circuit of
the STR-W6700 series is a pulse-by-pulse type, which detects
the peak value of the MOSFET drain current for each pulse and
inverts the oscillator output. As shown in figure 15, the overcur-
rent sense resistor, ROCP, is connected externally along with R4
and C5. R4 and C5 are to prevent malfunction caused by surges
when the MOSFET switches on. When the MOSFET switches
on, switching current occurs, and a voltage is developed across
ROCP . After that, the MOSFET turns off when the OCP/BD pin
voltage reaches VOCPBD(LIM).
The threshold voltage of the OCP/BD pin, VOCPBD(LIM), is
–0.94 V. The OCP circuit adopts negative-detection, which cre-
ates the detecting voltage, VOCPM, in the control part by dividing
the voltage (V1 + VROCP) with RB1, RB2, and R4. Because RB1
and RB2 are resistors incorporated in the IC, taking the variance
of RB1 and RB2 (defined as IOCPBD in the specifications) into
consideration, the value of R4 should be small, between 100 Ω
and 330 Ω. Select capacitor C5 (100 to 680 pF target value) for
good thermal behavior type. A high capacitance value results in
slow response time, ending up with an increase in peak drain cur-
rent during a transient and at start-up.
Operation description
Quasi-resonant operation Quasi-resonant operation matches
the timing of the MOSFET turn on to the bottom point of the
voltage resonant waveform, namely, ½ cycle of the resonant
frequency after the transformer discharges energy.
As shown in figure 16, the voltage resonant capacitor, C4, is
connected between the drain and source, and the delay circuit,
C10, D3, D4, and R9 are connected between the bias winding and
IDS
1
D
4 V CC
STA RT 18V
BUR ST 11 V
BURST
OSC
FB
FB
6
SW 1
VFB
3 S/GND
OCP
RO CP
VO CPM
7 OCP/BD
D
Control
D1
P
LOGIC DRIVE
Reg.V1
RB1
OCP
RB2
3
S/GND
VOCPM
7
OCP/BD
Filter
C5
V4
R4
V5
Figure 14. REG circuit functional block diagram
Figure 15. OCP functional block diagram
STRY6700-AN Rev. 2.0
SANKEN ELECTRIC CO., LTD.
6
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部品番号部品説明メーカ
STR-W6700

(STR-W6700 Series) Quasi-Resonant Switching Regulators

Sanken
Sanken
STR-W6700

Application Note

Sanken
Sanken


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