Panasonic KX-NS700, KX-NS720, KX-NS720XE, KX-NS720AL, KX-NS720UK Service Manual

© Panasonic System Networks Co., Ltd. 2014
Unauthorized copying and distribution is a violation
of law.

ORDER NO. KMS1411488SE

Hybrid IP-PBX

Model No. KX-NS700

KX-NS720 Series

Power Supply Unit Addition

TABLE OF CONTENTS

PAGE PAGE

1 Technical Descriptions----------------------------------------- 2

1.1. Power Supply Unit----------------------------------------- 2

1.1.1. Block Diagram and Circuit Description of
PSU ------------------------------------------------------ 2

1.2. AC input, Rectification Smoothing Circuit ----------- 2

1.3. Main Converter--------------------------------------------- 3

1.4. DC Switch and DC Output Circuit--------------------- 4

1.5. AC Alarm Circuit and DC Alarm Circuit-------------- 5

2 Troubleshooting Guide----------------------------------------- 6

2.1. Power Supply Unit----------------------------------------- 6

2.1.1. No Voltage is Output at All (1)--------------------- 6

2.1.2. No Voltage is Output at All (2)--------------------- 7

2.1.3. 41V are Not Output----------------------------------- 8

3 Schematic Diagram ----------------------------------------------9

3.1. Power Supply Board ------------------------------------ 14

3.2. Waveform----------------------------------------------------9

4 Printed Circuit Board------------------------------------------15

4.1. Power Supply Board ------------------------------------ 15

4.1.1. Component View ------------------------------------ 15

4.1.2. Bottom View------------------------------------------ 16

5 Exploded View and Replacement Parts List----------- 17

5.1. Power Supply Unit--------------------------------------- 17

5.2. Replacement Parts List--------------------------------- 18

5.2.1. Power Supply Board-------------------------------- 18

Please file and use this supplement manual together with the service manual.

2

1 Technical Descriptions

1.1. Power Supply Unit

Added into the Original Service Manual as section 4.5.

This unit is switching regulator power supply and supplies DC voltages to CPU Board (MPR), and optional card (free slot).
PSU (power supply unit) has two outputs (41V, 15V). 15V output is supplied only in CPU Board (MPR) and option ca rd.
Other outputs are mainly used as an object for the electric supply to a terminal.

1.1.1. Block Diagram and Circuit Description of PSU

Added into the Original Service Manual as section 4.5.1.

1.2. AC input, Rectification Smoothing Circuit

Added into the Original Service Manual as section 4.6.

1) Filter Circuit

This circuit consists of the following components and removes the exogenous noise or the noise generated at power supply.
CX1, CX2: normal mode filter (X-Capacitor)
LF1, LF2: common mode noise filter
CY1, CY2: common mode noise filter (Y-Capacitor)

ADDITIONS

3

2) Rectification Smoothing Circuit

This circuit consists mainly of the following components and performs AC-DC conversion.
D2: Diode Bridge
C4: Primary Smoothing Capacitor

3) Surge Absorber Circuit

As the main component of this circuit, VR1 protects the system against exogenous noise such as lightning surge.
VR1: Varistor

4) Inrush Current Avoiding Circuit

Immediately after AC input applies voltage, the following components control inrush current to the Smoothing Capacitor.
RT1: thermistor

5) AC Detection Circuit

This circuit consists of the following components and detects AC input voltage.
Main components: D9, D10, D24, Q8, Q12, Q13, U1, Z7
AC voltage commutates through D9, D10.
When AC voltage is over the threshold, Q8, Q12, and Q13 are switched ON to all ow AC Detection Circuit to transfer AC input
status to the secondary side AC alarm signal delivery section through U1.

1.3. Main Converter

Added into the Original Service Manual as section 4.7.

This section describes the main converter circuit which insulates the primary DC voltage and converts the voltage to a Secondary
voltage “ Vout” (41V).

1) Main Converter Section (Primary)

This main converter consists of the following components.
Q6: main switch FET
T1: isolation transformer
U2: Controls Q6
U4: device for transfer control secondary side
Other peripheral circuit

Secondary side output condition is transferred by U4 to the primary side.
Q6 is switched to ON/OFF in U2 to control the secondary side voltage.

2) Main converter section (Secondary)

T1: The output of this isolation transformer is 41V, and is the power supply for output voltage in section 3.
RT2: If the heatsink of Q6 become too hot.

Vout:

This output consists of the Rectification Smoothing Circuit of D6, C10, C11, C36.
This is the source of 15V output and 41V output of PSU.
The thermistor RT2 decreases the resistance value.

4

3) Latch function for protection

Control IC U2 has the latch fonction to stop the PSU operation when over heat or over voltage is detected .
To release the latch status, release the abnormal state at first, then remove the AC cord from PSU and leave for 60 seconds
before restart.

1.4. DC Switch and DC Output Circuit

Added into the Original Service Manual as section 4.8.

This section describes the operation of the 41V output circuit and 15V output circuit which consists of DC/DC converter.

1) DC Switch

Vout(41V), the output of Main Converter is supplied to post circuits via CN100 and DC Switch mounted on the cabinet.

2) 41V Output
2-1) 41V Overcurrent Protection Circuit

This circuit consists of mainly of Q19, R62, R105 and Q15
When Overcurrent flows to R62, the voltage potential defference between R62 and R105 is detected by Q19 and Q19 turns
ON.
Then Q15(FET Switch) turns OFF.
Consequently the fold back current limiting shuts down 41V output.
To control this circuit, +60V voltage which is generated in 15V Circuit.

2-2) 41V Output Converter Circuit

41V is devided to two outputs, "+41V" and "+41V_OP")
"+41V" is fed to the circuit on Base Board / CPU Boaerd.
"+41V_OP" is fed to the optional card via Base Board.

3) 15V Output
3-1) 15V Output Converter Circuit

This circuit generates +15V from +41V.
This circuit consists of mainly of F4, C12, U7, D14, L3, C26

3-2) 15V Output Overcurrent Detection Circuit

This circuit consists of mainly of R63, Q30, and Q31.
If overcurrent of 15V output is detected, Q30, Q31, and Q29 get ON, then SD(Shut Down) pin of U7 get high and U7 shut
downs.

3-3) 15V Output Overvoltage Detection Circuit

This circuit consists of mainly of Z12, Q28 and Q27.
If overvoltage of 15V output is detected, Q28, Q27, and Q29 get ON, then SD(Shut Down) pin of U7 ge t high and U7 shut
downs.

4) Overvoltage Detection Circuit-2

When 15V or 41V output becomes abnormally high, it makes Photo Coupler U3 ON via D13.
Then the control IC(U2) stops with the latch mode.

5

1.5. AC Alarm Circuit and DC Alarm Circuit

Added into the Original Service Manual as section 4.9.

This section describes the operation of the circuit that sends the AC alarm/DC alarm signal.

1) AC alarm circuit

When the AC Detection Circuit (described in section 1.2. (5)) detects AC input as "Yes", the Secondary side transistor of U1
turns ON. This action turns Q23 ON and then a LOW signal is sent to AC alarm output.
However, if the AC input is detected as "No", the Secondary side transistor of U1 turns OFF. This action turns Q23 OFF and
then AC alarm sending output becomes OPEN. (Open collector output)
Q18 functions as same as Q23 and the output of Q23 is used for DC ALM control.

2) DC Alarm Signal Sending Circuit

When 41V is output normally, shunt regurator U8 in the output voltage detection circuit turns ON and Q26 turns OFF. Q21 also
turns on and then DC alarm sending output becomes LOW.
When 41V output becomes abnormal, shunt regurator U8 turns OFF and Q26 turns ON, Q21 also tu rns OFF and DC alarm
sending output becomes OPEN. (Open collector output)
Q17 and Q25 function for the hysterysis of DC ALM detect/undetect volt age.

If AC alarm is detected, Q24 turns ON and Q21 tourns OFF (DCALM Low  Open) with some delay.

6

2 Troubleshooting Guide

2.1. Power Supply Unit

Added into the Original Service Manual as section 9.2.

2.1.1. No Voltage is Output at All (1)

Added into the Original Service Manual as section 9.2.1.

Main converter output voltage error [Between pin1 and pin2 of CN100, DC Switch OFF]