Preface

With the rapid spread of humanoid robots and smart robot dogs, Unitree — a world-leading civil quadruped / humanoid robot maker — ships its G1 and H1 humanoid robots and Go2 and B2 robot dogs with high-power lithium batteries, and the performance of the supporting power supply directly determines the equipment's endurance and safety. The FY33609000 charger disassembled here is the standard 302.4W lithium-battery adapter for Unitree equipment, manufactured by Klinsun Power. Below we analyze the design of this high-power power supply from appearance and dimensions, internal circuitry and component materials.

I. Appearance and overall hardware parameters

Overall appearance  /  Product nameplate  /  Charger hand-held size reference

1. Housing structure

The unit is a black rectangular block made of flame-retardant PC plastic; the shell is covered with vertical grooves to improve heat dissipation. A status-indicator hole is reserved on top, anti-slip support feet are set at the four bottom corners, and the shell is filled with thermally conductive white glue, combining structural reinforcement with heat conduction.

2. Interface configuration

• Input side: a national-standard IEC C14 detachable interface, supporting replacement with power cords of various country specifications, with grounding protection, adapting to global 100-240V mains;

• Output side: an integrated magnetically shielded cable, with a multi-layer anti-bending sheath at the outlet, a built-in anti-interference magnetic ring at the middle of the cable, and a custom multi-pin dedicated connector at the end — no universal replacement part.

3. Measured dimensions and weight

• Body: length 205mm, width 107.85mm, thickness 54.13mm;

• Total output cable length about 142cm;

• Net weight 1179g.

4. Core nameplate parameters

Model FY33609000, designed specifically for 33.6V lithium batteries, output 33.6V 9A (peak 302.4W); 4A input at full load; when on standby / low current (≤0.9A) the indicator lights green. It holds the full set of mainstream safety and energy-efficiency certifications.

C14 input port  /  Output cable with magnetic ring  /  Custom charging terminal for Unitree

II. Internal overall structure teardown

After opening the plastic shell, the core PCBA module is seen fully covered by two aluminum-alloy heat sinks, and the power devices are all screw-mounted onto the metal heat-dissipation parts; key components such as the transformer, capacitors and inductors are all secured with thermal adhesive, which both suppresses vibration noise and aids heat dissipation.
PCBA board specifications: length 200mm, width 98.14mm, thickness 38.21mm. It uses a single-sided PCB design with no SMD components on the back; a large area around the transformer is coated with thermal adhesive to improve heat-dissipation efficiency.

Housing and heat dissipation  /  Inside the Klinsun Power charger  /  PCB back side

III. Detailed circuit component materials

The unit adopts a valley-fill passive PFC architecture with an isolated flyback topology, divided into five circuits: EMI filtering, rectification and boost, switching inversion, secondary rectification, and constant-current/constant-voltage control. The brands and specifications of the core components are as follows:

1. Input EMI filter loop

1. Huade 6.3A time-delay fuse to prevent short-circuit surges;

2. Songtian Electronic safety X2 film capacitor (0.47μF) and multiple 450V film filter capacitors;

3. Dual-stage common-mode inductor + NTC thermistor to suppress power-on inrush and grid electromagnetic interference;

4. Two blue Songtian Y capacitors to meet safety insulation requirements.

2. Rectification and PFC boost circuit

1. Good-Ark GBU15M rectifier bridge (15A/1000V) to complete AC-to-DC conversion;

2. 4 × 200V 470μF high-voltage electrolytic capacitors + 3 × Good-Ark MBRF20200CT (200V/20A) Schottky diodes form the passive valley-fill PFC to improve power utilization;

3. AUK 650V high-voltage NMOS (SJMN074R65SW) as the main switch, in a TO-247 package with heat sink.

3. Main control and control chips

1. Leadtrend LD7575PN (DIP8 package): primary-side current-mode switching power supply controller with integrated high-voltage startup circuit;

2. UTC324D quad operational amplifier: handles the charging constant-voltage and constant-current logic;

3. Two PC817 optocouplers: primary-secondary isolation and feedback voltage regulation signal;

4. Huakaiwei 95°C thermal fuse: forced power-off protection when the unit overheats.

4. Secondary output rectification and filtering

1. Two PFC-brand PFR60L200PT Schottky rectifiers (60A/200V) handle high-power rectification;

2. 4 × UNITED 1000μF 63V electrolytic capacitors for output filtering, with an independent filter inductor to smooth the current;

3. Beite 20A output fuse to eliminate short-circuit risk at the rear battery.

Rectifier bridge  /  Main control chip  /  Output Schottky rectifier

IV. Design highlights and summary

Core advantages

1. Ample heat-dissipation margin: full double-layer aluminum-alloy heat dissipation with thermal adhesive on all devices; temperature rise stays stable under high-power conditions, suitable for long continuous charging of robots;

2. Comprehensive multi-layer protection: integrates input fuse, NTC surge suppression, over-temperature control, output over-current fuse and primary-secondary isolation regulation, protecting the battery and power supply in all directions;

3. Globally compliant and universal: 100-240V wide input + multi-country safety certifications, strong adaptability for overseas export; the detachable cord design facilitates changing regional plugs;

4. Mature high-power solution: the passive valley-fill PFC architecture lowers material cost; the mature flyback circuit is highly reliable and the 302.4W output is stable, matching Unitree robots' high-current charging needs.

Shortcomings

1. The single-sided PCB has limited routing space and relatively low integration;

2. The output terminal is a dedicated custom type that is not compatible with universal DC plugs, so replacement parts cost more;

3. Compared with active solutions, passive PFC has limited room to improve power factor.

Overall assessment

This Klinsun 302.4W charger is a high-power lithium-battery power supply for industrial-grade robot equipment, with solid materials and well-designed heat dissipation and protection. Relying on a mature switching power supply topology, it achieves a stable 9A high-current output that can meet the fast-charging needs of Unitree humanoid robots and quadruped robot dogs — suitable for high-power lithium-battery equipment scenarios with high requirements for power-supply stability and long-term durability.